Shell-regulated discrete chiral gold core-silver shell nanomaterials and preparation method thereof

Abstract

The application discloses a kind of shell regulation discrete chiral gold core silver shell nanomaterial and its preparation method, method includes the following steps: using anisotropic gold nanorod material, into which adding surfactant, cysteine, ascorbic acid, chloroauric acid solution is reacted, discrete chiral gold nanorod with strong plasmonic circular dichroism response is obtained;Then after centrifugation and purification concentration, adding cysteine, silver nitrate, ascorbic acid, secondary reaction is carried out to chiral gold nanorod.The scheme reaction condition is mild, easy to operate;And the discrete chiral gold core silver shell nanoparticles obtained is very good, single nanoparticle, with strong PCD signal, and chiral silver shell can amplify and reverse the chirality of chiral gold core, very suitable for biological sensing, basic research (such as surface chemistry and PCD mechanism research) etc..

Description

TECHNICAL FIELD

[0001] The application belongs to the field of preparation of optically active metal nanoparticles, and relates to a shell-regulated discrete chiral gold core-silver shell nanomaterial and a preparation method thereof. BACKGROUND

[0002] Chirality refers to the property of an object that cannot be superimposed on its mirror image, just like our left and right hands, which look similar but cannot be completely superimposed. In the microscopic world, many biological molecules, such as proteins and DNA, have chirality. Chiral substances have different responses to left-handed and right-handed circularly polarized light, which is called circular dichroism (CD). Plasmonic chirality is a combination of the two properties. When a nanomaterial has both plasmonic properties and chiral structures, plasmonic chiral nanoparticles are formed. These particles not only have unique optical enhancement effects due to plasmons, but also have significantly different responses to circularly polarized light of different rotation directions due to chiral structures, greatly enhancing the circular dichroism signal.

[0003] The gold core-silver shell structure has many significant advantages. First, from the perspective of stability, gold has excellent chemical stability and can provide a stable support framework for the entire nanoparticle as the core, effectively preventing structural damage or chemical changes of the particle under different environmental conditions, and helping to maintain the overall integrity of the chiral plasmonic nanoparticles. Second, in terms of optical properties, silver has excellent optical properties, with a significant surface plasmon resonance effect, which can produce strong light absorption and scattering. When silver is wrapped as a shell outside the gold core, not only can the plasmonic properties of the nanoparticle be enhanced, but also the chiral structure can interact with the plasmonic properties, further enhancing the chiral optical responses such as circular dichroism (CD) and circularly polarized light absorption (CPL). Chiral plasmonic nanomaterials have attracted more and more attention due to their unique optical activity, and have been widely used in biological sensing, tumor treatment, photocatalysis and other fields. However, how to precisely regulate the chiral signal of chiral plasmonic nanocrystals remains a difficult problem. SUMMARY

[0004] The purpose of the present application is to provide a shell-regulated discrete chiral gold core-silver shell nanomaterial and a preparation method thereof to solve the above defects.

[0005] To achieve the above purpose, the present application provides the following technical solutions:

[0006] The preparation method of the shell-regulated discrete chiral gold core-silver shell nanomaterial comprises the following steps:

[0007] (1) adding hexadecyl trimethyl ammonium chloride and cysteine into the anisotropic gold nanorod solution in sequence, mixing and adsorbing, then adding chloroauric acid and ascorbic acid to react, and obtaining discrete chiral gold nanorods after centrifugation and dispersion;

[0008] (2) adding hexadecyl trimethyl ammonium chloride and cysteine into the solution containing the chiral gold nanorods in sequence, mixing and adsorbing, then adding silver nitrate and ascorbic acid to react, and obtaining the shell-regulated optical activity discrete chiral gold core-silver shell nanomaterials after centrifugation.

[0009] Preferably, in the step (1), the concentration of the gold nanorods in the anisotropic gold nanorod solution ranges from 0.5 to 1 mM.

[0010] Preferably, in the step (1), the concentration of the hexadecyl trimethyl ammonium chloride used is 20 mM to 40 mM, and the concentration of the cysteine is 40 nM to 100 nM.

[0011] Preferably, in the step (1), the molar ratio of ascorbic acid to chloroauric acid is (20-40):1.

[0012] Preferably, in the step (1), the centrifugation speed is 4000 r / min to 6000 r / min, and the centrifugation time is 5 min to 10 min; the adsorption time in the step (1) is 1 hour, and the adsorption temperature is 30℃.

[0013] Preferably, in the step (2), the concentration of the chiral gold nanorods in the chiral gold nanorod solution ranges from 0.5 to 1.5 mM.

