Method for quantitatively detecting silver ions based on ratio fluorescent probe of near-infrared dual-emission gold nanocluster and ZIF-8 composite material

Abstract

The invention discloses a near-infrared dual-emission gold nanocluster and ZIF-8 composite material (NIR-GSH-AuNCs (at) beta-CD / ZIF-8) as well as a preparation method and application of the near-infrared dual-emission gold nanocluster and ZIF-8 composite material. The NIR-GSH-AuNCs (at) beta-CD / ZIF-8 is prepared by combining an endogenous near-infrared double-emission gold nanocluster (NIR-GSH-AuNCs (at) beta-CD) modified by sulfydryl-beta-cyclodextrin with the ZIF-8 through confinement packaging, and the endogenous near-infrared double-emission gold nanocluster (NIR-GSH-AuNCs (at) beta-CD / ZIF-8 is prepared by combining with the ZIF-8 through confinement packaging. Dispersion liquid of the composite material is a faint yellow solution under natural light, emits bright yellow fluorescence under irradiation of 365nm ultraviolet light, and shows near-infrared dual-emission fluorescence characteristics at 610nm and 810nm under exciting light of 437nm. The applicant discovers that after the NIR-GSH-AuNCs (at) beta-CD / ZIF-8 is in contact with silver ions, the intensity ratio (F610 / F810) of double emission peaks of the NIR-GSH-AuNCs (at) beta-CD / ZIF-8 regularly responds along with the change of the concentration of the silver ions, so that the ratio type quantitative detection of the silver ions can be realized, and the NIR-GSH-AuNCs (at) beta-CD / ZIF-8 is strong in anti-interference capability and high in sensitivity. When the concentration of silver ions is in a range of 0.02-5 [mu] mol / L, F610 / F810 and log (CAg < + >) are in a linear relationship, a standard curve equation is F610 / F810 = 2.68406. Log (CAg < + >) + 7.14637 (R2 = 0.9961), and the detection limit is as low as 0.0116 [mu] mol / L (S / N = 3). The method can quickly respond without complex pretreatment, and is suitable for accurate analysis of trace silver ions in complex matrixes (such as lake water, tap water and human serum).

Description

Technical Field

[0001] The present invention relates to the field of biological detection technology, and in particular to a method for quantitatively detecting silver ions using a ratiometric fluorescent probe based on metal organic framework (MOFs) encapsulated near-infrared dual-emission gold nanoclusters. Background Art

[0002] Silver ions (Ag + ) is a broad-spectrum antimicrobial agent widely used in medical, cosmetic and industrial fields, but its excessive accumulation will cause serious harm to the ecological environment and human health. Studies have shown that Ag + It can inhibit enzyme activity by binding to protein sulfhydryl groups, induce DNA damage and oxidative stress response, and lead to dysfunction of the nervous and immune systems. Therefore, it is necessary to develop highly sensitive and selective Ag + Detection technology is of great significance to environmental pollution monitoring and clinical diagnosis.

[0003] Currently, Ag + Conventional detection methods include inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectroscopy (AAS), etc., but these technologies rely on large instruments, are complex to operate and expensive, making it difficult to achieve rapid on-site detection. Fluorescence analysis has shown significant advantages in the field of analytical detection due to its high sensitivity and rapid response characteristics. Among them, gold nanoclusters (AuNCs) as a new type of fluorescent probe material have attracted much attention due to their ultra-small size and adjustable luminescence properties, but traditional single-emission AuNCs probes have inherent defects such as low quantum yield, high environmental sensitivity and insufficient photostability. In recent years, metal-organic framework materials with high specific surface area and confinement effect (such as ZIF-8) have provided new ideas for improving the performance of nanomaterials, and their pore structure can effectively enhance the stability and luminescence efficiency of fluorescent probes. However, existing studies have not yet achieved the synergistic regulation of near-infrared dual-emission AuNCs and MOFs confinement effect, resulting in the lack of specific surface area and confinement effect for Ag. + The ratiometric fluorescence detection system still faces technical bottlenecks such as weak anti-interference ability and high detection limit. Therefore, it is necessary to construct a ratiometric fluorescence probe based on the composite structure of near-infrared dual-emission AuNCs and MOFs to achieve Ag + The high stability, high selectivity detection and ultra-low concentration precise analysis of the product have important research value.

[0004] Patent publication number CN 105675556A discloses a method for detecting silver ions using glutathione-protected aggregation-induced emission (AIE) gold nanoclusters as fluorescent probes. This fluorescent reagent is prepared by reacting a chloroauric acid solution with a glutathione solution under mild conditions, followed by purification by dialysis. The resulting gold nanoclusters exhibit AIE properties and do not require additional fluorescent dye modification. This method utilizes the specific interaction between silver ions and the glutathione-protected gold nanoclusters to quantitatively analyze silver ions by detecting the enhanced fluorescence intensity of the gold nanoclusters at 630 nm.

[0005] The above reagent is based on glutathione-protected aggregation-induced emission gold nanoclusters, and its detection mechanism relies on the fluorescence intensity enhancement signal of a single emission wavelength (630nm). Although this method does not require additional fluorescent dye modification, its single emission mode is susceptible to probe concentration fluctuations, light source stability and matrix background interference, which may lead to reduced repeatability of the detection results. In addition, the reagent needs to react under specific acidic conditions (pH = 5) and has strict requirements on buffer preparation, which increases the complexity of the experimental operation. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a ratiometric fluorescent probe based on near-infrared dual-emission gold nanoclusters and ZIF-8 composite materials. Through the confinement effect of metal organic frameworks (MOFs) and the near-infrared dual-emission self-calibration mechanism, the defects of poor fluorescence stability and weak anti-interference ability of single-emission probes are overcome, while significantly enhancing the fluorescence intensity, thereby realizing high-sensitivity and high-stability quantitative detection of silver ions.

[0007] The near-infrared dual-emission gold nanocluster and ZIF-8 composite material described in the present invention (abbreviated as NIR-GSH-AuNCs@β-CD / ZIF-8 or composite fluorescent probe in this application) is prepared by combining near-infrared gold nanocluster modified with thiol-β-cyclodextrin (abbreviated as NIR-GSH-AuNCs@β-CD in this application) and metal organic framework material ZIF-8 through confined encapsulation. The composite fluorescent probe is a dispersion liquid with dimethyl sulfoxide (DMSO) as a solvent. It appears as a light yellow solution under natural light and emits bright yellow fluorescence under 365nm ultraviolet light. Under 437nm excitation light, it exhibits near-infrared dual-emission fluorescence characteristics at 610nm and 810nm, and the dual-emission peak intensity ratio (F 610 / F 810 ) can respond regularly with changes in silver ion concentration.

