Emergent Nonreciprocal Dual Circularly Polarized Luminescence from an Iridescent Cellulose Nanocrystalline Film

Emergent Nonreciprocal Dual Circularly Polarized Luminescence from an Iridescent Cellulose Nanocrystalline Film | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Emergent Nonreciprocal Dual Circularly Polarized Luminescence from an Iridescent Cellulose Nanocrystalline Film Xinling Wang, Daikun Jia, Ruixin Zhu, Yuting Tian, Dandan Zhu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6164168/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Ubiquitous chirality has attracted increasing attention because of its unique scientific significance. Moreover, circularly polarized (CP) absorption and emission, which are the essential components of chiral optics, have received considerable interest from researchers. However, very few studies have been conducted on materials with nonreciprocal CP emission that emit CP light with opposite handedness from their two opposite surfaces. Here, we present a novel nonreciprocal CP emission film developed from cellulose nanocrystalline (CNC). A sustainable CNC film with twisted right-handedness opposite to its inherent left-handed nematic structure is developed by a rotation-induced dynamic self-assembly strategy; this film not only ambidextrously reflects left- and right-handed CP light but also clearly exhibits a tunable Janus chiroptical activity, i.e., anisotropic CP absorption and emission, on its opposite surfaces. Both orientation factor and reflected wavelength with maximum reflectivity of the CNC film significantly depend on the rotation rate and direction. In particular, the CNC film for the first time shows a unique feature of nonreciprocal CP luminescence (CPL) achieved through pH-regulated doping of cadmium telluride quantum dots. This rare nonreciprocal CPL phenomenon has broken through the reciprocity in CP emission and is highly desired in next-generation chiral electronics and photonics because of their immense potential. Physical sciences/Optics and photonics/Optical materials and structures/Photonic crystals Physical sciences/Materials science/Materials for optics/Photonic crystals Physical sciences/Nanoscience and technology/Nanoscale materials/Structural properties cellulose nanocrystal film right-handedness chiroptical anisotropy nonreciprocal circularly polarized luminescence structural color Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 8 1. Introduction Chirality, a property in which an object is not superimposed but is symmetrical with its mirror image, is one of the essential attributes of nature across macro to micro scales globally. [ 1 – 3 ] At the macro level, the mysterious nebula and the occasional cyclone show macroscopic helical chirality, [ 4 , 5 ] ordinary plant tendrils grow naturally by coiling through a left- or right-handed helix, [ 6 ] and the attractive conch shell displays an inherent helical structure. [ 7 ] At the micro-nano scale, double-helical DNA chains and certain small organic molecules exhibit unique chirality and corresponding properties. [ 8 – 10 ] Inspired by natural chirality, researchers have made considerable efforts to explore the mysteries of chirality in physics, [ 11 ] biology, [ 12 – 14 ] and chemistry [ 15 , 16 ] . In terms of materials, Liu and Yashima have summarized several significant achievements related to polymers with preferred-handed helical conformations induced by external chiral stimuli, [ 17 , 18 ] which provides a systematic understanding of the formation and mechanism of chiral structures in materials. With rapid advancements in chiral research, chiroptics and corresponding materials have attracted considerable interest worldwide because of their huge prospects. The potential of circularly polarized (CP) absorption and emission, two critical aspects of chiroptics, is usually evaluated based on circular dichroism (CD) and circularly polarized luminescence (CPL). CPL has highly attractive potential applications in various advanced technology fields such as photoelectronic devices, [ 19 , 20 ] spintronic devices, [ 21 – 23 ] information encryption and anti-counterfeiting, [ 24 , 25 ] optical data storage/quantum information, [ 26 , 27 ] 3D display, [ 28 , 29 ] CPL lasers, [ 30 ] smart sensors/detectors, [ 12 , 14 , 31 – 33 ] , and asymmetric synthesis [ 15 , 16 ] . Consequently, CPL-active materials with high luminescent quantum yield and excellent luminescent asymmetric g-factor (g lum ) are currently one of the most popular optical materials because of their remarkable optical sensitivity and spatial resolution. As paradigms, Ye et al. reported a CP room temperature phosphorescence-active material developed by incorporating naphthalene- and pyrene-doped polymethyl methacrylate into a cellulose nanocrystalline (CNC) film, therefore providing a chiral environment with tunable photonic bandgap (PBG) for achieving switchable CP phosphorescence with long-lasting afterglow. [ 34 ] Recently, Gong et al. presented a co-doping strategy in which chiral naphthylphosphoric acid derivatives, rhodamine B, and polyvinyl alcohol were selected as the donors, acceptor, and matrix, respectively, which enabled to precisely control the afterglow color of the CPL-active film for application in anti-counterfeiting and encryption. [ 35 ] In 2023, Yu et al. developed a printable CPL-active photonic paint for 3D display in next-generation wearable and smart electronics by using a confining helical co-assembly strategy; this strategy allowed controllable and macroscopic preparation of flexible CPL devices by printing on various substrates. [ 36 ] In the same year, Zhuang’s group achieved multilayer optical information encoding by using CPL-active materials to meet the increasing needs for anti-counterfeiting. [ 37 ] More recently, Zhuang et al. [ 38 ] and Liu et al. [ 39 ] successively reported full-color CPL ranging from blue to green to red by adopting different strategies. In the former study, a single-emitted helical-caging with the largest g lum of 0.8 was reported, while in the latter study, CPL involved dynamically adjustable supramolecular polymers. In addition to the abovementioned studies, several notable investigations on CPL have been reported. [ 40 – 47 ] However, it should be noted that the current research on CPL materials is primarily focused on tunable color, intensity, and feasible applications. Some advanced CPL achievements have also been reported, for example, Duan et al. proposed a unique multiple emission system through co-assembly of chiral annihilators and a sensitizer, thus forming upconverting and downshifting CPL. [ 48 ] Subsequently, a reversible optical-mechanical dual-responsive CPL elastomer was prepared, its CPL signal could be weaken or even disappear under visible light or after stretching. [ 49 ] A series of CPL-active copolymers with adjustable lifetime was constructed by modulating energy transfer efficiency, which facilitated the molecular regulation of CPL lifetime at the millisecond scale. [ 50 ] Zhao and coworkers constructed a novel through-space conjugated chiral foldamer, which enabled switchable dual CPL with opposite signs at different emission wavelengths and overcame the limitation of most CPL-active systems that exhibit CPL only at a single wavelength. [ 51 ] These emerging findings are promising for accelerating the development, in-depth understanding, and broad-spectrum application of CPL-active materials; nonetheless, very few studies have reported nonreciprocal CPL as a chiroptical phenomenon in which the sign of CPL inverses with the inversion of the propagation direction of excitation light. In contrast, reciprocal chiroptical properties (reciprocal CD and CPL) have been frequently studied. CNC suspensions can be obtained from abundant renewable plant resources. Above a certain critical concentration, CNC forms ordered cholesteric liquid crystals from disordered isotropic colloids. [ 52 ] This implies that an individual CNC particle spontaneously deposits downwards and shows parallel alignment to the directional vector. The particle is periodically deflected clockwise due to spatial repulsion and electrostatic interaction, resulting in a certain angle between the adjacent alignment layers and the corresponding axially chiral helix, which is retained in the solid state. Finally, the incident CP light with the same or opposite handedness is selectively reflected or transmitted when the wavelength adequately matches the periodic helical structure according to Bragg’s law. [ 36 , 53 ] Therefore, CNC is considered an ideal environmentally friendly alternative photonic crystal for sustainably developing iridescent chiral nematic functional materials with CP light response. The structural color and CPL property of CNC-based materials depend on their PBG (or helical pitch), which is controlled by the self-assembly condition. Given this unique nano self-assembly behavior of CNC photonic crystals, several studies have examined these crystals not only for fundamental scientific interest but also for developing valuable functional and intelligent materials. [ 54 – 58 ] To the best of our knowledge, most of these studies are based on the inherent left-handed cholesteric phase structure of CNC; however, right-handed CNC systems have been rarely reported. Tsukruk et al. demonstrated a shear-induced twisted printing method, where the substrate was rotated clockwise or anticlockwise by a certain angle for printing a shear-oriented CNC layer, which provided an on-demand, customized transparent film with left- or right-handedness. [ 59 ] Similarly, Felix et al. modified the orientation of cellulose nanofibers (CNF) through spray-assisted alignment and layer-by-layer accumulation on a rotatable plate, yielding CNF films with different chiral properties. [ 60 ] These two abovementioned studies are the only state-of-the-art examples for preparing cellulose films with right-handed helical structures. In contrast, Ye et al. discovered the chiral inversion of CNC films with left-handed cholesteric structures under extremely high pressure; [ 61 ] however, the harsh conditions of chiral inversion decreased the practicality of this approach. Moreover, although other studies have partially achieved chiroptical inversion, [ 57 , 62 – 64 ] they have not truly obtained right-handed structures. In our previous work, we attempted to develop right-handed CNC-based materials; we used a rotational evaporation-induced self-assembly (REISA) method to produce a CNC film with right-handed helical features and provided a preliminary description of its chiroptical behavior. [ 65 ] Here, as shown in Fig. 1 , we used the same method to achieve emergent nonreciprocal CPL in CNC films for the first time by doping cadmium telluride quantum dots (CdTe QDs) with CNC. The chiroptical properties of the as-prepared right-handed CNC films were thoroughly investigated using polarized optical images (POMs) and reflectance and CD spectroscopies. The results demonstrated that the films exhibited dual reflections of CP light and “Janus” chiroptical property, which were regulated by film thickness, temperature, ionic strength, and pH. The structural morphology and orientation of the developed CNC films were analyzed by scanning electron microscopy (SEM) and 2D wide-angle X-ray scattering (2D WAXS), and the findings revealed that Hermans order parameter (S) increased due to rotation-induced orientation. The results for both CD and CPL showed that the as-prepared CNC films with right-handedness exhibited prominent out-of-plane anisotropy, enabling to achieve a new type of CPL functional materials. 2. Results and Discussion 2.1 Circularly polarized absorption and right-handed helical structure To prepare CNC films using the REISA method, a CNC colloidal suspension with a concentration of approximately 2.2wt% was prepared by sulfuric acid hydrolysis. As shown in Figure S1 , the nanoparticle size analysis revealed an effective average diameter of 185 nm for rod-like CNC particles with a zeta potential of -60.8 mV. Neglecting particles in the aggregated state, atomic force microscopy (AFM) displayed similar sizes for particles in the CNC suspension, wherein the average length and width of CNC particles were approximately 200 nm and 5 nm, respectively. The elemental analyzer (EA) showed a high sulfur content of 0.88wt%, indicating that the CNC suspension was acidic (pH 2.6). The REISA method yielded rigid CNC films (25℃, 15 g suspension for each film) with concentric textures, in which the orange outer areas and blue centers were distinct from each other ( Figure S2a ). Figure 2 shows CP absorption (known as apparent CD), one of the chiroptical features, for the orange outer areas of the as-prepared CNC films. The apparent CD signals of the as-prepared CNC films were recorded by rotating samples around the optical axis at 45° intervals from 0° to 315° and then flipping them 180° around the y-axis (Fig. 2 b). For both sides of each film, 16 apparent CD curves were plotted in Figure S3 ; the curves showed that rotation induced CNC films to exhibit negative CD signals that were weakly correlated with the magnetic field. Self-assembled CNC-based materials show left-handed nematic structures with positive CD signals. [ 57 , 66 ] Here, we considered a widely reported theoretical model to explore the origin of this unexpected negative CD signal. According to this model, apparent CD is the sum of isotropic component and anisotropic contribution and can be described by the following equation: [ 58 , 67 – 69 ] $$\:C{D}_{obs}\approx\:{CD}_{iso}+\frac{1}{2}(LD{\prime\:}\cdot\:LB-LD\cdot\:LB{\prime\:})\:$$ 1 where CD obs is apparent CD directly recorded through instrument testing; CD iso refers to genuine CD; the terms LD and LB denote linear dichroism (LD) and linear birefringence (LB) measured along the x-axis and y-axis, respectively; and the terms LDʹ and LBʹ represent LD and LB obtained along the bisectors of the x-axis and y-axis, respectively. On the one hand, as a reciprocal isotropic component, CD iso originates solely from the intrinsic chirality at different hierarchy levels, independent of the orientation, rotation, and flipping of the sample. On the other hand, the nonreciprocal contribution, i.e., LDLB, originates from the interference interaction of the macroscopic anisotropies in the solid sample. [ 67 – 70 ] LDLB, in particular, remains