CN114951683A - Synthesis method of gold nanocluster and detection method of hexavalent chromium ions of gold nanocluster - Google Patents
Synthesis method of gold nanocluster and detection method of hexavalent chromium ions of gold nanocluster Download PDFInfo
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Abstract
The invention provides a synthesis method of gold nanoclusters AuNCs, which comprises the following steps: the preparation method comprises the steps of adding histidine and polylysine into a chloroauric acid solution to obtain a reaction mixed solution; after the mixed solution in the step is stirred by a stirrer, the synthesized solution is filtered by a filter membrane, and the obtained solution is transferred to an ultrafiltration tube and centrifuged by a weapon in a centrifuge to obtain supernatant; and thirdly, freeze-drying the supernatant obtained in the second step to obtain a gold nanocluster AuNCs solid, weighing, and re-dissolving the gold nanocluster AuNCs by phosphate buffer solution PBS to obtain a gold nanocluster AuNCs solution.The method solves the problems of high cost and long time consumption of the prior art for synthesizing the gold nanoclusters AuNCs; the gold nanocluster fluorescent probe constructed by the invention is used for detecting Cr 6+ The method has the advantages of simple and rapid operation, low cost, no need of complex large-scale instruments, strong practicability, and Cr 6+ The rapid detection field of the method has wide application prospect.
Description
Technical Field
The invention belongs to the technical field of nano materials, and particularly relates to a synthesis method of a gold nanocluster and a detection method of hexavalent chromium ions of the gold nanocluster.
Background
With the development of modern industry, chromium and its compounds are used in many industrial processes such as metal processing, electroplating and leather tanning, among which there are even some manufacturers producing edible capsule shells from leather waste. Large amounts of chromium are released into the human living environment through these industrial processes, seriously jeopardizing human life safety. In general, the two main valence states of chromium in nature are Cr 3+ And Cr 6+ Wherein Cr is 3+ Is an essential element in human nutrition, and Cr 6+ Is a highly toxic substance, has nonbiodegradability and carcinogenicity, and can be exposed to low concentration of Cr 6+ May cause hemolysis, renal failure, hepatic failure, etc., leading to the development of cancer. Therefore, establishing an accurate and feasible detection method for hexavalent chromium ions has important significance for environmental monitoring and human health maintenance.
At present, the conventional methods for detecting chromium ions mainly include inductively coupled plasma mass spectrometry (ICP-MS), Ion Chromatography (IC), Atomic Absorption Spectroscopy (AAS), and the like. Although these methods based on large-scale equipment have high sensitivity, excellent accuracy and stability, they have the disadvantages of high detection cost, complex and time-consuming pretreatment process, high operation requirement for technicians, and the like. Wherein, the ICP-MS and AAS methods can only detect the total amount of chromium but cannot detect the total amount of the chromium 6+ Quantification was performed. Therefore, there is still a need to develop a simple, fast and highly sensitive Cr 6+ And (3) a detection method.
