Construction of S,O-Doped g-C3N4 Encapsulated in Eu-MOF with Dual-Emission for Ratiometric Fluorescence Detection of Hg²⁺

Construction of S,O-Doped g-C3N4 Encapsulated in Eu-MOF with Dual-Emission for Ratiometric Fluorescence Detection of Hg²⁺ | 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 Construction of S,O-Doped g-C 3 N 4 Encapsulated in Eu-MOF with Dual-Emission for Ratiometric Fluorescence Detection of Hg²⁺ Jie Yao, Hongfang Chen, Xiaohua Yang, Muzaffar Iqbal, Wei Bian This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6942147/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 25 Aug, 2025 Read the published version in Journal of Fluorescence → Version 1 posted 11 You are reading this latest preprint version Abstract Mercury ions (Hg 2+ ) are categorized as environmental pollutants, which distributed in water, soil, and food systems due to environmental contamination. Hence, designing a sensitive assay for the convenient determination of Hg 2+ is of great importance. Herein, S and O-doped graphite phase nitrogenized carbon quantum dots (S,O-C 3 N 4 QDs) was encapsulated within a europium -based metal-organic framework (Eu-MOF) to construct a novel ratiometric fluorescent nanoprobe for the quantitative detection of Hg 2+ . The native emission of S,O-C 3 N 4 QDs at 445 nm is used as a response signal, while Eu-MOF with fluorescence offers a reference signal at 619 nm. Hg 2+ exhibits high affinity for the surface functional groups of S/O-C 3 N 4 QDs, forming non-fluorescent chelation complexes that induce static quenching. This results in significant attenuation of the fluorescence intensity at 445 nm, while the emission at 619 nm remains invariant. A ratiometric fluorescence sensing platform was established based on the intensity ratio (F 445 /F 619 ) for the selective detection of Hg 2+ . The linear range of S,O-C 3 N 4 QDs/Eu-MOF of Hg 2+ was 0.25–35 µM and with a detection limit of 4.3 nM. The satisfying results demonstrate the effectiveness of the developed S,O-C 3 N 4 QDs/Eu-MOF-based fluorescence probe for Hg 2+ detection, highlighting its promising potential for environmental monitoring applications. Doped Eu-MOF fluorescence sensor Quantum dots Ratiometric fluorescence Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Introduction Mercury ions (Hg 2+ ) are persistent global environmental pollutant that can pose a significant risk to human health through the food chain.[ 1 ] The enrichment of Hg 2+ in the human body can cause severe immunotoxicity, genotoxicity and neurotoxicity to the human by forming stable complexes with enzymes and thiols in proteins.[ 2 , 3 ] Therefore, establishing a sensitive and accurate method for detecting Hg 2+ has great significance for human health and ecological security. Currently, there are many reported methods for detecting trace amounts of Hg 2+ , such as high performance liquid chromatography, cold atomic absorption spectrometry, inductively coupled plasma mass spectrometry, capillary electrophoresis and fluorescence methods.[ 4 – 7 ] Among these methods, fluorescence method has great application potential in practical applications due to its lots of advantages, such as high sensitivity, excellent efficiency, convenient operation and low cost.[ 8 , 9 ] The traditional fluorescence detection method relies on single fluorescence transmission signal, which is prone to environmental interference, resulting in unstable experimental signals and being unfavorable for conducting multiple experiment.[ 10 , 11 ] Compared with single fluorescence signal detection, the dual-emission fluorescence probe minimizes environmental interference and intrinsic concentration-dependent errors through self-calibration of the two emission signals, thereby reducing background noise, enhancing the signal to noise ratio, and enabling more accurate detection.[ 12 , 13 ] Excellent fluorescent probes as signal platforms are extremely important for achieving sensitive and accurate detection of target substances in fluorescence detection methods. Recently, the emergence of various luminescent nanomaterials has provided broad prospects for the development of new fluorescent sensors, including quantum dots, carbon dots, nanoclusters, and metal-organic frameworks (MOFs), which have all been reported to be synthesized and applied in the detection of Hg 2+ .[ 13 – 16 ] With large surface areas, high porosity, and structural diversity, metal-organic frameworks (MOF) are widely applied in diverse fields including magnetism, heterogeneous catalysis, and fluorescence sensing.[ 17 , 18 ] Notably, (Ln-MOFs), constructed from organic ligands and lanthanide (Ln) metal ions via coordination, exhibit unique luminescent properties such as large long fluorescence Lifetime, Stokes shifts, narrow emission band, and stable emissive energies.[ 12 , 19 ] Among of them, the luminescent europium metal–organic framework (Eu-MOF) has gained prominence as a fluorescence detection material due to its narrow emission bands, strong structural and chemical tunability, and high selectivity in recent years.[ 2 , 20 – 22 ] Under hydrothermal conditions, Chang et al. synthesized a novel Eu-MOF fluorescent material exhibiting excellent water and pH stability.[ 23 ] The prepared Eu-MOF can be successfully used to quantitatively detect Hg 2+ in real samples with high sensitivity and adsorption of Hg 2+ . The recoveries of Eu-MOF can reach 99.84–102.34%, further demonstrating excellent relative standard deviation (RSD) of less than 2.01% (n = 3). Lu et al. reported a rapid, convenient water detection method is crucial for the chemical industry. This work presents a simple strategy using a dual-emitting R6G@Eu-MOF sensor, prepared by encapsulating green-emitting Rhodamine 6G within red-emitting Eu-MOF. The sensor displays distinct fluorescence responses to organic solvents. Furthermore, using water content as input and fluorescence emissions as outputs, a one-to-two logic gate system was constructed, enabling intelligent water detection. This platform efficiently traces water and classifies polar organic solvents.[ 24 ] Graphite phase nitrogenized carbon (g-C 3 N 4 ) has garnered considerable interest as a new type of fluorescent nanomaterials, owing to its excellent luminescent performance, good light stability and low toxicity. Currently, g-C 3 N 4 composites attract increasing attention and find extensive applications in fields such as photocatalysis, electrochemical sensors, and fluorescence detection.[ 25 – 28 ] For instance, Wang et al. (In-situ growth of CeO 2 onto) have synthesized spherical g-C 3 N 4 /CeO 2 nanocomposites through in situ growth of CeO 2 nanocatalysts on g-C₃N₄ nanosheets and utilized them for a selective colorimetric detection strategy targeting Hg 2+ ions.[ 26 ] The g-C 3 N 4 substrate enhanced electron transfer in CeO 2 , yielding a nanozyme with 4-fold higher catalytic activity than pure CeO 2 . Hg 2+ selectively aggregates the nanozyme via Hg-N bonding, inhibiting catalysis proportionally to Hg 2+ concentration. As an important fluorescent nanomaterial, many studies have found that surface modification or element doping of g-C 3 N 4 can enhance visible light absorption, improve optical stability, and broaden its applications in analytical detection and biomedicine.[ 29 , 30 ] Especially, doping g-C 3 N 4 with non-metallic elements, which precludes toxic metal ion introduction and eliminates secondary pollution risks, has attracted increasing attention.[ 31 , 32 ] More recently, many reports about doping g- C 3 N 4 with S and O non-metallic elements enriches active sites and enhances visible light absorption capacity, thereby facilitating the construction of fluorescence sensing platforms.[ 25 , 31 ] Abdelhamid et al. prepared N, S, O-doped carbon dots (CDs) derived from L-cysteine by using a hydrothermal method, which exhibit blue fluorescence and selective fluorescence quenching toward Cu 2+ ions via surface aggregation.[ 33 ] The linear response and detection limit of this method is about 10–33.3 µM and 2 µM, respectively. The CDs also function as electrochemical probes. This work demonstrates their dual-function capability as sensitive/selective fluorescent sensors for Cu 2+ detection. Many researches have demonstrated that sulfur and oxygen-doped g-C 3 N 4 exhibits straightforward synthesis, environmental benignity, excellent aqueous solubility, high quantum yield, and stable fluorescence. Hence, it has great application potential in the construction of proportional fluorescence sensors. In this part, a rapid and sensitive ratio fluorescence probe for detecting Hg 2+ was constructed by encapsulating S,O-C 3 N 4 QDs in Eu-MOF. Eu-MOF was synthesized using Eu 3+ as the metal center and 1,3,5-benzenetricarboxylic acid (H 3 BTC) as the organic linker through coordination. Subsequently, S,O- C 3 N 4 QDs are encapsulated in Eu-MOF (Scheme 1 ). The fabricated S,O-C 3 N 4 QDs/Eu-MOF ratiometric fluorescent probe exhibits distinct and stable emission bands at 619 nm and 445 nm. When Hg 2+ was added to the S,O-C 3 N 4 QDs/Eu-MOF system, the fluorescence intensity at 445 nm progressively decreases due to static quenching, whereas the emission intensity at 619 nm remains constant. This distinct ratiometric response enables the quantitative detection of Hg 2+ . Experimental section Chemicals reagents The EuCl 3 ·6H 2 O, citric acid (C 9 H 6 O 6 ), Benzene-1,3,5-tricarboxylic acid (H 3 BTC), acetic acid sodium salt (CH 3 COONa), thiourea (CH 4 N 2 S) and ethanol (C 2 H 6 O) were sourced from Shanghai Aladdin Reagent Co., Ltd. Metal salts (NaCl, CuCl 2 , CoCl 2 , NiCl 2 , FeCl 3 , FeCl 2 , MnCl 2 , MgCl 2 , AgNO 3 , HgCl 2 , Na 2 SO 4 , Na 2 CO 3 , KNO 3 , Na 3 PO 4 3− ) and Lysine (Lys), Arginine (Arg), Glutamic Acid (Glu), Glycine (Gly) were acquired from Sinopharm Chemical Reagent Co., Ltd. (PR China). All the reagents used in this work were analytically pure and did not undergo further purification. Deionized water (> 18 MU) used in this experiment was supplied by an ultrapure water system. Characterization Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) imaging was performed on Nippon Electron JEM-F200 (Japan) operating at 200 kV. Powder X-ray diffraction (PXRD) patterns were obtained on D-MAX 2500/PC ༈Rigaku, Japan) with Cu Kα radiation (40 kV, 40 mA). Fourier transform infrared (FT-IR) spectroscopy was conducted on KBr pellets using a Digilab FTS-3000 IR spectrometer. The optical properties of the synthesized S,O-C 3 N 4 QDs/Eu-MOF were characterized using an Ultraviolet-visible Spectrophotometer (Hitachi, Japan). the chemical valence states of the surface elements of the MnCeX nanozymes were recorded by X-ray photoelectron spectroscopy (XPS) (ThermoFisher, 250Xi, USA). Sample Preparation Eu-MOF synthesis . The Eu-MOF were obtained by a simple optimized solvothermal way with reference to the published literature.