invariant upon rotating the sample around the optical axis (z-axis) but inverts its sign when the sample is flipped. It should be noted that LDLB is an actual and reproducible contribution rather an artifact. [ 68 , 70 ] Figure S4 shows non-ignorable LD signals collected together with apparent CDs. These noticeable LDs combined with apparent CD curves showing deviation from each other ( Figure S3 ) revealed considerable anisotropic contributions of LDLB to the chiroptical response in the rotated CNC films. In other words, the rotation enhanced the anisotropy of the CNC film, resulting in considerable nonreciprocal LDLB, which led to deviation and distinct differences in the apparent CD signals for the two sides of film, thereby exhibiting out-of-plane chiroptical anisotropy. To evaluate the intrinsic chirality of the as-prepared CNC films, it is essential to eliminate as much as possible the potential anisotropic interference of LDLB in Eq. ( 1 ) and then acquire the intrinsic isotropic CD iso . Because the sign of LDLB in Eq. ( 1 ) showed inversion after flipping the film, [ 70 ] we used a previously reported simple and effective approach [ 67 , 69 , 71 , 72 ] to decouple CD iso (average CD, Fig. 2 a) by averaging 16 apparent CDs. The average CDs for Ref-0 (reference sample prepared without rotation and magnetic field exposure) and for M ⊥ -0 and M ∥ -0 (samples prepared without rotation but exposed to perpendicular and parallel magnetic fields, respectively) were strictly positive; in contrast, the average CDs for other films were positive at shorter wavelengths but significantly negative at longer wavelengths. This change was more apparent when the rotation rate was ≥ 80 rpm; this finding possibly confirms that the novel right-handedness formed within the CNC film during rotation. The CNC film with the left-handed helical nematic phase usually reflects left-handed CP (L-CP) light and transmits right-handed CP (R-CP) light. As shown in Fig. 2 c, the reflections of L-CP light (red line) were higher than those of R-CP light (blue line) at a slower rotation speed, for example, Ref-0, M ⊥ -A30, and M ∥ -C40 (the samples were defined as M ∥ -Ax, M ∥ -Cx, M ⊥ -Ax, or M ⊥ -Cx, where M ∥ and M ⊥ denote parallel and perpendicular magnetic fields, respectively; A and C indicate anticlockwise and clockwise directions, respectively; and x denote the rotation rate). This observation was consistent with the characteristic of the left-handed nematic phase. Interestingly, with the increase in the rotation rate, the reflections of R-CP light were close to or even slightly exceeded those of L-CP light, such as M ⊥ -C100, M ⊥ -A100, M ∥ -C100, and M ∥ -A100. These results showed that the CNC films formed at a higher rotation rate could ambidextrously reflect L-CP and R-CP lights (Fig. 2 d). This finding was further validated through the POMs in Figs. 2 e and S5, where M ⊥ -0 and M ∥ -0 were dark in the R-CP channel due to no reflection of R-CP light. In contrast, the POMs for the films formed by rapid rotation showed the same level of brightness for both L-CP and R-CP lights; moreover, M ⊥ -A80 even displayed higher brightness in the R-CP channel. This unexpected R-CP light reflection might be related to the right-handedness confirmed by the negative average CD signals in CNC films. To confirm the right-handedness of the film, direct observations of twisted right-handed helical structures in the as-prepared CNC films by SEM served as robust evidence of the inverse chiroptical behavior, including negative average CD and R-CP light reflection. Figure 3 shows the stacked layered structures of M ∥ -0 and M ⊥ -0, where the CNC particles in each layer were approximately parallelly aligned. Fascicular twist structures comprising several assembled CNC particles were observed after the rotation process. Although the orientation and size of the twists varied among the films, right-handedness was a common feature in these films and could be observed from multiple dimensions ( Figures S6 and S7 ). This finding confirms that rotation promotes the formation of the right-handed twisted helical bundle during the self-assembly process of CNC, which directly manifests as inverse chiroptical activity. In other words, the fascicular twisted right-handed helices were primarily responsible for the negative average CD and R-CP light reflection, and the nonreciprocal LDLB component played a secondary role. A comparison with our previous study [ 65 ] indicated that a magnetic field of certain strength, which can induce CNC particles in the suspension to align to their chiral nematic axis (perpendicular to the long axis of individual CNC crystals) along the magnetic field because of intrinsic anisotropic diamagnetic susceptibility, [ 66 , 73 , 74 ] did not hinder the generation of right-handed helices. This suggests that such twisted right-handed structures are more prone to the formation of a larger helical pitch (P) than intrinsic left-handed chiral nematic structures, leading to the appearance of negative CD signals at longer wavelengths. Finally, it should be noted that the rotation-induced centrifugal force with gradient distribution along the rotation radius caused irregular distribution of the helical structures inside the film; however, these helices could be reproduced in different samples. Thus, the present study provides a promising strategy for constructing right-handed helices of CNC at the micro-nano level. 2.2 Structural color and light reflectance Although CNC films were prepared by a dynamic method as shown in Figure S2b , which disrupted the self-assembly of CNC particles, they still displayed iridescent structure color to a certain extent ( Figures S2a and S8 ). We summarized the reflection wavelength (λ max ) with the maximum reflectivity of the as-prepared films in Table 1 ; the data revealed three critical phenomena: (1) λ max initially decreased and later increased with the increase in the rotation rate up to 90 rpm; (2) anticlockwise rotation resulted in a larger λ max than clockwise rotation under the same rotational rate; and (3) perpendicular magnetic fields led to larger λ max as compared to parallel magnetic fields. Table 1 Reflection wavelength (λ max ) with maximum reflectivity of the CNC films under unpolarized light. Rotation rate (rpm) 0 20 30 40 60 70 80 90 100 No C 516 / / / / / 618 / / M ∥ C 523 < 400 / 417 490 511 526 599 593 A / 442 / 464 520 612 570 615 588 M ⊥ C 565 / 532 / 573 / 630 / 627 A / / 557 / 600 / 696 / 584 The CNC films were formed through clockwise (C) or anticlockwise (A) rotation without (No) or with parallel (M ∥ ) and perpendicular (M ⊥ ) magnetic fields. The reason underlying the first phenomenon could be the magnitude of the centrifugal force. In the stationary state (with no centrifugal force), size-dispersed CNC particles spontaneously assemble into left-handed cholesteric structures with conventional P. During rotation at a low speed, a smaller centrifugal force cannot yield right-handed structures; however, it can promote the separation of size-dispersed CNC particles according to the size gradient. Consequently, particles with similar sizes align more regularly and compactly, generating more uniform local domains with smaller P. With the increase in the rotational speed, a sufficient amount of centrifugal force is generated for CNC particles to undergo hierarchical assembly, leading to the formation of not only an inherent left-handed cholesteric structure but also a right-handed helix through twisting; consequently, the loose interlacing of the two structures creates a larger P. However, a stronger centrifugal force (such as that achieved at the rotational speed of 100 rpm) causes the two structures to form a tight stack, thereby decreasing P. Thereby, a similar change in λ max is presented according to the known relationship between λ max , P, and average refractive index (n) described by Bragg’s Law: [ 55 ] $$\:{\lambda\:}_{max}=nPcos\theta\:$$ 2 where θ refers to the angle between the incident light and the helical axis. In the Northern Hemisphere, the Earth’s self-rotation is anticlockwise, which inspires us to contemplate the fundamental source of the second phenomenon. As stated above, a faster speed of rotation can increase P. During the REISA process, the Earth’s self-rotation may negate and superimpose with the clockwise and anticlockwise rotation of CNC suspension, respectively, resulting in the anticlockwise rotated film exhibiting a larger P. Nevertheless, more efforts are required to obtain more precise and in-depth understanding of the mechanisms underlying aforementioned phenomena. The third phenomenon can be explained by the magnitude of the magnetic field. As reported earlier, the applied magnetic field can reduce the number of dislocations with the growth of CNC tactoids, contributing to a larger average packing volume between the particles, i.e., increased P value of CNC assemblies. [ 66 , 75 , 76 ] Because of the inherent limitations of the rotating setup ( Figure S2b ), although the same magnets were used, the spacing between the parallel magnetic field was greater than that between the perpendicular magnetic field, resulting in a more robust perpendicular magnetic field and subsequently a larger λ max . 2.3 Invariant centers of CNC films The blue centers of CNC films are distinct from the inversion of the orange outer areas, and the chiroptical characteristics of the blue centers are presented in Fig. 4 . As shown in Fig. 4 a, L-CP light reflection was significantly higher than R-CP light reflection even at higher rotational speeds, and the L-CP channel provided brighter optical images (Fig. 4 c). No difference was observed when compared with the property of the conventional left-handed nematic CNC film. This finding indicated the absence of right-handedness in the centers because the centrifugal force of the rotation center was not sufficiently strong to promote the handedness twist of the CNC assemblies. This difference indirectly reveals that the centrifugal force with an appropriate strength is the key to generate inverted right-handedness in CNC films fabricated through the REISA method. 2.4 In-plane and out-of-plane orientation study We further used 2D WAXS to quantitatively analyze the orientation degree of CNC films formed by rotating under parallel (Fig. 5 ) and perpendicular (Fig. 6 ) magnetic fields. Figures 5 a and 6 a show 2D WAXS patterns and intensities for in-plane orientation, and Figs. 5 b and 6 b display out-of-plane patterns and intensities. Cellulose I β crystal in CNC is usually characterized by 200 lattice plane and shows a remarkable X-ray diffraction peak at around 2θ = 22.8°, which corresponds to the scattering signal at around q = 1.61 Å −1 ( Figure S9 ). Here, the scattering intensity I(Ф) at around q = 1.61 Å −1 for the 200 lattice plane was extracted from the 2D WAXS pattern and plotted as the function of the azimuthal angle (Ф) for calculating the orientation factor, i.e., Hermans order parameter (S), based on the following equation: [ 77 – 80 ] $$\:S=1-3\frac{\int\:I\left(ф\right){cos}^{2}ф\:sinф\:dф}{\int\:I\left(ф\right)sinф\:dф}$$ 3 where 0 ≤ S ≤ 1, and S = 0 represents a fully isotropic system, while S = 1 represents an anisotropic system with perfect orientation. In Figs. 5 and 6 , the blue plots denote varying intensity of complete Debye rings (defined as circuit) for 200 lattice planes; the plots show symmetrical and asymmetrical bimodal distributions for in-plane and out-of-plane alignments, respectively. This could be attributed to the chiral nematic layers of the CNC film, i.e., the spirally stacked layers with inevitable interlayer gaps resulted in asymmetrical out-of-plane scattering patterns. In Fig. 5 b, the bimodal distribution of out-of-plane alignment was more asymmetrical at the slower rotation speed (M ∥ -A40 and M ∥ -C40). Additionally, I(Ф) of the 1/2 Debye ring covering the maximum intensity was also plotted from 0° to 180° (orange plot, defined as the integral region) for calculating the S value. It was observed that in-plane S values were lower than out-of-plane S values because rod-like CNC particles primarily aligned themselves parallel to the film surface. Additionally, the rotary direction did not affect the S value at slow speeds; however, a certain correlation was observed between the S value and the rotary direction at fast speeds, although the underlying mechanism remains unclear. In Fig. 6 c, the S was drawn as the function of the rotation rate and exhibited a significant improvement at a slower rotation speed regardless of its in-plane or out-of-plane orientation. However, with the increase in the rotation speed, the out-of-plane S values began to subside and fluctuate though they were still higher than the values at the starting point. The in-plane S values exhibited a gradual increase accompanied by fluctuations (Fig. 6 c). The reason why the bimodal distribution of I(Ф) was more asymmetrical at the slower rotation speed and the S values were higher might be identical to the reason for change in the reflected wavelength λ max , i.e., a smaller centrifugal force can promote only the separation of size-dispersed CNC particles according to size gradients at a slower rotation speed, resulting in more uniform local particle sizes. CNC particles with similar sizes then assembled into more organized local alignment domains with a clearer layered structure and more prominent orientation. However, the faster rotation speed disturbed the formation of the layered structure and weakened S to a certain extent. Despite this, the S values at higher rotation speeds were higher than those of Ref-0, M ∥ -0, and M ⊥ -0, indicating that the rotation process was beneficial to the orderly alignments of rod-like CNC particles. This result supported that the CNC film generated by rotation exhibited more significant anisotropy, enabling nonreciprocal LD and LB to play a greater role in the chiroptical response. 