With the rapid development of nanotechnology, novel nanomaterials have become hot spots in various research fields due to their special physicochemical properties, wherein gold nanoclusters (AuNCs) have adjustable fluorescence, good hydrophilicity and high biocompatibilityAnd the synthetic route is simple, and the like, and the method is concerned. AuNCs is a special fluorescent nanoparticle, generally consisting of several to several hundred gold atoms, with a size below 3nm, and is a relatively stable molecular-like aggregate. Researchers have successfully used AuNCs as fluorescent probes for Cr by utilizing the physicochemical properties of AuNCs 6+ In the analytical detection of (3). Sun et al (Sun, Zhang)&Jin, Journal of Materials Chemistry C,2013,1(1),138-143.) preparation of 11-mercaptoundecanoic acid modified gold nanoclusters against Cr 3+ Specific response, then Cr with ascorbic acid 6+ Reduction to Cr 3+ Indirectly detecting Cr 6+ . While Zhang et al (Zhang, Liu, Wang, Yun, Li, Liu, et al.2013, Analytica Chimica Acta,770, 140-reservoir 146.) prepared the glutathione-modified gold nanocluster to directly detect hexavalent chromium. Although both studies were sensitive to Cr detection 6+ And Cr 3+ However, EDTA is required to be added to mask Cr in the detection process 3+ And EDTA and Cr 3+ Long complexing time and no effect on Cr 6+ And the rapid detection is realized. Yin et al (Yin, Coonrod, Heck, Lejarza)&Wong,ACS Applied Materials&Interfaces,2019,11(19),17491-17500.) microcapsules of glutathione-modified AuNCs, Shellaaiah et al (Shellaaiah, Simon, Thiumaaivasan, Sun, Ko&Wu, Microchimica Acta,2019,186(12),788.) synthesized cysteamine-modified gold-copper nanoclusters, although these two methods could directly detect Cr 6+ Without being affected by Cr 3+ However, these two fluorescent probes have the disadvantage of complicated and time-consuming synthetic route, which is not suitable for large-scale synthesis in practical application. Looking up related documents, a method for detecting hexavalent chromium ions by using a gold nanocluster fluorescent probe modified by histidine and polylysine is not reported.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a method for modifying gold nanoclusters by using histidine and polylysine, the method is carried out at normal temperature, the synthesis process is simple, and the prepared gold nanoclusters can be used as a fluorescent probe to rapidly and quantitatively detect hexavalent chromium ions directly.
The synthesis method of the gold nanocluster is characterized by comprising the following steps of:
the preparation method comprises the steps of adding histidine and polylysine into a chloroauric acid solution to obtain a reaction mixed solution;
after the mixed solution in the step is stirred by a stirrer, the synthesized solution is filtered by a filter membrane, and the obtained solution is transferred to an ultrafiltration tube and centrifuged in a centrifuge to obtain supernatant;
and thirdly, freeze-drying the supernatant obtained in the second step to obtain a gold nanocluster AuNCs solid, weighing, and re-dissolving the gold nanocluster AuNCs by phosphate buffer solution PBS to obtain a gold nanocluster AuNCs solution.
Preferably, in the step, the histidine is one of D-histidine, L-histidine and DL-histidine, the content of histidine is 0.1 to 5mmol, the content of polylysine is 0.01 to 1mmol, the molecular weight of polylysine is 1000 to 300000, and the content of chloroauric acid is 0.01 to 1 mmol.
Preferably, the stirring speed of the stirrer is 400-1200 rpm, the stirring time is 0.5-3 h, the specification of the filter membrane is 0.22 μm, the molecular weight of the ultrafiltration tube is 3-100 KD, the rotating speed of the centrifuge is 8000-15000 rpm, and the centrifugation time is 10-30 min;
preferably, the pH value of the phosphate buffer solution PBS is 7-9, and the color of the gold nanocluster AuNCs solution is light yellow.
Preferably, the particle size of the gold nanoclusters AuNCs is 1.4-2.5 nm, the excitation wavelength of the gold nanoclusters AuNCs is 370nm, the emission wavelength of the gold nanoclusters AuNCs is 480nm, and the emission wavelength increases with the increase of the excitation wavelength.
The invention also aims to provide the application of the gold nanocluster as a fluorescent probe for hexavalent chromium ion determination, which is characterized by comprising the following specific steps:
preparation of Cr by phosphate buffer solution PBS solution 6+ A standard solution;
the gold nanoclusters AuNCs and Cr 6+ Mixing standard solutions, and measuring a fluorescence emission spectrum intensity graph of the solution with the excitation wavelength of 370nm after reaction;
the third is Cr 6+ Concentration value is abscissa, fluorescence quenching efficiency { QE ═ FL 0 -FL)/FL 0 Is ordinate, in which: FL and FL 0 Respectively representing the presence and absence of Cr 6+ Fluorescence intensity of AuNCs; to obtain Cr with different concentrations 6+ The fluorescence quenching efficiency and Cr of the AuNCs fluorescent probe solution 6+ Establishing a standard curve according to a linear relation graph among the concentrations;
selecting different inorganic interferents, wherein the inorganic interferents comprise Cr 6+ Or does not contain Cr 6+ The fluorescence intensity is obtained according to the detection method in the steps;
fifthly, adding Cr into the pretreated actual sample 6+ To prepare Cr 6+ Adding a sample solution to be detected with standard concentration; according to the steps of the two steps, the fluorescence intensity is obtained through the in-situ detection method, and the Cr in the sample to be detected can be determined by contrasting a standard curve 6+ And calculating the recovery rate and relative standard deviation of the added standard; in order to verify the reliability of the fluorescence method, the common traditional ion chromatography method is also adopted to detect Cr in the actual sample 6+ Concentration, and comparing the result with a fluorescence method.
