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Engineering efficient dual-mode portable sensor with built-in cross reference correction is of great significance for onsite reliable and precise detection of organophosphorus pesticides (OPs) and evading the false-positive outputs, especially in emergency case. Currently, most nanozyme-based sensors for OPs monitoring primarily replied on the peroxidase-like activity, which involved unstable and toxic H 2 O 2. In this scenario, a hybrid oxidase-like 2D fluorescence nanozyme (PtPdNPs@g-C 3 N 4) was yielded by in situ growing PtPdNPs in the ultrathin two-dimensional (2D) graphitic carbon nitride (g-C 3 N 4) nanosheet. When acetylcholinesterase (AChE) hydrolyzed acetylthiocholine (ATCh) to thiocholine (TCh), it ablated O 2 −• from the dissolved O 2 catalyzed by PtPdNPs@g-C 3 N 4 's oxidase-like activity, hampering the oxidation of o-phenylenediamine (OPD) into 2,3-diaminophenothiazine (DAP). Consequently, with the increasing concentration of OPs which inhibited the blocking effect by inactivating AChE, the produced DAP caused an apparent color change and a dual-color ratiometric fluorescence change in the response system. Through integrating into a smartphone, a H 2 O 2 -free 2D nanozyme-based onsite colorimetric and fluorescence dual-mode visual imaging sensor for OPs was proposed with acceptable results in real samples, which holds vast promise for further development of commercial point-of-care testing platform in early warning and controlling of OPs pollution for safeguarding environmental health and food safety. [Display omitted] • Oxidase-like 2D fluorescence nanozyme PtPdNPs@g-C 3 N 4 was synthesized by growing in situ PtPdNPs on g-C 3 N 4. • PtPdNPs@g-C 3 N 4 showed the prominent oxide-mimetic activity and excellent fluorescence emission ability. • A H 2 O 2 -free 2D nanozyme-based onsite colorimetric and fluorescence dual-mode sensor was proposed. • This multimodal detection and assessment platform was successfully applied to detect OPs residues in food samples. [ABSTRACT FROM AUTHOR]

• Advances in nanomaterial-based fluorescent sensing of H 2 S in food are summarized. • Sensing performance and application of each sensor are highlighted. • Discussed response strategy of fluorescence analysis for H 2 S detection. • Discussed challenges and future prospects for H 2 S detection in food. As the level of hydrogen sulfide (H 2 S) is one of the most important indicators of food safety, it is necessary to strengthen the monitoring accuracy of H 2 S levels in food production. Fluorescence assays are considered as one of the most promising tools for H 2 S monitoring due to their simplicity, convenience, high accuracy, low cost, and real-time. The rapid progress of fluorescence assays is further promoted by the vigorous development of nanotechnology, and numerous innovative nanotechnology-driven fluorescence assays have been widely used to monitor the H 2 S levels in food-related matrices. To further accelerate the commercialization of point-of-care fluorescence assays for the portable detection of H 2 S in food-related matrices, it is necessary to integrate the available knowledge in innovative nanotechnology-driven fluorescence assays for H 2 S detection. The recent investigations concerning six types (metal-based nanomaterials, metal–organic frameworks, carbon-based nanomaterials, quantum dots-based nanomaterials, silicon-based nanomaterials, and upconversion nanomaterials) of nanomaterials-based fluorescence assays for reporting H 2 S in food-related matrices were summarized, and its inevitable challenges and prospects were discussed. It helps the development of an efficient early-warning and management method to ensure public food safety. [ABSTRACT FROM AUTHOR]

