CN108356277B

CN108356277B - Preparation method of gold nanorods

Info

Publication number: CN108356277B
Application number: CN201810157626.1A
Authority: CN
Inventors: 李东升; 张汉杰; 杨德仁
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2018-02-24
Filing date: 2018-02-24
Publication date: 2020-08-11
Anticipated expiration: 2038-02-24
Also published as: CN108356277A

Abstract

The invention discloses a preparation method of gold nanorods, which comprises the following steps: (1) mixing cetyl trimethyl ammonium bromide and oleate to prepare a solution, sequentially adding a soluble silver ion solution and an HAuCl4 aqueous solution to obtain a growth solution, and equally dividing the growth solution into at least two parts; (2) quickly adding a NaHB4 aqueous solution into one part of the growth solution obtained in the step (1), quickly stirring and standing to obtain a gold seed solution; (3) adding an acid solution and an ascorbic acid solution into the other growth solutions in the step (1), quickly adding the gold seed solution in the step (2) after stirring, and standing after stirring; the invention simplifies the preparation process of gold seed solution and improves the process efficiency; oleate is introduced in the whole preparation process, the use of a highly toxic ligand Cetyl Trimethyl Ammonium Bromide (CTAB) is reduced, the toxicity is reduced, and the production cost is also saved.

Description

Preparation method of gold nanorods

Technical Field

The invention relates to the field of manufacturing of gold nanorods, in particular to a preparation method of the gold nanorods.

Background

Gold nanorods have wide applications in many fields. Such as: in the aspect of medical diagnosis and treatment, the gold nanorods have the advantages of stable property, adjustable optical property, easy surface functionalization and the like, and can be used as a platform to form a biomolecule detection or medical imaging reagent together with a plurality of fluorescent structures. In addition, the gold nanorods have wide application in aspects of drug delivery, photothermal therapy and the like, and the development of precise medical treatment is promoted.

In the aspect of molecular probes, as the resonance peak of the gold nanorod is in the near-back outer region, the scattering signal is also in the near-infrared region, the characteristic that infrared rays easily penetrate through biological tissues can be utilized to obtain a Raman signal with high signal-to-noise ratio, and the established molecular probe has many applications in many detection aspects. The surface enhanced Raman effect can realize the enhancement of Raman signals in the near infrared region.

In the aspect of sensors, the gold rod can be coupled with a Fluorescence Resonance Energy Transfer (FRET) phenomenon, so that the energy Transfer range is further improved, and the application range of the sensors can be widened by combining the sensitivity of energy Transfer to distance and the surface plasmon polariton enhancement effect of the gold rod.

In conclusion, the research on the preparation of the gold rod has great significance. There are also various methods for producing gold rods in the prior art, and for example, patent document CN104707998B discloses a method for producing gold rodsA nano gold bar coated with fluorescent dye, having a core-shell structure and used for detecting bovine serum albumin, a preparation method and application thereof, firstly, NaBH is utilized₄Reducing HAuCl in CTAB solution with certain concentration₄Obtaining gold seeds, adding silver nitrate into a system containing CTAB and sodium oleate, standing, and adding HAuCl₄And then adding ascorbic acid, finally adding the gold seeds obtained before, and growing overnight to finally obtain the gold nanorods with uniform appearance.

For another example, patent document CN 104907578A discloses a method for preparing gold nanorods, and belongs to the field of nano material preparation. The method of the invention comprises the following steps: step one, preparing a mixed solution of quaternary ammonium bromide salt, oleate, tetrachloroauric acid, silver nitrate, an acid solution and ascorbic acid to obtain a growth solution; reducing tetrachloroauric acid by using a strong reducing agent sodium borohydride in a hexadecyl trimethyl ammonium bromide surface modifier solution to obtain a gold seed solution; and step three, injecting the gold seed solution into the growth solution, and reacting for 3-15 hours to obtain the gold nanorods. The method has the advantages of low equipment requirement, simple method operation, mild condition and high reproducibility, and can be used for mass preparation.

However, the preparation method in the prior art has the disadvantages of relatively independent steps, low preparation efficiency and excessive dosage of the highly toxic ligand Cetyl Trimethyl Ammonium Bromide (CTAB).