Preferably, in the first step, the PBS solution has a pH of 7 to 9.
Preferably, the gold nanoclusters AuNCs and Cr 6+ The volume ratio of the standard solution is 1:1, and the reaction time is 1-5 min.
Preferably, the method comprises the following steps of detecting Cr in the gold nanocluster by a fluorescence method 6+ Further comprising: histidine and polylysine are coated around the gold core, so that the gold nanoclusters AuNCs have a plurality of oxygen-containing and nitrogen-containing groups which are combined with Cr 6+ Combining to make gold nanoclusters AuNCs and Cr 6+ Energy resonance transfer is generated, and the gold nanoclusters AuNCs are aggregated, so that the gold nanoclusters AuNCs are subjected to fluorescence quenching; cr pair is realized through the change value of the gold nanocluster AuNCs fluorescence intensity signal 6+ And (4) carrying out quantitative detection.
Preferably, the step fifthly further comprises pretreatment of the object to be tested, and the step of pretreatment of the object to be tested specifically comprises the following steps: agricultural products: grinding 1-10 g of agricultural products into slurry or powder, adding 100mL of phosphate buffer solution PBS (phosphate buffer solution) with the pH value of 7-9, and then carrying out ultrasonic treatment for 30 min; capsule sample preparation: dissolving 1g of capsule shell in 100mL of phosphate buffer solution PBS, heating to dissolve the capsule shell in a pH value of 7-9, and cooling to room temperature; leather sample: cutting 1g of leather into small pieces, dissolving the small pieces in 100mL of phosphate buffer solution PBS (pH 7-9), and then shaking for 3h under nitrogen atmosphere; soil sample: dissolving 1g of soil in 100mL of phosphate buffer solution PBS (pH 7-9), and then carrying out ultrasonic treatment for 30 min; water sample: taking a water sample, boiling, and then cooling to room temperature; all sample solutions were then centrifuged at 13000rpm for 30min, and the resulting supernatant was filtered through a 0.45 μm filter to obtain the actual sample solution after treatment.
Compared with the prior art, the invention has the beneficial effects that:
gold nanoclusters AuNCs prepared by the method are used as fluorescent probes for detecting Cr 6+ The method has simple and rapid operation, good selectivity and high sensitivity, and can reach Cr specified in national standard or pharmacopoeia 6+ A limited level of detection. The hexavalent chromium limit value is regulated to be 0.05mg/L in the sanitary standard GB5749-2022 of the drinking water; the chromium limit value in the grains and products thereof is 1mg/kg and the chromium limit value in the vegetables and products thereof is 0.5mg/kg according to the national standard GB2762-2017 for food safety; the content of chromium in the medicinal capsules and the used gelatin raw materials specified in Chinese pharmacopoeia 2010 edition must not exceed 2 mg/kg; the European Union stipulates in the reach regulation of 5 months in 2015 that the limit value of hexavalent chromium in leather is 3mg/kg, whereas in this method Cr is present 6+ The detection limit of (2) was 7.2. mu.g/L.
The reagents used by the gold nanocluster AuNCs fluorescent probe prepared by the invention are histidine, polylysine and chloroauric acid, have no toxic or side effect, are environment-friendly reagents, and the synthesis method of the probe has the characteristics of simple synthesis, low cost, rapidness and convenience, only needs to react at normal temperature, and does not generate toxic pollutants in the synthesis process.
