Because ascorbic acid (AA) is one of the basic elements to maintain the normal physiological functions of human body, it is urgent to develop a material that can achieve efficient, rapid and in-situ detection for AA. A new fluorescence organic compound 4\',4\'\'\'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)bis([1,1\'-biphenyl]-4-carboxylic acid) (H2BTBC) based on benzothiadiazole group has been synthesized, which can detect Fe3+ ions by fluorescence turn-off effect with a detection limit of 0.015 μM, as well as recognize linear amines by fluorescence turn-on effect. Moreover, a highly stable Tb(III) metal-organic framework has been solvothermally prepared with H2BTBC, namely {[(CH3)2NH2]2[Tb2(BTBC)4]∙solvents}n (JXUST-39), which can selectively detect AA among biological fluids by fluorescence enhancement effect with a detection limit of 0.077 μM. In addition, the mechanism for JXUST-39 detecting AA is possibly the cooperative effect of absorbance-caused enhancement and charge transfer between JXUST-39 and AA. Moreover, LED lamp beads, fluorescent films and fluorescent detection test paper based on JXUST-39 were prepared to achieve portable detection via fluorescence enhancement effect.

The misuse of tetracyclines in livestock production poses significant health risks. Thus, establishing convenient detection methods to replace complex laboratory tests for food safety is crucial. In this study, a heterostructure Zn-BTC/IRMOF-3 (denoted as ZBI) asynchronous response fluorescence sensor was developed for the qualitative and quantitative detection of tetracyclines in foods. The ZBI solution exhibited blue fluorescence under UV excitation; upon the introduction of tetracyclines, ZBI selectively recognized the tetracycline molecules through electron transfer, π-π stacking, and chelation, resulting in blue fluorescence quenching and green fluorescence enhancement. The ZBI sensor for tetracycline detection achieved recovery rates ranging from 93.91 to 111.91% in food samples, with a detection limit of as low as 0.086 μmol/L. Lastly, a portable sensing device using support vector classifier was constructed for detecting tetracyclines in real-life scenarios. Our findings introduce a new approach for fabricating fluorescence sensors and offer a novel method for detecting tetracyclines.

Diphenylalanine(FF)-Zn self-assembly (FS) confined in covalent organic polymers (FS@COPs) with efficient fluorescence was synthesized for fluorescence sensing of biogenic amines, which was one of the most important indicators for monitoring food freshness. FS@COPs combined excellent biodegradability of self-assembled dipeptide with chemical stability, porosity and targeted site recognition of COPs. With an optimal excitation wavelength of 360 nm and an optimal emission wavelength of 450 nm, FS@COPs could be used as fluorescence probes to rapidly visualize and highly sensitive determination of tryptamine (Try) within 15 min, and the linear range was from 40 to 900 μg L-1 with a detection limit of 63.08 μg kg-1. Importantly, the FS@COPs showed a high fluorescence quantum yield of 11.28%, and good stability, solubility, and selectivity, which could successfully achieve the rapid, accurate and highly sensitive identification of Try. Furthermore, we revealed the mechanism of FS@COPs for fluorescence sensing of targets. The FS@COPs system was applied to the fluorescence sensing of Try in real samples and showed satisfactory accuracy of 93.02%-105.25%.

Antibiotic residues persist in the environment and represent serious health hazards; thus, it is important to develop sensitive and effective detection techniques. This paper presents a bio-inspired way to make water-soluble fluorescent polymer carbon dots (PCDs@PVA) by heating biomass precursors and polyvinyl alcohol (PVA) together. For example, the synthesized PCDs@PVA are very stable with enhanced emission intensity. This property was observed in a wide range of environmental conditions, including those with changing temperatures, pH levels, UV light, and ionic strength. PCDs@PVA detected the antibiotic chlortetracycline (CTCs) with great selectivity against structurally related compounds and a low detection limit of 20 nM, demonstrating outstanding sensitivity and specificity. We confirmed the sensor\'s practical application through real sample analysis, yielding recovery rates of 98%-99% in samples of milk, honey, and river water. The synthesized PCDs@PVA fluorescence sensor was successfully used for CTCs detection in real samples.

A new Europium metal-organic framework (Eu-MOF), namely [Eu(dpa) (H2O)]·0.5(bpy)·4H2O}n (H4dpa = 5-(3,4-dicarboxyphenoxy) isophenic acid, bpy = protonated 4,4\'-bipyridine) was synthesized and structurally characterized by elemental analyses, infrared spectroscopy, and X-ray single-crystal diffraction analyses. Eu-MOF shows a three-dimensional network structure based on EuIII ions and (dpa)4- ligands via µ4: η1, η2, η2, η2 coordination mode. Fluorescence analysis shows that Eu-MOF has excellent fluorescence sensing characteristics, which can efficiently and sensitively detect various pollutants in water: the limit of detection (LOD) of ratiometric fluorescence detection of ANI in water was 42.9 nM, which was better than the single-peak detection limit. In addition, the peak detection limits of Eu-MOF for Flu, ORN and NB were 120 nM, 27 nM and 94 nM, respectively. In addition, XPS, LUMO orbital energy level, fluorescence lifetime, ultraviolet absorption and other principles are used to explore the mechanism of fluorescence quenching. Surprisingly, Eu-MOF not only has excellent anti- counterfeiting ability and stability, can be used as anti-counterfeiting material in life, but also has good selectivity to Flu. Eu-MOF has obvious fluorescence quenching effect on Flu on paper under ultraviolet light, which can be used for rapid in situ imaging test paper of pesticide residues.

Fluorescence sensing of latent fingerprints (LFPs) has gained extensive attention due to its high sensitivity, non-destructive testing, low biotoxicity, ease of operation, and the potential for in situ visualization. However, the realization of in situ visualization of LFPs especially with green emission and rapid speed is still a challenge. Herein, we synthesized an amphibious green-emission AIE-gen TPE-NI-AOH (PLQY = 62%) for instant in situ LFP detecting, which integrates the excellent fluorescence properties of naphthalimide (NI) with a hydrophilic head and the AIE character as well as the donating property of tetraphenylethene (TPE). TPE-NI-AOH in ethanol/water binary solvent was used as an environmentally friendly LFP developer and achieved in situ green-fluorescence visualization of LFPs. The fluorescence signal achieves its 60% saturated intensity in 0.37 s and nearly 100% in 2.50 s, which is an instant process for the naked eye. Moreover, level 3 details and super-resolution images of LFPs could be observed clearly. Besides, the TPE-NI-AOH developer could be stored for at least 6 months, suitable for long-term storage. This instant in situ highlighting method does not require post-processing operations, providing a more convenient, rapid, and efficient detection method of LFPs. This work would inspire the further advancement of fluorescent sensors for fingerprint imaging.

The misuse of antibiotics has caused serious impacts on food safety and human health, making it crucial to develop rapidly and highly sensitive methods for detecting trace nitrofuran antibiotics (NFs). In this study, phosphorus, nitride-doped carbon nanosheets (PN/CNs) were synthesized using a simple hydrothermal method based on graphitic carbon nitride. This prepared material showed excellent water solubility and stable optical properties. A new fluorescence sensing platform based on PN/CNs was constructed for the highly sensitive detection of four NFs. This sensitivity was mainly attributed to the fluorescence resonance energy transfer (FRET) mechanism. The limits of detection for nitrofurazone, nitrofurantoin, furazolidone and furaltadone were determined to be 13.41, 15.24, 16.37 and 19.94 nM, respectively. The high sensitivity and selectivity of PN/CNs for these four NFs were thoroughly evaluated by the Stern-Volmer equation and FRET quenching efficiency. This proposed method exhibited high sensitivity and can be successfully applied to detect NFs in fish.

In this work, a novel and sensitive fluorescence sensing system for alkaline phosphatase (ALP) was constructed using a bifunctional copper metal-organic framework (Cu@MOF) nanozyme, which had excellent oxidase-mimetic activity and fluorescence properties. Owing to the presence of 2-amino-1,4-benzenedicarboxylic acid (1,4-BDC-NH2) ligand, Cu@MOF displays excellent fluorescence performance at 444 nm. Additionally, Cu2+ endows the oxidase-like activity of Cu@MOF, which could trigger p-phenylenediamine (PPD) to be oxidized to a brown product (PPDox) and quench the photoluminescence of Cu@MOF through the inner filtration effect (IFE). As the preferential affinity of ATP for Cu2+, the catalytic activity of Cu@MOF was significantly reduced once ATP was added, thus PPD could not be oxidized and fluorescence was recovered. In the presence of ALP, ATP was hydrolyzed to adenosine and Pi, which allowed Cu@MOF to regain its catalytic activity and continued to catalyze the generation of PPDox. The fluorescence of Cu@MOF was therefore weakened once again. The ALP activity was directly proportional to the degree of decrease in fluorescence intensity. Thus, this novel fluorescence sensing strategy had a linear range of 0.5-60 U/L and the limit of detection was 0.14 U/L. The established sensing method could also be used to for ALP inhibitors screening, and achieved satisfactory results in determining the level of ALP activity in human serum.

Quantitative microRNA (miRNA) detection is crucial for early breast cancer diagnosis and prognosis. However, quick and stable fluorescence sensing for miRNA identification is still challenging. This work developed a novel label-free detection method based on AuNPs etching for quantitatively detecting miRNA-155. A layer of AuNPs was grown on the surface of mesoporous silica nanoparticles (MSN) loaded with Rhodamine 6G (R6G) using seed-mediated growth, followed by probe attachment. In the presence of miRNA-155, the MSN@R6G@AuNP surface loses the protection of the attached probe, rendering AuNPs susceptible to etching by hydrochloric acid. This results in a significant fluorescent signal being released in the free space. The encapsulation with AuNPs effectively reduces signal leakage, while the rapid etching process shortens detection time. This strategy enables sensitive and fast detection with a detection range of 100 fM to 100 nM, a detection limit of 2.18 fM, and a detection time of 30 min. The recovery rate in normal human serum ranges from 99.02 % to 106.34 %. This work presents a simple biosensing strategy with significant potential for application in tumor diagnosis.

A stable crystalline organic porous salt (CPOSs-NXU-1) with 1D apertures has been assembled by the solvothermal method, which shows high-sensitivity \"turn-on\" fluorescence detection and large-capacity adsorption of As(III) ions in water. The detection limits, saturated adsorption capacity, and removal rate of CPOSs-NXU-1 for As(III) ions in an aqueous solution can reach 74.34 nm (5.57 ppb), 451.01 mg g-1, and 99.6%, respectively, at pH = 7 and room temperature. With the aid of XPS, IR, Raman, and DFT theoretical calculations, it is determined that CPOSs-NXU-1 adsorbed As(III) ions in the form of H2AsO3 - and H3AsO3 through hydrogen bonding between the host and guest. The mechanism for fluorescence sensitization of As(III) ions to CPOSs-NXU-1 is mainly to increase the energy level difference between the ground state and excited state investigated by UV-vis absorption spectra, UV-vis diffuse reflectance spectra, and theoretical calculations. By constructing fluorescent CPOSs, an integrated solution has been achieved to treating As(III) contamination in the water that is equipped with detection and removal. These results blaze a promising path for addressing trivalent arsenic contamination in water efficiently, rapidly, and economically.