Developing an off-on fluorescence sensor based on red copper nanoclusters wrapped by sulfhydryl and polymer double ligands for sensitive detection of N-acetyl-L-cysteine.

N-acetyl-L-cysteine (NAC) as a class of thiols is commonly used in the treatment of lung diseases, detoxification and prevention of liver damage. In this paper, 4-mercaptobenzoic acid (4-MBA) coated and polyvinylpyrrolidone (PVP) attached copper nanoclusters (4-MBA@PVP-CuNCs) were successfully synthesized using a simple one-pot method with an absolute quantum yield of 10.98 %, and its synthetic conditions (like effects of single/double ligands and temperature) were studied intensively. Then Hg2+ could quench the fluorescence of the 4-MBA@PVP-CuNCs and its fluorescence was restored with the addition of NAC. Based on the above principles, an off-on switching system was established to detect NAC. That is, the 4-MBA@PVP-CuNCs-Hg probe was prepared by adding Hg2+ to switch off the fluorescence of the CuNCs by static quenching, and then NAC was added to switch on the fluorescence of the probe based on the chelation of NAC and Hg2+. Moreover, the effects of metal ion types and mercury ion doses for the probe construction were also further discussed. The method showed excellent linearity in the range of 0.05-1.25 µM and low detection limit of 16 nM. Meanwhile, good recoveries in real urine, tablets and pellets were observed, which proved the reliability of the method and provided a convenient, fast and sensitive method for NAC detection.

A sequential dual-locked luminescent copper nanocluster probe for tumor cell imaging and killing.

A sequential dual-locked luminescent copper nanoclusters (CuNCs) probe was designed and synthesized for the specific imaging and selective killing of tumor cells. This nanoprobe was prepared by first forming a Fe3+-coupled tannic acid (TA)-stabilized CuNCs (CuNCs-FeIII), which is in quenching state due to the electron transfer between CuNCs and Fe3+, and then coating a protectable layer of hyaluronic acid (HA) on the surface of CuNCs-FeIII to form the final dual-locked nanoprobe (CuNCs-FeIII@HA). When the nanoprobe of CuNCs-FeIII@HA target enter the tumor cells through CD44-HA receptor, HAase will first digest the HA layer of the nanoprobes, and then, GSH over-expressed in tumor cells will reduce Fe3+ to Fe2+, thus restoring the fluorescence emission of CuNCs and at the same time killing the tumor cells with the hydroxyl free radicals (∙OH) produced by the Fenton reaction between Fe2+ and H2O2. This sequential dual-locked luminescent nanoprobe of CuNCs-FeIII@HA has been successfully used for the specific imaging and selective killing of tumor cells.

Confinement-enhanced electrochemiluminescence of copper nanoclusters on 3D layered double hydroxide for ultrasensitive detection of GFAP.

In this work, the copper nanoclusters (Cu NCs) were confined on 3D layered double hydroxide (3D-LDH) to form Cu NCs@3D-LDH with outstanding electrochemiluminescence (ECL) for constructing ultrasensitive biosensor to detect of glial fibrillary acidic protein (GFAP) implicated in Alzheimer's Disease (AD). More importantly, compared to the individual Cu NCs, Cu NCs@3D-LDH presented strong and stable ECL response, since 3D-LDH could not only gather more Cu NCs but also limit the intramolecular free motion to reduce nonradiative transition for obtaining high ECL intensity. In addition, the improved cascade amplification method combining proximity ligation assay (PLA) with DNAzyme could transform tiny amount of target protein into a large amount of output DNA to improve sensitivity of biosensor. The ECL biosensor realized ultrasensitive detection of GFAP with the detection limit of 2 ag/mL and it had been successfully applied to the evaluation of GFAP in the serum of patients with neurological diseases. This research offered a general and facile method to improve ECL performance of Cu NCs for sensitive detection of biomarkers for disease diagnosis.

In situ synthesis of luminescent dsDNA-Cu NCs stained with a dsDNA-lighted fluorophore for rapid and stable detection of histamine in food.

