CN111205852B

CN111205852B - Glutathione-protected strong fluorescence-emission gold-platinum alloy nano-cluster and controllable preparation method thereof

Info

Publication number: CN111205852B
Application number: CN202010046615.3A
Authority: CN
Inventors: 吴玉清; 李洪伟; 高延才
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2020-01-16
Filing date: 2020-01-16
Publication date: 2021-07-09
Anticipated expiration: 2040-01-16
Also published as: CN111205852A

Abstract

A glutathione-protected strong fluorescence-emission gold-platinum alloy nano-cluster and a controllable preparation method thereof belong to the technical field of preparation of strong near-infrared luminescent metal nano-cluster materials. Taking a chloroauric acid trihydrate aqueous solution and a chloroplatinic acid hexahydrate aqueous solution as a gold source and a platinum source, taking sodium citrate as a reducing agent, and taking glutathione as a stabilizing agent and a ligand; firstly, uniformly mixing a chloroauric acid trihydrate aqueous solution and a chloroplatinic acid hexahydrate aqueous solution, adding a glutathione solution into the mixed solution, uniformly mixing, and then adding a sodium citrate solution; and then transferring the mixed solution into a reaction kettle, and carrying out hydrothermal reaction for 30-210 minutes at 100-120 ℃ to obtain the gold-platinum alloy nano-cluster solution protected by glutathione and having strong fluorescence emission. The invention realizes the controllable preparation of the gold-platinum alloy nanoclusters with two different fluorescence emissions and high stability by finely regulating and controlling the experimental conditions such as reaction time, reaction temperature, the charge ratio of reaction raw materials and the like.

Description

Glutathione-protected strong fluorescence-emission gold-platinum alloy nano-cluster and controllable preparation method thereof

Technical Field

The invention belongs to the technical field of preparation of a strong near infrared luminescence (NIR) metal nano-cluster material, and particularly relates to a glutathione-protected strong fluorescence emission gold platinum alloy nano-cluster with a red light or near infrared fluorescence emission characteristic and a controllable preparation method thereof.

Background

Metal Nanoclusters (NCs) have excellent optical properties and thus have attracted great attention in the fields of fluorescence sensing, imaging, and labeling. Most importantly, by changing the ligand type in the metal nanocluster or the number of metal atoms forming the nanocluster, the emission wavelength of the metal Nanoclusters (NCs) can be changed from visible light fluorescence emission to Near Infrared (NIR) fluorescence emission, and the red shift of the fluorescence emission wavelength is beneficial to promoting the application of the nanoclusters in aspects of fluorescence imaging and the like. At present, gold nanoclusters with adjustable size and fluorescence emission peak have been prepared in the existing research results, wherein one method is to change the number of metal atoms forming the metal nanoclusters, such as Au connected by polyaminoamine dendrimers₅、Au₈、Au₁₃、Au₂₃And Au₃₁(gold nanoclusters consisting of 5, 8, 13, 23 and 31 gold atoms, respectively) that can produce ultraviolet-visible absorption, blue, green, red and near infrared fluorescence emission, respectively (Phys Rev Lett 2004,93, 077402); another method is to modify the ligand to realize the controllability of the particle size and fluorescence emission of the metal nanocluster, such as modifying the polyethylene glycol ligand to modify it with methoxy, amino or carboxyl (-OCH)₃、-NH₂or-COOH) and eventually the metal nanoclusters exhibit red, yellow and blue fluorescence emissions, respectively (Langmuir 2016,32, 6445).

