Eco-friendly and Biocompatible Gelatin Plasmonic Filters for UV-Vis-NIR Light

Eco-friendly and Biocompatible Gelatin Plasmonic Filters for UV-Vis-NIR Light | 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 Eco-friendly and Biocompatible Gelatin Plasmonic Filters for UV-Vis-NIR Light Ramon Alvarez-Puebla, Irving Brian Becerril Castro, Yoel Negrin Montecelo, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3911708/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 25 May, 2024 Read the published version in Communications Chemistry → Version 1 posted You are reading this latest preprint version Abstract In this work, we present the development of light filters using a gelatin-based nanocomposite. Owing to the plasmonic properties of metallic nanoparticles (NPs), these filters can be customized across the UV-Visible-NIR spectrum. Additionally, the filters are designed for modular use, allowing for the addition or removal of desired spectral ranges. The nanocomposites are composed of biodegradable and biocompatible materials. These plasmonic gelatin-based filters block light due to the Localized Surface Plasmon Resonance (LSPR) of the NPs and can be tailored to meet various requirements, akin to a diner selecting options from a menu. This approach is inspired by culinary techniques, and we anticipate it will stimulate further exploration of biomaterials for applications in optics, materials science, electronics, and more. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction The increasing consumer demand for environmentally-friendly products has shifted research efforts toward the development of eco-friendly materials and sustainable processes. Among these new materials, nanocomposites that incorporate biopolymers occupy a prominent position, primarily because biopolymers are naturally occurring in living organisms and are presumed to be biodegradable and biocompatible. Interestingly, the use of biopolymers is also prevalent in the food industry. For instance, plant-based guar gum and bacteria-derived xanthan gum are biopolymers commonly used as thickening and stabilizing agents. 1–3 However, gelatin holds a unique place among the biopolymers used in cooking. Gelatin is a protein-based substance derived through the hydrolysis of animal connective tissues. It is highly soluble in water and is also considered nutritious due to its high protein content (85–92%), containing all essential amino acids except for tryptophan, and its low caloric value. 4 Additionally, its unique melt-in-the-mouth property, due to the formation of thermally reversible gels with a gel-melting point below body temperature (< 35°C), is highly prized for making gel desserts. 5 As it is edible, gelatin capsules and microcapsules are commonly found in pharmaceuticals. 4 Nanocomposites with gelatin include works with carbon nanotubes 6 and copper nanoparticles (NPs) 7 to create conductive materials. Nonetheless, the development of gelatin-based nanocomposites for photonics and optics has not been extensively studied. 8 In this work, we explore an intriguing application for optical uses: the design and fabrication of gelatin-based nanocomposites for light filters. To impart optical properties to a traditionally transparent material, 9 we incorporated a variety of metallic NPs into the polymeric matrix, providing mechanical support. Due to their size, metallic NPs can sustain localized surface plasmon resonance (LSPR), enabling light manipulation (entrapment) at the nanoscale. By varying the physical characteristics of the NPs, such as material, size, and geometry, it is possible to finely tune their optical properties across the electromagnetic spectrum. The inclusion of NPs allows us to work within the UV-Visible-NIR range with high control over the optical filtering properties of the nanocomposites. These plasmonic gelatin-based light filters exhibit modular behavior, allowing them to be used in combination to add or remove the desired spectral range of interest, while being composed of sustainable and ecological materials. Our work presents an alternative approach to the production of light filters that meets requirements in a manner comparable to selecting options from a restaurant menu. Results and discussion To create plasmonic gelatin-based light filters, we alter the inherent optical properties of plain gelatin by dispersing plasmonic nanoparticles (NPs). Combining the optical transparency of gelatin with the absorption capabilities of metallic NPs, we hypothesized that achieving the desired filtering effect was contingent on preventing NP agglomeration, which could otherwise obscure the distinct localized surface plasmon resonances (LSPRs) of the NPs. Accordingly, we devised and adhered to the procedure outlined in Fig. 1 . Initially, five types of NPs were chosen and synthesized using established methods: silver nanospheres (AgNPs), gold nanospheres (AuNPs), and gold nanorods (AuNRs) with three varying aspect ratios. Subsequently, these NPs were amalgamated with pre-dissolved gelatin to create a NP@biopolymer solution, which was then cast in petri dishes. Post-casting, the molds were refrigerated at 4°C for 48 hours to ensure solidification (gelation). Once set, the nanocomposites were exposed to air for drying. Finally, the dry material was carefully extracted using tweezers. The chosen set of NPs demonstrated robust absorption across the UV-Vis-NIR spectrum due to LSPR, as evidenced by the absorption spectra in Fig. 2 A. Plasmon resonances were identified at 405 nm for AgNPs, 537 nm for AuNPs, and at 730, 920, and 1050 nm for AuNRs. This extensive absorption range underscores the ability to adjust the optical properties of NPs. Representative Transmission TEM images for each NP type are displayed in Figs. 2 B-F. The average sizes were 51 ± 13 nm for AgNPs and 61 ± 2 nm for AuNPs. Meanwhile, the lengths of AuNRs were 69 ± 6, 51 ± 4, and 50 ± 12 nm, correlating with increasing aspect ratios (AR) of 3.1, 5.2, and 6.5 for AuNRs730, AuNRs920, and AuNRs1050, respectively. Notably, while all NPs had comparable sizes, their geometry and composition markedly influenced their optical responses. Specifically, the AR of AuNRs facilitated controlled responses in the Vis-NIR region, 10 while the AgNPs’ LSPR bordered the visible and UVA regions. 11 Direct addition of dry biopolymer (laminates) to the NP colloid resulted in NP aggregation. Therefore, the biopolymer was first hydrated (10 min in cold water), then dissolved (at 35°C), and finally combined with a predetermined volume of NPs. To calculate the necessary NP volume, we assumed a linear relationship between the NPs' absorption and the optical path length. Using a standard petri dish as a mold (diameter = 9 cm) and targeting a final concentration of 2% biopolymer in a 15 ml volume for an easily detachable nanocomposite, we employed the expression: where A is the desired maximum absorption. After determining the NP volume, water was added to achieve a final 9 ml volume, which was then mixed with a 6 ml aliquot of 5% gelatin. The resultant liquid NP@biopolymer solution was cast in the mold and refrigerated to form hydrated gelatinized nanocomposites. Any present bubbles were removed while the mixture was still liquid to ensure material uniformity. We examined the formation of hydrated gelatinized nanocomposites by preparing and analyzing five samples with varying concentrations of AgNPs using UV-Vis-NIR spectroscopy (Fig. 3 ). A pronounced absorption at 410 nm, attributed to the AgNPs, was observed. The 5 nm redshift aligns with the expected change in the dielectric constant due to the biopolymer. Absorption from 1320 nm onward was attributed to the material's water content. Notably, refrigeration was essential for gelation of the NP@biopolymer, distinct from pure gelatin. Without this step, the final filters were inhomogeneous. Correlating the absorbance of the