[0014] Preferably, in the step (2), the concentration of the hexadecyl trimethyl ammonium chloride used is 50 mM to 100 mM, the concentration of the cysteine is 1 μM to 4 μM, the concentration of the silver nitrate is 0 to 300 μM, and the concentration of the ascorbic acid is 0 to 3 mM.

[0015] Preferably, in the step (2), the centrifugation speed is 4000 r / min to 6000 r / min, and the centrifugation time is 5 min to 10 min; the adsorption time in the step (2) is 1 hour, and the adsorption temperature is 30℃; the reaction time in the step (2) is 2 hours, and the reaction temperature is 70℃.

[0016] A shell-regulated discrete chiral gold core-silver shell nanomaterial, prepared according to the preparation method of the shell-regulated discrete chiral gold core-silver shell nanomaterial, comprising a chiral gold core and a chiral silver shell coated on the chiral gold core.

[0017] Preferably, the particle size of the chiral gold core is 50-150 nm, and the thickness of the silver shell is 3-30 nm.

[0018] The present application has the advantages of:

[0019] (1) The preparation method of the shell-regulated discrete chiral gold core-silver shell nanomaterials is simple, convenient, short in time, low in energy consumption, small in raw material loss, low in preparation cost, good in repeatability and reproducibility, and can prepare monodisperse intrinsic chiral gold nanoparticles, which have very stable and large-range controllable chiral plasmonic signals in the visible light region; these controllable monodisperse noble metal nanoparticles are very suitable for enhancing surface detection (such as enhancing surface Raman effect, biological imaging, etc.), and have wide applicability and popularization value.

[0020] (2) The preparation method of the shell-regulated discrete chiral gold core-silver shell nanomaterials not only realizes the regulation of the chiral signals of the chiral gold nanoparticles in a large range, but also realizes the chiral amplification and inversion of the chiral gold nanoparticles by regulating the silver shell. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 : UV and TEM pictures of gold nanorods prepared in Examples 1-6. Figure 1 a is the UV picture of the gold nanorods, Figure 1 b is the TEM picture of the gold nanorods.

[0022] Figure 2 : UV, CD and TEM pictures of chiral gold nanorods prepared in Examples 1-6. Figure 2 a is the UV, CD picture of the gold nanorods, Figure 2 b is the TEM picture of the chiral gold nanorods.

[0023] Figure 3 : UV, CD and g-factor columnar chart of chiral gold nanorod core-silver shell materials prepared in Examples 1-4. Figure 3 a-d are respectively the UV CD pictures of C-LAμ@LAg, C-LAμ@DAg, C-DAμ@LAg and C-DAμ@DAg. Figure 3 e-h are respectively the g-factor columnar charts of C-LAμ@LAg, C-LAμ@DAg, C-DAμ@LAg and C-DAμ@DAg

[0024] Figure 4 : TEM pictures of chiral gold nanorod core-silver shell materials prepared in Examples 1-2. Figure 4 a-c are the TEM pictures of C-LAμ, Figure 4 d-f are the TEM pictures of C-LAμ@LAg when the silver nitrate is 20 μl,Figure 4 h-i are the TEM images of C-LAμ@DAg when the concentration of silver nitrate is 20 μl.

[0025] Figure 5 : UV-CD spectra of chiral gold nanorod core non-chiral silver shell material prepared in Example 5-6. Figure 5 a-b are the CD spectra of C-LAμ@Ag and C-DAμ@Ag respectively, Figure 5 c-d are the UV spectra of C-LAμ@Ag and C-DAμ@Ag respectively. DETAILED DESCRIPTION

[0026] The application will be further described below in conjunction with the examples. It should be noted that the examples are only examples and illustrations of the concept of the application, and those skilled in the art can make various modifications or supplements to the described specific examples or replace them with similar ways, as long as they do not deviate from the concept of the application or exceed the scope defined by the claims.

[0027] Example 1:

[0028] A preparation method of a chiral gold nanorod core left-handed cysteine induced chiral silver shell material (C-LAμ@LAg) induced by left-handed cysteine, comprising the following steps:

[0029] (1), preparing left-handed chiral gold nanorods with strong chiral response, specifically as follows:

[0030] Preparation of gold nanorod solution, the specific preparation steps are: adding 250 μl of chloroauric acid solution with a concentration of 10 mM and 600 μL of sodium borohydride solution with a concentration of 10 mM prepared at 0 ℃ ice water into 9.75 mL of 0.1M CTAB solution, and obtaining gold nanoseed solution after reacting at room temperature for two hours; adding 2 ml of chloroauric acid solution with a concentration of 10 mM, 40 ml of cetyltrimethylammonium bromide solution with a concentration of 0.1M, 0.8 mL of 1M hydrochloric acid solution, 0.32 ml of 0.1M ascorbic acid and 0.4 ml of 0.01M silver nitrate solution into a centrifuge tube, and then immediately adding 15 μl of seed solution, shaking uniformly, and reacting at 30 ℃ for 12 h to obtain gold nanorod solution.

