CN113059175A

CN113059175A - Preparation method of Au @ Ag @ AgCl nanoparticles and application of Au @ Ag @ AgCl nanoparticles in ammonia colorimetric detection

Info

Publication number: CN113059175A
Application number: CN202110021621.8A
Authority: CN
Inventors: 曾景斌; 仇志伟; 梁心怡; 崔炳文; 张云芝
Original assignee: China University of Petroleum East China
Current assignee: China University of Petroleum East China
Priority date: 2021-01-08
Filing date: 2021-01-08
Publication date: 2021-07-02
Anticipated expiration: 2041-01-08
Also published as: CN113059175B

Abstract

The invention discloses a preparation method of Au @ Ag @ AgCl nano particles for colorimetric detection of ammonia concentration₄And reducing the solution in a water phase to prepare the Au nanospheres. Then reducing AgNO with ascorbic acid under alkalescent condition by epitaxial growth method₃Solution, a silver shell was deposited onto the preformed Au nanospheres. Then, passing through FeCl₃Oxide etching of Ag shellAnd (3) etching, namely depositing a thin layer of AgCl on the Au @ Ag nano particles to obtain the Au @ Ag @ AgCl nano particles with three layers of core-shell structures. The nanometer probe has strong specificity, high sensitivity, stable performance, convenience and rapidness for ammonia response, and can realize rapid qualitative and semi-quantitative analysis of ammonia concentration by naked eyes.

Description

Preparation method of Au @ Ag @ AgCl nanoparticles and application of Au @ Ag @ AgCl nanoparticles in ammonia colorimetric detection

Technical Field

The invention relates to an Au @ Ag @ AgCl nano particle with a three-layer core-shell structure, in particular to an Au @ Ag @ AgCl nano particle probe suitable for ammonia colorimetric detection.

Background

Ammonia is a colorless and toxic gas with a strong pungent odor, and its main sources include both natural and artificial aspects. Nitrogen in the air can be converted into ammonia gas under the fixation action of microbial plants to enter the soil and participate in ecological cycle; and the chemical industry, the metallurgical industry, the automobile manufacturing industry, the refrigeration industry, the coal mine combustion industry and other industries can also artificially produce a large amount of ammonia gas. In recent decades, with the rapid development of industrialization and urbanization, the emission of ammonia gas worldwide has increased year by year. As a gas with great harm to human bodies, even at a low concentration, ammonia gas can also bring serious stimulation to oral cavities, skin mucous membranes, upper respiratory tracts and the like of human bodies. The united states Occupational Safety and Health Administration (OSHA) stipulates that the upper limit of the ammonia gas concentration in the air is 25ppm, but the olfaction limit of human beings on the ammonia gas is 55ppm, and the content of the ammonia gas in the air cannot be simply judged through olfaction, so that potential safety hazards are brought in industry and daily life. Therefore, the ammonia gas is detected accurately and quickly in real time, which not only helps to monitor the environmental pollution problem, but also has important significance for ensuring production safety and public health.

Conventional methods for detecting the ammonia gas concentration include gas chromatography, electrochemical methods, fluorescence methods, and the like. These detection methods have relatively ideal detection sensitivity and have been proved to be practical for a long time, but the defects are obvious. On the one hand, these methods require expensive large instruments and professional operators, and are difficult to realize rapid and real-time detection; on the other hand, the detection conditions of the methods are harsh, such as the semiconductor electrochemical sensors often need higher working temperature,meanwhile, the method also has the inherent defects of easy moisture, long recovery time and the like. In addition to the above methods, colorimetric methods are also widely used in the field of analytical detection because of their low cost, simple operation and ease of semi-quantitative detection. Conventional colorimetric detection of ammonia gas has been accomplished primarily using organic dyes as probes, including Nessler reagents, indoxyl blue, pH sensitive dyes, etc., which upon binding to ammonia gas cause a structural change in the organic molecule resulting in a macroscopic color change, which are easy to implement, but remain insensitive to in situ gaseous ammonia gas determination (T.F. Hartley, Annals of Clinical Biochemistry,11(1974) 137-. Recently, some scientists have proposed using the localized surface plasmon resonance effect of noble metal nanomaterials to detect ammonia. For example, Ag (NH) is formed by reaction with ammonia gas using silver nanoparticles as probes₃)₂ ⁺The complex is used for regulating and controlling the surface plasmon band of the silver nanoparticles, thereby realizing the colorimetric detection of ammonia gas (S.Pandey, International Journal of Biological Macromolecules,51(2012), 583-. However, the sensitivity of the noble metal nano material probe to ammonia gas still needs to be improved, and meanwhile, the silver nano particles are easy to oxidize and have insufficient stability, so that the practical application of the noble metal nano material probe in the field of ammonia gas content detection in practical places is reduced to a certain extent.