[ 34 ] EuCl 3 ·6H 2 O (36.6 mg, 0.1 mmol) and CH₃COONa (15 mg) were dissolved in 10 mL of deionized water with stirring to form solution A. Separately, H 3 BTC (21 mg, 0.1 mmol) was added to ethanol (10 mL) under ultrasonication to yield solution B. Solution A was then added dropwise to solution B under continuous stirring. The resulting mixture was vigorously stirred for 1 hour. The white precipitate was collected by centrifugation (8000 rpm, 10 min, room temperature), washed sequentially with CH 3 CH 2 OH and deionized water (6 cycles), and finally dried under ambient conditions to obtain the Eu-MOF product. Synthesis of S,O-C 3 N 4 QDs . S,O-C 3 N 4 QDs were synthesized via a hydrothermal method. Specifically, C 9 H 6 O 6 (0.21 g) and CH 4 N 2 S (0.26 g) were dissolved in 20 mL of distilled water under stirring. The combined solution was transferred to a Teflon-lined autoclave with the volume 25 mL and subjected to hydrothermal treatment at 200°C for 2 h. After cooling to ambient temperature, the resulting product was dispersed in 50 mL of distilled water. The resulting aqueous dispersion was then centrifuged at 15,000 rpm for 10 min remove insoluble residues. Subsequently, the supernatant was filtered through a 0.22 µm microporous membrane to afford a brownish-yellow solution. To purify the QDs, this solution was dialyzed against distilled water for 24 h by using a dialysis membrane (molecular weight cut-off: 500 Da) to obtain purified S,O-C 3 N 4 QDs. Finally, the dialyzed solution was freeze-dried to afford the solid S,O-C 3 N 4 QDs. Synthesis of S,O-C 3 N 4 QDs/Eu-MOF . The S,O-C 3 N 4 QDs /Eu-MOF composite was prepared following a procedure analogous to that of the pristine Eu-MOF, with a key modification. Specifically, 5 mg of S,O-C 3 N 4 QDs were introduced into Solution A during its preparation. All subsequent steps were identical to those employed for the synthesis of Eu-MOF. Ratiometric Fluorescence Detection of Hg The Hg²⁺ detection procedure using the S,O-C 3 N 4 QDs /Eu-MOF ratiometric fluorescence probe was performed as follows. First, 1.0 mL of the S,O-C 3 N 4 QDs /Eu-MOF suspension was placed in a 3 mL quartz cuvette. Subsequently, varying volumes of Hg 2+ standard solution (10 − 3 M) were introduced. The total volume was then adjusted to 2.0 mL with Tris-HCl buffer solution. After incubation for 4 min, fluorescence emission spectra were recorded at an excitation wavelength of 370 nm. The detection limit (LOD) for Hg 2+ was calculated according to the equation LOD = 3σ/k, where σ represents the standard deviation of 11 consecutive blank measurements, and k denotes the slope of the ratiometric signal (F 445 /F 619 ) vs. Hg 2+ concentration calibration curve. Selectivity anti-interference ability, and stability test To evaluate the selectivity of the S,O-C 3 N 4 QDs/Eu-MOF ratiometric probe towards Hg 2+ and its anti-interference capability against potential coexisting species, competitive binding assays were performed. Specifically, the response of the probe was measured in the presence of various analytes: amino acids (Gly, Ala, Glu, Lys), anions (Cl ⁻ , CO 3 2⁻ , SO 4 2⁻ , PO 4 3⁻ , NO 3 ⁻ ), cations (Ag + , Mg 2+ , Mn 2+ , Cu 2+ , Ni 2+ , Co 2+ , Fe 3+ , Fe 2+ ). To ensure statistical reliability, triplicate independent measurements were conducted for each condition. The stability of the S,O-C 3 N 4 QDs/Eu-MOF ratiometric probe was systematically evaluated under four distinct conditions: (i)Photostability: continuous exposure to 365 nm ultraviolet irradiation for 60 min; (ii) Ionic strength tolerance: dispersion in NaCl solutions with various concentration (100–1000 mM); (iii) pH stability: dispersion in buffer solutions spanning a pH range (pH 4–10); (iv) Long-term storage stability: ambient storage at 25°C for 60 days. Fluorescence spectra were periodically recorded to quantify the ratiometric signal intensity (F 445 /F 619 ) under each condition. Real sample analysis Actual water samples employed in this study comprised lake water collected from Yingze Park and laboratory tap water. The obtained water was filtered and then heated to boiling for 30 minutes. After cooling to ambient temperature, the solution was filtered through a 0.22 µm microporous membrane and stored at 4°C for subsequent use. Both the blood and urine samples were obtained from healthy adult volunteers. Fresh urine samples were centrifuged (12,000 × g) for 20 min. The supernatant was subsequently diluted 1000-fold with 10 mM Tris-HCl buffer (pH 9.0) for short-term storage at 4°C. Add an equal volume of acetonitrile solution to the blood sample and stir evenly. After standing for 3 minutes, centrifuge for 10 minutes. Filter the supernatant with a 0.22 µm microporous filter membrane. Finally, dilute it 100 times with Tris-HCl buffer salt solution (10 mM, pH = 9) and store it in a 4°C refrigerator for later use. Standard tetracycline solutions (2.5, 10, 30 µM) were added to treated lake water, tap water, blood and urine samples for further analysis. Results and discussion The characterization analyses of the synthesis nanomaterials The structure properties of the prepared materials were studied by TEM, HRTEM and XRD. As shown in Figure 1a, Eu-MOF showed a rod-like morphology and its diameter is approximately 60nm. Following the encapsulation of S,O-co-doped carbon nitride quantum dots (S,O-C 3 N 4 QDs), the Eu-MOF maintained their structural integrity while exhibiting uniformly dispersed nanoparticles anchored on their surfaces (Figure 1b). 22 The HRTEM characterization presented in Figure 1c reveals clear lattice streaks with a lattice spacing of 0.33 nm, corresponding to the characteristic (002) crystal plane of S,O-C 3 N 4 QDs. This result clearly confirms the successful encapsulation of S, O-C 3 N 4 quantum dots within Eu-MOF.[20] The XRD pattern was also performed to analyses the crystal structure of Eu-MOF and S,O-C 3 N 4 QDs/Eu-MOF. As displayed in Figure 1d, it shows multiple sharp characteristic diffraction peaks of Eu-MOF and S,O-C 3 N 4 QDs/Eu-MOF within the range of 5-40°, which were closely matched the corresponding standard simulated peaks of Eu-MOF (CCDC No. 290771 and 147248).[34,35] Comparative XRD analysis of the Eu-MOF and S,O-C 3 N 4 QDs/Eu-MOF composite demonstrates the diffraction patterns with peak positions (2θ = 5.3°, 10.7°, 16.2°) essentially identical to pristine Eu-MOF (Δθ < 0.2°)，indicating that the successful encapsulation of S,O-C₃N₄ QDs within the Eu-MOF matrix has while preserving the structural integrity of the MOF framework, as evidenced by TEM imaging (Figure 1b) results. The FT-IR spectrum was carried out to further study the functional groups of the prepared samples. As presented in Figure 1e, the characteristic peaks appeared around 3410 cm −1 is belonged to the Eu-MOF due to the stretching vibrations of O-H and N-H. 36 In addition, the characteristic peaks were observed at 1373 cm −1 , 1436 cm −1 , 1560 cm −1 , and 1612 cm −1 can be assigned to assigned to the symmetric and anti-symmetric stretching vibration of the carboxyl group, respectively.[34,37] Furthermore, S,O-C 3 N 4 QDs/Eu-MOF exhibited characteristic peaks at 2064 cm cm − 1 , which verifies that S,O-C 3 N 4 QDs was successfully incorporated into Eu-MOF. XPS analysis was employed to further investigate the elements changes during the synthesis process of the S,O-C 3 N 4 QDs/Eu-MOF. As shown in Figure 1f, the full survey spectra demonstrated that the elements in Eu-MOF include Eu, O and C, the S,O-C 3 N 4 QDs contains only four elements: C, N, S and O.[38-40] With the S,O-C 3 N 4 QDs successful encapsulation in Eu-MOF, N and S elements appear in S,O-C 3 N 4 QDs/Eu-MOF, which is in agreement with the FT-IR results.[41] Figure 2a-d showed the XPS high-resolution spectrum of S,O-C 3 N 4 QDs/Eu-MOF. As exhibition in Figure 2a, there was five split peaks appeared at 284.6 eV, 284.9 eV, 285.5 eV, 288.6 eV and 289.0 eV, which were abscribed to the binding enery of C=C, C-C/C-H, C-OH/C-O-C, C=O and COOH.[42] As can be observed in Figure 2b, N 1s showed obvious spectral peaks at 400.7 eV and 401.8 eV, which belonged to N–H and N–O binding energy, respectively.[43] In the O 1 s energy spectrum (Figure 2c), the binding energy located at 532.1 eV and 533.2 eV are determined to be C–O and C=O bond. For the Eu 3d highresolution spectrum (Figure 2d), it can be deconvoluted into four peaks. Among them, the peaks at 1165.1 eV and 1157.6 eV are belong to Eu 3d 3/2 , the characteristic peaks located at 1135.2 eV eV are caused by the binding energy of Eu 3 d5/2 .[44] Additionaly, the peak with the binding energy is 1143.2 eV should be attributed to the satellite signal.[2] These characterization consequences collectively confirmed that the successful syntheis of dual ligands MOFs. Eu-MOF fluorescence emission spectra were investigated at different excitation wavelengths. Figure 3a reveals weak fluorescence emission peaks at 595 nm and 690 nm under excitation at different wavelengths, while a strong peak is observed at 619 nm. Notably, the results in Fgiure 3a demonstrate a prominent fluorescence emission peak located at 619 nm. It is worth noting that the fluorescence intensity exhibits excitation wavelength-dependent behavior, showing an initial enhancement followed by gradual attenuation as the excitation wavelength increases. The maximum emission intensity was observed at an optimal excitation wavelength of 265 nm, indicating wavelength-specific activation characteristics of the material. The UV-vis absorption spectra and fluorescence spectra of the S,O-C 3 N 4 QDs/Eu-MOF were shown in Figure 3b. In UV spectra, S,O-C 3 N 4 QDs/Eu-MOF reveals two distinct electronic transition features: the sharp absorption band centered at 200 nm is assignable to π-π * electronic transitions of C=C bonds, whereas the broader peaks extending to 340 nm originates from n-π* electronic transitions associated with C=O moieties in the nanostructure. [22, 24] As evidenced by the spectral analysis in Figure 3b, under 370 nm excitation, S,O-C 3 N 4 QDs/Eu-MOF composite probe maintained the characteristic emission of S,O-C 3 N 4 QDs at 450 nm while simultaneously exhibiting three distinct emission bands at 595 nm, 619 nm, and 690 nm. These longer wavelength emissions correspond to the typical electronic transitions of Eu³⁺ ions.[2,15] Apparently, the above analysis results confirmed that S,O-C 3 N 4 QDs was successfully incorporated into Eu-MOF. Optimum of experimental conditions In order to obtain optimal conditions for sensing Hg 2 , the experimental parameters such as the concentration of S,O-C 3 N 4 QDs/Eu-MOF and reaction time were systematically investigated. As shown in Figure 4a, the F 619 /F 445 ratio exhibited an inverse linear dependence on Hg 2+ concentration over the range of 0.1–35 µM. Notably, the slope of the linear correlation between the ratio F 619 /F 445 and Hg 2+ concentration exhibited a distinct concentration-dependent behavior. As the concentration of S,O-C 3 N 4 QDs/Eu-MOF increased from 13 to 17 μg/mL, the slope value initially showed a progressive enhancement, reaching maximum responsiveness at 15 μg/mL, followed by a subsequent decline at higher concentrations. Hence, the concentration of 15 μg/mL was chosen for subsequent experiment. Response time of the fluorescence intensity of S,O-C 3 N 4 QDs/Eu-MOF after the addition of Hg 2+ was exhibited in Figure 4b. It can be found that the fluorescence intensity ratio of F 619 /F 445 achieved stabilization within 4 minutes and maintained this equilibrium state throughout the subsequent 30 minutes monitoring period. Based on these observations, 4 minutes was selected for all subsequent analytical measurements to ensure optimal sensing responsiveness. Fluorescence detection of Hg 2+ To evaluate the sensitivity enhancement achieved through S,O-C 3 N 4 QDs/Eu-MOF-based ratiometric fluorescence detection for Hg 2+ , a comparative study was carried out by using single-emission S,O-C 3 N 4 QDs as the reference sensing platform. Figure 5a delineates the concentration-dependent fluorescence quenching behavior of S,O-C 3 N 4 QDs upon interaction with Hg 2+ ions within the concentration range of 0-160 μM. As illustrated in Figure 5a, with the increase of Hg 2+ concentration, the fluorescence intensity at 445 nm gradually decreases, which indicated that the emission at 445 nm of S,O-C 3 N 4 QDs was quenched by Hg 2+ . The Figure 5b exhibits a linear dependence of 1/(F 0 - F) on concentration of 1/C Hg 2+ , among them, F 0 and F represent the fluorescence intensity values at 445 nm in the absence and presence of Hg 2+ , respectively, and C Hg2+ is the concentration of Hg 2+ . linear relationship between the reciprocal of fluorescence intensity difference (1/(F 0 -F 1 )) and the inverse of mercury ion concentration (1/C Hg2+ ), where F 0 represents the baseline fluorescence intensity at 445 nm in the absence of Hg 2+ , while F 1 denotes the corresponding fluorescence intensity measured in the presence of Hg 2+ . The regression equation is established: 1/(F 0 -F 1 ) = 0.0427 C Hg2+ + 0.0014, while the concentration of Hg 2+ under the range of 0.0 ~ 160 μM. The LOD for Hg 2+ was calculated to be 0.172 μM based on the equation of LOD=3σ/K. As shown in Figure 5c, with the increase of Hg 2+ concentration, the fluorescence intensity of S,O-C 3 N 4 QDs/Eu-MOF at 445 nm decreased significantly, whereas the emission intensity at 619 nm exhibited negligible variation across the tested concentration range. Figure 6a displays the dual-wavelength fluorescence response (445/619 nm) of the sensor system to Hg 2+ concentrations, paralleling the spectral evolution patterns demonstrated in Figure 5c. The concentration-dependent response of the F 619 /F 445 ratio to Hg 2+ is presented in Figure 6b. The calibration curve exhibited two distinct linear correlations across different concentration ranges of Hg 2+ , i.e. in the range from 0.25 to 4 μM (R 2 = 0.9935) and from 4 to 35 μM (R 2 = 0.9961). These relationships indicate that there is a strong linear dependence between the fluorescence intensity ratio and the mercury ion concentration, and the correlation coefficients in both concentration domains exceed 0.99. The LOD for Hg 2+ was calculated to be 4.3 nM. The comparative analysis reveals that the S,O-C 3 N 4 QDs/Eu-MOF composite demonstrates significantly superior Hg 2+ sensing performance relative to its individual S,O-C 3 N 4 QDs counterpart. The detection range and LOD of S,O-C 3 N 4 QDs/Eu-MOF are compared with the previously reported platform and summarized in Table 1. As shown in Table 1, the S,O-C 3 N 4 QDs/Eu-MOF exhibits high sensitivity (LOD of 4.3 nM) within the range of 0.25–35 µM, which indicate that doping g-C 3 N 4 quantum dots with S and O and encapsulating them in Eu-MOF can effectively improve the sensitivity of detecting Hg 2+ . Table 1 Comparison of different probes for Hg 2+ detection based the ratiometric intensity Probe Liner range (μM) LOD refs luminol -Eu-IPA CPNPs 0.05–20 13.2 nM [45] BYCDs 0.95–50 270 nM [46] rhodamine B- carbon quantum dots 10–70 3.3 nM [47] Eu-Ca-MOF 0.02-200 2.6 nM [48] Laponite-Eu-Cit 0.4–1.2 30 nM [49] S,O-C 3 N 4 QDs/Eu-MOF 0.25–35 4.3 nM This work Selectivity, anti-interference ability, and stability In order to understand the selectivity and the anti-interference ability of the S,O-C 3 N 4 QDs/Eu-MOF system for detecting Hg 2+ , some common interferents such as metal ions (Na + , Ag + , Ni 2+ , Cu 2+ , Mg 2+ , Mn 2+ , Fe 2+ , Co 2+ , and Fe 3+ ), anions (Cl − , NO 3 − , SO 4 2− , and CO 3 2− ), and some amino acids (Lys, Arg, Glu, Gly, and Ala) are tested in this work. Figure 7 shows the intensity ratio of F 445 /F 619 for Hg 2+ and other interferents, respectively. It is noteworthy that Hg 2+ causes significant changes for F 445 /F 619 , wheras other interferents exhibit negligible changes. Eventually, the anti-interference ability of the S,O-C 3 N 4 QDs/Eu-MOF after mixing Hg 2+ with various coexisting intererents was further evaluated. The analytical findings demonstrate that these interferents exert negligible interference on Hg 2+ detection sensitivity. The exceptional selectivity of this sensing platform originates from the specific interaction between S,O-C 3 N 4 QDs/Eu-MOF and Hg 2+ makes this platform have high practical applications for detection Hg 2+ in real samples. The fluorescence stability of the S,O-C 3 N 4 QDs/Eu-MOF were further studied under four distinct environmental conditions to evaluate its practical applicability: (a) continuous exposure to 365 nm ultraviolet irradiation for 60 minutes to assess photostability, (b) immersion in aqueous NaCl solutions with varying ionic strengths (0.1-1.0 M) to examine electrolyte tolerance, (c) dispersion in buffer solutions within a pH range of 3.0-11.0 to evaluate acid-base stability, and (d) long-term ambient storage (25°C, 60 days) to monitor time stability. As shown in Figure 8, S,O-C 3 N 4 QDs/Eu-MOF shows good fluorescence stability under UV irradiation, wide pH ranges, high salt conditions, and long time. Hence, its good fluorescence stability makes the use of S,O-C 3 N 4 QDs/Eu-MOF in practical applications. Mechanisms of detecting Hg 2+ by S,O-C 3 N 4 QDs/Eu-MOF The sensing mechanism of fluorescence response of the S,O-C 3 N 4 QDs/Eu-MOF is further investigated toward Hg 2+ . Figure 9a depicts the temperature dependence (300-320 K) of the Stern-Volmer plot for S,O-C 3 N 4 QDs- Hg 2+ system. The slope revealing an inverse relationship between temperature and the quenching constant, which indicated diminished collisional quenching efficiency at higher thermal energy levels. Comprehensive surface analysis via FTIR and XPS spectra (Figure 1e and Figure 1f), reveals that there were large numbers of carbonyl, hydroxyl and carboxylic groups on S,O-C 3 N 4 QDs surfaces, suggesting the possible electrostatic interactions between S,O-C 3 N 4 QDs and Hg 2+ . Hg 2+ exhibits strong binding affinity toward surface functional groups (e.g., carboxyl groups), forming non-fluorescent complexes via chelation that induce fluorescence quenching. As demonstrated in the Figure 9b, UV-Vis absorption spectra of S,O-CNQDs show concentration-dependent attenuation (0.0–35 μM Hg 2+ ), suggesting complex formation between Hg²⁺ and quantum dots. In order to further investigate the interaction mechanism between S,O-C 3 N 4 QDs and Hg 2+ , the fluorescence lifetimes of S,O-C 3 N 4 QDs with different concentrations of Hg 2+ were shown in the Figure 9c. The average lifetime of S,O-C 3 N 4 QDs were basically unchanged with the increasing of the concentration of Hg 2+ . This result confirm that static quenching was considered the mechanism for the S,O-C 3 N 4 QDs probe.[50,51] Determination of Hg 2+ in real sample The practical application of the S,O-C 3 N 4 QDs/Eu-MOF system is evaluated by a recovery test of Hg 2+ spiked blood, urine, lake water and tap water samples, the consequences are listed in Table 2. Table 2 demonstrates that good recoveries (96 ~ 108%) and satisfactory RSDs (6 ~ 32%) are obtained from this detection model. This result indicated that S,O-C 3 N 4 QDs/Eu-MOF has better accuracy and higher reliability, which can be used for the determination of Hg 2+ in actual samples. Table 2 Determination of Hg 2+ with S,O-C 3 N 4 QDs/Eu-MOF in real samples Sample Concentration of Hg 2+ Recovery (%) RSD (%,n=3) Added (μM) Found (μM) Blood sample 2 2.17 108 0.13 5 5.12 102 0.32 20 19.85 99 0.21 Urine sample 2 1.93 96 0.12 5 5.09 101 0.10 20 20.36 101 0.07 Lake water 2 2.05 102 0.15 5 4.98 99 0.24 20 20.33 102 0.06 Tap water 2 2.11 105 0.16 5 4.78 96 0.25 20 19.27 96 0.18 Conclusion In summary, a novel probe (S,O-C 3 N 4 QDs/Eu-MOF) was successfully synthesized to detect Hg 2+ . The synthesized probe exhibited dual-emission at wavelengths of 445 nm and 619 nm, respectively. As the Hg 2+ concentration increases, the emission at 445 nm of S,O-C 3 N 4 QDs/Eu-MOF decreases gradually, whereas that of u-MOF at 619 nm remains constant. The fluorescence of S,O-C 3 N 4 QDs/Eu-MOF at 445 nm was quenched by Hg 2+ due to static quenching. According to the intensity ratio (I 445 / I 619 ), a feasible detection method was established for Hg 2+ detection, the linear range of S,O-C 3 N 4 QDs/Eu-MOF + Hg 2+ was 0.25–35 µM with a LOD 4.3 nM. Moreover, the S,O-C 3 N 4 QDs/Eu-MOF was successfully applied for the detection of Hg 2+ in real samples such as blood, urine, lake water and tap water samples with the recoveries of 96 ~ 108% and the satisfactory RSDs (6 ~ 32%). Overall, the prepared nanoprobes have high sensitivity, excellent selectivity and anti-interference ability for Hg 2+ . These satisfying results in this work demonstrates an effective fluorescence sensor for Hg 2+ detection and highlight the potential of S,O- C 3 N 4 QDs /Eu-MOF composites in environmental monitoring applications. Declarations Conflicts of interest There are no conflicts of interest to declare. Author Contribution Jie Yao: writing, review and editing, formal analysis. Hongfang Chen: writing, original draft, investigation, data curation. Xiaohua Yang: data curation. Muzaffar Iqbal: writing, review and editing, Wei Bian: writing, review and editing, funding acquisition. Acknowledgements This work was supported by Natural Science Foundation of Shanxi Province of China (202403021212220, 202203021221186, 201901D111210), the Shanxi Province Higher Education "Billion Project" Science and Technology Guidance Project (BYJL025) and the Central Government Guides Local Funds for Science and Technology Development (YDZJSX2024C028), Ongoing Research Funding Program(ORF-2025-734), King Saud University, Riyadh, Saudi Arabia. Data availability The raw/processed data required to reproduce these findings cannot beshared at this time as the data also forms part of an ongoing study. References J. Wang, M. Shen, F. Meng, X. Han, M. Zhang (2025) A portable paper-based analytical device mediated by transition metal selenide nanozymes based on Hg 2+ -activated oxidase-like activity. Chem. Eng. J 512: 162683. Q. Song, L. Wang, J. Zhang, Y. 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Cite Share Download PDF Status: Published Journal Publication published 25 Aug, 2025 Read the published version in Journal of Fluorescence → Version 1 posted Editorial decision: Revision requested 09 Jul, 2025 Reviews received at journal 09 Jul, 2025 Reviews received at journal 04 Jul, 2025 Reviews received at journal 03 Jul, 2025 Reviewers agreed at journal 01 Jul, 2025 Reviewers agreed at journal 28 Jun, 2025 Reviewers agreed at journal 26 Jun, 2025 Reviewers invited by journal 26 Jun, 2025 Editor assigned by journal 24 Jun, 2025 Submission checks completed at journal 24 Jun, 2025 First submitted to journal 20 Jun, 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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02:23:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6942147/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6942147/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10895-025-04535-0","type":"published","date":"2025-08-25T15:57:19+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":85723003,"identity":"d5dbb139-ac6a-4ec2-a449-449362b51455","added_by":"auto","created_at":"2025-07-01 06:00:57","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":690640,"visible":true,"origin":"","legend":"\u003cp\u003eTEM, HRTEM images of the prepared nanomaterials: (a) Eu-MOF; (b) S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF; (c) S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF, (d), (e), (f): PXRD patterns, FT-IR spectra, XPS survey of synthesized Eu-MOF, S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs, S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs/Eu-MOF.