• H 2 S/H+ served as "dual-key" turn on the ratiometric fluorescence of the nanoprobe. • The nanoprobe has superior specificity and sensitivity to H 2 S by H+-powered. • The nanoprobe accurately monitor meat freshness via color and fluorescence changes. • Both TVC and H 2 S-PBC of meat samples correlate with F 688nm /F 818 nm value. Accurate and real-time reporting the freshness and quality of meat has far-reaching implications for safeguarding food safety and public health. Owing to the significant indicator role of H 2 S in meat spoilage, we here designed a "dual-key-and-lock" kind of H+-powered H 2 S-responsive ratiometric fluorescent nanoprobe BODIPY/Cy7Cl@HyNPs for precise and real-time evaluating the meat freshness. After incubation with spoilt meat, BODIPY/Cy7Cl@HyNPs was simultaneously initiated by the abnormal H+ and H 2 S acted as "dual-keys". As a result, the fluorescence emission of BODIPY/Cy7Cl@HyNPs at ∼ 688 nm was enhanced, and the other emission at ∼ 818 nm was quenched, thereby yielding a typical H+-powered ratiometric fluorescence response toward H 2 S in meat. In addition, we also successfully exploited BODIPY/Cy7Cl@HyNPs to achieve the real-time monitoring of the meat freshness during storage by measuring the changes of fluorescence signals and solution color. [ABSTRACT FROM AUTHOR]

Development of accurate and reliable FRET-based assays is of great significance to establish efficient warning-early mechanisms for reporting heavy metal pollution and safeguarding food safety. This review concentrates on the advances of various FRET-based assays toward heavy metals in food and agriculture-related matrices, and profiles the current and future trends, including future commercial point-of-care testing. [Display omitted] • FRET-based assay is a promising technique for monitoring heavy metals to safeguard food safety. • Summarizing the FRET principle in developing efficient assays toward heavy metals for food safety. • Analyzing the progress of FRET-based assays for heavy metals in food and agriculture-related matrices. • Pointing out the challenges and perspectives in FRET-based assays toward heavy metals for food safety. As one of the serious threats to food safety and public health, heavy metal contamination in food and agriculture-related matrices has aroused serious concern for the public and needs to be solved urgently. In this regard, it is important to focus on developing ingenious assays for facile, reliable, efficient, and accurate reporting the residual levels of heavy metals in food and agriculture-related matrices. Recently, with the prosperous progress of fluorescence assays, fluorescence resonance energy transfer (FRET)-based assays have been emerging as one of the most promising analytical tools to recognize and quantify the fouling of heavy metals in food and agriculture-related matrices, which exhibits a simple, rapid, cost-effective, reliable, stable, sensitive, selective, and real-time way. Regarding the vast endeavors that have been contributed in this field up to now, we here summarize the recent advances of FRET-based innovative assays for reporting the contamination of heavy metals (e.g. , Hg, Cu, Pb, Fe, Ag, Cd, Cr, As, U, and their mixture) in complicated food and agriculture-related matrices, point out the unavoidable challenges, and propose the future perspectives. This review might give important insights for developing effective warning-early mechanisms, management strategies, and commercial FRET-based point-of-care assays toward heavy metal contamination in food and agriculture-related matrices, safeguarding food safety and public health. [ABSTRACT FROM AUTHOR]

Development of high-throughput portable smartphone-based onsite visual assays is of great significance to safeguard food safety. This review focuses on a variety of various food contaminants detection based on ratiometric fluorescent signals-driven portable smartphone, and discusses the current and future trends, including future commercialization. [Display omitted] • Smartphone-based ratiometric fluorescent sensors are promising tools in food safety analysis. • Summering the principles in smartphone-based ratiometric fluorescent sensors for food safety. • Profiling the advances in smartphone-based ratiometric fluorescent sensors for food contaminants. • Discussing the challenges and perspectives in smartphone-based ratiometric fluorescent sensors for food safety. Development of efficient and portable biosensor to achieve the accurate onsite detection of food contaminants is of very great significance for safeguarding food safety and human health. With the popularity of smartphone, the digital imaging feature makes it to be an outstanding analytical platform to develop the point-of-care testing sensors. Compared with single-emission fluorescent assay, the ratiometric fluorescent assay possesses the built-in self-calibration function to avoid the interferences caused by various target-independent factors, circumventing/reducing false positive result output, thus improving the detection accuracy and expanding the dynamic detection range in complicated food matrixes. Based on these, vast efforts focus on integrating smartphone with ratiometric fluorescent strategies to develop portable sensors for realizing the onsite visual detection of food contaminants in a rapid, low cost, reliable, and even easy to implement in resource-limited areas way. In this review, we summarize the recent development of ratiometric fluorescent signals-driven smartphone-based sensors for onsite visual detection of food contaminants (e.g. , antibiotics, pesticides, & harmful ions), discuss the confronting challenges, and propose an outlook on the future of this advanced analytical technology to help better achieve the precisely onsite detection of food contaminants, ensuring food safety and human health. [ABSTRACT FROM AUTHOR]

