Tetrakis(4-pyridylphenyl)ethylene-decorated metal–organic frameworks with aggregation induced chemiluminescence emission on paper-based paltform for volatile sulfur compounds measurement

Tetrakis(4-pyridylphenyl)ethylene-decorated metal–organic frameworks with aggregation induced chemiluminescence emission on paper-based paltform for volatile sulfur compounds measurement | 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 Tetrakis(4-pyridylphenyl)ethylene-decorated metal–organic frameworks with aggregation induced chemiluminescence emission on paper-based paltform for volatile sulfur compounds measurement Huaqin Shui, Yanli Guo, Jingbo Geng, Qing Chang, Yuxin Tian, Xue Du, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7195328/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 03 Dec, 2025 Read the published version in Microchimica Acta → Version 1 posted 10 You are reading this latest preprint version Abstract Volatile sulfur compounds (VSCs) in human exhaled breath (EB) are considered as biomarkers of halitosis. Convenient and reliable detection of VSCs has significance for confirming oral health. Herein, copper-based metal-organic framework (Cu-TPPE) was synthesized by utilizing aggregation-induced emission (AIE) phenomenon of tetrakis(4-pyridylphenyl)ethylene (TPPE) ligand on paper. Due to electron transfer between Cu 2+ and TPPE, the aggregation-induced emission of TPPE was quenched. In the presence of VSCs, the affinity between S and Cu led to delocalization of Cu in Cu-TPPE, thus recovering the aggregation-induced chemiluminescence emission (AICE) between TPPE and bis(2,4,6-trichlorophenyl)oxalate (TCPO)-H 2 O 2 . Based on this principle, selective and sensitive determination of VSCs in human EB was achieved. Quantification linear range of H 2 S was 0.07-8.0 ppm, and the detection limit was 0.03 ppm. This paper-based chemiluminescence (CL) platform has been applied to the detection of VSCs in real breath samples. Volatile sulfur compounds tetrakis(4-pyridylphenyl)ethylene Aggregation-induced emission Chemiluminescence Exhaled breath Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Human exhaled breath (EB) contains about 3000 volatile organic compounds (VOCs), some of which are related to metabolic conditions.[ 1 ] For example, isoprene, aldehydes and acetone in EB are indicators of cardiovascular disease[ 2 ], lung cancer[ 3 ] and diabetes[ 4 ], respectively. Volatile sulfur compounds (VSCs) in EB, including hydrogen sulfide (H 2 S), methyl mercaptan (CH 4 S) and dimethyl sulfide (C 2 H 6 S), are generated when oral bacteria degrades sulfur-containing amino acids (such as cysteine and methionine),[ 5 ] so VSCs in human exhalation are regarded as markers of halitosis.[ 6 ] Exhaled H 2 S of halitosis patients exceeds 2 ppm, which is 3–4 times higher than healthy people.[ 7 ] Halitosis is associated with gingivitis and periodontitis,[ 8 ] so detection of VSCs in breath is of significance for disease screening. Currently, gas chromatography-mass spectrometry (GC-MS)[ 9 ], colorimetric sensor[ 10 ] and electrochemical gas sensor[ 11 ] have been used to analyze VSCs in EB. However, GC-MS is time-consuming and expensive, thus it is not convenient for large-scale application. Colorimetric sensor does not have complex circuits, but it features low sensitivity and response speed. Electrochemical gas sensor is highly sensitive, but it usually works at high temperature and thus is not convenient for on-site diagnosis of halitosis. Therefore, establishing an accurate, low-cost and portable VSCs analysis platform is of great significance for the assessment of halitosis. EB contains various VOCs, while the content of H 2 S in EB is ppm level,[ 1 , 7 ] so metal-organic frameworks (MOFs) with large surface area and high porosity were used to adsorb and enrich VSCs. As CuS can be formed between Cu and sulfur-containing compounds, Cu-based MOFs such as Cu-TATB[ 10 ] and Cu-BTC[ 12 ] have been used for selective capture and sensing of H 2 S. If MOFs are loaded on flexible paper, resulting paper-based analysis platform will have advantages of both portable and sensitive. However, the fluorescence (FL) of traditional luminescent MOFs is quenched in solid state, so this work chose MOF with aggregation-induced emission (AIE) effect to adsorb, capture and sense VSCs in EB. Among various ligands of MOFs with AIE property, tetraphenylethene (TPE) and its derivatives such as tetrakis(4-pyridylphenyl)ethylene (TPPE) have been widely used to prepare MOFs with AIE characteristics due to simple synthesis and good stability.[ 13 ] Therefore, in this paper, Cu-TPPE was synthesized and loaded on paper for selective capture and sensing of VSCs in EB. Nowadays, investigation of MOFs with AIE effect usually focused on FL method.[ 14 ] Since Lv's group[ 15 ] combined the AIE phenomenon of Au NCs aggregates with chemiluminescence (CL) of bis(2,4,6-trichlorophenyl)oxalate (TCPO)-H 2 O 2 , reports about aggregation-induced chemiluminescence emission (AICE) gradually appeared. For example, Li's team[ 16 ] prepared a covalent organic framework with AIE property (TPE@SNW − 1 ) by combining TPE with a Schiff base network (SNW − 1 ). Using TPE@SNW − 1 as energy acceptor and TCPO-H 2 O 2 as energy donor, chemiluminescent resonance energy transfer (CRET) system was designed. The linear range of H 2 O 2 was 5.0-1000.0 µM with the detection limit of 2.34 µM. Based on generated H 2 O 2 when uric acid was catalyzed by uricase, uric acid in human serum samples can be determined with the linear range of 10.0-150.0 µM and the detection limit of 4.94 µM. CL technology has the advantages of simple device, high sensitivity, wide linear range and low background.[ 17 ] Although there have been reports on the determination of sulfur-containing compounds by CL method, CL analysis of H 2 S was often based on inhibited CL signal by H 2 S,[ 10 , 18 ] and until now, no report on the detection of VSCs based on AICE was found. Therefore, it is necessary to develop aggregation-induced chemiluminescence enhancement method to detect VSCs in EB. Herein, Cu-TPPE was prepared using TPPE with AIE effect as ligand. A paper-based sensor (Cu-TPPE@paper) was designed by loading Cu-TPPE on paper. The valence electron of Cu 2+ was 3d 9 , so electron transfer between Cu 2+ and TPPE can occur, thus Cu-TPPE had almost no aggregation-induced luminescence. However, in the presence of VSCs, the affinity between S and Cu led to delocalization of Cu in Cu-TPPE, thus recovering FL of TPPE.[ 19 ] TPPE was aggregated on paper. Aggregated TPPE with AIE property and TCPO-H 2 O 2 donor can trigger CRET, so AICE was produced. In this way, VSCs in EB can be detected based on enhanced CL signals. Scheme 1 showed the sensing principle of VSCs by Cu-TPPE and TCPO-H 2 O 2 system. This paper-based CL sensor was accurate and sensitive, promising to screen patients with oral diseases from healthy people. Experimental section Materials and Reagents Tetrakis(4-pyridylphenyl)ethylene (TPPE) was purchased from Alpha Chemical Reagents Co., Ltd. (Zhengzhou, China). Sodium hydrosulfide hydrate (NaHS∙xH 2 O), phosphate, dimethyl sulfide (C 2 H 6 S), copper (II) chloride dehydrate (CuCl 2 ∙2H 2 O), tetrachloroethene, bis(2,4,6-trichlorophenyl)oxalate (TCPO), formaldehyde, acetaldehyde, ammonium chloride, sodium hydrogen sulfite and sodium carbonate were obtained from Aladdin Reagents Co., Ltd. (Shanghai, China). Methyl mercaptan (CH 4 S) was from Sigma Co., Ltd. (USA). Methanol, ethanol, isopropanol, acetone, toluene, hydrogen peroxide aqueous solution (H 2 O 2 , 30wt%), sodium hydroxide, hydrochloric acid (36–38%) and potassium bromide were provided by Sinopharm Chemical Reagents Co., Ltd. (Shanghai, China). 5 mM TCPO solution was prepared by dissolving TCPO into acetone. The water used in this work was secondary ultra-pure water (18.2 MΩ cm). Whatman chromatography paper #1 was purchased from Sigma Co., Ltd. (USA). Teflon gas sampling bag was from Zhanhai Co., Ltd. (China). Instrumentations SU8220 scanning electron microscopy (SEM) and F-7000 fluorescence spectrometer were purchased from Hitachi Instruments Co., Ltd., Kyoto, Japan. D8 advance X-ray diffractometer (XRD) and Prestige-21 Fourier transform infrared (FTIR) spectrometer were from Bruker Instruments Co., Ltd., Germany. Brunauer-Emmett-Teller (BET) test was performed on ASAP2020 (Micromeritics, USA). CL tests were performed on a model IFFS-A CL analyzer and the data were obtained by RFL-1 software (Remex Electronic Sci. Tech. Co. Ltd., China). 4-20R bench high speed refrigerated centrifuge was from Henuo Instrument Equipment Co., Ltd., Hunan. DZF-6030A electric blast drying oven was purchased from Yiheng Scientific Instrument Co., Ltd., Shanghai. AL204-IC electronic analytical balance was obtained from Mettler Toledo Instrument Co., Ltd., Switzerland. 