Disclosure of Invention

The invention aims to provide Au @ Ag @ AgCl nanoparticles for colorimetric detection of ammonia concentration and a preparation method thereof, wherein the Au @ Ag @ AgCl nanoparticles have the advantages of sensitive reaction, strong specificity, high stability and the like, and the Au @ Ag @ AgCl nanoparticles are used as specific probes aiming at the defects of the existing ammonia colorimetric detection method that the probe sensitivity needs to be improved, the stability is poor and the like.

The invention also aims to provide application of the Au @ Ag @ AgCl nanoparticle probe in colorimetric detection of ammonia gas concentration in an actual air sample.

The Au @ Ag @ AgCl nanoparticle probe is a spherical nanoparticle with a three-layer core-shell structure, wherein Au nanoparticles are used as cores, and the diameter of the Au nanoparticles is 12.9-13.5 nm; ag is an inner shell, and the thickness of the shell is 1.6-4.6 nm; the AgCl is an outer shell, and the thickness of the shell is 0.7-2.3 nm.

The preparation method of the Au @ Ag @ AgCl nanoparticle probe comprises the following steps:

1) preparing Au nanoparticles: HAuCl is added into a three-neck flask in sequence₄The solution and water were heated under reflux and stirred. The sodium citrate solution was then added and heating continued for a period of time. The solution quickly turns purple black from the original light yellow, and is finally stabilized to wine red, so that Au nano-particles are obtained;

2) preparing Au @ Ag nanoparticles: sequentially adding the following components into a three-neck flask: and (2) stirring the Au nanoparticle solution obtained in the step 1) and water. Then quickly adding ascorbic acid solution and AgNO at one time₃Solutions and NaOH solutions. Stirring the mixture to continue reacting for a period of time, centrifuging at a certain speed and for a certain period of time, removing the supernatant and dispersing into water to obtain Au @ Ag nano particles;

3) preparing an Au @ Ag @ AgCl nanoparticle probe: adding into a glass bottle in sequence: au @ Ag nano particle solution and FeCl obtained in step 2)₃And finally, obtaining the Au @ Ag @ AgCl core-shell nanoparticle probe, wherein the solution and the mixed solution are orange yellow.

In step 1), the HAuCl₄The volume ratio of the solution, water and the sodium citrate solution can be 5 mL: 95mL of: 10 mL; the HAuCl₄The solution adopts HAuCl with the molar concentration of 0.02428mol/L₄A solution; the water can adopt ultrapure water; the sodium citrate solution is a sodium citrate solution with the mass concentration of 11.46 mg/mL; the reflux heating temperature is 100 ℃; the heating time is 15 min.

In step 2), the Au nanoparticle solution, water, ascorbic acid solution, AgNO₃The volume ratio of the solution to the NaOH solution can be 10 mL: 40mL of: 120 μ L of: (60-90) μ L: (225-450) μ L, preferably 10 mL: 40mL of: 120 μ L of: 75 μ L of: 225 μ L; the water can adopt ultrapure water; the ascorbic acid solution is prepared fromAscorbic acid solution with a molar concentration of 100 mM; the AgNO₃The solution adopts AgNO with the molar concentration of 100mM₃A solution; the NaOH solution adopts a NaOH solution with the molar concentration of 100 mM; the reaction time is 30 min; the centrifugal speed can be 6000-10000 rpm, preferably 8000 rpm; the centrifugation time can be 10-30 min, and preferably 20 min; the volume of water used for dispersion may be 50 mL.

