Dual-emission ratiometric fluorescent probe based on Uio-66- NH 2 @CQDs for quantitative detection of acetophenone

Dual-emission ratiometric fluorescent probe based on Uio-66- NH 2 @CQDs for quantitative detection of acetophenone | 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 Research Article Dual-emission ratiometric fluorescent probe based on Uio-66- NH 2 @CQDs for quantitative detection of acetophenone Yongze Shou, Zhouqing Xu, Huijun Li, Wenjie Liu, Junkun Wang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7393397/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 17 Oct, 2025 Read the published version in Journal of Fluorescence → Version 1 posted 9 You are reading this latest preprint version Abstract It is imperative that developing fluorescent probe to detect volatile organic compound such as acetophenone (AP) to protect environment public health protection. In this work, we synthesized a ratiometric Uio-66-NH2@CQDs sensor through post-synthetic modification by anchoring carbon quantum dots onto Uio-66-NH2 metal-organic framework, which could be readily utilized as self-calibrating nanoprobe for selective detection of AP over other potential interferants. Upon the addition of AP, Uio-66-NH2@CQDs featured a decreased emision at 430 nm and an enhanced emission at 550 nm, accompanied by a characteristic fluorescence color transition from blue-green to yellow. By adopting the ration of I430nm/I550nm as the detection signal, Uio-66-NH2@CQDs could distinguish AP with excellent performance. The limit of detection for AP was estimated to be 175.6 nM, which was a significant value. Additionally, we demonstrated that on-site visual inspection of AP in industrial wastewater using a paper-based Uio-66-NH2@CQDs analysis device. Uio-66-NH2@CQDs AP sensing Ratiometric sensor Fluorescence detection Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction The ever-increasing industrial production has led to a growing discharge of organic wastewater and various chemical wastes, causing increasingly severe environmental impacts and drawing significant attention in society [1,2]. Acetophenone (AP), which usually serves as an indispensable precursor in synthesizing pharmaceuticals, dyes and rubber additives, is a highly toxic and prevalent volatile organic compound [3-6]. Its improper management or potential AP leakage would pose significant environmental and health risks including respiratory distress, chronic cough, and skin cancer, and potentially trigger public health concerns [7,8]. Consequently, it is crucial to develop an efficient, rapid, and sensitive detection method of AP for environmental monitoring and public health protection [9,10]. Traditional analytical instrumentation techniques such as Raman spectroscopy, X-ray dispersion, ion mobility spectroscopy are reported to be used to detect and quantify the concentration of AP [11,12]. However, these methods either require skilled operators or tedious pre-treatment of samples. Integrating these methods into portable devices is difficult, which severely limits their application in field testing [13,14]. Fluorescence spectroscopy has emerged as a transformative analytical tool, offering unparalleled sensitivity, real-time response, and non-destructive operation [15,16]. Among fluorescent materials, metal-organic frameworks (MOF) stand out due to their structural programmability, permanent porosity, and host-guest recognition capabilities [17,18]. The matrix in MOF could act as a molecular sieve to preconcentrate target analytes via host-guest interactions (e.g., π-π stacking, hydrogen bonding), further enable analyte-specific fluorescence modulation through mechanisms such as energy transfer or electron exchange [19-21]. However, most reported MOF-based sensor are single-emission probes, which are inherently susceptible to environmental interference, leading to unreliable signals in complex matrices [22,23]. In this regard, ratiometric fluorescent sensors have the ability of calibrating against systemic errors by simultaneously tracking changes in two distinct emission bands, thereby enhancing accuracy and reproducibility [24,25]. Therefore, integrating other fluorescent molecules with L-MOFs to construct dual-emission ratiometric sensor is a suitable strategy, where analyte-induced differential quenched or enhanced emissions of fluorescent molecules and MOF cancels out matrix interference, achieving sub-ppm sensitivity and field-compatible robustness [26,27]. Carbon quantum dots (CQDs) captured researcher’s interest due to their tunable photoluminescence, exceptional photostability, and rapid (<1 min) analyte-responsive signal transitions mediated by electron transfer or surface interactions [28,29]. However, individual CQDs often face limitations in practical application due to non-specific binding and aggregation-induced quenching (ACQ) in aqueous environments. Fortunately, the porous architecture of MOF could confine CQDs to prevent ACQ and amplify fluorescence resonance effects [30]. Herein, we engineered a dual-emission ratiometric sensor by encapsulating o-phenylenediamine-derived CQDs into Uio-66-NH₂ (named Uio-66-NH₂@CQDs). The Uio-66-NH₂@CQDs composite exhibits AP-responsive fluorescence quenching at 430 nm and enhancing at 550 nm. This CQDs integrated in MOF design achieves rapid (< 2 min), interference-resistant AP detection with a detection limit of 175.6 nM, showing an outperforming conventional single-emission sensing in accuracy and environmental sample tolerance. Furthermore, we also studied the sensor’s portability and reusability, further underscoring its potential for on-site monitoring of AP contamination in industrial and ecological settings. Results and Discussion The synthesis procedure for Uio-66-NH 2 @CQDs is illustrated in Fig. 1. Yellow fluorescent CQDs were synthesized following a bottom-up approach from hydrothermal decomposition of o-phenylenediamine. Uio-66-NH 2 is obtained by mixing ZrCl 4 , NH 2 -BDC in DMF solution using a solvothermal method. Characterization of Uio-66-NH 2 @CQDs The powder XRD patterns of the Uio-66-NH 2 nanoparticles and Uio-66-NH 2 @CQDs composites are revealing in Fig. 2a. In the XRD pattern of Uio-66-NH 2 , the peaks at 7.4 ◦ and 8.5 ◦ corresponded to the crystal planes [111] and [200], respectively as reported in literature [34,35]. Both Uio-66-NH 2 and Uio-66-NH 2 @CQDs matches with the simulated XRD pattern of Uio-66. There is no extra peak found validating that the pure crystalline phase with Uio-66-NH 2 structure was successfully prepared via the present synthetic route. Even after increasing the carbon dot loading the composite frame work was not destroyed [36,37]. This validates that the encapsulation of CQDs has no effects on the lattice of Uio-66-NH 2 during the post-synthetic loading treatment seemingly because CQDs were embedded in the cavity instead of physically adsorption on the surface owing to the exceptional micropore structure of Uio-66-NH 2 . To get further evidence of the successful synthesis of Uio-66-NH 2 and Uio-66-NH 2 @CQDs and investigate their possible functional groups and chemical bonds, FTIR spectroscopy was accomplished Fig. 2b. The absorption bands at 663 cm -1 , 1386 cm -1 , and 1437/1571 cm -1 correspond to Zr-O, Zr-O-H, and C-O-Zr group vibration of Uio-66-NH 2 , respectively. Furthermore, Uio-66-NH 2 showed a transmittance peak at 1661 cm -1 attributed to C=O stretching in DMF. The FTIR spectrum of Uio-66-NH 2 @CQDs showed a wide band between 3050 and 3400 cm −1 , indicating the presence of amino and oxygen functional groups of Uio-66-NH 2 on its surface [38,39]. The transmission peak of DMF molecule at 1661 cm -1 in the Uio-66-NH 2 @CQDs spectrum disappears, indicating that the DMF molecule in the pores of the Uio-66-NH 2 network has been replaced by CQDs. Compared to Uio-66-NH 2 and CQDs, Uio-66-NH 2 @CQDs does not have significant CQDs peaks, further demonstrating that these CQDs are trapped in the pore channels of the frame without damaging their structure due to the shielding effect of 3D Uio-66-NH 2 [40,41]. The topography and surface composition of Uio-66-NH 2 @CQDs were investigated using scanning electron microscopy. The topography of the composite material did not change and the dimensions were less than 1 μm Fig. 2d. Trans­mission electron microscopy (TEM) was used to examine the presence of carbon quantum dots in Uio-66-NH 2 . The TEM image Fig. S1a shows that CQDs is well dispersed with an average transverse size of 2.56 nm. The high-resolution TEM image Fig. S1b of CQDs shows high-resolution lattice fringes, the spacing between the lattice fringes is about 0.103 nm. TEM results also indicated that spherical Uio-66-NH 2 @CQDs composite nanoparticles of size 2-3 nm have been formed with clearly visible pore channels Fig. 2c. Further the encapsulated CQDs in Uio-66-NH 2 clearly shows spherical. As further shown in Fig. 3a the XPS survey spectrum of Uio-66-NH 2 @CQDs showed four peaks at 284.8 eV for C 1s, 399.3 eV for N 1s, 531.7 eV for O 1s, and 182.3 eV for Zr3d, respectively. The XPS spectrum revealed that the composition of Uio-66-NH 2 @CQDs was C 60.87%, N 5.55%, and O 29.66% Zr 3.92%, indicating that Uio-66-NH 2 @CQDs were both carbon-rich and nitrogen-doped due to the addition of CQDs. A high-resolution C 1s spectrum Fig. 3b indicated the existences of C-C/C=C (284.36 eV), C=N (285.67 eV), and C=O (288.56 eV). A high-resolution N 1s spectrum Fig. 3c exhibited the presences of C-N-C (401.02 eV), N-H (399.91 eV), and Zr-N (398.93 eV). A high-resolution O 1s spectrum Fig. 3d showed two peaks at 531.75 eV of C-OH/C-O-C and 530.59 eV of C=O. A high-resolution Zr3d spectrum Fig. 3e showed two peaks at 181.4 eV for Zr 3d3/2 and 183.7 eV for Zr 3d5/2. The results of the FTIR were further confirmed by the XPS analysis. These results verified the successful doping of CQDs atoms in Uio-66-NH 2 @CQDs [42,43]. Construction of visual ratiometric fluorescence sensor of Uio-66-NH 2 @CQDs As shown in Fig. 4a, CQDs show excitation-dependent emission over the wavelength range (330-390 nm) with a maximum emission wavelength of 380 nm. In order to study the practicability of the probe, we added the probe to different solvents to compare its fluorescence intensity Fig. 4b, to evaluate the feasibility of the material as a fluorescent probe in an aqueous medium. Finally, we chose water as the solvent for detection. Water is the most common substance in life, and easy to obtain in experiment. The luminescence properties and structural stability of the material were further investigated, and the FL intensity of the Uio-66-NH 2 @CQDs probe under different pH values and different storage days was observed Fig. S3. Another important factor for a fluorescence sensor is selectivity, for which it is the prerequisite for testing analytes in real samples. Under the optimal conditions, effects of different material including metal ions and other ketones on Uio-66-NH 2 @CQDs sensor were separately studied. As illustrated in Figs. 4c-d, except for AP, metal ions, and similar compounds such as 2,5-dihy-droxyacetophenone, 3,4-dihydroxyacetophenone, 4-hydroxyacetophe-nones, 2-hydroxyacetophenones, 4-fluoroacetophenone, benzylacetone, and cyclopentanone, did not induce the above fluorescence changes. Other materials exert little influence on the fluorescence intensity ratio of Uio-66-NH 2 @CQDs sensor (I 430 /I 550 ), indicating that the sensor has good selectivity for AP. Then, sequential addition of AP is added to the aqueous solution of Uio-66-NH 2 @CQDs to assess the sensitivity of Uio-66-NH 2 @CQDs to AP under optimal conditions. As shown in Figs. 5a-b, as the AP concentration increases from 0 to 30 μL, the fluorescence intensity decreases at 430 nm and increases at 550 nm, and the fluorescence color changes from blue-green to yellow as shown in Fig. 5c. The ratio of the two signal intensities [I 430 /I 550 ] showed a good linear relationship with the AP concentration. [I 430 /I 550 ] = 1.317-0.03028X in the range of 0-30 μL (R 2 = 0.978) with a limit of detection (LOD) of 59.408 nM, based on the expression LOD = 3σ/k [44,45]. Quenching mechanism In order to study the sensing mechanism of Uio-66-NH 2 @CQDs on AP, the AP-treated Uio-66-NH 2 @CQDs samples were characterized by PXRD, FT-IR, FL, UV-VIS and other methods. PXRD spectra showed Fig. 6a that the structure of Uio-66-NH 2 @CQDs retained its original structure, indicating that the basic skeleton remained unchanged throughout sensing, which ruled out the possibility that structural changes could lead to changes in fluorescence. Then we delved into the interaction of Uio-66-NH 2 @CQDs with the AP Fig. 7a. Uio-66-NH 2 @CQDs showed two well-resolved emission peaks at 430 nm and 550 nm, which corresponded to CQDs and Uio-66-NH 2 , individually. The distinct shifted peak positions compared with individual CQDs and Uio-66-NH 2 may be attributed to their interaction in the nanocomposite form. Also, a slight red shift upon the addition of AP can be attributed to the dynamic attaching the AP to the nanocomposite. Upon the addition of AP to the Uio-66-NH 2 @CQDs solution, the fluorescence color changed under UV illumination, and yellow fluorescence emission was observed in the resulting suspension Figs. S5a-b. In order to gain a deeper understanding of the sensing mechanism of AP, we compared the fluorescence of the probe and the precipitate and the supernatant after the addition of AP, as shown in the Fig. S5c, the fluorescence peak of the supernatant at 550 nm may be due to the detachment of CQDs attached to the surface of Uio-66-NH 2 , but the fluorescence peak of the precipitate proves that the structure of CQDs inside it still exists, it is further proved that the quenching mechanism is not a possibility caused by structural changes. Fluorescence quenching of fluorophores has three widely accepted causes: static quenching, fluorescence resonance energy transfer (FRET), and internal filtration effect (IFE) [46]. A prerequisite for static quenching is the formation of ground-state complexes. As shown in Fig. 7b, there are no new absorption peaks other than the original characteristic absorption peaks of Uio-66-NH 2 @CQDs and AP, thus indicating that Uio-66-NH 2 @CQDs and AP do not form a ground-state complex, thus ruling out the possibility of static quenching. In addition, there is no overlap between the absorption of UV-vis from AP and the emission of Uio-66-NH 2 @CQDs, suggesting that FRET is not responsible for the change in fluorescence [47,48]. To further determine the fluorescence quenching mechanism of Uio-66-NH 2 @CQDs on AP, the lifetime of the Uio-66-NH 2 @CQDs and Uio-66-NH 2 @CQDs+AP emission peaks at 550 nm was also studied Fig. 6b. The results showed no significant change in the fluorescence lifetime of Uio-66-NH 2 @CQDs, ruling out the possibility of a dynamic quenching effect between the probe and the detection substrate. Therefore, the cascade sensing of AP is realized by IFE, that is, the competitive absorption of AP can cause the fluorescence quenching of Uio-66-NH 2 @CQDs to achieve quantitative detection of AP. Construction of sensing film for the detection of AP In addition, to avoid the problem of sensor failure caused by over-encapsulation, we preliminarily constructed the membrane by mixing the Uio-66-NH 2 @CQDs solution with an acetate membrane and drying it in air Fig. 8. The membrane is then applied to detect AP at different concentrations. Relative to the original blue-green fluorescence of the membrane, those exposed to different concentrations of AP experienced a continuous visible fluorescence color change that could be directly observed and further processed by smartphone. Extracting the RGB values on the output fluorescence image can directly determine the approximate concentration range of the AP and determine whether it is in the danger range. Once the fluorescence color of this film turns yellow, we should be vigilant and focus on monitoring and controlling whether the AP in the environment exceeds the standard. In addition, the ratio of (R/G/B) 0 /(R/G/B) i has a good linear relationship with AP concentrations in the range of 0-60 μL, with the corresponding linear equation being Y= 1.0122 - 0.01024 x (R 2 = 0.99214). At the same time, the LOD calculated by this formula is 175.6 nM. Therefore, a novel, simple, and intuitive method has been successfully established for the field, visualization, and semi-quantitative analysis of AP using Uio-66-NH 2 @CQDs paper-based sensors. This method is cost-effective, rapid, requires no preprocessing, and allows for convenient on-site analysis of AP in wastewater samples. Conclusion We constructed an AP-responsive fluorescent probe that can provide a fluorescence turn-on at 550 nm and turn-off at 430 nm. The fluorescence change was found to be highly selective for AP over other pollutants. The probe Uio-66-NH 2 @CQDs provided readily detectable fluorescence change to AP in the range of concentration, with a detection limit of 175.6 nM compatible with the environmental AP levels. Moreover, Uio-66-NH 2 @CQDs sensor was made for on-site, visual and semi-quantitative analysis of AP in simulates industrial wastewater by comparing the colors of standard and actual sample on Uio-66-NH 2 @CQDs paper-based sensor. Therefore, we proposed that Uio-66-NH 2 @CQDs can be applied for detection of traces of AP in real working environments due to its easy operational characteristics. This work could provide a new insight for exploring and utilizing of nanocomposites with promising potentials in continuous monitoring. Declarations Author Contributions Y.Z. Shou completed the experiments and wrote up the manuscript. W.J. Liu and J.K. Wang participated in the experiments and characterizations processes. 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Supplementary Files SupportingInformation.docx GraphicalAbstract.docx Cite Share Download PDF Status: Published Journal Publication published 17 Oct, 2025 Read the published version in Journal of Fluorescence → Version 1 posted Editorial decision: Revision requested 26 Aug, 2025 Reviews received at journal 25 Aug, 2025 Reviews received at journal 25 Aug, 2025 Reviewers agreed at journal 22 Aug, 2025 Reviewers agreed at journal 20 Aug, 2025 Reviewers invited by journal 20 Aug, 2025 Editor assigned by journal 18 Aug, 2025 Submission checks completed at journal 18 Aug, 2025 First submitted to journal 17 Aug, 2025 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. 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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-7393397","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":505841581,"identity":"17fee81b-773f-4cf7-976a-4711e6efcf29","order_by":0,"name":"Yongze Shou","email":"","orcid":"","institution":"Henan Polytechnic University","correspondingAuthor":false,"prefix":"","firstName":"Yongze","middleName":"","lastName":"Shou","suffix":""},{"id":505841582,"identity":"2066dfdd-6c66-438a-bbed-763d0cf3cfda","order_by":1,"name":"Zhouqing Xu","email":"","orcid":"","institution":"Henan Polytechnic University","correspondingAuthor":false,"prefix":"","firstName":"Zhouqing","middleName":"","lastName":"Xu","suffix":""},{"id":505841583,"identity":"2f229ba7-8ff3-41d5-8d35-9dc0068e393a","order_by":2,"name":"Huijun Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5klEQVRIiWNgGAWjYBACPmYeBoYEHjCb8TFELAG/FjYkLczGxGlh4EGwpYnTws57TOKBzOE8g/NrzKoLdxxm4GfPMWD4uQOfw/jSJBJ4DhdLznhjdnvmmcMMkj1vDBh7z+D1ixlIS2K/xBmz27xthxkMbuQYMDO2EaGlDailGKTFnmgt/fw9ZsxgWyQIazG2SOBJT5w5g61YmvdMOo/EmWcFB3vxaOHnP2N482ePdeKG84c3fubdYS3H35688cFPPFrAgLEHSEhkGDAwNkCi6QABDUDwA2Tf8QcgLaNgFIyCUTAKMAAAyPpIzLtorFoAAAAASUVORK5CYII=","orcid":"","institution":"Henan Polytechnic University","correspondingAuthor":true,"prefix":"","firstName":"Huijun","middleName":"","lastName":"Li","suffix":""},{"id":505841584,"identity":"ae7116ef-4d85-4c74-b793-32d826faa66a","order_by":3,"name":"Wenjie Liu","email":"","orcid":"","institution":"Henan Polytechnic University","correspondingAuthor":false,"prefix":"","firstName":"Wenjie","middleName":"","lastName":"Liu","suffix":""},{"id":505841585,"identity":"2aed4441-ae38-4b09-91a4-3735b47d667f","order_by":4,"name":"Junkun Wang","email":"","orcid":"","institution":"Henan Polytechnic University","correspondingAuthor":false,"prefix":"","firstName":"Junkun","middleName":"","lastName":"Wang","suffix":""}],"badges":[],"createdAt":"2025-08-17 15:53:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7393397/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7393397/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10895-025-04596-1","type":"published","date":"2025-10-17T15:58:16+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":90200845,"identity":"abf51f37-bcd7-4f2a-b505-25265265ae70","added_by":"auto","created_at":"2025-08-29 18:37:35","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":396825,"visible":true,"origin":"","legend":"\u003cp\u003eThe synthesis procedure for Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs\u003c/p\u003e","description":"","filename":"Figure1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7393397/v1/62197eddeb0abdd74a3f9847.jpeg"},{"id":90201445,"identity":"3a73aaea-b3e9-4149-9cd5-762fc8aba428","added_by":"auto","created_at":"2025-08-29 18:45:35","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1096040,"visible":true,"origin":"","legend":"\u003cp\u003e(a) XRD patterns of Uio-66, Uio-66-NH\u003csub\u003e2\u003c/sub\u003e, Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs. (b) FT-IR spectra of CQDs, Uio-66-NH\u003csub\u003e2\u003c/sub\u003e, Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs, Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQD of AP. (c) TEM images of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs. (d) Scanning electron microscopy (SEM) images of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs\u003c/p\u003e","description":"","filename":"Figure2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7393397/v1/81cdfe0a38e49c2f05b63ab1.jpeg"},{"id":90200846,"identity":"7eb3d965-1335-4310-9588-b02beec0a566","added_by":"auto","created_at":"2025-08-29 18:37:35","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":626234,"visible":true,"origin":"","legend":"\u003cp\u003e(a) XPS survey spectrum of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs, (b) XPS survey scan of C1s, (c) N1s, (d) O1s, (e) Zr3d\u003c/p\u003e","description":"","filename":"Figure3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7393397/v1/d5c1b47449d13343acce008a.jpeg"},{"id":90201446,"identity":"07db3b3f-1dc0-4bcd-aa84-5ba2e0750844","added_by":"auto","created_at":"2025-08-29 18:45:35","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":940356,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Emission spectra of CQDs under different excitations. (b) fluorescence spectra of the Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs probe under different solvents. (c) suspension-state photoluminescence spectra of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs in the presence of common cation anions and AP. (d) suspension-state photoluminescence spectra of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs in the presence of AP and other similar substances\u003c/p\u003e","description":"","filename":"Figure4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7393397/v1/10564420c046ae00c9e8cf43.jpeg"},{"id":90200853,"identity":"39059d37-7229-458b-81fc-deb6392a598d","added_by":"auto","created_at":"2025-08-29 18:37:35","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":200044,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Emission spectra and linear curves of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs at different concentrations of AP (0–30 μL). (b) I\u003csub\u003e430\u003c/sub\u003enm/I\u003csub\u003e550\u003c/sub\u003enm ratio SFS intensity against AP concentrations. (c) the corresponding fluorescence images of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs in the presences of different concentrations of AP under UV light\u003c/p\u003e","description":"","filename":"Figure5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7393397/v1/66bb577e73799f2138e5a0e7.jpeg"},{"id":90200863,"identity":"1282257f-dc10-4e39-8414-2273c2a71095","added_by":"auto","created_at":"2025-08-29 18:37:36","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":481073,"visible":true,"origin":"","legend":"\u003cp\u003e(a) PXRD pattern in the case of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs and Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs +AP. (b) Fluorescence lifetime of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs and Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs+AP at 550 nm\u003c/p\u003e","description":"","filename":"Figure6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7393397/v1/47ed9152d4349cff2d8006e4.jpeg"},{"id":90201451,"identity":"d427d0af-fe35-4583-85ee-76def7bbdf67","added_by":"auto","created_at":"2025-08-29 18:45:36","extension":"jpeg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":630939,"visible":true,"origin":"","legend":"\u003cp\u003e(a) The emission spectra of CQDs, Uio-66-NH\u003csub\u003e2\u003c/sub\u003e, AP and Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs nanocomposite alone and in the presence of AP. (b) UV absorption spectra and emission spectra of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs and UV absorption spectra of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs and Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs+AP and excitation spectra of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs+AP at 430 and 550 nm\u003c/p\u003e","description":"","filename":"Figure7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7393397/v1/d6b3c4ace6944348754e9b85.jpeg"},{"id":90200856,"identity":"7b67491a-a07c-4e1a-8bed-085e58c843a8","added_by":"auto","created_at":"2025-08-29 18:37:35","extension":"jpeg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":121208,"visible":true,"origin":"","legend":"\u003cp\u003eFabrication of paper-based sensing film and schematic diagram of smartphone AP and linear fitting curves of RGB from the APP of the paper-based sensor after the addition of different concentrations of AP\u003c/p\u003e","description":"","filename":"Figure8.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7393397/v1/860e749b1370946aaeae1f0a.jpeg"},{"id":93956202,"identity":"c8788f64-e37a-40fe-9a68-755755846d84","added_by":"auto","created_at":"2025-10-20 16:11:30","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5005229,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7393397/v1/ce4ec1a8-e310-4809-956b-3265a028722b.pdf"},{"id":90200852,"identity":"20dd7066-3d04-4bb6-bf7d-fe004f32bde0","added_by":"auto","created_at":"2025-08-29 18:37:35","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1335133,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-7393397/v1/0ff21af217bca8210e90ee48.docx"},{"id":90201877,"identity":"451fe4eb-5f2e-4fe2-b1bd-14011ad4d93f","added_by":"auto","created_at":"2025-08-29 19:01:35","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":337373,"visible":true,"origin":"","legend":"","description":"","filename":"GraphicalAbstract.docx","url":"https://assets-eu.researchsquare.com/files/rs-7393397/v1/3ad665501af018dee12000f5.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Dual-emission ratiometric fluorescent probe based on Uio-66- NH 2 @CQDs for quantitative detection of acetophenone","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe ever-increasing industrial production has led to a growing discharge of organic wastewater and various chemical wastes, causing increasingly severe environmental impacts and drawing significant attention in society [1,2]. Acetophenone (AP), which usually serves as an indispensable precursor in synthesizing pharmaceuticals, dyes and rubber additives, is a highly toxic and prevalent volatile organic compound [3-6]. Its improper management or potential AP leakage would pose significant environmental and health risks including respiratory distress, chronic cough, and skin cancer, and potentially trigger public health concerns [7,8]. Consequently, it is crucial to develop an efficient, rapid, and sensitive detection method of AP for environmental monitoring and public health protection [9,10]. Traditional analytical instrumentation techniques such as Raman spectroscopy, X-ray dispersion, ion mobility spectroscopy are reported to be used to detect and quantify the concentration of AP [11,12]. However, these methods either require skilled operators or tedious pre-treatment of samples. Integrating these methods into portable devices is difficult, which severely limits their application in field testing [13,14].\u003c/p\u003e\n\u003cp\u003eFluorescence spectroscopy has emerged as a transformative analytical tool, offering unparalleled sensitivity, real-time response, and non-destructive operation\u0026nbsp;[15,16]. Among fluorescent materials, metal-organic frameworks (MOF) stand out due to their structural programmability, permanent porosity, and host-guest recognition capabilities [17,18]. The matrix in MOF could act as a molecular sieve to preconcentrate target analytes via host-guest interactions (e.g., π-π stacking, hydrogen bonding), further enable analyte-specific fluorescence modulation through mechanisms such as energy transfer or electron exchange [19-21].\u003c/p\u003e\n\u003cp\u003eHowever, most reported MOF-based sensor are single-emission probes, which are inherently susceptible to environmental interference, leading to unreliable signals in complex matrices [22,23]. In this regard, ratiometric fluorescent sensors have the ability of calibrating against systemic errors by simultaneously tracking changes in two distinct emission bands, thereby enhancing accuracy and reproducibility [24,25]. Therefore, integrating other fluorescent molecules with L-MOFs to construct dual-emission ratiometric sensor is a suitable strategy, where analyte-induced differential quenched or enhanced emissions of fluorescent molecules and MOF cancels out matrix interference, achieving sub-ppm sensitivity and field-compatible robustness [26,27].\u003c/p\u003e\n\u003cp\u003eCarbon quantum dots (CQDs) captured researcher’s interest due to their tunable photoluminescence, exceptional photostability, and rapid (\u0026lt;1 min) analyte-responsive signal transitions mediated by electron transfer or surface interactions [28,29]. However, individual CQDs often face limitations in practical application due to non-specific binding and aggregation-induced quenching (ACQ) in aqueous environments. Fortunately, the porous architecture of MOF could confine CQDs to prevent ACQ and amplify fluorescence resonance effects [30].\u003c/p\u003e\n\u003cp\u003eHerein, we engineered a dual-emission ratiometric sensor by encapsulating o-phenylenediamine-derived CQDs into Uio-66-NH₂ (named Uio-66-NH₂@CQDs). The Uio-66-NH₂@CQDs composite exhibits AP-responsive fluorescence quenching at 430 nm and enhancing at 550 nm. This CQDs integrated in MOF design achieves rapid (\u0026lt; 2 min), interference-resistant AP detection with a detection limit of 175.6 nM, showing an outperforming conventional single-emission sensing in accuracy and environmental sample tolerance. Furthermore, we also studied the sensor’s portability and reusability, further underscoring its potential for on-site monitoring of AP contamination in industrial and ecological settings.\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cp\u003eThe synthesis procedure for Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs is illustrated in Fig. 1. Yellow fluorescent CQDs were synthesized following a bottom-up approach from hydrothermal decomposition of o-phenylenediamine. Uio-66-NH\u003csub\u003e2\u003c/sub\u003e is obtained by mixing ZrCl\u003csub\u003e4\u003c/sub\u003e, NH\u003csub\u003e2\u003c/sub\u003e-BDC in DMF solution using a solvothermal method.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCharacterization of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe powder XRD patterns of the Uio-66-NH\u003csub\u003e2\u003c/sub\u003e nanoparticles and Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs composites are revealing in Fig. 2a. In the XRD pattern of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e, the peaks at 7.4\u003csup\u003e◦\u003c/sup\u003e and 8.5\u003csup\u003e◦\u003c/sup\u003e corresponded to the crystal planes [111] and [200], respectively as reported in literature [34,35]. Both Uio-66-NH\u003csub\u003e2\u003c/sub\u003e and Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs matches with the simulated XRD pattern of Uio-66.\u0026nbsp;There is no extra peak found validating that the pure crystalline phase with Uio-66-NH\u003csub\u003e2\u003c/sub\u003e structure was successfully prepared via the present synthetic route. Even after increasing the carbon dot loading the composite frame work was not destroyed [36,37]. This validates that the encapsulation of CQDs has no effects on the lattice of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e during the post-synthetic loading treatment seemingly because CQDs were embedded in the cavity instead of physically adsorption on the surface owing to the exceptional micropore structure of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e\n\u003cp\u003eTo get further evidence of the successful synthesis of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e and Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs and investigate their possible functional groups and chemical bonds, FTIR spectroscopy was accomplished Fig. 2b. The absorption bands at 663 cm\u003csup\u003e-1\u003c/sup\u003e, 1386 cm\u003csup\u003e-1\u003c/sup\u003e, and 1437/1571 cm\u003csup\u003e-1\u003c/sup\u003e correspond to Zr-O, Zr-O-H, and C-O-Zr group vibration of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e, respectively. Furthermore, Uio-66-NH\u003csub\u003e2\u003c/sub\u003e showed a transmittance peak at 1661 cm\u003csup\u003e-1\u003c/sup\u003e attributed to C=O stretching in DMF. The FTIR spectrum of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs showed a wide band between 3050 and 3400 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e, indicating the presence of amino and oxygen functional groups of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e on its surface [38,39]. The transmission peak of DMF molecule at 1661 cm\u003csup\u003e-1\u003c/sup\u003e in the Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs spectrum disappears, indicating that the DMF molecule in the pores of the Uio-66-NH\u003csub\u003e2\u003c/sub\u003e network has been replaced by CQDs. Compared to Uio-66-NH\u003csub\u003e2\u003c/sub\u003e and CQDs, Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs does not have significant CQDs peaks, further demonstrating that these CQDs are trapped in the pore channels of the frame without damaging their structure due to the shielding effect of 3D Uio-66-NH\u003csub\u003e2\u003c/sub\u003e [40,41].\u003c/p\u003e\n\u003cp\u003eThe topography and surface composition of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs were investigated using scanning electron microscopy. The topography of the composite material did not change and the dimensions were less than 1 \u0026mu;m Fig. 2d. Trans\u0026shy;mission electron microscopy (TEM) was used to examine the presence of carbon quantum dots in Uio-66-NH\u003csub\u003e2\u003c/sub\u003e. The TEM image Fig. S1a shows that CQDs is well dispersed with an average transverse size of 2.56 nm. The high-resolution TEM image Fig. S1b of CQDs shows high-resolution lattice fringes, the spacing between the lattice fringes is about 0.103 nm. TEM results also indicated that spherical Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs composite nanoparticles of size 2-3 nm have been formed with clearly visible pore channels Fig. 2c. Further the encapsulated CQDs in Uio-66-NH\u003csub\u003e2\u003c/sub\u003e clearly shows spherical.\u003c/p\u003e\n\u003cp\u003eAs further shown in Fig. 3a the XPS survey spectrum of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs showed four peaks at 284.8 eV for C 1s, 399.3 eV for N 1s, 531.7 eV for O 1s, and 182.3 eV for Zr3d, respectively.\u0026nbsp;The XPS spectrum revealed that the composition of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs was C 60.87%, N 5.55%, and O 29.66% Zr 3.92%, indicating that Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs were both carbon-rich and nitrogen-doped due to the addition of CQDs.\u0026nbsp;A high-resolution C 1s spectrum Fig. 3b indicated the existences of C-C/C=C (284.36 eV), C=N (285.67 eV), and C=O (288.56 eV).\u0026nbsp;A high-resolution N 1s spectrum Fig. 3c exhibited the presences of C-N-C (401.02 eV), N-H (399.91 eV), and Zr-N (398.93 eV).\u0026nbsp;A high-resolution O 1s spectrum Fig. 3d showed two peaks at 531.75 eV of C-OH/C-O-C and 530.59 eV of C=O. A high-resolution Zr3d spectrum Fig. 3e showed two peaks at 181.4 eV for Zr 3d3/2 and 183.7 eV for Zr 3d5/2. The results of the FTIR were further confirmed by the XPS analysis. These results verified the successful doping of CQDs atoms in Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs [42,43].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConstruction of visual ratiometric fluorescence sensor of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAs shown in Fig. 4a, CQDs show excitation-dependent emission over the wavelength range (330-390 nm) with a maximum emission wavelength of 380 nm. In order to study the practicability of the probe, we added the probe to different solvents to compare its fluorescence intensity Fig. 4b, to evaluate the feasibility of the material as a fluorescent probe in an aqueous medium. Finally, we chose water as the solvent for detection. Water is the most common substance in life, and easy to obtain in experiment. The luminescence properties and structural stability of the material were further investigated, and the FL intensity of the Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs probe under different pH values and different storage days was observed Fig. S3.\u003c/p\u003e\n\u003cp\u003eAnother important factor for a fluorescence sensor is selectivity, for which it is the prerequisite for testing analytes in real samples. Under the optimal conditions, effects of different material including metal ions and other\u0026nbsp;ketones on Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs sensor were separately studied. As illustrated in Figs. 4c-d, except for AP, metal ions, and similar compounds such as 2,5-dihy-droxyacetophenone, 3,4-dihydroxyacetophenone, 4-hydroxyacetophe-nones, 2-hydroxyacetophenones, 4-fluoroacetophenone, benzylacetone, and cyclopentanone, did not induce the above fluorescence changes. Other materials exert little influence on the fluorescence intensity ratio of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs sensor (I\u003csub\u003e430\u003c/sub\u003e/I\u003csub\u003e550\u003c/sub\u003e), indicating that the sensor has good selectivity for AP.\u003c/p\u003e\n\u003cp\u003eThen, sequential addition of AP is added to the aqueous solution of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs to assess the sensitivity of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs to AP under optimal conditions. As shown in Figs. 5a-b, as the AP concentration increases from 0 to 30 \u0026mu;L, the fluorescence intensity decreases at 430 nm and increases at 550 nm, and the fluorescence color changes from blue-green to yellow as shown in Fig. 5c. The ratio of the two signal intensities [I\u003csub\u003e430\u003c/sub\u003e/I\u003csub\u003e550\u003c/sub\u003e] showed a good linear relationship with the AP concentration. [I\u003csub\u003e430\u003c/sub\u003e/I\u003csub\u003e550\u003c/sub\u003e] = 1.317-0.03028X in the range of 0-30 \u0026mu;L (R\u003csup\u003e2\u003c/sup\u003e = 0.978) with a limit of detection (LOD) of 59.408 nM, based on the expression LOD = 3\u0026sigma;/k [44,45].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eQuenching mechanism\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn order to study the sensing mechanism of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs on AP, the AP-treated Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs samples were characterized by PXRD, FT-IR, FL, UV-VIS and other methods. PXRD spectra showed Fig. 6a that the structure of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs retained its original structure, indicating that the basic skeleton remained unchanged throughout sensing, which ruled out the possibility that structural changes could lead to changes in fluorescence.\u003c/p\u003e\n\u003cp\u003eThen we delved into the interaction of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs with the AP Fig. 7a. Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs showed two well-resolved emission peaks at 430 nm and 550 nm, which corresponded to CQDs and Uio-66-NH\u003csub\u003e2\u003c/sub\u003e, individually. The distinct shifted peak positions compared with individual CQDs and Uio-66-NH\u003csub\u003e2\u003c/sub\u003e may be attributed to their interaction in the nanocomposite form. Also, a slight red shift upon the addition of AP can be attributed to the dynamic attaching the AP to the nanocomposite. Upon the addition of AP to the Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs solution, the fluorescence color changed under UV illumination, and yellow fluorescence emission was observed in the resulting suspension Figs. S5a-b. In order to gain a deeper understanding of the sensing mechanism of AP, we compared the fluorescence of the probe and the precipitate and the supernatant after the addition of AP, as shown in the Fig. S5c, the fluorescence peak of the supernatant at 550 nm may be due to the detachment of CQDs attached to the surface of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e, but the fluorescence peak of the precipitate proves that the structure of CQDs inside it still exists, it is further proved that the quenching mechanism is not a possibility caused by structural changes.\u003c/p\u003e\n\u003cp\u003eFluorescence quenching of fluorophores has three widely accepted causes: static quenching, fluorescence resonance energy transfer (FRET), and internal filtration effect (IFE) [46]. A prerequisite for static quenching is the formation of ground-state complexes. As shown in Fig. 7b, there are no new absorption peaks other than the original characteristic absorption peaks of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs and AP, thus indicating that Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs and AP do not form a ground-state complex, thus ruling out the possibility of static quenching. In addition, there is no overlap between the absorption of UV-vis from AP and the emission of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs, suggesting that FRET is not responsible for the change in fluorescence [47,48].\u003c/p\u003e\n\u003cp\u003eTo further determine the fluorescence quenching mechanism of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs on AP, the lifetime of the Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs and Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs+AP emission peaks at 550 nm was also studied Fig. 6b. The results showed no significant change in the fluorescence lifetime of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs, ruling out the possibility of a dynamic quenching effect between the probe and the detection substrate.\u0026nbsp;Therefore, the cascade sensing of AP is realized by IFE, that is, the competitive absorption of AP can cause the fluorescence quenching of Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs to achieve quantitative detection of AP.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConstruction of sensing film for the detection of AP\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn addition, to avoid the problem of sensor failure caused by over-encapsulation, we preliminarily constructed the membrane by mixing the Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs solution with an acetate membrane and drying it in air Fig. 8. The membrane is then applied to detect AP at different concentrations. Relative to the original blue-green fluorescence of the membrane, those exposed to different concentrations of AP experienced a continuous visible fluorescence color change that could be directly observed and further processed by smartphone. Extracting the RGB values on the output fluorescence image can directly determine the approximate concentration range of the AP and determine whether it is in the danger range. Once the fluorescence color of this film turns yellow, we should be vigilant and focus on monitoring and controlling whether the AP in the environment exceeds the standard.\u0026nbsp;In addition, the ratio of (R/G/B)\u003csub\u003e0\u003c/sub\u003e/(R/G/B)\u003csub\u003ei\u003c/sub\u003e has a good linear relationship with AP concentrations in the range of 0-60 \u0026mu;L, with the corresponding linear equation being Y= 1.0122 - 0.01024 x (R\u003csup\u003e2\u003c/sup\u003e = 0.99214). At the same time, the LOD calculated by this formula is 175.6 nM.\u003c/p\u003e\n\u003cp\u003eTherefore, a novel, simple, and intuitive method has been successfully established for the field, visualization, and semi-quantitative analysis of AP using Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs paper-based sensors. This method is cost-effective, rapid, requires no preprocessing, and allows for convenient on-site analysis of AP in wastewater samples.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eWe constructed an AP-responsive fluorescent probe that can provide a fluorescence turn-on at 550 nm and turn-off at 430 nm. The fluorescence change was found to be highly selective for AP over other pollutants. The probe Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs provided readily detectable fluorescence change to AP in the range of concentration, with a detection limit of 175.6 nM compatible with the environmental AP levels. Moreover, Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs sensor was made for on-site, visual and semi-quantitative analysis of AP in simulates industrial wastewater by comparing the colors of standard and actual sample on Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs paper-based sensor. Therefore, we proposed that Uio-66-NH\u003csub\u003e2\u003c/sub\u003e@CQDs can be applied for detection of traces of AP in real working environments due to its easy operational characteristics. This work could provide a new insight for exploring and utilizing of nanocomposites with promising potentials in continuous monitoring.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eY.Z. Shou\u0026nbsp;\u003c/strong\u003ecompleted the experiments and wrote up the manuscript. \u003cstrong\u003eW.J. Liu\u003c/strong\u003e and \u003cstrong\u003eJ.K. Wang\u003c/strong\u003e participated in the experiments and characterizations processes. \u003cstrong\u003eH.J. Li\u0026nbsp;\u003c/strong\u003eand \u003cstrong\u003eZ.Q. Xu\u0026nbsp;\u003c/strong\u003eprovided the project administration and revised the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThere are no conflicts to declare.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Innovative research team of Henan Polytechnic University (T2023-6), the Youth Exploration Fund of Henan Polytechnic University (NSFRF210330).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInnovative research team of Henan Polytechnic University, (T2023-6). Youth Exploration Fund of Henan Polytechnic University, (NSFRF210330).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eRobertson PA, Bishop HM, Orr-Ewing AJ (2021) Tuning the excited-state dynamics of acetophenone using metal ions in solution. J Phys Chem Lett 12:5473\u0026ndash;5478\u003c/li\u003e\n \u003cli\u003eChen DJ, Huo SH, Cheng PF, Cheng YL, Zhou N, Chen P, Wang YP, Li K, Peng P, Ruan R (2021) Treatment and nutrient recovery from acetophenone based wastewater by an integrated catalytic intense pulsed light and Tribonema sp. Cultivation. Chem Eng Process Process Intensif 160:108276\u003c/li\u003e\n \u003cli\u003eLi B, Mi CW (2021) On the chirality-dependent adsorption behavior of volatile organic compounds on carbon nanotubes. 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Macromolecules 52:8643\u0026ndash;8650\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":"journal-of-fluorescence","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jofl","sideBox":"Learn more about [Journal of Fluorescence](https://www.springer.com/journal/10895)","snPcode":"10895","submissionUrl":"https://submission.nature.com/new-submission/10895/3","title":"Journal of Fluorescence","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Uio-66-NH2@CQDs, AP sensing, Ratiometric sensor, Fluorescence detection","lastPublishedDoi":"10.21203/rs.3.rs-7393397/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7393397/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"It is imperative that developing fluorescent probe to detect volatile organic compound such as acetophenone (AP) to protect environment public health protection. In this work, we synthesized a ratiometric Uio-66-NH2@CQDs sensor through post-synthetic modification by anchoring carbon quantum dots onto Uio-66-NH2 metal-organic framework, which could be readily utilized as self-calibrating nanoprobe for selective detection of AP over other potential interferants. Upon the addition of AP, Uio-66-NH2@CQDs featured a decreased emision at 430 nm and an enhanced emission at 550 nm, accompanied by a characteristic fluorescence color transition from blue-green to yellow. By adopting the ration of I430nm/I550nm as the detection signal, Uio-66-NH2@CQDs could distinguish AP with excellent performance. The limit of detection for AP was estimated to be 175.6 nM, which was a significant value. Additionally, we demonstrated that on-site visual inspection of AP in industrial wastewater using a paper-based Uio-66-NH2@CQDs analysis device.","manuscriptTitle":"Dual-emission ratiometric fluorescent probe based on Uio-66- NH 2 @CQDs for quantitative detection of acetophenone","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-29 18:37:31","doi":"10.21203/rs.3.rs-7393397/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-08-26T12:44:58+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-25T15:24:55+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-25T06:30:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"261568620007779831526874735213211369855","date":"2025-08-22T12:20:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"147290958306772870958445061625842952715","date":"2025-08-20T12:35:49+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-20T12:13:58+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-18T17:22:55+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-08-18T17:22:07+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Fluorescence","date":"2025-08-17T15:45:14+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-fluorescence","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jofl","sideBox":"Learn more about [Journal of Fluorescence](https://www.springer.com/journal/10895)","snPcode":"10895","submissionUrl":"https://submission.nature.com/new-submission/10895/3","title":"Journal of Fluorescence","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"867b5f04-7cbe-4c02-ae41-bd0f77b1fbb8","owner":[],"postedDate":"August 29th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-10-20T16:07:20+00:00","versionOfRecord":{"articleIdentity":"rs-7393397","link":"https://doi.org/10.1007/s10895-025-04596-1","journal":{"identity":"journal-of-fluorescence","isVorOnly":false,"title":"Journal of Fluorescence"},"publishedOn":"2025-10-17 15:58:16","publishedOnDateReadable":"October 17th, 2025"},"versionCreatedAt":"2025-08-29 18:37:31","video":"","vorDoi":"10.1007/s10895-025-04596-1","vorDoiUrl":"https://doi.org/10.1007/s10895-025-04596-1","workflowStages":[]},"version":"v1","identity":"rs-7393397","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7393397","identity":"rs-7393397","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}