In recent years, although there have been few advances in nanocluster research, reports on near infrared fluorescence emission nanoclusters (NIR-NCs) have been limited. The near-infrared fluorescence emission can enhance the tissue penetrating power and reduce the background interference of tissue autofluorescence, so the near-infrared fluorescence emission metal nano-cluster has great potential in biological application. In the preparation of metal nanoclusters for near-infrared fluorescence emission, near-infrared fluorescence emission is realized by changing the number of metal atoms in the metal nanoclusters, for example, in the preparation of thiolated gold nanoclusters (AuNC), the number of gold atoms forming the gold nanoclusters is changedPreparation of Au₁₁、Au₃、Au₁₄₀And Au₂₀₁(gold nanoclusters consisting of 11, 38, 140 and 201 gold atoms, respectively) to have a near infrared fluorescence emission range of 800 to 1300 nm (Adv Mater 2019,31, e 1901015); in addition, gold nanoclusters (AuNCs) having a fluorescence emission peak in the range of 900-1000 nm, which have a good fluorescence quantum yield (FL QY%), and which have relatively excellent stability under physiological conditions, are prepared by using zwitterionic ligands (Phys Rev Lett 2004,93, 077402). These near infrared fluorescence emission nanoclusters (NIR NCs) above achieve near infrared fluorescence emission by changing the size of the ligands or cores, but all focus on single metal nanomaterials. To our knowledge, foreign atom doping is a powerful technique for improving the luminescent properties of metal nanoclusters. Therefore, alloy nanoclusters having near-infrared fluorescence emission will become one of the popular researches.

In the work of the invention, a gold-platinum metal nano cluster (Au-PtNCs @ GSH) protected by Glutathione (GSH) with adjustable luminescence can be controllably prepared by a hydrothermal synthesis method, so that the fluorescence emission wavelength of the gold-platinum metal nano cluster is 625 nm and 805 nm. Characterization of the metal nanoclusters by characterization means such as ultraviolet-visible absorption spectroscopy, high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS) and the like, shows that the core size and metal ratio of the alloy nanoclusters and the results are well matched to their unique function. Therefore, the current work provides a new approach for preparing bimetallic nanoclusters with controllable fluorescence emission through a hydrothermal synthesis method, which will stimulate more researches on exploring the use of the metal nanoclusters.

Disclosure of Invention

The invention aims to provide a glutathione-protected strong fluorescence-emission gold platinum alloy nano-cluster with red light or near-infrared fluorescence emission characteristics prepared by a hydrothermal synthesis method and a controllable preparation method (Au-Pt @ GSHNCs) thereof. By adopting a hydrothermal method, the gold-platinum alloy nanocluster with the strongest fluorescence intensity and near infrared luminescence (with the fluorescence emission wavelength of 805 nm) is obtained based on the preparation conditions of the embodiments 1 to 4, and by adopting the same method, the gold-platinum alloy nanocluster with red luminescence (with the fluorescence emission wavelength of 625 nm) is successfully prepared. The gold-platinum alloy nano-cluster has good luminous characteristics, large Stokes shift (near infrared fluorescence emission is 155nm, red fluorescence emission is 245nm) and high stability, and the two gold-platinum alloy nano-clusters can be stored for 4 months at the temperature of 4 ℃.

The invention successfully synthesizes gold-platinum alloy nanoclusters (Au-Pt @ GSHNCs) protected by glutathione and having strong fluorescence emission by adopting a one-step hydrothermal method, wherein a chloroauric acid trihydrate aqueous solution and a chloroplatinic acid hexahydrate aqueous solution are used as an gold source and a platinum source, CA (sodium citrate) is used as a reducing agent, and GSH (glutathione) is used as a stabilizing agent and a ligand; firstly, uniformly mixing a chloroauric acid trihydrate aqueous solution and a chloroplatinic acid hexahydrate aqueous solution, adding a glutathione solution into the mixed solution, uniformly mixing, and then adding a sodium citrate solution; and then transferring the mixed solution into a reaction kettle, and carrying out hydrothermal reaction at 100-120 ℃ for 60-210 minutes to obtain a glutathione-protected gold-platinum alloy nanocluster (Au-Pt @ GSHNCs) solution with strong fluorescence emission.

In the method, the molar dosage of the chloroauric acid trihydrate is 8 millimoles, and the molar dosage ratio of the chloroauric acid trihydrate aqueous solution to the chloroplatinic acid hexahydrate aqueous solution is 8: (0.5-4), wherein the molar use ratio of the ligand glutathione to the total amount of metal ions (gold and platinum) is (1-4.5): 1, the molar usage ratio of the reducing agent sodium citrate to the total amount of metal ions (gold and platinum) is (11-33): 1.

drawings

FIG. 1: the fluorescence intensity of Au-PtNCs @ GSH as a function of reaction time and reaction temperature (a, c) and bar graphs (b, d).