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6942147/v1/b39346c910131d79bc3d745b.png"},{"id":85723001,"identity":"d5e0a417-6f75-4e61-9547-87def33f22aa","added_by":"auto","created_at":"2025-07-01 06:00:56","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":90622,"visible":true,"origin":"","legend":"\u003cp\u003eXPS spectra of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs/Eu-MOF: (a) C 1S, (b) N 1S, (c) O1S, (d) Eu 3d\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6942147/v1/8038d4ddd68bdbc980838285.png"},{"id":85723969,"identity":"00ceda56-1c25-473c-8d33-4d8737c70cc2","added_by":"auto","created_at":"2025-07-01 06:08:57","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":163865,"visible":true,"origin":"","legend":"\u003cp\u003ea: Fluorescence emission spectra of Eu-MOF, b: UV-vis spectrum, the excitation spectrum and the emission spectrum of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6942147/v1/c742a326f290b96431149bf5.png"},{"id":85723008,"identity":"9cb8b238-a055-4e12-9421-27d7d486ddb9","added_by":"auto","created_at":"2025-07-01 06:00:57","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":52139,"visible":true,"origin":"","legend":"\u003cp\u003ea:The influence of different concentrations of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF on the detection of Hg\u003csup\u003e2+\u003c/sup\u003e, b: Response time of the fluorescence intensity of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF after the addition of Hg\u003csup\u003e2+\u003c/sup\u003e of 15 μM\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6942147/v1/700cda2181eb1890588e697d.png"},{"id":85723006,"identity":"02e9a5d3-7bbe-410a-bba4-f93399e003da","added_by":"auto","created_at":"2025-07-01 06:00:57","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":97882,"visible":true,"origin":"","legend":"\u003cp\u003ea: The influence of different concentrations of Hg\u003csup\u003e2+\u003c/sup\u003e on the fluorescence spectra of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs, b: The Lineweaver-Burk standard curve of Hg\u003csup\u003e2+\u003c/sup\u003e and S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs, c: The influence of different concentrations of Hg\u003csup\u003e2+\u003c/sup\u003e on the fluorescence spectra of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6942147/v1/4608094621256bbc990fada7.png"},{"id":85723009,"identity":"e124f84f-cf34-447c-82c4-e6ce1e677f9f","added_by":"auto","created_at":"2025-07-01 06:00:57","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":281400,"visible":true,"origin":"","legend":"\u003cp\u003ea: Luminescence intensities of 445 and 619 nm in S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF with different concentrations of Hg\u003csup\u003e2+\u003c/sup\u003e, b: The linear relationship between the ratiometric intensity (F\u003csub\u003e445\u003c/sub\u003e/F\u003csub\u003e619\u003c/sub\u003e) of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF and Hg\u003csup\u003e2+\u003c/sup\u003e concentration\u003c/p\u003e","description":"","filename":"floatimage7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6942147/v1/a6469feaa5cb06ec6882f23e.jpeg"},{"id":85723028,"identity":"f12ef535-ab4a-4287-abbf-0884f6c0e91a","added_by":"auto","created_at":"2025-07-01 06:00:57","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":152118,"visible":true,"origin":"","legend":"\u003cp\u003eF\u003csub\u003e445\u003c/sub\u003e/F\u003csub\u003e419\u003c/sub\u003e ratios of the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF system with Hg\u003csup\u003e2+\u003c/sup\u003e ions and interferents.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-6942147/v1/150fd584d1571b247cceed23.png"},{"id":85723015,"identity":"9d7a75fd-7474-4d07-8766-d6e5e3afc972","added_by":"auto","created_at":"2025-07-01 06:00:57","extension":"jpeg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":305729,"visible":true,"origin":"","legend":"\u003cp\u003eThe stablity of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF under different conditions: (a) continuous irradiation with ultraviolet lamps for 30 minutes at 365 nm, (b) under diferent concentration of NaCl, (c) at different pH values, (d) storage time\u003c/p\u003e","description":"","filename":"floatimage9.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6942147/v1/003de9ba90adefc310470d3f.jpeg"},{"id":85723974,"identity":"394eac4e-1537-4f0c-9b40-1659c8cc87f8","added_by":"auto","created_at":"2025-07-01 06:08:57","extension":"jpeg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":278754,"visible":true,"origin":"","legend":"\u003cp\u003ea: The influence of temperature on the detection of Hg\u003csup\u003e2+\u003c/sup\u003e by S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs, b: The effect of different concentrations of Hg\u003csup\u003e2+\u003c/sup\u003e on the UV absorption spectra of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs, c:The fluorescence lifetime curve of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs with and without Hg\u003csup\u003e2+\u003c/sup\u003e addition\u003c/p\u003e","description":"","filename":"floatimage10.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6942147/v1/448da4d9b4919a9d341461b3.jpeg"},{"id":90345000,"identity":"ccfab5ad-bde3-4549-a5ae-6ef4f68cdd6d","added_by":"auto","created_at":"2025-09-01 16:09:05","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2989113,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6942147/v1/75fc28c8-b0b2-4bca-8dc2-2edc5160df8b.pdf"},{"id":85723005,"identity":"da3cefeb-d43e-4e8d-a3db-79e919fafe20","added_by":"auto","created_at":"2025-07-01 06:00:57","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":202953,"visible":true,"origin":"","legend":"\u003cp\u003eScheme 1. Process of NS-CDs/AgNCs synthesis and Hg\u003csup\u003e2+\u003c/sup\u003e detection.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6942147/v1/89e413700df8912caa90199f.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eConstruction of S,O-Doped g-C\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eN\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e4\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e Encapsulated in Eu-MOF with Dual-Emission for Ratiometric Fluorescence Detection of Hg²⁺\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eMercury ions (Hg\u003csup\u003e2+\u003c/sup\u003e) are persistent global environmental pollutant that can pose a significant risk to human health through the food chain.[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] The enrichment of Hg\u003csup\u003e2+\u003c/sup\u003e in the human body can cause severe immunotoxicity, genotoxicity and neurotoxicity to the human by forming stable complexes with enzymes and thiols in proteins.[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] Therefore, establishing a sensitive and accurate method for detecting Hg\u003csup\u003e2+\u003c/sup\u003e has great significance for human health and ecological security.\u003c/p\u003e \u003cp\u003eCurrently, there are many reported methods for detecting trace amounts of Hg\u003csup\u003e2+\u003c/sup\u003e, such as high performance liquid chromatography, cold atomic absorption spectrometry, inductively coupled plasma mass spectrometry, capillary electrophoresis and fluorescence methods.[\u003cspan additionalcitationids=\"CR5 CR6\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] Among these methods, fluorescence method has great application potential in practical applications due to its lots of advantages, such as high sensitivity, excellent efficiency, convenient operation and low cost.[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] The traditional fluorescence detection method relies on single fluorescence transmission signal, which is prone to environmental interference, resulting in unstable experimental signals and being unfavorable for conducting multiple experiment.[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] Compared with single fluorescence signal detection, the dual-emission fluorescence probe minimizes environmental interference and intrinsic concentration-dependent errors through self-calibration of the two emission signals, thereby reducing background noise, enhancing the signal to noise ratio, and enabling more accurate detection.[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] Excellent fluorescent probes as signal platforms are extremely important for achieving sensitive and accurate detection of target substances in fluorescence detection methods.\u003c/p\u003e \u003cp\u003eRecently, the emergence of various luminescent nanomaterials has provided broad prospects for the development of new fluorescent sensors, including quantum dots, carbon dots, nanoclusters, and metal-organic frameworks (MOFs), which have all been reported to be synthesized and applied in the detection of Hg\u003csup\u003e2+\u003c/sup\u003e.[\u003cspan additionalcitationids=\"CR14 CR15\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] With large surface areas, high porosity, and structural diversity, metal-organic frameworks (MOF) are widely applied in diverse fields including magnetism, heterogeneous catalysis, and fluorescence sensing.[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] Notably, (Ln-MOFs), constructed from organic ligands and lanthanide (Ln) metal ions via coordination, exhibit unique luminescent properties such as large long fluorescence Lifetime, Stokes shifts, narrow emission band, and stable emissive energies.[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] Among of them, the luminescent europium metal\u0026ndash;organic framework (Eu-MOF) has gained prominence as a fluorescence detection material due to its narrow emission bands, strong structural and chemical tunability, and high selectivity in recent years.[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] Under hydrothermal conditions, Chang et al. synthesized a novel Eu-MOF fluorescent material exhibiting excellent water and pH stability.[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] The prepared Eu-MOF can be successfully used to quantitatively detect Hg\u003csup\u003e2+\u003c/sup\u003e in real samples with high sensitivity and adsorption of Hg\u003csup\u003e2+\u003c/sup\u003e. The recoveries of Eu-MOF can reach 99.84\u0026ndash;102.34%, further demonstrating excellent relative standard deviation (RSD) of less than 2.01% (n\u0026thinsp;=\u0026thinsp;3). Lu et al. reported a rapid, convenient water detection method is crucial for the chemical industry. This work presents a simple strategy using a dual-emitting R6G@Eu-MOF sensor, prepared by encapsulating green-emitting Rhodamine 6G within red-emitting Eu-MOF. The sensor displays distinct fluorescence responses to organic solvents. Furthermore, using water content as input and fluorescence emissions as outputs, a one-to-two logic gate system was constructed, enabling intelligent water detection. This platform efficiently traces water and classifies polar organic solvents.[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eGraphite phase nitrogenized carbon (g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e) has garnered considerable interest as a new type of fluorescent nanomaterials, owing to its excellent luminescent performance, good light stability and low toxicity. Currently, g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e composites attract increasing attention and find extensive applications in fields such as photocatalysis, electrochemical sensors, and fluorescence detection.