2.5 Tunable chiroptical activity The self-assembly of particles in CNC suspension is a subtle process influenced by multiple factors such as ionic strength, drying conditions, pH, stimulation of the external field, and particle parameters (surface charge and chemistry, dimension, and aspect ratio). [ 59 , 60 ] Based on the abovementioned discussion regarding the chiroptical behavior, right-handed helical structure, and orientation of CNC thin films prepared by the REISA method, we further investigated the tunability and CPL feasibility of the chiroptical activity. Films with varying suspension masses (25℃), drying temperatures (9 g suspension for each film), ionic strengths (25℃, 15 g suspension for each film), and pH values (25℃, 9 g suspension for each film) were prepared by clockwise rotation at 100 rpm within the perpendicular magnetic field, and the corresponding results were presented in Figs. 7 and S10. The structural color, CP reflection, and CD signal of these films were thoroughly evaluated. An increase in the suspension mass thickened the CNC film, which was visually manifested as a blue shift in structural color (Figs. 7 c and 7 d). Regarding chiroptical activity, although no significant difference was noted between reflected L-CP and R-CP lights (Fig. 7 a), the average CD suggested that film thickness affected chiral structure to a certain extent (Fig. 7 b). An increase in the drying temperature also caused similar but smaller changes in these three dimensions. Based on CP reflection (Fig. 7 a) and structural color (Fig. 7 c), the effects caused by the slight increase in ionic strength were negligible. However, the addition of 2.5 g 0.01 M sodium chloride solution to 9 g CNC suspension formed a film with stronger L-CP light reflection (Fig. 7 a); moreover, this film showed no negative CD signals at longer wavelengths, which was completely contrasting to other films treated with less sodium chloride solution ( Figures S10 and 7b ). Lastly, the complicated pH regulation was divided into three categories according to the pH value. On the one hand, under suitable acidic or alkaline condition such as pH = 3.0 or 11.5, respectively, retained inherent left-handed nematic structures and newly generated twisted right-handed helical bundles in CNC films were confirmed by positive average CD at short wavelengths and negative average CD at long wavelengths. These films were orange yellow and ambidextrously reflected CP light. On the other hand, under a stronger acidic or alkaline condition such as pH = 1.8 or 11.8, respectively, the chirality property was deprived, and an almost transparent film was formed without the ability of reflection. Different from the previous two categories, the colorful films with pH = 7 and 10.5 were light purple, particularly the former. It should be emphasized that negative average CD signals were not detected at long wavelengths, although the films exhibited negative apparent CD signals ( Figure S10 ). This observation was almost consistent with the stronger L-CP light reflection of the films. Among these four regulatory modes, the mechanisms underlying regulation by thickness and temperature remain a current research challenge. The mechanisms underlying regulation by ionic strength and pH involve the electrostatic effect, which plays a crucial role in the assembly of CNC particles. The varying ionic strength or system pH alters the electrostatic repulsion of CNC, forcing a shift in the balance of multiple forces. This results in the emergence of inconsistent assembly structures with different property features. 2.6 Nonreciprocal circularly polarized emission An interesting finding was the emergence of a novel nonreciprocal CPL activity during pH regulation when CdTe QDs were doped into CNC films under rotation, although the film showed a low g lum . In the context of the abovementioned results for regulating chiroptical activity, we considered pH regulation as a paradigm here to study the CPL feasibility of CdTe QDs-doped CNC films. Because CdTe QDs were stable only under alkaline conditions and the average CD detected from the film with pH 11.5 was significantly negative, the pH values of CdTe QDs-doped CNC suspensions (25℃, 9 g suspension for each film) were adjusted to 11.0, 11.2, and 11.5, and thin films were prepared by clockwise rotation at 100 rpm under the perpendicular magnetic field. As shown in Fig. 8 a, CdTe QDs-doped CNC films presented similar chiroptical properties, i.e., nonnegligible LDs and deviated and discrepant apparent CDs for the two sides; moreover, the three films exhibited clearly negative average CD signals. In particular, the positive CD signal of the thin film was very weak at pH 11.2. Additionally, L-CP and R-CP channels showed similar optical brightness when the films were observed by POM. Given the deviated apparent CDs, CPL spectra were recorded by rotating the film around the optical axis at 90° intervals from 0° to 270°, with four times testing for each side. As shown in Fig. 8 b, the film with pH 11.0 exhibited nonreciprocal CPL activity, as described in Fig. 8 c. When this CNC film was excited by UV light from side A, a negative CPL signal was detected, indicating a R-CP emitter. Conversely, a positive CPL signal was observed when the film was excited by UV light from side B, which manifested as a L-CP emitter. The nonreciprocal CPL activity was apparently tunable according to the pH value. For example, negative and positive CPL signals were detected at pH 11.2 although a deviation was noted in intensity and low g lum , while the nonreciprocity property disappeared at pH 11.5, exhibiting a common and single R-CP emitter. The overlap between PBG and luminescent emission wavelength is the key factor for chiral materials to emit CP light. [ 34 , 81 ] Although the three films showed negative average CDs, the results were not the same for PBG; thus, different overlaps were noted between their PBGs and the luminescent emission wavelength of CdTe QDs. Consequently, different CPL characteristics were observed in Fig. 8 b. The aqueous solution of CdTe QDs showed an emission wavelength of approximately 705 nm, and the fluorescence emissions (PL) significantly shifted to 570 ~ 580 nm after these QDs were doped into CNC films (Figs. 8 d and f ). As illustrated in Fig. 8 e, the reflections of CdTe QDs-doped films occurred at 640 ~ 670 nm. Therefore, by combining the reflection, PL, and CPL spectra, we concluded that the CPL signal was mainly achieved through the circularly polarized selective reflection mechanism. CP emission (known as apparent CPL) is another important chiroptical feature in thin films and has been widely investigated. However, because of the complexity of its underlying mechanisms, most of the studies present only the CPL phenomenon and potential applications; consequently, there are few theoretical models that can explicitly clarify the complicated nonreciprocal CPL behavior. Here, a reported model may provide valuable insights for interpreting the unprecedented nonreciprocal CPL activity. Similar to apparent CD, the apparent CPL included several contributions that can be \(\:C{PL}_{obs}\approx\:{CPL}_{iso}+(f{\prime\:}\cdot\:LB-f\cdot\:LB{\prime\:})\:\) (4) where CPL obs represents the apparent CPL directly observed through instrumental testing, CPL iso denotes the isotropic reciprocal component related only to intrinsic chirality at the molecular or higher scale, the second term (designated as fLB) affected by film alignment is the nonreciprocal contribution derived from macroscopically anisotropic interaction, and f and fʹ represent linear fluorescence anisotropy of the sample measured along the x-axis and y-axis and their bisectors, respectively. fLB shows inversion of its sign when the sample is flipped but remains constant when the film is rotated around the z-axis (optical axis). On the one hand, the results of 2D WAXS revealed that rotation amplified the anisotropy of CNC films, thus favoring the contribution of fLB to apparent CPL. On the other hand, both average CD and SEM indicated rotation-induced twisted right-handedness in CNC films. On the basis of these two points, we decomposed the apparent CPL of CNC films into four components according to Eq. (4), i.e., negative CPL iso -N from the inherent left-handed nematic phase, positive CPL iso -P from the rotation-induced right-handed helix, and nonreciprocal fLB components (negative fLB-N for A side and positive fLB-P for B side) contributed by anisotropy. As illustrated in Fig. 8 c, “CPL iso -N + fLB-N” was larger than CPL iso -P when the CNC film was excited from side A, resulting in a negative CPL obs . When the CNC film was excited from side B, “CPL iso -P + fLB-P” was larger than CPL iso -N, leading to a positive CPL obs . Therefore, we considered that the anisotropic fLB contribution is dominant for this nonreciprocal CPL activity that enables left- and right-handed CP emissions from the two opposite surfaces of the same film. Compared to nonreciprocal CPL, apparent CD did not exhibit nonreciprocal characteristics. According to equations ( 1 ) and (4), both apparent CD and CPL include isotropic and anisotropic components. But small anisotropic contribution cannot inverse the sign of apparent CD, resulting in the absence of nonreciprocal features. Rapidly growing interest in chiroptical materials has facilitated in-depth studies on reciprocal CP absorption and emission; in contrast, the nonreciprocal categories, particularly nonreciprocal CP emission, has been rarely studied. Developing a new type of a chiral functional material by harnessing only one enantiomer to obtain opposite chiroptical properties from the two opposite surfaces of the same film is not only of fundamental scientific interest, but also provides an exciting opportunity for broadening the scope of implications of CP absorbance and emission systems. The first case of such nonreciprocal chiroptical properties was reported by Deng et al. in 2019, where the authors developed a composite film comprising an achiral luminophore interlayer and two surfaces with opposite chiral helicity. [ 82 ] In 2020, Lorenzo et al. reported another interesting discovery, i.e., an organic thin film that displays almost enantiomer-like CD and CPL from its front and back surfaces, respectively. [ 83 ] In the present study, we achieved a similar unexpected chiroptical feature, i.e., nonreciprocal CPL, by using natural and sustainable CNC-based films. For advanced CNC-based materials that require an opposite chiroptical response, this feature not only simplifies the manufacturing procedure and reduces the overall cost by avoiding complex integration of materials with different handedness, but it is also a valuable breaking of CP emission reciprocity that inverts the CP light handedness following reversal of the emitted light wavevector. [ 83 , 84 ] Although this emergent nonreciprocal CPL-active material is still in its infancy, it has enormous potential for application in advancing next-generation of chiral electronics and photonics, for example, in the development of CP organic field-effect transistor (CP-OFET) that can differentiate the illumination direction and in the revolutionary innovation of highly efficient CP organic light-emitting diode (CP-OLED) with an increased output of CP from the device. [ 68 , 83 , 84 ] 3. Conclusion Mysterious chirality at different hierarchy scales exists widely in nature and has attracted increasing interest of researchers worldwide. CP absorption and emission, the two major components of chiroptics, are commonly known as apparent CD and CPL, respectively. Although reciprocal behaviors of both apparent CD and CPL are widely known, there is limited information on the nonreciprocal categories, particularly nonreciprocal CP emission. CNC, a natural, sustainable, and renewable material, is a highly promising building block for chiral photonic crystals; however, the right-handedness of CNC-based materials remains a challenge to be addressed. Here, we developed a rotation-induced dynamic assembly strategy that enables rod-like CNC particles to assemble into a twisted right-handed helix bundle in solid iridescent CNC films. These films can ambidextrously reflect left- and right-handed CP light because of the coexistence of the newly emerged right-handed helix bundle and the inherent left-handed helical nematic phase. The right-handedness was closely dependent on the rotation rate rather than on the rotation direction; moreover, it occurred only at the outer areas of the CNC film, whereas the center of the film retained the features of the left-handed helical nematic phase. With the increase in the rotation speed, the λ max value of the CNC film first decreased and then increased, and this value was larger when the CNC suspension was rotated anticlockwise. An increase in Hermann order parameter S revealed that the rotation process also enhanced the macroscopic anisotropy of the CNC film, causing nonnegligible contribution to apparent CD and CPL. These CNC films with right-handed helices exhibited a Janus chiroptical activity, i.e., anisotropic CP absorption and emission, on two opposite surfaces. The Janus chiroptical activity was tunable by controlling the mass, drying temperature, ionic strength, and pH of the CNC suspension. It should also be noted that CdTe QDs-doped CNC films exhibited a rare phenomenon of nonreciprocal CPL regulated by pH for the first time in CNC materials. In other words, CdTe QDs-doped CNC films could emit opposite CP light from their two opposite surfaces, without the requirement for the complex integration of materials with different handedness. Thus, the emergent nonreciprocal CPL broke the reciprocity in CP emission and opened new avenues to develop novel chiral functional materials by harnessing only one enantiomer to obtain opposite chiroptical properties in the same film; this feature is highly desired in developing next-generation chiral electronics and photonics such as CP-OFET for differentiating the illumination direction and efficient CP-OLED with an increased CP degree output. 