[0031] The gold nanorod solution was separated by centrifugation at 8000 r / min for 10 min to obtain a precipitate solution of gold nanorods. Then, 4 ml of a 40 mM cetyltrimethylammonium chloride solution, 50 μl of a 5 μM L-cysteine solution, and 150 μl of a 0.01 M chloroauric acid solution were added to the solution and mixed uniformly. Then, 475 μl of a 0.1 M ascorbic acid solution was added to the mixed solution, followed by the addition of deionized water to make the total volume of the mixed solution 5 ml. The solution was immediately placed in a water bath at 30°C for 2 h. The product was centrifuged at 6000 r / min for 10 min, and the precipitate was re-dispersed in deionized water to obtain a chiral gold nanorod solution.

[0032] (2) Preparation of C-LAμ@LAg materials with different shell thicknesses, as follows:

[0033] Five groups of comparative tests were performed. First, 1 ml of the chiral gold nanorod solution prepared in step (1) was taken, 3 ml of a 80 mM cetyltrimethylammonium chloride solution was added, and 6 μl of a 1 mM L-cysteine solution was added. The solution was adsorbed at 30°C for 1 h. Then, 0 μl, 5 μl, 20 μl, 40 μl, and 80 μl of a 10 mM silver nitrate solution was added, respectively, and immediately the same volume of a 0.1 M ascorbic acid solution was added. The solution was immediately placed in a water bath at 70°C for 2 h. The product was centrifuged at 6000 r / min for 10 min, and the precipitate was re-dispersed in deionized water to obtain C-LAμ@LAg.

[0034] The UV and TEM images of the gold nanorod solution prepared in step (1) are shown in Figure 1 Figure 1 a shows that the transverse plasmon resonance peak of the prepared gold nanorods is at 520 nm, and the longitudinal plasmon resonance peak is at 720 nm, Figure 1 b shows that the prepared gold nanorods are relatively uniform, with a width of 34 nm, a length of about 103 nm, and an aspect ratio of about 3. The UV, CD spectra, and TEM images of the L-chiral gold nanorod (C-LAμ) solution prepared in step (1) are shown in Figure 2 Figure 2 a shows that the transverse plasmon resonance peak of the prepared chiral gold rods is at 577 nm, which has a red shift relative to the transverse plasmon resonance peak of the gold nanorods. The longitudinal plasmon resonance peak of the chiral gold rods is at 712 nm, which has a blue shift relative to the longitudinal plasmon resonance peak of the gold nanorods, indicating that gold grows more on the two sides of the gold rods, making the aspect ratio of the chiral gold rods smaller than that of the gold nanorods, Figure 2 b shows that the TEM image of the chiral gold rods also proves this, Figure 2 b shows that the width of the chiral gold rods is about 70 nm, the length is about 140 nm, and the aspect ratio is about 2. Figure 2 ​​The CD spectra of a show that the chiral gold nanorods induced by L-cysteine and D-cysteine have good optical activity, and show very good symmetry, and the chiral peaks are at 572 nm and 760 nm, respectively, which is very consistent with the UV spectra. The UV and CD spectra of the C-LAμ@LAg solution with different shell thicknesses prepared in step (2) are shown in Figure 3 a. As shown in the figure, with the increase of the content of silver nitrate, the UV spectrum is blue-shifted as a whole, which indicates that silver is successfully grown on the surface of the chiral gold nanorod, and the CD begins to reverse, and the chirality is greatly enhanced. When the content of silver nitrate is 20 μl, the g factor reaches the maximum, and the specific g factor is shown in Figure 3 e. The transmission spectra of C-LAμ@LAg are shown in 4d-f, which are very uniform, and the silver shell grows more on the four corners of the chiral gold nanorod, and the thickness of the silver shell on the four corners is about 10-15 nm, and the thickness of the silver shell on the side is about 3-7 nm. Most of the chiral inversion is almost caused by the great change of the shape of the material, but here it can be observed that the shape of C-LAμ@LAg (4d-f) is almost the same as that of C-LAμ (4a-c), which proves that the chiral inversion of C-LAμ@LAg relative to C-LAμ is not caused by the change of shape, but by the chiral silver shell. When the cysteine of the chiral gold nanorod core is the same as the cysteine in the chiral silver shell, it will cause the chiral inversion.