In step 3), the Au @ Ag nanoparticle solution and FeCl₃The volume ratio of the solution may be 1 mL: (6-18) μ L, preferably 1 mL: 12 mu L of the solution; the FeCl₃The molarity of the solution was 10 mM.

The Au @ Ag @ AgCl nanoparticle probe can be applied to ammonia gas colorimetric detection. The method applied is as follows:

100 μ L of known NH concentration was taken₃·H₂Adding 900 mu L of Au @ Ag @ AgCl nanoparticle probe solution into an O standard solution (0, 50, 100, 300, 600, 900, 1000, 1200, 1400 and 1600 mu M), fully mixing, reacting at room temperature for 10min, shooting the color of the solution by using a digital camera, and manufacturing a standard colorimetric card; and simultaneously, scanning the ultraviolet-visible absorption spectrum of the mixed solution by using a spectrophotometer, drawing a working curve by taking the absorbance change value at 510nm as a vertical coordinate and the concentration of the ammonia water standard solution as a horizontal coordinate, and obtaining a linear equation. Absorbing a polluted gas sample containing ammonia gas by using a 20mL medical injector, introducing 5mL of Au @ Ag @ AgCl nano particle probe solution into the injector in advance, incubating for 10 minutes at ambient temperature, shooting the color of the solution by using a digital camera, and comparing the color of the solution in the picture with a standard colorimetric card to perform semi-quantitative detection on the concentration of the ammonia gas in the detected polluted gas sample; and meanwhile, scanning the ultraviolet-visible absorption spectrum of the mixed solution to obtain the absorbance change value at the wavelength of 510nm, and substituting the absorbance change value into the linear equation to obtain the concentration of the ammonia in the polluted gas sample.

The invention provides a novel method for detecting ammonia gas, namely Au @ Ag @ AgCl nano particles with a three-layer core-shell structure are used as a colorimetric probe to quickly detect the concentration of the ammonia gas in the air. Firstly, using sodium citrate solution as a reducing agent, and adding HAuCl₄And reducing the solution in a water phase to prepare the Au nanospheres. Then reducing AgNO with ascorbic acid by epitaxial growth method under alkalescent condition₃Solution, a silver shell was deposited onto the preformed Au nanospheres. Then, passing through FeCl₃And (2) under the action of oxidizing and etching the Ag shell, depositing a thin layer of AgCl on the Au @ Ag nano particles to construct the Au @ Ag @ AgCl nano particles with a three-layer core-shell structure. The sensing mechanism of the Au @ Ag @ AgCl nanoparticle probe for ammonia gas is based on continuous etching of ammonia gas to AgCl and an Ag shell layer, so that the components of the nanoprobe and the components of the shell layer are changed, Ag and Au with local surface plasmon resonance effect inside are exposed, the absorbance of the material is changed, and the color of a probe solution is changed from orange to pink and then to red. In the Au @ Ag @ AgCl nanoparticle probe synthesized by the method, AgCl is introduced as an outermost shell, so that the Ag layer is protected, the stability of the probe to oxygen is enhanced, the color level is richer, and the sensitivity of the probe to ammonia is improved. The method for colorimetric detection of ammonia concentration by using the Au @ Ag @ AgCl nanoparticle probe has the advantages of strong specificity, high sensitivity, stable performance, convenience and quickness, can realize qualitative and semi-quantitative analysis of ammonia by naked eyes, and shows huge application potential in the aspect of real-time monitoring of ammonia content in air.

Drawings

FIG. 1 is a schematic diagram of the principle of colorimetric detection of ammonia gas by Au @ Ag @ AgCl nanoparticles with a three-layer core-shell structure.

Fig. 2 is a transmission electron micrograph and an ultraviolet-visible absorption spectrum of the Au nanoparticle of the present invention. In fig. 2, (a) is a transmission electron micrograph of Au nanoparticles; (b) is the ultraviolet-visible absorption spectrum of the Au nano-particles.