[\u003cspan additionalcitationids=\"CR26 CR27\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] For instance, Wang et al. (In-situ growth of CeO\u003csub\u003e2\u003c/sub\u003e onto) have synthesized spherical g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e/CeO\u003csub\u003e2\u003c/sub\u003e nanocomposites through in situ growth of CeO\u003csub\u003e2\u003c/sub\u003e nanocatalysts on g-C₃N₄ nanosheets and utilized them for a selective colorimetric detection strategy targeting Hg\u003csup\u003e2+\u003c/sup\u003e ions.[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] The g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e substrate enhanced electron transfer in CeO\u003csub\u003e2\u003c/sub\u003e, yielding a nanozyme with 4-fold higher catalytic activity than pure CeO\u003csub\u003e2\u003c/sub\u003e. Hg\u003csup\u003e2+\u003c/sup\u003e selectively aggregates the nanozyme via Hg-N bonding, inhibiting catalysis proportionally to Hg\u003csup\u003e2+\u003c/sup\u003e concentration. As an important fluorescent nanomaterial, many studies have found that surface modification or element doping of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e can enhance visible light absorption, improve optical stability, and broaden its applications in analytical detection and biomedicine.[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] Especially, doping g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with non-metallic elements, which precludes toxic metal ion introduction and eliminates secondary pollution risks, has attracted increasing attention.[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e] More recently, many reports about doping g- C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with S and O non-metallic elements enriches active sites and enhances visible light absorption capacity, thereby facilitating the construction of fluorescence sensing platforms.[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] Abdelhamid et al. prepared N, S, O-doped carbon dots (CDs) derived from L-cysteine by using a hydrothermal method, which exhibit blue fluorescence and selective fluorescence quenching toward Cu\u003csup\u003e2+\u003c/sup\u003e ions via surface aggregation.[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] The linear response and detection limit of this method is about 10\u0026ndash;33.3 \u0026micro;M and 2 \u0026micro;M, respectively. The CDs also function as electrochemical probes. This work demonstrates their dual-function capability as sensitive/selective fluorescent sensors for Cu\u003csup\u003e2+\u003c/sup\u003e detection. Many researches have demonstrated that sulfur and oxygen-doped g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e exhibits straightforward synthesis, environmental benignity, excellent aqueous solubility, high quantum yield, and stable fluorescence. Hence, it has great application potential in the construction of proportional fluorescence sensors.\u003c/p\u003e \u003cp\u003eIn this part, a rapid and sensitive ratio fluorescence probe for detecting Hg\u003csup\u003e2+\u003c/sup\u003e was constructed by encapsulating S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs in Eu-MOF. Eu-MOF was synthesized using Eu\u003csup\u003e3+\u003c/sup\u003e as the metal center and 1,3,5-benzenetricarboxylic acid (H\u003csub\u003e3\u003c/sub\u003eBTC) as the organic linker through coordination. Subsequently, S,O- C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs are encapsulated in Eu-MOF (Scheme \u003cspan refid=\"Sch1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The fabricated S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF ratiometric fluorescent probe exhibits distinct and stable emission bands at 619 nm and 445 nm. When Hg\u003csup\u003e2+\u003c/sup\u003e was added to the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs/Eu-MOF system, the fluorescence intensity at 445 nm progressively decreases due to static quenching, whereas the emission intensity at 619 nm remains constant. This distinct ratiometric response enables the quantitative detection of Hg\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Experimental section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eChemicals reagents\u003c/h2\u003e \u003cp\u003eThe EuCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, citric acid (C\u003csub\u003e9\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e), Benzene-1,3,5-tricarboxylic acid (H\u003csub\u003e3\u003c/sub\u003eBTC), acetic acid sodium salt (CH\u003csub\u003e3\u003c/sub\u003eCOONa), thiourea (CH\u003csub\u003e4\u003c/sub\u003eN\u003csub\u003e2\u003c/sub\u003eS) and ethanol (C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eO) were sourced from Shanghai Aladdin Reagent Co., Ltd. Metal salts (NaCl, CuCl\u003csub\u003e2\u003c/sub\u003e, CoCl\u003csub\u003e2\u003c/sub\u003e, NiCl\u003csub\u003e2\u003c/sub\u003e, FeCl\u003csub\u003e3\u003c/sub\u003e, FeCl\u003csub\u003e2\u003c/sub\u003e, MnCl\u003csub\u003e2\u003c/sub\u003e, MgCl\u003csub\u003e2\u003c/sub\u003e, AgNO\u003csub\u003e3\u003c/sub\u003e, HgCl\u003csub\u003e2\u003c/sub\u003e, Na\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e, KNO\u003csub\u003e3\u003c/sub\u003e, Na\u003csub\u003e3\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e) and Lysine (Lys), Arginine (Arg), Glutamic Acid (Glu), Glycine (Gly) were acquired from Sinopharm Chemical Reagent Co., Ltd. (PR China). All the reagents used in this work were analytically pure and did not undergo further purification. Deionized water (\u0026gt;\u0026thinsp;18 MU) used in this experiment was supplied by an ultrapure water system.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eCharacterization\u003c/h3\u003e\n\u003cp\u003eTransmission electron microscopy (TEM) and high-resolution TEM (HRTEM) imaging was performed on Nippon Electron JEM-F200 (Japan) operating at 200 kV. Powder X-ray diffraction (PXRD) patterns were obtained on D-MAX 2500/PC ༈Rigaku, Japan) with Cu Kα radiation (40 kV, 40 mA). Fourier transform infrared (FT-IR) spectroscopy was conducted on KBr pellets using a Digilab FTS-3000 IR spectrometer. The optical properties of the synthesized S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF were characterized using an Ultraviolet-visible Spectrophotometer (Hitachi, Japan). the chemical valence states of the surface elements of the MnCeX nanozymes were recorded by X-ray photoelectron spectroscopy (XPS) (ThermoFisher, 250Xi, USA).\u003c/p\u003e\n\u003ch3\u003eSample Preparation\u003c/h3\u003e\n\u003cp\u003e \u003cem\u003eEu-MOF synthesis\u003c/em\u003e. The Eu-MOF were obtained by a simple optimized solvothermal way with reference to the published literature.[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] EuCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO (36.6 mg, 0.1 mmol) and CH₃COONa (15 mg) were dissolved in 10 mL of deionized water with stirring to form solution A. Separately, H\u003csub\u003e3\u003c/sub\u003eBTC (21 mg, 0.1 mmol) was added to ethanol (10 mL) under ultrasonication to yield solution B. Solution A was then added dropwise to solution B under continuous stirring. The resulting mixture was vigorously stirred for 1 hour. The white precipitate was collected by centrifugation (8000 rpm, 10 min, room temperature), washed sequentially with CH\u003csub\u003e3\u003c/sub\u003eCH\u003csub\u003e2\u003c/sub\u003eOH and deionized water (6 cycles), and finally dried under ambient conditions to obtain the Eu-MOF product.\u003c/p\u003e \u003cp\u003e \u003cem\u003eSynthesis of S,O-C\u003c/em\u003e \u003csub\u003e \u003cem\u003e3\u003c/em\u003e \u003c/sub\u003e \u003cem\u003eN\u003c/em\u003e \u003csub\u003e \u003cem\u003e4\u003c/em\u003e \u003c/sub\u003e \u003cem\u003eQDs\u003c/em\u003e. S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs were synthesized via a hydrothermal method. Specifically, C\u003csub\u003e9\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e (0.21 g) and CH\u003csub\u003e4\u003c/sub\u003eN\u003csub\u003e2\u003c/sub\u003eS (0.26 g) were dissolved in 20 mL of distilled water under stirring. The combined solution was transferred to a Teflon-lined autoclave with the volume 25 mL and subjected to hydrothermal treatment at 200\u0026deg;C for 2 h. After cooling to ambient temperature, the resulting product was dispersed in 50 mL of distilled water. The resulting aqueous dispersion was then centrifuged at 15,000 rpm for 10 min remove insoluble residues. Subsequently, the supernatant was filtered through a 0.22 \u0026micro;m microporous membrane to afford a brownish-yellow solution. To purify the QDs, this solution was dialyzed against distilled water for 24 h by using a dialysis membrane (molecular weight cut-off: 500 Da) to obtain purified S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs. Finally, the dialyzed solution was freeze-dried to afford the solid S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs.\u003c/p\u003e \u003cp\u003e \u003cem\u003eSynthesis of S,O-C\u003c/em\u003e \u003csub\u003e \u003cem\u003e3\u003c/em\u003e \u003c/sub\u003e \u003cem\u003eN\u003c/em\u003e \u003csub\u003e \u003cem\u003e4\u003c/em\u003e \u003c/sub\u003e \u003cem\u003eQDs/Eu-MOF\u003c/em\u003e. The S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs /Eu-MOF composite was prepared following a procedure analogous to that of the pristine Eu-MOF, with a key modification. Specifically, 5 mg of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs were introduced into Solution A during its preparation. All subsequent steps were identical to those employed for the synthesis of Eu-MOF.\u003c/p\u003e\n\u003ch3\u003eRatiometric Fluorescence Detection of Hg\u003c/h3\u003e\n\u003cp\u003eThe Hg\u0026sup2;⁺ detection procedure using the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs /Eu-MOF ratiometric fluorescence probe was performed as follows. First, 1.0 mL of the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs /Eu-MOF suspension was placed in a 3 mL quartz cuvette. Subsequently, varying volumes of Hg\u003csup\u003e2+\u003c/sup\u003e standard solution (10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e M) were introduced. The total volume was then adjusted to 2.0 mL with Tris-HCl buffer solution. After incubation for 4 min, fluorescence emission spectra were recorded at an excitation wavelength of 370 nm. The detection limit (LOD) for Hg\u003csup\u003e2+\u003c/sup\u003e was calculated according to the equation LOD\u0026thinsp;=\u0026thinsp;3σ/k, where σ represents the standard deviation of 11 consecutive blank measurements, and k denotes the slope of the ratiometric signal (F\u003csub\u003e445\u003c/sub\u003e/F\u003csub\u003e619\u003c/sub\u003e) vs. Hg\u003csup\u003e2+\u003c/sup\u003e concentration calibration curve.\u003c/p\u003e\n\u003ch3\u003eSelectivity anti-interference ability, and stability test\u003c/h3\u003e\n\u003cp\u003eTo evaluate the selectivity of the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF ratiometric probe towards Hg\u003csup\u003e2+\u003c/sup\u003e and its anti-interference capability against potential coexisting species, competitive binding assays were performed. Specifically, the response of the probe was measured in the presence of various analytes: amino acids (Gly, Ala, Glu, Lys), anions (Cl\u003csup\u003e⁻\u003c/sup\u003e, CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2⁻\u003c/sup\u003e, SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2⁻\u003c/sup\u003e, PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3⁻\u003c/sup\u003e, NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e⁻\u003c/sup\u003e), cations (Ag\u003csup\u003e+\u003c/sup\u003e, Mg\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, Co\u003csup\u003e2+\u003c/sup\u003e, Fe\u003csup\u003e3+\u003c/sup\u003e, Fe\u003csup\u003e2+\u003c/sup\u003e). To ensure statistical reliability, triplicate independent measurements were conducted for each condition.