[0035] Example 2:

[0036] A preparation method of a chiral gold nanorod core induced by L-cysteine and a chiral silver shell induced by D-cysteine material (C-LAμ@DAg), comprising the following steps:

[0037] (1) preparing a left-handed chiral gold nanorod with strong chiral response, specifically as follows:

[0038] Preparation of gold nanorod solution: 250 μl of chloroauric acid solution with a concentration of 10 mM and 600 μL of sodium borohydride solution with a concentration of 10 mM prepared in ice water at 0°C were added to 9.75 mL of 0.1M CTAB solution, and gold nanoseed solution was obtained after two hours of reaction at room temperature; 2 ml of 10 mM chloroauric acid solution, 40 ml of 0.1M cetyltrimethylammonium bromide solution, 0.8 mL of 1M hydrochloric acid solution, 0.32 ml of 0.1M ascorbic acid, and 0.4 ml of 0.01M silver nitrate solution were added to a centrifuge tube, and then 15 μl of seed solution was immediately added, shaken uniformly, and reacted at 30°C for 12 h to obtain gold nanorod solution.

[0039] The gold nanorod solution was separated by centrifugation at 8000 r / min for 10 min to obtain a precipitate solution of gold nanorods. Then, 4 ml of a 40 mM cetyltrimethylammonium chloride solution, 50 μl of a 5 μM L-cysteine solution, and 150 μl of a 0.01 M chloroauric acid solution were added to the solution and mixed uniformly. Then, 475 μl of a 0.1 M ascorbic acid solution was added to the mixed solution, followed by the addition of deionized water to make the total volume of the mixed solution 5 ml. The solution was immediately placed in a water bath at 30°C for 2 h. The product was centrifuged at 6000 r / min for 10 min, and the precipitate was re-dispersed in deionized water to obtain a chiral gold nanorod solution.

[0040] (2) Preparation of C-LAμ@DAg materials with different shell thicknesses, as follows:

[0041] Five groups of comparative tests were performed. First, 1 ml of the chiral gold nanorod solution prepared in step (1) was added with 3 ml of a 80 mM cetyltrimethylammonium chloride solution and 6 μl of a 1 mM D-cysteine solution, and adsorbed at 30°C for 1 h. Then, 0 μl, 5 μl, 20 μl, 40 μl, and 80 μl of a 10 mM silver nitrate solution were added, respectively, and immediately added with ascorbic acid of the same volume as the silver nitrate solution and with a concentration of 0.1 M. The solution was immediately placed in a water bath at 70°C for 2 h. The product was centrifuged at 6000 r / min for 10 min, and the precipitate was re-dispersed in deionized water to obtain C-LAμ@DAg.

[0042] The UV and TEM images of the gold nanorod solution prepared in step (1) are shown in Figure 1 Figure 1 a shows that the transverse plasmon resonance peak of the prepared gold nanorods is at 520 nm, and the longitudinal plasmon resonance peak is at 720 nm, Figure 1 b shows that the prepared gold nanorods are relatively uniform, with a width of 34 nm, a length of about 103 nm, and an aspect ratio of about 3. The UV, CD spectra, and TEM images of the L-chiral gold nanorod (C-LAμ) solution prepared in step (1) are shown in Figure 2 Figure 2 a shows that the transverse plasmon resonance peak of the prepared chiral gold rods is at 577 nm, which is red-shifted relative to the transverse plasmon resonance peak of the gold nanorods, and the longitudinal plasmon resonance peak of the chiral gold rods is at 712 nm, which is blue-shifted relative to the longitudinal plasmon resonance peak of the gold nanorods, which indicates that gold grows more on the two sides of the gold rods, making the aspect ratio of the chiral gold rods smaller than that of the gold nanorods, Figure 2 b shows that the TEM image of the chiral gold rods also proves this, Figure 2 b shows that the width of the chiral gold rods is about 70 nm, the length is about 140 nm, and the aspect ratio is about 2. Figure 2 ​​The CD spectra of a show that the chiral gold nanorods induced by L-cysteine and D-cysteine have good optical activity, and show very good symmetry, and the chiral peaks are at 572 nm and 760 nm, respectively, which is very consistent with the UV spectra. The UV and CD spectra of the C-LAμ@DAg solution with different shell thicknesses prepared in step (2) are shown in Figure 3 b. As the content of silver nitrate increases, the UV spectrum as a whole is blue-shifted, which indicates that silver is successfully grown on the surface of the chiral gold nanorod, and the CD does not reverse, and the chirality is greatly enhanced. The g factor reaches a maximum when the content of silver nitrate is 20 μl, and the specific g factor is shown in Figure 3 f. The transmission spectra of C-LAμ@DAg are shown in 4g-i, which are very uniform, and the silver shell is more grown on the four corners of the chiral gold nanorod, and the thickness of the silver shell on the four corners is about 10-15 nm, and the thickness of the silver shell on the side is about 3-7 nm. Here, it can be observed that the shape of C-LAμ@DAg (4g-i) is almost the same as that of C-LAμ (4a-c) and C-LAμ@LAg (4d-f). When the cysteine of the chiral gold nanorod core is opposite to the cysteine in the chiral silver shell, it does not cause the chirality to reverse.