FIG. 3 is a transmission electron micrograph and UV-visible absorption spectra of Au @ Ag nanoparticles of the present invention. In FIG. 3, (a) is a transmission electron micrograph of Au @ Ag nanoparticles; (b) is an ultraviolet-visible absorption spectrogram of the Au @ Ag nano particles.

FIG. 4 is a transmission electron microscope image and a particle size distribution diagram of the Au @ Ag @ AgCl nanoparticle probe of the invention. In FIG. 4, the large image is a transmission electron micrograph of the Au @ Ag @ AgCl nanoparticle probe; the small internal graph is a particle size distribution diagram of the Au @ Ag @ AgCl nanoparticle probe.

FIG. 5 is a high resolution transmission electron micrograph and a selected area electron diffraction micrograph of the Au @ Ag @ AgCl nanoparticle probe of the present invention. In FIG. 5, the large image is a high resolution transmission electron micrograph of the Au @ Ag @ AgCl nanoparticle probe; and the internal small graph is a selected region electron diffraction graph of the Au @ Ag @ AgCl nanoparticle probe.

FIG. 6 is a transmission electron microscope image and an element distribution image of the Au @ Ag @ AgCl nanoparticle probe of the invention. In FIG. 6, (a) is a transmission electron micrograph of the Au @ Ag @ AgCl nanoparticle probe; (b) distribution imaging graphs of elements Au, Ag and Cl in the Au @ Ag @ AgCl nano particle probe are respectively shown in the (d) to (d); (e) is an imaging schematic diagram after elements Au, Ag and Cl are combined.

FIG. 7 is a graph of the UV-visible absorption spectrum of the Au @ Ag @ AgCl nanoparticle probe before/after addition of a certain amount of ammonia water.

FIG. 8 is a transmission electron microscope image and a particle size distribution diagram of the Au @ Ag @ AgCl nanoparticle probe of the invention after a certain amount of ammonia water is added. In FIG. 8, the transmission electron micrograph of the Au @ Ag @ AgCl nanoparticle probe after addition of a certain amount of ammonia water is shown in the figure; the small internal graph is a particle size distribution diagram of the Au @ Ag @ AgCl nanoparticle probe after a certain amount of ammonia water is added.

FIG. 9 is a graph showing the relationship between the reaction time and the absorbance of the characteristic peak in the UV-visible absorption spectrum in the process of detecting ammonia gas by using the Au @ Ag @ AgCl nanoparticle probe of the invention.

FIG. 10 is a graph showing the relationship between the pH value of the solution and the absorbance of a characteristic peak in an ultraviolet-visible absorption spectrum in the process of detecting ammonia gas with different concentrations by using the Au @ Ag @ AgCl nanoparticle probe of the invention.

FIG. 11 is a graph showing an ultraviolet-visible absorption spectrum of ammonia water with a concentration range of 0-1600 μ M and a linear relationship curve between an absorbance change value at 510nm and ammonia water concentration in an embodiment of the Au @ Ag @ AgCl nanoparticle probe of the present invention. In FIG. 11, (a) is a UV-VIS spectrum of the Au @ Ag @ AgCl nanoparticle probe in the embodiment, with the detection concentration range of 0-1600 μ M ammonia water; (b) the linear relation curve graph of the absorbance change value at 510nm of ammonia water with the detection concentration range of 0-1600 mu M and the ammonia water concentration in the embodiment of the Au @ Ag @ AgCl nano particle probe is disclosed.

FIG. 12 is a graph showing an ultraviolet-visible absorption spectrum of ammonia water with a detection concentration range of 1800-5000 μ M and a linear relationship curve between an absorbance change value at 510nm and ammonia water concentration in an embodiment of the Au @ Ag @ AgCl nanoparticle probe of the invention. In FIG. 12, (a) is a UV-VIS spectrum of an Au @ Ag @ AgCl nanoparticle probe in an embodiment, with the detection concentration of 1800-5000 μ M ammonia water; (b) the linear relation curve graph of the absorbance change value at 510nm of ammonia water with the detection concentration range of 1800-5000 mu M and the ammonia water concentration in the Au @ Ag @ AgCl nano particle probe embodiment is disclosed.