Disclosure of Invention

The invention provides a preparation method of gold nanorods, which simplifies the preparation process and the dosage of toxic ligands and effectively improves the process efficiency.

A preparation method of gold nanorods comprises the following steps:

(1) mixing cetyl trimethyl ammonium bromide and oleate to prepare a solution, sequentially adding a soluble silver ion solution and an HAuCl4 aqueous solution to obtain a growth solution, and equally dividing the growth solution into at least two parts;

(2) quickly adding a NaHB4 aqueous solution into one part of the growth solution obtained in the step (1), quickly stirring and standing to obtain a gold seed solution;

(3) and (3) adding an acid solution and an ascorbic acid solution into the other growth solutions in the step (1), stirring, quickly adding the gold seed solution in the step (2), stirring, and standing.

According to the invention, oleate is introduced into the whole process (steps 1-3) of preparing the gold rod, so that the preparation process of the alloy seed solution and the growth solution can be effectively completed, the step 2 is simplified, cetyl trimethyl ammonium bromide and oleate do not need to be repeatedly weighed and added, and the preparation efficiency is improved; on the other hand, the gold seed solution is also added with sodium oleate, so that the use of a highly toxic ligand Cetyl Trimethyl Ammonium Bromide (CTAB) is reduced, the toxicity is reduced, and the production cost is also saved.

The coordination capacity of the oleate radical and gold is stronger than that of hexadecyl trimethyl ammonium bromide, so that after oleate is added, on one hand, the use amount of a highly toxic substance, namely hexadecyl trimethyl ammonium bromide, is reduced; on the other hand, the uniformity of the gold rod is improved. Preferably, the oleate is sodium oleate or potassium oleate.

Silver ions can be adsorbed on a specific gold surface to help the gold solution directionally grow into a gold rod, and preferably, the soluble silver ion solution is silver nitrate solution.

The acid solution can realize effective adjustment of pH, and further influences the wrapping state of the oleate and the hexadecyl trimethyl ammonium bromide in the solution, and preferably, the acid solution is concentrated hydrochloric acid.

Preferably, the step (1) specifically comprises the following steps:

1-1, 0.21-0.43 g CTAB and 0.04-0.062 g sodium oleate are dissolved in 5-20 mL of water at 50-70 ℃, and cooled to 10-30 ℃;

1-2, sequentially adding 0.12-1.92 mL of 4mM silver nitrate aqueous solution and 5-15 mL of 1mM HAuCl₄Water solution to obtain growth solution;

1-3, dividing the obtained growth solution into 2-5 parts. The flow of gold seed re-preparation can be reduced.

Preferably, the step (2) specifically comprises the following steps:

2-1, quickly adding 0.5-2 mL of 0.006M NaHB into one part of the growth solution in the step (1)₄Rapidly stirring for 2-5 minutes;

2-2, standing for 30 minutes to prepare the gold seed solution. And in the standing process, the prepared gold rod is more uniform.

Preferably, the step (3) specifically comprises the following steps:

3-1, after 1.5h in the step (1), adding 0.03-0.056 mL of 37% concentrated hydrochloric acid into the other part of the growth solution;

adding 5-50 mu L of 0.045M ascorbic acid solution after 3-2 min and 15 min;

and (3) quickly adding 0.006-0.08 mL of the gold seed solution obtained in the step (2) after 3-3 s and 30s, and standing to obtain the gold nanorods. Compared with the method for synthesizing the gold rod at one time, the prepared gold rod has higher uniformity due to the uniform nucleation center and one-time addition.

Preferably, in step 3-3, the mixture is allowed to stand at room temperature for 12 hours or more. The reaction time is long enough, the concentration of gold particles in the solution can be ensured, the equilibrium concentration of the reaction is reduced, and the raw materials are effectively utilized.

The invention has the beneficial effects that:

(1) the preparation process of the gold seed solution is simplified, and the process efficiency is improved.

(2) Oleate is introduced in the whole preparation process, the use of a highly toxic ligand Cetyl Trimethyl Ammonium Bromide (CTAB) is reduced, the toxicity is reduced, and the production cost is also saved.

Drawings

FIGS. 1 to 4 are scanning electron micrographs of gold rods produced in example 1 under four different gold seed volumes.

FIG. 5 shows the absorption spectra of the gold rods prepared in example 1 for different volumes of gold species.