liquid (0.4, 0.8, 1.2, and 1.6) before gelation with the experimental transmittance of the hydrated NP@biopolymer (at 410 nm) indicated good agreement with the predicted transmittance, suggesting that the gelation process does not cause NP aggregation but instead immobilizes their position within the biopolymer matrix. The subsequent drying process aimed to eliminate water's impact on the nanocomposite's transmittance and enhance its mechanical properties. Figure 4 A illustrates that the absorption starting from 1320 nm, visible in Fig. 3 , is nearly removed in all samples post-drying. Although the final transmittance still aligns with theoretical predictions, a broadening of the absorption peak and a decrease in maximum transmittance (89%) are observed. These changes suggest that the AgNPs draw closer as the water content diminishes, forming occasional interactions and thus reducing the maximum absorption by the NPs, which is compensated by the biopolymer's absorption. However, a distinct absorption band due to the NPs remains. The highest absorption occurs between 436–438 nm, which is redshifted compared to the hydrated material and the original colloidal particles. This finding aligns with the increased dielectric medium of the material: n = 1.536 for pure gelatin at 632.8 nm. 9 The shiny appearance and uniform color of the filters with high absorption (> 50%) over a white background are shown in Fig. 4 B. The filters are thin, flexible layers but are prone to tearing. SEM characterization (Fig. 4 C) revealed uniform thickness (33.4 µm) and a distinctive layer pattern on the surface, likely imprinted by the mold. Backscattered electron imaging confirmed even particle distribution within the material. Having established the methodology for light filters with AgNPs, we extended our process to include all previously selected NPs (i.e., AuNPs, AuNRs730, AuNRs920, and AuNRs1050) for filters with approximately 60% transmittance. This transmittance level was chosen as a balance between absorption efficiency and ease of preparation. The UV-Vis-NIR spectra of these nanocomposites (Fig. 5 A) indicate that the gelation process also prevents aggregation of the AuNPs and AuNRs. However, the drying process differed from that for AgNPs: an increase (~ 10%) in final absorbance was observed (Fig. 5 B). This increase, previously attributed to gelatin, was overshadowed by interparticle interactions in AgNP filters. In AuNP and AuNR filters, this interparticle interaction compensation seems absent. This hypothesis is supported by a smaller broadening of the AuNPs absorption peak compared with the AgNPs. One explanation is that the AuNPs and AuNRs have CTAC and CTAB stabilizing layers, respectively, that attach to the metal surface with an amine group. Thus, compared to the easily displaced citrate on AgNPs, the AuNPs and AuNRs are less bound to the biopolymer during drying and tend to arrange apart from other NPs. The final appearance of the filters is shown in Fig. 5 C, alongside a filter with AgNPs for comparison. A small image with letters resembling a “tumbling E” chart is placed behind the filter to demonstrate the material's transparency. These results show that gelatin-based filters can be tuned within the UV-Vis-NIR spectrum using the employed NPs' LSPR. Therefore, this procedure can be expanded to other morphologies or materials with a desired absorption spectrum. The gelatin provides a transparent canvas that can be exploited as desired. The process for obtaining biopolymer-based light filters is not limited to selecting constituent NPs but can also be designed through arrangements of filters. This approach is demonstrated using the presented filters to create two commonly used filter configurations: a bandpass filter and a notch filter. In the first example (Fig. 6 A), individual AgNPs and AuNRs1050 filters were stacked. This configuration restricts passing wavelengths within the range of 550 to 1010 nm, effectively acting as a band filter. The optical image over a pseudo-tumbling E chart allows visual inspection of the material, as most of the optical range is permitted to pass through. A different filter arrangement utilizes AuNRs730 and AuNRs1050 filters (Fig. 6 B), reducing NIR range wavelengths from 730 to 1085 nm, hence predominantly acting as a notch filter. These basic examples of filter configurations aim to demonstrate the modularity of the filters and their potential for integration into existing systems that could benefit from the broad spectral range and simple fabrication process. The presented gelatin-based filters primarily reduce incident light through absorption by the NPs. However, this method of light filtering is not always ideal. For example, IR filters used in buildings or automobiles to reduce energy consumption during summer prefer to reflect rather than absorb IR radiation. 12 This preference stems from the fact that a window absorbing IR radiation would act as a heater, despite preventing heat transfer by radiation. Therefore, we investigated whether the light not transmitted by our filters is entirely absorbed. To do this, we measured the total and diffuse reflectance of the filter surface with AuNPs, and from these, we estimated the specular reflection, as shown in Fig. 7 A. The total reflection accounted for an average of 7% of the untransmitted light (400-2500nm), with the maximum in diffuse reflection redshifted from the maximum absorption. Plotting the normalized transmittance and diffuse reflection (Fig. 7 B) highlights this shift (25nm), which can be explained in terms of the calculated cross-sections of the far field. We employed the boundary element theory 13 in the MNPBEM 14 implementation in MATLAB to distinguish the absorption and scattering contributions to the total extinction (Fig. 7 C), revealing an 11 nm redshift between them. This suggests that the dominant component of the diffusely reflected light can be attributed to scattering by the AuNPs. Although this contribution is minimal, it demonstrates that the NPs in the filters can manipulate incident light through absorption or scattering. This opens the possibility of creating filters that reflect light instead of absorbing it by changing the constituent NPs. Conclusions In this research, we have successfully pioneered the development and implementation of innovative gelatin-based light filters using metallic nanoparticles (NPs), an endeavor inspired by the culinary utilization of biopolymers. This groundbreaking approach is expected to catalyze further research and exploration into the application of biomaterials across various sectors, including optics, materials science, electronics, and potentially beyond. Embracing the current environmental ethos, these optical filters are fashioned from biocompatible and eco-friendly materials, epitomizing the shift towards green and sustainable material research. The filters' adaptability across the UV-Visible-NIR electromagnetic spectrum is a significant achievement, allowing for precise customization and functionality. Moreover, their modular nature facilitates easy integration into existing technological and scientific apparatus, enhancing their utility and applicability. The fabrication process of these filters is notably straightforward and cost-effective, eliminating the need for elaborate or high-cost equipment. This simplicity in production paves the way for widespread adoption and experimentation in both academic and industrial settings, potentially leading to novel applications and advancements in the field of material science and photonics.. Methods Materials . Tetrachloroauric acid (HAuCl 4 ·3H 2 O), hexadecyltrimethylammonium bromide 99% (CTAB), cetyltrimethylammonium chloride solution 0.78 M, sodium borohydride 99% (NaBH 4 ), silver nitrate (AgNO 3 ), hydrochloric acid 37% (HCl), Hydroquinone 99% (HQ), L-ascorbic acid 99% (AA) and tri-sodium citrate dihydrate 99.5% (Na 3 Cit) were purchased from Thermo Fisher Scientific. Milli-Q water (18.2 MΩ) was used in all preparations. Commercial gelatine was purchased from Neutral gelatine was purchased from Ewald-Gelatine. Characterization . TEM images were collected from a JEOL 1010 and 1011. Samples were prepared on carbon-Formvar-coated 200 mesh copper grids. SEM samples were imaged with a JEOL JSM-6700f. UV-VIS spectroscopy was performed in a Jasco V-770. Synthesis of AgNPs. AgNPs were synthesized using a modified version of a previously reported protocol. 