1810B ultra-pure water machine and KH5200E ultrasonic cleaner were from Chongqing Moore Water Treatment Equipment Co., Ltd and Hechuang Ultrasonic Instrument Co., Ltd., Kunshan, respectively. Synthesis of Cu-TPPE Powder and Preparation of Cu-TPPE@paper Cu-TPPE powder was synthesized according to the work of Latham’s group with small modifications.[ 20 ] First, 27.2 mg CuCl 2· 2H 2 O was dissolved in 10 mL CH 3 OH, and 25 mg TPPE was dissolved in a mixture of 11.25 mL CCl 2 = CCl 2 and 3.75 mL CH 3 OH. Then, the CuCl 2 solution was gently poured into the above TPPE solution and left at room temperature for 3 d. Finally, Cu-TPPE powder was obtained by vacuum drying of green crystals at 55 ℃ for 4 h. Cu-TPPE@paper was fabricated by loading 10 µ L 0.1 g·mL -1 Cu-TPPE ethanol solution onto paper. Generation of Standard Gas H 2 S is a binary weak acid with pK a 1 = 6.76 at 37 ℃. When pH < 6, sulfides can be considered to be entirely in the form of H 2 S.[ 21 ] Therefore, different concentrations of H 2 S standard gas can be prepared by acidifying different concentrations of NaHS solution with 85% H 3 PO 4 . For accurately controlling gas volume, resealable Teflon bag (200 mL) was used. After filling the bag with nitrogen, NaHS and H 3 PO 4 solutions were injected successively. The Teflon bag was placed at 37℃ for 2 h to obtain homogeneous volatile H 2 S. The generation of CH 4 S and C 2 H 6 S standard gases was in the similar way. Detection of VSCs with Cu-TPPE@paper Analysis procedure of VSCs by CL method was as follows. First, Cu-TPPE@paper was placed into a Teflon bag with a cutting incision. Then, tape was used to seal the cutting incision, and the air in the bag was driven out with a vacuum pump.[ 10 ] Next, the standard gas prepared above was transferred to this bag. After sensing for 40 min, Cu-TPPE@paper was taken out from the bag and was put into CL analyzer. Finally, TCPO and H 2 O 2 were introduced to Cu-TPPE@paper to obtain CL signal. The detection of CH 4 S and C 2 H 6 S was in the similar way. Determination of VSCs in Human Exhaled Breath Samples Breath samples collected from three healthy volunteers without oral diseases from Shaanxi Normal University. Before breath sampling, to avoid exogenous interfering gases, the volunteers should not eat and needed to rest for 10 min in a well-ventilated room.[ 22 ] When collecting the exhalation, the volunteers breathed deeply and exhaled into a Teflon bag with Cu-TPPE@paper in it. After sensing for 40 min, Cu-TPPE@paper was removed from the bag and then TCPO-H 2 O 2 was introduced to obtain CL response. Results and discussion Characterization of Cu-TPPE The synthesized Cu-TPPE was characterized by the following protocols. The morphology of green Cu-TPPE was investigated by TEM. Figure 1 A showed Cu-TPPE sheets had a size of about 100 nm. In Fig. 1 B, powder X-ray diffraction (PXRD) pattern of the synthesized Cu-TPPE was consistent with the work of Latham’s team,[ 20 ] indicating that Cu-TPPE was successfully prepared. For the FTIR spectrum of Cu-TPPE (Fig. 1 C), the peaks at 1557 cm − 1 and 1115 cm − 1 belonged to C = C bending vibrations and C-H in-plane vibrations of phenyl ring, respectively.[ 23 , 24 ] The absorption peak at 1487 cm − 1 corresponded to stretching vibrations of benzene ring, and the peak at 1605 cm − 1 was assigned to the pyridine group of the TPPE ligand.[ 25 ] The FTIR peaks at 650–910 cm − 1 in the fingerprint region reflected the different substitutions of aromatic ring. The N 2 adsorption isotherm of Cu-TPPE exhibited type I and its Langmuir surface area was 101.4 m 2 /g (Fig. 1 D), indicating that gaseous H 2 S can be adsorbed by Cu-TPPE. Aggregation Behaviors of Cu-TPPE and TPPE on paper According to previous reports, TPPE with AIE effect was used as ligand to prepare MOFs, the synthesized MOFs still exhibited AIE property,[ 25 ] and AIE phenomenon can be produced when they were in solid state.[ 26 ] Therefore, in this work, Cu-TPPE using TPPE as ligand was loaded onto solid-phase paper to investigate its luminescence performance. By comparing the SEM of Cu-TPPE powder in Fig. 1 A, it was found that Cu-TPPE was aggregated on paper with an average size of 10 µ m (Fig. 2 A). However, Cu-TPPE emitted almost no FL because the 3d 9 valence electron of Cu 2+ induced electron transfer between Cu 2+ and TPPE. Therefore, the FL of Cu-TPPE ethanol solution and Cu-TPPE@paper were weak (Fig. 2 B). Next, TPPE ligand with AIE effect on paper was studied. The SEM in Fig. 3 A showed that TPPE was also aggregated on paper with a size of about 20 µ m, while TPPE powder itself was columnar with an average length of 10 µ m and a width of 2 µ m (Fig. 3 B). The FL intensity of TPPE@paper was significantly increased compared to TPPE ethanol solution (Fig. 3 C), suggesting that AIE phenomenon can be easily produced by loading AIE molecules onto paper. TCPO-H 2 O 2 system is a commonly used CL system. Based on CRET between TCPO-H 2 O 2 and fluorescent molecules, various substances have been detected.[ 16 ] Introducing TCPO-H 2 O 2 into TPPE solution and TPPE@paper, CL comparison results illustrated that TPPE@paper can cause TCPO-H 2 O 2 to produce strong CL (Fig. 3 D), which further showed that TPPE@paper can trigger AICE phenomenon. The CL Mechanism of TPPE-TCPO-H 2 O 2 System As mentioned above, TPPE@paper can trigger TCPO-H 2 O 2 to produce strong CL. The CL mechanism of TPPE-TCPO-H 2 O 2 system was investigated. As shown in Fig. S1 A, the CL spectrum peak of TCPO-H 2 O 2 system was at 450 nm, which overlapped the FL excitation spectrum of TPPE in Fig. S1 B (Fig. S1 C). The CL spectrum peak of TPPE-TCPO-H 2 O 2 system was located at 470 nm (Fig. S1 D), which was corresponded to the FL emission wavelength of TPPE (Fig. S1 B). Above results showed that CRET occurred between TCPO-H 2 O 2 and TPPE acceptor, and the emitting species of TPPE-TCPO-H 2 O 2 system was excited-state TPPE. Only the energy transfer between TCPO-H 2 O 2 and TPPE can be confirmed by the experimental result that TPPE-TCPO-H 2 O 2 had no UV-Vis new peaks compared with TPPE and TCPO (Fig. S1 E). Therefore, the possible CL mechanism of TPPE-TCPO-H 2 O 2 system was as follows. TCPO was oxidized by H 2 O 2 to generate high-energy 1,2-dioxetane intermediate, then its energy was transferred to TPPE to form excited TPPE, and CL was produced when excited TPPE returned to the ground state (Scheme 2 ).[ 27 ] The Principle of Sensing VSCs with Cu-TPPE@paper Designed Cu-TPPE@paper was used to detect VSCs. As mentioned above, although Cu-TPPE was aggregated on paper, Cu (Ⅱ)-induced electron transfer led to emitting almost no FL of aggregated Cu-TPPE on paper.[ 19 ] However, VSCs caused Cu delocalization in Cu-TPPE due to the affinity between S and Cu, thus turning on FL of aggregated TPPE. This sensing principle can be verified by comparing pictures of Cu-TPPE@paper before and after adsorbing 10 ppm H 2 S under natural and 365 nm UV light. As shown in Fig. 4 A, Cu-TPPE@paper appeared green. Yellow TPPE appeared after response to H 2 S. When irradiating above papers by 365 nm UV lamp, the FL of Cu-TPPE@paper exposed to H 2 S was much stronger (Fig. 4 B). Above results confirmed the delocalization of Cu in Cu-TPPE and the aggregation of TPPE on paper. Compared with FL method, CL technology had lower background, so both analysis methods for determination of 1 ppm H 2 S were compared here. In Fig. 5 A, the signal-to-noise ratio (S/N) of sensing H 2 S using Cu-TPPE@paper by FL method was 7.8, while the S/N of CL method was 19.8 (Fig. 5 B), indicating that CL method had advantage over FL method for detecting H 2 S. To illustrate the advantages of the paper-based analysis platform, the S/N of sensing H 2 S in solution and on paper via CL technology was compared. The results in Fig. 5 C demonstrated that detecting H 2 S on paper was more sensitive, which may be because TPPE generated by Cu delocalization was aggregated on paper. Therefore, CL method and Cu-TPPE@paper were chosen for detecting VSCs. Optimization of VSCs Detection Conditions To explore the optimal conditions for detection of VSCs, optimization experiments were carried out. First, the concentrations of TCPO and H 2 O 2 were optimized. Due to the weak FL of Cu-TPPE@paper, 1 ppm H 2 S was adsorbed for 30 min to provide detectable CL signals. The best detection performances were obtained when the concentrations of TCPO and H 2 O 2 were 2.5 mM (Fig. S2A) and 0.1 M (Fig. S2B), respectively. It took time for H 2 S to enter the pore of Cu-TPPE and the reaction of Cu and S, so the adsorption time of H 2 S was optimized. The result in Fig. S2C showed that 40 min was suitable for H 2 S determination. AICE Detection of VSCs Cu-TPPE@paper was used for CL detection of VSCs. As shown in Fig. 6 A, it exhibited piecewise linear when Cu-TPPE@paper sensed 0.07-8.0 ppm H 2 S. In Fig. 6 B, CL intensity was proportional to the H 2 S concentration of 0.07-1.0 ppm, and its linear equation was I = 823.5 C -4.7 ( R 2 = 0.996), where C was the concentration of gaseous H 2 S, and I was the CL intensity at this H 2 S concentration. In Fig. 6 C, the linear equation was I = 16.7 C + 795.2 ( R 2 = 0.995) for H 2 S of 1.0–8.0 ppm. According to 3 δ / k rule ( δ was the standard deviation of blank signal, k was the slope of calibration curve), the detection limit for H 2 S by this CL method was 0.03 ppm. Besides, Cu-TPPE@paper was also used to detect CH 4 S and C 2 H 6 S. As shown in Fig. S3A and Fig. S3B, the linear equation was I = 57.6 C -6.2 ( R 2 = 0.996) for 1.0–10.0 ppm CH 4 S with the detection limit of 0.3 ppm. For 0.08–0.8 ppm C 2 H 6 S in Fig. S3C and Fig. S3D, the linear equation was I = 1027.0 C -18.2 ( R 2 = 0.997) with the detection limit of 0.03 ppm. Table S1 summarized the different detection methods of VSCs in EB.