FIG. 2: the fluorescence intensity of Au-PtNCs @ GSH as a function of the molar ratio of gold to platinum at the time of dosing (a) and bar graph (b).

FIG. 3: curve (a) and bar graph (b) of fluorescence intensity of Au-PtNCs @ GSH versus molar ratio of metal ions (gold and platinum) to ligand (GSH) at dosing.

FIG. 4: curve (a) and bar graph (b) of the fluorescence intensity of Au-PtNCs @ GSH versus the molar amount of reducing agent sodium Citrate (CA) at dosing.

FIG. 5: fluorescence excitation and fluorescence emission spectra (a) of Au-PtNCs @ GSH with fluorescence emission wavelength of 805 nm and ultraviolet-visible absorption spectra (b) of Au-PtNCs @ GSH.

FIG. 6: high resolution transmission electron microscopy (HR-TEM) (a) and particle size distribution bar graph (b) of Au-PtNCs @ GSH with a fluorescence emission wavelength of 805 nm.

FIG. 7: x-ray photoelectron spectroscopy (XPS) of gold element (a) and platinum element (b) in Au-PtNCs @ GSH with emission wavelength of 805 nm.

FIG. 8: fluorescence excitation and fluorescence emission spectra of Au-PtNCs @ GSH with an emission wavelength of 625 nm.

FIG. 9: fluorescence excitation spectrum (a) and fluorescence intensity change curve (b) of Au-PtNCs @ GSH as a function of reaction time.

FIG. 10: UV-visible absorption spectrum of Au-PtNCs @ GSH as a function of reaction time.

FIG. 11: high resolution transmission electron microscopy (HR-TEM) (a) and particle size distribution bar graph (b) of Au-PtNCs @ GSH with an emission wavelength of 625 nm.

FIG. 1 corresponds to example 1 and example 2; FIG. 2 corresponds to example 3; FIG. 3 corresponds to example 4; FIG. 4 corresponds to example 5; FIGS. 5-7 correspond to example 6; fig. 8-11 correspond to example 7.

As shown in fig. 1 to 4, by the hydrothermal synthesis method, as various conditions such as reaction time, reaction temperature, molar ratio of gold and platinum, molar ratio of ligand Glutathione (GSH) to metal ions, and molar ratio of reducing agent sodium Citrate (CA) to metal ions in the preparation process are changed, the fluorescence intensity of the gold-platinum alloy nanoclusters is also changed accordingly. In addition, in the preparation process, the gold-platinum alloy nanoclusters protected by glutathione with fluorescence emission wavelengths of 625 nanometers and 805 nanometers respectively are successfully and controllably prepared by regulating and controlling reaction time and temperature.

In addition, the two different fluorescence-emitted gold-platinum alloy nanoclusters are characterized by means of an ultraviolet-visible absorption spectrum, a fluorescence spectrum, a high-resolution transmission electron microscope and the like.

The gold platinum alloy nanocluster with the fluorescence emission peak of 805 nanometers prepared under the optimized condition is subjected to morphology characterization by a high-resolution transmission electron microscope (HR-TEM) (FIG. 6a), and the graph shows that the nanoparticles are high in dispersity and uniform in particle size. The average grain size was found to be 2.39 nm by systematic analysis of approximately 200 particles (fig. 6 b). The interplanar spacing (-0.23 nm) of the particles (inset in fig. 6a) is between the 111 interplanar spacing of platinum atoms (0.226 nm) and the 111 interplanar spacing of gold atoms (0.236 nm). In addition, the ultraviolet-visible absorption spectrum is used for carrying out preliminary analysis on the optical properties in the process of preparing the gold-platinum alloy nanocluster (Au-PtNCs @ GSH). As shown in fig. 7, a broad absorption peak exists near 500 nm in the absorption spectrum; and the intensity of the absorption peak is increased along with the prolonging of the reaction time. The results indicate that the particle diameter of the nanoclusters increases with time during the preparation of the gold platinum alloy nanoclusters. The gold and platinum in the gold-platinum alloy nanocluster (Au-PtNCs @ GSH) coexist in four valence states, which are Au (0), Au (I), Pt (I) and Pt (II) (FIG. 8). We speculate that the Au (0) is distributed in the core, and Au (I), Pt (I) and Pt (II) are distributed outside the core of the nano-cluster. In the same way, the gold-platinum alloy nanocluster with a fluorescence emission peak of 625 nanometers is analyzed, and the average size of crystal grains is 1.40 nanometers. The interplanar spacing (-0.23 nm) of the particles (inset in fig. 6a) is between the 111 interplanar spacing of platinum atoms (0.226 nm) and the 111 interplanar spacing of gold atoms (0.236 nm).

