A method for regulating the length of gold nanorods

Abstract

The application provides a method for regulating the length of gold nanorods, which adopts light intensity of wavelength of 300 nm or above, including 320-340 nm and / or 530-700 nm, of 50 μw / cm 2 The light source is used to irradiate the gold nanorod dispersion liquid. The method for regulating the length of gold nanorods is performed after the preparation of gold nanorods is completed, mainly utilizes the metal SPR effect and the hot electron effect to realize the oxidation of gold nanorods, controls the light intensity, irradiation time and other parameters of near ultraviolet and / or visible light to realize the control of the length of gold nanorods, meanwhile, the diameter of gold nanorods is basically unchanged, the operation is simple, and no external additives are introduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterials, and more particularly to a method for regulating the length of gold nanorods. BACKGROUND

[0002] Gold nanorods are rod-shaped gold nanoparticles with a size ranging from several nanometers to hundreds of nanometers. They have two surface plasmon resonance absorption peaks, i.e., a transverse surface plasmon resonance peak (TSPRP) and a longitudinal surface plasmon resonance peak (LSPRP). When incident light interacts with the free electrons of gold nanoparticles, surface plasmon resonance (SPR) is generated, and a strong absorption peak is shown on the ultraviolet-visible absorption spectrum. The TSPRP is invariant at about 530 nm, while the LSPRP can change from the visible light to the infrared region with the change of the aspect ratio of the gold nanorods. This unique optical property makes gold nanorods have great application prospects in the fields of nanoelectronics, optics, medical detection, imaging, information storage, and clinical treatment.

[0003] The unique optical property of gold nanorods depends on the size and aspect ratio of the gold nanorods. Therefore, the size regulation method of gold nanorods is a very critical technology. The existing size regulation methods of gold nanorods can be performed during preparation or after preparation. The methods performed after preparation mainly include thermal reshaping, regrowth, and oxidation. Among them, the oxidation method is widely used. After adding an oxidizing reagent such as H2O2 to the gold nanorod solution, the gold nanorods are oxidized, the aspect ratio (AR) is reduced, and the LSPRP is blue-shifted. However, this method has a relatively complicated operation procedure, and it is difficult to accurately control the experimental parameters such as the concentration of H2O2 and the oxidation time that affect the aspect ratio of gold nanorods. The existing technology discloses a size regulation method for accurately changing the length of gold nanorods by changing the amount of chloroauric acid added. A linear relationship exists between the length of the gold nanorods and the amount of chloroauric acid added. However, the regulation method introduces bromide and chloroauric acid, which is complicated to operate. SUMMARY

[0004] The present application aims to overcome the defects and shortcomings of the existing oxidation size regulation method, which is complicated to operate and requires the introduction of external additives. The present application provides a method for regulating the length of gold nanorods. By controlling the light intensity, irradiation time, and other parameters of near-ultraviolet and / or visible light, the length of gold nanorods can be controlled while maintaining the diameter unchanged. The method is simple to operate and does not require the introduction of external additives.

[0005] The above-mentioned object of the present application is achieved by the following technical solutions.

[0006] A method for regulating the length of gold nanorods, characterized in that the light intensity of the light source with a wavelength of 300 nm or above, including 320-340 nm and / or 530-700 nm, is 50 μw / cm 2 The gold nanorod dispersion liquid is irradiated by the above light source.

[0007] The method for regulating the length of gold nanorods provided by the present application uses the light intensity of the light source with a wavelength of 300 nm or above, including 320-340 nm and / or 530-700 nm, which is 50 μw / cm 2 The gold nanorod dispersion liquid is irradiated by the above light source, and the ultraviolet light with a wavelength of 300 nm or below promotes the reduction of gold nanorods and interferes with the oxidation of gold nanorods. The principle of the light source irradiating the oxidized gold nanorods is to utilize the surface plasmon resonance (SPR) effect and the hot electron effect. Gold nanorods have strong coupling effect with light (visible light band: 530-700 nm) in the SPR frequency range thereof, which can realize the oxidation of gold nanorods, but the oxidation rate is low. Under the irradiation of near-ultraviolet light with a wavelength of 320-340 nm, the gold atoms in the conduction band of the gold nanorods can excite the inner layer electrons to form hot electrons through interband transition, which can promote the oxidation rate. Therefore, the combination of the metal SPR effect and the hot electron effect increases the oxidation rate of the gold nanorods, and realizes the oxidation of the gold nanorods. Since the field enhancement effect is more obvious at the two ends of the gold nanorods, the oxidation will preferentially occur at the two ends of the gold nanorods in the longitudinal direction, so that the length of the gold nanorods can be controlled by controlling the light intensity, irradiation time and other parameters of the near-ultraviolet and / or visible light, while the diameter of the gold nanorods remains unchanged.