4. Experimental Section Materials . Polyethylene glycol (PEG, Mn = 20000) and sodium hydroxide solution (0.5 M) were purchased from Aladdin Biochemical Technology Co., Ltd (Shanghai, China). Water-soluble CdTe QDs with a solid content of approximately 4 mg∙mL − 1 were supplied by Beida Jubang Science and Technology Co., Ltd (Beijing, China). The QDs were decorated with the carboxyl group and showed an emission wavelength of 705 nm. Sodium chloride solution (0.01 M) was provided by Shanghai Meryer Biochemical Technology Co., Ltd (Shanghai, China). Approximately 2.2wt% CNC suspension was prepared as reported previously. [ 65 ] Industrial neodymium magnets (NdFeB magnets) with the size of 60 mm × 60 mm × 30 mm were used for inducing the local magnetic field. One NdFeB magnet had a 9-mm-diameter hole in the center along the thickness direction to induce a perpendicular magnetic field. Preparation of CNC films . An appropriate amount of CNC suspension was completely mixed with the PEG solution (2wt%) in the mass ratio of 15:1. The mixed suspension was then added to a Petri dish (56 mm diameter) fixed on a rotary platform, which was driven by a tunable pulse signal. As illustrated in Figure S2b , two NdFeB magnets were placed on the left and right (or upper and lower) sides of the Petri dish for inducing a parallel or perpendicular magnetic field. The suspension was then rotated at the desired rotation rate and direction under ambient humidity and controlled temperature until it dried into a film. Samples were defined as M ∥ -Ax, M ∥ -Cx, M ⊥ -Ax, and M ⊥ -Cx, where M ∥ and M ⊥ represent parallel and perpendicular magnetic fields; A and C denote anticlockwise and clockwise rotation, respectively; and x represents the rotation rate (rpm). A and C were omitted when x = 0 rpm (without rotation). Ref-0 and Ref-C80 were used as two references without the application of the magnetic field. Sodium hydroxide and sodium chloride solutions were used to adjust the pH and ionic strength of the mixed suspension, respectively. Characterization . Nano-size and electric potential of the diluted CNC suspension were measured with a particle size and zeta potential analyzer (Omni, Brookhaven Instruments, USA) at 25°C. An atomic force microscope (MFP-3D, Oxford Instruments, USA) was used to observe the morphology of the diluted rod-like CNC particles on a pristine mica sheet. Sulfur content of dried CNC was determined by an elemental analyzer (Vario EL Cube, Element Corporation, Germany). A UV/Vis/NIR spectrometer (Lambda 750S, PerkinElmer, USA) was used for measuring reflectivity in the visible light range; additionally, a left- or right-handed CP filter was inserted into the light path to illuminate L-CP or R-CP light on the film surface. Polarized optical images (POMs) were captured on a Zeiss microscope (Axiolab 5) in the reflection mode as shown in Fig. 3 b. An inverted L-CP or R-CP filter was used to allow the reflected light from the film to travel through for distinguishing L-CP or R-CP light. CD spectra of CNC films were measured with the Jasco Model J-1500 spectrometer (Japan) from 820 to 200 nm at 1 nm data pitch and 200 nm∙min -1 rate. The CPL spectra from 800 to 450 nm were acquired on a Jasco CPL-300 spectrometer (Japan) with an excitation wavelength of 365 nm, data pitch of 0.5 nm, and a scanning rate of 500 nm∙min -1 . The RISE-MAGNA scanning electron microscope (TESCAN, Czech Republic) was used for capturing SEM images at 3 keV accelerating voltage and 30 pA current. Samples for viewing were prepared by peeling along the surface (or fracturing) and sputter coating the target surface with gold-palladium. Declarations Supporting Information Supporting Information is available from the author. Acknowledgements This work was financially supported by Interdisciplinary Program of Shanghai Jiao Tong University (YG2022QN085). References Yang, X., et al., Recent Progress of Circularly Polarized Luminescence Materials from Chinese Perspectives. 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Supplementary Files SupportingInformation.docx Emergent Nonreciprocal Dual Circularly Polarized Luminescence from an Iridescent Cellulose Nanocrystalline Film Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6164168","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":427823296,"identity":"5ebef999-841f-4a3c-a3e0-bc5ed92b898b","order_by":0,"name":"Xinling Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2klEQVRIiWNgGAWjYDACdjBpw8DYAKLZiNHCDCbTGBjbSNRyGKqaGC0Gh3kMPxf8Om/PPL/HgOFD2WEG/tkN+LVINvMYS8/su53Y2MZjwDjj3GEGiTsH8GvhZ+bdIM3bczuBEaiFmbftMIOBRAJ+LWzMvJt/8/acswdr+UuMFqAt26R5fhxgBDmMmZEYLZLN/N+seRuSgX5JKzjYcy6dR+IGAS0Gx9uSb/P8sbM3bD688cGPMms5/hkEtIABKBoNGxgYDgDZPESoB4E/DAzyRCodBaNgFIyCEQgAI8M9Awf1iasAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-1422-5265","institution":"School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai","correspondingAuthor":true,"prefix":"","firstName":"Xinling","middleName":"","lastName":"Wang","suffix":""},{"id":427823297,"identity":"8f44142b-eb55-4f6c-aeed-14835ddbfeab","order_by":1,"name":"Daikun Jia","email":"","orcid":"","institution":"School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai","correspondingAuthor":false,"prefix":"","firstName":"Daikun","middleName":"","lastName":"Jia","suffix":""},{"id":427823298,"identity":"031e4aa2-349f-4933-a675-4b309fd96fb6","order_by":2,"name":"Ruixin Zhu","email":"","orcid":"","institution":"School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai","correspondingAuthor":false,"prefix":"","firstName":"Ruixin","middleName":"","lastName":"Zhu","suffix":""},{"id":427823299,"identity":"d0f52a30-0efe-49d5-b642-dc02283b1094","order_by":3,"name":"Yuting Tian","email":"","orcid":"","institution":"School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai","correspondingAuthor":false,"prefix":"","firstName":"Yuting","middleName":"","lastName":"Tian","suffix":""},{"id":427823300,"identity":"62ae3935-0241-4afa-9162-213bf8a84c2b","order_by":4,"name":"Dandan Zhu","email":"","orcid":"","institution":"School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai","correspondingAuthor":false,"prefix":"","firstName":"Dandan","middleName":"","lastName":"Zhu","suffix":""}],"badges":[],"createdAt":"2025-03-05 15:55:33","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6164168/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6164168/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":78419985,"identity":"1d8bd990-d0a5-486c-aeea-dbc5c2096ab5","added_by":"auto","created_at":"2025-03-13 05:33:23","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":320539,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Preparation of the anisotropic CNC film with dual chirality and (b) its chiroptical activity.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6164168/v1/aa5255c3a4c865ef53569e72.png"},{"id":78419986,"identity":"f0a49ed1-e620-48d8-a9df-7fcb2386ae51","added_by":"auto","created_at":"2025-03-13 05:33:23","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":802659,"visible":true,"origin":"","legend":"\u003cp\u003eChiroptical properties of the as-prepared CNC films. (a) Average CD spectra showing the intrinsic chiral helixes. (b) Schematic illustration for determining average CD. (c) Reflectance spectra under left- and right-handed CP (L-CP and R-CP, respectively) light. (d) Schematic reflected illustration of dual CP light. (e) Polarized optical images (POMs) captured from L-CP (red arrow) and R-CP (blue arrow) light channels.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6164168/v1/9715dc088bd5b56c74dda813.png"},{"id":78419988,"identity":"92b1de54-cb1b-4abb-b54a-e696c0e7671f","added_by":"auto","created_at":"2025-03-13 05:33:23","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":426654,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of the typical CNC films with parallel and perpendicular magnetic fields. The yellow dashed line shows the twisted right-handed helical structure.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6164168/v1/ae7b6a597fb6ef2d26d4f886.png"},{"id":78423271,"identity":"41b7bc6e-1e8d-46ef-bf79-58b355314b17","added_by":"auto","created_at":"2025-03-13 06:05:23","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":213493,"visible":true,"origin":"","legend":"\u003cp\u003eChiroptical characteristics of the centers of paradigmatic CNC films. (a) Reflectance spectra of the centers under L-CP and R-CP lights. (b) Schematic illustration for collecting (c) POMs of CNC films from L-CPand R-CPchannels.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6164168/v1/bcb85797cc7233af0e2823ec.png"},{"id":78419989,"identity":"bc9b8c69-b738-48fc-a9bf-91774824d50a","added_by":"auto","created_at":"2025-03-13 05:33:23","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":602333,"visible":true,"origin":"","legend":"\u003cp\u003e2D WAXS analysis of CNC films formed in the parallel magnetic field. (a) In-plane and (b) out-of-plane orientation degree. The 2D color images with the concentric green Debye ring show WAXS patterns. The characteristicscattering of the CNC crystal (corresponding to 200 lattice plane) is extracted to plot the intensity curve versus the azimuthal angle. The blue line represents the varying scattering intensity of a complete Debye ring (circuit), while the orange line represents the varying scattering intensity of a 1/2 Debye ring (defined as 0°~180 °, integral region).\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6164168/v1/cd072d7dc92581909857f44a.png"},{"id":78419999,"identity":"ba49a440-7eb0-490f-ad2d-cbb2591e1ab9","added_by":"auto","created_at":"2025-03-13 05:33:23","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":289973,"visible":true,"origin":"","legend":"\u003cp\u003e2D WAXS analysis of CNC films formed in the perpendicular magnetic field. (a) In-plane and (b) out-of-plane orientation degree. (c) Hermans order parameter (S) of (c1) out-of-plane and (c2) in-plane orientation versus the rotation rate. The 2D color images with the concentric green Debye ring represent WAXS patterns. The characteristic signal of CNC crystals (corresponding to 200 lattice plane) is extracted to plot the intensity curve versus the azimuthal angle. The blue line represents the varying scattering intensity of a complete Debye ring, and the orange line displays the varying scattering intensity of a 1/2 Debye ring (defined as 0° ~180°, integral region).\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6164168/v1/c13d84e89566af97e0858031.png"},{"id":78423272,"identity":"94912210-4950-4dbd-8947-788491ef322d","added_by":"auto","created_at":"2025-03-13 06:05:23","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":536116,"visible":true,"origin":"","legend":"\u003cp\u003eCD and CPL properties of CdTe quantum dots-doped CNC films with different pH values. (a) CD spectra and concomitant data (the illustrations are POMs under L-CP and R-CP light). (b) Adjustable nonreciprocal CPL spectra. (c) Schematic illustration of nonreciprocal CPL. (d) Normalized excitation and emission spectra of the CdTe quantum dot solution. (e) Normalizedreflectance and (f) photoluminescence (PL) spectra of CNC films.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-6164168/v1/ea251b68ec2106040c70e27a.png"},{"id":81837490,"identity":"096094ec-cf25-40ed-aeba-bc4d06573323","added_by":"auto","created_at":"2025-05-02 15:19:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4252112,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6164168/v1/3b60ed87-312d-4240-8c66-86035767a10d.pdf"},{"id":78419997,"identity":"4d044129-5b68-4a41-a472-740e0ebd1ca8","added_by":"auto","created_at":"2025-03-13 05:33:23","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":2885706,"visible":true,"origin":"","legend":"Emergent Nonreciprocal Dual Circularly Polarized Luminescence from an Iridescent Cellulose Nanocrystalline Film","description":"","filename":"SupportingInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-6164168/v1/11da405cf23b07cb63bb536b.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"\u003cp\u003eEmergent Nonreciprocal Dual Circularly Polarized Luminescence from an Iridescent Cellulose Nanocrystalline Film\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eChirality, a property in which an object is not superimposed but is symmetrical with its mirror image, is one of the essential attributes of nature across macro to micro scales globally.\u003csup\u003e[\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e At the macro level, the mysterious nebula and the occasional cyclone show macroscopic helical chirality,\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e ordinary plant tendrils grow naturally by coiling through a left- or right-handed helix,\u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e and the attractive conch shell displays an inherent helical structure.\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e At the micro-nano scale, double-helical DNA chains and certain small organic molecules exhibit unique chirality and corresponding properties.\u003csup\u003e[\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e Inspired by natural chirality, researchers have made considerable efforts to explore the mysteries of chirality in physics,\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e biology,\u003csup\u003e[\u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e and chemistry\u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. In terms of materials, Liu and Yashima have summarized several significant achievements related to polymers with preferred-handed helical conformations induced by external chiral stimuli,\u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e which provides a systematic understanding of the formation and mechanism of chiral structures in materials.\u003c/p\u003e \u003cp\u003eWith rapid advancements in chiral research, chiroptics and corresponding materials have attracted considerable interest worldwide because of their huge prospects. The potential of circularly polarized (CP) absorption and emission, two critical aspects of chiroptics, is usually evaluated based on circular dichroism (CD) and circularly polarized luminescence (CPL). CPL has highly attractive potential applications in various advanced technology fields such as photoelectronic devices,\u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e spintronic devices,\u003csup\u003e[\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e information encryption and anti-counterfeiting,\u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e optical data storage/quantum information,\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e 3D display,\u003csup\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e CPL lasers,\u003csup\u003e[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e smart sensors/detectors,\u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan additionalcitationids=\"CR32\" citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]\u003c/sup\u003e, and asymmetric synthesis\u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. Consequently, CPL-active materials with high luminescent quantum yield and excellent luminescent asymmetric g-factor (g\u003csub\u003elum\u003c/sub\u003e) are currently one of the most popular optical materials because of their remarkable optical sensitivity and spatial resolution. As paradigms, Ye et al. reported a CP room temperature phosphorescence-active material developed by incorporating naphthalene- and pyrene-doped polymethyl methacrylate into a cellulose nanocrystalline (CNC) film, therefore providing a chiral environment with tunable photonic bandgap (PBG) for achieving switchable CP phosphorescence with long-lasting afterglow.