15 Briefly, a AgNO 3 solution (100 ml, 1 mM) was heated to boiling point. Then 2 ml of Na 3 Cit (2 ml, 34 mM) was rapidly injected into the boiling solution an let under vigorous stirring for 45 minutes. Finally, the solution was left to cool at room temperature. Synthesis of AuNPs with uniform diameters. Smooth AuNPs with 43 nm of diameter were synthesized by a modification of the seed-mediated growth protocol. 16 Firstly, AuNPs with 10 nm of diameter were grown by addition of 2 ml of HAuCl 4 solution (5 × 10 − 4 M) using a syringe pump with injection rate of 2 ml/h in a solution containing 2 ml of CTAC 0.2 M, 1.5 ml of AA (0.1 M) and 50 µl of the initial seeds. After that, 2 ml of HAuCl 4 solution (5 × 10 − 4 M) were injected (with injection rate of 2 ml/h) in a second growth solution containing 2 ml of CTAC 0.1 M, 13 µl of AA 0.1 M and 10 µl of the 10 nm seeds. Synthesis of AuNRs . AuNRs were prepared by the seed-mediated growth method following two protocols previously described. 17,18 In order to tune the longitudinal LSPR some modifications have been made in the addition of AgNO 3 and seeds solutions in the growth process. Preparation of the initial, CTAB-Capped Au clusters (seeds). A fresh aqueous NaBH 4 solution (0.3 ml, 0.01 M) was rapidly added into a 4.7 ml of an aqueous solution containing HAuCl 4 (2.5 × 10 − 4 M) and CTAB (0.1 M). The mixture was stirred a speed of 1000 rpm for 2 min, and then kept undisturbed at 27°C for 3 h to ensure complete decomposition of the NaBH 4 . AuNRs with LSPR centered at 730 nm and 920 nm. AuNRs with LSPR centered at 730 nm and 920 nm, respectively, were synthesized by a modification of the seed-mediated growth protocol described by Scarabelli et all. 2 For 10 ml of solution with final concentration of HAuCl 4 and CTAB fixed at 5 × 10 − 4 M and 0.1 M, respectively, we used 20 µl of the Au-seeds in the growth solution (for AuNR with LSPR at 730 nm) and 32 µl of the Au-seeds (for AuNR with LSPR at 920 nm). AuNRs with LSPR = 1050 nm. AuNRs with LSPR centered at 1090 nm were synthesized by a modification of the seed-mediated growth protocol described by Vigderman et all. 1 For a typical 10 ml of solution with final concentration of HAuCl 4 and CTAB fixed at 5 × 10 − 4 M and 0.1 M, respectively, we used 0.4 ml of seeds and 0.5 ml of HQ. In the last step AuNPs and AuNRs were collected by centrifugation at 6000 rpm for 40 min, and then washed two times and redispersed in water for characterization. Plasmonic galatine-based light filters. The nanocomposites were obtained through the dispersion of plasmonic NPs on a gelatin matrix. To do this a certain amount of gelatin was hydrated in cold water for 10 minutes and then dissolved in water at 35°C. Then was mixed with colloidal NPs to obtain a solution with final concentration of 2% (w/v) gelatine and the desired NPs concentration (Eq. 1 ). After that, the plasmonic sol was transferred to petri dishes and kept at 4°C for 48h in a fridge. To dry the material, the petri dishes were left in an open atmosphere for 7 days. To detach the filters, they were pulled out with tweezers while deforming the mold. Numerical cross section calculations. Using the MNPBEM 14 tool box, we place a AuNP with diameter of 51 nm in an ideal dielectric media (n = 1.536). 8 The NP was modeled as a “trisphere” object with 484 vertex. For the dielectric constant of gold we used experimental data previously reported. 19 Data availability The authors declare that all relevant data supporting the findings of this study are available within the paper. Declarations Acknowledgements This work was supported by the projects PID2020-120306RB-I00 PID2020-113704RB-I00/AEI/10.13039/501100011033; TED2021-132101B-I00, PDC2021-121787-I00 funded by MCIN/AEI/10.13039/501100011033 and European Union “NextGenerationEU”/PRTR; Xunta de Galicia ED431C 2022/24; 2020SGR00166 (funded by Generalitat de Cataluña), 2021PFR-URV-B2-02 (funded by Universitat Rovira i Virgili), and HORIZON-EIC-2022-PATHFINDERCHALLENGES-01-06, HORIZON-HLTH-2022-DISEASE-06-TWO-STAGE, GA. No. 857543 and ENSEMBLE3 – Centre of Excellence for nanophotonics, advanced materials and novel crystal growth-based technologies” project (GA No. MAB/2020/14) of the European Union Horizon 2020 Research and Innovation Program. Author contributions IBBC, JM and YNM designed, performed, and analyzed experiments. IBBC and R.A.A.P wrote the manuscript. JM, IBBC and R.A.A.P conceptual idea. M.A.C.D, V.G. and R.A.A.P obtained the funding, analyzed data and supervised the work. Competing interests The authors declare no competing interests. References Mortensen, A. et al. Re‐evaluation of xanthan gum (E 415) as a food additive. EFSA Journal 15 , doi:10.2903/j.efsa.2017.4909 (2017). Mudgil, D., Barak, S. & Khatkar, B. S. Guar gum: processing, properties and food applications—A Review. Journal of Food Science and Technology 51 , 409-418, doi:10.1007/s13197-011-0522-x (2014). Habibi, H. & Khosravi-Darani, K. Effective variables on production and structure of xanthan gum and its food applications: A review. Biocatalysis and Agricultural Biotechnology 10 , 130-140, doi:10.1016/j.bcab.2017.02.013 (2017). Schrieber, R. & Gareis, H. Gelatine handbook: theory and industrial practice . (John Wiley & Sons, 2007). Stevens, P. in Food Stabilisers, Thickeners and Gelling Agents (ed Alan Imeson) 116-144 (2009). Meiyazhagan, A., Thangavel, S., Daniel P, H., Pulickel M, A. & Palanisamy, T. Electrically conducting nanobiocomposites using carbon nanotubes and collagen waste fibers. Materials Chemistry and Physics 157 , 8-15, doi:10.1016/j.matchemphys.2015.03.005 (2015). Cheirmadurai, K., Biswas, S., Murali, R. & Thanikaivelan, P. Green synthesis of copper nanoparticles and conducting nanobiocomposites using plant and animal sources. RSC Advances 4 , 19507, doi:10.1039/c4ra01414f (2014). Colusso, E. & Martucci, A. An overview of biopolymer-based nanocomposites for optics and electronics. Journal of Materials Chemistry C 9 , 5578-5593, doi:10.1039/d1tc00607j (2021). Manocchi, A. K., Domachuk, P., Omenetto, F. G. & Yi, H. Facile fabrication of gelatin-based biopolymeric optical waveguides. Biotechnology and Bioengineering 103 , 725-732, doi:10.1002/bit.22306 (2009). Chang, H.-H. & Murphy, C. J. Mini Gold Nanorods with Tunable Plasmonic Peaks beyond 1000 nm. Chemistry of Materials 30 , 1427-1435, doi:10.1021/acs.chemmater.7b05310 (2018). Bastús, N. G., Merkoçi, F., Piella, J. & Puntes, V. Synthesis of Highly Monodisperse Citrate-Stabilized Silver Nanoparticles of up to 200 nm: Kinetic Control and Catalytic Properties. Chemistry of Materials 26 , 2836-2846, doi:10.1021/cm500316k (2014). Butt, M. et al. Infrared reflective coatings for building and automobile glass windows for heat protection . Vol. 10342 OTT (SPIE, 2017). García De Abajo, F. J. & Howie, A. Retarded field calculation of electron energy loss in inhomogeneous dielectrics. Physical Review B 65 , doi:10.1103/physrevb.65.115418 (2002). Hohenester, U. & Trügler, A. MNPBEM – A Matlab toolbox for the simulation of plasmonic nanoparticles. Computer Physics Communications 183 , 370-381, doi:10.1016/j.cpc.2011.09.009 (2012). Lee, P. C. & Meisel, D. Adsorption and surface-enhanced Raman of dyes on silver and gold sols. The Journal of Physical Chemistry 86 , 3391-3395, doi:10.1021/j100214a025 (1982). Zheng, Y., Zhong, X., Li, Z. & Xia, Y. Successive, Seed‐Mediated Growth for the Synthesis of Single‐Crystal Gold Nanospheres with Uniform Diameters Controlled in the Range of 5–150 nm. Particle & Particle Systems Characterization 31 , 266-273, doi:10.1002/ppsc.201300256 (2014). Scarabelli, L., Sánchez-Iglesias, A., Pérez-Juste, J. & Liz-Marzán, L. M. A “Tips and Tricks” Practical Guide to the Synthesis of Gold Nanorods. The Journal of Physical Chemistry Letters 6 , 4270-4279, doi:10.1021/acs.jpclett.5b02123 (2015). Vigderman, L. & Zubarev, E. R. High-Yield Synthesis of Gold Nanorods with Longitudinal SPR Peak Greater than 1200 nm Using Hydroquinone as a Reducing Agent. Chemistry of Materials 25 , 1450-1457, doi:10.1021/cm303661d (2013). Johnson, P. B. & Christy, R. W. Optical Constants of the Noble Metals. Physical Review B 6 , 4370-4379, doi:10.1103/PhysRevB.6.4370 (1972). Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Published Journal Publication published 25 May, 2024 Read the published version in Communications Chemistry → 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-3911708","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":270718283,"identity":"4a495c66-4314-49ee-94aa-35e7c40d8b09","order_by":0,"name":"Ramon Alvarez-Puebla","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3ElEQVRIiWNgGAWjYBADGQhVQYIWHgh1Bso9QLQWxjYitJi3n058XMBgx2Nw/OzDhz/nHc43OMD88PMHPFpkzuRuNp7BkMxjcCbd2EBy22HLDQfYjCXw2SLBkLtNmoeBmUeyIY1NwnDbYQPJBh4G/Fr434K01PNI9j9j/5E4B6yF+QdeLRJgWw7z8EuksTEcbDhswM/Aw4bfFom3m42BfgdqecYs2XAs3YCfmc3M4gw+Lfy5Gx/zVFTLsfGnMX78UWNtwMbe/PgG4Sg1QOYwE1Q+CkbBKBgFo4AQAADO80CZovoOMwAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0003-4770-5756","institution":"Universitat Rovira i Virgili","correspondingAuthor":true,"prefix":"","firstName":"Ramon","middleName":"","lastName":"Alvarez-Puebla","suffix":""},{"id":270718284,"identity":"a2b618b6-745c-4c48-94ff-02099cbb3c08","order_by":1,"name":"Irving Brian Becerril Castro","email":"","orcid":"https://orcid.org/0000-0001-9184-8055","institution":"Universitat Rovira i Virgili","correspondingAuthor":false,"prefix":"","firstName":"Irving","middleName":"Brian Becerril","lastName":"Castro","suffix":""},{"id":270718285,"identity":"7f1850b6-4289-40b9-b3dd-f22e3939baa6","order_by":2,"name":"Yoel Negrin Montecelo","email":"","orcid":"","institution":"Universitat Rovira i Virgili","correspondingAuthor":false,"prefix":"","firstName":"Yoel","middleName":"Negrin","lastName":"Montecelo","suffix":""},{"id":270718286,"identity":"7fff8f6e-1f54-46f2-ae6f-75fedc3fb727","order_by":3,"name":"Josep Moreno","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Josep","middleName":"","lastName":"Moreno","suffix":""},{"id":270718287,"identity":"3b92ddc8-20a0-4452-83b2-080ae4c71ae3","order_by":4,"name":"Vincenzo Giannini","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Vincenzo","middleName":"","lastName":"Giannini","suffix":""},{"id":270718288,"identity":"d2c76704-611e-4344-a3ca-60eeea214bc5","order_by":5,"name":"Miguel A. Correa-Duarte","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Miguel","middleName":"A.","lastName":"Correa-Duarte","suffix":""}],"badges":[],"createdAt":"2024-01-30 20:47:05","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3911708/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3911708/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s42004-024-01202-6","type":"published","date":"2024-05-25T04:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":50642607,"identity":"f747ec97-f34a-44e0-b1ea-47c719f8e27b","added_by":"auto","created_at":"2024-02-05 06:21:01","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":175400,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic procedure to obtain plasmonic gelatine-based light filters.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-3911708/v1/7797fa4dfee17cabb1676ff4.png"},{"id":50642248,"identity":"bb688cca-80ab-4283-8fbb-06e1f7706112","added_by":"auto","created_at":"2024-02-05 06:13:01","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1362874,"visible":true,"origin":"","legend":"\u003cp\u003eOptical and electronic characterization of the constituent metallic NPs of plasmonic gelatine-based light filters. (A) Experimental surface plasmon resonances of the NPs obtained by UV-vis spectroscopy. From left to right: AgNPs (405 nm), AuNPs (537 nm), AuNRs (730, 920 and 1050 nm). (B-F) Representative TEM images for AgNSp (Φ = 51 nm), AuNPs (Φ = 61 nm), AuNRs730 (AR=3.1), AuNRs920 (AR=5.2) and AuNRs920 (AR=6.5).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-3911708/v1/1007a5e68ee10f27de231dc9.png"},{"id":50642244,"identity":"2b0fa8a1-48dc-441b-997c-5652fa4c5389","added_by":"auto","created_at":"2024-02-05 06:13:01","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":84686,"visible":true,"origin":"","legend":"\u003cp\u003eUV-Vis-NIR characterization of the hydrated nanocomposite. Inset: measured transmittance (dots) of the estimated absorbance. Theoretical result as dashed line. Absorbance 0 correspond to the hydrated biopolymer without AgNPs.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-3911708/v1/909b237972410215c2e494c3.png"},{"id":50642247,"identity":"303e4820-62e8-4b13-a01d-944e0552a2ee","added_by":"auto","created_at":"2024-02-05 06:13:01","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":767686,"visible":true,"origin":"","legend":"\u003cp\u003eOptical and electronic microscopy characterization of gelatin-based light filters around 437 nm with AgNPs. (A) UV-Vis-NIR spectra (B) Optical images. (C) SEM images of the cross-section and surface of the filters with secondary electrons. Backscattering image showing the distribution of AgNPs inside the material.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-3911708/v1/752fd9ca834a4b5c01bef274.png"},{"id":50642606,"identity":"ed50f0b5-3b38-47cc-8b51-a096d2b0ab38","added_by":"auto","created_at":"2024-02-05 06:21:01","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":661252,"visible":true,"origin":"","legend":"\u003cp\u003eOptical and electronic microscopy characterization of gelatin-based light filters around 437 nm with AgNPs. (A) UV-Vis-NIR spectra of the hydrated material with AuNPs and AuNRs. (B) UV-Vis-NIR spectra of the gelatine-based filters with different NPs. (C) Optical images of the filters in front a pseudo-tumbling E chart to showcase the visibility of the material.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-3911708/v1/a230c442f5c797ab6c4a5b39.png"},{"id":50642250,"identity":"6ecae800-33fe-4081-b987-afb8f262a7e2","added_by":"auto","created_at":"2024-02-05 06:13:01","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":357306,"visible":true,"origin":"","legend":"\u003cp\u003eFilter configurations for multiuse of filters. (A) Bandpass configuration in the Vis-NIR range (550 to 1010 nm) using the filters with AgNPs and AuNRs1050. (B) Notch configuration using the AuNRs730 and AuNRs1050 filters. In dashed lines the ideal approximation.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-3911708/v1/63f0ad4fa125f0a9a354d1b5.png"},{"id":50642245,"identity":"3e6f5438-2808-4a46-a22a-59e920e2768e","added_by":"auto","created_at":"2024-02-05 06:13:01","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":132506,"visible":true,"origin":"","legend":"\u003cp\u003eReflectance of the gelatine light filters. (A) Measured total and diffuse reflectance, specular reflection is included as the difference between them. (B) Normalized transmitante and difusse reflection of the light filters with AuNPs. (C) Calculated cross sections for a 51 nm AuNP.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-3911708/v1/ad5bec6a5c4decd8396f44cf.png"},{"id":57153206,"identity":"9c4de0f6-880e-481d-b536-611de24e1741","added_by":"auto","created_at":"2024-05-26 07:06:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5427559,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3911708/v1/9f6aca6a-697f-4333-a397-13ebbde2033f.