[0008] In the method for regulating the length of gold nanorods provided by the present application, the gold nanorods can be prepared by any method known in the prior art, and the gold nanorod dispersion liquid can be the initial gold nanorod solution for preparing the gold nanorods, or the gold nanorods prepared can be centrifuged from the initial gold nanorod solution and then re-dissolved in ultrapure water.

[0009] Preferably, the light source is near-ultraviolet light and / or visible light with a wavelength of 300-600 nm.

[0010] When the near-ultraviolet light and the visible light are irradiated together, the metal SPR effect and the hot electron effect are combined, which can quickly realize the oxidation of the gold nanorods by the near-ultraviolet and visible light.

[0011] Further, the absorbance of the gold nanorod dispersion liquid is 0.06-0.25.

[0012] The absorbance is the amount of light absorbed by the solution. The gold nanorod dispersion liquid is detected by ultraviolet-visible absorption spectrum. The absorbance corresponding to the longitudinal surface plasmon resonance peak of the gold nanorod is read from the ultraviolet-visible absorption spectrum. The absorbance is linearly proportional to the sample concentration. With the increase of the absorbance of the gold nanorod dispersion liquid, the oxidation rate of the gold nanorod decreases.

[0013] Further, the light intensity of the light source is 80-150 μw / cm 2 .

[0014] If the light intensity is too low, the oxidation rate is low, and the reaction time is long. If the light intensity is too high, a more obvious thermal effect will be caused, leading to the ablation of the gold nanorod and the interference with the process of oxidizing the gold nanorod, and the diameter of the gold nanorod changes.

[0015] Preferably, the light intensity of the light source is 130 μw / cm 2 .

[0016] Further, the gold nanorod dispersion liquid is prepared according to the following method:

[0017] P1. Preparation of seed solution: gold nanorod seed solution is prepared by using chloroauric acid, sodium borohydride and surfactant as raw materials;

[0018] P2. Preparation of growth solution: gold nanorod growth solution is prepared by using chloroauric acid, silver nitrate, surfactant and reducing agent as raw materials;

[0019] P3. Preparation of gold nanorod dispersion liquid: the seed solution of P1 is added to the growth solution of P2, and the mixture is uniformly mixed and then statically placed for 3-18 h to make the chemical growth reaction reach equilibrium, thereby obtaining the gold nanorod dispersion liquid.

[0020] Specifically, the surfactant in the preparation method of the gold nanorod dispersion liquid is a cationic surfactant, such as a quaternary ammonium chloride salt and / or a quaternary ammonium bromide salt.

[0021] Specifically, the quaternary ammonium chloride salt is one of dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride and octadecyltrimethylammonium chloride.

[0022] Specifically, the quaternary ammonium bromide salt is one of dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide and octadecyltrimethylammonium bromide.

[0023] Specifically, the reducing agent in the step P2 in the preparation method of the gold nanorod dispersion liquid is one or more of ascorbic acid, citric acid and hydroxylamine hydrochloride.

[0024] Specifically, the molar ratio of chloroauric acid, cetyltrimethylammonium bromide and sodium borohydride in the step P1 in the preparation method of the gold nanorod dispersion liquid is 1:(200-400):(2-20).

[0025] Specifically, the molar ratio of chloroauric acid and silver nitrate in the step P2 in the preparation method of the gold nanorod dispersion liquid is (3-12):1.

[0026] Specifically, the molar ratio of chloroauric acid and ascorbic acid in the step P2 in the preparation method of the gold nanorod dispersion liquid is 1:(1-3).

[0027] Specifically, the preparation method of the gold nanorod dispersion liquid is as follows:

[0028] P1. Preparation of seed solution: chloroauric acid (HAuCl4·3H2O) and cetyltrimethylammonium bromide (CTAB) are mixed in a glass container with water as solvent, and a mixed solution is obtained by inverting and mixing gently, sodium borohydride is added to the mixed solution, and the seed solution is prepared by rapid inversion and mixing, and the seed solution in the glass container is kept in a constant temperature water bath at 25-30℃ for 2-3h;

[0029] P2. Preparation of growth solution: cetyltrimethylammonium bromide, chloroauric acid and silver nitrate (AgNO3) solution are sequentially added to a test tube and mixed to obtain a mixed solution, ascorbic acid (AA) is added to the mixed solution to prepare a growth solution, at this time the mixed solution changes from brown yellow to colorless;

[0030] P3. Preparation of gold nanorod dispersion liquid: the seed solution of P1 is added to the growth solution of P2, the reaction mixture is gently mixed, and kept in a constant temperature water bath at 25-30℃ for 3-18h to prepare the gold nanorod dispersion liquid.

[0031] The beneficial effects of the present application are:

[0032] The method for regulating the length of gold nanorods provided by the present application is carried out after the preparation of gold nanorods is completed, mainly utilizes metal SPR effect and hot electron effect to realize oxidation of gold nanorods, controls the length of gold nanorods by controlling the light intensity, illumination time and other parameters of near ultraviolet and / or visible light, and at the same time keeps the diameter of gold nanorods basically unchanged, which is simple in operation and does not need to introduce external additives. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 Transmission electron microscope pictures of the initial gold nanorods in the gold nanorod dispersion liquid prepared in Example 1 and the gold nanorods after length regulation in Example 6;

[0034] Wherein, a is the initial gold nanorod in the gold nanorod dispersion prepared in Example 1, b is the gold nanorod after length regulation in Example 1, and c is the gold nanorod after length regulation in Example 6.

[0035] Figure 2 UV-visible absorption spectrum of the initial gold nanorod in the gold nanorod dispersion prepared in Example 1 and the gold nanorod after length regulation in Examples 1-6;

[0036] Wherein, a is the UV-visible absorption spectrum curve of the initial gold nanorod, and b-g are the UV-visible absorption spectrum curves of the gold nanorod after irradiation for 1h, 2h, 3h, 4h, 5h and 6h, respectively.

[0037] Figure 3 UV-visible absorption spectrum of the gold nanorod after length regulation in Examples 7-11;

[0038] Wherein, a-e are the UV-visible absorption spectrum curves of the gold nanorod after irradiation for 1h, 2h, 3h, 4h and 5h, respectively.

[0039] Figure 4 UV-visible absorption spectrum of the gold nanorod after length regulation in Examples 13-15;

[0040] Wherein, a-c are the UV-visible absorption spectrum curves of the gold nanorod after irradiation for 1h, 2h and 3h, respectively.

[0041] Figure 5 UV-visible absorption spectrum of the gold nanorod after length regulation in Examples 17-19;

[0042] Wherein, a-c are the UV-visible absorption spectrum curves of the gold nanorod after irradiation for 1h, 2h and 3h, respectively. DETAILED DESCRIPTION

[0043] In order to more clearly and completely describe the technical solutions of the present application, the present application is further described in detail below through specific examples. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application, and various changes can be made within the scope of the present application.

[0044] Example 1

[0045] A method for regulating the length of gold nanorods, 10mL of gold nanorod dispersion (the maximum absorption wavelength is 785nm, and the absorbance is 0.22) is placed in a quartz glass container and irradiated for 1h under a light source with a light intensity of 130μw / cm 2 .

[0046] The light source used is a 250W ultraviolet high-pressure mercury lamp, and the spectral range is 240-600nm. The ultraviolet light below 300nm is filtered out during the experiment.

[0047] The preparation method of the gold nanorod dispersion liquid is as follows:

[0048] P1. Preparation of seed solution: 0.25 mL of chloroauric acid (0.01 mol / L) and 7.5 mL of cetyltrimethylammonium bromide (0.10 mol / L) were mixed in a glass container with water as the solvent, and the mixed solution was obtained by inverting and mixing gently. 0.6 mL of sodium borohydride (0.10 mol / L) was added to the mixed solution, and the mixture was mixed quickly by inverting for 2 min to prepare the seed solution. The molar ratio of chloroauric acid, cetyltrimethylammonium bromide and sodium borohydride is 1:302.4:2.25. The seed solution in the glass container was kept in a constant temperature water bath at 25°C for 2h;

[0049] P2. Preparation of growth solution: 0.2 mL of chloroauric acid (0.01 mol / L), 4.75 mL of cetyltrimethylammonium bromide (0.10 mol / L) and 0.03 mL of silver nitrate (0.01 mol / L) solution were sequentially added to a test tube and mixed to obtain a mixed solution. The molar ratio of chloroauric acid to silver nitrate is 6.7:1. 0.032 mL of ascorbic acid (0.10 mol / L) was added to the mixed solution to prepare the growth solution. The molar ratio of chloroauric acid to ascorbic acid is 1:1.6. At this time, the mixed solution changes from brown yellow to colorless;

[0050] P3. Preparation of gold nanorod dispersion liquid: 0.01 mL of P1 seed solution was added to the growth solution of P2, the reaction mixture was mixed gently for 10s, and kept in a 25°C constant temperature water bath for 3h to prepare the gold nanorod dispersion liquid.

[0051] Example 2

[0052] A method for regulating the length of gold nanorods, which is basically the same as example 1, the difference is that the irradiation time of the light source is 2h.

[0053] Example 3

[0054] A method for regulating the length of gold nanorods, which is basically the same as example 1, the difference is that the irradiation time of the light source is 3h.

[0055] Example 4

[0056] A method for regulating the length of gold nanorods, which is basically the same as example 1, the difference is that the irradiation time of the light source is 4h.

[0057] Example 5

[0058] A method for regulating the length of gold nanorods, which is basically the same as that of Example 1, except that the irradiation time of the light source is 5h.

[0059] Example 6

[0060] A method for regulating the length of gold nanorods, which is basically the same as that of Example 1, except that the irradiation time of the light source is 6h.

[0061] Example 7

[0062] A method for regulating the length of gold nanorods, which is basically the same as that of Example 1, except that the irradiation light intensity of the light source is 80μw / cm 2 .

[0063] Example 8

[0064] A method for regulating the length of gold nanorods, which is basically the same as that of Example 7, except that the irradiation time of the light source is 2h.

[0065] Example 9

[0066] A method for regulating the length of gold nanorods, which is basically the same as that of Example 7, except that the irradiation time of the light source is 3h.

[0067] Example 10

[0068] A method for regulating the length of gold nanorods, which is basically the same as that of Example 7, except that the irradiation time of the light source is 4h.

[0069] Example 11

[0070] A method for regulating the length of gold nanorods, which is basically the same as that of Example 7, except that the irradiation time of the light source is 5h.

[0071] Example 12

[0072] A method for regulating the length of gold nanorods, which is basically the same as that of Example 1, except that the light source used is a 75W xenon lamp with a spectral range of 300-700nm.

[0073] Example 13

[0074] A method for regulating the length of gold nanorods, 10mL of gold nanorod dispersion (with a maximum absorption wavelength of 785nm and an absorbance of 0.22) was placed in a quartz glass container and irradiated under a light source with an intensity of 130μw / cm 2 for 1h.

[0075] The light source used is a 250W ultraviolet high-pressure mercury lamp with a spectral range of 240-600nm, and only visible light with a wavelength range of 530-600nm was retained during the experiment.

[0076] Example 14

[0077] A method for regulating the length of gold nanorods, which is basically the same as that of Example 13, except that the irradiation time of the light source is 2h.

[0078] Example 15

[0079] A method for regulating the length of gold nanorods, which is basically the same as that of Example 13, except that the irradiation time of the light source is 3h.

[0080] Example 16

[0081] A method for regulating the length of gold nanorods, which is basically the same as that of Example 13, except that the light source used is a CW dye laser, and the spectral range is 550-700nm.

[0082] Example 17

[0083] A method for regulating the length of gold nanorods, 10mL of gold nanorod dispersion (the maximum absorption wavelength is 785nm, and the absorbance is 0.22) is placed in a quartz glass container and irradiated under a light source with an intensity of 130μw / cm 2 for 1h.

[0084] The light source used is a 250W ultraviolet high-pressure mercury lamp, and the spectral range is 240-600nm. During the experiment, only near-ultraviolet light with a wavelength range of 320-340nm is retained.

[0085] Example 18

[0086] A method for regulating the length of gold nanorods, which is basically the same as that of Example 17, except that the irradiation time of the light source is 2h.

[0087] Example 19

[0088] A method for regulating the length of gold nanorods, which is basically the same as that of Example 17, except that the irradiation time of the light source is 3h.

[0089] The gold nanorods after length regulation in each example are subjected to the following test and test research.

[0090] (1) Morphology characterization test

[0091] The initial gold nanorods in the gold nanorod dispersion prepared in Example 1 and the gold nanorods after length regulation in Example 6 are subjected to morphology characterization test.

[0092] The test method is as follows: transmission electron microscopy is used to characterize the morphology of the initial gold nanorods in the gold nanorod dispersion prepared in Example 1 and the gold nanorods after length regulation in Example 6.

[0093] Test results Figure 1 shown, Figure 1 a is a TEM image of the initial gold nanorod in the gold nanorod dispersion prepared in Example 1, the length of the initial gold nanorod is 80.5 nm, and the diameter is 21 nm; Figure 1 b is a TEM image of the gold nanorod after the length is regulated in Example 1, the length of the gold nanorod is 77 nm, and the diameter is 21 nm; Figure 1 c is a TEM image of the gold nanorod after the length is regulated in Example 6, the length of the gold nanoparticle obtained after the initial gold nanorod is oxidized for 6 h is 23 nm, and the diameter is 21 nm. Figure 1 It can be seen that after the gold nanorod is irradiated by the near-ultraviolet and visible light with a wavelength of 300-600 nm for 1 h, the length of the gold nanorod is shortened, but the diameter is basically unchanged, and the morphology is also unchanged, and until the gold nanorod is shortened into a gold nanoparticle after being irradiated for 6 h, it is indicated that the near-ultraviolet and visible light irradiation can oxidize the gold nanorod and regulate the length of the gold nanorod, and with the increase of the irradiation time, the length of the gold nanorod is continuously shortened, and the diameter is basically unchanged.

[0094] The morphology of the gold nanorod obtained after the treatment in Examples 2-5 is similar to that of Example 1, the length is gradually shortened, and the diameter is basically unchanged, and until the gold nanorod is shortened into a gold nanoparticle after being irradiated for 6 h in Example 6.

[0095] The morphology of the gold nanorod obtained after the treatment in Examples 7-11 is similar to the change of the morphology in Examples 1-5, the length is gradually shortened, and the diameter is basically unchanged, but because the light intensity is reduced, compared with Examples 1-5, the rate of oxidizing the gold nanorod by the near-ultraviolet and visible light is slowed down, and the length of the gold nanorod is shortened in the same irradiation time.

[0096] The morphology of the gold nanorod obtained after the treatment in Example 12 is similar to that of Example 1, which indicates that other light sources with a spectral range of 300-700 nm can also realize the oxidation of the gold nanorod.

[0097] The morphology of the gold nanorod obtained after the treatment in Examples 13-15 is similar to the change of the morphology in Examples 1-3, the length is gradually shortened, and the diameter is basically unchanged, but because only the surface plasmon resonance (SPR) effect of the metal is used, the gold nanorod has a strong coupling effect with the light (visible light band: 530-700 nm) in the SPR frequency range thereof, although the oxidation of the gold nanorod can be realized, but the oxidation rate is low.

[0098] The morphology of the gold nanorod obtained after the treatment in Example 16 is similar to that of Example 13, which indicates that other light sources with a spectral range of 530-700 nm can also realize the oxidation of the gold nanorod.

[0099] The morphology of the gold nanorods obtained after the treatment of Examples 17-19 is similar to the morphology change of Examples 1-3, the length of the gold nanorods gradually shortens, and the diameter remains basically unchanged. The gold atoms in the conduction band of the gold nanorods can be excited to form hot electrons through interband transition under the irradiation of near-ultraviolet light with a wavelength of 320-340 nm, thereby realizing the oxidation of the gold nanorods. Compared with the oxidation of the gold nanorods under the combined irradiation of near-ultraviolet and visible light in Examples 1-3, the oxidation rate is lower.

[0100] (2) UV-Vis absorption spectrum detection

[0101] The initial gold nanorods in the gold nanorod dispersion liquid prepared in Example 1 and the gold nanorods after length control in Examples 1-6 were subjected to UV-Vis absorption spectrum detection.

[0102] The test method is as follows: the gold nanorod dispersion liquid is centrifuged twice at 12000 rpm for 15 min, and the gold nanorod precipitate after removing impurities by centrifugation is redissolved in pure water, and the gold nanorods are subjected to UV-Vis absorption spectrum detection by using a UV-Vis spectrometer.

[0103] The test results are shown in Figure 2 , wherein a is the UV-Vis absorption spectrum curve of the initial gold nanorods in the gold nanorod dispersion liquid prepared in Example 1, and b-g are respectively the UV-Vis absorption spectrum curves of the gold nanorods after irradiation of the light source with an intensity of 130 μw / cm 2 for 1 h, 2 h, 3 h, 4 h, 5 h and 6 h in Examples 1-6. The longitudinal surface plasmon resonance peak wavelengths of the initial gold nanorods in the gold nanorod dispersion liquid prepared in Example 1 and the gold nanorods after length control in Examples 1-6 are 785 nm, 767 nm, 710 nm, 672 nm, 644 nm, 621 nm and 525 nm respectively, and according to the empirical formula LSPRP = 95AR + 420 of the longitudinal surface plasmon resonance peak wavelength and the aspect ratio of the gold nanorods, under the condition that the diameter of the gold nanorods remains almost unchanged, the longitudinal surface plasmon resonance peak wavelength (LSPRP) of the gold nanorods is linearly related to the length of the gold nanorods, so it can be seen that under the same irradiation light intensity, the irradiation time of the light source can control the length of the gold nanorods.

[0104] The gold nanorods after length control in Examples 7-11 were subjected to UV-Vis absorption spectrum detection.

[0105] The test results are shown in Figure 3 , wherein a-e are respectively the UV-Vis absorption spectrum curves of the gold nanorods after irradiation of the light source with an intensity of 80 μw / cm 2The UV-Vis absorption spectra of gold nanorods after irradiation with a light source for 1 h, 2 h, 3 h, 4 h, and 5 h are shown. In Examples 7-11, the wavelengths of the longitudinal surface plasmon resonance peaks of the gold nanorods with adjusted lengths were 773 nm, 729 nm, 712 nm, 700 nm, and 680 nm, respectively. Example 2 was irradiated with a light intensity of 130 μw / cm². 2 Irradiation was performed for 2 hours under a light source, and in Example 9 the light intensity was 80 μw / cm. 2 The wavelengths of the longitudinal surface plasmon resonance peaks of the gold nanorods obtained by irradiating them under a light source for 3 hours were similar (710 nm for the gold nanorods in Example 2 and 712 nm for the gold nanorods in Example 9), proving that the stronger the light intensity, the shorter the irradiation time required to obtain gold nanorods of the same size.

[0106] The gold nanorods after length adjustment in Example 12 were subjected to UV-Vis absorption spectroscopy.

[0107] The test results were the same as in Example 1 at a light intensity of 130 μw / cm. 2 The UV-Vis absorption spectrum curves of the gold nanorods after 1 hour of irradiation with the light source are similar.

[0108] The gold nanorods in Examples 13-15 were subjected to UV-Vis absorption spectroscopy after length adjustment.

[0109] Test results as follows Figure 4 As shown, a to c are the UV-Vis absorption spectra of gold nanorods after 1h, 2h and 3h of visible light irradiation in the wavelength range of 530-600nm, respectively. The longitudinal surface plasmon resonance peak of the gold nanorods blue shifts with irradiation time, but it can be seen from the figure that the blue shift of LSPRP is small, which proves that the rate of visible light oxidation of gold nanorods is low.

[0110] The gold nanorods after length adjustment in Example 16 were subjected to UV-Vis absorption spectroscopy.

[0111] The detection results are similar to the UV-Vis absorption spectrum curve of the gold nanorods after 1 hour of irradiation in Example 13.

[0112] The gold nanorods in Examples 17-19 were subjected to UV-Vis absorption spectroscopy after length adjustment.

[0113] Test results as follows Figure 5 As shown, a to c are the UV-Vis absorption spectra of gold nanorods after 1h, 2h, and 3h of near-ultraviolet light irradiation in the wavelength range of 320-340nm, respectively. The longitudinal surface plasmon resonance peak of the gold nanorods blue-shifts with irradiation time, proving that near-ultraviolet light in the range of 320-340nm can oxidize gold nanorods, but the oxidation rate is lower than that of irradiation by both near-ultraviolet and visible light.

[0114] In summary, the method of the embodiment can oxidize gold nanorods by near ultraviolet and / or visible light radiated by different light sources, and realize the length control of gold nanorods. When the near ultraviolet and visible light in the wavelength range of 320-340 nm and 530-700 nm is irradiated together, the oxidation rate of gold nanorods is faster. The present application realizes the oxidation of gold nanorods by using metal SPR effect and hot electron effect, that is, the oxidation of gold nanorods by near ultraviolet and / or visible light, and can realize the length control of gold nanorods by controlling the irradiation light intensity, irradiation time and other parameters of near ultraviolet and / or visible light, while keeping the diameter unchanged.

[0115] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. Those skilled in the art should understand that other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to enumerate all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A method for controlling the length of gold nanorods, characterized in that, Use light with wavelengths above 320 nm, including 320–340 nm and / or 530–700 nm, with an intensity of 50 μw / cm². 2 The above light sources were used to irradiate the gold nanorod dispersion. The gold nanorod dispersion was prepared according to the following method: P1. Seed solution preparation: Gold nanorod seed solutions were prepared using chloroauric acid, sodium borohydride, and surfactants as raw materials; P2. Preparation of growth solution: A gold nanorod growth solution was prepared using chloroauric acid, silver nitrate, surfactant, and reducing agent as raw materials; P3. Preparation of gold nanorod dispersion: Add seed solution of P1 to growth solution of P2, mix evenly, and let stand for 3~18h to allow chemical growth reaction to reach equilibrium, and obtain the gold nanorod dispersion. The molar ratio of chloroauric acid, hexadecyltrimethylammonium bromide and sodium borohydride in P1 is 1:(200~400):(2~20); The molar ratio of chloroauric acid to silver nitrate in P2 is (3~12):

1.

2. The method for controlling the length of gold nanorods according to claim 1, characterized in that, The absorbance of the gold nanorod dispersion is 0.06~0.

25.

3. The method for controlling the length of gold nanorods according to claim 1, characterized in that, The light intensity of the light source is 80~150 μw / cm² 2 .

4. The method for controlling the length of gold nanorods according to claim 3, characterized in that, The light intensity of the light source is 130 μw / cm². 2 .

5. The method for controlling the length of gold nanorods according to claim 1, characterized in that, The surfactant is a cationic surfactant, a quaternary ammonium chloride salt or / or a quaternary ammonium bromide salt.

6. The method for controlling the length of gold nanorods according to claim 1, characterized in that, The reducing agent in P2 is one or more of ascorbic acid, citric acid, or hydroxylamine hydrochloride.

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