\u003csup\u003e[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]\u003c/sup\u003e Recently, Gong et al. presented a co-doping strategy in which chiral naphthylphosphoric acid derivatives, rhodamine B, and polyvinyl alcohol were selected as the donors, acceptor, and matrix, respectively, which enabled to precisely control the afterglow color of the CPL-active film for application in anti-counterfeiting and encryption.\u003csup\u003e[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]\u003c/sup\u003e In 2023, Yu et al. developed a printable CPL-active photonic paint for 3D display in next-generation wearable and smart electronics by using a confining helical co-assembly strategy; this strategy allowed controllable and macroscopic preparation of flexible CPL devices by printing on various substrates.\u003csup\u003e[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/sup\u003e In the same year, Zhuang\u0026rsquo;s group achieved multilayer optical information encoding by using CPL-active materials to meet the increasing needs for anti-counterfeiting.\u003csup\u003e[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/sup\u003e More recently, Zhuang et al.\u003csup\u003e[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/sup\u003e and Liu et al.\u003csup\u003e[\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]\u003c/sup\u003e successively reported full-color CPL ranging from blue to green to red by adopting different strategies. In the former study, a single-emitted helical-caging with the largest g\u003csub\u003elum\u003c/sub\u003e of 0.8 was reported, while in the latter study, CPL involved dynamically adjustable supramolecular polymers. In addition to the abovementioned studies, several notable investigations on CPL have been reported.\u003csup\u003e[\u003cspan additionalcitationids=\"CR41 CR42 CR43 CR44 CR45 CR46\" citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]\u003c/sup\u003e However, it should be noted that the current research on CPL materials is primarily focused on tunable color, intensity, and feasible applications. Some advanced CPL achievements have also been reported, for example, Duan et al. proposed a unique multiple emission system through co-assembly of chiral annihilators and a sensitizer, thus forming upconverting and downshifting CPL.\u003csup\u003e[\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]\u003c/sup\u003e Subsequently, a reversible optical-mechanical dual-responsive CPL elastomer was prepared, its CPL signal could be weaken or even disappear under visible light or after stretching.\u003csup\u003e[\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]\u003c/sup\u003e A series of CPL-active copolymers with adjustable lifetime was constructed by modulating energy transfer efficiency, which facilitated the molecular regulation of CPL lifetime at the millisecond scale.\u003csup\u003e[\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e]\u003c/sup\u003e Zhao and coworkers constructed a novel through-space conjugated chiral foldamer, which enabled switchable dual CPL with opposite signs at different emission wavelengths and overcame the limitation of most CPL-active systems that exhibit CPL only at a single wavelength.\u003csup\u003e[\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e]\u003c/sup\u003e These emerging findings are promising for accelerating the development, in-depth understanding, and broad-spectrum application of CPL-active materials; nonetheless, very few studies have reported nonreciprocal CPL as a chiroptical phenomenon in which the sign of CPL inverses with the inversion of the propagation direction of excitation light. In contrast, reciprocal chiroptical properties (reciprocal CD and CPL) have been frequently studied.\u003c/p\u003e \u003cp\u003eCNC suspensions can be obtained from abundant renewable plant resources. Above a certain critical concentration, CNC forms ordered cholesteric liquid crystals from disordered isotropic colloids.\u003csup\u003e[\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e]\u003c/sup\u003e This implies that an individual CNC particle spontaneously deposits downwards and shows parallel alignment to the directional vector. The particle is periodically deflected clockwise due to spatial repulsion and electrostatic interaction, resulting in a certain angle between the adjacent alignment layers and the corresponding axially chiral helix, which is retained in the solid state. Finally, the incident CP light with the same or opposite handedness is selectively reflected or transmitted when the wavelength adequately matches the periodic helical structure according to Bragg\u0026rsquo;s law.\u003csup\u003e[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e]\u003c/sup\u003e Therefore, CNC is considered an ideal environmentally friendly alternative photonic crystal for sustainably developing iridescent chiral nematic functional materials with CP light response. The structural color and CPL property of CNC-based materials depend on their PBG (or helical pitch), which is controlled by the self-assembly condition. Given this unique nano self-assembly behavior of CNC photonic crystals, several studies have examined these crystals not only for fundamental scientific interest but also for developing valuable functional and intelligent materials.\u003csup\u003e[\u003cspan additionalcitationids=\"CR55 CR56 CR57\" citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e]\u003c/sup\u003e To the best of our knowledge, most of these studies are based on the inherent left-handed cholesteric phase structure of CNC; however, right-handed CNC systems have been rarely reported. Tsukruk et al. demonstrated a shear-induced twisted printing method, where the substrate was rotated clockwise or anticlockwise by a certain angle for printing a shear-oriented CNC layer, which provided an on-demand, customized transparent film with left- or right-handedness.\u003csup\u003e[\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e]\u003c/sup\u003e Similarly, Felix et al. modified the orientation of cellulose nanofibers (CNF) through spray-assisted alignment and layer-by-layer accumulation on a rotatable plate, yielding CNF films with different chiral properties.\u003csup\u003e[\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e]\u003c/sup\u003e These two abovementioned studies are the only state-of-the-art examples for preparing cellulose films with right-handed helical structures. In contrast, Ye et al. discovered the chiral inversion of CNC films with left-handed cholesteric structures under extremely high pressure;\u003csup\u003e[\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e]\u003c/sup\u003e however, the harsh conditions of chiral inversion decreased the practicality of this approach. Moreover, although other studies have partially achieved chiroptical inversion,\u003csup\u003e[\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e, \u003cspan additionalcitationids=\"CR63\" citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e]\u003c/sup\u003e they have not truly obtained right-handed structures.\u003c/p\u003e \u003cp\u003eIn our previous work, we attempted to develop right-handed CNC-based materials; we used a rotational evaporation-induced self-assembly (REISA) method to produce a CNC film with right-handed helical features and provided a preliminary description of its chiroptical behavior.\u003csup\u003e[\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e]\u003c/sup\u003e Here, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, we used the same method to achieve emergent nonreciprocal CPL in CNC films for the first time by doping cadmium telluride quantum dots (CdTe QDs) with CNC. The chiroptical properties of the as-prepared right-handed CNC films were thoroughly investigated using polarized optical images (POMs) and reflectance and CD spectroscopies. The results demonstrated that the films exhibited dual reflections of CP light and \u0026ldquo;Janus\u0026rdquo; chiroptical property, which were regulated by film thickness, temperature, ionic strength, and pH. The structural morphology and orientation of the developed CNC films were analyzed by scanning electron microscopy (SEM) and 2D wide-angle X-ray scattering (2D WAXS), and the findings revealed that Hermans order parameter (S) increased due to rotation-induced orientation. The results for both CD and CPL showed that the as-prepared CNC films with right-handedness exhibited prominent out-of-plane anisotropy, enabling to achieve a new type of CPL functional materials.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"2. Results and Discussion","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Circularly polarized absorption and right-handed helical structure\u003c/h2\u003e \u003cp\u003eTo prepare CNC films using the REISA method, a CNC colloidal suspension with a concentration of approximately 2.2wt% was prepared by sulfuric acid hydrolysis. As shown in \u003cb\u003eFigure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e\u003c/b\u003e, the nanoparticle size analysis revealed an effective average diameter of 185 nm for rod-like CNC particles with a zeta potential of -60.8 mV. Neglecting particles in the aggregated state, atomic force microscopy (AFM) displayed similar sizes for particles in the CNC suspension, wherein the average length and width of CNC particles were approximately 200 nm and 5 nm, respectively. The elemental analyzer (EA) showed a high sulfur content of 0.88wt%, indicating that the CNC suspension was acidic (pH 2.6). The REISA method yielded rigid CNC films (25℃, 15 g suspension for each film) with concentric textures, in which the orange outer areas and blue centers were distinct from each other (\u003cb\u003eFigure S2a\u003c/b\u003e). Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows CP absorption (known as apparent CD), one of the chiroptical features, for the orange outer areas of the as-prepared CNC films. The apparent CD signals of the as-prepared CNC films were recorded by rotating samples around the optical axis at 45\u0026deg; intervals from 0\u0026deg; to 315\u0026deg; and then flipping them 180\u0026deg; around the y-axis (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). For both sides of each film, 16 apparent CD curves were plotted in \u003cb\u003eFigure S3\u003c/b\u003e; the curves showed that rotation induced CNC films to exhibit negative CD signals that were weakly correlated with the magnetic field. Self-assembled CNC-based materials show left-handed nematic structures with positive CD signals.\u003csup\u003e[\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e, \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e]\u003c/sup\u003e Here, we considered a widely reported theoretical model to explore the origin of this unexpected negative CD signal. According to this model, apparent CD is the sum of isotropic component and anisotropic contribution and can be described by the following equation:\u003csup\u003e[\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan additionalcitationids=\"CR68\" citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e]\u003c/sup\u003e\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:C{D}_{obs}\\approx\\:{CD}_{iso}+\\frac{1}{2}(LD{\\prime\\:}\\cdot\\:LB-LD\\cdot\\:LB{\\prime\\:})\\:$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere CD\u003csub\u003eobs\u003c/sub\u003e is apparent CD directly recorded through instrument testing; CD\u003csub\u003eiso\u003c/sub\u003e refers to genuine CD; the terms LD and LB denote linear dichroism (LD) and linear birefringence (LB) measured along the x-axis and y-axis, respectively; and the terms LDʹ and LBʹ represent LD and LB obtained along the bisectors of the x-axis and y-axis, respectively. On the one hand, as a reciprocal isotropic component, CD\u003csub\u003eiso\u003c/sub\u003e originates solely from the intrinsic chirality at different hierarchy levels, independent of the orientation, rotation, and flipping of the sample. On the other hand, the nonreciprocal contribution, i.e., LDLB, originates from the interference interaction of the macroscopic anisotropies in the solid sample.\u003csup\u003e[\u003cspan additionalcitationids=\"CR68 CR69\" citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eLDLB, in particular, remains invariant upon rotating the sample around the optical axis (z-axis) but inverts its sign when the sample is flipped. It should be noted that LDLB is an actual and reproducible contribution rather an artifact.\u003csup\u003e[\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e, \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e]\u003c/sup\u003e \u003cb\u003eFigure S4\u003c/b\u003e shows non-ignorable LD signals collected together with apparent CDs. These noticeable LDs combined with apparent CD curves showing deviation from each other (\u003cb\u003eFigure S3\u003c/b\u003e) revealed considerable anisotropic contributions of LDLB to the chiroptical response in the rotated CNC films. In other words, the rotation enhanced the anisotropy of the CNC film, resulting in considerable nonreciprocal LDLB, which led to deviation and distinct differences in the apparent CD signals for the two sides of film, thereby exhibiting out-of-plane chiroptical anisotropy.