CN113319275A

CN113319275A - Au @ AgNRs nanorod as well as preparation method and application thereof

Info

Publication number: CN113319275A
Application number: CN202110401521.8A
Authority: CN
Inventors: 胡睿; 刘靖康; 吕云杰; 莫振豪; 刘丽炜; 屈军乐
Original assignee: Shenzhen University
Current assignee: Shenzhen University
Priority date: 2021-04-14
Filing date: 2021-04-14
Publication date: 2021-08-31
Anticipated expiration: 2041-04-14
Also published as: CN113319275B

Abstract

The invention belongs to the technical field of thiram detection, and particularly relates to an Au @ AgNRs nanorod as well as a preparation method and application thereof. The method comprises the steps of adding ascorbic acid, silver nitrate solution and sodium hydroxide solution into gold nanorods, obtaining silver-plated gold nanorods after primary silver plating, and obtaining Au @ AgNRs nanorods after chloroplatinic acid etching and secondary silver plating. The outer layer of the silver-plated gold nanorod is etched by chloroplatinic acid, a shell with a rough surface is formed, the surface of the outer layer becomes extremely irregular, after silver plating is performed again, the contact area of the core-shell structure is indirectly increased, more 'hot spots' occur, a stronger electromagnetic field is generated, the surface Raman effect of the nanorod is remarkably enhanced, and the nanorod can be better applied to Raman imaging or Raman sensing and other applications. The Au @ AgNRs nanorod prepared by the method can be used for qualitative or quantitative detection of thiram.

Description

Au @ AgNRs nanorod as well as preparation method and application thereof

Technical Field

The invention belongs to the technical field of thiram detection, and particularly relates to an Au @ AgNRs nanorod as well as a preparation method and application thereof.

Background

Raman spectroscopy has been widely used in many fields, such as biomedicine, material science, environmental science, physics, etc., as a very potential analytical tool. With the research, researchers obtain a surface enhanced raman scattering spectrum (SERS) on the rough mercury electrode for the first time, and then adsorb a single layer of pyridine molecules on the surface of the rough silver electrode to obtain a high-quality raman scattering spectrum, so that the raman scattering intensity is greatly enhanced, the sensitivity of raman detection is greatly improved, and even the detection level of single molecules can be reached, so that the raman spectrum becomes one of the widely applied spectroscopy technologies. SERS as an analytical detection tool has the characteristics of high sensitivity, high selectivity and the like, so that the SERS is widely applied to the fields of biomedicine, environment, food safety, catalysis and the like.

In recent years, the application of the core-shell structure of Au core-Ag shell (Au @ AgNRs) in sensing has been advanced, and has attracted more and more attention. The Au @ AgNRs structure has excellent adjustable optical characteristics and can be widely applied to various fields such as scattering optical imaging, surface enhanced Raman, colorimetric sensing and the like. The Raman enhancement effect of Au @ AgNRs is much stronger than that of gold nanorods, but the enhancement effect on certain organic compounds is not obvious, such as thiram, peroxide and the like. Chinese patent document CN106404765A discloses a method for preparing silver-coated gold nanorod colorimetric probes and a method for detecting copper ions, which is a detection method for copper ions and cannot effectively detect organic matters. In addition, the method for detecting the organic matters in the prior art is greatly changed by factors such as illumination, temperature and the like, and has poor stability and reliability.

Disclosure of Invention

Therefore, the invention aims to overcome the defects that the enhancement effect of Au @ AgNRs on Raman signals of thiram is poor, the Raman detection result is greatly influenced by factors such as environment and the like in the prior art, and provides the Au @ AgNRs nanorod and the preparation method and application thereof.

Therefore, the invention provides the following technical scheme.