[0008] The morphology of the near-infrared dual-emission gold nanoclusters and ZIF-8 composite material described in the present invention was characterized by transmission electron microscopy (TEM). It was found that the NIR-GSH-AuNCs@β-CD / ZIF-8 was a rhombic tetrahedron with an average particle size of 133±0.3nm. The NIR-GSH-AuNCs@β-CD particles were wrapped or attached to the surface of ZIF-8, showing obvious aggregation.

[0009] The method for preparing the near-infrared dual-emission gold nanoclusters and ZIF-8 composite material of the present invention comprises the following steps:

[0010] (1) Add chloroauric acid or chloroaurate to a glutathione (GSH) solution, heat and stir in the dark, and then centrifuge to remove insoluble matter. Place the solution in a dialysis bag and dialyze to remove excess reactants to obtain glutathione-reduced near-infrared dual-emission gold nanoclusters (also referred to as NIR-GSH-AuNCs in this application). Freeze-dry the solution and store at 4°C for later use.

[0011] (2) Add thiol-β-cyclodextrin powder (SH-β-CD) to the NIR-GSH-AuNCs solution and stir thoroughly to obtain an assembly of thiol-β-cyclodextrin and glutathione gold nanoclusters (also referred to as NIR-GSH-AuNCs@β-CD in this application). Compared with NIR-GSH-AuNCs, the fluorescence intensity of the NIR-GSH-AuNCs@β-CD assembly at both the 610 nm and 810 nm emission peaks is enhanced under 437 nm excitation.

[0012] (3) Dimethylimidazole (2-MI) and zinc nitrate hexahydrate (Zn(NO3)2·6H2O) were dissolved in methanol respectively and added to the NIR-GSH-AuNCs@β-CD solution. The solution was heated and stirred thoroughly, and then dispersed in DMSO solution after centrifugation and washing to obtain NIR-GSH-AuNCs@β-CD / ZIF-8.

[0013] In the above preparation method, the chloroauric acid is tetrachloroauric acid trihydrate, and the chloroaurate can be one or a combination of two or more selected from sodium chloroaurate, potassium chloroaurate, potassium tetranitrate alloy and sodium tetranitrate alloy.

[0014] In the above preparation method, chloroauric acid or chloroaurate and glutathione can be dissolved in water respectively and then mixed together. The molar ratio of glutathione to chloroauric acid or chloroaurate is preferably 0.75 to 0.95:1, more preferably 0.80 to 0.90:1, and most preferably 0.85:1.

[0015] In the above preparation method, to achieve higher fluorescence intensity in the obtained NIR-GSH-AuNCs, the reaction is preferably carried out at 80-100°C, more preferably 90-100°C, and most preferably 90°C. The reaction time is preferably 70-100 minutes, more preferably 90-100 minutes, and most preferably 90 minutes. The applicant's experiments have shown that within a certain time range, the peak emission intensity of the NIR-GSH-AuNCs at 810 nm increases with increasing reaction time, reaching a maximum intensity at a reaction time of 90 minutes. Therefore, a reaction time of 90 minutes is preferred in this application.

[0016] In the above preparation method, in order to obtain NIR-GSH-AuNCs@β-CD with higher fluorescence intensity, the concentration of NIR-GSH-AuNCs solution is preferably 3.85 mmol / L, and the volume is preferably 20 mL. The amount of thiol-β-cyclodextrin added is preferably 0.3-0.7 mmol / L, more preferably 0.4-0.6 mmol / L, and most preferably 0.5 mmol / L, based on the final concentration. The applicant's experiments have shown that within a certain concentration range, the emission peak intensity of NIR-GSH-AuNCs@β-CD at 810 nm increases with increasing SH-β-CD concentration. When the SH-β-CD concentration is 0.5 mmol / L, the intensity reaches its maximum. Therefore, the preferred final reaction concentration of SH-β-CD in this application is 0.5 mmol / L.

[0017] In the above preparation method, dimethylimidazole (2-MI) and zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) are dissolved in methanol to prepare 0.4 mol / L and 0.1 mol / L mother liquors, respectively. The mixture is stirred thoroughly until completely dissolved before mixing. The molar ratio of dimethylimidazole to zinc nitrate hexahydrate is preferably 3:1 to 5:1, more preferably 4:1.

[0018] Furthermore, the method for preparing glutathione-reduced near-infrared dual-emitting gold nanoclusters described herein further includes purifying the resulting NIR-GSH-AuNCs aqueous solution. Specifically, the NIR-GSH-AuNCs aqueous solution is dialyzed, followed by freeze-drying the dialyzate to obtain solid NIR-GSH-AuNCs. The dialysis is preferably performed using a dialysis bag with a molecular weight cutoff of 1000 Da.

[0019] The applicant found in the experiment that after the NIR-GSH-AuNCs@β-CD / ZIF-8 of the present invention came into contact with the silver ion solution, the fluorescence of NIR-GSH-AuNCs@β-CD / ZIF-8 was enhanced, which was specifically manifested in that the absorption peak intensity at 610nm was greatly enhanced and the absorption peak intensity at 810nm was slightly weakened. Based on the ratio of the two absorption peak intensities (F610 / F 810 ), a quantitative detection method for silver ions can be established. Therefore, the present invention also includes the use of the above-mentioned NIR-GSH-AuNCs@β-CD / ZIF-8 in measuring the content of silver ions.

[0020] Compared with the prior art, the present invention provides a ratiometric fluorescent probe based on near-infrared dual-emission gold nanoclusters and ZIF-8 composite materials and its preparation method. The probe exhibits near-infrared dual-emission fluorescence characteristics at 610nm and 810nm under 437nm excitation light, and when exposed to silver ions (Ag + ), the double emission peak intensity ratio (F 610 / F 810 ) changes regularly, which can realize the ratio-type quantitative detection of silver ions. This method has strong anti-interference ability and high sensitivity. The silver ion concentration (C Ag+ ) is in the range of 0.02 to 5 μmol / L, F 610 / F 810 It is linearly related to log(C), and the fitting equation is F 610 / F 810 =2.68406*log(C Ag+ )+7.14637(R 2＝ 0.9961), with a detection limit as low as 0.0116 μmol / L (S / N=3), which is suitable for the precise analysis of trace silver ions in complex matrices (such as serum and lake water). BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the method for preparing NIR-GSH-AuNCs@β-CD / ZIF-8 solution.