The development of facile, low-cost reliable, and precise onsite assays for the bioactive component hypoxanthine (Hx) in meat products is significant for safeguarding food safety and public health. Herein, we proposed a smartphone-assissted aggregation-induced emission (AIE) fluorogen tetraphenylethene (TPE)-incorporated amorphous Fe-doped phosphotungstates (Fe-Phos@TPE) nanozyme-based ratiometric fluorescence-colorimetric dual-mode biosensor for achieving the onsite visual detection of Hx. When the Hx existed, xanthine oxidase (XOD) catalyzed Hx into H 2 O 2 to be further catalyzed into •OH by the prominent peroxidase activity of Fe-Phos@TPE at pH = 6.5, resulting in the oxidization of nonfluorescent o -phenylenediamine (OPD, naked-eye colorless) to be yellow fluorescent emissive 2,3-diaminophenazine (DAP, naked-eye dark yellow) at 550 nm as well as the intrinsic blue fluorescence of Fe-Phos@TPE at 440 nm to be decreased via inner-filter effect (IFE) action, thereby realizing a multi-enzyme cascade catalytic reaction at near-neutral pH to overcome the traditional acidity dependence-induced time-consuming and low sensitivity troublesome. • Synthesis of AIE fluorescent nanozyme Fe-Phos@TPE with high peroxidase-like activity at neutral pH. • Ratiometric fluorescence-colorimetric dual-mode analysis of bioactive component hypoxanthine. • The smartphone-based biosensor possessed a high sensitivity and fast kinetics. • The biosensor has been applied to the detection of hypoxanthine in meat products. [ABSTRACT FROM AUTHOR]

• Nucleic acid amplification-free biosensors types and characteristics are examined. • Nanomaterial roles in nucleic acid amplification-free biosensors are outlined. • CRISPR/Cas system roles in nucleic acid amplification-free biosensors are discussed. • Nucleic acid amplification-free biosensors challenges and prospects are explored. Accurate, rapid, cost-effective, and point-of-care pathogen identification is crucial for public health safety and encompasses disease prevention, food safety, and environmental governance. Despite the current prevalent detection methods that enable the inspection of various pathogens, certain limitations necessitate resolution. For instance, the plate culture method is time- and labor-intensive. Conversely, antibody- and large-equipment-based detection methods expedite the detection. However, their advancement has been constrained by the availability of antibodies and the inconvenience of deploying large equipment for point-of-care testing (POCT). The development of nucleic acid amplification technology can address the aforementioned issues to a certain extent. However, challenges such as intricate primer design and dependency on thermal cycling persist. Therefore, nucleic acid amplification-free biosensors have garnered significant attention. Biosensors are broadly categorized based on the following tools: nanomaterials-based nucleic acid amplification-free biosensors, clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeat-associated nuclease (CRISPR/Cas)-based nucleic acid amplification-free biosensors, and nucleic acid amplification-free biosensors comprising nanomaterials and CRISPR/Cas. This review not only introduces biosensor performance and CRISPR/Cas applications, but also systematically elucidates the working principles and specific applications of nanomaterials and CRISPR/Cas in optimizing nucleic acid amplification-free detection systems, while judiciously categorizing them based on signal output modalities. Moreover, it discusses the challenges and prospects of nucleic acid amplification-free biosensors and provides valuable insights for further research. [ABSTRACT FROM AUTHOR]