[ 6 , 9 – 11 , 28 – 32 ] The results showed that this paper-based CL sensor was sensitive for analyzing VSCs in EB. Selectivity and Repeatability of Cu-TPPE@paper for VSCs Detection Human EB contains various disease-related compounds. For example, the concentration of 2-butanone in EB increased significantly for patients with liver cirrhosis[ 33 ], ovarian cancer[ 34 ] and helicobacter pylori infection[ 35 ]. The normal level of NH 3 in EB is 425–1800 ppb, and abnormal NH 3 content indicates renal failure.[ 36 ] As mentioned above, VSCs in EB were biomarkers of bad breath. To evaluate the selectivity of Cu-TPPE@paper for detecting VSCs in EB, interfering compounds in human exhalation were studied. As shown in Fig. S4A, adding 20-fold methanol, ethanol, isopropanol, formaldehyde, acetaldehyde, toluene and 50-fold acetone, CO 2 , SO 2 and NH 3 displayed a negligible influence on detection of 1 ppm H 2 S, indicating that the designed paper-based sensor was suitable for VSCs detection in human EB. The reliability of the experimental results was illustrated by repeated respond to 1 ppm H 2 S. As shown in Fig. S4B, RSD of H 2 S determination by the proposed sensor was 4.8% (n = 11), suggesting that the experimental results were reliable. Analysis of EB Samples As mentioned above, VSCs in EB are considered to be biomarkers of halitosis, gingivitis and periodontitis. To assess the feasibility of Cu-TPPE@paper for the analysis of VSCs in human EB, breath samples from three volunteers were collected, one of which was sampled before gargling in the morning. Different concentrations of gaseous H 2 S were spiked into EB samples. After sensing for 40 min, Cu-TPPE@paper was removed and analyzed by CL analyzer. The results in Table 1 showed the recovery rate of 90–110%, indicating that this paper-based AICE sensor was feasible for VSCs detection in human EB. Table 1 Detection of VSCs in human exhaled breath samples by proposed CL method (n = 3) Sample Initial ± SD (ppm) Added (ppm) Measured ± SD (ppm) 1 0.9 ± 0.2 0.4 1.2 ± 0.2 0.6 1.4 ± 0.1 0.8 1.7 ± 0.1 2 0.8 ± 0.1 0.4 1.1 ± 0.3 0.6 1.3 ± 0.2 0.8 1.5 ± 0.2 3 1.7 ± 0.3 0.4 2.0 ± 0.3 0.6 2.4 ± 0.2 0.8 2.5 ± 0.1 Conclusions In conclusion, a paper-based AICE sensor based on Cu delocalization of Cu-TPPE was developed for VSCs detection in human EB. As the 3d 9 valence electron of Cu 2+ induced electron transfer between Cu 2+ and TPPE ligand, Cu-TPPE was weakly emissive. VSCs can turn on luminescence because the reaction of Cu and S caused Cu delocalization of Cu-TPPE. CL determination of VSCs in human EB can be realized based on CRET between aggregated TPPE on paper and TCPO-H 2 O 2 donor. The linear range of H 2 S was 0.07-8.0 ppm with the detection limit of 0.03 ppm, and the recovery rate of H 2 S was 90–110% for human EB samples. CH 4 S had a linear range of 1.0–10.0 ppm with the detection limit of 0.3 ppm. The linear range of C 2 H 6 S was 0.08–0.8 ppm, and the detection limit was 0.03 ppm. This accurate and sensitive paper-based AICE platform has potential to analyze VSCs in real breath samples. Declarations Author contribution Huaqin Shui: Investigation, Formal analysis, Data curation, Software, Writing - Review & Editing, Visualization. Yanli Guo: Conceptualization, Methodology, Formal analysis, Investigation, Data curation, Writing-Original Draft, Visualization. Jingbo Geng: Validation. Qing Chang: Data curation. Yuxin Tian: Validation. Xue Du: Data curation. Yan Jin: Review. Baoxin Li: Review. Wei Liu: Review&Editing, Supervision, Funding acquisition. Funding We are very thankful to Natural Science Foundation of Shaanxi Province (No. 2024JC-YBMS-116) for supporting this work. The authors also thank the Fundamental Research Funds for the Central Universities (GK201902009 and GK201701002) and Program for Innovative Research Team in Shaanxi Province (2014KCT-28) for supporting this work. Data availability Data will be made available on request. Ethics approval and consent to participate This study received approval from the Committee on Ethics at Shaanxi Normal University, and all volunteers provided informed consent prior to their participation. Conflict of interest The authors declare no competing interests. References Moura PC, Raposo M, Vassilenko V (2023) Breath volatile organic compounds (VOCs) as biomarkers for the diagnosis of pathological conditions: A review. Biomed J 46(4):100623. https://doi.org/10.1016/j.bj.2023.100623 Chen T, Liu TN, Li T, Zhao H, Chen QM (2021) Exhaled breath analysis in disease detection. 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Chem-Eur 26(1):114–127. https://doi.org/10.1002/chem.201904054 Koshimune S, Awano S, Gohara K, Kurihara E, Ansai T, Takehara T (2003) Low Salivary Flow and Volatile Sulfur Compounds in Mouth Air. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 96(1):38–41. https://doi.org/10.1016/S1079-2104(03) 00162-8 Jornet-Martínez N, Hakobyan L, Argente-García AI, Molins-Legua C, Campíns-Falcó P (2019) Nylon-Supported Plasmonic Assay Based on the Aggregation of Silver Nanoparticles: In Situ Determination of Hydrogen Sulfide-like Compounds in Breath Samples as a Proof of Concept. ACS Sens 4(8):2164–2172. https://doi.org/10.1021/acssensors.9b01019 Bae G, Kim MJ, Lee A, Ji S, Jang M, Yim S, Song W, Lee SS, Yoon DH, An KS (2022) Nanometric Lamination of Zinc Oxide Nanofilms with Gold Nanoparticles for Self-Perceived Periodontal Disease Sensors. Compos Part B-Eng 230:109490. https://doi.org/10.1016/j.compositesb.2021.109490 Yang S, Sun J, Xu L, Zhou QQ, Chen XF, Zhu SD, Dong B, Lu GY, Song HW (2022) Au@ZnO Functionalized Three-Dimensional Macroporous WO 3 : A Application of Selective H 2 S Gas Sensor for Exhaled Breath Biomarker Detection. Sens Actuators B 324:128725. https://doi.org/10.1016/j.snb.2020.128725 Song BY, Zhang M, Teng Y, Zhang XF, Deng ZP, Huo LH, Gao S (2020) Highly Selective ppb-Level H 2 S Sensor for Spendable Detection of Exhaled Biomarker and Pork Freshness at Low Temperature: Mesoporous SnO 2 Hierarchical Architectures Derived from Waste Scallion Root. Sens Actuators B 307: 127662. https://doi.org/10.1016/j.snb.2020 . 127662 Morisco F, Aprea E, Lembo V, Fogliano V, Vitaglione P, Mazzone G, Cappellin L, Gasperi F, Masone S, Palma GDD, Marmo R, Caporaso N, Biasioli F (2013) Rapid Breath-Print of Liver Cirrhosis by Proton Transfer Reaction Time-of-Flight Mass Spectrometry. A Pilot Study. PLoS ONE 8(4):e59658. https://doi.org/10.1371/journal.pone.0059658 Amal H, Shi DY, Ionescu R, Zhang W, Hua QL, Pan YY, Tao L, Liu H, Haick H (2015) Assessment of Ovarian Cancer Conditions From Exhaled Breath. Int J Cancer 136(6):E614–E622. https://doi.org/10.1002/ijc.29166 Ulanowska A, Kowalkowski T, Hrynkiewicz K, Jackowski M, Buszewski B (2011) Determination of Volatile Organic Compounds in Human Breath for Helicobacter Pylori Detection by SPME-GC/MS. Biomed Chromatogr 25(3):391–397. https://doi.org/10.1002/bmc.1460 Vasilescu A, Hrinczenko B, Swain GM, Peteu SF (2021) Exhaled breath biomarker sensing. Biosens Bioelectron 182: 113193. https : //doi.org/10.1016/j.bios.2021.113193 Scheme Scheme 1 and 2 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files SupplementaryFile.docx Schemes.docx Cite Share Download PDF Status: Published Journal Publication published 03 Dec, 2025 Read the published version in Microchimica Acta → Version 1 posted Editorial decision: Revision requested 30 Aug, 2025 Reviews received at journal 22 Aug, 2025 Reviewers agreed at journal 10 Aug, 2025 Reviewers agreed at journal 06 Aug, 2025 Reviews received at journal 03 Aug, 2025 Reviewers agreed at journal 03 Aug, 2025 Reviewers invited by journal 02 Aug, 2025 Editor assigned by journal 24 Jul, 2025 Submission checks completed at journal 24 Jul, 2025 First submitted to journal 23 Jul, 