[0022] Figure 2 TEM characterization images, UV-visible absorption spectra and fluorescence spectra of NIR-GSH-AuNCs, NIR-GSH-AuNCs@β-CD and NIR-GSH-AuNCs@β-CD / ZIF-8, where Figure 2 a is the TEM image of NIR-GSH-AuNCs, Figure 2 b is the TEM image of NIR-GSH-AuNCs@β-CD / ZIF-8, Figure 2 c is the UV-visible absorption spectra of NIR-GSH-AuNCs, NIR-GSH-AuNCs@β-CD and NIR-GSH-AuNCs@β-CD / ZIF-8. Figure 2 d is the fluorescence spectra of NIR-GSH-AuNCs, NIR-GSH-AuNCs@β-CD and NIR-GSH-AuNCs@β-CD / ZIF-8, with insets Figure 1 NIR-GSH-AuNCs under sunlight, Figure 2 NIR-GSH-AuNCs@β-CD / ZIF-8 under sunlight, Figure 3 NIR-GSH-AuNCs under 365nm UV light, Figure 4 NIR-GSH-AuNCs@β-CD / ZIF-8 under 365nm ultraviolet light.

[0023] Figure 3 Figure 3a shows the FTIR images of GSH, NIR-GSH-AuNCs, ZIF-8 and NIR-GSH-AuNCs@β-CD / ZIF-8. Figure 3 b is the XRD patterns of NIR-GSH-AuNCs and NIR-GSH-AuNCs@β-CD / ZIF-8; Figure 3 c is the XPS graph of NIR-GSH-AuNCs; Figure 3 d is the XPS graph of NIR-GSH-AuNCs@β-CD / ZIF-8; Figure 3 e is the Zeta potential diagram of ZIF-8, NIR-GSH-AuNCs, NIR-GSH-AuNCs@β-CD and NIR-GSH-AuNCs@β-CD / ZIF-8; Figure 3 f is the fluorescence decay curve of NIR-GSH-AuNCs and NIR-GSH-AuNCs@β-CD / ZIF-8.

[0024] Figure 4 The relationship diagram of the effect of preparation conditions on the synthesis of NIR-GSH-AuNCs solution, where Figure 4 a and 4b are the curve and bar graphs showing the effect of the molar ratio of GSH to HAuCl4 on the synthesis of NIR-GSH-AuNCs solution; Figure 4 c and Figure 4 d is the curve graph and bar graph showing the effect of reaction time on the synthesis of NIR-GSH-AuNCs solution; Figure 4 e and 4f are the curve graph and bar graph of the effect of reaction temperature on the solution synthesis of NIR-GSH-AuNCs.

[0025] Figure 5 The relationship diagram of the effect of preparation conditions on the synthesis of NIR-GSH-AuNCs@β-CD and NIR-GSH-AuNCs@β-CD / ZIF-8 solution is shown in Figure 2. Figure 5 a and Figure 5b is a curve graph and a bar graph showing the effect of the final concentration of SH-β-CD on the synthesis of NIR-GSH-AuNCs@β-CD solution; Figure 5 c and Figure 5 d is the curve graph and bar chart showing the effect of the molar ratio of dimethylimidazole to zinc nitrate hexahydrate on the solution synthesis of NIR-GSH-AuNCs@β-CD / ZIF-8.

[0026] Figure 6 The relationship between the reaction conditions and the fluorescence response of NIR-GSH-AuNCs@β-CD / ZIF-8 solution and silver ions (C Ag+ =1 μmol / L), where Figure 6 a is the emission spectrum of different systems (C Ag+ =1 μmol / L) Figure 6 b is a line graph showing the effect of pH on the fluorescence response of NIR-GSH-AuNCs@β-CD / ZIF-8 solution and silver ions; Figure 6 c is a line graph showing the effect of temperature on the fluorescence response of NIR-GSH-AuNCs@β-CD / ZIF-8 solution and silver ions; Figure 6 d is a line graph showing the fluorescence response of NIR-GSH-AuNCs@β-CD / ZIF-8 solution to silver ions versus time.

[0027] Figure 7 This is an analysis diagram of the detection performance of NIR-GSH-AuNCs@β-CD / ZIF-8 solution, where Figure 7 a is different Ag + Fluorescence emission spectra of NIR-GSH-AuNCs@β-CD / ZIF-8 at different concentrations, Figure 7 b is the standard curve of silver ion determination, Figure 7 c Histogram of the effect of interfering substances on the fluorescence response of NIR-GSH-AuNCs@β-CD / ZIF-8 solution to silver ions. Figure 7 d is a bar graph showing the fluorescence stability of NIR-GSH-AuNCs@β-CD / ZIF-8 within 30 days. DETAILED DESCRIPTION

[0028] To better explain the technical solution of the present invention, the present invention is further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical features used in the embodiments may be replaced with other technical features known in the art having equivalent or similar functions or effects without departing from the inventive concept.

[0029] Example 1

[0030] 1. Experimental

[0031] 1.1 Main instruments and reagents

[0032] All reagents used in the experiment were of analytical grade. SH-β-CD was purchased from Shandong Binzhou Zhiyuan Biotechnology Co., Ltd., dimethyl sulfoxide, glutathione, and tetrachloroauric acid trihydrate were purchased from Shanghai Ciyu Chemical Technology Co., Ltd., zinc nitrate hexahydrate was purchased from Xilong Chemical Co., Ltd., and other reagents were purchased from Aladdin Reagent Company. Ultrapure water was used in the experiments.

[0033] The main instruments used for reagent preparation include a heat-collecting magnetic stirrer (Shanghai Lichen); a high-precision constant-temperature water bath; an ultrathin carbon film copper mesh (accelerating voltage 200 kV); a desktop high-speed refrigerated centrifuge; and a freeze dryer. Analytical instruments include a fluorescence spectrophotometer; an ultraviolet spectrophotometer; a nanoparticle size analyzer; a high-resolution transmission electron microscope (HRTEM, accelerating voltage 200 kV); a Fourier transform infrared spectrometer (FTIR); an X-ray photoelectron spectrometer system; an X-ray diffractometer; and a photoluminescence spectrometer.

[0034] Preparation of silver ion stock solution (1.0 M): Weigh 1.699 g of silver nitrate solid, dissolve it in 10 mL of ultrapure water, and then dilute it to different concentrations as needed.