Pesticides are recognized as effective tools for crop protection, but pesticide residues pose a potential threat to human health and ecosystems. When pesticides are present in crops, they can enter the food chain and cause harm to humans and other organisms. Therefore, the monitoring of pesticide levels in relevant matrices is essential to ensure the safety of humans and other organisms. This paper reviews the applications of oxidase-like nanozymes-driven colorimetric, fluorescence and ECL assays for pesticide residues. The mechanisms of fluorescence, colorimetric and ECL assays are also presented. Finally, the advantages and disadvantages of colorimetric, fluorescence and ECL assays and traditional methods in pesticide detection were compared, and their applications in different pesticides detection were validated. This study aims to explore the feasibility and superiority of oxidase-like nanozymes-driven colorimetric, fluorescence and ECL assays for pesticide residues, and to provide an economical, sensitive and accurate detection method for pesticide residue detection. Oxidase-like nanozymes-driven colorimetric, fluorescence and ECL assays can rapidly and accurately detect the presence of pesticides under laboratory conditions with high accuracy and stability. Future research will focus on the development of portable assay equipment based on oxidase-like nanozymes to achieve rapid assay of pesticide residues in the field, which is of great significance in ensuring food safety and thus maintaining the health of humans and other organisms. [Display omitted] • Oxidase-like nanozymes-driven colorimetric, fluorescence and ECL assays for pesticides. • Principles of colorimetric, fluorescence and ECL-based assays for pesticides. • Progress in pesticide residues assays based on oxidase-like nanozyme. • Challenges and perspectives for pesticide assays based on oxidase-like nanozyme. [ABSTRACT FROM AUTHOR]

Microcystins (MCs) is toxic substances that may affect the safety and quality of seafood and aquatic products through water contamination, thus posing a potential threat to both human health and the ecosystem. When MCs exists in water, it can lead to contamination of aquatic plants and animals, which can affect other organisms in the food chain. Therefore, monitoring and controlling the level of MCs in water can ensure that seafood and aquatic products do not contain harmful substances, thereby safeguarding the health and safety of consumers. It also ensures that the quality of aquatic products meets hygiene standards and improves the market competitiveness of the products. This article reviews the application of different fluorescence nanomaterials in the assays of MCs. In addition, the mechanism of fluorescence determination in MCs is introduced, including photoinduced electron transfer (PET), fluorescence resonance energy transfer (FRET), and inner-filter effect (IFE). Finally, we discussed the level of development and limitations of existing fluorescent nanotechnologies and suggested future possibilities in the detection of MCs. Fluorescence methods based on different nanomaterials can rapidly and accurately determine MCs in aqueous solution-related matrices, but the complexity of the environments relevant to the seafood and aquaculture chain limits the practical performance. The future development of multifunctional nanomaterials is needed to achieve a more stable and efficient portable method for the detection of MCs. • Fluorescence detection of MCs based on nanomaterials is a perspective approach. • The fluorescence principles based on nanomaterials for detection of MCs. • The advances in fluorescence detection of MCs based on nanomaterials. • The challenges and prospects based on nanomaterials for detection of MCs. [ABSTRACT FROM AUTHOR]

• PtPd NPs, a mesoporous material with strong oxidase activity, was synthesized. • AIE fluorogen was incorporated into mesoporous material to obtain fluorescent nanozyme PtPd NPs@TPE. • The antioxidative properties of putrescine were used to inhibit the oxidase-like activity of PtPd NPs@TPE. • The smartphone-assisted visual fluorescence sensor for detecting BAs to fight food freshness authenticity. Food safety concerns about the authenticity of soy product freshness have increased due to high demand from public. Developing an accurate and convenient monitoring method for freshness authenticity is crucial for safeguarding food safety. From this motive, this study employed PtPd NPs to encapsulate tetraphenylethylene (TPE) for engineering an AIE-based fluorescent nanozyme (PtPd NPs@TPE) with oxidase-like activity, achieving the ratiometric fluorescence monitoring of putrescine (PUT) to judge the freshness authenticity of soy products. In this design, PUT acted as an antioxidant and inhibited the oxidation process of PtPd NPs@TPE to o -phenylenediamine (OPD), leading to the reduction of oxidative product 2,3-diaminophenothiazine (DAP) alone with the weaken of yellow fluorescence from DAP at 552 nm and bright of bule fluorescence from PtPd NPs@TPE at 442 nm. On this basis, a ratiometric fluorescence strategy integrated with smartphone-based sensor was developed for PUT with acceptable results to combat food freshness fraud of soy products. [ABSTRACT FROM AUTHOR]