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Eco-friendly and Biocompatible Gelatin Plasmonic Filters for UV-Vis-NIR Light","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe increasing consumer demand for environmentally-friendly products has shifted research efforts toward the development of eco-friendly materials and sustainable processes. Among these new materials, nanocomposites that incorporate biopolymers occupy a prominent position, primarily because biopolymers are naturally occurring in living organisms and are presumed to be biodegradable and biocompatible. Interestingly, the use of biopolymers is also prevalent in the food industry. For instance, plant-based guar gum and bacteria-derived xanthan gum are biopolymers commonly used as thickening and stabilizing agents.\u003csup\u003e1\u0026ndash;3\u003c/sup\u003e However, gelatin holds a unique place among the biopolymers used in cooking. Gelatin is a protein-based substance derived through the hydrolysis of animal connective tissues. It is highly soluble in water and is also considered nutritious due to its high protein content (85\u0026ndash;92%), containing all essential amino acids except for tryptophan, and its low caloric value. \u003csup\u003e4\u003c/sup\u003e Additionally, its unique melt-in-the-mouth property, due to the formation of thermally reversible gels with a gel-melting point below body temperature (\u0026lt;\u0026thinsp;35\u0026deg;C), is highly prized for making gel desserts.\u003csup\u003e5\u003c/sup\u003e As it is edible, gelatin capsules and microcapsules are commonly found in pharmaceuticals.\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eNanocomposites with gelatin include works with carbon nanotubes\u003csup\u003e6\u003c/sup\u003e and copper nanoparticles (NPs)\u003csup\u003e7\u003c/sup\u003e to create conductive materials. Nonetheless, the development of gelatin-based nanocomposites for photonics and optics has not been extensively studied.\u003csup\u003e8\u003c/sup\u003e In this work, we explore an intriguing application for optical uses: the design and fabrication of gelatin-based nanocomposites for light filters. To impart optical properties to a traditionally transparent material,\u003csup\u003e9\u003c/sup\u003e we incorporated a variety of metallic NPs into the polymeric matrix, providing mechanical support. Due to their size, metallic NPs can sustain localized surface plasmon resonance (LSPR), enabling light manipulation (entrapment) at the nanoscale. By varying the physical characteristics of the NPs, such as material, size, and geometry, it is possible to finely tune their optical properties across the electromagnetic spectrum. The inclusion of NPs allows us to work within the UV-Visible-NIR range with high control over the optical filtering properties of the nanocomposites. These plasmonic gelatin-based light filters exhibit modular behavior, allowing them to be used in combination to add or remove the desired spectral range of interest, while being composed of sustainable and ecological materials. Our work presents an alternative approach to the production of light filters that meets requirements in a manner comparable to selecting options from a restaurant menu.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003eTo create plasmonic gelatin-based light filters, we alter the inherent optical properties of plain gelatin by dispersing plasmonic nanoparticles (NPs). Combining the optical transparency of gelatin with the absorption capabilities of metallic NPs, we hypothesized that achieving the desired filtering effect was contingent on preventing NP agglomeration, which could otherwise obscure the distinct localized surface plasmon resonances (LSPRs) of the NPs. Accordingly, we devised and adhered to the procedure outlined in Fig. \u003cspan\u003e1\u003c/span\u003e. Initially, five types of NPs were chosen and synthesized using established methods: silver nanospheres (AgNPs), gold nanospheres (AuNPs), and gold nanorods (AuNRs) with three varying aspect ratios. Subsequently, these NPs were amalgamated with pre-dissolved gelatin to create a NP@biopolymer solution, which was then cast in petri dishes. Post-casting, the molds were refrigerated at 4\u0026deg;C for 48 hours to ensure solidification (gelation). Once set, the nanocomposites were exposed to air for drying. Finally, the dry material was carefully extracted using tweezers.\u003c/p\u003e\n\u003cp\u003eThe chosen set of NPs demonstrated robust absorption across the UV-Vis-NIR spectrum due to LSPR, as evidenced by the absorption spectra in Fig. \u003cspan\u003e2\u003c/span\u003eA. Plasmon resonances were identified at 405 nm for AgNPs, 537 nm for AuNPs, and at 730, 920, and 1050 nm for AuNRs. This extensive absorption range underscores the ability to adjust the optical properties of NPs. Representative Transmission TEM images for each NP type are displayed in Figs. \u003cspan\u003e2\u003c/span\u003eB-F. The average sizes were 51\u0026thinsp;\u0026plusmn;\u0026thinsp;13 nm for AgNPs and 61\u0026thinsp;\u0026plusmn;\u0026thinsp;2 nm for AuNPs. Meanwhile, the lengths of AuNRs were 69\u0026thinsp;\u0026plusmn;\u0026thinsp;6, 51\u0026thinsp;\u0026plusmn;\u0026thinsp;4, and 50\u0026thinsp;\u0026plusmn;\u0026thinsp;12 nm, correlating with increasing aspect ratios (AR) of 3.1, 5.2, and 6.5 for AuNRs730, AuNRs920, and AuNRs1050, respectively. Notably, while all NPs had comparable sizes, their geometry and composition markedly influenced their optical responses. Specifically, the AR of AuNRs facilitated controlled responses in the Vis-NIR region,\u003csup\u003e10\u003c/sup\u003e while the AgNPs\u0026rsquo; LSPR bordered the visible and UVA regions. \u003csup\u003e11\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eDirect addition of dry biopolymer (laminates) to the NP colloid resulted in NP aggregation. Therefore, the biopolymer was first hydrated (10 min in cold water), then dissolved (at 35\u0026deg;C), and finally combined with a predetermined volume of NPs. To calculate the necessary NP volume, we assumed a linear relationship between the NPs\u0026apos; absorption and the optical path length. Using a standard petri dish as a mold (diameter\u0026thinsp;=\u0026thinsp;9 cm) and targeting a final concentration of 2% biopolymer in a 15 ml volume for an easily detachable nanocomposite, we employed the expression:\u003c/p\u003e\n\u003cdiv id=\"Equ1\"\u003e\n \u003cdiv id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\u003cimg src=\"https://myfiles.space/user_files/122228_c8a1650c59388082/122228_custom_files/img1707113394.png\"\u003e\u003cbr\u003e\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003ewhere A is the desired maximum absorption. After determining the NP volume, water was added to achieve a final 9 ml volume, which was then mixed with a 6 ml aliquot of 5% gelatin. The resultant liquid NP@biopolymer solution was cast in the mold and refrigerated to form hydrated gelatinized nanocomposites. Any present bubbles were removed while the mixture was still liquid to ensure material uniformity.\u003c/p\u003e\n\u003cp\u003eWe examined the formation of hydrated gelatinized nanocomposites by preparing and analyzing five samples with varying concentrations of AgNPs using UV-Vis-NIR spectroscopy (Fig. \u003cspan\u003e3\u003c/span\u003e). A pronounced absorption at 410 nm, attributed to the AgNPs, was observed. The 5 nm redshift aligns with the expected change in the dielectric constant due to the biopolymer. Absorption from 1320 nm onward was attributed to the material\u0026apos;s water content. Notably, refrigeration was essential for gelation of the NP@biopolymer, distinct from pure gelatin. Without this step, the final filters were inhomogeneous. Correlating the absorbance of the liquid (0.4, 0.8, 1.2, and 1.6) before gelation with the experimental transmittance of the hydrated NP@biopolymer (at 410 nm) indicated good agreement with the predicted transmittance, suggesting that the gelation process does not cause NP aggregation but instead immobilizes their position within the biopolymer matrix.