The detection method is simple and quick to operate, low in cost, free of complex large-scale instruments, high in practicability and applicable to Cr detection 6+ The rapid detection field of the method has wide application prospect.
Drawings
FIG. 1A is a high resolution transmission electron microscope image of gold nanoclusters AuNCs of the present invention; FIG. 1B is a graph of the particle size distribution of AuNCs according to the present invention using a high resolution transmission electron microscope;
FIG. 2 shows that different Cr is added in the present invention 6+ The fluorescence intensity diagram of the gold nanoclusters AuNCs in content;
FIG. 3 shows the fluorescence quenching efficiency and Cr of gold nanoclusters AuNCs of the present invention 6+ A linear relationship graph of the content;
FIG. 4A shows the addition of Cr according to the present invention 6+ High resolution transmission electron microscopy images of the latter gold nanoclusters AuNCs;
FIG. 4B shows the addition of Cr according to the present invention 6+ The grain size distribution diagram of the high-resolution transmission electron microscope of the rear gold nanoclusters AuNCs;
FIG. 5 is a graph showing the selectivity of fluorescence method according to the present invention for adding different metal ions.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings:
[ example 1 ]:
the preparation method of the gold nanoclusters AuNCs comprises the following specific steps:
1mmol of D-histidine and 0.1mmol of polylysine (molecular weight: about 5000) were added to 0.1mmol of chloroauric acid solution, and after stirring for 1 hour at 800rpm on a stirrer, the resulting pale yellow solution was filtered through a 0.22 μm filter, and the resulting solution was centrifuged at 10000rpm for 20min in a 3KD ultrafiltration tube. And finally, freeze-drying the obtained supernatant to obtain a gold nanocluster AuNCs solid, weighing, and re-dissolving the gold nanocluster AuNCs by phosphate buffer solution PBS (pH 7) to obtain a light yellow AuNCs fluorescent probe with the particle size of 1.4-2.5 nm and uniform dispersion, wherein a high-resolution transmission electron microscope image and a particle size distribution diagram of the light yellow AuNCs fluorescent probe are shown in FIG. 1.
[ example 2 ]:
the preparation method of the gold nanoclusters AuNCs comprises the following specific steps:
5mmol of DL-histidine and 1mmol of polylysine (molecular weight: about 5000) were added to a 1mmol of chloroauric acid solution, and after stirring for 3 hours at 1200rpm on a stirrer, the resultant pale yellow solution was filtered through a 0.22 μm filter, and the resulting solution was centrifuged at 15000rpm for 10min in a 3KD ultrafiltration tube. Finally, the obtained supernatant was freeze-dried to obtain a solid gold nanocluster AuNCs, and the gold nanocluster AuNCs were redissolved with PBS (pH 7.5) by weighing to obtain a light yellow gold nanocluster AuNCs fluorescent probe.
[ example 3 ]:
the preparation method of the gold nanoclusters AuNCs comprises the following specific steps:
0.1mmol of L-histidine and 0.01mmol of polylysine (molecular weight: about 5000) were added to a 0.01mmol solution of chloroauric acid, and after stirring for 0.5h at 400rpm on a stirrer, the resulting pale yellow solution was filtered through a 0.22 μm filter, and the resulting solution was centrifuged for 30min at 8000rpm in a 3KD ultrafilter tube. The obtained supernatant was finally freeze-dried to obtain gold nanocluster AuNCs solid, and the AuNCs were redissolved with PBS (pH 8) by weighing to obtain light yellow AuNCs fluorescent probe.
Example 4:
the preparation method of AuNCs comprises the following specific steps:
1mmol of D-histidine and 0.05mmol of polylysine (molecular weight about 30000) were added to a 0.1mmol solution of chloroauric acid, and after stirring for 2 hours at 1200rpm on a stirrer, the resulting pale yellow solution was filtered through a 0.22 μm filter, and the resulting solution was centrifuged at 1200rpm for 15min in a 10KD ultrafiltration tube. The obtained supernatant was finally freeze-dried to obtain AuNCs solid, and the AuNCs was redissolved with PBS (pH 9) by weighing to obtain a pale yellow AuNCs fluorescent probe.