\u003c/p\u003e \u003cp\u003eTo evaluate the intrinsic chirality of the as-prepared CNC films, it is essential to eliminate as much as possible the potential anisotropic interference of LDLB in Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) and then acquire the intrinsic isotropic CD\u003csub\u003eiso\u003c/sub\u003e. Because the sign of LDLB in Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) showed inversion after flipping the film,\u003csup\u003e[\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e]\u003c/sup\u003e we used a previously reported simple and effective approach\u003csup\u003e[\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e, \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e, \u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e71\u003c/span\u003e, \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e]\u003c/sup\u003e to decouple CD\u003csub\u003eiso\u003c/sub\u003e (average CD, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea) by averaging 16 apparent CDs. The average CDs for Ref-0 (reference sample prepared without rotation and magnetic field exposure) and for M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e-0 and M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e-0 (samples prepared without rotation but exposed to perpendicular and parallel magnetic fields, respectively) were strictly positive; in contrast, the average CDs for other films were positive at shorter wavelengths but significantly negative at longer wavelengths. This change was more apparent when the rotation rate was \u0026ge;\u0026thinsp;80 rpm; this finding possibly confirms that the novel right-handedness formed within the CNC film during rotation. The CNC film with the left-handed helical nematic phase usually reflects left-handed CP (L-CP) light and transmits right-handed CP (R-CP) light. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec, the reflections of L-CP light (red line) were higher than those of R-CP light (blue line) at a slower rotation speed, for example, Ref-0, M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e-A30, and M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e-C40 (the samples were defined as M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e-Ax, M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e-Cx, M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e-Ax, or M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e-Cx, where M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e and M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e denote parallel and perpendicular magnetic fields, respectively; A and C indicate anticlockwise and clockwise directions, respectively; and x denote the rotation rate). This observation was consistent with the characteristic of the left-handed nematic phase. Interestingly, with the increase in the rotation rate, the reflections of R-CP light were close to or even slightly exceeded those of L-CP light, such as M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e-C100, M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e-A100, M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e-C100, and M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e-A100. These results showed that the CNC films formed at a higher rotation rate could ambidextrously reflect L-CP and R-CP lights (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed). This finding was further validated through the POMs in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee and S5, where M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e-0 and M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e-0 were dark in the R-CP channel due to no reflection of R-CP light. In contrast, the POMs for the films formed by rapid rotation showed the same level of brightness for both L-CP and R-CP lights; moreover, M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e-A80 even displayed higher brightness in the R-CP channel. This unexpected R-CP light reflection might be related to the right-handedness confirmed by the negative average CD signals in CNC films.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo confirm the right-handedness of the film, direct observations of twisted right-handed helical structures in the as-prepared CNC films by SEM served as robust evidence of the inverse chiroptical behavior, including negative average CD and R-CP light reflection. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the stacked layered structures of M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e-0 and M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e-0, where the CNC particles in each layer were approximately parallelly aligned. Fascicular twist structures comprising several assembled CNC particles were observed after the rotation process. Although the orientation and size of the twists varied among the films, right-handedness was a common feature in these films and could be observed from multiple dimensions (\u003cb\u003eFigures S6\u003c/b\u003e and \u003cb\u003eS7\u003c/b\u003e). This finding confirms that rotation promotes the formation of the right-handed twisted helical bundle during the self-assembly process of CNC, which directly manifests as inverse chiroptical activity. In other words, the fascicular twisted right-handed helices were primarily responsible for the negative average CD and R-CP light reflection, and the nonreciprocal LDLB component played a secondary role. A comparison with our previous study\u003csup\u003e[\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e]\u003c/sup\u003e indicated that a magnetic field of certain strength, which can induce CNC particles in the suspension to align to their chiral nematic axis (perpendicular to the long axis of individual CNC crystals) along the magnetic field because of intrinsic anisotropic diamagnetic susceptibility,\u003csup\u003e[\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e, \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e73\u003c/span\u003e, \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e]\u003c/sup\u003e did not hinder the generation of right-handed helices. This suggests that such twisted right-handed structures are more prone to the formation of a larger helical pitch (P) than intrinsic left-handed chiral nematic structures, leading to the appearance of negative CD signals at longer wavelengths. Finally, it should be noted that the rotation-induced centrifugal force with gradient distribution along the rotation radius caused irregular distribution of the helical structures inside the film; however, these helices could be reproduced in different samples. Thus, the present study provides a promising strategy for constructing right-handed helices of CNC at the micro-nano level.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Structural color and light reflectance\u003c/h2\u003e \u003cp\u003eAlthough CNC films were prepared by a dynamic method as shown in \u003cb\u003eFigure S2b\u003c/b\u003e, which disrupted the self-assembly of CNC particles, they still displayed iridescent structure color to a certain extent (\u003cb\u003eFigures S2a\u003c/b\u003e and \u003cb\u003eS8\u003c/b\u003e). We summarized the reflection wavelength (λ\u003csub\u003emax\u003c/sub\u003e) with the maximum reflectivity of the as-prepared films in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e; the data revealed three critical phenomena: (1) λ\u003csub\u003emax\u003c/sub\u003e initially decreased and later increased with the increase in the rotation rate up to 90 rpm; (2) anticlockwise rotation resulted in a larger λ\u003csub\u003emax\u003c/sub\u003e than clockwise rotation under the same rotational rate; and (3) perpendicular magnetic fields led to larger λ\u003csub\u003emax\u003c/sub\u003e as compared to parallel magnetic fields.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eReflection wavelength (λ\u003csub\u003emax\u003c/sub\u003e) with maximum reflectivity of the CNC films under unpolarized light.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eRotation rate (rpm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e80\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003e90\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eNo\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eC\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e516\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e618\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003eM\u003c/b\u003e\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eC\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e523\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e417\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e490\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e511\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e526\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e599\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e593\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eA\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e442\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e464\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e520\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e612\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e570\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e615\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e588\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003eM\u003c/b\u003e\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eC\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e565\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e532\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e573\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e630\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e627\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eA\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e557\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e696\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e584\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe CNC films were formed through clockwise (C) or anticlockwise (A) rotation without (No) or with parallel (M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e) and perpendicular (M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e) magnetic fields.\u003c/p\u003e \u003cp\u003eThe reason underlying the first phenomenon could be the magnitude of the centrifugal force. In the stationary state (with no centrifugal force), size-dispersed CNC particles spontaneously assemble into left-handed cholesteric structures with conventional P. During rotation at a low speed, a smaller centrifugal force cannot yield right-handed structures; however, it can promote the separation of size-dispersed CNC particles according to the size gradient. Consequently, particles with similar sizes align more regularly and compactly, generating more uniform local domains with smaller P. With the increase in the rotational speed, a sufficient amount of centrifugal force is generated for CNC particles to undergo hierarchical assembly, leading to the formation of not only an inherent left-handed cholesteric structure but also a right-handed helix through twisting; consequently, the loose interlacing of the two structures creates a larger P. However, a stronger centrifugal force (such as that achieved at the rotational speed of 100 rpm) causes the two structures to form a tight stack, thereby decreasing P. Thereby, a similar change in λ\u003csub\u003emax\u003c/sub\u003e is presented according to the known relationship between λ\u003csub\u003emax\u003c/sub\u003e, P, and average refractive index (n) described by Bragg\u0026rsquo;s Law:\u003csup\u003e[\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e]\u003c/sup\u003e\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:{\\lambda\\:}_{max}=nPcos\\theta\\:$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere θ refers to the angle between the incident light and the helical axis.\u003c/p\u003e \u003cp\u003eIn the Northern Hemisphere, the Earth\u0026rsquo;s self-rotation is anticlockwise, which inspires us to contemplate the fundamental source of the second phenomenon. As stated above, a faster speed of rotation can increase P. During the REISA process, the Earth\u0026rsquo;s self-rotation may negate and superimpose with the clockwise and anticlockwise rotation of CNC suspension, respectively, resulting in the anticlockwise rotated film exhibiting a larger P. Nevertheless, more efforts are required to obtain more precise and in-depth understanding of the mechanisms underlying aforementioned phenomena. The third phenomenon can be explained by the magnitude of the magnetic field. As reported earlier, the applied magnetic field can reduce the number of dislocations with the growth of CNC tactoids, contributing to a larger average packing volume between the particles, i.e., increased P value of CNC assemblies.\u003csup\u003e[\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e, \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e75\u003c/span\u003e, \u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e76\u003c/span\u003e]\u003c/sup\u003e Because of the inherent limitations of the rotating setup (\u003cb\u003eFigure S2b\u003c/b\u003e), although the same magnets were used, the spacing between the parallel magnetic field was greater than that between the perpendicular magnetic field, resulting in a more robust perpendicular magnetic field and subsequently a larger λ\u003csub\u003emax\u003c/sub\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Invariant centers of CNC films\u003c/h2\u003e \u003cp\u003eThe blue centers of CNC films are distinct from the inversion of the orange outer areas, and the chiroptical characteristics of the blue centers are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, L-CP light reflection was significantly higher than R-CP light reflection even at higher rotational speeds, and the L-CP channel provided brighter optical images (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). No difference was observed when compared with the property of the conventional left-handed nematic CNC film. This finding indicated the absence of right-handedness in the centers because the centrifugal force of the rotation center was not sufficiently strong to promote the handedness twist of the CNC assemblies. This difference indirectly reveals that the centrifugal force with an appropriate strength is the key to generate inverted right-handedness in CNC films fabricated through the REISA method.