\u003c/p\u003e\n\u003cp\u003eThe subsequent drying process aimed to eliminate water\u0026apos;s impact on the nanocomposite\u0026apos;s transmittance and enhance its mechanical properties. Figure \u003cspan\u003e4\u003c/span\u003eA illustrates that the absorption starting from 1320 nm, visible in Fig. \u003cspan\u003e3\u003c/span\u003e, is nearly removed in all samples post-drying. Although the final transmittance still aligns with theoretical predictions, a broadening of the absorption peak and a decrease in maximum transmittance (89%) are observed. These changes suggest that the AgNPs draw closer as the water content diminishes, forming occasional interactions and thus reducing the maximum absorption by the NPs, which is compensated by the biopolymer\u0026apos;s absorption. However, a distinct absorption band due to the NPs remains. The highest absorption occurs between 436\u0026ndash;438 nm, which is redshifted compared to the hydrated material and the original colloidal particles. This finding aligns with the increased dielectric medium of the material: n\u0026thinsp;=\u0026thinsp;1.536 for pure gelatin at 632.8 nm.\u003csup\u003e9\u003c/sup\u003e The shiny appearance and uniform color of the filters with high absorption (\u0026gt;\u0026thinsp;50%) over a white background are shown in Fig. \u003cspan\u003e4\u003c/span\u003eB. The filters are thin, flexible layers but are prone to tearing. SEM characterization (Fig. \u003cspan\u003e4\u003c/span\u003eC) revealed uniform thickness (33.4 \u0026micro;m) and a distinctive layer pattern on the surface, likely imprinted by the mold. Backscattered electron imaging confirmed even particle distribution within the material.\u003c/p\u003e\n\u003cp\u003eHaving established the methodology for light filters with AgNPs, we extended our process to include all previously selected NPs (i.e., AuNPs, AuNRs730, AuNRs920, and AuNRs1050) for filters with approximately 60% transmittance. This transmittance level was chosen as a balance between absorption efficiency and ease of preparation. The UV-Vis-NIR spectra of these nanocomposites (Fig. \u003cspan\u003e5\u003c/span\u003eA) indicate that the gelation process also prevents aggregation of the AuNPs and AuNRs. However, the drying process differed from that for AgNPs: an increase (~\u0026thinsp;10%) in final absorbance was observed (Fig. \u003cspan\u003e5\u003c/span\u003eB). This increase, previously attributed to gelatin, was overshadowed by interparticle interactions in AgNP filters. In AuNP and AuNR filters, this interparticle interaction compensation seems absent. This hypothesis is supported by a smaller broadening of the AuNPs absorption peak compared with the AgNPs. One explanation is that the AuNPs and AuNRs have CTAC and CTAB stabilizing layers, respectively, that attach to the metal surface with an amine group. Thus, compared to the easily displaced citrate on AgNPs, the AuNPs and AuNRs are less bound to the biopolymer during drying and tend to arrange apart from other NPs. The final appearance of the filters is shown in Fig. \u003cspan\u003e5\u003c/span\u003eC, alongside a filter with AgNPs for comparison. A small image with letters resembling a \u0026ldquo;tumbling E\u0026rdquo; chart is placed behind the filter to demonstrate the material\u0026apos;s transparency. These results show that gelatin-based filters can be tuned within the UV-Vis-NIR spectrum using the employed NPs\u0026apos; LSPR. Therefore, this procedure can be expanded to other morphologies or materials with a desired absorption spectrum. The gelatin provides a transparent canvas that can be exploited as desired.\u003c/p\u003e\n\u003cp\u003eThe process for obtaining biopolymer-based light filters is not limited to selecting constituent NPs but can also be designed through arrangements of filters. This approach is demonstrated using the presented filters to create two commonly used filter configurations: a bandpass filter and a notch filter. In the first example (Fig. \u003cspan\u003e6\u003c/span\u003eA), individual AgNPs and AuNRs1050 filters were stacked. This configuration restricts passing wavelengths within the range of 550 to 1010 nm, effectively acting as a band filter. The optical image over a pseudo-tumbling E chart allows visual inspection of the material, as most of the optical range is permitted to pass through. A different filter arrangement utilizes AuNRs730 and AuNRs1050 filters (Fig. \u003cspan\u003e6\u003c/span\u003eB), reducing NIR range wavelengths from 730 to 1085 nm, hence predominantly acting as a notch filter. These basic examples of filter configurations aim to demonstrate the modularity of the filters and their potential for integration into existing systems that could benefit from the broad spectral range and simple fabrication process.\u003c/p\u003e\n\u003cp\u003eThe presented gelatin-based filters primarily reduce incident light through absorption by the NPs. However, this method of light filtering is not always ideal. For example, IR filters used in buildings or automobiles to reduce energy consumption during summer prefer to reflect rather than absorb IR radiation.\u003csup\u003e12\u003c/sup\u003e This preference stems from the fact that a window absorbing IR radiation would act as a heater, despite preventing heat transfer by radiation. Therefore, we investigated whether the light not transmitted by our filters is entirely absorbed. To do this, we measured the total and diffuse reflectance of the filter surface with AuNPs, and from these, we estimated the specular reflection, as shown in Fig. \u003cspan\u003e7\u003c/span\u003eA. The total reflection accounted for an average of 7% of the untransmitted light (400-2500nm), with the maximum in diffuse reflection redshifted from the maximum absorption. Plotting the normalized transmittance and diffuse reflection (Fig. \u003cspan\u003e7\u003c/span\u003eB) highlights this shift (25nm), which can be explained in terms of the calculated cross-sections of the far field. We employed the boundary element theory\u003csup\u003e13\u003c/sup\u003e in the MNPBEM\u003csup\u003e14\u003c/sup\u003e implementation in MATLAB to distinguish the absorption and scattering contributions to the total extinction (Fig. \u003cspan\u003e7\u003c/span\u003eC), revealing an 11 nm redshift between them. This suggests that the dominant component of the diffusely reflected light can be attributed to scattering by the AuNPs. Although this contribution is minimal, it demonstrates that the NPs in the filters can manipulate incident light through absorption or scattering. This opens the possibility of creating filters that reflect light instead of absorbing it by changing the constituent NPs.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn this research, we have successfully pioneered the development and implementation of innovative gelatin-based light filters using metallic nanoparticles (NPs), an endeavor inspired by the culinary utilization of biopolymers. This groundbreaking approach is expected to catalyze further research and exploration into the application of biomaterials across various sectors, including optics, materials science, electronics, and potentially beyond. Embracing the current environmental ethos, these optical filters are fashioned from biocompatible and eco-friendly materials, epitomizing the shift towards green and sustainable material research. The filters' adaptability across the UV-Visible-NIR electromagnetic spectrum is a significant achievement, allowing for precise customization and functionality. Moreover, their modular nature facilitates easy integration into existing technological and scientific apparatus, enhancing their utility and applicability. The fabrication process of these filters is notably straightforward and cost-effective, eliminating the need for elaborate or high-cost equipment. This simplicity in production paves the way for widespread adoption and experimentation in both academic and industrial settings, potentially leading to novel applications and advancements in the field of material science and photonics..