[ example 5 ]:
AuNCs is detecting Cr 6+ In (1)
Cr 6+ Detection of (2)
Preparation of 1g/LCr with ultrapure water 6+ The mother solution was then diluted with PBS (pH 7) solution to obtain Cr of various concentrations 6+ Standard solutions (0.01, 0.04, 0.07, 0.1, 0.4, 0.7, 1, 4, 7, 10, 40, 70, 100 mg/L). Then 200. mu.L of 1mg/mL AuNCs were directly mixed with 200. mu.L Cr 6+ Standard solutionThe fluorescence emission spectrum intensity of the solution at the excitation wavelength of 370nm after mixing and reacting for 2min is shown in FIG. 2. With Cr 6+ Concentration value is abscissa, fluorescence quenching efficiency { QE ═ FL 0 -FL)/FL 0 Is ordinate (where FL and FL 0 Respectively representing the presence and absence of Cr 6+ Fluorescence intensity of AuNCs) to obtain different concentrations of Cr added 6+ The fluorescence quenching efficiency and Cr of the AuNCs fluorescent probe solution 6+ The linear relationship between concentrations is shown in FIG. 3, and QE is 0.0462C Cr 6+ +0.0002(R 2 0.991), the linear range of detection is 10-10000 mug/L, and the detection limit is 7.2 mug/L.
The detection principle is as follows:
referring to FIG. 1, the AuNCs fluorescent probe synthesized from histidine and polylysine was used to detect Cr 6+ . Because histidine and polylysine are coated around the gold core, AuNCs have a plurality of oxygen-containing and nitrogen-containing groups which can be reacted with Cr 6+ Combining AuNCs and Cr 6+ Generating energy resonance transfer, aggregating AuNCs, and adding Cr 6+ The high resolution transmission electron micrograph of the post-AuNCs and the particle size distribution thereof are shown in FIG. 4, thereby causing fluorescence quenching of the AuNCs. Cr pair is realized through the change value of AuNCs fluorescence intensity signal 6+ And (4) carrying out quantitative detection.
Selective experiments:
50mg/L of each of the samples was prepared in PBS (pH 7) without Cr 6+ Or containing 50mg/LCr 6+ Different kinds of inorganic substances (K) 2 Cr 2 O 7 、CrCl 3 、PbCl 2 、CoCl 2 、CdCl 2 、Hg(NO 3 ) 2 、AlCl 3 、FeCl 3 、MnCl 2 、Fe(NH 4 ) 2 (SO 4 ) 2 、BaCl 2 、CaCl 2 、NaCl、MgCl 2 、InCl 3 And GaCl 3 ) As an interfering substance, 200. mu.L of 1mg/mL AuNCs were directly mixed with 200. mu.L of Cr-free AuNCs 6+ Or containing Cr 6+ The inorganic substance solution is mixed, and after reacting for 2min, the fluorescence signal of the solution with the excitation wavelength of 370nm is measured. The obtained AuNCs fluorescence quenching effectThe ratio chart is shown in FIG. 5, in which Cr is added alone 6+ The fluorescence quenching efficiency of AuNCs is far higher than that of the AuNCs without adding Cr 6+ While only the fluorescence quenching efficiency of the other interferents is added. When Cr is added into the system 6+ And when other single interferents are added, the fluorescence quenching efficiency of AuNCs is obviously improved, and the aim of adding Cr independently is achieved 6+ Similar levels. This indicates that other inorganic substances have little interference with the method, indicating that fluorescence based on AuNCs is applied to Cr 6+ Has good selectivity.