Through the research, the gold-platinum alloy nanoclusters protected by glutathione and having different fluorescence emissions are controllably prepared by a hydrothermal synthesis method.

Detailed Description

Example 1:

in this example, the effect of different reaction times on the fluorescence intensity of the nanoclusters was mainly explored. Adding 10 mmol/ml aqueous chloroauric acid trihydrate and 800 microliters and 100 microliters of aqueous chloroplatinic acid hexahydrate into a polytetrafluoroethylene lining of a stainless steel reaction kettle, uniformly stirring, adding 360 microliters of aqueous glutathione solution with the concentration of 100 mmol/ml, and then adding 400 microliters and 500 mmol/ml aqueous sodium Citrate (CA) solution. And finally, adding deionized water to enable the volume of the solution to be 10 milliliters, uniformly stirring, transferring the polytetrafluoroethylene lining into a stainless steel reaction kettle, placing the stainless steel reaction kettle into a drying oven, and carrying out hydrothermal reaction at the set temperature of 110 ℃. And then taking out the reaction kettle after 30, 60, 90, 120, 150, 180, 210 and 240 minutes respectively, and cooling to room temperature to obtain the gold-platinum alloy nanocluster (Au-PtNCs @ GSH) solution with strong fluorescence emission and protected by glutathione, which is prepared under different reaction time conditions.

The fluorescence emission spectra of the gold-platinum alloy nanoclusters at different reaction times are obtained through fluorescence spectra, and the conclusion that we can obtain from the graphs in fig. 1(a) and (b) is that: the emission peak of the gold platinum alloy nanoclusters was strongest at 110 ℃ with a reaction time of 150 minutes, and we used this reaction time for the next experiment.

Example 2:

in this example, the effect of different reaction temperatures on the fluorescence intensity of the nanoclusters was mainly explored. An aqueous solution of chloroauric acid trihydrate having a concentration of 10 mmol/ml and an aqueous solution of chloroplatinic acid hexahydrate having a concentration of 800. mu.l and 100. mu.l, respectively, were added to a polytetrafluoroethylene liner, and after stirring the mixture uniformly, 360. mu.l of an aqueous solution of glutathione having a concentration of 100 mmol/ml was added, and then 400. mu.l of an aqueous solution of sodium Citrate (CA) having a concentration of 500 mmol/ml was added. And finally, adding deionized water to enable the volume of the solution to be 10 milliliters, uniformly stirring, transferring the polytetrafluoroethylene lining into a stainless steel reaction kettle, placing the stainless steel reaction kettle into an oven, and performing hydrothermal reaction at the temperatures of 100 ℃, 110 ℃ and 120 ℃ respectively for 150 minutes. And (4) taking out the reaction kettle after the reaction is finished, and cooling to room temperature to obtain Au-PtNCs @ GSH prepared under the conditions of different reaction temperatures.

The fluorescence emission spectra of the gold-platinum alloy nanoclusters at different reaction temperatures are obtained through fluorescence spectra, and the conclusion that we can obtain from the graphs in fig. 1(c) and (d) is that: the emission peak of the gold platinum alloy nanocluster is strongest at the reaction temperature of 110 ℃, so we use the reaction temperature for the next experiment.