[0035] 1.2 Preparation and purification of NIR-GSH-AuNCs

[0036] NIR-GSH-AuNCs were prepared using a reduction method. The following steps were used: All glassware was washed thoroughly with freshly prepared aqua regia. HAuCl4·4H2O and GSH solutions were prepared separately in ultrapure water. HAuCl4·4H2O (10 mL, 10 mmol / L) was slowly added to the GSH solution (16 mL, 5.3125 mmol / L) at room temperature. The mixture was stirred vigorously for 5 minutes, until the color of the solution changed from yellow to light yellow. The mixture was transferred to a 90°C oil bath and heated in the dark for 1.5 hours with slow stirring. During the reaction, the color of the mixture changed from light yellow to colorless, and finally to straw yellow. After the reaction, the mixture was centrifuged at 6000 rpm for 10 minutes to remove insoluble impurities, resulting in the NIR-GSH-AuNCs solution.

[0037] Purification of NIR-GSH-AuNCs: The NIR-GSH-AuNCs solution was dialyzed in a 1000 Da dialysis bag for 48 h, with distilled water replaced every 4 h. The dialyzed solution was freeze-dried and stored at 4°C.

[0038] 1.3 Preparation of NIR-GSH-AuNCs@β-CD

[0039] At room temperature, 11.5 mg of mercapto-β-cyclodextrin powder (final concentration in the solution was 0.5 mmol / L) was added to a 20 mL, 3.85 mmol / L GSH-AuNCs solution and stirred for 20 minutes to obtain NIR-GSH-AuNCs@β-CD. Under 437 nm excitation, the fluorescence intensity of the assembly was enhanced at both the 610 nm and 810 nm emission peaks.

[0040] 1.3 Preparation of NIR-GSH-AuNCs@β-CD / ZIF-8

[0041] A methanol solution of dimethylimidazole (10.4 mL, 0.4 mol / L) was added to NIR-GSH-AuNCs@β-CD and stirred thoroughly to allow for full reaction. A methanol solution of zinc nitrate hexahydrate (10.4 mL, 0.1 mol / L) was then added and stirred for 5 minutes. The mixture was then placed in a 70°C oil bath and stirred for 10 minutes. After cooling to room temperature, the mixture was centrifuged at 6000 rpm for 10 minutes, the supernatant discarded, and the precipitate washed and added with 20 mL of dimethyl sulfoxide to obtain NIR-GSH-AuNCs@β-CD / ZIF-8, which was then stored at room temperature in the dark.

[0042] 1.4 Determination of silver ions

[0043] 10 μL of silver ion solution of a certain concentration was added to the NIR-GSH-AuNCs@β-CD / ZIF-8 solution and allowed to react for 10 minutes. The silver ions were determined by measuring the emission peak intensities of NIR-GSH-AuNCs@β-CD / ZIF-8 at 610 nm and 810 nm before and after the addition of silver ions under 437 nm excitation light.

[0044] 2. Experimental Results and Discussion

[0045] 2.1 Experimental Principle

[0046] The NIR-GSH-AuNCs@β-CD / ZIF-8 composite fluorescent probe was constructed by a step-by-step method. First, NIR-GSH-AuNCs were synthesized by a hydrothermal method using GSH as a reducing agent and stabilizer, and its emission peaks were located at 610nm and 810nm, respectively. Subsequently, SH-β-CD was introduced as a functional ligand, and the AuNCs surface was modified by Au-S bonds to form a NIR-GSH-AuNCs@β-CD assembly, which initially enhanced the fluorescence intensity. Finally, utilizing the nano-confinement effect of ZIF-8, NIR-GSH-AuNCs@β-CD was encapsulated in a metal-organic framework material to further suppress non-radiative relaxation and significantly improve the dual-emission fluorescence performance to obtain NIR-GSH-AuNCs@β-CD / ZIF-8. Ag+ The detection is based on its specific binding to the cavity of cyclodextrin, which makes the ligand shell rigid and inhibits the rotation and vibration between molecules, resulting in enhanced fluorescence at 610nm and quenching of fluorescence at 810nm, and realizes ratiometric quantitative detection through the bimodal intensity ratio.

[0047] 2.2 Characterization of gold nanoclusters and composite fluorescent probes

[0048] The shape of NIR-GSH-AuNCs solution under natural light and 365nm ultraviolet light is shown in the figure below. Figure 2 c. The NIR-GSH-AuNCs solution is a yellow transparent solution under natural light ( Figure 2 c plug Figure 1 ), and showed dark red fluorescence under 365nm ultraviolet light ( Figure 2 c plug Figure 3 ); The prepared NIR-GSH-AuNCs have good fluorescence properties. The morphology of NIR-GSH-AuNCs was characterized by HRTEM. The results showed that NIR-GSH-AuNCs were spherical particles with a particle size of about 1.41nm and were dispersed ( Figure 2 a).

[0049] The shape of NIR-GSH-AuNCs@β-CD / ZIF-8 solution under natural light and 365nm ultraviolet light is shown in the figure below. Figure 2 c. The NIR-GSH-AuNCs@β-CD / ZIF-8 solution is a yellow solution under natural light ( Figure 2 c plug Figure 2 ), and shows bright yellow fluorescence under 365nm ultraviolet light ( Figure 2 c plug Figure 4 ); The prepared NIR-GSH-AuNCs@β-CD / ZIF-8 has good fluorescence properties. The morphology of NIR-GSH-AuNCs@β-CD / ZIF-8 was characterized by HRTEM. The results showed that NIR-GSH-AuNCs@β-CD / ZIF-8 was a rhombic tetrahedron with a particle size of about 133nm. NIR-GSH-AuNCs@β-CD particles were wrapped or attached to the surface of ZIF-8, showing obvious aggregation phenomenon ( Figure 2 b).

[0050] The UV absorption spectra of NIR-GSH-AuNCs, NIR-GSH-AuNCs@β-CD and NIR-GSH-AuNCs@β-CD / ZIF-8 are shown in Figure 2. Figure 2c. The UV absorption peak of NIR-GSH-AuNCs is single-peaked at 200-300 nm, and there is no UV absorption peak at 300-500 nm, indicating that gold nanoclusters rather than large gold nanoparticles are synthesized. The UV absorption peak of NIR-GSH-AuNCs@β-CD is higher than that of NIR-GSH-AuNCs, and the peak positions are roughly the same, indicating that thiol-β-cyclodextrin has been bound to the gold atoms. Compared with NIR-GSH-AuNCs and NIR-GSH-AuNCs@β-CD, the UV absorption peak of NIR-GSH-AuNCs@β-CD / ZIF-8 is red-shifted, indicating that the size of the composite fluorescent probe increases and induces aggregation.