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 In-plane and out-of-plane orientation study\u003c/h2\u003e \u003cp\u003eWe further used 2D WAXS to quantitatively analyze the orientation degree of CNC films formed by rotating under parallel (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e) and perpendicular (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) magnetic fields. Figures\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea show 2D WAXS patterns and intensities for in-plane orientation, and Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb display out-of-plane patterns and intensities. Cellulose I\u003cem\u003eβ\u003c/em\u003e crystal in CNC is usually characterized by 200 lattice plane and shows a remarkable X-ray diffraction peak at around 2θ\u0026thinsp;=\u0026thinsp;22.8\u0026deg;, which corresponds to the scattering signal at around q\u0026thinsp;=\u0026thinsp;1.61 \u0026Aring;\u003csup\u003e\u0026minus;1\u003c/sup\u003e (\u003cb\u003eFigure S9\u003c/b\u003e). Here, the scattering intensity I(Ф) at around q\u0026thinsp;=\u0026thinsp;1.61 \u0026Aring;\u003csup\u003e\u0026minus;1\u003c/sup\u003e for the 200 lattice plane was extracted from the 2D WAXS pattern and plotted as the function of the azimuthal angle (Ф) for calculating the orientation factor, i.e., Hermans order parameter (S), based on the following equation:\u003csup\u003e[\u003cspan additionalcitationids=\"CR78 CR79\" citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e80\u003c/span\u003e]\u003c/sup\u003e\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\:S=1-3\\frac{\\int\\:I\\left(ф\\right){cos}^{2}ф\\:sinф\\:dф}{\\int\\:I\\left(ф\\right)sinф\\:dф}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere 0\u0026thinsp;\u0026le;\u0026thinsp;S\u0026thinsp;\u0026le;\u0026thinsp;1, and S\u0026thinsp;=\u0026thinsp;0 represents a fully isotropic system, while S\u0026thinsp;=\u0026thinsp;1 represents an anisotropic system with perfect orientation. In Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, the blue plots denote varying intensity of complete Debye rings (defined as circuit) for 200 lattice planes; the plots show symmetrical and asymmetrical bimodal distributions for in-plane and out-of-plane alignments, respectively. This could be attributed to the chiral nematic layers of the CNC film, i.e., the spirally stacked layers with inevitable interlayer gaps resulted in asymmetrical out-of-plane scattering patterns. In Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, the bimodal distribution of out-of-plane alignment was more asymmetrical at the slower rotation speed (M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e-A40 and M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e-C40). Additionally, I(Ф) of the 1/2 Debye ring covering the maximum intensity was also plotted from 0\u0026deg; to 180\u0026deg; (orange plot, defined as the integral region) for calculating the S value. It was observed that in-plane S values were lower than out-of-plane S values because rod-like CNC particles primarily aligned themselves parallel to the film surface. Additionally, the rotary direction did not affect the S value at slow speeds; however, a certain correlation was observed between the S value and the rotary direction at fast speeds, although the underlying mechanism remains unclear. In Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec, the S was drawn as the function of the rotation rate and exhibited a significant improvement at a slower rotation speed regardless of its in-plane or out-of-plane orientation. However, with the increase in the rotation speed, the out-of-plane S values began to subside and fluctuate though they were still higher than the values at the starting point. The in-plane S values exhibited a gradual increase accompanied by fluctuations (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec). The reason why the bimodal distribution of I(Ф) was more asymmetrical at the slower rotation speed and the S values were higher might be identical to the reason for change in the reflected wavelength λ\u003csub\u003emax\u003c/sub\u003e, i.e., a smaller centrifugal force can promote only the separation of size-dispersed CNC particles according to size gradients at a slower rotation speed, resulting in more uniform local particle sizes. CNC particles with similar sizes then assembled into more organized local alignment domains with a clearer layered structure and more prominent orientation. However, the faster rotation speed disturbed the formation of the layered structure and weakened S to a certain extent. Despite this, the S values at higher rotation speeds were higher than those of Ref-0, M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e-0, and M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e-0, indicating that the rotation process was beneficial to the orderly alignments of rod-like CNC particles. This result supported that the CNC film generated by rotation exhibited more significant anisotropy, enabling nonreciprocal LD and LB to play a greater role in the chiroptical response.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Tunable chiroptical activity\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe self-assembly of particles in CNC suspension is a subtle process influenced by multiple factors such as ionic strength, drying conditions, pH, stimulation of the external field, and particle parameters (surface charge and chemistry, dimension, and aspect ratio).\u003csup\u003e[\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e]\u003c/sup\u003e Based on the abovementioned discussion regarding the chiroptical behavior, right-handed helical structure, and orientation of CNC thin films prepared by the REISA method, we further investigated the tunability and CPL feasibility of the chiroptical activity. Films with varying suspension masses (25℃), drying temperatures (9 g suspension for each film), ionic strengths (25℃, 15 g suspension for each film), and pH values (25℃, 9 g suspension for each film) were prepared by clockwise rotation at 100 rpm within the perpendicular magnetic field, and the corresponding results were presented in Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e and S10. The structural color, CP reflection, and CD signal of these films were thoroughly evaluated. An increase in the suspension mass thickened the CNC film, which was visually manifested as a blue shift in structural color (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ed). Regarding chiroptical activity, although no significant difference was noted between reflected L-CP and R-CP lights (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea), the average CD suggested that film thickness affected chiral structure to a certain extent (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb). An increase in the drying temperature also caused similar but smaller changes in these three dimensions. Based on CP reflection (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea) and structural color (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec), the effects caused by the slight increase in ionic strength were negligible. However, the addition of 2.5 g 0.01 M sodium chloride solution to 9 g CNC suspension formed a film with stronger L-CP light reflection (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea); moreover, this film showed no negative CD signals at longer wavelengths, which was completely contrasting to other films treated with less sodium chloride solution (\u003cb\u003eFigures S10\u003c/b\u003e and \u003cb\u003e7b\u003c/b\u003e). Lastly, the complicated pH regulation was divided into three categories according to the pH value. On the one hand, under suitable acidic or alkaline condition such as pH\u0026thinsp;=\u0026thinsp;3.0 or 11.5, respectively, retained inherent left-handed nematic structures and newly generated twisted right-handed helical bundles in CNC films were confirmed by positive average CD at short wavelengths and negative average CD at long wavelengths. These films were orange yellow and ambidextrously reflected CP light. On the other hand, under a stronger acidic or alkaline condition such as pH\u0026thinsp;=\u0026thinsp;1.8 or 11.8, respectively, the chirality property was deprived, and an almost transparent film was formed without the ability of reflection. Different from the previous two categories, the colorful films with pH\u0026thinsp;=\u0026thinsp;7 and 10.5 were light purple, particularly the former. It should be emphasized that negative average CD signals were not detected at long wavelengths, although the films exhibited negative apparent CD signals (\u003cb\u003eFigure S10\u003c/b\u003e). This observation was almost consistent with the stronger L-CP light reflection of the films. Among these four regulatory modes, the mechanisms underlying regulation by thickness and temperature remain a current research challenge. The mechanisms underlying regulation by ionic strength and pH involve the electrostatic effect, which plays a crucial role in the assembly of CNC particles. The varying ionic strength or system pH alters the electrostatic repulsion of CNC, forcing a shift in the balance of multiple forces. This results in the emergence of inconsistent assembly structures with different property features.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Nonreciprocal circularly polarized emission\u003c/h2\u003e \u003cp\u003eAn interesting finding was the emergence of a novel nonreciprocal CPL activity during pH regulation when CdTe QDs were doped into CNC films under rotation, although the film showed a low g\u003csub\u003elum\u003c/sub\u003e. In the context of the abovementioned results for regulating chiroptical activity, we considered pH regulation as a paradigm here to study the CPL feasibility of CdTe QDs-doped CNC films. Because CdTe QDs were stable only under alkaline conditions and the average CD detected from the film with pH 11.5 was significantly negative, the pH values of CdTe QDs-doped CNC suspensions (25℃, 9 g suspension for each film) were adjusted to 11.0, 11.2, and 11.5, and thin films were prepared by clockwise rotation at 100 rpm under the perpendicular magnetic field. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea, CdTe QDs-doped CNC films presented similar chiroptical properties, i.e., nonnegligible LDs and deviated and discrepant apparent CDs for the two sides; moreover, the three films exhibited clearly negative average CD signals. In particular, the positive CD signal of the thin film was very weak at pH 11.2. Additionally, L-CP and R-CP channels showed similar optical brightness when the films were observed by POM. Given the deviated apparent CDs, CPL spectra were recorded by rotating the film around the optical axis at 90\u0026deg; intervals from 0\u0026deg; to 270\u0026deg;, with four times testing for each side. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb, the film with pH 11.0 exhibited nonreciprocal CPL activity, as described in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec. When this CNC film was excited by UV light from side A, a negative CPL signal was detected, indicating a R-CP emitter. Conversely, a positive CPL signal was observed when the film was excited by UV light from side B, which manifested as a L-CP emitter. The nonreciprocal CPL activity was apparently tunable according to the pH value. For example, negative and positive CPL signals were detected at pH 11.2 although a deviation was noted in intensity and low g\u003csub\u003elum\u003c/sub\u003e, while the nonreciprocity property disappeared at pH 11.5, exhibiting a common and single R-CP emitter. The overlap between PBG and luminescent emission wavelength is the key factor for chiral materials to emit CP light.\u003csup\u003e[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e81\u003c/span\u003e]\u003c/sup\u003e Although the three films showed negative average CDs, the results were not the same for PBG; thus, different overlaps were noted between their PBGs and the luminescent emission wavelength of CdTe QDs. Consequently, different CPL characteristics were observed in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb. The aqueous solution of CdTe QDs showed an emission wavelength of approximately 705 nm, and the fluorescence emissions (PL) significantly shifted to 570\u0026thinsp;~\u0026thinsp;580 nm after these QDs were doped into CNC films (Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ed and \u003cb\u003ef\u003c/b\u003e). As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ee, the reflections of CdTe QDs-doped films occurred at 640\u0026thinsp;~\u0026thinsp;670 nm. Therefore, by combining the reflection, PL, and CPL spectra, we concluded that the CPL signal was mainly achieved through the circularly polarized selective reflection mechanism.\u003c/p\u003e \u003cp\u003eCP emission (known as apparent CPL) is another important chiroptical feature in thin films and has been widely investigated. However, because of the complexity of its underlying mechanisms, most of the studies present only the CPL phenomenon and potential applications; consequently, there are few theoretical models that can explicitly clarify the complicated nonreciprocal CPL behavior. Here, a reported model may provide valuable insights for interpreting the unprecedented nonreciprocal CPL activity. Similar to apparent CD, the apparent CPL included several contributions that can be \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:C{PL}_{obs}\\approx\\:{CPL}_{iso}+(f{\\prime\\:}\\cdot\\:LB-f\\cdot\\:LB{\\prime\\:})\\:\\)\u003c/span\u003e\u003c/span\u003e (4)\u003c/p\u003e \u003cp\u003ewhere CPL\u003csub\u003eobs\u003c/sub\u003e represents the apparent CPL directly observed through instrumental testing, CPL\u003csub\u003eiso\u003c/sub\u003e denotes the isotropic reciprocal component related only to intrinsic chirality at the molecular or higher scale, the second term (designated as fLB) affected by film alignment is the nonreciprocal contribution derived from macroscopically anisotropic interaction, and f and fʹ represent linear fluorescence anisotropy of the sample measured along the x-axis and y-axis and their bisectors, respectively. fLB shows inversion of its sign when the sample is flipped but remains constant when the film is rotated around the z-axis (optical axis). On the one hand, the results of 2D WAXS revealed that rotation amplified the anisotropy of CNC films, thus favoring the contribution of fLB to apparent CPL. On the other hand, both average CD and SEM indicated rotation-induced twisted right-handedness in CNC films. On the basis of these two points, we decomposed the apparent CPL of CNC films into four components according to Eq.\u0026nbsp;(4), i.e., negative CPL\u003csub\u003eiso\u003c/sub\u003e-N from the inherent left-handed nematic phase, positive CPL\u003csub\u003eiso\u003c/sub\u003e-P from the rotation-induced right-handed helix, and nonreciprocal fLB components (negative fLB-N for A side and positive fLB-P for B side) contributed by anisotropy. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec, \u0026ldquo;CPL\u003csub\u003eiso\u003c/sub\u003e-N\u0026thinsp;+\u0026thinsp;fLB-N\u0026rdquo; was larger than CPL\u003csub\u003eiso\u003c/sub\u003e-P when the CNC film was excited from side A, resulting in a negative CPL\u003csub\u003eobs\u003c/sub\u003e. When the CNC film was excited from side B, \u0026ldquo;CPL\u003csub\u003eiso\u003c/sub\u003e-P\u0026thinsp;+\u0026thinsp;fLB-P\u0026rdquo; was larger than CPL\u003csub\u003eiso\u003c/sub\u003e-N, leading to a positive CPL\u003csub\u003eobs\u003c/sub\u003e. Therefore, we considered that the anisotropic fLB contribution is dominant for this nonreciprocal CPL activity that enables left- and right-handed CP emissions from the two opposite surfaces of the same film. Compared to nonreciprocal CPL, apparent CD did not exhibit nonreciprocal characteristics. According to equations (\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) and (4), both apparent CD and CPL include isotropic and anisotropic components. But small anisotropic contribution cannot inverse the sign of apparent CD, resulting in the absence of nonreciprocal features.\u003c/p\u003e \u003cp\u003eRapidly growing interest in chiroptical materials has facilitated in-depth studies on reciprocal CP absorption and emission; in contrast, the nonreciprocal categories, particularly nonreciprocal CP emission, has been rarely studied. Developing a new type of a chiral functional material by harnessing only one enantiomer to obtain opposite chiroptical properties from the two opposite surfaces of the same film is not only of fundamental scientific interest, but also provides an exciting opportunity for broadening the scope of implications of CP absorbance and emission systems. The first case of such nonreciprocal chiroptical properties was reported by Deng et al. in 2019, where the authors developed a composite film comprising an achiral luminophore interlayer and two surfaces with opposite chiral helicity.\u003csup\u003e[\u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e82\u003c/span\u003e]\u003c/sup\u003e In 2020, Lorenzo et al. reported another interesting discovery, i.e., an organic thin film that displays almost enantiomer-like CD and CPL from its front and back surfaces, respectively.\u003csup\u003e[\u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e83\u003c/span\u003e]\u003c/sup\u003e In the present study, we achieved a similar unexpected chiroptical feature, i.e., nonreciprocal CPL, by using natural and sustainable CNC-based films. For advanced CNC-based materials that require an opposite chiroptical response, this feature not only simplifies the manufacturing procedure and reduces the overall cost by avoiding complex integration of materials with different handedness, but it is also a valuable breaking of CP emission reciprocity that inverts the CP light handedness following reversal of the emitted light wavevector.\u003csup\u003e[\u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e83\u003c/span\u003e, \u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e84\u003c/span\u003e]\u003c/sup\u003e Although this emergent nonreciprocal CPL-active material is still in its infancy, it has enormous potential for application in advancing next-generation of chiral electronics and photonics, for example, in the development of CP organic field-effect transistor (CP-OFET) that can differentiate the illumination direction and in the revolutionary innovation of highly efficient CP organic light-emitting diode (CP-OLED) with an increased output of CP from the device.\u003csup\u003e[\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e, \u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e83\u003c/span\u003e, \u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e84\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Conclusion","content":"\u003cp\u003eMysterious chirality at different hierarchy scales exists widely in nature and has attracted increasing interest of researchers worldwide. CP absorption and emission, the two major components of chiroptics, are commonly known as apparent CD and CPL, respectively. Although reciprocal behaviors of both apparent CD and CPL are widely known, there is limited information on the nonreciprocal categories, particularly nonreciprocal CP emission. CNC, a natural, sustainable, and renewable material, is a highly promising building block for chiral photonic crystals; however, the right-handedness of CNC-based materials remains a challenge to be addressed. Here, we developed a rotation-induced dynamic assembly strategy that enables rod-like CNC particles to assemble into a twisted right-handed helix bundle in solid iridescent CNC films. These films can ambidextrously reflect left- and right-handed CP light because of the coexistence of the newly emerged right-handed helix bundle and the inherent left-handed helical nematic phase. The right-handedness was closely dependent on the rotation rate rather than on the rotation direction; moreover, it occurred only at the outer areas of the CNC film, whereas the center of the film retained the features of the left-handed helical nematic phase. With the increase in the rotation speed, the λ\u003csub\u003emax\u003c/sub\u003e value of the CNC film first decreased and then increased, and this value was larger when the CNC suspension was rotated anticlockwise. An increase in Hermann order parameter S revealed that the rotation process also enhanced the macroscopic anisotropy of the CNC film, causing nonnegligible contribution to apparent CD and CPL. These CNC films with right-handed helices exhibited a Janus chiroptical activity, i.e., anisotropic CP absorption and emission, on two opposite surfaces. The Janus chiroptical activity was tunable by controlling the mass, drying temperature, ionic strength, and pH of the CNC suspension. It should also be noted that CdTe QDs-doped CNC films exhibited a rare phenomenon of nonreciprocal CPL regulated by pH for the first time in CNC materials. In other words, CdTe QDs-doped CNC films could emit opposite CP light from their two opposite surfaces, without the requirement for the complex integration of materials with different handedness. Thus, the emergent nonreciprocal CPL broke the reciprocity in CP emission and opened new avenues to develop novel chiral functional materials by harnessing only one enantiomer to obtain opposite chiroptical properties in the same film; this feature is highly desired in developing next-generation chiral electronics and photonics such as CP-OFET for differentiating the illumination direction and efficient CP-OLED with an increased CP degree output.\u003c/p\u003e"},{"header":"4. Experimental Section","content":"\u003cp\u003e \u003cb\u003eMaterials\u003c/b\u003e. Polyethylene glycol (PEG, Mn\u0026thinsp;=\u0026thinsp;20000) and sodium hydroxide solution (0.5 M) were purchased from Aladdin Biochemical Technology Co., Ltd (Shanghai, China). Water-soluble CdTe QDs with a solid content of approximately 4 mg∙mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e were supplied by Beida Jubang Science and Technology Co., Ltd (Beijing, China). The QDs were decorated with the carboxyl group and showed an emission wavelength of 705 nm. Sodium chloride solution (0.01 M) was provided by Shanghai Meryer Biochemical Technology Co., Ltd (Shanghai, China). Approximately 2.2wt% CNC suspension was prepared as reported previously.\u003csup\u003e[\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e]\u003c/sup\u003e Industrial neodymium magnets (NdFeB magnets) with the size of 60 mm \u0026times; 60 mm \u0026times; 30 mm were used for inducing the local magnetic field. One NdFeB magnet had a 9-mm-diameter hole in the center along the thickness direction to induce a perpendicular magnetic field.\u003c/p\u003e \u003cp\u003e \u003cb\u003ePreparation of CNC films\u003c/b\u003e. An appropriate amount of CNC suspension was completely mixed with the PEG solution (2wt%) in the mass ratio of 15:1. The mixed suspension was then added to a Petri dish (56 mm diameter) fixed on a rotary platform, which was driven by a tunable pulse signal. As illustrated in \u003cb\u003eFigure S2b\u003c/b\u003e, two NdFeB magnets were placed on the left and right (or upper and lower) sides of the Petri dish for inducing a parallel or perpendicular magnetic field. The suspension was then rotated at the desired rotation rate and direction under ambient humidity and controlled temperature until it dried into a film. Samples were defined as M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e-Ax, M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e-Cx, M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e-Ax, and M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e-Cx, where M\u003csub\u003e\u003cb\u003e∥\u003c/b\u003e\u003c/sub\u003e and M\u003csub\u003e\u003cb\u003e\u0026perp;\u003c/b\u003e\u003c/sub\u003e represent parallel and perpendicular magnetic fields; A and C denote anticlockwise and clockwise rotation, respectively; and x represents the rotation rate (rpm). A and C were omitted when x\u0026thinsp;=\u0026thinsp;0 rpm (without rotation). Ref-0 and Ref-C80 were used as two references without the application of the magnetic field. Sodium hydroxide and sodium chloride solutions were used to adjust the pH and ionic strength of the mixed suspension, respectively.\u003c/p\u003e \u003cp\u003e \u003cb\u003eCharacterization\u003c/b\u003e. Nano-size and electric potential of the diluted CNC suspension were measured with a particle size and zeta potential analyzer (Omni, Brookhaven Instruments, USA) at 25\u0026deg;C. An atomic force microscope (MFP-3D, Oxford Instruments, USA) was used to observe the morphology of the diluted rod-like CNC particles on a pristine mica sheet. Sulfur content of dried CNC was determined by an elemental analyzer (Vario EL Cube, Element Corporation, Germany). A UV/Vis/NIR spectrometer (Lambda 750S, PerkinElmer, USA) was used for measuring reflectivity in the visible light range; additionally, a left- or right-handed CP filter was inserted into the light path to illuminate L-CP or R-CP light on the film surface. Polarized optical images (POMs) were captured on a Zeiss microscope (Axiolab 5) in the reflection mode as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb. An inverted L-CP or R-CP filter was used to allow the reflected light from the film to travel through for distinguishing L-CP or R-CP light. CD spectra of CNC films were measured with the Jasco Model J-1500 spectrometer (Japan) from 820 to 200 nm at 1 nm data pitch and 200 nm∙min\u003csup\u003e-1\u003c/sup\u003e rate. The CPL spectra from 800 to 450 nm were acquired on a Jasco CPL-300 spectrometer (Japan) with an excitation wavelength of 365 nm, data pitch of 0.5 nm, and a scanning rate of 500 nm∙min\u003csup\u003e-1\u003c/sup\u003e. The RISE-MAGNA scanning electron microscope (TESCAN, Czech Republic) was used for capturing SEM images at 3 keV accelerating voltage and 30 pA current. Samples for viewing were prepared by peeling along the surface (or fracturing) and sputter coating the target surface with gold-palladium.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eSupporting Information\u003c/h2\u003e \u003cp\u003eSupporting Information is available from the author.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThis work was financially supported by Interdisciplinary Program of Shanghai Jiao Tong University (YG2022QN085).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eYang, X., et al., \u003cem\u003eRecent Progress of Circularly Polarized Luminescence Materials from Chinese Perspectives.\u003c/em\u003e CCS Chemistry, 2023. \u003cstrong\u003e5\u003c/strong\u003e(12): p. 2760-2789.\u003c/li\u003e\n \u003cli\u003eZheng, S. and G. 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Pan, and J. 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Moreover, circularly polarized (CP) absorption and emission, which are the essential components of chiral optics, have received considerable interest from researchers. However, very few studies have been conducted on materials with nonreciprocal CP emission that emit CP light with opposite handedness from their two opposite surfaces. Here, we present a novel nonreciprocal CP emission film developed from cellulose nanocrystalline (CNC). A sustainable CNC film with twisted right-handedness opposite to its inherent left-handed nematic structure is developed by a rotation-induced dynamic self-assembly strategy; this film not only ambidextrously reflects left- and right-handed CP light but also clearly exhibits a tunable Janus chiroptical activity, i.e., anisotropic CP absorption and emission, on its opposite surfaces. Both orientation factor and reflected wavelength with maximum reflectivity of the CNC film significantly depend on the rotation rate and direction. In particular, the CNC film for the first time shows a unique feature of nonreciprocal CP luminescence (CPL) achieved through pH-regulated doping of cadmium telluride quantum dots. This rare nonreciprocal CPL phenomenon has broken through the reciprocity in CP emission and is highly desired in next-generation chiral electronics and photonics because of their immense potential.\u003c/p\u003e","manuscriptTitle":"Emergent Nonreciprocal Dual Circularly Polarized Luminescence from an Iridescent Cellulose Nanocrystalline Film","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-13 05:33:18","doi":"10.21203/rs.3.rs-6164168/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"6f20ce4e-3b87-49aa-a798-87ba798d4e4b","owner":[],"postedDate":"March 13th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":45614681,"name":"Physical sciences/Optics and photonics/Optical materials and structures/Photonic crystals"},{"id":45614682,"name":"Physical sciences/Materials science/Materials for optics/Photonic crystals"},{"id":45614683,"name":"Physical sciences/Nanoscience and technology/Nanoscale materials/Structural properties"}],"tags":[],"updatedAt":"2025-05-02T15:11:49+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-13 05:33:18","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6164168","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6164168","identity":"rs-6164168","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}