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-7195328","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":496623727,"identity":"2a614b98-56b5-427b-ad66-c6aa22cf303f","order_by":0,"name":"Huaqin Shui","email":"","orcid":"","institution":"Shaanxi Normal University","correspondingAuthor":false,"prefix":"","firstName":"Huaqin","middleName":"","lastName":"Shui","suffix":""},{"id":496623728,"identity":"ce227fe9-68de-43ff-ad32-9ce5c4d9e101","order_by":1,"name":"Yanli Guo","email":"","orcid":"","institution":"Shaanxi Normal University","correspondingAuthor":false,"prefix":"","firstName":"Yanli","middleName":"","lastName":"Guo","suffix":""},{"id":496623729,"identity":"81a984b8-aa85-4d64-9bf7-b1bfc1352a3c","order_by":2,"name":"Jingbo Geng","email":"","orcid":"","institution":"Shaanxi Normal University","correspondingAuthor":false,"prefix":"","firstName":"Jingbo","middleName":"","lastName":"Geng","suffix":""},{"id":496623730,"identity":"035646e8-12b8-46d0-b6ec-92e108b452b4","order_by":3,"name":"Qing Chang","email":"","orcid":"","institution":"Shaanxi Normal University","correspondingAuthor":false,"prefix":"","firstName":"Qing","middleName":"","lastName":"Chang","suffix":""},{"id":496623731,"identity":"2ad5054a-d6fb-4e98-b2c1-40d9b04b66e6","order_by":4,"name":"Yuxin Tian","email":"","orcid":"","institution":"Shaanxi Normal University","correspondingAuthor":false,"prefix":"","firstName":"Yuxin","middleName":"","lastName":"Tian","suffix":""},{"id":496623732,"identity":"b20f5df6-30ce-476d-809b-7336765c6ca8","order_by":5,"name":"Xue Du","email":"","orcid":"","institution":"Shaanxi Normal University","correspondingAuthor":false,"prefix":"","firstName":"Xue","middleName":"","lastName":"Du","suffix":""},{"id":496623733,"identity":"02a0eb0a-4fe5-408a-ac72-904bf8b66c21","order_by":6,"name":"Yan Jin","email":"","orcid":"","institution":"Shaanxi Normal University","correspondingAuthor":false,"prefix":"","firstName":"Yan","middleName":"","lastName":"Jin","suffix":""},{"id":496623735,"identity":"01e370cd-85be-423e-a53c-70a8225e8a51","order_by":7,"name":"Baoxin Li","email":"","orcid":"","institution":"Shaanxi Normal University","correspondingAuthor":false,"prefix":"","firstName":"Baoxin","middleName":"","lastName":"Li","suffix":""},{"id":496623736,"identity":"a3179483-484e-4c44-950a-81590d8658b5","order_by":8,"name":"Wei Liu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAqklEQVRIiWNgGAWjYFACxsYDCQw2PPzsDcRraQBqSZOR7DlAgj1AtYdtDG44EKnc4Hhzw4GHbed5GG4wMH74mEOMljMHGw4ktt3mYZzdwCw5cxsRWsxuJEK0MMscYGPmJUrL/YcgLed42CQSiNVygxGk5QAPD9Fa7M8AHZZwLplHgudgM3F+kWw//vDhjzI7e/vjzQc/fCRGCxJgbCBN/SgYBaNgFIwC3AAABa87zs8gE94AAAAASUVORK5CYII=","orcid":"","institution":"Shaanxi Normal University","correspondingAuthor":true,"prefix":"","firstName":"Wei","middleName":"","lastName":"Liu","suffix":""}],"badges":[],"createdAt":"2025-07-23 10:38:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7195328/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7195328/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00604-025-07735-4","type":"published","date":"2025-12-03T15:57:40+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":88660391,"identity":"b8e41bf8-0649-41ce-9bb4-84fc9826d984","added_by":"auto","created_at":"2025-08-08 20:49:26","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":131987,"visible":true,"origin":"","legend":"\u003cp\u003eCharacterization of Cu-TPPE. (A) TEM image, (B) PXRD pattern, (C) FTIR spectrum and (D) N\u003csub\u003e2\u003c/sub\u003e absorption-desorption curve of Cu-TPPE powder.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7195328/v1/1d1950cac85f2f6d99e94021.png"},{"id":88660392,"identity":"236d73b0-963c-447c-8229-d42df4ebc609","added_by":"auto","created_at":"2025-08-08 20:49:26","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":89654,"visible":true,"origin":"","legend":"\u003cp\u003eAggregation behavior of Cu-TPPE on paper. (A) SEM image of Cu-TPPE on paper, (B) FL signals of Cu-TPPE@paper (10 \u003cem\u003eμ\u003c/em\u003eL) and Cu-TPPE ethanol solution (0.1 g/mL).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7195328/v1/e0c30406e992057843d22670.png"},{"id":88660916,"identity":"8980268d-7b62-4833-b723-0740b5100d2d","added_by":"auto","created_at":"2025-08-08 20:57:26","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":119514,"visible":true,"origin":"","legend":"\u003cp\u003eAggregation behavior of TPPE on paper. SEM images of (A) TPPE on paper and (B) TPPE powder, (C) FL and (D) CL comparisons of TPPE@paper and TPPE ethanol solution (0.01 g/mL) (TCPO: 5.0 mM, 2.5 \u003cem\u003eμ\u003c/em\u003eL; H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: 0.1 M, 2.5 \u003cem\u003eμ\u003c/em\u003eL).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7195328/v1/23253a06401cf5b56443d4fb.png"},{"id":88660403,"identity":"cc9ee70d-b5d3-4a86-9db1-618fa784e04f","added_by":"auto","created_at":"2025-08-08 20:49:26","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":246493,"visible":true,"origin":"","legend":"\u003cp\u003eThe principle of detecting VSCs using Cu-TPPE@paper. The pictures of Cu-TPPE@paper before and after response to H\u003csub\u003e2\u003c/sub\u003eS under (A) natural and (B) 365 nm UV light.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7195328/v1/4f878daeaab2c875f3a3a08d.png"},{"id":88660399,"identity":"0a0a1f28-b43f-4279-95bb-30aa8ce83da7","added_by":"auto","created_at":"2025-08-08 20:49:26","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":69256,"visible":true,"origin":"","legend":"\u003cp\u003eThe response of 1 ppm H\u003csub\u003e2\u003c/sub\u003eS by Cu-TPPE@paper via (A) FL method and (B) CL method, (C) The CL signal comparisons of detecting H\u003csub\u003e2\u003c/sub\u003eS in solution and on paper.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7195328/v1/4fdb23779430c1a4bdc0595a.png"},{"id":88660402,"identity":"40e22e05-b925-4884-8984-1449ff10d8e0","added_by":"auto","created_at":"2025-08-08 20:49:26","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":80889,"visible":true,"origin":"","legend":"\u003cp\u003eCL results of H\u003csub\u003e2\u003c/sub\u003eS detection with Cu-TPPE@paper. (A) CL signals of Cu-TPPE@paper after sensing 0.07-8.0 ppm H\u003csub\u003e2\u003c/sub\u003eS. Linear relationships between CL intensities and H\u003csub\u003e2\u003c/sub\u003eS concentrations of (B) 0.07-1.0 ppm and (C) 1.0-8.0 ppm (n=3).\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7195328/v1/e26c6f02f187f9136dc056b8.png"},{"id":97724029,"identity":"b29b0fef-953b-40a9-9f34-e5e2157c982e","added_by":"auto","created_at":"2025-12-08 16:11:11","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1576530,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7195328/v1/a878f56e-c037-4d56-ab35-6fd2e8ecb370.pdf"},{"id":88660917,"identity":"17b5ed38-a3c1-447b-8584-794981a41837","added_by":"auto","created_at":"2025-08-08 20:57:26","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":5663492,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryFile.docx","url":"https://assets-eu.researchsquare.com/files/rs-7195328/v1/7487524cbc4d55ab39ceae44.docx"},{"id":88660396,"identity":"2a04e1d1-f7e6-4e6a-baad-e79f894670b9","added_by":"auto","created_at":"2025-08-08 20:49:26","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":418071,"visible":true,"origin":"","legend":"","description":"","filename":"Schemes.docx","url":"https://assets-eu.researchsquare.com/files/rs-7195328/v1/ff156850c1dabd5701e58ac7.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Tetrakis(4-pyridylphenyl)ethylene-decorated metal–organic frameworks with aggregation induced chemiluminescence emission on paper-based paltform for volatile sulfur compounds measurement","fulltext":[{"header":"Introduction","content":"\u003cp\u003eHuman exhaled breath (EB) contains about 3000 volatile organic compounds (VOCs), some of which are related to metabolic conditions.[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] For example, isoprene, aldehydes and acetone in EB are indicators of cardiovascular disease[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], lung cancer[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] and diabetes[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], respectively. Volatile sulfur compounds (VSCs) in EB, including hydrogen sulfide (H\u003csub\u003e2\u003c/sub\u003eS), methyl mercaptan (CH\u003csub\u003e4\u003c/sub\u003eS) and dimethyl sulfide (C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eS), are generated when oral bacteria degrades sulfur-containing amino acids (such as cysteine and methionine),[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] so VSCs in human exhalation are regarded as markers of halitosis.[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] Exhaled H\u003csub\u003e2\u003c/sub\u003eS of halitosis patients exceeds 2 ppm, which is 3\u0026ndash;4 times higher than healthy people.