A method for preparing oleophilic gold nanorods

Abstract

The invention discloses a method for preparing an oleophilic gold nanorod, comprising the following steps: (1) preparing a gold nanorod dispersion by a seed method; (2) cleaning; (3) coating a silicon dioxide layer; (4) surface modification; and (5) cleaning and dispersing. The invention has simple process steps, strong operability, and a wide range of applications. Gold nanorods coated with silicon dioxide of different porosities can be surface modified. The prepared oleophilic gold nanorod material can retain the physical properties of the gold nanorod itself and can also be uniformly dispersed in an oily solvent, thereby broadening the application range of the gold nanorod.

Description

Technical Field

[0001] The invention relates to a photonic nanocrystal material, in particular to a method for preparing an oleophilic gold nanorod. Background Art

[0002] Nanomaterials have been the focus of research over the past few decades. Among them, precious metal nanomaterials, especially gold and silver nanoparticles, have extensive and in-depth applications in optics, medicine, sensing, imaging, etc. due to their unique localized surface plasmon properties based on shape and size. The prepared gold nanorod raw products usually need to undergo certain treatments. For example, surface modification, self-assembly, oxidation corrosion, core-shell coating, etc., in order to maintain its stability and application range in various physical and chemical environments, and expand in many aspects in different disciplines and project fields.

[0003] The original product is easily dispersed in aqueous solution due to the adsorption of CTAB on its surface. This special micelle environment enhances the stability of gold nanocrystals in extreme environments such as high-speed centrifugation and high conductivity. However, it is difficult for them to exist stably and evenly in oily solvents and function, which means they have limitations. Therefore, it is very necessary to further explore the modification and modification of gold nanorods so that they can be evenly dispersed and function in oily solutions. Summary of the invention

[0004] The purpose of the invention is to provide a method for preparing oleophilic gold nanorods with simple process steps and strong operability. The prepared oleophilic gold nanorod material can retain the physical properties of the gold nanorods themselves and can also be uniformly dispersed in oily solvents, thereby broadening the application range of the gold nanorods.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: A method for preparing lipophilic gold nanorods of the present invention comprises the following steps:

[0006] (1) Preparing gold nanorod dispersion by seed method;

[0007] (2) Cleaning

[0008] The gold nanorod dispersion is centrifuged, and the separated matter is dispersed in a 1-2 mM CTAB solution to obtain a gold nanorod concentrate. The concentration of gold nanorods in the gold nanorod concentrate is the same as that in the gold nanorod dispersion before centrifugation.

[0009] (3) Silicon dioxide coating

[0010] 0.4 mL of 0.2 M NaOH solution was added to the gold nanorod concentrate, and TEOS was added six times, 0.04 mL of TEOS was added each time, and the mixture was stirred for 30 minutes after each addition. After the sixth addition of TEOS, the mixture was stirred for 2 days to obtain a gold nanorod dispersion coated with silica. Due to the presence of CTAB, it is difficult to modify the gold nanorod raw material directly, so the silica coating layer was used for transition in the present invention, and the gold nanorods were grafted after being coated with silica; the NaOH solution was used as a catalyst to uniformly hydrolyze TEOS to form a uniform silica layer.

[0011] (4) Surface modification

[0012] After centrifuging the silica-coated gold nanorod dispersion, remove the supernatant, add 25 mL of ethanol to obtain the silica-coated gold nanorod ethanol dispersion; take 3 mL of the silica-coated gold nanorod ethanol dispersion, add 100 μL of 32 wt.% ammonia water and 500 μL of 2.4 wt.% OTMS chloroform solution in sequence, stir for 24 hours, and obtain the reaction product. After adding OTMS and ammonia water, the grafting is achieved through the hydrolysis of methoxyl groups in a weakly alkaline environment and the condensation of the obtained silanetriol with the surface Si-OH group, and OTMS is successfully modified on the gold nanorods, so that the gold nanorods show lipophilic properties.

[0013] (5) Cleaning and dispersion

[0014] The reaction product is centrifuged, the separated product is washed with ethanol, and then dispersed in cyclohexane to obtain the lipophilic gold nanorod material.

[0015] Preferably, in step (1), the specific steps of preparing the gold nanorod dispersion by the seed method are:

[0016] (a) Preparation of seed solution

[0017] After mixing 10 mL of 0.1 M CTAB solution and 0.25 mL of 10 mM HAuCl4 solution, add 0.3 mL of 0.02 M NaBH4 solution and stir vigorously until the color of the solution changes from golden yellow to brown yellow to obtain a seed solution.

[0018] (b) Preparation of Growth Solution

[0019] Dissolve 9.25 mL of 0.1 M CTAB solution and 0.062 g of NaOL in 14.5 mL of water, add 1.2 mL of 4 mM AgNO3 solution, let stand at 30°C, then add 0.25 mL of 10 mM HAuCl4 solution, and stir until the solution changes from golden yellow to colorless to obtain a growth solution.

[0020] (c) Preparation of gold nanorod dispersion

[0021] After adding 0.105 mL of 37 wt.% hydrochloric acid to the growth solution to adjust the pH, 75 μL of 64 mM ascorbic acid solution and 40 μL of seed solution were added in sequence. After vigorous stirring, the solution was kept at a constant temperature of 30°C and centrifuged. After removing the supernatant, deionized water was added and centrifuged. The separated material was dispersed in deionized water to obtain a hydrophilic gold nanorod dispersion.

[0022] Preferably, in step (b), 9.25 mL of 0.1 M CTAB solution and 0.062 g of NaOL are dissolved in 14.5 mL of water at 50° C., and after cooling to 30° C., 1.2 mL of 4 mM AgNO 3 solution is added.

[0023] Preferably, in step (c), the stirring rate is 400 rpm.

[0024] Preferably, in step (4), the stirring rate is 800 rpm.

[0025] Preferably, in step (5), the centrifugal speed is 6000 rpm and the centrifugal time is 30 min; the separated material is washed twice with ethanol.

[0026] Therefore, the present invention has the following beneficial effects:

[0027] (1) The surface modification process is simple. It only requires adding OTMS and ammonia water and stirring to complete the modification in one step.

[0028] (2) It has a wide range of applications and can be used to modify the surface of gold nanorods coated with silica of different porosities;

[0029] (3) The prepared oleophilic gold nanorod material can retain the physical properties of the gold nanorods themselves while being evenly dispersed in oily solvents, thus broadening the application range of gold nanorods. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a transmission electron microscope image of the oleophilic gold nanorods obtained in Example 1.

[0031] Figure 2 This is a physical picture of the oil-water stratification formed after the lipophilic gold nanorod dispersion obtained in Example 1 is added to water.

[0032] Figure 3 This is a transmission electron microscope image of the oleophilic gold nanorods obtained in Example 2.

[0033] Figure 4 This is a transmission electron microscope image of the oleophilic gold nanorods obtained in Example 3. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] (1) Preparing gold nanorod dispersion by seed method;

[0037] (a) Preparation of seed solution

[0038] After mixing 10 mL of 0.1 M CTAB solution and 0.25 mL of 10 mM HAuCl4 solution, add 0.3 mL of 0.02 M NaBH4 solution and stir vigorously until the color of the solution changes from golden yellow to brown yellow to obtain a seed solution;

[0039] (b) Preparation of Growth Solution

[0040] Dissolve 9.25 mL of 0.1 M CTAB solution and 0.062 g of NaOL in 14.5 mL of water at 50 °C, cool to 30 °C, add 1.2 mL of 4 mM AgNO3 solution, keep it in a 30 °C water bath for 15 min, add 0.25 mL of 10 mM HAuCl4 solution, and stir at 400 rpm until the solution changes from golden yellow to colorless to obtain a growth solution;

[0041] (c) Preparation of gold nanorod dispersion

[0042] After adding 0.105 mL of 37 wt.% hydrochloric acid to the growth solution to adjust the pH, 75 μL of 64 mM ascorbic acid solution and 40 μL of seed solution were added in sequence. After vigorous stirring, the solution was kept at a constant temperature of 30°C and centrifuged. After removing the supernatant, deionized water was added and centrifuged. The separated material was dispersed in deionized water to obtain a hydrophilic gold nanorod dispersion.

[0043] (2) Cleaning

[0044] The gold nanorod dispersion was centrifuged, and the separated matter was dispersed in a 1.5 mM CTAB solution to obtain a gold nanorod concentrate. The concentration of gold nanorods in the gold nanorod concentrate was the same as that in the gold nanorod dispersion before centrifugation.

[0045] (3) Silicon dioxide coating

[0046] 0.4 mL of 0.2 M NaOH solution was added to the gold nanorod concentrate, and TEOS was added six times, 0.04 mL of TEOS was added each time, and the mixture was stirred for 30 minutes after each addition. After the sixth addition of TEOS, the mixture was stirred for 2 days to obtain a gold nanorod dispersion coated with silica.

[0047] (4) Surface modification

[0048] After centrifuging the silica-coated gold nanorod dispersion, remove the supernatant and add 25 mL of ethanol to obtain a silica-coated gold nanorod ethanol dispersion; take 3 mL of the silica-coated gold nanorod ethanol dispersion, add 100 μL of 32 wt.% ammonia water and 500 μL of 2.4 wt.% OTMS chloroform solution in sequence, stir at 800 rpm for 24 hours to obtain a reaction product.

[0049] (5) Cleaning and dispersion

[0050] The reaction product was centrifuged at 6000 rpm for 30 minutes, the separated product was washed twice with ethanol, and then dispersed in cyclohexane to obtain the lipophilic gold nanorod material.

[0051] The transmission electron microscope image of the lipophilic gold nanorods obtained in this example is as follows: Figure 1 As shown. Figure 1 It can be seen that the surface of the gold nanorods is uniformly coated with mesoporous silica, with a size of about 15 nm. The coating integrity is high, there are no independent gold rods with coating failure, and the reaction repeatability is high.

[0052] The surface modified gold nanorod dispersion obtained in this example was added to a certain amount of water to form an oil-water stratification structure as shown in the figure below: Figure 2 As shown. Figure 2 It can be seen that the water-oil system produces an obvious oil-water stratification phenomenon (the density of cyclohexane is lower than that of water, and the upper layer is the surface-modified gold nanorod dispersion), which shows that the surface-modified gold nanorods can be stably dispersed in oily solvents, are insoluble in water, and have excellent lipophilic properties.

[0053] Example 2

[0054] The difference between this embodiment and embodiment 1 is that in step (2), the separated material is dispersed in a 1 mM CTAB solution, and the rest is the same as embodiment 1.

[0055] The transmission electron microscope image of the lipophilic gold nanorods obtained in this example is as follows: Figure 3 As shown. Figure 3 It can be seen that the surface of the gold nanorods is uniformly coated with mesoporous silica, but compared with Example 1, the porosity of the mesoporous silica layer is reduced, the size is still about 15 nm, the coating integrity is high, there are no independent gold rods with failed coating, and the reaction repeatability is high, indicating that the present invention is also applicable when the porosity of the mesoporous silica layer is low.

[0056] Example 3

[0057] The difference between this embodiment and embodiment 1 is that in step (2), the separated material is dispersed in a 2 mM CTAB solution, and the rest is the same as embodiment 1.

[0058] The transmission electron microscope image of the lipophilic gold nanorods obtained in this example is as follows: Figure 4 As shown. Figure 4 It can be seen that the surface of the gold nanorods is uniformly coated with mesoporous silica, but compared with Example 1, the porosity of the mesoporous silica layer is increased, the size is still about 15 nm, the coating integrity is high, there are no independent gold rods with coating failure, and the reaction repeatability is high, indicating that the present invention is also applicable when the porosity of the mesoporous silica layer is high.

[0059] The above-described embodiment is only a preferred solution of the present invention and does not limit the present invention in any form. There are other variations and modifications without exceeding the technical solution described in the claims.

Claims

1. A method for preparing oleophilic gold nanorods, characterized in that: The following steps are involved: (1) Preparing a gold nanorod dispersion by a seed method, the specific steps are: (a) Preparation of seed solution After mixing 10 mL of 0.1 M CTAB solution and 0.25 mL of 10 mM HAuCl4 solution, add 0.3 mL of 0.02 M NaBH4 solution and stir vigorously until the color of the solution changes from golden yellow to brown yellow to obtain a seed solution; (b) Preparation of Growth Solution Dissolve 9.25 mL of 0.1 M CTAB solution and 0.062 g of NaOL in 14.5 mL of water at 50 °C, cool to 30 °C, add 1.2 mL of 4 mM AgNO3 solution, keep at 30 °C, add 0.25 mL of 10 mM HAuCl4 solution, and stir until the solution changes from golden yellow to colorless to obtain a growth solution; (c) Preparation of gold nanorod dispersion After adding 0.105 mL of 37 wt.% hydrochloric acid to the growth solution to adjust the pH, 75 μL of 64 mM ascorbic acid solution and 40 μL of seed solution were added in sequence, stirred at 400 rpm, and then kept at 30° C. for centrifugation. After removing the supernatant, deionized water was added, and the solution was centrifuged. The separated product was dispersed in deionized water to obtain a hydrophilic gold nanorod dispersion. (2) Cleaning The gold nanorod dispersion is centrifuged, and the separated matter is dispersed in a 1-2 mM CTAB solution to obtain a gold nanorod concentrate, wherein the concentration of gold nanorods in the gold nanorod concentrate is the same as that in the gold nanorod dispersion before centrifugation; (3) Silicon dioxide coating 0.4 mL of 0.2 M NaOH solution was added to the gold nanorod concentrate, and TEOS was added six times, 0.04 mL of TEOS was added each time, and the mixture was stirred for 30 minutes after each addition. After the sixth addition of TEOS, the mixture was stirred for 2 days to obtain a gold nanorod dispersion coated with silica; (4) Surface modification After centrifuging the silica-coated gold nanorod dispersion, removing the supernatant, adding 25 mL of ethanol to obtain a silica-coated gold nanorod ethanol dispersion; taking 3 mL of the silica-coated gold nanorod ethanol dispersion, adding 100 μL of 32 wt.% ammonia water and 500 μL of 2.4 wt.% OTMS chloroform solution in sequence, stirring for 24 h, and obtaining a reaction product; (5) Cleaning and dispersion The reaction product is centrifuged, the separated product is washed with ethanol, and then dispersed in cyclohexane to obtain the lipophilic gold nanorod material.

2. The method for preparing oleophilic gold nanorods according to claim 1, characterized in that: In step (4), the stirring rate is 800 rpm.

3. The method for preparing oleophilic gold nanorods according to claim 1, characterized in that: In step (5), the centrifugal speed is 6000 rpm and the centrifugal time is 30 min; the separated material is washed twice with ethanol.

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