[0051] The fluorescence spectra of NIR-GSH-AuNCs, NIR-GSH-AuNCs@β-CD and NIR-GSH-AuNCs@β-CD / ZIF-8 are shown in Figure 2. Figure 2 d. Under 437nm excitation, the emission spectra of these three materials exhibit two emission centers located at 610nm and 810nm, respectively. Binding of NIR-GSH-AuNCs to SH-β-CD enhanced the fluorescence intensity of these two emission centers. Subsequent binding to ZIF-8 increased the fluorescence intensity of the composite fluorescent probe at the 610nm emission center by 6.8 times, and at the 810nm emission center by 2.3 times. UV absorption peaks and fluorescence spectra indicate that the binding of NIR-GSH-AuNCs to thiol-β-cyclodextrin and its encapsulation in ZIF-8 enhances fluorescence.

[0052] The Fourier transform infrared spectra of GSH, NIR-GSH-AuNCs, ZIF-8 and NIR-GSH-AuNCs@β-CD / ZIF-8 are shown in Figure 4. Figure 3 As shown in a, it can be seen that GSH is at 2530 cm -1 There is a stretching vibration peak of SH bond at 3427 cm, while this peak disappears in NIR-GSH-AuNCs, indicating that the thiol group (-SH) of GSH binds to the gold core through the Au-S bond to form a stable coordination structure. -1 (OH stretching vibration), 3134cm -1 (NH stretching vibration) and 1634cm -1 The characteristic peak at (C=O vibration absorption peak) is retained, indicating that the hydroxyl, amino and carbonyl functional groups of glutathione are still retained on the surface of the nanocluster. The infrared spectra of ZIF-8 and NIR-GSH-AuNCs@β-CD / ZIF-8 are highly similar, indicating that the introduction of ZIF-8 does not destroy the surface functional groups of the nanocomposite. Among them, 1421cm -1 and 1592cm-1 The peak at 1634 cm is the stretching vibration of the C=N bond, which confirms the integrity of the ZIF-8 skeleton. -1 The retained C=O vibration absorption peak at is derived from AuNCs, indicating that they are successfully encapsulated in the ZIF-8 structure.

[0053] The XRD spectra of NIR-GSH-AuNCs and NIR-GSH-AuNCs@β-CD / ZIF-8 are shown in Figure 2. Figure 3 As shown in b, the characteristic peaks of NIR-GSH-AuNCs at 31.2°, 50.7°, and 65.6° correspond to the (111), (200), and (220) crystal planes of face-centered cubic (fcc) Au, respectively. Comparison of NIR-GSH-AuNCs@β-CD / ZIF-8 with the ZIF-8 standard card shows that the characteristic peaks are basically consistent, indicating that the strong peaks of ZIF-8 are not destroyed after binding with NIR-GSH-AuNCs@β-CD. This indicates that ZIF-8 maintains its own morphology and configuration during the formation of NIR-GSH-AuNCs@β-CD / ZIF-8 crystals, and the structural changes are not significant, which is consistent with the data obtained from the FT-IR image.

[0054] The XPS spectra of NIR-GSH-AuNCs and NIR-GSH-AuNCs@β-CD / ZIF-8 are shown in Figure 2. Figure 3 c and 3d, representing Au 4f at 84.0 eV and 87.8 eV, respectively. 7 / 2 and Au 4f 5 / 2 The absorption peaks of NIR-GSH-AuNCs@β-CD and NIR-GSH-AuNCs@β-CD / ZIF-8 indicate the presence of Au(I) and Au(0). The contents of Au(Ⅰ) in NIR-GSH-AuNCs@β-CD and NIR-GSH-AuNCs@β-CD / ZIF-8 are 55.9% and 56.4%, respectively. The change of Au(I) content is not obvious, indicating that the fluorescence enhancement is caused by the spatial confinement effect of ZIF-8 on the aggregation of NIR-GSH-AuNCs@β-CD. The absorption peaks of Zn 3p orbital at 88.7eV and 91.3eV represent the absorption peaks of Zn 3p orbital at 88.7eV and 91.3eV, respectively. 3 / 2 and Zn3p 1 / 2 , is Zn 2+ Therefore, Au(0), Zn 2+ The existence of demonstrates the successful synthesis of NIR-GSH-AuNCs@β-CD / ZIF-8 nanocomposites.

[0055] The zeta potentials of ZIF-8, NIR-GSH-AuNCs, NIR-GSH-AuNCs@β-CD and NIR-GSH-AuNCs@β-CD / ZIF-8 are shown in Figure 2 Figure 3The synthesized ZIF-8 is positively charged with a zeta potential of 12 mV. NIR-GSH-AuNCs, NIR-GSH-AuNCs@β-CD, and NIR-GSH-AuNCs@β-CD / ZIF-8 are negatively charged at 27 mV, 30 mV, and 20 mV, respectively. The potential changes indicate that NIR-GSH-AuNCs@β-CD binds to ZIF-8 through electrostatic interactions. The absolute value of the zeta potential of NIR-GSH-AuNCs@β-CD / ZIF-8 is higher than that of ZIF-8, indicating that the fluorescent composite probe exhibits high stability and good dispersibility in aqueous solution.

[0056] The fluorescence lifetime decay curves of NIR-GSH-AuNCs and NIR-GSH-AuNCs@β-CD / ZIF-8 are shown in Figure 2. Figure 3 f. The fluorescence lifetime of NIR-GSH-AuNCs@β-CD / ZIF-8 was extended from 9.15 μs to 9.45 μs compared to NIR-GSH-AuNCs. The MOF confinement caused the aggregation of AuNCs, inhibiting the molecular vibration and rotation, thereby improving the efficiency of energy radiation transition.

[0057] 2.3 Fluorescence enhancement of gold nanoclusters and composite fluorescent probes by silver ions

[0058] In order to investigate whether there is interaction between silver ions and gold nanoclusters and composite fluorescent probes, and to compare the degree of interaction, 10 μL of 100 μmol / L silver ion solution was added to 1.0 mL of NIR-GSH-AuNCs, NIR-GSH-AuNCs@β-CD and NIR-GSH-AuNCs@β-CD / ZIF-8 solutions respectively and allowed to react fully. Figure 6 Figure a shows the fluorescence spectra of the three systems before and after the addition of silver ions. Clearly, before the addition of silver ions, the bimodal fluorescence intensity of NIR-GSH-AuNCs@β-CD / ZIF-8 is the highest. After the addition of silver ions, the bimodal changes in NIR-GSH-AuNCs@β-CD / ZIF-8 are also the greatest, manifested by an increase in the absorption peak intensity at 610nm and a decrease in the absorption peak at 810nm. Based on the ratio of the bimodal peaks of NIR-GSH-AuNCs@β-CD / ZIF-8, a method for measuring silver ions can be established, achieving the design goal of the fluorescent probe.