Poisonous histamine is accumulated in stale meat and fermented foods. The rapid and stable detection of histamine is essential for food safety. Herein, a ratiometric fluorometric method for histamine detection was designed through in situ preparing double-stranded DNA­copper nanoclusters (dsDNA-Cu NCs) stained with 4',6-diamidino-2-phenylindole (DAPI). dsDNA-Cu NCs with red emission were rapidly synthesized via mixing Cu2+, ascorbate and dsDNA at room temperature for 5 min. When DAPI was added during preparation, DAPI coordinated with the Cu element accompanied by the quenched red emission of dsDNA-Cu NCs, and DAPI bound to dsDNA together with the enhanced blue emission of DAPI. Upon adding DAPI and histamine simultaneously, the coordination of histamine with the Cu element further decreased the red emission of dsDNA-Cu NCs, and drove the movement of DAPI from the Cu element to dsDNA along with the enhanced blue emission of DAPI. Significantly, ratiometric fluorescence was insensitive to variations in instrument and environment, causing stable measurement. Meanwhile, in situ synthesis integrated probe preparation with analyte detection, reducing time consumption. Additionally, this method quantified histamine in the concentration range of 7-50 µM with a detection limit of 3.6 µM. It was applied to determining histamine in food with satisfactory accuracy and precision.

Interfacial Hydrogen-Bond Interactions Driven Assembly toward Polychromatic Copper Nanoclusters.

Constructing versatile metal nanoclusters (NCs) assemblies through noncovalent weak interactions between inter-ligands is a long-standing challenge in interfacial chemistry, while compelling interfacial hydrogen-bond-driven metal NCs assemblies remain unexplored so far. Here, the study reports an amination-ligand o-phenylenediamine-coordinated copper NCs (CuNCs), demonstrating the impact of interfacial hydrogen-bonds (IHBs) motifs on the luminescent behaviors of metal NCs as the alteration of protic solvent. Experimental results supported by theoretical calculation unveil that the flexibility of interfacial ligand and the distance of cuprophilic CuI···CuI interaction between intra-/inter-NCs can be tailored by manipulating the cooperation between the diverse IHBs motifs reconstruction, therewith the IHBs-modulated fundamental structure-property relationships are established. Importantly, by utilizing the IHBs-mediated optical polychromatism of aminated CuNCs, portable visualization of humidity sensing test-strips with fast response is successfully manufactured. This work not only provides further insights into exploring the interfacial chemistry of NCs based on inter-ligands hydrogen-bond interactions, but also offers a new opportunity to expand the practical application for optical sensing of metal NCs.

Rapid and sensitive detection of etomidate based on functionalized copper nanoclusters fluorescent probe.

Etomidate as a non-barbiturate sedative, has central inhibitory effect and addiction and has been listed as a controlled drug in some countries due to the abusing trend nowadays. Therefore, rapid and sensitive detection of etomidate is of great significance. In this work, a novel fluorescent sensing probe (CuNCs@MIPs) based on copper nanoclusters (CuNCs) and molecular imprinted polymers (MIPs) has been firstly reported. CuNCs was environment-friendly synthesized using poly(vinylpyrrolidone) as a template and ascorbic acid as a reducing agent. After functionalized with molecular imprinting technique, the CuNCs@MIPs probe has special binding cavities on surface to target etomidate, causing the fluorescence intensity rapidly decrease, which confirmed it has excellent sensitivity, selectivity and stability. Under optimal conditions, the fluorescent sensing probe presented high precision linear relationship for etomidate in range of 10-500 ng/ml with detection limit of 10 ng/ml, and the whole detection process was completed within 10 min. This sensing method has also been applied to real samples detection, still demonstrated excellent feasibility in electronic cigarette liquids and urine. More importantly, compared with previous methods, this fluorescent sensing method has advantages such as rapid, simple and easy to operate. Collectively, the proposed CuNCs@MIPs sensing probe has good fluorescence characteristics and simple synthesis strategy, showed a great potential in etomidate detection and application.

Synthesis of novel phenylalanine-coated copper nanoclusters for fluorescent probes to determine the interactions of cancer drugs with DNA.