Example 3:

in this example, the effect of the molar amounts of chloroauric acid and chloroplatinic acid on the fluorescence intensity of the nanoclusters was mainly explored. Adding 800 microliters of aqueous chloroauric acid trihydrate solution with the concentration of 10 mmol/ml into a polytetrafluoroethylene lining, then respectively adding 50, 100, 200, 300 and 400 microliters of aqueous chloroplatinic acid hexahydrate solution with the concentration of 10 mmol/ml, stirring uniformly, then respectively adding 340, 360, 400, 440 and 480 microliters of Glutathione (GSH) aqueous solution with the concentration of 100 mmol/ml, and then respectively adding 400 microliters and 500 mmol/ml sodium Citrate (CA) aqueous solution. And finally, adding deionized water to enable the volume of the solution to be 10 milliliters, uniformly stirring, transferring the polytetrafluoroethylene lining into a stainless steel reaction kettle, placing the stainless steel reaction kettle into an oven, and setting the temperature of the oven to be 110 ℃ for hydrothermal reaction for 150 minutes. And after the reaction is finished, cooling to room temperature to obtain Au-PtNCs @ GSH prepared under the condition of different gold-platinum ratio during feeding.

The fluorescence emission spectra of the gold-platinum alloy nanoclusters at different gold-platinum ratios are obtained by fluorescence spectroscopy, and the conclusion that we can obtain from fig. 2 is that: when the molar ratio of gold to platinum is 8: 1, the emission peak of the gold-platinum alloy nanocluster is strongest, so we use the gold-platinum ratio for the next experiment.

Example 4:

in this example, the effect of the ratio of the total molar amount of different metal ions (gold and platinum) to the molar amount of the ligand glutathione on the fluorescence intensity of the nanoclusters was mainly explored. Adding 10 mmol/ml aqueous chloroauric acid trihydrate and 100. mu.l aqueous chloroplatinic acid hexahydrate into a polytetrafluoroethylene lining, stirring uniformly, adding 100 mmol/ml aqueous glutathione respectively, and enabling the molar ratio of the molar amount of the aqueous glutathione to the sum of the molar amounts of metal ions (gold and platinum) to be 1: 1. 1: 1.5, 1: 2. 1: 2.5, 1: 3. 1: 3.5, 1: 4 and 1: 4.5, then 400. mu.l of 500 mmol/ml aqueous sodium Citrate (CA) solution was added. And finally adding deionized water to enable the volume of the solution to be 10 milliliters, uniformly stirring, transferring the polytetrafluoroethylene lining into a stainless steel reaction kettle, placing the stainless steel reaction kettle into an oven, setting the temperature of the oven to be 110 ℃, carrying out hydrothermal reaction for 150 minutes, taking out the reaction kettle, and cooling to room temperature to obtain Au-PtNCs @ GSH prepared under the conditions of different ligand-metal ion ratios.

The fluorescence emission spectra of the gold-platinum alloy nanoclusters under different ligand-to-metal ion ratios are obtained through fluorescence spectroscopy, and the conclusion that we can obtain from fig. 3 is that: when the molar ratio of ligand to metal ion is 4: 1, the emission peak of the gold-platinum alloy nanocluster is strongest, so we use the ligand to metal ion ratio for the next experiment.

Example 5:

in this example, the effect on the fluorescence intensity of the nanoclusters at different molar amounts of the reducing agent sodium citrate was mainly explored. Adding 10 mmol/ml aqueous chloroauric acid trihydrate and 360 microliters aqueous chloroplatinic acid hexahydrate into a polytetrafluoroethylene lining, stirring uniformly, adding 0, 100, 200, 300, 400, 500 and 600 microliters of 500 mmol/ml aqueous sodium citrate (at this time, the molar amount of sodium citrate is 0, 50, 100, 150, 200, 250 and 300 mmol respectively, and the molar amount of sodium citrate and the total molar amount of metal ions, namely the molar amount of chloroauric acid and chloroplatinic acid is 0: 9, 5.6: 1, 11: 1, 16.7: 1, 22: 1, 27.8: 1 and 33: 1 respectively), adding deionized water to make the volume of the solution 10 milliliters, stirring uniformly, transferring the polytetrafluoroethylene lining into a stainless steel reaction kettle, and placing the stainless steel reaction kettle in an oven, setting the temperature of the oven at 110 ℃ for hydrothermal reaction for 150 minutes, taking the reaction kettle out, and cooling to room temperature to obtain Au-PtNCs @ GSH prepared under the conditions of different reducing agent sodium Citrate (CA) concentrations.