[0059] 2.4 Optimization of NIR-GSH-AuNCs preparation conditions

[0060] 2.4.1 Effect of the molar ratio of GSH to HAuCl4 on the synthesis of NIR-GSH-AuNCs

[0061] Glutathione is a protective agent and reducing agent for gold nanoclusters, and its content directly determines whether NIR-GSH-AuNCs can be synthesized. The effect of the molar ratio of GSH to HAuCl4 from 0.70:1 to 1.00:1 on the fluorescence properties of NIR-GSH-AuNCs was studied. Figure 4 a and Figure 4 As shown in Figure b, when the molar ratio of GSH to HAuCl4 ranges from 0.70:1 to 0.85:1, AuNCs with a predominant emission center at 810 nm are synthesized, and the fluorescence intensity of the 610 nm emission peak increases accordingly. When the molar ratio is greater than 0.85:1, as the GSH content increases, AuNCs with a predominant emission center at 610 nm are synthesized. Adjusting the molar ratio of GSH to HAuCl4 causes the emission center to shift due to the varying coverage of thiol groups in GSH on the Au surface. When the Au surface coverage is low, AuNCs with a predominant emission center at 810 nm are synthesized, while increasing the Au surface coverage leads to AuNCs with a predominant emission center at 610 nm. To obtain AuNCs with a predominant emission center at 810 nm, a GSH to HAuCl4 molar ratio of 0.85:1 was selected.

[0062] 2.4.2 Effect of reaction time on the synthesis of NIR-GSH-AuNCs

[0063] Different reaction times will result in different amounts and aggregation levels of NIR-GSH-AuNCs, thus affecting the fluorescence properties of NIR-GSH-AuNCs. The effects of synthesis times from 50 min to 130 min on the fluorescence properties of NIR-GSH-AuNCs were investigated. Figure 4 c and Figure 4 As shown in Figure d, when the reaction time is less than 90 min, the fluorescence intensity of the emission peaks at 610 nm and 810 nm increases with increasing reaction time, reaching its peak at 90 min. As the reaction time increases, the fluorescence intensity at 610 nm continues to increase, while the fluorescence intensity at 810 nm decreases. The optimal reaction time for the preparation of NIR-GSH-AuNCs is 90 min.

[0064] 2.4.3 Effect of reaction temperature on the synthesis of NIR-GSH-AuNCs

[0065] Reaction temperature is another important condition for the synthesis of NIR-GSH-AuNCs. When the reaction temperature is 70℃, 80℃, 90℃, 100℃, and 110℃, the fluorescence spectra of the NIR-GSH-AuNCs solution are as follows: Figure 4 e and Figure 4As shown in figure f, the fluorescence intensity of the synthesized NIR-GSH-AuNCs is weak at low temperatures. As the temperature increases, the fluorescence intensity at the 610nm emission peak continues to increase, while the fluorescence intensity at 810nm first increases and then decreases. This may be because high temperatures form aggregates of insoluble Au(I)-sulfate complexes, resulting in reduced fluorescence. Therefore, the optimal reaction temperature is 90°C.

[0066] 2.5 Optimization of Preparation Conditions of NIR-GSH-AuNCs@β-CD

[0067] 2.5.1 Effect of SH-β-CD Concentration on the Synthesis of NIR-GSH-AuNCs@β-CD

[0068] This study investigated the effect of SH-β-CD at a final concentration of 0.1 to 0.8 mmol / L on the fluorescence enhancement of NIR-GSH-AuNCs@β-CD. Figure 5 a and Figure 5 As shown in Figure b, with increasing SH-β-CD final concentration, the fluorescence intensity of the 610 nm emission peak continuously increases, while the fluorescence intensity of the 810 nm emission peak first increases and then decreases. At an SH-β-CD concentration of 0.5 mM, the fluorescence of both emission peaks increases, with the highest increase at 810 nm. SH-β-CD binds to the Au core via the -SH group, and at low SH-β-CD concentrations, it enhances the fluorescence of both emission peaks. As the SH-β-CD concentration increases, the fluorescence of the 610 nm emission peak increases, while the fluorescence of the 810 nm emission peak decreases. This is likely due to the fact that the addition of SH-β-CD alters the GSH coverage on Au, converting low GSH coverage to high GSH coverage. Therefore, the optimal SH-β-CD concentration was selected as 0.5 mmol / L.

[0069] 2.6 Optimization of Preparation Conditions of NIR-GSH-AuNCs@β-CD / ZIF-8

[0070] 2.6.1 2-MI and Zn 2+ Effect of the molar ratio of GSH and AuNCs on the synthesis of NIR-GSH-AuNCs@β-CD / ZIF-8

[0071] The ratio of metal ions and organic ligands plays a decisive role in the structure and properties of ZIF-8. 2+ The effect of the molar ratio of NIR-GSH-AuNCs@β-CD / ZIF-8 on the synthesis of Figure 5 c and Figure 5 d. When 2-MI and Zn 2+When the molar ratio is 4:1, the double emission peak fluorescence of NIR-GSH-AuNCs@β-CD is enhanced to the highest level. This may be because excessive organic ligands will increase the crystal defects of ZIF-8, while too little organic ligands will affect the reaction and make the reaction incomplete.

[0072] 2.7 Optimization of fluorescence response conditions of NIR-GSH-AuNCs@β-CD / ZIF-8 and silver ions

[0073] 2.7.1 Effect of pH on the fluorescence response of NIR-GSH-AuNCs@β-CD / ZIF-8 to silver ions

[0074] The pH value of the medium is one of the important parameters that affect the performance of the fluorescence sensing system. A suitable pH value is conducive to improving the sensitivity of detection. In order to explore the effect of pH on the fluorescence response of NIR-GSH-AuNCs@β-CD / ZIF-8 to silver ions, Tris-HCl buffer with different pH values ​​was mixed with NIR-GSH-AuNCs@β-CD / ZIF-8. 10 μL of 100 μmol / L silver ion solution was added to 1 mL of the mixed solution. The fluorescence intensity of the double peak after the reaction of the reagent and silver ions was measured and recorded as F. 610 、F 810 , and calculate F 610 / F 810 , the results are as follows Figure 6 As shown in b. With the increase of pH value, the ZIF-8 structure is more complete and can give full play to the spatial aggregation effect, + The binding provides dense binding sites, thereby increasing the degree of reaction. Under the condition of pH = 8.5, the F 610 / F 810 The maximum value indicates a stronger sensitivity, which means pH=8.5 is the best pH for the reagent to respond to silver ions.

[0075] 2.7.2 Effect of reaction temperature on the fluorescence response of NIR-GSH-AuNCs@β-CD / ZIF-8 to silver ions

[0076] In order to explore the effect of reaction temperature on the fluorescence response of NIR-GSH-AuNCs@β-CD / ZIF-8 to silver ions, the optimal conditions for the response of NIR-GSH-AuNCs@β-CD / ZIF-8 to silver ions were obtained above to explore the effect of temperature. A high-precision constant temperature water bath was used to control the measurement temperature. After the temperature reached the set value, the fluorescence intensity of the double peak before and after the reaction of the reagent with silver ions was measured and recorded as F. 610 、F 810 , and calculate F 610 / F 810 , the results are as follows Figure 6c. As the reaction temperature increases, the fluorescence intensity of the gold nanoclusters decreases, but for the gold nanoclusters and Ag + The response fluorescence ratio did not change significantly with the change of temperature, but only decreased slightly, indicating that the reaction temperature did not have much effect on its response, so the reaction time at room temperature of 25°C was selected.

[0077] 2.7.2 Effect of reaction time on the fluorescence response of NIR-GSH-AuNCs@β-CD / ZIF-8 to silver ions

[0078] In order to develop a rapid detection method and reduce complexity, reaction time is a very critical parameter. Therefore, the effect of the reaction time between NIR-GSH-AuNCs@β-CD / ZIF-8 and silver ions on the fluorescence response was studied. The optimal pH = 8.5 Tris-HCl buffer was mixed with NIR-GSH-AuNCs@β-CD / ZIF-8, and the reaction temperature was set at 25 ° C. The double peak intensity F of the system was measured at different reaction times. 610 、F 810 , and calculate F 610 / F 810 , the results are as follows Figure 6 As shown in d. From the start of the reaction to 10min, F 610 / F 810 The fluorescence intensity gradually increased, and after 10 minutes, it was basically stable, indicating that the composite fluorescent probe and Ag + The reaction reached saturation. The reaction time for subsequent experiments was 10 min.

[0079] 2.8 Fluorescence response performance of NIR-GSH-AuNCs@β-CD / ZIF-8 to silver ions

[0080] 2.8.1 Standard Curve

[0081] In order to establish the quantitative relationship between the fluorescence intensity of NIR-GSH-AuNCs@β-CD / ZIF-8 and the silver ion concentration in the range of 0.01 to 10.00 μmol·L -1 Thirteen silver ion solutions with different concentrations were prepared within the concentration range. 10.0 μL of silver ion solutions with the above concentrations were added dropwise to 1.0 mL of NIR-GSH-AuNCs@β-CD / ZIF-8 solution with pH=8.5. The reaction temperature was 25°C and the reaction time was 10 min. The fluorescence emission spectrum was then measured ( Figure 7 a).

[0082] In Ag + The fluorescence intensity of the composite fluorescent probe at 610 nm increased with the concentration of Ag in the range of 0.01 to 10 μmol / L. +The fluorescence intensity at 810 nm increases with the increase of Ag concentration. + The concentration of F is quenched. 610 / F 810 The value of log(C Ag+ ) shows a good linear relationship, and the fitting equation is F 610 / F 810 =2.68406*log(C Ag+ (μmol / L))+7.14637, correlation coefficient R 2 is 0.9961( Figure 7 b) The limit of detection (LOD) of silver ions was calculated to be 0.0160 μmol / L (S / N=3, n=3). + The relative standard deviation (RSD) of five repeated measurements was 1.43%, indicating that the proposed method has good repeatability.

[0083] 2.8.2 Discussion on the mechanism of fluorescence response of NIR-GSH-AuNCs@β-CD / ZIF-8 to silver ions

[0084] The experimental results of this paper show that silver ions can cause the near-infrared dual emission peaks of NIR-GSH-AuNCs@β-CD / ZIF-8 to change in different trends. The reaction mechanism can be attributed to Ag + The specific binding to the cyclodextrin cavity and the synergistic confinement effect of ZIF-8. The nanocavity structure of the metal organic framework ZIF-8 is Ag + It provides high-density binding sites, and the cavity of SH-β-CD can be enclosed by Ag. + It stiffens the ligand shell, inhibits molecular vibration and rotation, and reduces non-radiative relaxation, thereby significantly enhancing the fluorescence intensity at 610nm. + The introduction of may interfere with the emission center at 810 nm through the surface plasmon resonance effect or energy transfer pathway, resulting in a decrease in the fluorescence intensity at this wavelength.

[0085] Cyclodextrin and Ag + The inclusion of NIR-GSH-AuNCs@β-CD / ZIF-8 is a static process, which can be confirmed from the response time of NIR-GSH-AuNCs@β-CD / ZIF-8 and Ag+. + The response takes 10 minutes, not instantaneous.

[0086] 2.8.3 Effects of different interfering substances NIR-GSH-AuNCs@β-CD / ZIF-8 on the fluorescence response of silver ions

[0087] The actual test samples contain not only silver ions but also other substances. In order to verify the effect of NIR-GSH-AuNCs@β-CD / ZIF-8 on Ag + In order to determine the selectivity of the detection, this study examined the effects of 21 common ions on the response of the fluorescent probe to silver ions. 2+ , Pb 2+ 、Al 3+ 、Fe 2+ 、Fe 3+ Cr 3+ Mg 2+ 、Mn 2+ 、Na + , K + 、Cd 2+ , Ca 2+ 、Cl - , human serum albumin, urea, cysteine, galactose, dopamine, cholesterol, glucose, uric acid and other representative interfering substances were prepared. The reaction temperature was 25°C. Tris-HCl buffer with pH = 8.5 was used to mix NIR-GSH-AuNCs@β-CD / ZIF-8. 1 mL of the reagent was added with 10 μL of 100 μmol / L silver ion solution and an equal volume of interfering substances. After 10 minutes of reaction, the near-infrared double emission peak fluorescence intensity (F 610 and F 810 ), calculate the intensity ratio F 610 / F 810 , with F 610 / F 810 With the vertical axis and different interfering substances as the horizontal axis, a histogram of the effects of different interfering substances on the fluorescence response of NIR-GSH-AuNCs@β-CD / ZIF-8 and silver ions was established. The results are shown in Figure 7 c. The results show that these interfering substances have a great influence on the interaction between NIR-GSH-AuNCs@β-CD / ZIF-8 and Ag. + There is no obvious enhancement in the fluorescence intensity, indicating that the proposed sensor has good selectivity and anti-interference properties.

[0088] At the same time, the fluorescence stability of NIR-GSH-AuNCs@β-CD / ZIF-8 was also studied. The constructed NIR-GSH-AuNCs@β-CD / ZIF-8 was divided into eight samples, seven of which were placed in a refrigerator for 5, 10, 15, 20, 25, and 30 days, respectively. The fluorescence intensity of the composite nanomaterial and its fluorescence intensity ratio were then recorded. The results are shown in Figure 2. Figure 7 As shown in Figure d, the fluorescence intensity decreases with increasing storage time. On the 30th day, the fluorescence intensity changes little, and the fluorescence intensity ratio remains essentially unchanged, indicating that the composite nanomaterial has good stability.

[0089] 2.9 Determination of silver ions in real samples

[0090] 2.9.1 Determination of silver ions in real water samples

[0091] To test the applicability of this method, silver ion concentrations in real water samples were measured. Water samples were collected from a lake at Guilin University of Electronic Technology and from tap water used daily. The lake water was filtered through a 0.22 μm filter membrane, while the tap water was used directly without pretreatment. 10 μL of lake water and tap water were added to 1.0 mL of a NIR-GSH-AuNCs@β-CD / ZIF-8 solution at pH 8.5. The fluorescence intensities were measured, and the fluorescence intensity ratio (F) of the dual emission peaks was calculated. 610 / F 810 , respectively, calculated the concentration and recovery. The results are shown in Table 1. For the six samples, the spiked recoveries ranged from 96.00% to 104.3%, with RSDs ≤ 5.95%, indicating that the method is accurate and applicable in complex environmental water samples.

[0092] Table 1 Determination of silver ions in real water samples (n=3)

[0093]

[0094] 2.9.2 Determination of silver ions in serum samples

[0095] To verify the clinical applicability of the NIR-GSH-AuNCs@β-CD / ZIF-8 probe, the Ag in actual human serum samples was detected. + Serum samples were provided by a local hospital in Guilin and followed the institutional ethical standards. 10 μL of serum was added to 1.0 mL of NIR-GSH-AuNCs@β-CD / ZIF-8 solution at pH 8.5, and its fluorescence intensity was measured. The fluorescence intensity ratio of its dual emission peaks, F, was calculated. 610 / F 810 The concentration and recovery were calculated respectively. The results are shown in Table 2. For the three samples, the spiked recoveries ranged from 94.00% to 101.60%, with RSDs ≤ 4.26%, indicating that the method is also accurate and applicable in serum samples.

[0096] Table 2 Determination of silver ions in human serum samples (n=3)

[0097]

[0098]

[0099] 3. Conclusion

[0100] Using HAuCl4 as a precursor and glutathione as a reducing agent and stabilizer, NIR-GSH-AuNCs with near-infrared dual-emission fluorescence were synthesized by a hydrothermal method. The molar ratio of the reactants, synthesis time, synthesis temperature and the ratio of SH-β-CD to ZIF-8 were optimized to obtain the NIR-GSH-AuNCs@β-CD / ZIF-8 composite probe with the best fluorescence performance. + Specific binding to the cyclodextrin cavity and the nanoconfinement effect of ZIF-8 allows the probe to trigger fluorescence enhancement at 610 nm and fluorescence quenching at 810 nm via ligand-metal charge transfer, enabling dual-wavelength ratiometric detection of silver ions. This method exhibits high sensitivity, a wide linear range, excellent selectivity, and rapid response without the need for complex pretreatment, making it suitable for the determination of low-concentration silver ions. Common coexisting ions do not interfere with silver ion determination, and this method has been applied to the determination of silver ions in actual water samples and serum with positive results.

Claims

1. A method for quantitatively detecting silver ions using a ratiometric fluorescent probe based on a near-infrared dual-emission gold nanoclusters and a ZIF-8 composite material. Synthesized via a one-pot hydrothermal method, these near-infrared gold nanoclusters exhibit intrinsic dual-emission properties. Modification with thiol-β-cyclodextrin ligands and confinement with the metal-organic framework ZIF-8 enhance their near-infrared emission performance. This results in a dual-emission ratiometric composite fluorescent probe for highly sensitive silver ion detection. The composite fluorescent probe, a dispersion containing DMSO as the solvent, exhibits a pale yellow solution under natural light and emits bright yellow fluorescence under 365nm ultraviolet light.

2. The NIR-GSH-AuNCs@β-CD / ZIF-8 according to claim 1, characterized in that: The composite fluorescent probe is a rhombic tetrahedron with an average particle size of 133±0.3nm, and the NIR-GSH-AuNCs@β-CD particles are wrapped or attached to the ZIF-8 surface.

3. The preparation method of NIR-GSH-AuNCs@β-CD / ZIF-8 according to claim 1, characterized in that: The following steps are involved: (1) AuCl2 or AuCl2 salt was mixed with glutathione solution, heated in the dark, and then purified to prepare gold nanoclusters with endogenous near-infrared dual emission (NIR-GSH-AuNCs); (2) Add thiol-β-cyclodextrin (SH-β-CD) to the NIR-GSH-AuNCs solution and stir to form NIR-GSH-AuNCs@β-CD; (3) Methanol solutions of dimethylimidazole and zinc nitrate hexahydrate were added to NIR-GSH-AuNCs@β-CD in sequence. After heating for reaction, the mixture was washed by centrifugation and dispersed in DMSO to obtain NIR-GSH-AuNCs@β-CD / ZIF-8.

4. The preparation method according to claim 3, wherein In step (1), the molar ratio of chloroauric acid or chloroaurate to glutathione is 0.85:1, the reaction temperature is 90° C., and the reaction time is 90 min.

5. The preparation method according to claim 3 or 4, characterized in that: The final concentration of SH-β-CD in step (2) is 0.5 mmol / L.

6. The preparation method according to claim 3 or 4, characterized in that: In step (3), the molar ratio of dimethylimidazole to zinc nitrate hexahydrate is 4:1, the reaction temperature is 70° C., and the reaction time is 10 min.

7. The use of the NIR-GSH-AuNCs@β-CD / ZIF-8 according to claim 1 in the quantitative detection of silver ions, wherein the dual-emission ratiometric probe can significantly enhance the near-infrared weak emission signal by utilizing ligand regulation and confinement effects, thereby achieving high-sensitivity detection of silver ions. Based on the dual emission peak intensity ratio (F 610 / F 810 ) was linearly related to the logarithm of silver ion concentration in the range of 0.02 to 5 μmol / L, and the detection limit was 0.0116 μmol / L (S / N=3).

8. The use according to claim 7, characterized in that: The detection was carried out in a buffer solution of pH=8.5, the reaction time was 10 min, and the reaction temperature was 25°C.

9. The use according to claim 7 or 8, characterized in that: The assay is suitable for the analysis of silver ions in complex matrices, including samples such as lake water, tap water, and human serum.

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