Feasibility experiments:
to verify the method, Cr was detected in the actual sample 6+ And (3) performing a standard recovery rate experiment. Chinese cabbage, rice, capsule shells, leather, soil and river water are selected as actual samples, and the samples are firstly subjected to independent pretreatment. The pretreatment of each sample is as follows: chinese cabbage: grinding 10g of celery cabbage into paste, adding 100ml of LPBS (pH 7), and then carrying out ultrasonic treatment for 30 min; rice flour: dissolving 1g of rice flour in 100ml PBS (pH 7), and then performing ultrasonic treatment for 30 min; capsule shell: dissolving 1g of capsule shell in 100ml pbs (pH 7) and heating to dissolve, then cooling to room temperature; leather: 1g of leather was cut into small pieces and dissolved in 100ml pbs (pH 7) and then shaken under nitrogen for 3 h; river water: heating the collected river water to a boiling point, and then cooling to room temperature; soil: 1g of soil was dissolved in 100ml of PBS (pH 7) and then sonicated for 30 min. Then, all the sample solutions were centrifuged at 13000rpm for 30min, and the resulting supernatant was filtered through a 0.45 μm filter to obtain the treated actual sample solutions. Then, adding Cr with different content of 1.0g/L into the actual sample solution 6+ To prepare sample solutions at different spiking concentrations (50, 300 and 3000. mu.g/L). Then 200. mu.L of 1mg/mLAuNCs was directly mixed with 200. mu.L of different Cr 6+ Mixing the concentrated and standard actual sample solutions, reacting for 2min, measuring the fluorescence emission spectrum intensity of the solution with excitation wavelength of 370nm, and obtaining the fluorescence emission spectrum intensity chart according to the standard curve linear equation QE (0.0462C) Cr 6+ +0.0002, Cr calculated by AuNCs fluorescence method can be obtained 6+ Concentrations, and calculating the normalized recovery and relative standard deviation. In addition, in order to verify the reliability of the fluorescence method, a conventional method is also adoptedMethod (ion chromatography) for detecting Cr in actual sample 6+ The results were compared with the fluorescence method, and the results are shown in table 1:
TABLE 1
Based on AuNCs, the recovery rate of the fluorescence method is 84.9-102.9%, and the RSD value is 2.7-5.8%. Compared with the ion chromatography, the fluorescence method has good precision and accuracy, and the fluorescence method based on AuNCs can be used for detecting Cr 6+ Alternative methods of (3).
The above description is only a preferred embodiment of the present invention, and all the equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.
Claims (10)
1. A method for synthesizing gold nanoclusters is characterized by comprising the following steps:
the preparation method comprises the steps of adding histidine and polylysine into a chloroauric acid solution to obtain a reaction mixed solution;
after the mixed solution in the step is stirred in a stirrer, filtering the synthesized solution by using a filter membrane, transferring the obtained solution to an ultrafiltration tube, and centrifuging in a centrifuge to obtain supernatant;
and thirdly, freeze-drying the supernatant obtained in the second step to obtain a gold nanocluster AuNCs solid, weighing, and re-dissolving the gold nanocluster AuNCs by phosphate buffer solution PBS to obtain a gold nanocluster AuNCs solution.
2. The method for synthesizing the gold nanoclusters according to claim 1, characterized in that the histidine is one of D-histidine, L-histidine and DL-histidine, the content of histidine is 0.1-5 mmol, the content of polylysine is 0.01-1 mmol, the molecular weight of polylysine is 1000-300000, and the content of chloroauric acid is 0.01-1 mmol.
3. The method for synthesizing the gold nanoclusters according to claim 1, characterized in that the stirring speed of the stirrer is 400-1200 rpm, the stirring time is 0.5-3 hours, the specification of the filter membrane is 0.22 μm, the molecular weight of the ultrafiltration tube is 3-100 KD, the rotation speed of the centrifuge is 8000-15000 rpm, and the centrifugation time is 10-30 min.
4. The method for synthesizing the gold nanoclusters according to claim 1, wherein the pH of the phosphate buffer solution PBS is 7-9, and the color of the gold nanocluster AuNCs solution is light yellow.
5. The gold nanoclusters prepared by the synthesis method of claim 1, wherein the gold nanoclusters AuNCs have a particle size of 1.4-2.5 nm, an excitation wavelength of 370nm and an emission wavelength of 480nm, and the emission wavelength increases with the increase of the excitation wavelength.