FIG. 13 is a graph comparing the response of the Au @ Ag @ AgCl nanoparticle probe of the present invention to ammonia gas detection with other 10 interfering reagents/gases.

FIG. 14 is a graph of UV-VIS spectra of different ammonia concentrations in actual contaminated air samples measured using an Au @ Ag @ AgCl nanoparticle probe according to an embodiment of the present invention.

Detailed Description

The following examples will further illustrate the present invention with reference to the accompanying drawings.

FIG. 1 shows a schematic diagram of the principle of colorimetric detection of ammonia gas by using the Au @ Ag @ AgCl nanoparticle probe with a three-layer core-shell structure. The Au @ Ag core-shell nano material is obtained by epitaxial growth, and FeCl is further used₃And oxidizing and etching the Ag shell to form an AgCl shell layer on the outermost layer. When the Au @ Ag @ AgCl nanoparticle probe is exposed to an ammonia environment, ammonia and an external AgCl shell layer react as follows: AgCl +2NH₃·H₂O═[Ag(NH₃)₂]⁺+Cl^-+2H₂O, so that an AgCl shell layer is etched, and the absorbance characteristic of Au @ Ag inside is exposed; when the concentration of ammonia gas is increased continuously, the ammonia gas can continuously etch the Ag shell layer to generate Ag +8NH₃·H₂O+O₂═4[Ag(NH₃)₂]⁺+4OH^-+6H₂O, thereby exposing the light absorbing properties of the Au inside. Therefore, the quantitative detection of the ammonia gas concentration can be realized according to the change of the color and the absorbance of the probe solution.

FIG. 2 shows a transmission electron microscope image and an ultraviolet-visible absorption spectrum of the Au nanoparticle of the invention. As shown in FIG. 2(a), the Au nanoparticles are uniform and spherical in morphology, have good dispersity and no obvious agglomeration phenomenon, and have a particle size range of 12.9-13.5 nm. Fig. 2(b) shows the uv-vis absorption spectrum of Au nanoparticles, and a distinct absorption peak appears at 510nm, corresponding to the characteristic absorption peak of nanogold.

FIG. 3 shows a transmission electron micrograph and an ultraviolet-visible absorption spectrum of the Au @ Ag nanoparticles of the present invention. As shown in FIG. 3(a), the Au @ Ag nano-particles are uniform and spherical in morphology, good in dispersity and free of obvious agglomeration, and the size range of the particles is 13.8-16.2 nm. FIG. 2(b) shows the UV-VIS absorption spectrum of Au @ Ag nanoparticles, showing two distinct absorption peaks at 390nm and 510nm, corresponding to the characteristic absorption peaks of nano-silver and nano-gold, respectively.

FIG. 4 shows a transmission electron microscope image and a particle size distribution diagram of the Au @ Ag @ AgCl nanoparticle probe of the present invention. As shown in a transmission electron microscope image of FIG. 4, the Au @ Ag @ AgCl nanoparticle probe is uniform and spherical in morphology, and has good dispersity and no obvious agglomeration phenomenon. As shown by a particle size distribution diagram presented by a small graph, the size distribution of the Au @ Ag @ AgCl nano particle probe is concentrated, and the range is 15.7-17.3 nm.

FIG. 5 shows a high resolution transmission electron micrograph and a selected area electron diffraction pattern of the Au @ Ag @ AgCl nanoparticle probe of the present invention. As shown in FIG. 5, the high resolution TEM image clearly shows the morphology of a single nanoparticle, which is shown by the lattice diffraction fringes of the particles with the size of

The lattice fringes of (2) correspond to the Au of the (111) crystal face and have the size of

The lattice fringes of (a) correspond to the AgCl of the (200) crystal plane, confirming the composition of the nanoprobe. At the same time, the same crystal properties are confirmed by the selected electron diffraction pattern presented by the small figure.