\u003c/p\u003e \u003cp\u003eThe stability of the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF ratiometric probe was systematically evaluated under four distinct conditions: (i)Photostability: continuous exposure to 365 nm ultraviolet irradiation for 60 min; (ii) Ionic strength tolerance: dispersion in NaCl solutions with various concentration (100\u0026ndash;1000 mM); (iii) pH stability: dispersion in buffer solutions spanning a pH range (pH 4\u0026ndash;10); (iv) Long-term storage stability: ambient storage at 25\u0026deg;C for 60 days. Fluorescence spectra were periodically recorded to quantify the ratiometric signal intensity (F\u003csub\u003e445\u003c/sub\u003e/F\u003csub\u003e619\u003c/sub\u003e) under each condition.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eReal sample analysis\u003c/h2\u003e \u003cp\u003eActual water samples employed in this study comprised lake water collected from Yingze Park and laboratory tap water. The obtained water was filtered and then heated to boiling for 30 minutes. After cooling to ambient temperature, the solution was filtered through a 0.22 \u0026micro;m microporous membrane and stored at 4\u0026deg;C for subsequent use. Both the blood and urine samples were obtained from healthy adult volunteers. Fresh urine samples were centrifuged (12,000 \u0026times; g) for 20 min. The supernatant was subsequently diluted 1000-fold with 10 mM Tris-HCl buffer (pH 9.0) for short-term storage at 4\u0026deg;C. Add an equal volume of acetonitrile solution to the blood sample and stir evenly. After standing for 3 minutes, centrifuge for 10 minutes. Filter the supernatant with a 0.22 \u0026micro;m microporous filter membrane. Finally, dilute it 100 times with Tris-HCl buffer salt solution (10 mM, pH\u0026thinsp;=\u0026thinsp;9) and store it in a 4\u0026deg;C refrigerator for later use. Standard tetracycline solutions (2.5, 10, 30 \u0026micro;M) were added to treated lake water, tap water, blood and urine samples for further analysis.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results and discussion","content":"\u003cp\u003e\u003cstrong\u003eThe characterization analyses of the synthesis nanomaterials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe structure properties of the prepared materials were studied by TEM, HRTEM and XRD. As shown in Figure 1a, Eu-MOF showed a rod-like morphology and its diameter is approximately 60nm. Following the encapsulation of S,O-co-doped carbon nitride quantum dots (S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs), the Eu-MOF maintained their structural integrity while exhibiting uniformly dispersed nanoparticles anchored on their surfaces (Figure 1b).\u003csup\u003e22\u003c/sup\u003e The HRTEM characterization presented in Figure 1c reveals clear lattice streaks with a lattice spacing of 0.33 nm, corresponding to the characteristic (002) crystal plane of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs. This result clearly confirms the successful encapsulation of S, O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e quantum dots within Eu-MOF.[20]\u003c/p\u003e\n\u003cp\u003eThe XRD pattern was also performed to analyses the crystal structure of Eu-MOF and S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs/Eu-MOF. As displayed in Figure 1d, it shows multiple sharp characteristic diffraction peaks of Eu-MOF and S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF\u0026nbsp;within the range of 5-40\u0026deg;, which were closely matched the corresponding standard simulated peaks of\u0026nbsp;Eu-MOF\u0026nbsp;(CCDC No. 290771 and 147248).[34,35] Comparative XRD analysis of the\u0026nbsp;Eu-MOF and S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF composite demonstrates the diffraction patterns with peak positions (2\u0026theta; = 5.3\u0026deg;, 10.7\u0026deg;, 16.2\u0026deg;) essentially identical to pristine Eu-MOF (\u0026Delta;\u0026theta; \u0026lt; 0.2\u0026deg;)，indicating that the successful encapsulation of S,O-C₃N₄ QDs within the Eu-MOF matrix has while preserving the structural integrity of the MOF framework, as evidenced by TEM imaging (Figure 1b) results.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe FT-IR spectrum was carried out to further study the functional groups of the prepared samples. As presented in Figure 1e, the characteristic peaks appeared around 3410 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e is belonged to the Eu-MOF due to the stretching vibrations of O-H and N-H.\u003csup\u003e36\u003c/sup\u003e In addition, the characteristic peaks were observed at 1373 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e, 1436 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e, 1560 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e, and 1612 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e can be assigned to assigned to the symmetric and anti-symmetric stretching vibration of the carboxyl group, respectively.[34,37] Furthermore, S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs/Eu-MOF exhibited characteristic peaks at 2064 cm cm\u003csup\u003e\u0026minus;\u003c/sup\u003e\u003csup\u003e1\u003c/sup\u003e, which verifies that S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs was successfully incorporated into Eu-MOF.\u003c/p\u003e\n\u003cp\u003eXPS analysis was employed to further investigate the elements changes during the synthesis process of the\u0026nbsp;S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs/Eu-MOF. As shown in Figure 1f, the full survey spectra demonstrated that the elements in Eu-MOF include Eu, O and C, the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs contains only four elements: C, N, S and O.[38-40] With the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs successful encapsulation in Eu-MOF, N and S elements appear in S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs/Eu-MOF, which is in agreement with the FT-IR results.[41]\u003c/p\u003e\n\u003cp\u003eFigure 2a-d showed the XPS high-resolution spectrum of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF. As exhibition in Figure 2a, there was five split peaks appeared at 284.6 eV, 284.9 eV, 285.5 eV, 288.6 eV and 289.0 eV, which were abscribed to the binding enery of C=C, C-C/C-H, C-OH/C-O-C, C=O and COOH.[42] As can be observed in Figure 2b, N 1s showed obvious spectral peaks at 400.7 eV and 401.8 eV, which belonged to N\u0026ndash;H and N\u0026ndash;O binding energy, respectively.[43] In the O 1 s energy spectrum (Figure 2c), the binding energy located at 532.1 eV and 533.2 eV are determined to be C\u0026ndash;O and C=O bond. For the Eu 3d highresolution spectrum (Figure 2d), it can be deconvoluted into four peaks. Among them, the peaks at 1165.1 eV and 1157.6 eV are belong to Eu 3d\u003csub\u003e3/2\u003c/sub\u003e, the characteristic peaks located at 1135.2 eV eV are caused by the binding energy of Eu 3\u003csub\u003ed5/2\u003c/sub\u003e.[44] Additionaly, the peak with the binding energy is 1143.2 eV should be attributed to the satellite signal.[2] These characterization consequences collectively confirmed that the successful syntheis of dual ligands MOFs.\u003c/p\u003e\n\u003cp\u003eEu-MOF fluorescence emission spectra were investigated at different excitation wavelengths. Figure 3a reveals weak fluorescence emission peaks at 595 nm and 690 nm under excitation at different wavelengths, while a strong peak is observed at 619 nm. Notably, the results in Fgiure 3a demonstrate a prominent fluorescence emission peak located at 619 nm. It is worth noting that the fluorescence intensity exhibits excitation wavelength-dependent behavior, showing an initial enhancement followed by gradual attenuation as the excitation wavelength increases. The maximum emission intensity was observed at an optimal excitation wavelength of 265 nm, indicating wavelength-specific activation characteristics of the material. The UV-vis absorption spectra and fluorescence spectra of the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF were shown in Figure 3b. In UV spectra, S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF reveals two distinct electronic transition features: the sharp absorption band centered at 200 nm is assignable to \u0026pi;-\u0026pi; * electronic transitions of C=C bonds, whereas the broader peaks extending to 340 nm originates from n-\u0026pi;* electronic transitions associated with C=O moieties in the nanostructure. [22, 24] As evidenced by the spectral analysis in Figure 3b, under 370 nm excitation, S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF composite probe maintained the characteristic emission of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs at 450 nm while simultaneously exhibiting three distinct emission bands at 595 nm, 619 nm, and 690 nm. These longer wavelength emissions correspond to the typical electronic transitions of Eu\u0026sup3;⁺ ions.[2,15]\u0026nbsp;Apparently, the above analysis results confirmed that\u0026nbsp;S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs was successfully incorporated into Eu-MOF.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOptimum of experimental conditions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn order to obtain optimal conditions for sensing\u0026nbsp;Hg\u003csup\u003e2\u003c/sup\u003e, the experimental parameters such as the concentration of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF and reaction time were systematically investigated. As shown in Figure 4a, the F\u003csub\u003e619\u003c/sub\u003e/F\u003csub\u003e445\u003c/sub\u003e ratio exhibited an inverse linear dependence on Hg\u003csup\u003e2+\u003c/sup\u003e concentration over the range of 0.1\u0026ndash;35 \u0026micro;M. Notably, the slope of the linear correlation between the ratio F\u003csub\u003e619\u003c/sub\u003e/F\u003csub\u003e445\u003c/sub\u003e and Hg\u003csup\u003e2+\u003c/sup\u003e concentration exhibited a distinct concentration-dependent behavior. As the concentration of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF increased from 13 to 17 \u0026mu;g/mL, the slope value initially showed a progressive enhancement, reaching maximum responsiveness at 15 \u0026mu;g/mL, followed by a subsequent decline at higher concentrations. Hence, the concentration of 15 \u0026mu;g/mL was chosen for subsequent experiment. Response time of the fluorescence intensity of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF after the addition of Hg\u003csup\u003e2+\u003c/sup\u003e was exhibited in Figure 4b. It can be found that the fluorescence intensity ratio of F\u003csub\u003e619\u003c/sub\u003e/F\u003csub\u003e445\u003c/sub\u003e achieved stabilization within 4 minutes and maintained this equilibrium state throughout the subsequent 30 minutes monitoring period. Based on these observations, 4 minutes was selected for all subsequent analytical measurements to ensure optimal sensing responsiveness.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFluorescence detection of Hg\u003csup\u003e2+\u003c/sup\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo evaluate the sensitivity enhancement achieved through S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF-based ratiometric fluorescence detection for Hg\u003csup\u003e2+\u003c/sup\u003e, a comparative study was carried out by using single-emission S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs as the reference sensing platform. Figure 5a delineates the concentration-dependent fluorescence quenching behavior of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs upon interaction with Hg\u003csup\u003e2+\u003c/sup\u003e ions within the concentration range of 0-160 \u0026mu;M. As illustrated in Figure 5a, with the increase of Hg\u003csup\u003e2+\u003c/sup\u003e concentration, the fluorescence intensity at 445 nm gradually decreases, which indicated that the emission at 445 nm of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs was quenched by Hg\u003csup\u003e2+\u003c/sup\u003e. The Figure 5b exhibits a linear dependence of 1/(F\u003csub\u003e0\u003c/sub\u003e - F) on concentration of 1/C\u003csub\u003eHg\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e, among them, F\u003csub\u003e0\u003c/sub\u003e and F represent the fluorescence intensity values at 445 nm in the absence and presence of Hg\u003csup\u003e2+\u003c/sup\u003e, respectively, and C\u003csub\u003eHg2+\u003c/sub\u003e is the concentration of Hg\u003csup\u003e2+\u003c/sup\u003e. linear relationship between the reciprocal of fluorescence intensity difference (1/(F\u003csub\u003e0\u003c/sub\u003e-F\u003csub\u003e1\u003c/sub\u003e)) and the inverse of mercury ion concentration (1/C\u003csub\u003eHg2+\u003c/sub\u003e), where F\u003csub\u003e0\u003c/sub\u003e represents the baseline fluorescence intensity at 445 nm in the absence of Hg\u003csup\u003e2+\u003c/sup\u003e, while F\u003csub\u003e1\u003c/sub\u003e denotes the corresponding fluorescence intensity measured in the presence of Hg\u003csup\u003e2+\u003c/sup\u003e. The regression equation is established: 1/(F\u003csub\u003e0\u003c/sub\u003e-F\u003csub\u003e1\u003c/sub\u003e) = 0.0427 C\u003csub\u003eHg2+\u003c/sub\u003e + 0.0014, while the concentration of Hg\u003csup\u003e2+\u003c/sup\u003e under the range of 0.0 ~ 160 \u0026mu;M. The LOD for Hg\u003csup\u003e2+\u003c/sup\u003e was calculated to be 0.172 \u0026mu;M based on the equation of LOD=3\u0026sigma;/K. As shown in Figure 5c, with the increase of Hg\u003csup\u003e2+\u003c/sup\u003e concentration, the fluorescence intensity of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF at 445 nm decreased significantly, whereas the emission intensity at 619 nm exhibited negligible variation across the tested concentration range.\u003c/p\u003e\n\u003cp\u003eFigure 6a displays the dual-wavelength fluorescence response (445/619 nm) of the sensor system to Hg\u003csup\u003e2+\u003c/sup\u003e concentrations, paralleling the spectral evolution patterns demonstrated in Figure 5c. The concentration-dependent response of the F\u003csub\u003e619\u003c/sub\u003e/F\u003csub\u003e445\u003c/sub\u003e ratio to Hg\u003csup\u003e2+\u003c/sup\u003e is presented in Figure 6b. The calibration curve exhibited two distinct linear correlations across different concentration ranges of Hg\u003csup\u003e2+\u003c/sup\u003e, i.e. in the range from 0.25 to 4 \u0026mu;M (R\u003csup\u003e2\u003c/sup\u003e = 0.9935) and from 4 to 35 \u0026mu;M (R\u003csup\u003e2\u003c/sup\u003e = 0.9961). These relationships indicate that there is a strong linear dependence between the fluorescence intensity ratio and the mercury ion concentration, and the correlation coefficients in both concentration domains exceed 0.99. The LOD for Hg\u003csup\u003e2+\u003c/sup\u003e was calculated to be 4.3 nM. The comparative analysis reveals that the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF composite demonstrates significantly superior Hg\u003csup\u003e2+\u003c/sup\u003e sensing performance relative to its individual S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs counterpart.\u003c/p\u003e\n\u003cp\u003eThe detection range and LOD of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF are compared with the previously reported platform and summarized in Table 1. As shown in Table 1, the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF exhibits high sensitivity (LOD of 4.3 nM) within the range of 0.25\u0026ndash;35 \u0026micro;M, which indicate that doping g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e quantum dots with S and O and encapsulating them in Eu-MOF can effectively improve the sensitivity of detecting Hg\u003csup\u003e2+\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 1 Comparison of different probes for Hg\u003csup\u003e2+\u003c/sup\u003e detection based the ratiometric intensity\u003c/p\u003e\n\u003cdiv align=\"center\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003eProbe\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003eLiner range (\u0026mu;M)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13px;\"\u003e\n \u003cp\u003eLOD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003erefs\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003eluminol -Eu-IPA CPNPs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e0.05\u0026ndash;20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13px;\"\u003e\n \u003cp\u003e13.2 nM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e[45]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003eBYCDs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e0.95\u0026ndash;50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13px;\"\u003e\n \u003cp\u003e270 nM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e[46]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003erhodamine B-\u0026nbsp;carbon quantum dots\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e10\u0026ndash;70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13px;\"\u003e\n \u003cp\u003e3.3 nM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e\u0026nbsp;[47]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003eEu-Ca-MOF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e0.02-200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13px;\"\u003e\n \u003cp\u003e2.6 nM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e\u0026nbsp;[48]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003eLaponite-Eu-Cit\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e0.4\u0026ndash;1.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13px;\"\u003e\n \u003cp\u003e30 nM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e\u0026nbsp;[49]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003eS,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e0.25\u0026ndash;35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13px;\"\u003e\n \u003cp\u003e4.3 nM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003eThis work\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSelectivity, anti-interference ability, and stability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn order to understand the selectivity and the anti-interference ability of the\u0026nbsp;S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF system for detecting Hg\u003csup\u003e2+\u003c/sup\u003e, some common interferents such as metal ions (Na\u003csup\u003e+\u003c/sup\u003e, Ag\u003csup\u003e+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e, Mg\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e2+\u003c/sup\u003e, Fe\u003csup\u003e2+\u003c/sup\u003e, Co\u003csup\u003e2+\u003c/sup\u003e, and Fe\u003csup\u003e3+\u003c/sup\u003e), anions (Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e, NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e, SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e, and CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e), and some amino acids (Lys, Arg, Glu, Gly, and Ala) are tested in this work. Figure 7 shows the intensity ratio of F\u003csub\u003e445\u003c/sub\u003e/F\u003csub\u003e619\u003c/sub\u003e for Hg\u003csup\u003e2+\u003c/sup\u003e and other interferents, respectively. It is noteworthy that Hg\u003csup\u003e2+\u003c/sup\u003e causes significant changes for F\u003csub\u003e445\u003c/sub\u003e/F\u003csub\u003e619\u003c/sub\u003e, wheras other interferents exhibit negligible changes. Eventually, the anti-interference ability of the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF after mixing Hg\u003csup\u003e2+\u003c/sup\u003e with various coexisting intererents was further evaluated. The analytical findings demonstrate that these interferents exert negligible interference on Hg\u003csup\u003e2+\u003c/sup\u003e detection sensitivity. The exceptional selectivity of this sensing platform originates from the specific interaction between S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF and Hg\u003csup\u003e2+\u003c/sup\u003e makes this platform have high practical applications for detection Hg\u003csup\u003e2+\u003c/sup\u003e in real samples.\u003c/p\u003e\n\u003cp\u003eThe fluorescence stability of the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF were further studied under four distinct environmental conditions to evaluate its practical applicability: (a) continuous exposure to 365 nm ultraviolet irradiation for 60 minutes to assess photostability, (b) immersion in aqueous NaCl solutions with varying ionic strengths (0.1-1.0 M) to examine electrolyte tolerance, (c) dispersion in buffer solutions within a pH range of 3.0-11.0 to evaluate acid-base stability, and (d) long-term ambient storage (25\u0026deg;C, 60 days) to monitor time stability. As shown in Figure 8, S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF shows good fluorescence stability under UV irradiation, wide pH ranges, high salt conditions, and long time. Hence, its good fluorescence stability makes the use of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF in practical applications.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMechanisms of detecting Hg\u003csup\u003e2+\u003c/sup\u003e by S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe sensing mechanism of fluorescence response of the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF is further investigated toward Hg\u003csup\u003e2+\u003c/sup\u003e. Figure 9a depicts the temperature dependence (300-320 K) of the Stern-Volmer plot for S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs- Hg\u003csup\u003e2+\u003c/sup\u003e system. The slope revealing an inverse relationship between temperature and the quenching constant, which indicated diminished collisional quenching efficiency at higher thermal energy levels. Comprehensive surface analysis via FTIR and XPS spectra (Figure 1e and Figure 1f), reveals that there were large numbers of carbonyl, hydroxyl and carboxylic groups on S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs surfaces, suggesting the possible electrostatic interactions between S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs and Hg\u003csup\u003e2+\u003c/sup\u003e. Hg\u003csup\u003e2+\u003c/sup\u003e exhibits strong binding affinity toward surface functional groups (e.g., carboxyl groups), forming non-fluorescent complexes via chelation that induce fluorescence quenching. As demonstrated in the Figure 9b, UV-Vis absorption spectra of S,O-CNQDs show concentration-dependent attenuation (0.0\u0026ndash;35 \u0026mu;M Hg\u003csup\u003e2+\u003c/sup\u003e), suggesting complex formation between Hg\u0026sup2;⁺ and quantum dots. In order to further investigate the interaction mechanism between S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs and Hg\u003csup\u003e2+\u003c/sup\u003e, the fluorescence lifetimes of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs with different concentrations of Hg\u003csup\u003e2+\u003c/sup\u003e were shown in the Figure 9c. The average lifetime of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs were basically unchanged with the increasing of the concentration of Hg\u003csup\u003e2+\u003c/sup\u003e. This result confirm that static quenching was considered the mechanism for the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs probe.