Abiraterone acetate (ATA) is an FDA-approved prodrug that exerts its effects by irreversibly inhibiting the enzymatic activities of 17α-hydroxylase and C17,20-lyase, which are responsible for testosterone production, particularly. Drug-DNA interaction studies are conducted using various methods. In this study, CuNCs were used as a fluorescent probe for the first time to investigate drug-DNA interactions. Additionally, a new synthesis was developed for copper nanoclusters coated with phenylalanine (Phe). Ascorbic acid served as the reducing agent, while Phe was used as a surface functionalizing and stabilizing agent. Phe/CuNCs were characterized using various techniques including TEM, DLS, XPS, UV-Vis spectroscopy, and fluorescence spectroscopy. Optimization studies were conducted for synthesis parameters such as ascorbic acid concentration, Phe concentration, incubation time, and incubation temperature. This new synthesis method offers various advantages such as easy synthesis procedure, short synthesis time, and compatibility with green chemistry principles. Phe/CuNCs were used as a fluorescent probe for ATA-DNA interactions. The binding constant (Ka) between ATA and DNA was calculated as 1.03 × 104. Furthermore, thermodynamic studies indicated that the effective forces involved in ATA-DNA interaction are Van der Waals and hydrogen bonding.

An electrochemiluminescent dual-signal immunosensor based on a Ru(bpy)32+-doped silica nanoparticle/copper nanocluster composite for okadaic acid detection.

In this study, a sensitive dual-signal electrochemiluminescence (ECL) immunosensor was developed for okadaic acid (OA) detection utilizing copper nanoclusters (CuNCs) and Ru(bpy)32+-doped silica nanoparticles (RuSiNPs). Interestingly, the CuNCs could simultaneously enhance both cathodic (-0.95 V) and anodic (+1.15 V) ECL signals of RuSiNPs, forming a dual-signal ECL sensing platform. Further, RuSiNPs@CuNCs were used as immunomarkers by covalently conjugating them with an anti-OA monoclonal antibody (mAb) to form probes. Finally, dual ECL signals of the immunosensor were fabricated and showed good linear relationships with OA concentrations in the range of 0.05-70 ng mL-1, having a median inhibitory concentration (IC50) of 1.972 ng mL-1 and a limit of detection of 0.039 ng mL-1. Moreover, the constant ratio of the cathodic and anodic ECL peaks achieved self-calibration of the detection signal and improved the reliability of the results. Finally, we successfully applied the ECL sensor to detect OA in spiked oyster samples.

A facile synthesis of water-soluble copper nanoclusters as label-free fluorescent probes for rapid, selective and sensitive determination of alizarin red.

Copper nanoclusters (FA@CuNCs) emitting blue fluorescence were successfully developed via a one-pot technique. In this method, the copper chloride, folic acid and hydrazine hydrate were applied as a precursor, protective agent and reducing agent, respectively. The absorption, fluorescence excitation and emission spectra of FA@CuNCs were carried out by using ultraviolet-visible and fluorescence spectrometry, respectively. The morphology, particle size, functional groups, oxidation states of elements of FA@CuNCs were discussed via using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The stability of FA@CuNCs was studied under various conditions, such as storage time at 25 ℃, ultraviolet radiation time, sodium chloride solutione and pH. The FA@CuNCs displayed blue fluorescence under the excitation wavelength of 361 nm, and the fluorescence quantum yield was 7.45 %. As a result of the inner filter effect, the alizarin red could significantly weaken the blue fluorescence of FA@CuNCs. Thus, the as-prepared FA@CuNCs could be utilized as fluorescence nanosensors for the trace determination of alizarin red. This platform suggested an excellent linear range for alizarin red varying from 0.5 to 200 µM with a fitting coefficient of 0.9955. The detection limit was calculated to be 0.064 µM in the light of the 3b/k (b and k refer to the standard deviation and slope of fitted curve, respectively). Furthermore, the as-developed FA@CuNCs could be used to detect the alizarin red in real samples and for the sensing of temperature.

Serum albumin-embedding copper nanoclusters inhibit Alzheimer's ß-amyloid fibrillogenesis and neuroinflammation.