• NPs with immense feasibility in manufacturing of ECL platforms for food safety. • The mechanism of NPs triggered signal amplification in ECL biosensors were summarized. • Profiling the mechanism and advances of NPs-driven ECL immunoassay. • Discussing the challenges and perspectives in NPs triggeded ECL immunoassay. Pragmatic testing method is of great significance for food safety control, while the standard detection approach has a series of limitations, such as exhausting procedure, expensive equipment, and professional operation. Real-time supervision of food market urgently needs the assistance of multiple and innovative detection strategies. Electrochemiluminescence (ECL) detection mode is a combination of highly sensitive electrochemical detection and highly specific immunoassay, which has the advantages of low background, fast response, and simple and portable operation. Nevertheless, there are few papers based on the ECL immunoassays for fastly detecting food risks currently by signal amplification. Therefore, the common methods of signal amplification used in this detection mode were further developed in this study on the basis of a deeper understanding of the ECL immunoassay detection principle, and a clarification of their significance and specific applications. Last but not least, it is anticipated to offer insightful reasoning and potential development direction for ECL immunoassays in the detection of food risks. [ABSTRACT FROM AUTHOR]

Food safety is a matter of national health and life safety, and the establishment of scientific and effective detection methods has become an effective means of proper early warning, traceability and management of contaminants in food. This review focuses on Design, preparation, and application of molecularly imprinted nanomaterials for food safety analysis with electrochemistry, and discusses the challenges and future directions of MIPs-EC-based sensors in food safety analysis. [Display omitted] • Nanomaterial-based MIPs-EC sensor for food safety analysis. • Summary the preparation of molecularly imprinted nanomaterials. • Summary on output signal sources of MIPs-EC sensor employed for food safety analysis. • Advancement of nanomaterial-based MIPs-EC sensor for food safety analysis. • Present the challenges and prospects for nanomaterial-based MIPs-EC sensor. Food safety is a matter of national health and life safety, and the establishment of scientific and effective detection methods has become an effective means of proper early warning, traceability and management of contaminants in food, which is one of the most effective ways to ensure food safety. In this context, electrochemical sensors based on novel nanomaterials have unique features such as high sensitivity, fast analysis speed, simple device operation and easy miniaturization, showing great analytical potential compared with other sensors. Molecularly imprinted polymers (MIPs), as sensor recognition elements, have the advantages of simple preparation, low cost and high chemical stability, and have a broad commercial prospect and high practical application value in the field of food safety analysis. Therefore, molecularly imprinted electrochemical (MIPs-EC) sensors using MIPs as recognition elements have received much attention and shown excellent performance. This review explores the recent progress of MIPs-EC sensors in three parts: Principles of molecularly imprinted electrochemical sensor, relevant applications of MIPs-EC-based sensors in food safety analysis, and unavoidable challenges and future perspectives of MIPs-EC. This current and systematically presented review could contribute to the development of novel nanomaterials-based MIPs-EC sensor detection systems, commercial transient detectors, and efficient early warning mechanisms for researchers to monitor and control contaminants in food to ensure food safety and public health. [ABSTRACT FROM AUTHOR]

Pathogenic bacterial infections have become a global concern for safety, and pathogens in food-related matrices can cause a wide range of diseases (e.g. , common cold, asthma, influenza, tuberculosis, anthrax and pneumonia). Therefore, it is necessary to enhance the accuracy of monitoring pathogenic bacteria levels in the food-related matrices. However, traditional detection methods are often complex and time-consuming. With the rapid development of nanotechnology, nanomaterials-based fluorescent assays have been widely used by researchers due to their high fluorescence intensity, stability, low cost, high sensitivity and selectivity. To promote further development in this field, we review here the identification of nanomaterials with pathogenic bacteria based on fluorescent assays and the progress of research on the detection of pathogenic bacteria using functionalized nanoparticles (gold nanomaterials, silver nanomaterials, quantum dots, upconversion nanomaterials, magnetic nanomaterials, carbon nanomaterials and metal-organic frameworks/covalent organic frameworks). Finally, we discuss the shortcomings of fluorescent assays and provide current challenges and prospects for the detection of pathogenic bacteria in food-related matrices. The use of nanomaterials-based fluorescent assays in the detection of pathogenic bacteria has broken the limitations of traditional methods, resulting in much shorter detection time and much higher detection sensitivity. However, detection applications are still at the laboratory stage, and future research should focus on the development of high-throughput detection techniques and portable or visual fluorescent sensors for commercial and industrial applications. We envision that this review will contribute to the development of more sensitive, accurate and convenient nanomaterials-based fluorescent assays for the detection of pathogenic bacteria in food-related matrices for food and public safety. [Display omitted] • Nanomaterials-based fluorescent assays for pathogenic bacteria retained in food-related matrices. • Summary of the principles of the way nanomaterials identifying target pathogenic bacteria. • Analysis of advances in nanomaterials-based fluorescence assays for pathogenic bacteria in food-related matrices. • Presenting challenges and perspectives of nanomaterials-based fluorescent assays for pathogenic bacteria. [ABSTRACT FROM AUTHOR]