FIG. 6 shows a transmission electron microscope image and an element distribution image of the Au @ Ag @ AgCl nanoparticle probe of the invention. According to the element distribution imaging chart, Au is located in the material, and the size of Au is smaller than that of Ag and Cl; the Ag and the Au present the appearance structure of concentric circles and the size is slightly larger than the Au; cl, Au and Ag are in the shape of concentric circles, the size of the Cl, Au and Ag is slightly larger than that of Au, and the Cl, the Au, the Ag and the AgCl are basically the same as those of Ag, and the structural characteristics that Au is an inner shell, Ag is an outer shell and AgCl is an outer shell are confirmed. The characterization results show that the Au @ Ag @ AgCl nanoparticles with three-layer core-shell structures are successfully synthesized by the method provided by the invention.

FIG. 7 shows the UV-visible absorption spectrum of the Au @ Ag @ AgCl nanoparticle probe of the present invention before/after addition of a certain amount of ammonia water. As shown in the figure, after the outer layer is oxidized and etched into an AgCl shell layer, the characteristic absorption peak of the nano Ag at 390nm is reduced due to the masking effect of AgCl. And when 250 mu M ammonia water is added into the Au @ Ag @ AgCl nano particle probe, AgCl +2NH is generated between the ammonia water and AgCl₃·H₂O═[Ag(NH₃)₂]⁺+Cl^-+2H₂And through the reaction of O, the AgCl shell layer is etched and consumed, the shielding effect is weakened, and the internal Au core and the Ag shell are exposed, so that the intensities of the characteristic absorption peak of the nano Ag at 390nm and the characteristic absorption peak of the nano Au at 510nm are increased, and the good response of the Au @ Ag @ AgCl nano particle probe to ammonia is proved.

FIG. 8 shows a transmission electron microscope image and a particle size distribution diagram of the Au @ Ag @ AgCl nanoparticle probe of the invention after a certain amount of ammonia water is added. As shown in the figure, after 250 μ M of ammonia water is added, the nanoparticles still maintain good dispersibility and relatively complete spherical morphology, and the size is reduced to a certain extent. As shown by a particle size distribution diagram in a small graph, the size range of the nano particles after the reaction with ammonia is 12.3-15.9 nm, which is reduced by 1.4-3.4 nm compared with that before the reaction, and the successful etching of the AgCl shell layer by ammonia is verified.

FIG. 9 shows a graph of the reaction time of the Au @ Ag @ AgCl nanoparticle probe of the invention in the process of detecting ammonia gas and the variation of the absorbance of the characteristic peak in the ultraviolet-visible absorption spectrum. As shown in the figure, under three ammonia gas concentrations (200 muM, 1000 muM and 2000 muM), the change value of the characteristic peak absorbance of the Au @ Ag @ AgCl nano particle probe reaches the maximum at about 10min and does not change any more. Therefore, the reaction time of the Au @ Ag @ AgCl nanoparticle probe for detecting ammonia gas is set to be 10 min.

FIG. 10 shows a graph of the change of the pH value of the solution to the absorbance of a characteristic peak in an ultraviolet-visible absorption spectrum in the process of detecting ammonia gas by using the Au @ Ag @ AgCl nanoparticle probe of the invention. As shown in the figure, in the ammonia gas concentration range of 0-2000 mu M, the change value of the absorbance of the characteristic peak of the Au @ Ag @ AgCl nanoparticle probe is gradually obvious along with the increase of the ammonia gas concentration under the influence of pH, and the change value of the absorbance under the condition that the pH is 8 is more obvious. Therefore, the pH value of the Au @ Ag @ AgCl nanoparticle probe for detecting ammonia gas is set to be 8.

The following examples are provided to examine the performance of the method in detail.