Increasing evidence suggests that the accumulations of reactive oxygen species (ROS), ß-amyloid (Aß), and neuroinflammation are crucial pathological hallmarks for the onset of Alzheimer's disease (AD), yet there are few effective treatment strategies. Therefore, design of nanomaterials capable of simultaneously elimination of ROS and inhibition of Aß aggregation and neuroinflammation is urgently needed for AD treatment. Herein, we designed human serum albumin (HSA)-embedded ultrasmall copper nanoclusters (CuNCs@HSA) via an HSA-mediated fabrication strategy. The as-prepared CuNCs@HSA exhibited outstanding multiple enzyme-like properties, including superoxide dismutase (>5000 U/mg), catalase, and glutathione peroxidase activities as well as hydroxyl radicals scavenging ability. Besides, CuNCs@HSA prominently inhibited Aß fibrillization, and its inhibitory potency was 2.5-fold higher than native HSA. Moreover, CuNCs@HSA could significantly increase the viability of Aß-treated cells from 60 % to over 96 % at 40 µg/mL and mitigate Aß-induced oxidative stresses. The secretion of neuroinflammatory cytokines by lipopolysaccharide-induced BV-2 cells, including tumor necrosis factor-α and interleukin-6, was alleviated by CuNCs@HSA. In vivo studies manifested that CuNCs@HSA effectively suppressed the formation of plaques in transgenic C. elegans, reduced ROS levels, and extended C. elegans lifespan by 5 d. This work, using HSA as a template to mediate the fabrication of copper nanoclusters with robust ROS scavenging capability, exhibited promising potentials in inhibiting Aß aggregation and neuroinflammation for AD treatment.

Vibration-Dependent Dual-Phosphorescent Cu4 Nanocluster with Remarkable Piezochromic Behavior.

The dual emission (DE) characteristics of atomically precise copper nanoclusters (Cu NCs) are of significant theoretical and practical interest. Despite this, the underlying mechanism driving DE in Cu NCs remains elusive, primarily due to the complexities of excited state processes. Herein, a novel [Cu4(PPh3)4(C≡C-p-NH2C6H4)3]PF6 (Cu4) NC, shielded by alkynyl and exhibiting DE, was synthesized. Hydrostatic pressure was applied to Cu4, for the first time, to investigate the mechanism of DE. With increasing pressure, the higher-energy emission peak of Cu4 gradually disappeared, leaving the lower-energy emission peak as the dominant emission. Additionally, the Cu4 crystal exhibited notable piezochromism transitioning from cyan to orange. Angle-dispersive synchrotron X-ray diffraction results revealed that the reduced inter-cluster distances under pressure brought the peripheral ligands closer, leading to the formation of new C-H⋅⋅⋅N and N-H⋅⋅⋅N hydrogen bonds in Cu4. It is proposed that these strengthened hydrogen bond interactions limit the ligands' vibration, resulting in the vanishing of the higher-energy peak. In situ high-pressure Raman and vibrationally resolved emission spectra demonstrated that the benzene ring C=C stretching vibration is the structural source of the DE in Cu4.

A highly selective dual-signal response ratiometric fluorescence sensing strategy for malachite green in fish based on carbon dots/copper nanoclusters nanocomposite.

Malachite green (MG), a widely used antiparasitic agent, poses health risks to human due to its genotoxic and carcinogenic properties. Herein, a stable dual-emission fluoroprobe of carbon dots/copper nanoclusters is prepared for highly selective detection of MG based on the inner filter effect. This probe exhibits characteristic emission bands at 435 and 625 nm when excited at 376 nm. After adding MG, the both emission signals were significantly quenched, and the ratio of fluorescence intensity (F435/F625) was linearly related to the concentration of MG in the range of 0.05-40 µmol L-1 with a limit of detection of 18.2 nmol L-1. Meanwhile, the two signals exhibit linear relationships with the concentration of MG, respectively, and the corresponding detection results were consistent. The fluoroprobe was successfully used for the detection of MG in fish samples with the recoveries ranging from 96.0% to 103.8% and a relative standard deviation of <3.3%.

A Novel Enhanced-Fluorescent Probe Based on DHLA-Stabilized Red-Emitting Copper Nanoclusters for Methimazole Detection Via Aggregation-Induced Emission Effect.

Herein, an aqueous phase synthesis approach was presented for the fabrication of copper nanoclusters (Cu NCs) with aggregation-induced emission (AIE) property, utilizing lipoic acid and NaBH4 as ligands and reducing agent, respectively. The as-synthesized Cu NCs exhibit an average size of 3.0 ± 0.2 nm and demonstrate strong solid-state fluorescence upon excitation with UV light. However, when dissolved in water, no observable fluorescent emission is detected in the aqueous solution of Cu NCs. Remarkably, the addition of Methimazole induced a significant red fluorescence from the aqueous solution of Cu NCs. This unexpected phenomenon can be ascribed to the aggregation of negatively charged Cu NCs caused by electrostatic interaction with positively charged imidazole groups in Methimazole, resulting in enhanced fluorescence through AIE mechanism. Therefore, there exists an excellent linear correlation between the fluorescent intensities of Cu NCs aqueous solution and the concentration of Methimazole within a range of 0.1-1.5 mM with a low limit of detection of 82.2 µM. Importantly, the designed enhanced-fluorescent nanoprobe based on Cu NCs exhibits satisfactory performance in assaying commercially available Methimazole tablets, demonstrating its exceptional sensitivity, reliability, and accuracy.