• Precise reporting food pollutants is conducive to establish warning mechanism to safeguard food safety. • Nanomaterials-driven ECL aptasensors pose enormous potential in reporting food pollutants. • Sorting out the sensing mechanisms of nanomaterials-driven ECL aptasensors in food analysis. • Dissecting the progress and challenges of nanomaterials-driven ECL aptasensors toward food pollutants. As one of the most concerned issues of public health and food safety, food pollution has attracted great attention. The low-cost, reliable and efficient warning-early of food pollutants has become one of the most alarming challenges but effective strategies for establishing proper management of food pollutants, safeguarding food safety and public health. In this background, the key assurance for supervision is the strong creativity and sustainable progress of monitoring technology. With the progress and development of nanomaterials, photo/electric sensing and nucleic acid aptamer recognition technology, their integration-driven emerging electrochemiluminescence (ECL) aptamer sensing technology has shown the promising potentials in reporting the residual levels of various food pollutants towards practicality, economy, and sensitivity. Especially in recent years, the use of ECL aptamer sensing technology to study the detection and application of food pollutants has been increasing year by year. In order to better boost the advancement of this field, we reviewed the latest progress of nanomaterials-driven ECL aptasensors with nanomaterials as the active elements and aptamers as recognition elements for quantitative detecting the residual food pollutants (e.g. , pesticides, heavy metal ions, toxins, antibiotics, pathogenic bacteria, etc.) in food and agriculture-related matrices in the past 5 years, dissected the inevitable challenges and discussed the future prospects. We anticipated this current and systematically presented review would provide essential insights into the development the nanomaterials-driven ECL aptasensor-driven regulatory systems, commercial instant aptasensors, and validated effective warning-early mechanisms for the detection and control of the residual food pollutants, thereby safeguarding food safety and public health. [ABSTRACT FROM AUTHOR]