[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] Halitosis is associated with gingivitis and periodontitis,[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] so detection of VSCs in breath is of significance for disease screening. Currently, gas chromatography-mass spectrometry (GC-MS)[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], colorimetric sensor[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] and electrochemical gas sensor[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] have been used to analyze VSCs in EB. However, GC-MS is time-consuming and expensive, thus it is not convenient for large-scale application. Colorimetric sensor does not have complex circuits, but it features low sensitivity and response speed. Electrochemical gas sensor is highly sensitive, but it usually works at high temperature and thus is not convenient for on-site diagnosis of halitosis. Therefore, establishing an accurate, low-cost and portable VSCs analysis platform is of great significance for the assessment of halitosis.\u003c/p\u003e\u003cp\u003eEB contains various VOCs, while the content of H\u003csub\u003e2\u003c/sub\u003eS in EB is ppm level,[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] so metal-organic frameworks (MOFs) with large surface area and high porosity were used to adsorb and enrich VSCs. As CuS can be formed between Cu and sulfur-containing compounds, Cu-based MOFs such as Cu-TATB[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] and Cu-BTC[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] have been used for selective capture and sensing of H\u003csub\u003e2\u003c/sub\u003eS. If MOFs are loaded on flexible paper, resulting paper-based analysis platform will have advantages of both portable and sensitive. However, the fluorescence (FL) of traditional luminescent MOFs is quenched in solid state, so this work chose MOF with aggregation-induced emission (AIE) effect to adsorb, capture and sense VSCs in EB. Among various ligands of MOFs with AIE property, tetraphenylethene (TPE) and its derivatives such as tetrakis(4-pyridylphenyl)ethylene (TPPE) have been widely used to prepare MOFs with AIE characteristics due to simple synthesis and good stability.[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] Therefore, in this paper, Cu-TPPE was synthesized and loaded on paper for selective capture and sensing of VSCs in EB.\u003c/p\u003e\u003cp\u003eNowadays, investigation of MOFs with AIE effect usually focused on FL method.[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] Since Lv's group[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] combined the AIE phenomenon of Au NCs aggregates with chemiluminescence (CL) of bis(2,4,6-trichlorophenyl)oxalate (TCPO)-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, reports about aggregation-induced chemiluminescence emission (AICE) gradually appeared. For example, Li's team[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] prepared a covalent organic framework with AIE property (TPE@SNW\u003csub\u003e\u0026minus;\u0026thinsp;1\u003c/sub\u003e) by combining TPE with a Schiff base network (SNW\u003csub\u003e\u0026minus;\u0026thinsp;1\u003c/sub\u003e). Using TPE@SNW\u003csub\u003e\u0026minus;\u0026thinsp;1\u003c/sub\u003e as energy acceptor and TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e as energy donor, chemiluminescent resonance energy transfer (CRET) system was designed. The linear range of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e was 5.0-1000.0 \u0026micro;M with the detection limit of 2.34 \u0026micro;M. Based on generated H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e when uric acid was catalyzed by uricase, uric acid in human serum samples can be determined with the linear range of 10.0-150.0 \u0026micro;M and the detection limit of 4.94 \u0026micro;M. CL technology has the advantages of simple device, high sensitivity, wide linear range and low background.[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] Although there have been reports on the determination of sulfur-containing compounds by CL method, CL analysis of H\u003csub\u003e2\u003c/sub\u003eS was often based on inhibited CL signal by H\u003csub\u003e2\u003c/sub\u003eS,[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] and until now, no report on the detection of VSCs based on AICE was found. Therefore, it is necessary to develop aggregation-induced chemiluminescence enhancement method to detect VSCs in EB.\u003c/p\u003e\u003cp\u003eHerein, Cu-TPPE was prepared using TPPE with AIE effect as ligand. A paper-based sensor (Cu-TPPE@paper) was designed by loading Cu-TPPE on paper. The valence electron of Cu\u003csup\u003e2+\u003c/sup\u003e was 3d\u003csup\u003e9\u003c/sup\u003e, so electron transfer between Cu\u003csup\u003e2+\u003c/sup\u003e and TPPE can occur, thus Cu-TPPE had almost no aggregation-induced luminescence. However, in the presence of VSCs, the affinity between S and Cu led to delocalization of Cu in Cu-TPPE, thus recovering FL of TPPE.[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] TPPE was aggregated on paper. Aggregated TPPE with AIE property and TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e donor can trigger CRET, so AICE was produced. In this way, VSCs in EB can be detected based on enhanced CL signals. Scheme \u003cspan refid=\"Sch1\" class=\"InternalRef\"\u003e1\u003c/span\u003e showed the sensing principle of VSCs by Cu-TPPE and TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e system. This paper-based CL sensor was accurate and sensitive, promising to screen patients with oral diseases from healthy people.\u003c/p\u003e"},{"header":"Experimental section","content":"\u003cp\u003e\u003cb\u003eMaterials and Reagents\u003c/b\u003e\u003c/p\u003e\u003cp\u003eTetrakis(4-pyridylphenyl)ethylene (TPPE) was purchased from Alpha Chemical Reagents Co., Ltd. (Zhengzhou, China). Sodium hydrosulfide hydrate (NaHS∙xH\u003csub\u003e2\u003c/sub\u003eO), phosphate, dimethyl sulfide (C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eS), copper (II) chloride dehydrate (CuCl\u003csub\u003e2\u003c/sub\u003e∙2H\u003csub\u003e2\u003c/sub\u003eO), tetrachloroethene, bis(2,4,6-trichlorophenyl)oxalate (TCPO), formaldehyde, acetaldehyde, ammonium chloride, sodium hydrogen sulfite and sodium carbonate were obtained from Aladdin Reagents Co., Ltd. (Shanghai, China). Methyl mercaptan (CH\u003csub\u003e4\u003c/sub\u003eS) was from Sigma Co., Ltd. (USA). Methanol, ethanol, isopropanol, acetone, toluene, hydrogen peroxide aqueous solution (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, 30wt%), sodium hydroxide, hydrochloric acid (36\u0026ndash;38%) and potassium bromide were provided by Sinopharm Chemical Reagents Co., Ltd. (Shanghai, China). 5 mM TCPO solution was prepared by dissolving TCPO into acetone. The water used in this work was secondary ultra-pure water (18.2 MΩ cm). Whatman chromatography paper #1 was purchased from Sigma Co., Ltd. (USA). Teflon gas sampling bag was from Zhanhai Co., Ltd. (China).\u003c/p\u003e\u003cp\u003e\u003cb\u003eInstrumentations\u003c/b\u003e\u003c/p\u003e\u003cp\u003eSU8220 scanning electron microscopy (SEM) and F-7000 fluorescence spectrometer were purchased from Hitachi Instruments Co., Ltd., Kyoto, Japan. D8 advance X-ray diffractometer (XRD) and Prestige-21 Fourier transform infrared (FTIR) spectrometer were from Bruker Instruments Co., Ltd., Germany. Brunauer-Emmett-Teller (BET) test was performed on ASAP2020 (Micromeritics, USA). CL tests were performed on a model IFFS-A CL analyzer and the data were obtained by RFL-1 software (Remex Electronic Sci. Tech. Co. Ltd., China). 4-20R bench high speed refrigerated centrifuge was from Henuo Instrument Equipment Co., Ltd., Hunan. DZF-6030A electric blast drying oven was purchased from Yiheng Scientific Instrument Co., Ltd., Shanghai. AL204-IC electronic analytical balance was obtained from Mettler Toledo Instrument Co., Ltd., Switzerland. 1810B ultra-pure water machine and KH5200E ultrasonic cleaner were from Chongqing Moore Water Treatment Equipment Co., Ltd and Hechuang Ultrasonic Instrument Co., Ltd., Kunshan, respectively.\u003c/p\u003e\u003cp\u003e\u003cb\u003eSynthesis of Cu-TPPE Powder and Preparation of Cu-TPPE@paper\u003c/b\u003e\u003c/p\u003e\u003cp\u003eCu-TPPE powder was synthesized according to the work of Latham\u0026rsquo;s group with small modifications.