One-Pot facile synthesis of fluorescent copper nanoclusters for highly selective and sensitive detection of tetracycline.

Due to the excellent characteristics, fluorescent copper nanoclusters (Cu NCs) have aroused great interest in recent years. Herein, the simple prepared, environmentally friendly fluorescent Cu NCs were synthesized by using trypsin as the stabilizer and applied for the determination of tetracycline. Uniformly dispersed Try-Cu NCs were obtained with average size of 3.5 ± 0.3 nm and some excellent merits of good water solubility, UV light stability and salt stability. Emission peaks around 460.0 nm were visibly quenched by tetracycline based on static quenching mechanism and inner filter effect (IFE). Two excellent linear relationships were observed between ln(F0/F) and tetracycline concentrations in the range of 1-100 µM and 100-300 µM with limit of detection (LOD) of 0.084 µM. Meanwhile, this nanoprobe exhibited an apparent selectivity for tetracycline detection. Moreover, Try-Cu NCs were successfully employed to determine tetracycline in serum and milk samples after facile pretreatment with satisfactory recovery rates and credible standard deviation. The results suggested that this as-prepared Try-Cu NCs had excellent application prospects in the future.

Copper nanoclusters-doped novel carrier with synergistic adsorption-catalytic active sites to enable high-performance dye removal.

Enhancing the synergistic interplay between adsorption and catalytic oxidation to amplify Fenton-like effects remains a pivotal challenge in advancing water pollution remediation strategies. In this study, a suite of novel carriers (SH) composed of silica (SiO2) and hydroxyapatite (HAp) in different ratios were synthesized through an amalgamation of the sol-gel and co-precipitation techniques. Notably, various forms of copper (Cu) species, including Cu2+ ions and Cu nanoclusters (Cu NCs), could be stably incorporated onto the SH surface via meticulous loading and doping techniques. This approach has engendered a new class of Fenton-like catalysts (Cu NCs-SH1-5) characterized by robust acid-base tolerance stability and remarkable recyclability. Compared with the previously reported Cu NCs-HAp, this catalyst with lower Cu species content could achieve better performance in adsorbing and degrading dyes under the aid of hydrogen peroxide (H2O2). The catalyst's dual action sites, specifically the adsorption sites (SiOH, POH, slit pores) and catalytic centers (multivalent Cu species), had clear division of labor and collaborate with each other. Further, reactive oxygen species (ROS) identification and astute electrochemical testing have unveiled the mechanism underpinning the cooperative degradation of dyes by three types of ROS, spawned through electron transfer between the Fenton-like catalyst (Cu NCs-SH) and H2O2. From these insights, the mechanism of synergistic adsorption-catalytic removal was proposed.

BSA nanoclusters-based sensor for detection of dopamine in schizophrenia from biofluids.

OBJECTIVE: To develop nontoxic and stable fluorescent emission B-Cu nanoclusters (NCs) for the specific detection of dopamine at low concentrations in cerebrospinal fluid (CSF). SIGNIFICANCE: Fluorescent gold and copper NCs conjugated with proteins, such as bovine serum albumin (BSA), offer photostability and healthcare potential. This study focused on fabricating B-Cu NCs that exhibited superior characteristics for sensitive dopamine detection. METHODS: The study employed various instrumental techniques including attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), spectrofluorometry, and transmission electron microscopy (TEM) to characterize the formulated B-Cu NCs. The NCs were synthesized, resulting in particle size ∼300 nm. The highest observed fluorescence was recorded at 24542.81 relative fluorescence units (RFU). RESULTS: The introduction of dopamine at concentrations of 0.1, 0.2, 0.3, and 0.4 ng/mL led to decreased fluorescence in both B-Au and B-Cu NCs due to an electron transport system. This reduction in fluorescence allowed dopamine concentration analysis in phosphate buffer and biological fluids such as blood plasma and CSF. B-Cu NCs showed potential as a biosensing system for point-of-care (POC) applications, specifically for diagnosing schizophrenia. CONCLUSION: The study successfully synthesized stable and nontoxic B-Cu NCs with enhanced fluorescent emission properties. These NCs exhibited the capacity to detect dopamine at low concentrations in CSF. The study's findings hold promise for future applications, particularly in the development of a B-Cu NCs-based biosensing system for convenient POC detection of schizophrenia by both patients and clinicians. The potential impact of this technology on healthcare and biomedical fields is substantial.