Example 1: the detection effect of the Au @ Ag @ AgCl nanoparticle probe prepared by the invention on ammonia water solutions with series concentrations is given in the following. Preparing ammonia water solutions (0-5000 mu M) with a series of concentrations, adding the Au @ Ag @ AgCl nano particle probe solution, reacting for 10min at room temperature (25 +/-2 ℃), and then photographing and scanning an ultraviolet-visible absorption spectrum. FIG. 11(a) shows that when the ammonia water is in the range of 0-1600 μ M, the absorbance value of the characteristic absorption peak of the Au @ Ag @ AgCl nanoparticle probe solution at 510nm is gradually increased along with the increase of the ammonia water concentration, and the change value of the absorbance and the ammonia water concentration present a good linear relationship (FIG. 11(b)), the linear correlation coefficient reaches 0.997, and the lowest detection concentration is calculated to be 6.4 μ M according to the linear equation; FIG. 12(a) shows that when the ammonia water is in the range of 1800-5000 μ M, the absorbance value of the characteristic absorption peak of the Au @ Ag @ AgCl nanoparticle probe solution at 510nm is gradually reduced along with the increase of the ammonia water concentration, the absorption peak is slightly red-shifted, the change value of the absorbance and the ammonia water concentration show a good linear relationship (FIG. 12(b)), and the linear correlation coefficient reaches 0.991, which indicates that the method can be used for the quantitative detection of the ammonia water.

Example 2: the following is a comparison of the response effect of the Au @ Ag @ AgCl nanoparticle probe embodiments of the present invention on ammonia gas and other 10 interfering reagents/gases. FIG. 13 shows that the response signal of the Au @ Ag @ AgCl nanoparticle probe provided by the invention to ammonia gas is 8.12-139 times that of all other 10 interference reagents/gases, which indicates that the method has high specificity to ammonia gas.

Example 3: the following provides an example of detecting an actual gas sample by using the Au @ Ag @ AgCl nanoparticle probe of the invention. In order to test the feasibility of the method for detecting the content of the ammonia gas in the actual sample, the method is applied to the detection of the content of the ammonia gas in the simulated polluted gas. An aqueous ammonia solution (9mM, 10mL) was injected into a constant volume (20L) gas sampling bag, which was then filled with air by an air pump to prepare a contaminated gas. It was then divided into 4 gas sampling bags (5 liters) for use. Four further gas sampling bags (5 liters) were used to collect fresh air. Various amounts of aqueous ammonia solution standard solutions (0.17, 0.34, 0.51, 0.68, 1.02mg/L) were injected into the gas sampling bags, respectively. Prior to analysis, the air sampling bag was heated to 50 ℃ to ensure uniform diffusion of ammonia gas. Gas samples of varying concentrations were drawn into 20mL medical syringes into which 5mL of Au @ Ag @ AgCl nanoparticle probe solution was previously introduced. After incubation at room temperature (25. + -. 2 ℃ C.) for 10 minutes, UV-visible absorption spectra were obtained using a spectrophotometer (see FIG. 14), and the respective recoveries were calculated. As shown in Table 1, the normalized recovery rates of the clean air and the simulated polluted air samples are between 108.3% and 122.2%, and the standard deviation is between 3.4% and 5.2%, which indicates that the established method can meet the detection requirement of the ammonia gas in the gas samples.

TABLE 1 Process of the invention for the recovery of gas samples containing ammonia at different concentrations with a standard addition

The ammonia colorimetric detection method based on the Au @ Ag @ AgCl nanoparticle probe provided by the invention has the following characteristics:

1) the synthesized Au @ Ag @ AgCl nanoparticles have the advantages of uniform appearance, controllable size, strong stability and the like.

2) Compared with other colorimetric methods, the method for colorimetric detection of ammonia gas based on Au @ Ag @ AgCl nanoparticles has the advantages of high sensitivity, good selectivity and high response speed, and can realize real-time, rapid and semi-quantitative detection of ammonia gas concentration by naked eyes.

3) The method for colorimetric detection of ammonia gas based on Au @ Ag @ AgCl nanoparticles has the advantages of strong anti-interference capability, simplicity in operation and high practical application value, and can realize accurate quantitative detection of complex gas samples such as ambient air, polluted gas and the like.

Claims

1. A method for preparing an Au @ Ag @ AgCl nanoparticle probe is characterized by comprising the steps of preparing spherical nanoparticles with a three-layer core-shell structure, wherein Au is a core and the diameter of the Au is 12.9-13.5 nm; ag is an inner shell with the thickness of 1.6-4.6 nm; the AgCl is an outer shell and the thickness is 0.7-2.3 nm.