The fluorescence emission spectra of the gold-platinum alloy nanoclusters at different reducing agent sodium Citrate (CA) concentrations were obtained by fluorescence spectroscopy, and we can conclude from FIG. 4 that: when the molar amount of the reducing agent is 150 mmol (in this case, the ratio of the molar amount of the sodium citrate to the total molar amount of the metal ions, i.e., the molar total amount of the chloroauric acid and the chloroplatinic acid, is 16.7: 1), the emission peak of the gold-platinum alloy nanocluster is strongest, and therefore, the molar amount of the reducing agent is used in the next experiment.

Example 6:

according to the results of examples 1 to 5, an aqueous 10 mmol/ml chloroauric acid trihydrate solution and an aqueous hexachloroplatinic acid hexahydrate solution were added to a polytetrafluoroethylene liner in an amount of 800. mu.l and 100. mu.l, respectively, and after stirring them uniformly, 360. mu.l of an aqueous 100 mmol/ml glutathione solution and 300. mu.l of an aqueous 500 mmol/ml sodium Citrate (CA) solution were added thereto. And finally adding deionized water to enable the volume of the solution to be 10 milliliters, uniformly stirring, transferring the polytetrafluoroethylene lining into a stainless steel reaction kettle, setting the temperature of an oven to be 110 ℃, carrying out hydrothermal reaction for 150 minutes, taking out the reaction kettle, and cooling to room temperature to finally obtain Au-PtNCs @ GSH with the highest fluorescence intensity after the preparation conditions are optimized.

The results show that: the gold-platinum alloy nanoclusters (Au-PtNCs) obtained in the embodiment 6 have the strongest excitation wavelength of 645-660 nanometers and the strongest emission wavelength of 800-810 nanometers, and have larger Stokes shift (155 nanometers). The morphology of the gold-platinum alloy nanoclusters (Au-PtNCs) prepared under the optimized conditions was characterized by a high-resolution transmission electron microscope (HR-TEM) (FIG. 6 a). It can be seen from the figure that the dispersibility of the nanoparticles is high and the particle size is uniform (fig. 2 b). The average grain size was found to be 1.69 nm by systematic analysis of approximately 200 particles. The interplanar spacing (-0.23 nm) of the particles (inset in fig. 6a) was between the 111 interplanar spacing of platinum atoms (0.226 nm) and the 111 interplanar spacing of gold atoms (0.236 nm). furthermore, the optical properties of the gold-platinum alloy nanoclusters (Au-PtNCs) were preliminarily analyzed by uv-vis absorption spectroscopy and fluorescence spectroscopy, respectively. As shown in fig. 5b, there is a broad absorption peak near 350 nm in the absorption spectrum; an emission peak at wavelength 805 nm was obtained when excited at 650 nm (FIG. 5 a). The results indicate that the gold platinum alloy nanoclusters (Au-PtNCs) have larger Stokes shift (155 nm). Gold and platinum in the platinum alloy nanoclusters (Au-PtNCs) coexist in a total of four valence states, which are Au (0), Au (I), Pt (I) and Pt (II), respectively (FIG. 7). We speculate that the Au (0) is distributed in the core, and the Au (I), the Pt (I) and the Pt (II) are distributed outside the core of the nano-cluster. The fluorescence quantum yield of the gold-platinum alloy nanoclusters (Au-PtNCs) is 1.2%. In addition, compared with red and near-infrared luminescent materials reported in documents, the prepared near-infrared luminescent material has more environment-friendly preparation conditions, shorter preparation time and more outstanding cost performance compared with similar near-infrared luminescent materials; compared with the red-blue luminescent material prepared from the same raw material, the fluorescence emission wavelength of the material is more red-shifted, and the material provides an implementation basis for some biological imaging.

Example 7:

adding 10 mmol/ml aqueous chloroauric acid trihydrate solution and 100 microliters aqueous chloroplatinic acid hexahydrate solution into the polytetrafluoroethylene lining, respectively, stirring uniformly, and then adding 360 microliters and 300 microliters of 100 mmol/ml aqueous glutathione solution and 500 mmol/ml aqueous sodium Citrate (CA) solution. And finally, adding deionized water to ensure that the volume of the solution is 10 milliliters, uniformly stirring, transferring the polytetrafluoroethylene lining into a stainless steel reaction kettle, and setting the temperature of an oven to be 110 ℃ to perform hydrothermal reaction. And then taking out the reaction kettle after 60 minutes, 80 minutes, 100 minutes, 120 minutes, 150 minutes, 180 minutes and 210 minutes, and cooling to room temperature to obtain the gold-platinum alloy nanoclusters (Au-PtNCs @ GSH) protected by the glutathione under different reaction times. The change of the fluorescence emission peak of the gold-platinum alloy nano-cluster and the change of the intensity thereof at different times are monitored by a fluorescence spectrometer. As shown in fig. 9, we can see that only a fluorescence emission peak of 625 nm fluorescence emission exists during 60 to 100 minutes and increases with time; when the reaction time is 120 minutes, the condition that two fluorescence emission peaks exist is shown; when the reaction time was 150 to 210 minutes, only a fluorescence emission peak having a fluorescence emission of 805 nm existed and the fluorescence intensity decreased with time. In the process of preparing the near-infrared luminescent glutathione-protected gold-platinum alloy nanoclusters, red luminescent gold-platinum alloy nanoclusters can be prepared by controlling the temperature and the time, and as the reaction time is prolonged, the red fluorescence emission peak disappears and a near-infrared fluorescence emission peak appears as shown in fig. 8, wherein the fluorescence excitation wavelength of the gold-platinum alloy nanoclusters is 380 nm, and the fluorescence emission wavelength is 625 nm.

In addition, as shown in FIG. 10, the absorbance at different reaction times was monitored by a UV-Vis spectrophotometer. We found that the absorbance increased with the reaction time, and we speculated that the diameter of the nanocluster increased with the reaction time, resulting in different fluorescence emission peaks. The morphology of the gold-platinum alloy nanoclusters (Au-PtNCs) prepared under optimized conditions was characterized using a high-resolution transmission electron microscope (HR-TEM) (FIG. 11 a). It can be seen from the figure that the dispersibility of the nanoparticles is high and the particle size is uniform (fig. 11 b). The average size of the grains was found to be-1.40 nm by systematic analysis of about 200 particles. The interplanar spacing (-0.23 nm) of the particles (inset in fig. 6a) is between the 111 interplanar spacing of platinum atoms (0.226 nm) and the 111 interplanar spacing of gold atoms (0.236 nm).

By regulating and controlling the reaction time, a technical guarantee is provided for controllably preparing the glutathione-protected gold-platinum alloy nanoclusters with red and near-infrared fluorescence emission.

It should also be noted that the particular embodiments of the present invention are provided for illustrative purposes only and do not limit the scope of the present invention in any way, and that modifications and variations may be made by persons skilled in the art in light of the above teachings, but all such modifications and variations are intended to fall within the scope of the invention as defined by the appended claims.

Claims

1. A controllable preparation method of a glutathione-protected strong fluorescence emission gold-platinum alloy nano-cluster is characterized by comprising the following steps: taking a chloroauric acid trihydrate aqueous solution and a chloroplatinic acid hexahydrate aqueous solution as a gold source and a platinum source, taking sodium citrate as a reducing agent, and taking glutathione as a stabilizing agent and a ligand; firstly, uniformly mixing a chloroauric acid trihydrate aqueous solution and a chloroplatinic acid hexahydrate aqueous solution, adding a glutathione solution into the mixed solution, uniformly mixing, and then adding a sodium citrate solution; then transferring the mixed solution into a reaction kettle, and carrying out hydrothermal reaction for 60-210 minutes at 100-120 ℃ to obtain a glutathione-protected gold-platinum alloy nanocluster Au-Pt @ GSHNCs solution with red light or near-infrared fluorescence emission characteristics and strong fluorescence emission; wherein the molar amount of the chloroauric acid trihydrate is 8 millimoles, and the molar amount ratio of the chloroauric acid trihydrate aqueous solution to the chloroplatinic acid hexahydrate aqueous solution is 8: (0.5-4), wherein the molar usage ratio of the total amount of the ligand glutathione to the total amount of the metal ions is (1-4.5): 1, the molar usage ratio of the reducing agent sodium citrate to the total amount of the metal ions is (11-33): 1.

2. a glutathione-protected, strong fluorescence emitting gold-platinum alloy nanocluster characterized in that: is prepared by the method of claim 1.