Development of efficient point-of-care testing (POCT) toward heavy metals is an effective way to establish warning-early mechanisms against environmental and food safety risks, safeguarding public health. Here, we engineered an intelligent smartphone-based POCT platform for detecting of Fe3+ in environmental and food matrices. We firstly synthesized bovine serum albumin-protected copper nanoclusters (BSA-CuNCs) to assemble [Ru(bpy) 3 ]2+ for obtaining dual-emission BSA-CuNCs@ [Ru(bpy) 3 ]2+ via electrostatic attraction. However, Fe3+ triggered the fluorescence quenching of BSA-CuNCs at 452 nm through aggregation-induced quenching (ACQ) effect, while there was a negligible influence on the emission of [Ru(bpy) 3 ]2+ at 624 nm, obtaining a ratiometric fluorescent responding to Fe3+. By integrating into a smartphone-based gadget, we achieved fluorescence color varies from cyan-blue to red, which were transduced by the Color Picker APP into the RGB values that displayed linear relationship to Fe3+ concentration among 0.0 – 15.0 μM (R 2 = 0.995), with a detection limit of 0.086 μM and a response time within 3.0 min. Notably, this portable platform has been used to gauge Fe3+ in tap water and spirits, whose results agreed with ICP-MS analysis, proving its practicability for onsite determination of Fe3+ in safeguarding environmental and food safety. [Display omitted] • Designing a copper nanoclusters-based ratiometric fluorescent nanoprobe for precisely recognizing Fe3+. • Developing smartphone-based intelligent automatic POCT platform for onsite traceability analysis of Fe3+. • Exhibiting good practicability of smartphone-based POCT platform for Fe3+ in environmental and food analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorescence assay-based AOX-driven in situ synthesis of BSA-CuNCs for CH 3 SH detection. • The assay for CH 3 SH in real ham samples was carried out with acceptable results. • Offering novel insights into applying in situ synthesis strategy to develop sensing platforms. Owing to lack of the effective chromogenic groups, a convenient, precise, and real-time assay for the detection of methyl mercaptan (CH 3 SH) still remains many huge challenges, but it is of great importance to the food and agribusiness related industries. In this work, we proposed an interesting and efficient fluorescence sensing strategy-based alcohol oxidase (AOX)-triggered in situ synthesis of bovine serum albumin-stabilized copper nanoclusters (BSA-CuNCs) for sensitive and selective detection of CH 3 SH. In the presence of CH 3 SH, AOX-assisted O 2 could catalyze it to be H 2 O 2 , which could further trigger BSA-Cu2+ system to in situ synthesize of BSA-CuNCs, emitting fluorescence signals. On this basis, CH 3 SH concentration-dependent fluorescence emission of BSA-CuNCs was observed, thus allowing for developing a novel fluorescence sensing platform for reporting the levels of CH 3 SH with a broad linear range from 1.0 to 300.0 μM and a low detection limit of 0.19 μM. More significantly, we exploited this sensing strategy to monitor CH 3 SH in real ham samples with acceptable results. This work gives a new insight into applying in situ synthesis strategy to develop a new category of fluorescence sensing platform, achieving convenient, low-cost, reliable, and precise measurements in real food and agriculture-related systems, thereby manifesting a promising potential in food safety monitoring. [ABSTRACT FROM AUTHOR]

A novel H 2 S-responsive NIR ratiometric fluorescent nanoprobe based on the fluorescence resonance energy-transfer (FRET) system was designed and applied to accurately detect H 2 S residue level in food samples. • A H 2 S-responsive NIR ratiometric fluorescent nanoprobe-based switchable chromic material was designed. • This nanoprobe has excellent selectivity and sensitivity for H 2 S. • This nanoprobe can detect H 2 S in actual food samples. Food pollution has aroused increasing public health concerns and poses a huge medical and financial burden today. Here, we report a facile one-pot synthesis of hydrogen sulfide (H 2 S)-responsive near-infrared (NIR) ratiometric fluorescent nanoprobe NIR775/Cy7Cl@HyNPs by encapsulating H 2 S-sensitive organic chromic cyanine dye Cy7Cl and H 2 S-inert fluorophore NIR775 into an amphiphilic phospholipid polymer. Because of the confinement effect of phospholipid layer, the loaded NIR775 and Cy7Cl could be brought in close proximity for fluorescence resonance energy transfer (FRET) to occur, leading to single emission of Cy7Cl at ∼ 810 nm inside nanoprobe NIR775/Cy7Cl@HyNPs. However, with the introduction of H 2 S, the FRET process from NIR775 to Cy7Cl is disrupted due to the stimuli-responsive chromic behavior as a result of H 2 S-triggered nucleophilic, leading to restoring of the fluorescence emission of NIR775 at ∼ 778 nm companied by a remarkable fluorescence decrease of Cy7Cl at ∼ 810 nm, thereby enabling nanoprobe NIR775/Cy7Cl@HyNPs to show a NIR ratiometric response toward H 2 S. As expected, the nanoprobe NIR775/Cy7Cl@HyNPs exhibits a prominent practicability to precisely report the levels of H 2 S in actual food mediums with a wide linear range of 0.0367–120.0 μM, a satisfactory limit detection of 11.0 nM, as well as an excellent specificity over other sulfur-containing substances (e.g. biothiols). This study emphasizes the promise for utilizing switchable chromic materials to develop a new category of NIR ratiometric fluorescent nanosensors facilitating accurate and reliable measurement in actual food and agriculture-related systems without any pretreatments, which is of great significance for safeguarding food safety and human health. [ABSTRACT FROM AUTHOR]