2. The Au @ Ag @ AgCl nanoparticle probe of claim 1, wherein the Au @ Ag @ AgCl nanoparticle probe has a particle size of 15.7-17.3 nm.

3. The method of making an Au @ Ag @ AgCl nanoparticle probe of claim 1, comprising the steps of:

1) preparing an Au nanoparticle solution: HAuCl is added into a three-neck flask in sequence₄The solution and water were heated under reflux and stirred. The sodium citrate solution was then added and heating continued for a period of time. The solution quickly turns purple black from the original light yellow, is finally stabilized to wine red, and is cooled to room temperature to obtain Au nano-particle solution;

2) preparing Au @ Ag nanoparticle solution: sequentially adding the following components into a three-neck flask: and (2) stirring the Au nanoparticle solution obtained in the step 1) and water. Then quickly adding ascorbic acid solution and AgNO at one time₃Solutions and NaOH solutions. Stirring the mixture to continue reacting for a period of time, centrifuging at a certain speed and for a certain period of time, removing the supernatant, dispersing into water, and obtaining a yellow solution of Au @ Ag nano particles;

3) preparing an Au @ Ag @ AgCl nanoparticle probe solution: toAdding the following components in sequence in a glass bottle: au @ Ag nano particle solution and FeCl obtained in step 2)₃And (3) reacting the solution, and finally obtaining the Au @ Ag @ AgCl core-shell nanoparticle probe solution, wherein the mixed solution is orange yellow.

4. The method for preparing the Au @ Ag @ AgCl nanoparticle probe of claim 3, wherein in the step 1), the HAuCl is adopted₄The volume ratio of the solution, water and the sodium citrate solution is 5 mL: 95mL of: 10 mL; the HAuCl₄The solution adopts HAuCl with the molar concentration of 0.02428mol/L₄A solution; the water can adopt ultrapure water; the sodium citrate solution is 11.46 mg/mL.

5. The method of making an Au @ Ag @ AgCl nanoparticle probe of claim 3, wherein in step 1), the reflux heating temperature is 400 ℃; the heating time is 15min, and the obtained Au nanoparticles are Au nanoparticles with the diameter of 12.9-13.5 nm.

6. The method for preparing the Au @ Ag @ AgCl nanoparticle probe of claim 3, wherein in the step 2), the Au nanoparticle solution, water, ascorbic acid solution and AgNO are added₃The volume ratio of the solution to the NaOH solution can be 10 mL: 40mL of: 120 μ L of: (60-90) μ L: (225-450) μ L, preferably 10 mL: 40mL of: 120 μ L of: 75 μ L of: 225 μ L; the water can adopt ultrapure water; the ascorbic acid solution is 100mM in molar concentration; the AgNO₃The solution adopts AgNO with the molar concentration of 100mM₃A solution; the NaOH solution adopts a NaOH solution with the molar concentration of 100 mM.

7. The method for preparing the Au @ Ag @ AgCl nanoparticle probe as claimed in claim 3, wherein in the step 2), the reaction time is 30 min; the centrifugal speed can be 6000-10000 rpm, preferably 8000 rpm; the centrifugation time can be 10-30 min, and preferably 20 min; the volume of the water for dispersing can be 50mL, and the obtained Au @ Ag nano particles are Au @ Ag nano particles with the diameter of 13.8-16.2 nm.

8. The method for preparing the Au @ Ag @ AgCl nanoparticle probe of claim 3, wherein in the step 3), the Au @ Ag nanoparticle solution and FeCl are added₃The volume ratio of the solution may be 1 mL: (6-18) μ L, preferably 1 mL: 12 mu L of the solution; the FeCl₃The molar concentration of the solution is 10mM, and the obtained Au @ Ag @ AgCl nano particle probe is Au @ Ag @ AgCl nano particles with the diameter of 15.7-17.3 nm.

9. The use of the Au @ Ag @ AgCl nanoparticle probe of claim 1 in the colorimetric detection of ammonia gas.

10. The use according to claim 9, characterized in that the specific method is as follows: