A smartphone-assisted fluorescent sensor using Eu -MOF nanorods for visual and sensitive detection of Organophosphorus pesticides

A smartphone-assisted fluorescent sensor using Eu -MOF nanorods for visual and sensitive detection of Organophosphorus pesticides | 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 A smartphone-assisted fluorescent sensor using Eu -MOF nanorods for visual and sensitive detection of Organophosphorus pesticides Shiyi Wang, Kunyang Feng, Minzhu Zhao, Yusen Wang, Xin He, Qi Wang, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9273730/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 13 You are reading this latest preprint version Abstract Organophosphorus pesticides (OPs) are extensively used for pest control in crops, yet their residues pose potential threats to food safety and human health. Therefore, this study developed a dual-ligand metal-organic framework with stable red fluorescence as a ratiometric fluorescent sensor for highly sensitive detection of omethoate (OMT). The sensor utilizes Eu³⁺ as the metal node and employs 3,5-dicarboxyphenylboronic acid (BBDC) and 2-hydroxyterephthalic acid (BDC-OH) as mixed organic ligands. The introduction of OMT significantly quenches the red fluorescence of Eu-BBDC/BDC-OH through the inner filter effect (IFE), enabling the quantitative analysis of OMT. The sensor exhibits a good linear response within the ranges of 0.025–0.3 µg/mL and 0.3–0.9 µg/mL, with a detection limit of 7.35 ng/mL, and demonstrates excellent selectivity. Recoveries of OMT from strawberry and cucumber samples ranged from 95.74% to 101.1%, with relative standard deviations of 0.59%–5.91%, validating the reliability and practicality of the method. Moreover, a paper-based sensor integrated with smartphone RGB analysis was constructed, allowing rapid, real-time, and visual detection of OMT residues. Metal-organic frameworks Organophosphorus pesticides Fluorescent sensor Smartphone sensing Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Organophosphorus pesticides (OPs) are compounds containing phosphate or thiophosphate ester structures. Due to their high efficacy and broad-spectrum insecticidal activity, OPs have been extensively used in global agricultural production to control pests and diseases, playing a crucial role in safeguarding crop yields (Xu et al. 2024 ). However, most OPs are resistant to natural degradation and can enter the food chain through bioaccumulation, leading to widespread residues in agricultural products, water sources, and processed foods (Jiang et al. 2023 ). Long-term low-dose exposure to OPs residues can cause chronic damage to various human systems, including but not limited to the nervous and endocrine systems, whereas high-dose exposure may even lead to acute poisoning and life-threatening conditions (Yao et al. 2020 ). Therefore, monitoring and controlling OPs residues in food and environmental media have become important public safety issues. Omethoate (O, O-dimethyl-S-methylcarbamoylmethyl thiophosphate, OMT) is a typical systemic organophosphorus insecticide and acaricide, widely applied in the protection of crops such as cotton, wheat, and corn against pests, making it one of the commonly used OPs in agricultural production (Ding et al. 2021 ). Establishing rapid, sensitive, and reliable analytical methods for OMT is a prerequisite for implementing effective residue monitoring and ensuring food safety. To date, Traditional analytical techniques for OPs residues mainly include gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography (HPLC), and enzyme-linked immunosorbent assay (ELISA) (Umapathi et al. 2022 ). Although these methods provide high sensitivity and accuracy, they are hindered by limitations including costly instrumentation, complex operational procedures, labor-intensive sample pretreatment, and prolonged detection cycles, rendering them inadequate for on-site rapid testing demands. Therefore, the development of simple and rapid on-site detection techniques is of significant importance. Metal-Organic Frameworks (MOFs) are a class of crystalline porous materials formed by the self-assembly of metal ions or metal clusters with organic ligands via coordination bonds (Carpenter et al. 2023 ). Owing to their tunable pore structures, good chemical stability, and excellent optical properties, MOFs are regarded as an ideal platform for constructing fluorescent sensors (Zhang et al. 2021 ). In recent years, MOF-based sensing materials have demonstrated significant potential in the field of pesticide detection (Huang et al. 2024 ). The high specific surface area and adjustable pore size of MOFs enable efficient adsorption and enrichment of target pesticide molecules, thereby significantly improving detection sensitivity (Wagner et al. 2021 ; Wu et al. 2021 ). Moreover, by rationally selecting metal centers and organic ligands, high selective recognition of specific pesticide molecules can be achieved, further enhancing detection accuracy (Xu et al.). Among various MOFs materials, lanthanide-based metal-organic frameworks (Ln-MOFs) exhibit unique photoluminescence properties due to ligand-to-metal charge transfer, making them particularly suitable for optical sensing (Xie et al. 2023 ; Mohammed Ameen et al. 2025; Qi et al. 2026 ). Furthermore, with the development of smartphone-based portable sensing platforms, the built-in camera and RGB color analysis can convert fluorescence signals into digital output. This allows real-time, on-site detection without the need for sophisticated instruments by monitoring changes in the red-to-blue emission intensity ratio induced by analytes (Liu et al. 2026 ). This study synthesized a dual-ligand Ln-MOFs (Eu-BBDC/BDC-OH) nanorods and constructed a novel smartphone-assisted ratiometric fluorescence sensing platform for the specific, highly sensitive, and visual detection of OMT (Scheme 1). Based on the inherent dual-emission characteristics of Eu-BBDC/BDC-OH, this sensor enables the quantitative analysis of OMT by monitoring the consistent changes in the intensity ratio (F 614 /F 430 ) of characteristic fluorescence peaks before and after the addition of OMT. Experimental results indicate that the sensing platform exhibits excellent detection sensitivity and high selectivity toward OMT. To further validate its potential for practical applications, the sensor was successfully employed for the detection of OMT residues in strawberries and cucumbers, demonstrating reliable recovery rates and precision. This work shows promising potential for the development of portable, on-site rapid detection devices targeting OPs. Scheme 1. Schematic illustration for fluorescence sensing of OMT by Eu-MOF. 2. Material and methods 2.1. Reagents and instruments Eu (Cl) 3 ·6H 2 O (99.9%), 3,5-Dicarboxyphenylboronic acid (BBDC,≥98%), 2-Hydroxyterephthalic acid (BDC-OH, ≥ 98%), glucose (Glc), glutathione (GSH), arginine (Arg), glycine (Gly), L-cysteine (Cys), valine(Val), and were provided by Aladdin (Shanghai, China).Omethoate (OMT, 98.6%), dimethoate (DMT), malathion (MAL), methomyl (MET), isocarbophos (ISO), iprobenfos (IBP) were purchased from TMRM Quality Inspection Technology Co., Ltd. (Changzhou, China), all belong to chromatographic purity. CaCl 2 , CoCl 2 , KCl, NH 4 Cl, ZnSO4, MnSO4, N, N-dimethylformamide (DMF), and anhydrous ethanol were provided by Macklin (Shanghai, China). All unmarked purities belong to the analytical or commercial grade. Scanning electron microscopy (SEM) images were acquired using a Hitachi SU8020 microscope (Japan). Transmission electron microscopy (TEM) images were obtained with a Tecnai G2 12 TEM instrument (FEI). X-ray diffraction (XRD) patterns were recorded on a Bruker D8 Advance diffractometer. Thermogravimetric analysis (TGA) was performed on a Mettler TG-DSC 3 + analyzer. UV–vis absorption spectra were measured with a Shimadzu UV-2600 spectrophotometer. Fluorescence (FL) spectra were collected on an Edinburgh FS5 spectrofluorometer. Zeta potential analysis was carried out using a Malvern Zetasizer Nano ZS90. Fourier transform infrared (FT–IR) spectra were acquired with a Thermo iS50 spectrometer. X-ray photoelectron spectroscopy (XPS) data were obtained using a Thermo ESCALAB Xi+ spectrometer. Fluorescence lifetime decays were measured with an Edinburgh FLS980 spectrometer. 2.2. Synthesis of Eu-MOF The Eu-BBDC/BDC-OH was prepared using a modified solvothermal technique based on the literature (He et al. 2025 ). In brief, 0.1 mmol of Eu (Cl) 3 ·6H 2 O in 3 mL of ultrapure water and a sonicated mixture of 0.1 mmol BBDC and 0.005 mmol BDC-OH in 7 mL of DMF were combined. The resulting solution was stirred for 40 minutes, transferred to a 20 mL Teflon-lined autoclave, and reacted at 150°C for 12 h in a muffle furnace. After naturally cooling to room temperature, the precipitate was collected via centrifugation (10000 rpm, 5 min), followed by repeated washing with DMF and ethanol to remove residual reactants. The final product was dried under vacuum at 60 ◦ C to obtain Eu-BBDC/BDC-OH powder. 2.3. Ratiometric fluorescent detection of OMT The Eu-BBDC/BDC-OH powder was dispersed in ultrapure water and ultrasonicated for 20 min to obtain a stable probe suspension (80 µg/ mL). Subsequently, varying amounts of OMT (0–1.0 µg/mL) were introduced into the above solution. The fluorescence emission spectra and corresponding visual color changes were recorded under an excitation wavelength of 250 nm. To assess the specificity of the Eu-BBDC/BDC-OH probe toward OMT, we evaluated its response to a series of potential interferents, including structural analogs of OMT (dimethoate, malathion, methomyl, isocarbophos, and iprobenfos), representative amino acids (GSH, arginine, glycine, L-cysteine, and valine), and prevalent inorganic ions (Ca 2+ , K + , NH 4+ , Zn 2+ , Mn 2+ , and Co 2+ ). These comparative tests were conducted under identical experimental conditions. 2.4. Detection of OMT by smartphone–assisted test strip To prepare the fluorescent test strips, filter paper pieces (1.0 × 1.0 cm 2 ) were soaked in probe solution (80 µg/mL) for 48 h, followed by drying under ambient conditions (Chi et al. 2023 ). The resulting strips were then exposed to varying concentrations of OMT (0–1.0 µg/mL), and fluorescence color variations were recorded using a smartphone under 254 nm illumination in a dark box. Image analysis was conducted by extracting RGB values from the captured images using the smartphone’s built–in software. Finally, a linear calibration curve was constructed by correlating the R/B (red–to–blue) ratio with OMT concentration. 2.5. Detection of OMT in real samples Cucumber and strawberry were selected as representative food matrices to evaluate the applicability of the fluorescent probe. Both sample types were purchased from a local supermarket in Chongqing. To maintain the spiked concentrations of OMT in the food sample matrix at 0.2, 0.4 and 0.8 µg/mL, 5g of homogenized cucumber and strawberry samples were added to a known variable OMT standard solution (20 µL), and the spiked samples were then vortexed with 15 mL of dichloromethane for 2 min. After removing insoluble material, the mixed solution was heated to 50°C for 10 min to remove the dichloromethane. The residue was then redissolved using 2 mL of DMF. Real samples were detected using the same method as previously described, recording each fluorescence assay at least three times. 3. Results and discussion 3.1. Characterizations and optical performances Using SEM and TEM, the morphology and microstructure of Eu-BBDC/BDC-OH nanorods were studied. The SEM analysis revealed that the Eu-BBDC/BDC-OH composite exhibits a well-defined rod-like morphology (Fig. 1A–B). Furthermore, the TEM imaging further confirmed the presence of rod-shaped nanocrystals, with a length of approximately 200 nm (Fig. 1C). The elemental composition and distribution within the Eu-BBDC/BDC-OH were evaluated using a high–resolution TEM (Fig. 1D). The elemental distribution map showed that europium (Eu), carbon (C), oxygen (O), and boron (B) were uniformly distributed within the framework. Energy-dispersive X-ray spectroscopy (EDS) verified the successful incorporation of Eu, further confirming the successful preparation of the nanorods (Fig. S1 ). The crystalline phases of the nanorods were demonstrated by the XRD measurement (Fig. S2). The diffraction peaks of Eu-BBDC/BDC-OH match well with the simulated pattern, indicating high crystallinity and the absence of impurity phases. Additionally, the thermal stability of Eu-BBDC/BDC-OH was obtained by TGA analyzer (Fig. S3). We can observe that the weight loss process of Eu-BBDC/BDC-OH is divided into two stages. The first weight loss occurred between 30 and 550 ◦ C with a mass loss of 0.6692 mg (21.59%), which could be attributed to the loss of free water leading to the loss of mass. In the second stage, between 550 and 600 ◦ C, with a mass loss of 0.2297 mg (7.41%), the skeleton of Eu-BBDC/BDC-OH starts to collapse and rapidly loses weight, with a mass residual of 71%. The aforementioned findings showed that the Eu-BBDC/BDC-OH has good thermal stability (He et al. 2025 ). Figure 1. (A) SEM pictures for Eu-BBDC/BDC-OH nanorods. (B-C) TEM picture for Eu-BBDC/BDC-OH nanorods. (D) HAADF-STEM and corresponding elemental mapping images of Eu-BBDC/BDC-OH nanorods. The XPS analysis was performed to get more information about Eu-BBDC/BDC-OH nanorods. The survey XPS spectra (Fig. 2 A) show the existence of C, O, and Eu. The high-resolution Eu 3d spectra (Fig. 2 B) was fitted to Eu 3+ 3d 3/2 (1165.2 eV) and Eu 3+ 3d 5/2 (1135.3 eV) (Gan et al. 2021 ). The high-resolution C 1s spectrum (Fig. 2 C) displayed two peaks at 289.1 and 284.9 eV, which were attributed to C-O and C-C/C = C bonds, respectively (Fonseca et al. 2019 ). The O 1s spectrum (Fig. 2 D) show two peaks at 531.6 and 532.0 eV, attributed to the Eu-O (metal oxygen single bond) and O = C-O groups, respectively (Han et al. 2022 ). The successful fabrication of Eu-BBDC/BDC-OH nanorods could be proven by the above results. Fourier transform infrared (FT-IR) spectra of BDC-OH, BBDC and Eu-BBDC/BDC-OH were recorded respectively (Fig. 3A). After Eu-MOF formation, the broad hydroxyl characteristic bands of BDC-OH and BBDC in the 2500–3500 cm − 1 region were significantly attenuated, which was ascribed to the partial or full deprotonation of these ligands during synthesis (Liu et al. 2023 ). The successful coordination of Eu³⁺ ions with the carboxylate groups is confirmed by the disappearance of the C = O stretching vibration at ~ 1700 cm⁻¹ and the concurrent emergence of the symmetric and antisymmetric stretching vibrations of the -COO⁻ groups at 1350–1450 and 1550–1610 cm⁻¹, respectively (Zheng et al. 2023 ). The peak at 775 cm − 1 was associated with the Eu-O stretching vibration, indicating that the Eu atoms interact with the -COO group (Yue et al. 2023 ). Given the agreement between the FT-IR and XPS data, it can be inferred that the generated Eu-BBDC/BDC-OH contains a great amount of carboxyl and hydroxyl functional groups improves the stability of material and hydrophilicity. The FL and UV-vis spectra of Eu-BBDC/BDC-OH nanorods were applied to analyze their optical properties in detail. As shown in Fig. 3B, the Eu-BBDC/BDC-OH nanorods exhibit characteristic emission peaks at approximately 430 and 614 nm, which are attributed to the ligand itself and the ⁵D₀→⁷FJ (J = 1,2,3,4) transitions of Eu³⁺, respectively (Yang et al. 2017 ). The overall fluorescence of Eu-BBDC/BDC-OH nanorods exhibits bright red color under 365 nm UV irradiation. The fluorescence values at 430 and 614 nm are highest under 250 nm excitation wavelength (Fig. 3C). Thus, the subsequent experiments were carried out to select 250 nm as the best excitation wavelength. OMT has a strong ability to reduce the fluorescence of Eu/Tb-MOF (Fig. 3D). Additionally, the surface of Eu-BBDC/BDC-OH is positively charged, while OMT is negatively charged. The potential of Eu-BBDC/BDC-OH significantly decreased upon the addition of OMT, indicating the electrostatic attraction between MOF and OMT (Fig. S4). According to these findings, the Eu-BBDC/BDC-OH nanorods have the ability to serve as a fluorescent sensor for monitoring OMT. Figure 3. (A) FT-IR spectra of BDC-OH, BBDC, and Eu-BBDC/BDC-OH. (B) UV–vis absorption and FL spectra of Eu-BBDC/BDC-OH nanorods. Insert: digital picture of Tb-MOF excited at 254 nm UV lamp. (C) FL emission spectra of Eu-BBDC/BDC-OH nanorods under the excitation from 245 to 290nm. (D) FL emission spectra of Eu-BBDC/BDC-OH nanorods in the presence and absence of OMT. 3.2. Fluorescence assay of OMT Using a 250 nm excitation, a range of OMT concentrations (0–1µg/mL) were evaluated in order to study the sensitivity of Eu-BBDC/BDC-OH for OMT sensing. The optimal detection conditions were finally determined as follows to be an Eu–MOF concentration of 80 µg/mL, reaction pH of 7.0, immediate fluorescence measurement, and operation at room temperature (Fig. S5). Under optimal conditions, a quick, sensitive and dependable analytical method for detecting OMT has been established using fluorescent Eu-BBDC/BDC-OH nanorods. Firstly, the sensing performance of Eu-BBDC/BDC-OH for OMT was validated. As the OMT concentration increased, the FL emission of Eu-BBDC/BDC-OH at 614 nm decreased significantly, while the emission at 430 nm descended slowly (Fig. 4 A). As shown in Fig. 4 B, with an increase in the OMT concentration, we can clearly observe that the fluorescence values at F 430 and F 614 dropped, and the red fluorescence became weaker. Therefore, we constructed a fluorescence sensor to realize the quantitative detection of OMT. Two regression equations were developed between the OMT concentration (0-0.3and 0.3-1.0 µg/mL) and F 614 /F 430 . The regression equation can be written as ln F 614 /F 430 = 2.774X + 0.2232 (R 2 = 0.9968) ranging from 0.025 to 0.3 µg/mL, and ln F 614 /F 430 = 5.991X − 0.6593 (R 2 = 0.9940) ranging from 0.3 to 0.9 µg/mL (Fig. 4 C–E). Furthermore, the formula LOD = 3σ/k was utilized to determine the detection limit (LOD), which came out to be 7.35 ng/mL. Compared with previously reported methods (Table S1 ), the proposed radiometric fluorescent probe offers not only superior sensitivity but also a more straightforward and efficient detection procedure, highlighting its strong potential for practical pesticide residue monitoring in food safety applications. To assess the specificity and anti–interference capability of the Eu-BBDC/BDC-OH sensor, fluorescence responses were evaluated against a panel of structurally and chemically diverse interferents, including structural analogs of OMT, amino acids, and metal ions. As depicted in Fig. 3F, the introduction of OMT alone induced a pronounced fluorescence quenching of approximately 59% in the Eu-BBDC/BDC-OH system. In contrast, the presence of other potential interferents led to only negligible variations in fluorescence intensity, underscoring the exceptional of the system selectivity for OMT. To further challenge the selectivity, we investigated mixed systems containing OMT alongside a significant excess of these interferents (Fig. S6). The observed quenching efficiency remained consistent with that of the system containing only OMT, confirming the robust anti-interference capability and signal stability. Collectively, these findings affirm that the Eu-BBDC/BDC-OH probe possesses not only favorable chemical stability but also excellent selectivity for OMT detection. 3.4. Smartphone–integrated paper–based sensing platform For the visual detection of target analytes, this study developed a paper-based porous fluorescent sensor. The test paper was prepared by immersing filter paper in a uniformly dispersed suspension of Eu-MOF, followed by drying at room temperature. The MOF-coated strips were then exposed to OMT solutions at varying concentrations (0–1µg/mL). Under excitation by 254 nm ultraviolet light, the strips exhibited a concentration-dependent fluorescence color change, transitioning gradually from red to purple as the OMT concentration increased. The fluorescence response was captured using a smartphone camera (Fig. 5 A and B). Image analysis based on RGB values revealed a strong linear correlation between the red-to-blue (R/B) intensity ratio and the concentration of OMT (y = -1.72929X + 2.42882, R 2 = 0.9806) (Fig. 5 C). 3.5. Detection of OMT in real samples To validate the practical application of the probe, the Eu-BBDC/BDC-OH was applied to detect strawberry and cucumber samples containing OMT. As summarized in Table 1 , the recovery efficiencies were between 95.74% and 101.1%, with RSD of less than 5.91%. The good performances demonstrated that the Eu-BBDC/BDC-OH probe can be utilized to determine OMT in actual samples with excellent precision and accuracy. Table 1 Results for OMT assay in strawberry and cucumber (n = 3). Samples Added (µg/mL) Found (µg/mL) Recovery (%) RSD (n = 3,%) Strawberry 0 No detected / / 0.2 0.1955 97.76 5.91 0.4 0.3959 98.96 2.57 0.8 0.785 98.05 2.62 Cucumber 0 No detected / / 0.2 0.1916 95.74 2.98 0.4 0.4045 101.1 1.13 0.8 0.8003 100 0.59 3.6. Possible fluorescence quenching mechanism Fluorescence quenching occurs principally via static quenching, dynamic quenching, the internal filtration effect (IFE), and fluorescence resonance energy transfer (FRET) (Li and Zhang 2021 ). As illustrated in Fig. 6 A, OMT exhibits a strong and continuous absorption band in the range of 200–600 nm, which significantly overlaps with the characteristic excitation and emission wavelengths of Eu-MOF. This indicates that OMT effectively absorbs the excitation and emission energy of Eu-MOF, resulting in fluorescence quenching. Consequently, IFE and FRET were considered as potential quenching mechanisms (Tan et al. 2020 ). The UV-vis absorption spectra of Eu-MOF after the addition of OMT show no new absorption peaks and almost completely coincide with the superimposed spectra (Fig. 6 B). Furthermore, the FT-IR spectra confirm that no new chemical bonds are formed upon the introduction of OMT (Fig. 6 C). Thus, the formation of a ground-state complex between Eu-MOF and OMT can be ruled out, excluding static quenching as a possible mechanism. The addition of OMT caused only a minor change in the fluorescence lifetime of Eu-MOF, from 422.31 µs to 407.23 µs, as derived from the decay profiles in Fig. 6 D. The nearly identical lifetime values suggest that FRET is not the dominant quenching mechanism. In conclusion, IFE is identified as the dominant mechanism accounting for the fluorescence quenching of Eu-MOF induced by OMT (Luo et al. 2025 ). 4. Conclusions In conclusion, this study successfully constructed a dual-ligand Ln-MOFs (Eu-BBDC/BDC-OH) nanorods, via a one-pot solvothermal method. The material exhibits a well-defined crystal structure, uniform morphology and elemental distribution, along with distinct fluorescent properties. Based on the IFE, the characteristic red fluorescence of the material at 614 nm can be selectively quenched by OMT, enabling ratiometric fluorescent sensing of the pesticide. Sensing analysis demonstrated good linear responses within two concentration ranges of 0.025–0.3 µg/mL and 0.3–0.9 µg/mL, with a low detection limit of 7.35 ng/mL. Furthermore, a smartphone-based fluorescent detection platform was developed, allowing rapid, visual, and real-time monitoring of OMT. In spiked recovery experiments using real samples, the method displayed high sensitivity, accuracy, and repeatability, offering potential technical support for on-site detection of organophosphorus pesticide residues. Declarations CRediT authorship contribution statement Shiyi Wang : Writing – original draft, Visualization, Software, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Kunyang Feng : Writing – review & editing, Visualization, Supervision, Software, Methodology, Investigation. Minzhu Zhao : Validation, Software, Investigation, Formal analysis. Yusen Wang: Resources. Xin He: Investigation. Qi Wang: Conceptualization, Methodology, Software . Jianbo Li and Hanting Wang: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Methodology, Funding acquisition. Declaration of competing interest We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted. Funding Declaration This research was funded by the Intelligent Medicine Research Project of Chongqing Medical University (NO:ZHYX202114). Data Availability The datasets generated during and analysed during the current study are available from the corresponding author on reasonable request. References Carpenter BP, Talosig AR, Rose B et al (2023) Understanding and controlling the nucleation and growth of metal–organic frameworks. Chem Soc Rev 52:6918–6937. https://doi.org/10.1039/D3CS00312D Chi J, Song Y, Feng L (2023) A ratiometric fluorescent paper sensor based on dye-embedded MOF for high-sensitive detection of arginine. Biosens Bioelectron 241:115666. https://doi.org/10.1016/j.bios.2023.115666 Ding L, Hong H, Xiao L et al (2021) Nanoparticles-doped induced defective ZIF-8 as the novel cathodic luminophore for fabricating high-performance electrochemiluminescence aptasensor for detection of omethoate. Biosens Bioelectron 192:113492. https://doi.org/10.1016/j.bios.2021.113492 Fonseca RRF, Gaspar RDL, Raimundo IM, Luz PP (2019) Photoluminescent Tb3+-based metal-organic framework as a sensor for detection of methanol in ethanol fuel. J Rare Earths 37:225–231. https://doi.org/10.1016/j.jre.2018.07.006 Gan Z, Hu X, Xu X et al (2021) A portable test strip based on fluorescent europium-based metal–organic framework for rapid and visual detection of tetracycline in food samples. Food Chem 354:129501. https://doi.org/10.1016/j.foodchem.2021.129501 Han Q, Zhang D, Zhang R et al (2022) DNA-functionalized metal-organic framework ratiometric nanoprobe for MicroRNA detection and imaging in live cells. Sens Actuators B 361:131676. https://doi.org/10.1016/j.snb.2022.131676 He Y, Zou H, Jiang X et al (2025) A smartphone-assisted fluorescent sensor using Eu/Tb-MOF nanorods for ultrasensitive and visual monitoring of carbendazim in food samples. Microchem J 209:112602. https://doi.org/10.1016/j.microc.2024.112602 Huang P, Wu W, Li M et al (2024) Metal-organic framework-based nanoarchitectonics: A promising material platform for electrochemical detection of organophosphorus pesticides. Coord Chem Rev 501:215534. https://doi.org/10.1016/j.ccr.2023.215534 Jiang W, Yang Z, Tong F et al (2023) Two birds with one stone: An enzyme-regulated ratiometric fluorescent and photothermal dual-mode probe for organophosphorus pesticide detection. Biosens Bioelectron 224:115074. https://doi.org/10.1016/j.bios.2023.115074 Li S, Zhang Z (2021) Recent advances in the construction and analytical applications of carbon dots-based optical nanoassembly. Talanta 223:121691. https://doi.org/10.1016/j.talanta.2020.121691 Liu D, Jiang X, Li X et al (2026) A ratiometric fluorescent paper–based sensor based on Fe/Eu-MOF for visual and sensitive detection of diethylstilbestrol. Biosens Bioelectron 291:118017. https://doi.org/10.1016/j.bios.2025.118017 Liu X, Song J, Zhang X et al (2023) A highly selective and sensitive europium-organic framework sensor for the fluorescence detection of fipronil in tea. Food Chem 413:135639. https://doi.org/10.1016/j.foodchem.2023.135639 Luo M, Cai J, Pu S et al (2025) Supra-carbon dots for methyl-paraoxon detection using a new controllable IFE-based method. J Adv Res S2090123225008409. https://doi.org/10.1016/j.jare.2025.10.045 SSh MA, Algethami FK, Omer KM (2025) Improving ratiometric-based analysis via designing intense bi-ligand metal-organic frameworks: Dual-mode for detection of amoxicillin in milk and pharmaceutical samples. Food Chem 491:145185. https://doi.org/10.1016/j.foodchem.2025.145185 Qi X, Zhu J, Yuan Y et al (2026) Porous electrospun membranes with regenerable bifunctionality for on-site uranium detection and efficient capture. Desalination 623:119847. https://doi.org/10.1016/j.desal.2026.119847 Tan H, Wu X, Weng Y et al (2020) Self-assembled FRET nanoprobe with metal–organic framework as a scaffold for ratiometric detection of hypochlorous acid. Anal Chem 92:3447–3454. https://doi.org/10.1021/acs.analchem.9b05565 Umapathi R, Park B, Sonwal S et al (2022) Advances in optical-sensing strategies for the on-site detection of pesticides in agricultural foods. Trends Food Sci Technol 119:69–89. https://doi.org/10.1016/j.tifs.2021.11.018 Wagner M, Andrew Lin K-Y, Oh W-D, Lisak G (2021) Metal-organic frameworks for pesticidal persistent organic pollutants detection and adsorption – a mini review. J Hazard Mater 413:125325. https://doi.org/10.1016/j.jhazmat.2021.125325 Wu K-J, Wu C, Fang M et al (2021) Application of metal–organic framework for the adsorption and detection of food contamination. TRAC Trends Anal Chem 143:116384. https://doi.org/10.1016/j.trac.2021.116384 Xie Y, Sun G, Li J, Sun L (2023) Multimode emission from lanthanide-based metal–organic frameworks for advanced information encryption. Adv Funct Mater 33:2303663. https://doi.org/10.1002/adfm.202303663 Xu X, Zhang W, Huang J, Xu H (2024) Colorimetric sensors for detection of organophosphorus pesticides in food: From sensing strategies to chemometrics driven discrimination. Trends Food Sci Technol 152:104683. https://doi.org/10.1016/j.tifs.2024.104683 Xu Y, Wang H, Li X et al Metal–organic framework for the extraction and detection of pesticides from food commodities. https://doi.org/10.1111/1541-4337.12675 Yang Z-R, Wang M-M, Wang X-S, Yin X-B (2017) Boric-acid-functional lanthanide metal–organic frameworks for selective ratiometric fluorescence detection of fluoride ions. Anal Chem 89:1930–1936. https://doi.org/10.1021/acs.analchem.6b04421 Yao J, Wang Z, Guo L et al (2020) Advances in immunoassays for organophosphorus and pyrethroid pesticides. TRAC Trends Anal Chem 131:116022. https://doi.org/10.1016/j.trac.2020.116022 Yue X, Fu L, Li Y et al (2023) Lanthanide bimetallic MOF-based fluorescent sensor for sensitive and visual detection of sulfamerazine and malachite. Food Chem 410:135390. https://doi.org/10.1016/j.foodchem.2023.135390 Zhang Z, Lou Y, Guo C et al (2021) Metal–organic frameworks (MOFs) based chemosensors/biosensors for analysis of food contaminants. Trends Food Sci Technol 118:569–588. https://doi.org/10.1016/j.tifs.2021.10.024 Zheng X, Zhang Q, Ma Q et al (2023) A chiral metal-organic framework {(HQA)(ZnCl2)(2.5H2O)}n for the enantioseparation of chiral amino acids and drugs. J Pharm Anal 13:421–429. https://doi.org/10.1016/j.jpha.2023.03.003 Scheme 1 Scheme 1 is available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files SupplementaryMaterial.docx Scheme1.png Scheme 1. Schematic illustration for fluorescence sensing of OMT by Eu-MOF. Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 10 May, 2026 Reviews received at journal 05 May, 2026 Reviews received at journal 28 Apr, 2026 Reviewers agreed at journal 23 Apr, 2026 Reviews received at journal 23 Apr, 2026 Reviewers agreed at journal 21 Apr, 2026 Reviewers agreed at journal 21 Apr, 2026 Reviewers agreed at journal 21 Apr, 2026 Reviewers agreed at journal 21 Apr, 2026 Reviewers invited by journal 21 Apr, 2026 Editor assigned by journal 31 Mar, 2026 Submission checks completed at journal 31 Mar, 2026 First submitted to journal 30 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9273730","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":630838267,"identity":"75f8eb38-f191-4f11-865a-cb2d1824004c","order_by":0,"name":"Shiyi Wang","email":"","orcid":"","institution":"Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Shiyi","middleName":"","lastName":"Wang","suffix":""},{"id":630838268,"identity":"2c20c88e-9745-451d-9cfe-0dd3da87c513","order_by":1,"name":"Kunyang Feng","email":"","orcid":"","institution":"Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Kunyang","middleName":"","lastName":"Feng","suffix":""},{"id":630838269,"identity":"f8b98eae-59e6-4c76-80e2-0f1431532980","order_by":2,"name":"Minzhu Zhao","email":"","orcid":"","institution":"Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Minzhu","middleName":"","lastName":"Zhao","suffix":""},{"id":630838270,"identity":"16f60e7c-a7c2-42af-8975-08d8bac2be5e","order_by":3,"name":"Yusen Wang","email":"","orcid":"","institution":"Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Yusen","middleName":"","lastName":"Wang","suffix":""},{"id":630838271,"identity":"9e66c5e4-c895-469c-b3c7-6f5d8480b37a","order_by":4,"name":"Xin He","email":"","orcid":"","institution":"Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Xin","middleName":"","lastName":"He","suffix":""},{"id":630838272,"identity":"acb6f353-83d7-4ae3-9c71-3714a6cf34b9","order_by":5,"name":"Qi Wang","email":"","orcid":"","institution":"Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Qi","middleName":"","lastName":"Wang","suffix":""},{"id":630838273,"identity":"766da262-8941-4d6a-900b-2fe41f9fde0b","order_by":6,"name":"Hanting Wang","email":"","orcid":"","institution":"Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Hanting","middleName":"","lastName":"Wang","suffix":""},{"id":630838275,"identity":"f97272c3-2888-41ee-8c30-414578c19601","order_by":7,"name":"Jianbo Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAv0lEQVRIiWNgGAWjYBACNmbG5gcfDGxgXCK08LE3HzOcUZFGghY5nmMJ0jxnDpOghU0ix8CYt+28PN+1MwYMH8oOM/DPbiCs5eHcttuGM2/nGDDOOHeYQeLOAcJaDN623U4wAGph5m07zGAgkUBYiwRv2zmIlr9EaQF6X5LnzAGIFkaitEACORnol7SCgz3n0nkkbhDQIt8Mjko7eb7byRsf/CizluOfQUALAhwAIwYeYtVDtIyCUTAKRsEowAoAUYxEXZxVFoYAAAAASUVORK5CYII=","orcid":"","institution":"Chongqing Medical University","correspondingAuthor":true,"prefix":"","firstName":"Jianbo","middleName":"","lastName":"Li","suffix":""}],"badges":[],"createdAt":"2026-03-31 03:23:34","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9273730/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9273730/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108225510,"identity":"397ca811-28a4-4ace-acea-66384d6f4e51","added_by":"auto","created_at":"2026-04-30 16:19:11","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":535173,"visible":true,"origin":"","legend":"\u003cp\u003e(A) SEM pictures for Eu-BBDC/BDC-OH nanorods. (B-C) TEM picture for Eu-BBDC/BDC-OH nanorods. (D) HAADF-STEM and corresponding elemental mapping images of Eu-BBDC/BDC-OH nanorods.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-9273730/v1/3bb4b7312b94cfb8d7d93df9.png"},{"id":108225513,"identity":"99576db3-6570-42de-a1b6-d3fbe4ef398b","added_by":"auto","created_at":"2026-04-30 16:19:11","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":392467,"visible":true,"origin":"","legend":"\u003cp\u003e(A) XPS spectrum of Eu-BBDC/BDC-OH nanorods; (B-D) High-resolution XPS spectrum of Eu 3d (B), C 1s (C), and O 1s (D).\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-9273730/v1/23c5c09f004d0f7f6d6bc653.png"},{"id":109081134,"identity":"7c8246a0-b35d-44b8-84c7-57de00f1a7f2","added_by":"auto","created_at":"2026-05-12 12:00:38","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":495212,"visible":true,"origin":"","legend":"\u003cp\u003e(A) FT-IR spectra of BDC-OH, BBDC, and Eu-BBDC/BDC-OH. (B) UV–vis absorption and FL spectra of Eu-BBDC/BDC-OH nanorods. Insert: digital picture of Tb-MOF excited at 254 nm UV lamp. (C) FL emission spectra of Eu-BBDC/BDC-OH nanorods under the excitation from 245 to 290nm. (D) FL emission spectra of Eu-BBDC/BDC-OH nanorods in the presence and absence of OMT.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-9273730/v1/2c6504fa1245dec7f4c2de56.png"},{"id":108225515,"identity":"f4bef1ae-a3be-436e-9814-f0d2daa3bcd7","added_by":"auto","created_at":"2026-04-30 16:19:11","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":362244,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Fluorescence spectra of Eu-BBDC/BDC-OH nanorods after introducing various amounts of OMT. (B) Fluorescence profiles of Eu-BBDC/BDC-OH in the presence of different concentrations of OMT under the single excitation at 250 nm. (C) Relationship between F\u003csub\u003e614\u003c/sub\u003e/F\u003csub\u003e430\u003c/sub\u003e and OMT concentration. (D-E) The correlation curve between F\u003csub\u003e614\u003c/sub\u003e/F\u003csub\u003e430\u003c/sub\u003e and the concentration of OMT over the range of 0.025-0.3 and 0.3-0.9 µg/mL. (F) The (F\u003csub\u003e0\u003c/sub\u003e–F)/F\u003csub\u003e0 \u003c/sub\u003eratio of Eu-BBDC/BDC-OH in the presence of various substances, including OMT and other interferents. The error bar represents the standard deviation (n = 3).\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-9273730/v1/83e4e94039b73d2cb5a76488.png"},{"id":108491243,"identity":"f3211007-ce16-4745-8b02-f9125cecb973","added_by":"auto","created_at":"2026-05-05 09:53:02","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":232417,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Operational workflow for OMT detection using fluorescent test strips, with corresponding color transition from red to purple under 254 nm UV illumination. (B) Schematic of smartphone–sensor–assisted OMT detection platform. (C) Linear relationship between R/B ratio and OMT concentration (0–1 μg/mL). The error bar represents the standard deviation (n = 3).\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-9273730/v1/22ad717906186c7da603bb08.png"},{"id":108225516,"identity":"5cdfb033-16f7-49ba-81dc-301822bd5c28","added_by":"auto","created_at":"2026-04-30 16:19:11","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":429145,"visible":true,"origin":"","legend":"\u003cp\u003e(A) UV–vis absorption spectra of OMT, and FL excitation and emission spectra of Eu-MOF. (B) UV–vis absorption spectra of Eu-MOF, OMT, Eu-MOF + OMT, and superposition data of Eu -MOF and OMT. (C) FT–IR spectra of Eu–MOF and Eu-MOF + OMT. (D) Fluorescence lifetime decay profiles of Eu–MOF before and after the addition of OMT.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-9273730/v1/8e548c664d290b9dd99db2e3.png"},{"id":109204606,"identity":"8578b56d-1ee9-4252-974f-0fb6497e5b7b","added_by":"auto","created_at":"2026-05-13 15:01:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2658679,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9273730/v1/370a7a80-b5cf-4631-b053-d0b6be21a1dc.pdf"},{"id":108225511,"identity":"c7768f88-679f-4141-be80-0a84a7cda31b","added_by":"auto","created_at":"2026-04-30 16:19:11","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":722596,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-9273730/v1/aec6a2136df82caf47e39313.docx"},{"id":108492207,"identity":"c27f6dca-74bb-457d-be01-ff1b2bfa328b","added_by":"auto","created_at":"2026-05-05 09:57:10","extension":"png","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":290170,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScheme 1.\u003c/strong\u003e Schematic illustration for fluorescence sensing of OMT by Eu-MOF.\u003c/p\u003e","description":"","filename":"Scheme1.png","url":"https://assets-eu.researchsquare.com/files/rs-9273730/v1/06c01354cbc62eb60741a4b0.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"A smartphone-assisted fluorescent sensor using Eu -MOF nanorods for visual and sensitive detection of Organophosphorus pesticides","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eOrganophosphorus pesticides (OPs) are compounds containing phosphate or thiophosphate ester structures. Due to their high efficacy and broad-spectrum insecticidal activity, OPs have been extensively used in global agricultural production to control pests and diseases, playing a crucial role in safeguarding crop yields (Xu et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). However, most OPs are resistant to natural degradation and can enter the food chain through bioaccumulation, leading to widespread residues in agricultural products, water sources, and processed foods (Jiang et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Long-term low-dose exposure to OPs residues can cause chronic damage to various human systems, including but not limited to the nervous and endocrine systems, whereas high-dose exposure may even lead to acute poisoning and life-threatening conditions (Yao et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Therefore, monitoring and controlling OPs residues in food and environmental media have become important public safety issues. Omethoate (O, O-dimethyl-S-methylcarbamoylmethyl thiophosphate, OMT) is a typical systemic organophosphorus insecticide and acaricide, widely applied in the protection of crops such as cotton, wheat, and corn against pests, making it one of the commonly used OPs in agricultural production (Ding et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Establishing rapid, sensitive, and reliable analytical methods for OMT is a prerequisite for implementing effective residue monitoring and ensuring food safety.\u003c/p\u003e \u003cp\u003eTo date, Traditional analytical techniques for OPs residues mainly include gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography (HPLC), and enzyme-linked immunosorbent assay (ELISA) (Umapathi et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Although these methods provide high sensitivity and accuracy, they are hindered by limitations including costly instrumentation, complex operational procedures, labor-intensive sample pretreatment, and prolonged detection cycles, rendering them inadequate for on-site rapid testing demands. Therefore, the development of simple and rapid on-site detection techniques is of significant importance. Metal-Organic Frameworks (MOFs) are a class of crystalline porous materials formed by the self-assembly of metal ions or metal clusters with organic ligands via coordination bonds (Carpenter et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Owing to their tunable pore structures, good chemical stability, and excellent optical properties, MOFs are regarded as an ideal platform for constructing fluorescent sensors (Zhang et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In recent years, MOF-based sensing materials have demonstrated significant potential in the field of pesticide detection (Huang et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The high specific surface area and adjustable pore size of MOFs enable efficient adsorption and enrichment of target pesticide molecules, thereby significantly improving detection sensitivity (Wagner et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Wu et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Moreover, by rationally selecting metal centers and organic ligands, high selective recognition of specific pesticide molecules can be achieved, further enhancing detection accuracy (Xu et al.). Among various MOFs materials, lanthanide-based metal-organic frameworks (Ln-MOFs) exhibit unique photoluminescence properties due to ligand-to-metal charge transfer, making them particularly suitable for optical sensing (Xie et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Mohammed Ameen et al. 2025; Qi et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2026\u003c/span\u003e). Furthermore, with the development of smartphone-based portable sensing platforms, the built-in camera and RGB color analysis can convert fluorescence signals into digital output. This allows real-time, on-site detection without the need for sophisticated instruments by monitoring changes in the red-to-blue emission intensity ratio induced by analytes (Liu et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2026\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e This study synthesized a dual-ligand Ln-MOFs (Eu-BBDC/BDC-OH) nanorods and constructed a novel smartphone-assisted ratiometric fluorescence sensing platform for the specific, highly sensitive, and visual detection of OMT (Scheme 1). Based on the inherent dual-emission characteristics of Eu-BBDC/BDC-OH, this sensor enables the quantitative analysis of OMT by monitoring the consistent changes in the intensity ratio (F\u003csub\u003e614\u003c/sub\u003e/F\u003csub\u003e430\u003c/sub\u003e) of characteristic fluorescence peaks before and after the addition of OMT. Experimental results indicate that the sensing platform exhibits excellent detection sensitivity and high selectivity toward OMT. To further validate its potential for practical applications, the sensor was successfully employed for the detection of OMT residues in strawberries and cucumbers, demonstrating reliable recovery rates and precision. This work shows promising potential for the development of portable, on-site rapid detection devices targeting OPs.\u003c/p\u003e \u003cp\u003e \u003cb\u003eScheme 1.\u003c/b\u003e Schematic illustration for fluorescence sensing of OMT by Eu-MOF.\u003c/p\u003e"},{"header":"2. Material and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Reagents and instruments\u003c/h2\u003e \u003cp\u003eEu (Cl)\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO (99.9%), 3,5-Dicarboxyphenylboronic acid (BBDC,\u0026ge;98%), 2-Hydroxyterephthalic acid (BDC-OH, \u0026ge;\u0026thinsp;98%), glucose (Glc), glutathione (GSH), arginine (Arg), glycine (Gly), L-cysteine (Cys), valine(Val), and were provided by Aladdin (Shanghai, China).Omethoate (OMT, 98.6%), dimethoate (DMT), malathion (MAL), methomyl (MET), isocarbophos (ISO), iprobenfos (IBP) were purchased from TMRM Quality Inspection Technology Co., Ltd. (Changzhou, China), all belong to chromatographic purity. CaCl\u003csub\u003e2\u003c/sub\u003e, CoCl\u003csub\u003e2\u003c/sub\u003e, KCl, NH\u003csub\u003e4\u003c/sub\u003eCl, ZnSO4, MnSO4, N, N-dimethylformamide (DMF), and anhydrous ethanol were provided by Macklin (Shanghai, China). All unmarked purities belong to the analytical or commercial grade.\u003c/p\u003e \u003cp\u003eScanning electron microscopy (SEM) images were acquired using a Hitachi SU8020 microscope (Japan). Transmission electron microscopy (TEM) images were obtained with a Tecnai G2 12 TEM instrument (FEI). X-ray diffraction (XRD) patterns were recorded on a Bruker D8 Advance diffractometer. Thermogravimetric analysis (TGA) was performed on a Mettler TG-DSC 3\u0026thinsp;+\u0026thinsp;analyzer. UV\u0026ndash;vis absorption spectra were measured with a Shimadzu UV-2600 spectrophotometer. Fluorescence (FL) spectra were collected on an Edinburgh FS5 spectrofluorometer. Zeta potential analysis was carried out using a Malvern Zetasizer Nano ZS90. Fourier transform infrared (FT\u0026ndash;IR) spectra were acquired with a Thermo iS50 spectrometer. X-ray photoelectron spectroscopy (XPS) data were obtained using a Thermo ESCALAB Xi+ spectrometer. Fluorescence lifetime decays were measured with an Edinburgh FLS980 spectrometer.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Synthesis of Eu-MOF\u003c/h2\u003e \u003cp\u003eThe Eu-BBDC/BDC-OH was prepared using a modified solvothermal technique based on the literature (He et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). In brief, 0.1 mmol of Eu (Cl)\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO in 3 mL of ultrapure water and a sonicated mixture of 0.1 mmol BBDC and 0.005 mmol BDC-OH in 7 mL of DMF were combined. The resulting solution was stirred for 40 minutes, transferred to a 20 mL Teflon-lined autoclave, and reacted at 150\u0026deg;C for 12 h in a muffle furnace.\u003c/p\u003e \u003cp\u003eAfter naturally cooling to room temperature, the precipitate was collected via centrifugation (10000 rpm, 5 min), followed by repeated washing with DMF and ethanol to remove residual reactants. The final product was dried under vacuum at 60 \u003csup\u003e◦\u003c/sup\u003eC to obtain Eu-BBDC/BDC-OH powder.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Ratiometric fluorescent detection of OMT\u003c/h2\u003e \u003cp\u003eThe Eu-BBDC/BDC-OH powder was dispersed in ultrapure water and ultrasonicated for 20 min to obtain a stable probe suspension (80 \u0026micro;g/ mL). Subsequently, varying amounts of OMT (0\u0026ndash;1.0 \u0026micro;g/mL) were introduced into the above solution. The fluorescence emission spectra and corresponding visual color changes were recorded under an excitation wavelength of 250 nm. To assess the specificity of the Eu-BBDC/BDC-OH probe toward OMT, we evaluated its response to a series of potential interferents, including structural analogs of OMT (dimethoate, malathion, methomyl, isocarbophos, and iprobenfos), representative amino acids (GSH, arginine, glycine, L-cysteine, and valine), and prevalent inorganic ions (Ca\u003csup\u003e2+\u003c/sup\u003e, K\u003csup\u003e+\u003c/sup\u003e, NH\u003csup\u003e4+\u003c/sup\u003e, Zn\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e2+\u003c/sup\u003e, and Co\u003csup\u003e2+\u003c/sup\u003e). These comparative tests were conducted under identical experimental conditions.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Detection of OMT by smartphone\u0026ndash;assisted test strip\u003c/h2\u003e \u003cp\u003eTo prepare the fluorescent test strips, filter paper pieces (1.0 \u0026times; 1.0 cm\u003csup\u003e2\u003c/sup\u003e) were soaked in probe solution (80 \u0026micro;g/mL) for 48 h, followed by drying under ambient conditions (Chi et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The resulting strips were then exposed to varying concentrations of OMT (0\u0026ndash;1.0 \u0026micro;g/mL), and fluorescence color variations were recorded using a smartphone under 254 nm illumination in a dark box. Image analysis was conducted by extracting RGB values from the captured images using the smartphone\u0026rsquo;s built\u0026ndash;in software. Finally, a linear calibration curve was constructed by correlating the R/B (red\u0026ndash;to\u0026ndash;blue) ratio with OMT concentration.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Detection of OMT in real samples\u003c/h2\u003e \u003cp\u003eCucumber and strawberry were selected as representative food matrices to evaluate the applicability of the fluorescent probe. Both sample types were purchased from a local supermarket in Chongqing. To maintain the spiked concentrations of OMT in the food sample matrix at 0.2, 0.4 and 0.8 \u0026micro;g/mL, 5g of homogenized cucumber and strawberry samples were added to a known variable OMT standard solution (20 \u0026micro;L), and the spiked samples were then vortexed with 15 mL of dichloromethane for 2 min. After removing insoluble material, the mixed solution was heated to 50\u0026deg;C for 10 min to remove the dichloromethane. The residue was then redissolved using 2 mL of DMF. Real samples were detected using the same method as previously described, recording each fluorescence assay at least three times.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Characterizations and optical performances\u003c/h2\u003e \u003cp\u003eUsing SEM and TEM, the morphology and microstructure of Eu-BBDC/BDC-OH nanorods were studied. The SEM analysis revealed that the Eu-BBDC/BDC-OH composite exhibits a well-defined rod-like morphology (Fig.\u0026nbsp;1A\u0026ndash;B). Furthermore, the TEM imaging further confirmed the presence of rod-shaped nanocrystals, with a length of approximately 200 nm (Fig.\u0026nbsp;1C). The elemental composition and distribution within the Eu-BBDC/BDC-OH were evaluated using a high\u0026ndash;resolution TEM (Fig.\u0026nbsp;1D). The elemental distribution map showed that europium (Eu), carbon (C), oxygen (O), and boron (B) were uniformly distributed within the framework. Energy-dispersive X-ray spectroscopy (EDS) verified the successful incorporation of Eu, further confirming the successful preparation of the nanorods (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). The crystalline phases of the nanorods were demonstrated by the XRD measurement (Fig. S2). The diffraction peaks of Eu-BBDC/BDC-OH match well with the simulated pattern, indicating high crystallinity and the absence of impurity phases. Additionally, the thermal stability of Eu-BBDC/BDC-OH was obtained by TGA analyzer (Fig. S3). We can observe that the weight loss process of Eu-BBDC/BDC-OH is divided into two stages. The first weight loss occurred between 30 and 550 \u003csup\u003e◦\u003c/sup\u003eC with a mass loss of 0.6692 mg (21.59%), which could be attributed to the loss of free water leading to the loss of mass. In the second stage, between 550 and 600 \u003csup\u003e◦\u003c/sup\u003eC, with a mass loss of 0.2297 mg (7.41%), the skeleton of Eu-BBDC/BDC-OH starts to collapse and rapidly loses weight, with a mass residual of 71%. The aforementioned findings showed that the Eu-BBDC/BDC-OH has good thermal stability (He et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cb\u003eFigure\u0026nbsp;1.\u003c/b\u003e (A) SEM pictures for Eu-BBDC/BDC-OH nanorods. (B-C) TEM picture for Eu-BBDC/BDC-OH nanorods. (D) HAADF-STEM and corresponding elemental mapping images of Eu-BBDC/BDC-OH nanorods.\u003c/p\u003e \u003cp\u003eThe XPS analysis was performed to get more information about Eu-BBDC/BDC-OH nanorods. The survey XPS spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003eA) show the existence of C, O, and Eu. The high-resolution Eu 3d spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003eB) was fitted to Eu\u003csup\u003e3+\u003c/sup\u003e3d\u003csub\u003e3/2\u003c/sub\u003e (1165.2 eV) and Eu\u003csup\u003e3+\u003c/sup\u003e3d\u003csub\u003e5/2\u003c/sub\u003e (1135.3 eV) (Gan et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The high-resolution C 1s spectrum (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003eC) displayed two peaks at 289.1 and 284.9 eV, which were attributed to C-O and C-C/C\u0026thinsp;=\u0026thinsp;C bonds, respectively (Fonseca et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The O 1s spectrum (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003eD) show two peaks at 531.6 and 532.0 eV, attributed to the Eu-O (metal oxygen single bond) and O\u0026thinsp;=\u0026thinsp;C-O groups, respectively (Han et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The successful fabrication of Eu-BBDC/BDC-OH nanorods could be proven by the above results.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFourier transform infrared (FT-IR) spectra of BDC-OH, BBDC and Eu-BBDC/BDC-OH were recorded respectively (Fig.\u0026nbsp;3A). After Eu-MOF formation, the broad hydroxyl characteristic bands of BDC-OH and BBDC in the 2500\u0026ndash;3500 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e region were significantly attenuated, which was ascribed to the partial or full deprotonation of these ligands during synthesis (Liu et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The successful coordination of Eu\u0026sup3;⁺ ions with the carboxylate groups is confirmed by the disappearance of the C\u0026thinsp;=\u0026thinsp;O stretching vibration at ~\u0026thinsp;1700 cm⁻\u0026sup1; and the concurrent emergence of the symmetric and antisymmetric stretching vibrations of the -COO⁻ groups at 1350\u0026ndash;1450 and 1550\u0026ndash;1610 cm⁻\u0026sup1;, respectively (Zheng et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The peak at 775 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was associated with the Eu-O stretching vibration, indicating that the Eu atoms interact with the -COO group (Yue et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Given the agreement between the FT-IR and XPS data, it can be inferred that the generated Eu-BBDC/BDC-OH contains a great amount of carboxyl and hydroxyl functional groups improves the stability of material and hydrophilicity.\u003c/p\u003e \u003cp\u003e The FL and UV-vis spectra of Eu-BBDC/BDC-OH nanorods were applied to analyze their optical properties in detail. As shown in Fig.\u0026nbsp;3B, the Eu-BBDC/BDC-OH nanorods exhibit characteristic emission peaks at approximately 430 and 614 nm, which are attributed to the ligand itself and the ⁵D₀\u0026rarr;⁷FJ (J\u0026thinsp;=\u0026thinsp;1,2,3,4) transitions of Eu\u0026sup3;⁺, respectively (Yang et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). The overall fluorescence of Eu-BBDC/BDC-OH nanorods exhibits bright red color under 365 nm UV irradiation. The fluorescence values at 430 and 614 nm are highest under 250 nm excitation wavelength (Fig.\u0026nbsp;3C). Thus, the subsequent experiments were carried out to select 250 nm as the best excitation wavelength. OMT has a strong ability to reduce the fluorescence of Eu/Tb-MOF (Fig.\u0026nbsp;3D). Additionally, the surface of Eu-BBDC/BDC-OH is positively charged, while OMT is negatively charged. The potential of Eu-BBDC/BDC-OH significantly decreased upon the addition of OMT, indicating the electrostatic attraction between MOF and OMT (Fig. S4). According to these findings, the Eu-BBDC/BDC-OH nanorods have the ability to serve as a fluorescent sensor for monitoring OMT.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFigure\u0026nbsp;3.\u003c/b\u003e (A) FT-IR spectra of BDC-OH, BBDC, and Eu-BBDC/BDC-OH. (B) UV\u0026ndash;vis absorption and FL spectra of Eu-BBDC/BDC-OH nanorods. Insert: digital picture of Tb-MOF excited at 254 nm UV lamp. (C) FL emission spectra of Eu-BBDC/BDC-OH nanorods under the excitation from 245 to 290nm. (D) FL emission spectra of Eu-BBDC/BDC-OH nanorods in the presence and absence of OMT.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Fluorescence assay of OMT\u003c/h2\u003e \u003cp\u003eUsing a 250 nm excitation, a range of OMT concentrations (0\u0026ndash;1\u0026micro;g/mL) were evaluated in order to study the sensitivity of Eu-BBDC/BDC-OH for OMT sensing. The optimal detection conditions were finally determined as follows to be an Eu\u0026ndash;MOF concentration of 80 \u0026micro;g/mL, reaction pH of 7.0, immediate fluorescence measurement, and operation at room temperature (Fig. S5). Under optimal conditions, a quick, sensitive and dependable analytical method for detecting OMT has been established using fluorescent Eu-BBDC/BDC-OH nanorods. Firstly, the sensing performance of Eu-BBDC/BDC-OH for OMT was validated. As the OMT concentration increased, the FL emission of Eu-BBDC/BDC-OH at 614 nm decreased significantly, while the emission at 430 nm descended slowly (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e4\u003c/span\u003eA). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e4\u003c/span\u003eB, with an increase in the OMT concentration, we can clearly observe that the fluorescence values at F\u003csub\u003e430\u003c/sub\u003e and F\u003csub\u003e614\u003c/sub\u003e dropped, and the red fluorescence became weaker. Therefore, we constructed a fluorescence sensor to realize the quantitative detection of OMT. Two regression equations were developed between the OMT concentration (0-0.3and 0.3-1.0 \u0026micro;g/mL) and F\u003csub\u003e614\u003c/sub\u003e/F\u003csub\u003e430\u003c/sub\u003e. The regression equation can be written as ln F\u003csub\u003e614\u003c/sub\u003e/F\u003csub\u003e430\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;2.774X\u0026thinsp;+\u0026thinsp;0.2232 (R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.9968) ranging from 0.025 to 0.3 \u0026micro;g/mL, and ln F\u003csub\u003e614\u003c/sub\u003e/F\u003csub\u003e430\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;5.991X\u0026thinsp;\u0026minus;\u0026thinsp;0.6593 (R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.9940) ranging from 0.3 to 0.9 \u0026micro;g/mL (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e4\u003c/span\u003eC\u0026ndash;E). Furthermore, the formula LOD\u0026thinsp;=\u0026thinsp;3σ/k was utilized to determine the detection limit (LOD), which came out to be 7.35 ng/mL. Compared with previously reported methods (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e), the proposed radiometric fluorescent probe offers not only superior sensitivity but also a more straightforward and efficient detection procedure, highlighting its strong potential for practical pesticide residue monitoring in food safety applications.\u003c/p\u003e \u003cp\u003eTo assess the specificity and anti\u0026ndash;interference capability of the Eu-BBDC/BDC-OH sensor, fluorescence responses were evaluated against a panel of structurally and chemically diverse interferents, including structural analogs of OMT, amino acids, and metal ions. As depicted in Fig.\u0026nbsp;3F, the introduction of OMT alone induced a pronounced fluorescence quenching of approximately 59% in the Eu-BBDC/BDC-OH system. In contrast, the presence of other potential interferents led to only negligible variations in fluorescence intensity, underscoring the exceptional of the system selectivity for OMT. To further challenge the selectivity, we investigated mixed systems containing OMT alongside a significant excess of these interferents (Fig. S6). The observed quenching efficiency remained consistent with that of the system containing only OMT, confirming the robust anti-interference capability and signal stability. Collectively, these findings affirm that the Eu-BBDC/BDC-OH probe possesses not only favorable chemical stability but also excellent selectivity for OMT detection.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.4. Smartphone\u0026ndash;integrated paper\u0026ndash;based sensing platform\u003c/h2\u003e \u003cp\u003eFor the visual detection of target analytes, this study developed a paper-based porous fluorescent sensor. The test paper was prepared by immersing filter paper in a uniformly dispersed suspension of Eu-MOF, followed by drying at room temperature. The MOF-coated strips were then exposed to OMT solutions at varying concentrations (0\u0026ndash;1\u0026micro;g/mL). Under excitation by 254 nm ultraviolet light, the strips exhibited a concentration-dependent fluorescence color change, transitioning gradually from red to purple as the OMT concentration increased. The fluorescence response was captured using a smartphone camera (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e5\u003c/span\u003eA and B). Image analysis based on RGB values revealed a strong linear correlation between the red-to-blue (R/B) intensity ratio and the concentration of OMT (y = -1.72929X\u0026thinsp;+\u0026thinsp;2.42882, R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.9806) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e5\u003c/span\u003eC).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.5. Detection of OMT in real samples\u003c/h2\u003e \u003cp\u003eTo validate the practical application of the probe, the Eu-BBDC/BDC-OH was applied to detect strawberry and cucumber samples containing OMT. As summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the recovery efficiencies were between 95.74% and 101.1%, with RSD of less than 5.91%. The good performances demonstrated that the Eu-BBDC/BDC-OH probe can be utilized to determine OMT in actual samples with excellent precision and accuracy.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eResults for OMT assay in strawberry and cucumber (n\u0026thinsp;=\u0026thinsp;3).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSamples\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAdded (\u0026micro;g/mL)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFound (\u0026micro;g/mL)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRecovery (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRSD (n\u0026thinsp;=\u0026thinsp;3,%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStrawberry\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo detected\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.1955\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e97.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5.91\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.3959\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e98.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.57\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.785\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e98.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.62\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCucumber\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo detected\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.1916\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e95.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.98\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.4045\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e101.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.8003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.59\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e\u003cb\u003e3.6. Possible fluorescence quenching mechanism\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eFluorescence quenching occurs principally via static quenching, dynamic quenching, the internal filtration effect (IFE), and fluorescence resonance energy transfer (FRET) (Li and Zhang \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e6\u003c/span\u003eA, OMT exhibits a strong and continuous absorption band in the range of 200\u0026ndash;600 nm, which significantly overlaps with the characteristic excitation and emission wavelengths of Eu-MOF. This indicates that OMT effectively absorbs the excitation and emission energy of Eu-MOF, resulting in fluorescence quenching. Consequently, IFE and FRET were considered as potential quenching mechanisms (Tan et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The UV-vis absorption spectra of Eu-MOF after the addition of OMT show no new absorption peaks and almost completely coincide with the superimposed spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e6\u003c/span\u003eB). Furthermore, the FT-IR spectra confirm that no new chemical bonds are formed upon the introduction of OMT (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e6\u003c/span\u003eC). Thus, the formation of a ground-state complex between Eu-MOF and OMT can be ruled out, excluding static quenching as a possible mechanism. The addition of OMT caused only a minor change in the fluorescence lifetime of Eu-MOF, from 422.31 \u0026micro;s to 407.23 \u0026micro;s, as derived from the decay profiles in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e6\u003c/span\u003eD. The nearly identical lifetime values suggest that FRET is not the dominant quenching mechanism. In conclusion, IFE is identified as the dominant mechanism accounting for the fluorescence quenching of Eu-MOF induced by OMT (Luo et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn conclusion, this study successfully constructed a dual-ligand Ln-MOFs (Eu-BBDC/BDC-OH) nanorods, via a one-pot solvothermal method. The material exhibits a well-defined crystal structure, uniform morphology and elemental distribution, along with distinct fluorescent properties. Based on the IFE, the characteristic red fluorescence of the material at 614 nm can be selectively quenched by OMT, enabling ratiometric fluorescent sensing of the pesticide. Sensing analysis demonstrated good linear responses within two concentration ranges of 0.025\u0026ndash;0.3 \u0026micro;g/mL and 0.3\u0026ndash;0.9 \u0026micro;g/mL, with a low detection limit of 7.35 ng/mL. Furthermore, a smartphone-based fluorescent detection platform was developed, allowing rapid, visual, and real-time monitoring of OMT. In spiked recovery experiments using real samples, the method displayed high sensitivity, accuracy, and repeatability, offering potential technical support for on-site detection of organophosphorus pesticide residues.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCRediT authorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eShiyi Wang\u003c/strong\u003e: Writing \u0026ndash; original draft, Visualization, Software, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. \u003cstrong\u003eKunyang Feng\u003c/strong\u003e: Writing \u0026ndash; review \u0026amp; editing, Visualization, Supervision, Software, Methodology, Investigation. \u003cstrong\u003eMinzhu Zhao\u003c/strong\u003e: Validation, Software, Investigation, Formal analysis.\u003cstrong\u003eYusen Wang: \u003c/strong\u003eResources. \u003cstrong\u003eXin He: \u003c/strong\u003eInvestigation. \u003cstrong\u003eQi Wang:\u003c/strong\u003e Conceptualization, Methodology, Software\u003cstrong\u003e. \u003c/strong\u003e\u003cstrong\u003eJianbo Li and Hanting Wang:\u003c/strong\u003e Writing \u0026ndash; review \u0026amp; editing, Writing \u0026ndash; original draft, Visualization, Validation, Supervision, Methodology, Funding acquisition.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of competing interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eFunding Declaration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was funded by the Intelligent Medicine Research Project of Chongqing Medical University (NO:ZHYX202114).\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eCarpenter BP, Talosig AR, Rose B et al (2023) Understanding and controlling the nucleation and growth of metal\u0026ndash;organic frameworks. Chem Soc Rev 52:6918\u0026ndash;6937. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1039/D3CS00312D\u003c/span\u003e\u003cspan address=\"10.1039/D3CS00312D\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChi J, Song Y, Feng L (2023) A ratiometric fluorescent paper sensor based on dye-embedded MOF for high-sensitive detection of arginine. Biosens Bioelectron 241:115666. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.bios.2023.115666\u003c/span\u003e\u003cspan address=\"10.1016/j.bios.2023.115666\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDing L, Hong H, Xiao L et al (2021) Nanoparticles-doped induced defective ZIF-8 as the novel cathodic luminophore for fabricating high-performance electrochemiluminescence aptasensor for detection of omethoate. Biosens Bioelectron 192:113492. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.bios.2021.113492\u003c/span\u003e\u003cspan address=\"10.1016/j.bios.2021.113492\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFonseca RRF, Gaspar RDL, Raimundo IM, Luz PP (2019) Photoluminescent Tb3+-based metal-organic framework as a sensor for detection of methanol in ethanol fuel. J Rare Earths 37:225\u0026ndash;231. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jre.2018.07.006\u003c/span\u003e\u003cspan address=\"10.1016/j.jre.2018.07.006\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGan Z, Hu X, Xu X et al (2021) A portable test strip based on fluorescent europium-based metal\u0026ndash;organic framework for rapid and visual detection of tetracycline in food samples. Food Chem 354:129501. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.foodchem.2021.129501\u003c/span\u003e\u003cspan address=\"10.1016/j.foodchem.2021.129501\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHan Q, Zhang D, Zhang R et al (2022) DNA-functionalized metal-organic framework ratiometric nanoprobe for MicroRNA detection and imaging in live cells. Sens Actuators B 361:131676. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.snb.2022.131676\u003c/span\u003e\u003cspan address=\"10.1016/j.snb.2022.131676\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHe Y, Zou H, Jiang X et al (2025) A smartphone-assisted fluorescent sensor using Eu/Tb-MOF nanorods for ultrasensitive and visual monitoring of carbendazim in food samples. Microchem J 209:112602. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.microc.2024.112602\u003c/span\u003e\u003cspan address=\"10.1016/j.microc.2024.112602\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHuang P, Wu W, Li M et al (2024) Metal-organic framework-based nanoarchitectonics: A promising material platform for electrochemical detection of organophosphorus pesticides. Coord Chem Rev 501:215534. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.ccr.2023.215534\u003c/span\u003e\u003cspan address=\"10.1016/j.ccr.2023.215534\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJiang W, Yang Z, Tong F et al (2023) Two birds with one stone: An enzyme-regulated ratiometric fluorescent and photothermal dual-mode probe for organophosphorus pesticide detection. Biosens Bioelectron 224:115074. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.bios.2023.115074\u003c/span\u003e\u003cspan address=\"10.1016/j.bios.2023.115074\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi S, Zhang Z (2021) Recent advances in the construction and analytical applications of carbon dots-based optical nanoassembly. Talanta 223:121691. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.talanta.2020.121691\u003c/span\u003e\u003cspan address=\"10.1016/j.talanta.2020.121691\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu D, Jiang X, Li X et al (2026) A ratiometric fluorescent paper\u0026ndash;based sensor based on Fe/Eu-MOF for visual and sensitive detection of diethylstilbestrol. Biosens Bioelectron 291:118017. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.bios.2025.118017\u003c/span\u003e\u003cspan address=\"10.1016/j.bios.2025.118017\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu X, Song J, Zhang X et al (2023) A highly selective and sensitive europium-organic framework sensor for the fluorescence detection of fipronil in tea. Food Chem 413:135639. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.foodchem.2023.135639\u003c/span\u003e\u003cspan address=\"10.1016/j.foodchem.2023.135639\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLuo M, Cai J, Pu S et al (2025) Supra-carbon dots for methyl-paraoxon detection using a new controllable IFE-based method. J Adv Res S2090123225008409. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jare.2025.10.045\u003c/span\u003e\u003cspan address=\"10.1016/j.jare.2025.10.045\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSSh MA, Algethami FK, Omer KM (2025) Improving ratiometric-based analysis via designing intense bi-ligand metal-organic frameworks: Dual-mode for detection of amoxicillin in milk and pharmaceutical samples. Food Chem 491:145185. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.foodchem.2025.145185\u003c/span\u003e\u003cspan address=\"10.1016/j.foodchem.2025.145185\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eQi X, Zhu J, Yuan Y et al (2026) Porous electrospun membranes with regenerable bifunctionality for on-site uranium detection and efficient capture. Desalination 623:119847. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.desal.2026.119847\u003c/span\u003e\u003cspan address=\"10.1016/j.desal.2026.119847\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTan H, Wu X, Weng Y et al (2020) Self-assembled FRET nanoprobe with metal\u0026ndash;organic framework as a scaffold for ratiometric detection of hypochlorous acid. Anal Chem 92:3447\u0026ndash;3454. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/acs.analchem.9b05565\u003c/span\u003e\u003cspan address=\"10.1021/acs.analchem.9b05565\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUmapathi R, Park B, Sonwal S et al (2022) Advances in optical-sensing strategies for the on-site detection of pesticides in agricultural foods. Trends Food Sci Technol 119:69\u0026ndash;89. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.tifs.2021.11.018\u003c/span\u003e\u003cspan address=\"10.1016/j.tifs.2021.11.018\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWagner M, Andrew Lin K-Y, Oh W-D, Lisak G (2021) Metal-organic frameworks for pesticidal persistent organic pollutants detection and adsorption \u0026ndash; a mini review. J Hazard Mater 413:125325. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jhazmat.2021.125325\u003c/span\u003e\u003cspan address=\"10.1016/j.jhazmat.2021.125325\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWu K-J, Wu C, Fang M et al (2021) Application of metal\u0026ndash;organic framework for the adsorption and detection of food contamination. TRAC Trends Anal Chem 143:116384. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.trac.2021.116384\u003c/span\u003e\u003cspan address=\"10.1016/j.trac.2021.116384\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXie Y, Sun G, Li J, Sun L (2023) Multimode emission from lanthanide-based metal\u0026ndash;organic frameworks for advanced information encryption. Adv Funct Mater 33:2303663. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/adfm.202303663\u003c/span\u003e\u003cspan address=\"10.1002/adfm.202303663\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXu X, Zhang W, Huang J, Xu H (2024) Colorimetric sensors for detection of organophosphorus pesticides in food: From sensing strategies to chemometrics driven discrimination. Trends Food Sci Technol 152:104683. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.tifs.2024.104683\u003c/span\u003e\u003cspan address=\"10.1016/j.tifs.2024.104683\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXu Y, Wang H, Li X et al Metal\u0026ndash;organic framework for the extraction and detection of pesticides from food commodities. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/1541-4337.12675\u003c/span\u003e\u003cspan address=\"10.1111/1541-4337.12675\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang Z-R, Wang M-M, Wang X-S, Yin X-B (2017) Boric-acid-functional lanthanide metal\u0026ndash;organic frameworks for selective ratiometric fluorescence detection of fluoride ions. Anal Chem 89:1930\u0026ndash;1936. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/acs.analchem.6b04421\u003c/span\u003e\u003cspan address=\"10.1021/acs.analchem.6b04421\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYao J, Wang Z, Guo L et al (2020) Advances in immunoassays for organophosphorus and pyrethroid pesticides. TRAC Trends Anal Chem 131:116022. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.trac.2020.116022\u003c/span\u003e\u003cspan address=\"10.1016/j.trac.2020.116022\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYue X, Fu L, Li Y et al (2023) Lanthanide bimetallic MOF-based fluorescent sensor for sensitive and visual detection of sulfamerazine and malachite. Food Chem 410:135390. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.foodchem.2023.135390\u003c/span\u003e\u003cspan address=\"10.1016/j.foodchem.2023.135390\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang Z, Lou Y, Guo C et al (2021) Metal\u0026ndash;organic frameworks (MOFs) based chemosensors/biosensors for analysis of food contaminants. Trends Food Sci Technol 118:569\u0026ndash;588. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.tifs.2021.10.024\u003c/span\u003e\u003cspan address=\"10.1016/j.tifs.2021.10.024\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZheng X, Zhang Q, Ma Q et al (2023) A chiral metal-organic framework {(HQA)(ZnCl2)(2.5H2O)}n for the enantioseparation of chiral amino acids and drugs. J Pharm Anal 13:421\u0026ndash;429. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jpha.2023.03.003\u003c/span\u003e\u003cspan address=\"10.1016/j.jpha.2023.03.003\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Scheme 1","content":"\u003cp\u003eScheme 1 is available in the Supplementary Files section.\u003c/p\u003e\n"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"food-analytical-methods","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Food Analytical Methods](https://www.springer.com/journal/12161)","snPcode":"12161","submissionUrl":"https://submission.nature.com/new-submission/12161/3","title":"Food Analytical Methods","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Metal-organic frameworks, Organophosphorus pesticides, Fluorescent sensor, Smartphone sensing","lastPublishedDoi":"10.21203/rs.3.rs-9273730/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9273730/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eOrganophosphorus pesticides (OPs) are extensively used for pest control in crops, yet their residues pose potential threats to food safety and human health. Therefore, this study developed a dual-ligand metal-organic framework with stable red fluorescence as a ratiometric fluorescent sensor for highly sensitive detection of omethoate (OMT). The sensor utilizes Eu\u0026sup3;⁺ as the metal node and employs 3,5-dicarboxyphenylboronic acid (BBDC) and 2-hydroxyterephthalic acid (BDC-OH) as mixed organic ligands. The introduction of OMT significantly quenches the red fluorescence of Eu-BBDC/BDC-OH through the inner filter effect (IFE), enabling the quantitative analysis of OMT. The sensor exhibits a good linear response within the ranges of 0.025\u0026ndash;0.3 \u0026micro;g/mL and 0.3\u0026ndash;0.9 \u0026micro;g/mL, with a detection limit of 7.35 ng/mL, and demonstrates excellent selectivity. Recoveries of OMT from strawberry and cucumber samples ranged from 95.74% to 101.1%, with relative standard deviations of 0.59%\u0026ndash;5.91%, validating the reliability and practicality of the method. Moreover, a paper-based sensor integrated with smartphone RGB analysis was constructed, allowing rapid, real-time, and visual detection of OMT residues.\u003c/p\u003e","manuscriptTitle":"A smartphone-assisted fluorescent sensor using Eu -MOF nanorods for visual and sensitive detection of Organophosphorus pesticides","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-30 16:19:04","doi":"10.21203/rs.3.rs-9273730/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-05-10T14:42:44+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-05T08:45:55+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-28T07:19:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"178947005160718998486062144065168959730","date":"2026-04-23T15:40:14+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-23T14:00:50+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"309756723647958974044102198781018611716","date":"2026-04-21T22:45:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"141945058471011741211463005573165119749","date":"2026-04-21T16:26:21+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"268982275065334129352855185056914138814","date":"2026-04-21T16:16:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"220989781124081313339729155754084506468","date":"2026-04-21T15:41:57+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-21T15:39:10+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-31T09:57:18+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-31T09:56:45+00:00","index":"","fulltext":""},{"type":"submitted","content":"Food Analytical Methods","date":"2026-03-31T03:07:50+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"food-analytical-methods","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Food Analytical Methods](https://www.springer.com/journal/12161)","snPcode":"12161","submissionUrl":"https://submission.nature.com/new-submission/12161/3","title":"Food Analytical Methods","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"e094b735-3c70-4634-ae45-e1af0b195897","owner":[],"postedDate":"April 30th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Revision requested","date":"2026-05-10T14:42:44+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-05T08:45:55+00:00","index":18,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2026-05-10T14:53:55+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-30 16:19:04","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9273730","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9273730","identity":"rs-9273730","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}