The invention provides a preparation method of an Au @ AgNRs nanorod, which comprises the following steps,

(1) sequentially adding ascorbic acid, silver salt solution and alkali solution into the gold nanorods for reaction, and obtaining silver-plated gold nanorods after primary silver plating;

(2) and etching the silver-plated gold nanorods by a chloroplatinic acid solution, sequentially adding ascorbic acid, a silver salt solution and an alkali solution for reaction, and plating silver for the second time to obtain the Au @ AgNRs nanorods.

Further, the concentration of the chloroplatinic acid solution is 0.04-0.08ml/L, and the volume is 180-220 mu L.

In the step (1), the concentration of the ascorbic acid is 0.08-0.12mol/L, and the volume is 80-120 mu L; the concentration of the silver salt is 1.8-2.2mmol/L, and the volume is 180-220 mu L; the concentration of the alkali solution is 0.08-0.13mol/L, and the volume is 80-110 mu L;

in the step (2), the concentration of the ascorbic acid is 0.08-0.12mol/L, and the volume is 80-120 mu L; the concentration of the silver salt is 0.8-1.2mmol/L, and the volume is 70-90 mu L; the concentration of the alkali solution is 0.08-0.13mol/L, and the volume is 80-110 mu L.

Further, the silver salt solution is a silver nitrate solution, and the alkali solution is a sodium hydroxide solution;

in the step (1), ascorbic acid is sequentially added and then reacts for 1-2min, silver salt solution is added and reacts for 1-2min, and alkali solution is added and reacts for 1-2 min;

in the step (2), the ascorbic acid is sequentially added and then reacts for 1-2min, the silver salt solution is added and reacts for 1-2min, and the alkali solution is added and reacts for 1-2 min.

Furthermore, the absorption peak value of the gold nanorod at the ultraviolet spectrum of 730nm is 0.8-1.1.

In the step (1), the gold nanorods are prepared by a seed-mediated growth method.

The invention also provides the Au @ AgNRs nanorod prepared by the method.

The invention also provides application of the Au @ AgNRs nanorod etched by the chloroplatinic acid in detecting the thiram.

In addition, the invention also provides a method for detecting thiram by using the Au @ AgNRs nanorod or the Au @ AgNRs nanorod prepared by the method, which comprises the steps of adding the Au @ AgNRs nanorod into liquid to be detected to obtain a Raman signal and qualitatively or quantitatively detecting the thiram.

Further, a standard curve is established for quantitative detection, the quantitative detection comprises the following steps,

preparing thiram solutions with different concentrations, measuring Raman signals, taking the absolute value of logarithm of the concentration of the thiram solution as an abscissa, and obtaining the thiram Raman signal of 558cm^-1And (4) performing linear fitting by taking the peak value as a vertical coordinate to obtain a linear equation y which is 7477.2-572.5x, wherein the linear correlation coefficient is 0.99, and the linear equation is used for quantitatively detecting thiram.

The detection range of thiram is as follows: 10^-4-10^-6mol/L。

The technical scheme of the invention has the following advantages:

1. the preparation method of the Au @ AgNRs nanorod provided by the invention comprises the steps of adding ascorbic acid, silver nitrate solution and sodium hydroxide solution into a gold nanorod, carrying out primary silver plating to obtain a silver-plated gold nanorod, and carrying out chloroplatinic acid etching and secondary silver plating to obtain the Au @ AgNRs nanorod. The outer layer of the silver-plated gold nanorod is etched by chloroplatinic acid, a shell with a rough surface is formed, the surface of the outer layer becomes extremely irregular, after silver plating is performed again, the contact area of the core-shell structure is indirectly increased, more 'hot spots' occur, a stronger electromagnetic field is generated, the surface Raman effect of the nanorod is remarkably enhanced, and the nanorod can be better applied to Raman imaging or Raman sensing and other applications. The Au @ AgNRs nanorod prepared by the method can be used for qualitative or quantitative detection of thiram. The chloroplatinic acid is used for etching and improving the silver-plated gold nanorods, so that the effect of the new material on enhancing the thiram Raman signals becomes more obvious, and the detection limit is further improved.

When the Au @ AgNRs nanorod prepared by the invention is applied to Raman imaging or Raman sensing, the influence of external uncertain factors such as temperature, illumination and the like can be eliminated, and the repeatability, stability and reliability of a detection result are improved.

2. The chloroplatinic acid etched Au @ AgNRs nanorod provided by the invention is applied to detection of thiram, and the core-shell nano material plated with silver after chloroplatinic acid etching enhances the surface Raman enhancement effect, and can be used for quantitatively analyzing the concentration of thiram.

3. According to the method for detecting thiram, the Au @ AgNRs nanorod provided by the invention can be used for qualitatively or quantitatively analyzing the existence or the content of thiram in a substance to be detected. The detection method is less influenced by the outside, is not influenced by factors such as temperature, illumination and the like, has good repeatability, stability and reliability of detection results, is simple to operate and does not need expensive test equipment.

The "hot spot" mentioned above means that in SERS enhanced electromagnetic field enhancement, the enhancement effect of SERS is approximately proportional to the fourth power of the local electric field intensity, and most importantly, the electromagnetic field enhancement around the metal nanoparticle material is not uniformly distributed, but highly localized in a narrow spatial region, and these local regions with strong electromagnetic enhancement are called "SERS hot spots".

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a TEM image of gold nanorods in example 1 of the invention;

FIG. 2 is a TEM image of gold nanorods after primary silver plating in example 1 of the present invention;

FIG. 3 is a graph of the UV-VIS absorption spectrum of gold nanorods in example 1 of the invention;

FIG. 4 is a diagram showing an ultraviolet-visible absorption spectrum of gold nanorods after primary silver plating in example 1 of the present invention;

FIG. 5 is a TEM image of the nanorods after chloroplatinic acid etching in example 1 of the present invention;

FIG. 6 is a graph of the UV-VIS absorption spectra of nanorods after chloroplatinic acid etching of the silver layer and secondary silver plating in example 1 of the present invention;

FIG. 7 is a graph showing UV-VIS absorption spectra of nanorods obtained in examples 1 and 2-4 of the present invention;

FIG. 8 shows Raman signals of nanorods of examples 1 and 5-6 of the present invention;

FIG. 9 shows Raman signals of different thiram concentrations in example 7 of the present invention;

FIG. 10 is a fitted line equation according to example 7 of the present invention;

FIG. 11 is Raman signals of nanorods of example 1 and comparative example 1 of the present invention.

Detailed Description

The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.

The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.

Example 1

The embodiment provides a preparation method of an Au @ AgNRs nanorod, which comprises the following steps,

(1) preparing a seed solution of gold nanorods: CTAB stored at room temperature and with a concentration of 0.2mol/L is heated in a water bath to 55 ℃ to obtain a clear and transparent CTAB solution. The stirrer was washed clean with deionized water and placed in a 30ml glass bottle, then 5ml of chloroauric acid with a concentration of 0.5mmol/L was added to the glass bottle, 5ml of CTAB with a concentration of 0.2mol/L was added, and stirring was carried out at 1000rpm for 3min, whereupon the seed solution changed from pale yellow to bright yellow. And then preparing a fresh sodium borohydride solution, dissolving 0.004g of sodium borohydride in 10ml of 0 ℃ ice water, fully dissolving the sodium borohydride, adding 0.6ml of sodium borohydride solution into a glass bottle, keeping the rotation speed of 1200rpm for vigorous stirring in the process of adding the sodium borohydride, changing the seed solution from bright yellow to bright brown, continuously stirring for 3min, and standing the seed solution for 30min for later use. Taking a 5-bromosalicylic acid system as an example to prepare a growth solution, washing a stirrer well with deionized water, placing the washed stirrer in a 1000ml glass bottle, adding 100ml of deionized water into the glass bottle, heating the glass bottle in a water bath to 55 ℃, then dissolving 3.6g of CTAB in 100ml of deionized water with the temperature of 55 ℃, after the CTAB is fully dissolved, adding 0.45g of 5-bromosalicylic acid, keeping the rotating speed of the whole process at 800rpm until the solution becomes clear and transparent, then cooling the solution to room temperature, adding 1.5ml of silver nitrate with the concentration of 20mmol/L, fully stirring the silver nitrate, placing the silver nitrate at the room temperature for 15 minutes, adding 100ml of chloroauric acid with the concentration of 1mmol/L, changing the colorless and transparent solution to orange, then adding 0.8ml of ascorbic acid with the concentration of 0.1mol/L, and vigorously stirring the solution until the solution changes from orange to colorless. Finally, adding 0.32ml of seed solution into the growth solution, violently stirring for 15min, placing in a water bath kettle at the temperature of 35 ℃ for overnight growth, and preparing gold nanorods; the TEM electron micrograph of the gold nanorods is shown in FIG. 1, and the ultraviolet visible absorption spectrum is shown in FIG. 3.

Taking 0.5ml of centrifuged gold nanorods, dispersing the gold nanorods in 1.5ml of deionized water, adding 0.1 mol/L100 mu L of ascorbic acid into the nanorods to react for 2min under the condition of normal temperature, adding 2 mmol/L200 mu L of silver nitrate solution to react for 2min, and then adding 0.1 mol/L100 mu L of sodium hydroxide solution to react for 2min to obtain silver-plated gold nanorods; wherein, a TEM electron micrograph of the silver-plated gold nanorods is shown in figure 2, and an ultraviolet visible absorption spectrum is shown in figure 4, which shows that the silver plating of the gold nanorods is completed.

(2) And centrifuging the prepared gold nanorods, dispersing the gold nanorods to 2ml again to form silver-plated gold nanorod solution, adding the silver-plated gold nanorods into 0.08 ml/L200 mu L chloroplatinic acid to etch the silver layer, centrifuging the etched silver-plated gold nanorods, and continuously dispersing the gold nanorods to 2ml after the centrifugation is finished to form the etched silver-plated gold nanorod solution. Sequentially adding 0.1 mol/L100 mu L ascorbic acid for reaction for 2min, then adding 1 mmol/L80 mu L silver nitrate solution for reaction for 2min, then adding 0.1 mol/L100 mu L sodium hydroxide solution for reaction for 2min, and obtaining the Au @ AgNRs nano rod after secondary silver plating; the TEM electron microscope image of the nanorods after chloroplatinic acid etching is shown in FIG. 5, and the ultraviolet visible absorption spectrum of the nanorods after chloroplatinic acid etching of the silver layer and secondary silver plating is shown in FIG. 6.

Example 2

The difference between the present example and example 1 is that the concentration of chloroplatinic acid is different, and the concentration of chloroplatinic acid in the present example is 0.04 ml/L.

Example 3

The difference between the present example and example 1 is that the concentration of chloroplatinic acid is different, and the concentration of chloroplatinic acid in the present example is 0.02 ml/L.

Example 4

The difference between the present example and example 1 is that the concentration of chloroplatinic acid is different, and the concentration of chloroplatinic acid in the present example is 0.01 ml/L.

Example 5

The present example is different from example 1 in that the volume of the silver nitrate solution in the second silver plating is different, and the volume of the silver nitrate solution in the present example is 50. mu.L.

Example 6

The present example is different from example 1 in that the volume of the silver nitrate solution in the second silver plating is different, and the volume of the silver nitrate solution in the present example is 30. mu.L.

Test example 1

In the present test example, ultraviolet-visible absorption spectrograms of nanorods obtained at different concentrations of chloroplatinic acid (example 1, example 2-4) are studied, and as shown in fig. 7 (in fig. 7, c is the gold nanorod after primary silver plating, d is the gold nanorod obtained in example 4, e is the gold nanorod obtained in example 3, f is the gold nanorod obtained in example 2, g is the gold nanorod obtained in example 1, and h is the gold nanorod), it is demonstrated that chloroplatinic acid has an etching effect on the silver layer, and the etching effects at different concentrations are different.

This experimental example investigated the effect of the amount of silver nitrate solution (examples 1, 5-6) for secondary silver plating on the raman signal of nanorods, see fig. 8. From FIG. 8, it can be illustrated that when the silver nitrate concentration is 1mmol/L and the volume is 80 μ L, the obtained nanorods can obtain the strongest Raman signal, which illustrates that in the secondary silver plating, the concentration and volume of silver nitrate are larger for the nanorod Raman signal, and a silver nitrate solution with a specific concentration and volume is helpful for enhancing the Raman signal.

Comparative example 1

The difference between the comparative example and the example 1 is that the nanorods were obtained after the primary silver plating was finished without chloroplatinic acid etching and secondary silver plating. The raman signals of the nanorods prepared in example 1 and comparative example 1 were measured, respectively, as shown in fig. 11, and the nanorods obtained without chloroplatinic acid etching had a weak raman signal.

Example 7

The embodiment provides a qualitative analysis method for thiram, and the Au @ AgNRs nanorod prepared in the embodiment 1 is adopted, and the detection method comprises the following steps,

the qualitative analysis method comprises the following steps: mixing the substance to be detected and the prepared material, and detecting Raman spectrum of thiram if the Raman spectrum is 558cm^-1The appearance of a Raman peak indicates that the object to be detected contains thiram.

The embodiment also provides a method for quantitative analysis of thiram, which comprises the following steps,

(1) formulation 10^-4mol/L、10^-5mol/L、10^-6And measuring the Raman signal of the thiram solution with mol/L, wherein the peak values of the raman signal 558 of the thiram solution with different concentrations are 5188, 4613 and 4043 respectively. The raman signals of thiram at different concentrations are shown in fig. 9.

(2) And taking the logarithmic absolute value of the concentration of the thiram solution as an abscissa, and performing linear fitting by taking the peak value of the thiram Raman signal 558 as an ordinate to obtain a linear equation y of 7477.2-572.5x, wherein the linear correlation coefficient is 0.99, so that a linear fitting curve is obtained, and the thiram solution can be used for quantitatively detecting thiram. The fitted line equation is shown in fig. 10, to quantitatively analyze thiram.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.

Claims

1. A preparation method of Au @ AgNRs nanorods is characterized by comprising the following steps,

2. The method as claimed in claim 1, wherein the concentration of the chloroplatinic acid solution is 0.04-0.08ml/L and the volume is 180-220. mu.L.

3. The production method according to claim 1 or 2, wherein in the step (1), the ascorbic acid has a concentration of 0.08 to 0.12mol/L and a volume of 80 to 120 μ L; the concentration of the silver salt is 1.8-2.2mmol/L, and the volume is 180-220 mu L; the concentration of the alkali solution is 0.08-0.13mol/L, and the volume is 80-110 mu L;

4. The production method according to any one of claims 1 to 3, wherein the gold nanorods have an absorption peak at 730nm of the ultraviolet spectrum of 0.8 to 1.1.

5. The production method according to any one of claims 1 to 4, wherein in the step (1), the gold nanorods are obtained by a seed-mediated growth method.

6. Au @ AgNRs nanorods prepared by the method of any one of claims 1-5.

7. The Au @ AgNRs nanorod subjected to chloroplatinic acid etching is applied to detection of thiram.

8. A method for detecting thiram by using the Au @ AgNRs nanorods prepared by the method of any one of claims 1 to 5 or the Au @ AgNRs nanorods of claim 6, which comprises adding the Au @ AgNRs nanorods to a solution to be detected to obtain a Raman signal, and qualitatively or quantitatively detecting thiram.

9. The method for detecting thiram according to claim 8, wherein a standard curve is established for quantitative detection, the quantitative detection comprising the steps of,

10. The method of claim 9, wherein thiram is detected in the range of: 10^-4-10^-6mol/L。