6. The application of the gold nanocluster according to claim 1 as a fluorescent probe for hexavalent chromium ion determination, which is characterized by comprising the following specific steps:
preparation of Cr by phosphate buffer solution PBS solution 6+ A standard solution;
the gold nanoclusters AuNCs and Cr 6+ Mixing standard solutions, and measuring a fluorescence emission spectrum intensity graph of the solution with the excitation wavelength of 370nm after reaction;
the third is Cr 6+ Concentration value is abscissa, fluorescence quenching efficiency { QE ═ FL 0 -FL)/FL 0 Is ordinate, in which: FL and FL 0 Respectively representing the presence and absence of Cr 6+ Fluorescence intensity of AuNCs; to obtain Cr with different concentrations 6+ The fluorescence quenching efficiency and Cr of the AuNCs fluorescent probe solution 6+ Establishing a standard curve according to a linear relation graph among the concentrations;
selecting different inorganic interferents, wherein the inorganic interferents comprise Cr 6+ Or does not contain Cr 6+ The fluorescence intensity is obtained according to the detection method in the steps;
fifthly, adding Cr into the pretreated actual sample 6+ To prepare Cr 6+ Adding a sample solution to be detected with standard concentration; according to the steps, the fluorescence intensity is obtained by the in-situ detection method, and the Cr in the sample to be detected can be determined by contrasting a standard curve 6+ And calculating the recovery rate and relative standard deviation of the added standard; in order to verify the reliability of the fluorescence method, the common traditional ion chromatography method is also adopted to detect Cr in the actual sample 6+ Concentration, and comparing the result with a fluorescence method.
7. The use of the gold nanoclusters of claim 6 as a fluorescent probe for hexavalent chromium ion measurement, wherein the pH of the PBS solution is 7 to 9.
8. The use of the gold nanoclusters of claim 6 as a fluorescent probe for hexavalent chromium ion determination, wherein the gold nanoclusters are AuNCs and Cr 6+ The volume ratio of the standard solution is 1:1, and the reaction time is 1-5 min.
9. The use of the gold nanoclusters of claim 6 as a fluorescent probe for hexavalent chromium ion determination, which is used in the two steps and the three steps, and the gold nanoclusters are used for detecting Cr by a fluorescence method 6+ Further comprising: histidine and polylysine are coated around the gold core, so that the gold nanoclusters AuNCs have a plurality of oxygen-containing and nitrogen-containing groups which are combined with Cr 6+ Combining to make gold nanoclusters AuNCs and Cr 6+ Energy resonance transfer is generated, and the gold nanoclusters AuNCs are aggregated, so that the gold nanoclusters AuNCs are subjected to fluorescence quenching; cr pair is realized through the change value of the gold nanocluster AuNCs fluorescence intensity signal 6+ And (4) carrying out quantitative detection.
10. The use of the gold nanocluster of claim 6 as a fluorescence probe for hexavalent chromium ion determination, characterized in that step fifthly further comprises pretreatment of an object to be tested, and the step of pretreatment of the object to be tested specifically comprises: agricultural products: grinding 1-10 g of agricultural products into slurry or powder, adding 100mL of phosphate buffer solution PBS (phosphate buffer solution) with the pH value of 7-9, and then carrying out ultrasonic treatment for 30 min; capsule sample preparation: dissolving 1g of capsule shell in 100mL of phosphate buffer solution PBS, heating to dissolve the capsule shell in a pH value of 7-9, and cooling to room temperature; leather sample: cutting 1g of leather into small pieces, dissolving the small pieces in 100mL of phosphate buffer solution PBS (pH 7-9), and then shaking for 3 hours under nitrogen atmosphere; soil sample: dissolving 1g of soil in 100mL of phosphate buffer solution PBS (pH 7-9), and then carrying out ultrasonic treatment for 30 min; water sample: taking a water sample, boiling, and then cooling to room temperature; all sample solutions were then centrifuged at 13000rpm for 30min, and the resulting supernatant was filtered through a 0.45 μm filter to obtain the treated actual sample solution.
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