Fluorescent sensing platform based on polyethyleneimine-protected copper nanoclusters for detection of chromium(VI) in real samples.

A new type of polyethyleneimine-protected copper nanoclusters (PEI-CuNCs) is favorably developed by a one-pot method under mild conditions. The obtained PEI-CuNCs is characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, Fourier-transform infrared (FTIR) spectroscopy and other techniques. It is worth noting that the proposed PEI-CuNCs demonstrate a selective response to chromium(VI) over other competitive species. Fluorescence quenching of PEI-CuNCs is determined to be chromium(VI) concentrations dependence with a low limit of detection of 8.9 nM. What is more, the as-developed PEI-CuNCs is further employed in building a detection platform for portable recognition of chromium(VI) in real samples with good accuracy. These findings may offer a distinctive strategy for the development of methods for analyzing and monitoring chromium(VI) and expand their application in real sample monitoring.

Cobalt oxyhydroxide nanosheet-modulated ratiometric fluorescence platform for the selective detection of malachite green in fish.

A ratiometric fluorescence platform was developed based on the cobalt oxyhydroxide (CoOOH) nanosheet-modulated fluorescence response of blue emissive copper nanoclusters (Cu NCs) and yellow emissive o-phenylenediamine (OPD). CoOOH nanosheets showed dual function of strong absorption and oxidation ability, which can effectively quench the blue fluorescence of Cu NCs, with an excitation and emission peak maximum at 390 and 450 nm, respectively , and transfer the OPD into yellow fluorescence products, with an excitation and emission peak maximum at 390 and 560 nm, respectively. Upon introducing butyrylcholinesterase (BChE) and its substrates, CoOOH nanosheets were decomposed into Co2+, and malachite green (MG) showed strong inhibition ability to this  process. This resulted in the obvious difference on the ratio of blue and yellow fluorescence recorded on the system in the presence and absence of MG, which was utilized for the quantitative detection of MG, with a limit of detection of 0.140 µM and a coefficient of variation of 3.5%. The fluorescence ratiometric assay showed excellent detection performances in practical sample analysis.

Rapid chemical reduction synthesis of copper nanoclusters with blue fluorescence for highly sensitive detection of furazolidone.

Tannic acid (TA), as a stabilizing agent, was successfully utilized to establish blue-emitting copper nanoclusters (TA-Cu NCs) on the basis of a facile chemical reduction preparation method. Characterization results proved successful synthesis of TA-Cu NCs with uniform size and excellent stability. TA-Cu NCs exhibited a blue emission wavelength at 431 nm when excited at 364 nm. Interestingly, the as-prepared TA-Cu NCs were selectively quenched by furazolidone based on static quenching. In addition, this analysis platform for furazolidone detection had an excellent linear range from 0.5 to 120 µM with a detection limit of 0.074 µM (S/N = 3). Furthermore, the accuracy of this sensing method was successfully confirmed by detecting furazolidone in bovine serum samples, indicating that TA-Cu NCs had bright application prospects.

A Ratio Fluorescence Method Based on Dual Emissive Copper Nanoclusters for the Detection of Vanillin.

In this study, a novel double-emission fluorescence probe at 340 and 400 nm was synthesized by one-pot method using phenylalanine (Phe) and ascorbic acid (AA) as stabilizing and reducing agents. It was found that the fluorescence intensity of the probe at 400 nm could be controlled by controlling the temperature within a certain range, and the ratio of double-emission fluorescence probe could be further regulated. Under the optimal conditions, the fluorescence intensity at 340 nm decreased significantly, while it only showed a slight decrease at 400 nm, which constituted the ratio fluorescence probe. The synthesized fluorescence probe showed good linearity in the range of 0.2-32 µM, and its detection limit was 63.4 nM. Moreover, the method was successfully employed to determine VA in vanilla drink and perfumes, and corresponding results were consistent with those of HPLC.