[50,51]\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDetermination of Hg\u003csup\u003e2+\u003c/sup\u003e in real sample\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe practical application of the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF system is evaluated by a recovery test of Hg\u003csup\u003e2+\u003c/sup\u003e spiked blood, urine, lake water and tap water samples, the consequences are listed in Table 2. Table 2 demonstrates that good recoveries (96 ~ 108%) and satisfactory RSDs (6 ~ 32%) are obtained from this detection model. This result indicated that S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF has better accuracy and higher reliability, which can be used for the determination of Hg\u003csup\u003e2+\u003c/sup\u003e in actual samples.\u003c/p\u003e\n\u003cp\u003eTable 2 Determination of Hg\u003csup\u003e2+\u003c/sup\u003e with S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF in real samples\u003c/p\u003e\n\u003cdiv align=\"center\"\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 20px;\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 37px;\"\u003e\n \u003cp\u003eConcentration of Hg\u003csup\u003e2+\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 20px;\"\u003e\n \u003cp\u003eRecovery (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 20px;\"\u003e\n \u003cp\u003eRSD (%,n=3)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003eAdded (\u0026mu;M)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18px;\"\u003e\n \u003cp\u003eFound (\u0026mu;M)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" style=\"width: 20px;\"\u003e\n \u003cp\u003eBlood sample\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18px;\"\u003e\n \u003cp\u003e2.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e108\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e0.13\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18px;\"\u003e\n \u003cp\u003e5.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e102\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18px;\"\u003e\n \u003cp\u003e19.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" style=\"width: 20px;\"\u003e\n \u003cp\u003eUrine sample\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18px;\"\u003e\n \u003cp\u003e1.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18px;\"\u003e\n \u003cp\u003e5.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e101\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e0.10\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18px;\"\u003e\n \u003cp\u003e20.36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e101\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" style=\"width: 20px;\"\u003e\n \u003cp\u003eLake water\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18px;\"\u003e\n \u003cp\u003e2.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e102\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18px;\"\u003e\n \u003cp\u003e4.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e0.24\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18px;\"\u003e\n \u003cp\u003e20.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e102\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" style=\"width: 20px;\"\u003e\n \u003cp\u003eTap water\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18px;\"\u003e\n \u003cp\u003e2.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e105\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18px;\"\u003e\n \u003cp\u003e4.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e0.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18px;\"\u003e\n \u003cp\u003e19.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, a novel probe (S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF) was successfully synthesized to detect Hg\u003csup\u003e2+\u003c/sup\u003e. The synthesized probe exhibited dual-emission at wavelengths of 445 nm and 619 nm, respectively. As the Hg\u003csup\u003e2+\u003c/sup\u003e concentration increases, the emission at 445 nm of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF decreases gradually, whereas that of u-MOF at 619 nm remains constant. The fluorescence of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF at 445 nm was quenched by Hg\u003csup\u003e2+\u003c/sup\u003e due to static quenching. According to the intensity ratio (I\u003csub\u003e445\u003c/sub\u003e/ I\u003csub\u003e619\u003c/sub\u003e), a feasible detection method was established for Hg\u003csup\u003e2+\u003c/sup\u003e detection, the linear range of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF\u0026thinsp;+\u0026thinsp;Hg\u003csup\u003e2+\u003c/sup\u003e was 0.25\u0026ndash;35 \u0026micro;M with a LOD 4.3 nM. Moreover, the S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF was successfully applied for the detection of Hg\u003csup\u003e2+\u003c/sup\u003e in real samples such as blood, urine, lake water and tap water samples with the recoveries of 96\u0026thinsp;~\u0026thinsp;108% and the satisfactory RSDs (6\u0026thinsp;~\u0026thinsp;32%). Overall, the prepared nanoprobes have high sensitivity, excellent selectivity and anti-interference ability for Hg\u003csup\u003e2+\u003c/sup\u003e. These satisfying results in this work demonstrates an effective fluorescence sensor for Hg\u003csup\u003e2+\u003c/sup\u003e detection and highlight the potential of S,O- C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs /Eu-MOF composites in environmental monitoring applications.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eConflicts of interest\u003c/h2\u003e \u003cp\u003eThere are no conflicts of interest to declare.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eJie Yao: writing, review and editing, formal analysis. Hongfang Chen: writing, original draft, investigation, data curation. Xiaohua Yang: data curation. Muzaffar Iqbal: writing, review and editing, Wei Bian: writing, review and editing, funding acquisition.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThis work was supported by Natural Science Foundation of Shanxi Province of China (202403021212220, 202203021221186, 201901D111210), the Shanxi Province Higher Education \"Billion Project\" Science and Technology Guidance Project (BYJL025) and the Central Government Guides Local Funds for Science and Technology Development (YDZJSX2024C028), Ongoing Research Funding Program(ORF-2025-734), King Saud University, Riyadh, Saudi Arabia.\u003c/p\u003e\u003ch2\u003eData availability\u003c/h2\u003e \u003cp\u003eThe raw/processed data required to reproduce these findings cannot beshared at this time as the data also forms part of an ongoing study.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eJ. Wang, M. Shen, F. Meng, X. Han, M. 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Wang (2023) Sulfur quantum dot as a fluorescent nanoprobe for Fe\u003csup\u003e3+\u003c/sup\u003e ions: Uncovering of detection mechanism, high sensitivity, and large detection range. 257: 119693.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Scheme","content":"\u003cp\u003eScheme 1 is 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":"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":"Doped, Eu-MOF, fluorescence sensor, Quantum dots, Ratiometric fluorescence","lastPublishedDoi":"10.21203/rs.3.rs-6942147/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6942147/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eMercury ions (Hg\u003csup\u003e2+\u003c/sup\u003e) are categorized as environmental pollutants, which distributed in water, soil, and food systems due to environmental contamination. Hence, designing a sensitive assay for the convenient determination of Hg\u003csup\u003e2+\u003c/sup\u003e is of great importance. Herein, S and O-doped graphite phase nitrogenized carbon quantum dots (S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs) was encapsulated within a europium -based metal-organic framework (Eu-MOF) to construct a novel ratiometric fluorescent nanoprobe for the quantitative detection of Hg\u003csup\u003e2+\u003c/sup\u003e. The native emission of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs at 445 nm is used as a response signal, while Eu-MOF with fluorescence offers a reference signal at 619 nm. Hg\u003csup\u003e2+\u003c/sup\u003e exhibits high affinity for the surface functional groups of S/O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e QDs, forming non-fluorescent chelation complexes that induce static quenching. This results in significant attenuation of the fluorescence intensity at 445 nm, while the emission at 619 nm remains invariant. A ratiometric fluorescence sensing platform was established based on the intensity ratio (F\u003csub\u003e445\u003c/sub\u003e/F\u003csub\u003e619\u003c/sub\u003e) for the selective detection of Hg\u003csup\u003e2+\u003c/sup\u003e. The linear range of S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF of Hg\u003csup\u003e2+\u003c/sup\u003e was 0.25\u0026ndash;35 \u0026micro;M and with a detection limit of 4.3 nM. The satisfying results demonstrate the effectiveness of the developed S,O-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eQDs/Eu-MOF-based fluorescence probe for Hg\u003csup\u003e2+\u003c/sup\u003e detection, highlighting its promising potential for environmental monitoring applications.\u003c/p\u003e","manuscriptTitle":"Construction of S,O-Doped g-C3N4 Encapsulated in Eu-MOF with Dual-Emission for Ratiometric Fluorescence Detection of Hg²⁺","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-01 06:00:52","doi":"10.21203/rs.3.rs-6942147/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-09T13:03:43+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-09T08:17:15+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-04T10:54:04+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-03T07:52:25+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"254610626723378494444427410981420584309","date":"2025-07-01T04:50:21+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"13408866694703466162686156874344498648","date":"2025-06-29T02:46:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"35612691144820715966510538204776676182","date":"2025-06-26T11:17:18+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-26T11:02:34+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-24T17:46:08+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-24T17:45:30+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Fluorescence","date":"2025-06-21T02:17:19+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":"0946b908-34ce-421d-992d-68dbfb9776da","owner":[],"postedDate":"July 1st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-09-01T16:04:15+00:00","versionOfRecord":{"articleIdentity":"rs-6942147","link":"https://doi.org/10.1007/s10895-025-04535-0","journal":{"identity":"journal-of-fluorescence","isVorOnly":false,"title":"Journal of Fluorescence"},"publishedOn":"2025-08-25 15:57:19","publishedOnDateReadable":"August 25th, 2025"},"versionCreatedAt":"2025-07-01 06:00:52","video":"","vorDoi":"10.1007/s10895-025-04535-0","vorDoiUrl":"https://doi.org/10.1007/s10895-025-04535-0","workflowStages":[]},"version":"v1","identity":"rs-6942147","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6942147","identity":"rs-6942147","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}