\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e \u003cb\u003eMaterials\u003c/b\u003e. Tetrachloroauric acid (HAuCl\u003csub\u003e4\u003c/sub\u003e\u0026middot;3H\u003csub\u003e2\u003c/sub\u003eO), hexadecyltrimethylammonium bromide 99% (CTAB), cetyltrimethylammonium chloride solution 0.78 M, sodium borohydride 99% (NaBH\u003csub\u003e4\u003c/sub\u003e), silver nitrate (AgNO\u003csub\u003e3\u003c/sub\u003e), hydrochloric acid 37% (HCl), Hydroquinone 99% (HQ), L-ascorbic acid 99% (AA) and tri-sodium citrate dihydrate 99.5% (Na\u003csub\u003e3\u003c/sub\u003eCit) were purchased from Thermo Fisher Scientific. Milli-Q water (18.2 MΩ) was used in all preparations. Commercial gelatine was purchased from Neutral gelatine was purchased from Ewald-Gelatine.\u003c/p\u003e \u003cp\u003e \u003cb\u003eCharacterization\u003c/b\u003e. TEM images were collected from a JEOL 1010 and 1011. Samples were prepared on carbon-Formvar-coated 200 mesh copper grids. SEM samples were imaged with a JEOL JSM-6700f. UV-VIS spectroscopy was performed in a Jasco V-770.\u003c/p\u003e \u003cp\u003e \u003cb\u003eSynthesis of AgNPs.\u003c/b\u003e AgNPs were synthesized using a modified version of a previously reported protocol.\u003csup\u003e15\u003c/sup\u003e Briefly, a AgNO\u003csub\u003e3\u003c/sub\u003e solution (100 ml, 1 mM) was heated to boiling point. Then 2 ml of Na\u003csub\u003e3\u003c/sub\u003eCit (2 ml, 34 mM) was rapidly injected into the boiling solution an let under vigorous stirring for 45 minutes. Finally, the solution was left to cool at room temperature.\u003c/p\u003e \u003cp\u003e \u003cb\u003eSynthesis of AuNPs with uniform diameters.\u003c/b\u003e Smooth AuNPs with 43 nm of diameter were synthesized by a modification of the seed-mediated growth protocol.\u003csup\u003e16\u003c/sup\u003e Firstly, AuNPs with 10 nm of diameter were grown by addition of 2 ml of HAuCl\u003csub\u003e4\u003c/sub\u003e solution (5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e M) using a syringe pump with injection rate of 2 ml/h in a solution containing 2 ml of CTAC 0.2 M, 1.5 ml of AA (0.1 M) and 50 \u0026micro;l of the initial seeds. After that, 2 ml of HAuCl\u003csub\u003e4\u003c/sub\u003e solution (5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e M) were injected (with injection rate of 2 ml/h) in a second growth solution containing 2 ml of CTAC 0.1 M, 13 \u0026micro;l of AA 0.1 M and 10 \u0026micro;l of the 10 nm seeds.\u003c/p\u003e \u003cp\u003e \u003cb\u003eSynthesis of AuNRs\u003c/b\u003e. AuNRs were prepared by the seed-mediated growth method following two protocols previously described.\u003csup\u003e17,18\u003c/sup\u003e In order to tune the longitudinal LSPR some modifications have been made in the addition of AgNO\u003csub\u003e3\u003c/sub\u003e and seeds solutions in the growth process.\u003c/p\u003e \u003cp\u003e \u003cb\u003ePreparation of the initial, CTAB-Capped Au clusters (seeds).\u003c/b\u003e A fresh aqueous NaBH\u003csub\u003e4\u003c/sub\u003e solution (0.3 ml, 0.01 M) was rapidly added into a 4.7 ml of an aqueous solution containing HAuCl\u003csub\u003e4\u003c/sub\u003e (2.5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e M) and CTAB (0.1 M). The mixture was stirred a speed of 1000 rpm for 2 min, and then kept undisturbed at 27\u0026deg;C for 3 h to ensure complete decomposition of the NaBH\u003csub\u003e4\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003eAuNRs with LSPR centered at 730 nm and 920 nm.\u003c/b\u003e AuNRs with LSPR centered at 730 nm and 920 nm, respectively, were synthesized by a modification of the seed-mediated growth protocol described by Scarabelli et all.\u003csup\u003e2\u003c/sup\u003e For 10 ml of solution with final concentration of HAuCl\u003csub\u003e4\u003c/sub\u003e and CTAB fixed at 5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e M and 0.1 M, respectively, we used 20 \u0026micro;l of the Au-seeds in the growth solution (for AuNR with LSPR at 730 nm) and 32 \u0026micro;l of the Au-seeds (for AuNR with LSPR at 920 nm).\u003c/p\u003e \u003cp\u003e \u003cb\u003eAuNRs with LSPR\u0026thinsp;=\u0026thinsp;1050 nm.\u003c/b\u003e AuNRs with LSPR centered at 1090 nm were synthesized by a modification of the seed-mediated growth protocol described by Vigderman et all.\u003csup\u003e1\u003c/sup\u003e For a typical 10 ml of solution with final concentration of HAuCl\u003csub\u003e4\u003c/sub\u003e and CTAB fixed at 5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e M and 0.1 M, respectively, we used 0.4 ml of seeds and 0.5 ml of HQ.\u003c/p\u003e \u003cp\u003eIn the last step AuNPs and AuNRs were collected by centrifugation at 6000 rpm for 40 min, and then washed two times and redispersed in water for characterization.\u003c/p\u003e \u003cp\u003e \u003cb\u003ePlasmonic galatine-based light filters.\u003c/b\u003e The nanocomposites were obtained through the dispersion of plasmonic NPs on a gelatin matrix. To do this a certain amount of gelatin was hydrated in cold water for 10 minutes and then dissolved in water at 35\u0026deg;C. Then was mixed with colloidal NPs to obtain a solution with final concentration of 2% (w/v) gelatine and the desired NPs concentration (Eq.\u0026nbsp;\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). After that, the plasmonic sol was transferred to petri dishes and kept at 4\u0026deg;C for 48h in a fridge. To dry the material, the petri dishes were left in an open atmosphere for 7 days. To detach the filters, they were pulled out with tweezers while deforming the mold.\u003c/p\u003e \u003cp\u003e \u003cb\u003eNumerical cross section calculations.\u003c/b\u003e Using the MNPBEM\u003csup\u003e14\u003c/sup\u003e tool box, we place a AuNP with diameter of 51 nm in an ideal dielectric media (n\u0026thinsp;=\u0026thinsp;1.536).\u003csup\u003e8\u003c/sup\u003e The NP was modeled as a \u0026ldquo;trisphere\u0026rdquo; object with 484 vertex. For the dielectric constant of gold we used experimental data previously reported.\u003csup\u003e19\u003c/sup\u003e\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eData availability\u003c/h2\u003e \u003cp\u003eThe authors declare that all relevant data supporting the findings of this study are available within the paper.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the projects\u0026nbsp;\u003cstrong\u003ePID2020-120306RB-I00\u0026nbsp;\u003c/strong\u003ePID2020-113704RB-I00/AEI/10.13039/501100011033; TED2021-132101B-I00,\u0026nbsp;PDC2021-121787-I00\u0026nbsp;funded by MCIN/AEI/10.13039/501100011033 and European Union \u0026ldquo;NextGenerationEU\u0026rdquo;/PRTR; Xunta de Galicia ED431C 2022/24;\u0026nbsp;2020SGR00166 (funded by Generalitat de Catalu\u0026ntilde;a), 2021PFR-URV-B2-02 (funded by Universitat Rovira i Virgili),\u0026nbsp;and HORIZON-EIC-2022-PATHFINDERCHALLENGES-01-06, HORIZON-HLTH-2022-DISEASE-06-TWO-STAGE, GA. No. 857543 and ENSEMBLE3 \u0026ndash; Centre of Excellence for nanophotonics, advanced materials and novel crystal growth-based technologies\u0026rdquo; project (GA No. MAB/2020/14) of the\u0026nbsp;European Union Horizon 2020 Research and Innovation Program.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIBBC, JM and YNM designed, performed, and analyzed experiments. IBBC and R.A.A.P wrote the manuscript. JM, IBBC and R.A.A.P conceptual idea. M.A.C.D, V.G. and R.A.A.P obtained the funding, analyzed data and supervised the work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMortensen, A.\u003cem\u003e et al.