FIG. 6 is a scanning electron micrograph of a long gold rod prepared in example 2.

FIG. 7 is an absorption spectrum of a long gold rod in example 2.

Detailed Description

The present invention will be described in detail with reference to examples. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

In the following examples, the raw materials are commercially available and are not described in detail.

Example 1

The preparation method of the gold nanorods comprises the following steps:

(1) a growth solution was prepared by dissolving 0.7g cetyltrimethylammonium bromide (CTAB), 0.155g sodium oleate (NaOL) in 25mL water, sequentially adding 0.6mL of 4mM silver nitrate aqueous solution, 25mL of 1mM HAuCl₄Water solution, and dividing the growth solution into 5 parts;

(2) preparing gold seed solution, and adding 1mL of 0.006M NaHB to one part of the solution in step (1) rapidly₄Rapidly stirring for 2 minutes, and standing for 30 minutes to obtain a gold seed solution;

(3) after 1.5h, 0.042mL of 37% concentrated hydrochloric acid is added to the other 4 growth solutions obtained in the step (1), 25 μ L of 0.045M Ascorbic Acid (AA) solution is added after 15min, 0.006mL, 0.012mL, 0.024mL and 0.040mL of gold seed solution are added rapidly after 30s, and the mixture is allowed to stand at room temperature for 12h to obtain Gold Nanorods (GNR) with single distribution.

Example 2

The preparation method of the gold nanorods comprises the following steps:

(1) a growth solution was prepared by dissolving 0.28g of cetyltrimethylammonium bromide (CTAB), 0.062g of sodium oleate (NaOL) in 10mL of water, followed by 0.96mL of 4mM silver nitrate aqueous solution, 10mL of 1mM HAuCl₄Water solution, dividing the growth solution into 2 parts;

(3) after 1.5h, respectively adding 0.06mL of 37% concentrated hydrochloric acid to the other solution obtained in the step (1), after 15min, respectively adding 25 μ L of 0.045M Ascorbic Acid (AA) solution, after 30s, respectively adding 0.080mL of gold seed solution quickly, and standing at room temperature for 12h to obtain Gold Nanorods (GNR) with single distribution.

FIGS. 1 to 4 are scanning electron micrographs of gold nanorods prepared in example 1, and gold nanorods with different aspect ratios and single distribution were prepared by changing the volume of the gold seed solution, and the gold nanorods were prepared by adding 0.006mL, 0.012mL, 0.024mL, and 0.040mL of the gold seed solution, respectively.

FIG. 5 shows the absorption peaks corresponding to the gold rod at 660nm, 673nm, 685nm and 724nm for different gold seed solution volumes, so that the length-diameter ratio of the gold rod is longer and the absorption peak is red-shifted with the increase of the gold seeds.

FIG. 6 shows that the length-diameter ratio of the gold rod obtained according to the parameters in the preparation method of example 2 is relatively long, and therefore, the improvement method can also obtain the gold rod with large length-diameter ratio.

FIG. 7 shows the absorption spectrum of the gold rod obtained by the preparation method of example 2, from which the LSPR peak is about 853 nm.

Claims

1. A preparation method of gold nanorods is characterized by comprising the following steps:

step (1):

1-3, dividing the obtained growth solution into 2 parts;

step (2):

2-1, quickly adding 0.5-2 mL of 0.006M NaBH into one part of the growth solution in the step (1)₄Rapidly stirring for 2-5 minutes;

2-2, standing for 30 minutes to prepare a gold seed solution;

and (3):

adding an acid solution and an ascorbic acid solution into the other growth solutions in the step (1), quickly adding the gold seed solution in the step (2) after stirring, and standing after stirring;

the acid solution is concentrated hydrochloric acid.

2. The method for preparing gold nanorods according to claim 1, wherein the step (3) specifically comprises the steps of:

adding 5-50 mu L of 0.045M ascorbic acid solution after 3-2 min and 15 min;

and (3) quickly adding 0.006-0.08 mL of the gold seed solution obtained in the step (2) after 3-3 s and 30s, and standing to obtain the gold nanorods.

3. The method for preparing gold nanorods according to claim 2, wherein, in step 3-3, the gold nanorods are allowed to stand at room temperature for more than 12 hours.