[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] First, 27.2 mg CuCl\u003csub\u003e2\u0026middot;\u003c/sub\u003e2H\u003csub\u003e2\u003c/sub\u003eO was dissolved in 10 mL CH\u003csub\u003e3\u003c/sub\u003eOH, and 25 mg TPPE was dissolved in a mixture of 11.25 mL CCl\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;CCl\u003csub\u003e2\u003c/sub\u003e and 3.75 mL CH\u003csub\u003e3\u003c/sub\u003eOH. Then, the CuCl\u003csub\u003e2\u003c/sub\u003e solution was gently poured into the above TPPE solution and left at room temperature for 3 d. Finally, Cu-TPPE powder was obtained by vacuum drying of green crystals at 55 ℃ for 4 h. Cu-TPPE@paper was fabricated by loading 10 \u003cem\u003e\u0026micro;\u003c/em\u003eL 0.1 g\u0026middot;mL\u003csup\u003e-1\u003c/sup\u003e Cu-TPPE ethanol solution onto paper.\u003c/p\u003e\u003cp\u003e\u003cb\u003eGeneration of Standard Gas\u003c/b\u003e\u003c/p\u003e\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eS is a binary weak acid with pK\u003cem\u003ea\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;6.76 at 37 ℃. When pH\u0026thinsp;\u0026lt;\u0026thinsp;6, sulfides can be considered to be entirely in the form of H\u003csub\u003e2\u003c/sub\u003eS.[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] Therefore, different concentrations of H\u003csub\u003e2\u003c/sub\u003eS standard gas can be prepared by acidifying different concentrations of NaHS solution with 85% H\u003csub\u003e3\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e. For accurately controlling gas volume, resealable Teflon bag (200 mL) was used. After filling the bag with nitrogen, NaHS and H\u003csub\u003e3\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e solutions were injected successively. The Teflon bag was placed at 37℃ for 2 h to obtain homogeneous volatile H\u003csub\u003e2\u003c/sub\u003eS. The generation of CH\u003csub\u003e4\u003c/sub\u003eS and C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eS standard gases was in the similar way.\u003c/p\u003e\u003cp\u003e\u003cb\u003eDetection of VSCs with Cu-TPPE@paper\u003c/b\u003e\u003c/p\u003e\u003cp\u003eAnalysis procedure of VSCs by CL method was as follows. First, Cu-TPPE@paper was placed into a Teflon bag with a cutting incision. Then, tape was used to seal the cutting incision, and the air in the bag was driven out with a vacuum pump.[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] Next, the standard gas prepared above was transferred to this bag. After sensing for 40 min, Cu-TPPE@paper was taken out from the bag and was put into CL analyzer. Finally, TCPO and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e were introduced to Cu-TPPE@paper to obtain CL signal. The detection of CH\u003csub\u003e4\u003c/sub\u003eS and C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eS was in the similar way.\u003c/p\u003e\u003cp\u003e\u003cb\u003eDetermination of VSCs in Human Exhaled Breath Samples\u003c/b\u003e\u003c/p\u003e\u003cp\u003e Breath samples collected from three healthy volunteers without oral diseases from Shaanxi Normal University. Before breath sampling, to avoid exogenous interfering gases, the volunteers should not eat and needed to rest for 10 min in a well-ventilated room.[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] When collecting the exhalation, the volunteers breathed deeply and exhaled into a Teflon bag with Cu-TPPE@paper in it. After sensing for 40 min, Cu-TPPE@paper was removed from the bag and then TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e was introduced to obtain CL response.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003e\u003cb\u003eCharacterization of Cu-TPPE\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe synthesized Cu-TPPE was characterized by the following protocols. The morphology of green Cu-TPPE was investigated by TEM. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA showed Cu-TPPE sheets had a size of about 100 nm. In Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB, powder X-ray diffraction (PXRD) pattern of the synthesized Cu-TPPE was consistent with the work of Latham\u0026rsquo;s team,[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] indicating that Cu-TPPE was successfully prepared. For the FTIR spectrum of Cu-TPPE (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC), the peaks at 1557 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1115 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e belonged to C\u0026thinsp;=\u0026thinsp;C bending vibrations and C-H in-plane vibrations of phenyl ring, respectively.[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] The absorption peak at 1487 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponded to stretching vibrations of benzene ring, and the peak at 1605 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was assigned to the pyridine group of the TPPE ligand.[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] The FTIR peaks at 650\u0026ndash;910 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in the fingerprint region reflected the different substitutions of aromatic ring. The N\u003csub\u003e2\u003c/sub\u003e adsorption isotherm of Cu-TPPE exhibited type I and its Langmuir surface area was 101.4 m\u003csup\u003e2\u003c/sup\u003e/g (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eD), indicating that gaseous H\u003csub\u003e2\u003c/sub\u003eS can be adsorbed by Cu-TPPE.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eAggregation Behaviors of Cu-TPPE and TPPE on paper\u003c/b\u003e\u003c/p\u003e\u003cp\u003eAccording to previous reports, TPPE with AIE effect was used as ligand to prepare MOFs, the synthesized MOFs still exhibited AIE property,[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] and AIE phenomenon can be produced when they were in solid state.[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] Therefore, in this work, Cu-TPPE using TPPE as ligand was loaded onto solid-phase paper to investigate its luminescence performance. By comparing the SEM of Cu-TPPE powder in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA, it was found that Cu-TPPE was aggregated on paper with an average size of 10 \u003cem\u003e\u0026micro;\u003c/em\u003em (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). However, Cu-TPPE emitted almost no FL because the 3d\u003csup\u003e9\u003c/sup\u003e valence electron of Cu\u003csup\u003e2+\u003c/sup\u003e induced electron transfer between Cu\u003csup\u003e2+\u003c/sup\u003e and TPPE. Therefore, the FL of Cu-TPPE ethanol solution and Cu-TPPE@paper were weak (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). Next, TPPE ligand with AIE effect on paper was studied. The SEM in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA showed that TPPE was also aggregated on paper with a size of about 20 \u003cem\u003e\u0026micro;\u003c/em\u003em, while TPPE powder itself was columnar with an average length of 10 \u003cem\u003e\u0026micro;\u003c/em\u003em and a width of 2 \u003cem\u003e\u0026micro;\u003c/em\u003em (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB). The FL intensity of TPPE@paper was significantly increased compared to TPPE ethanol solution (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC), suggesting that AIE phenomenon can be easily produced by loading AIE molecules onto paper. TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e system is a commonly used CL system. Based on CRET between TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and fluorescent molecules, various substances have been detected.[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] Introducing TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e into TPPE solution and TPPE@paper, CL comparison results illustrated that TPPE@paper can cause TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e to produce strong CL (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eD), which further showed that TPPE@paper can trigger AICE phenomenon.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eThe CL Mechanism of TPPE-TCPO-H\u003c/b\u003e\u003csub\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sub\u003e\u003cb\u003eO\u003c/b\u003e\u003csub\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sub\u003e \u003cb\u003eSystem\u003c/b\u003e\u003c/p\u003e\u003cp\u003eAs mentioned above, TPPE@paper can trigger TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e to produce strong CL. The CL mechanism of TPPE-TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e system was investigated. As shown in Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003eA, the CL spectrum peak of TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e system was at 450 nm, which overlapped the FL excitation spectrum of TPPE in Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003eB (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003eC). The CL spectrum peak of TPPE-TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e system was located at 470 nm (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003eD), which was corresponded to the FL emission wavelength of TPPE (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003eB). Above results showed that CRET occurred between TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and TPPE acceptor, and the emitting species of TPPE-TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e system was excited-state TPPE. Only the energy transfer between TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and TPPE can be confirmed by the experimental result that TPPE-TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e had no UV-Vis new peaks compared with TPPE and TCPO (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003eE). Therefore, the possible CL mechanism of TPPE-TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e system was as follows. TCPO was oxidized by H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e to generate high-energy 1,2-dioxetane intermediate, then its energy was transferred to TPPE to form excited TPPE, and CL was produced when excited TPPE returned to the ground state (Scheme \u003cspan refid=\"Sch2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eThe Principle of Sensing VSCs with Cu-TPPE@paper\u003c/b\u003e\u003c/p\u003e\u003cp\u003eDesigned Cu-TPPE@paper was used to detect VSCs. As mentioned above, although Cu-TPPE was aggregated on paper, Cu (Ⅱ)-induced electron transfer led to emitting almost no FL of aggregated Cu-TPPE on paper.[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] However, VSCs caused Cu delocalization in Cu-TPPE due to the affinity between S and Cu, thus turning on FL of aggregated TPPE. This sensing principle can be verified by comparing pictures of Cu-TPPE@paper before and after adsorbing 10 ppm H\u003csub\u003e2\u003c/sub\u003eS under natural and 365 nm UV light. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA, Cu-TPPE@paper appeared green. Yellow TPPE appeared after response to H\u003csub\u003e2\u003c/sub\u003eS. When irradiating above papers by 365 nm UV lamp, the FL of Cu-TPPE@paper exposed to H\u003csub\u003e2\u003c/sub\u003eS was much stronger (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB). Above results confirmed the delocalization of Cu in Cu-TPPE and the aggregation of TPPE on paper. Compared with FL method, CL technology had lower background, so both analysis methods for determination of 1 ppm H\u003csub\u003e2\u003c/sub\u003eS were compared here. In Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eA, the signal-to-noise ratio (S/N) of sensing H\u003csub\u003e2\u003c/sub\u003eS using Cu-TPPE@paper by FL method was 7.8, while the S/N of CL method was 19.8 (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB), indicating that CL method had advantage over FL method for detecting H\u003csub\u003e2\u003c/sub\u003eS. To illustrate the advantages of the paper-based analysis platform, the S/N of sensing H\u003csub\u003e2\u003c/sub\u003eS in solution and on paper via CL technology was compared. The results in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eC demonstrated that detecting H\u003csub\u003e2\u003c/sub\u003eS on paper was more sensitive, which may be because TPPE generated by Cu delocalization was aggregated on paper. Therefore, CL method and Cu-TPPE@paper were chosen for detecting VSCs.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eOptimization of VSCs Detection Conditions\u003c/b\u003e\u003c/p\u003e\u003cp\u003eTo explore the optimal conditions for detection of VSCs, optimization experiments were carried out. First, the concentrations of TCPO and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e were optimized. Due to the weak FL of Cu-TPPE@paper, 1 ppm H\u003csub\u003e2\u003c/sub\u003eS was adsorbed for 30 min to provide detectable CL signals. The best detection performances were obtained when the concentrations of TCPO and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e were 2.5 mM (Fig. S2A) and 0.1 M (Fig. S2B), respectively. It took time for H\u003csub\u003e2\u003c/sub\u003eS to enter the pore of Cu-TPPE and the reaction of Cu and S, so the adsorption time of H\u003csub\u003e2\u003c/sub\u003eS was optimized. The result in Fig. S2C showed that 40 min was suitable for H\u003csub\u003e2\u003c/sub\u003eS determination.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAICE Detection of VSCs\u003c/b\u003e\u003c/p\u003e\u003cp\u003eCu-TPPE@paper was used for CL detection of VSCs. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eA, it exhibited piecewise linear when Cu-TPPE@paper sensed 0.07-8.0 ppm H\u003csub\u003e2\u003c/sub\u003eS. In Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eB, CL intensity was proportional to the H\u003csub\u003e2\u003c/sub\u003eS concentration of 0.07-1.0 ppm, and its linear equation was \u003cem\u003eI\u003c/em\u003e\u0026thinsp;=\u0026thinsp;823.5 \u003cem\u003eC\u003c/em\u003e-4.7 (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.996), where C was the concentration of gaseous H\u003csub\u003e2\u003c/sub\u003eS, and I was the CL intensity at this H\u003csub\u003e2\u003c/sub\u003eS concentration. In Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eC, the linear equation was \u003cem\u003eI\u003c/em\u003e\u0026thinsp;=\u0026thinsp;16.7 \u003cem\u003eC\u003c/em\u003e\u0026thinsp;+\u0026thinsp;795.2 (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.995) for H\u003csub\u003e2\u003c/sub\u003eS of 1.0\u0026ndash;8.0 ppm. According to 3\u003cem\u003eδ\u003c/em\u003e/\u003cem\u003ek\u003c/em\u003e rule (\u003cem\u003eδ\u003c/em\u003e was the standard deviation of blank signal, \u003cem\u003ek\u003c/em\u003e was the slope of calibration curve), the detection limit for H\u003csub\u003e2\u003c/sub\u003eS by this CL method was 0.03 ppm. Besides, Cu-TPPE@paper was also used to detect CH\u003csub\u003e4\u003c/sub\u003eS and C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eS. As shown in Fig. S3A and Fig. S3B, the linear equation was \u003cem\u003eI\u003c/em\u003e\u0026thinsp;=\u0026thinsp;57.6 \u003cem\u003eC\u003c/em\u003e-6.2 (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.996) for 1.0\u0026ndash;10.0 ppm CH\u003csub\u003e4\u003c/sub\u003eS with the detection limit of 0.3 ppm. For 0.08\u0026ndash;0.8 ppm C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eS in Fig. S3C and Fig. S3D, the linear equation was \u003cem\u003eI\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1027.0 \u003cem\u003eC\u003c/em\u003e-18.2 (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.997) with the detection limit of 0.03 ppm. Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e summarized the different detection methods of VSCs in EB.[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan additionalcitationids=\"CR29 CR30 CR31\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e] The results showed that this paper-based CL sensor was sensitive for analyzing VSCs in EB.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eSelectivity and Repeatability of Cu-TPPE@paper for VSCs Detection\u003c/b\u003e\u003c/p\u003e\u003cp\u003eHuman EB contains various disease-related compounds. For example, the concentration of 2-butanone in EB increased significantly for patients with liver cirrhosis[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], ovarian cancer[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] and helicobacter pylori infection[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. The normal level of NH\u003csub\u003e3\u003c/sub\u003e in EB is 425\u0026ndash;1800 ppb, and abnormal NH\u003csub\u003e3\u003c/sub\u003e content indicates renal failure.[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] As mentioned above, VSCs in EB were biomarkers of bad breath. To evaluate the selectivity of Cu-TPPE@paper for detecting VSCs in EB, interfering compounds in human exhalation were studied. As shown in Fig. S4A, adding 20-fold methanol, ethanol, isopropanol, formaldehyde, acetaldehyde, toluene and 50-fold acetone, CO\u003csub\u003e2\u003c/sub\u003e, SO\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e3\u003c/sub\u003e displayed a negligible influence on detection of 1 ppm H\u003csub\u003e2\u003c/sub\u003eS, indicating that the designed paper-based sensor was suitable for VSCs detection in human EB. The reliability of the experimental results was illustrated by repeated respond to 1 ppm H\u003csub\u003e2\u003c/sub\u003eS. As shown in Fig. S4B, RSD of H\u003csub\u003e2\u003c/sub\u003eS determination by the proposed sensor was 4.8% (n\u0026thinsp;=\u0026thinsp;11), suggesting that the experimental results were reliable.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAnalysis of EB Samples\u003c/b\u003e\u003c/p\u003e\u003cp\u003eAs mentioned above, VSCs in EB are considered to be biomarkers of halitosis, gingivitis and periodontitis. To assess the feasibility of Cu-TPPE@paper for the analysis of VSCs in human EB, breath samples from three volunteers were collected, one of which was sampled before gargling in the morning. Different concentrations of gaseous H\u003csub\u003e2\u003c/sub\u003eS were spiked into EB samples. After sensing for 40 min, Cu-TPPE@paper was removed and analyzed by CL analyzer. The results in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e showed the recovery rate of 90\u0026ndash;110%, indicating that this paper-based AICE sensor was feasible for VSCs detection in human EB.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eDetection of VSCs in human exhaled breath samples by proposed CL method (n\u0026thinsp;=\u0026thinsp;3)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eInitial\u0026thinsp;\u0026plusmn;\u0026thinsp;SD (ppm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAdded (ppm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMeasured\u0026thinsp;\u0026plusmn;\u0026thinsp;SD (ppm)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e0.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e1.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e1.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e1.7\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e0.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e1.1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e1.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e1.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e1.7\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e2.0\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e2.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn conclusion, a paper-based AICE sensor based on Cu delocalization of Cu-TPPE was developed for VSCs detection in human EB. As the 3d\u003csup\u003e9\u003c/sup\u003e valence electron of Cu\u003csup\u003e2+\u003c/sup\u003e induced electron transfer between Cu\u003csup\u003e2+\u003c/sup\u003e and TPPE ligand, Cu-TPPE was weakly emissive. VSCs can turn on luminescence because the reaction of Cu and S caused Cu delocalization of Cu-TPPE. CL determination of VSCs in human EB can be realized based on CRET between aggregated TPPE on paper and TCPO-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e donor. The linear range of H\u003csub\u003e2\u003c/sub\u003eS was 0.07-8.0 ppm with the detection limit of 0.03 ppm, and the recovery rate of H\u003csub\u003e2\u003c/sub\u003eS was 90\u0026ndash;110% for human EB samples. CH\u003csub\u003e4\u003c/sub\u003eS had a linear range of 1.0\u0026ndash;10.0 ppm with the detection limit of 0.3 ppm. The linear range of C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eS was 0.08\u0026ndash;0.8 ppm, and the detection limit was 0.03 ppm. This accurate and sensitive paper-based AICE platform has potential to analyze VSCs in real breath samples.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor contribution\u003c/strong\u003e Huaqin Shui: Investigation, Formal analysis, Data curation, Software, Writing - Review \u0026amp; Editing, Visualization. Yanli Guo: Conceptualization, Methodology, Formal analysis, Investigation, Data curation, Writing-Original Draft, Visualization. Jingbo Geng: Validation. Qing Chang: Data curation. Yuxin Tian: Validation. Xue Du: Data curation. Yan Jin: Review. Baoxin Li: Review. Wei Liu: Review\u0026amp;Editing, Supervision, Funding acquisition.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003eWe are very thankful to Natural Science Foundation of Shaanxi Province (No. 2024JC-YBMS-116) for supporting this work. The authors also thank the Fundamental Research Funds for the Central Universities (GK201902009 and GK201701002) and Program for Innovative Research Team in Shaanxi Province (2014KCT-28) for supporting this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e Data will be made available on request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e This study received approval from the Committee on Ethics at Shaanxi Normal University, and all volunteers provided informed consent prior to their participation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e The authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMoura PC, Raposo M, Vassilenko V (2023) Breath volatile organic compounds (VOCs) as biomarkers for the diagnosis of pathological conditions: A review. 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Biosens Bioelectron 182: 113193. \u003cem\u003ehttps\u003c/em\u003e:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e//doi.org/10.1016/j.bios.2021.113193\u003c/span\u003e\u003cspan address=\"http:////doi.org/10.1016/j.bios.2021.113193\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Scheme ","content":"\u003cp\u003eScheme 1 and 2 are available in the Supplementary Files section.\u003c/p\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":"microchimica-acta","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"miac","sideBox":"Learn more about [Microchimica Acta](https://link.springer.com/journal/604)","snPcode":"604","submissionUrl":"https://submission.springernature.com/new-submission/604/3","title":"Microchimica Acta","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Volatile sulfur compounds, tetrakis(4-pyridylphenyl)ethylene, Aggregation-induced emission, Chemiluminescence, Exhaled breath","lastPublishedDoi":"10.21203/rs.3.rs-7195328/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7195328/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eVolatile sulfur compounds (VSCs) in human exhaled breath (EB) are considered as biomarkers of halitosis. Convenient and reliable detection of VSCs has significance for confirming oral health. Herein, copper-based metal-organic framework (Cu-TPPE) was synthesized by utilizing aggregation-induced emission (AIE) phenomenon of tetrakis(4-pyridylphenyl)ethylene (TPPE) ligand on paper. Due to electron transfer between Cu\u003csup\u003e2+\u003c/sup\u003e and TPPE, the aggregation-induced emission of TPPE was quenched. In the presence of VSCs, the affinity between S and Cu led to delocalization of Cu in Cu-TPPE, thus recovering the aggregation-induced chemiluminescence emission (AICE) between TPPE and bis(2,4,6-trichlorophenyl)oxalate (TCPO)-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. Based on this principle, selective and sensitive determination of VSCs in human EB was achieved. Quantification linear range of H\u003csub\u003e2\u003c/sub\u003eS was 0.07-8.0 ppm, and the detection limit was 0.03 ppm. This paper-based chemiluminescence (CL) platform has been applied to the detection of VSCs in real breath samples.\u003c/p\u003e","manuscriptTitle":"Tetrakis(4-pyridylphenyl)ethylene-decorated metal–organic frameworks with aggregation induced chemiluminescence emission on paper-based paltform for volatile sulfur compounds measurement","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-08 20:49:21","doi":"10.21203/rs.3.rs-7195328/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-08-30T15:46:47+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-22T11:27:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"61608407650334034386575317761786979924","date":"2025-08-11T03:46:32+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"90914133497256676173303224364624172139","date":"2025-08-06T13:20:46+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-04T03:56:04+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"25212939155776995368103645085523821045","date":"2025-08-04T01:55:16+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-02T18:24:58+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-24T13:14:19+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-24T13:13:27+00:00","index":"","fulltext":""},{"type":"submitted","content":"Microchimica Acta","date":"2025-07-23T10:30:05+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"microchimica-acta","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"miac","sideBox":"Learn more about [Microchimica Acta](https://link.springer.com/journal/604)","snPcode":"604","submissionUrl":"https://submission.springernature.com/new-submission/604/3","title":"Microchimica Acta","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"7155ed81-b183-4c0c-9164-69f2519ef695","owner":[],"postedDate":"August 8th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-08T16:05:16+00:00","versionOfRecord":{"articleIdentity":"rs-7195328","link":"https://doi.org/10.1007/s00604-025-07735-4","journal":{"identity":"microchimica-acta","isVorOnly":false,"title":"Microchimica Acta"},"publishedOn":"2025-12-03 15:57:40","publishedOnDateReadable":"December 3rd, 2025"},"versionCreatedAt":"2025-08-08 20:49:21","video":"","vorDoi":"10.1007/s00604-025-07735-4","vorDoiUrl":"https://doi.org/10.1007/s00604-025-07735-4","workflowStages":[]},"version":"v1","identity":"rs-7195328","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7195328","identity":"rs-7195328","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}