\u003c/em\u003e Re‐evaluation of xanthan gum (E 415) as a food additive. \u003cem\u003eEFSA Journal\u003c/em\u003e \u003cstrong\u003e15\u003c/strong\u003e, doi:10.2903/j.efsa.2017.4909 (2017).\u003c/li\u003e\n\u003cli\u003eMudgil, D., Barak, S. \u0026amp; Khatkar, B. S. Guar gum: processing, properties and food applications\u0026mdash;A Review. \u003cem\u003eJournal of Food Science and Technology\u003c/em\u003e \u003cstrong\u003e51\u003c/strong\u003e, 409-418, doi:10.1007/s13197-011-0522-x (2014).\u003c/li\u003e\n\u003cli\u003eHabibi, H. \u0026amp; Khosravi-Darani, K. Effective variables on production and structure of xanthan gum and its food applications: A review. \u003cem\u003eBiocatalysis and Agricultural Biotechnology\u003c/em\u003e \u003cstrong\u003e10\u003c/strong\u003e, 130-140, doi:10.1016/j.bcab.2017.02.013 (2017).\u003c/li\u003e\n\u003cli\u003eSchrieber, R. \u0026amp; Gareis, H. \u003cem\u003eGelatine handbook: theory and industrial practice\u003c/em\u003e. (John Wiley \u0026amp; Sons, 2007).\u003c/li\u003e\n\u003cli\u003eStevens, P. in \u003cem\u003eFood Stabilisers, Thickeners and Gelling Agents\u003c/em\u003e (ed Alan Imeson) 116-144 (2009).\u003c/li\u003e\n\u003cli\u003eMeiyazhagan, A., Thangavel, S., Daniel P, H., Pulickel M, A. \u0026amp; Palanisamy, T. Electrically conducting nanobiocomposites using carbon nanotubes and collagen waste fibers. \u003cem\u003eMaterials Chemistry and Physics\u003c/em\u003e \u003cstrong\u003e157\u003c/strong\u003e, 8-15, doi:10.1016/j.matchemphys.2015.03.005 (2015).\u003c/li\u003e\n\u003cli\u003eCheirmadurai, K., Biswas, S., Murali, R. \u0026amp; Thanikaivelan, P. Green synthesis of copper nanoparticles and conducting nanobiocomposites using plant and animal sources. \u003cem\u003eRSC Advances\u003c/em\u003e \u003cstrong\u003e4\u003c/strong\u003e, 19507, doi:10.1039/c4ra01414f (2014).\u003c/li\u003e\n\u003cli\u003eColusso, E. \u0026amp; Martucci, A. An overview of biopolymer-based nanocomposites for optics and electronics. \u003cem\u003eJournal of Materials Chemistry C\u003c/em\u003e \u003cstrong\u003e9\u003c/strong\u003e, 5578-5593, doi:10.1039/d1tc00607j (2021).\u003c/li\u003e\n\u003cli\u003eManocchi, A. K., Domachuk, P., Omenetto, F. G. \u0026amp; Yi, H. Facile fabrication of gelatin-based biopolymeric optical waveguides. \u003cem\u003eBiotechnology and Bioengineering\u003c/em\u003e \u003cstrong\u003e103\u003c/strong\u003e, 725-732, doi:10.1002/bit.22306 (2009).\u003c/li\u003e\n\u003cli\u003eChang, H.-H. \u0026amp; Murphy, C. J. Mini Gold Nanorods with Tunable Plasmonic Peaks beyond 1000 nm. \u003cem\u003eChemistry of Materials\u003c/em\u003e \u003cstrong\u003e30\u003c/strong\u003e, 1427-1435, doi:10.1021/acs.chemmater.7b05310 (2018).\u003c/li\u003e\n\u003cli\u003eBast\u0026uacute;s, N. G., Merko\u0026ccedil;i, F., Piella, J. \u0026amp; Puntes, V. Synthesis of Highly Monodisperse Citrate-Stabilized Silver Nanoparticles of up to 200 nm: Kinetic Control and Catalytic Properties. \u003cem\u003eChemistry of Materials\u003c/em\u003e \u003cstrong\u003e26\u003c/strong\u003e, 2836-2846, doi:10.1021/cm500316k (2014).\u003c/li\u003e\n\u003cli\u003eButt, M.\u003cem\u003e et al.\u003c/em\u003e \u003cem\u003eInfrared reflective coatings for building and automobile glass windows for heat protection\u003c/em\u003e. Vol. 10342 OTT (SPIE, 2017).\u003c/li\u003e\n\u003cli\u003eGarc\u0026iacute;a De Abajo, F. J. \u0026amp; Howie, A. Retarded field calculation of electron energy loss in inhomogeneous dielectrics. \u003cem\u003ePhysical Review B\u003c/em\u003e \u003cstrong\u003e65\u003c/strong\u003e, doi:10.1103/physrevb.65.115418 (2002).\u003c/li\u003e\n\u003cli\u003eHohenester, U. \u0026amp; Tr\u0026uuml;gler, A. MNPBEM \u0026ndash; A Matlab toolbox for the simulation of plasmonic nanoparticles. \u003cem\u003eComputer Physics Communications\u003c/em\u003e \u003cstrong\u003e183\u003c/strong\u003e, 370-381, doi:10.1016/j.cpc.2011.09.009 (2012).\u003c/li\u003e\n\u003cli\u003eLee, P. C. \u0026amp; Meisel, D. Adsorption and surface-enhanced Raman of dyes on silver and gold sols. \u003cem\u003eThe Journal of Physical Chemistry\u003c/em\u003e \u003cstrong\u003e86\u003c/strong\u003e, 3391-3395, doi:10.1021/j100214a025 (1982).\u003c/li\u003e\n\u003cli\u003eZheng, Y., Zhong, X., Li, Z. \u0026amp; Xia, Y. Successive, Seed‐Mediated Growth for the Synthesis of Single‐Crystal Gold Nanospheres with Uniform Diameters Controlled in the Range of 5\u0026ndash;150 nm. \u003cem\u003eParticle \u0026amp; Particle Systems Characterization\u003c/em\u003e \u003cstrong\u003e31\u003c/strong\u003e, 266-273, doi:10.1002/ppsc.201300256 (2014).\u003c/li\u003e\n\u003cli\u003eScarabelli, L., S\u0026aacute;nchez-Iglesias, A., P\u0026eacute;rez-Juste, J. \u0026amp; Liz-Marz\u0026aacute;n, L. M. A \u0026ldquo;Tips and Tricks\u0026rdquo; Practical Guide to the Synthesis of Gold Nanorods. \u003cem\u003eThe Journal of Physical Chemistry Letters\u003c/em\u003e \u003cstrong\u003e6\u003c/strong\u003e, 4270-4279, doi:10.1021/acs.jpclett.5b02123 (2015).\u003c/li\u003e\n\u003cli\u003eVigderman, L. \u0026amp; Zubarev, E. R. High-Yield Synthesis of Gold Nanorods with Longitudinal SPR Peak Greater than 1200 nm Using Hydroquinone as a Reducing Agent. \u003cem\u003eChemistry of Materials\u003c/em\u003e \u003cstrong\u003e25\u003c/strong\u003e, 1450-1457, doi:10.1021/cm303661d (2013).\u003c/li\u003e\n\u003cli\u003eJohnson, P. B. \u0026amp; Christy, R. W. Optical Constants of the Noble Metals. \u003cem\u003ePhysical Review B\u003c/em\u003e \u003cstrong\u003e6\u003c/strong\u003e, 4370-4379, doi:10.1103/PhysRevB.6.4370 (1972).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-3911708/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3911708/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this work, we present the development of light filters using a gelatin-based nanocomposite. Owing to the plasmonic properties of metallic nanoparticles (NPs), these filters can be customized across the UV-Visible-NIR spectrum. Additionally, the filters are designed for modular use, allowing for the addition or removal of desired spectral ranges. The nanocomposites are composed of biodegradable and biocompatible materials. These plasmonic gelatin-based filters block light due to the Localized Surface Plasmon Resonance (LSPR) of the NPs and can be tailored to meet various requirements, akin to a diner selecting options from a menu. This approach is inspired by culinary techniques, and we anticipate it will stimulate further exploration of biomaterials for applications in optics, materials science, electronics, and more.\u003c/p\u003e","manuscriptTitle":"Eco-friendly and Biocompatible Gelatin Plasmonic Filters for UV-Vis-NIR Light","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-02-05 06:12:57","doi":"10.21203/rs.3.rs-3911708/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"communications-chemistry","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"commschem","sideBox":"Learn more about [Communications Chemistry](http://www.nature.com/commschem/)","snPcode":"","submissionUrl":"","title":"Communications Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Communications Series","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"a79fb9a8-9589-401d-84eb-1a9f2b5225f5","owner":[],"postedDate":"February 5th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-05-26T07:06:30+00:00","versionOfRecord":{"articleIdentity":"rs-3911708","link":"https://doi.org/10.1038/s42004-024-01202-6","journal":{"identity":"communications-chemistry","isVorOnly":false,"title":"Communications Chemistry"},"publishedOn":"2024-05-25 04:00:00","publishedOnDateReadable":"May 25th, 2024"},"versionCreatedAt":"2024-02-05 06:12:57","video":"","vorDoi":"10.1038/s42004-024-01202-6","vorDoiUrl":"https://doi.org/10.1038/s42004-024-01202-6","workflowStages":[]},"version":"v1","identity":"rs-3911708","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3911708","identity":"rs-3911708","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}