[0043] Example 3:

[0044] A method for preparing a chiral gold nanorod core induced by D-cysteine and a chiral silver shell material (C-DAμ@LAg) induced by L-cysteine, comprising the following steps:

[0045] (1) Preparing a right-handed chiral gold nanorod with strong chiral response, specifically as follows:

[0046] Prepare a gold nanorod solution, and the specific preparation steps are as follows: add 250 μl of a 10 mM chloroauric acid solution and 600 μL of a 10 mM sodium borohydride solution prepared in ice water at 0°C to 9.75 mL of a 0.1 M CTAB solution, and obtain a gold nanoseed solution after reacting at room temperature for two hours; add 2 ml of a 10 mM chloroauric acid solution, 40 ml of a 0.1 M cetyltrimethylammonium bromide solution, 0.8 mL of a 1 M hydrochloric acid solution, 0.32 ml of a 0.1 M ascorbic acid solution, and 0.4 ml of a 0.01 M silver nitrate solution to a centrifuge tube, and then immediately add 15 μl of the seed solution, shake uniformly, and react at 30°C for 12 h to obtain a gold nanorod solution.

[0047] The gold nanorod solution was centrifuged at 8000 r / min for 10 min to obtain a precipitate solution of gold nanorods. Then, 4 ml of a 40 mM cetyltrimethylammonium chloride solution, 50 μl of a 5 μM L-cysteine solution, and 150 μl of a 0.01 M chloroauric acid solution were added to the solution and mixed uniformly. Then, 475 μl of a 0.1 M ascorbic acid solution was added to the mixed solution, followed by the addition of deionized water to make the total volume of the mixed solution 5 ml. The solution was immediately placed in a 30 °C water bath for 2 h. The product was centrifuged at 6000 r / min for 10 min, and the precipitate was re-dispersed in deionized water to obtain a chiral gold nanorod solution.

[0048] (2) Preparation of C-DAμ@LAg materials with different shell thicknesses, as follows:

[0049] Five groups of comparative tests were performed. First, 1 ml of the chiral gold nanorod solution prepared in step (1) was taken, 3 ml of a 80 mM cetyltrimethylammonium chloride solution was added, and 6 μl of a 1 mM L-cysteine solution was added. The solution was adsorbed at 30 °C for 1 h. Then, 0 μl, 5 μl, 20 μl, 40 μl, and 80 μl of a 10 mM silver nitrate solution was added, respectively, and immediately the same volume of a 0.1 M ascorbic acid solution was added. The solution was immediately placed in a 70 °C water bath for 2 h. The product was centrifuged at 6000 r / min for 10 min, and the precipitate was re-dispersed in deionized water to obtain C-DAμ@LAg.

[0050] The UV and TEM images of the gold nanorod solution prepared in step (1) are shown in Figure 1 Figure 1 a shows that the transverse plasmon resonance peak of the prepared gold nanorods is at 520 nm, and the longitudinal plasmon resonance peak is at 720 nm, Figure 1 b shows that the prepared gold nanorods are relatively uniform, with a width of 34 nm, a length of about 103 nm, and an aspect ratio of about 3. The UV and CD spectra of the L-chiral gold nanorod (C-DAμ) solution prepared in step (1) are shown in Figure 2 Figure 2 a shows that the transverse plasmon resonance peak of the prepared chiral gold rods is at 577 nm, which has a red shift relative to the transverse plasmon resonance peak of the gold nanorods. The longitudinal plasmon resonance peak of the chiral gold rods is at 712 nm, which has a blue shift relative to the longitudinal plasmon resonance peak of the gold nanorods. This indicates that more gold grows on the two sides of the gold rods, making the aspect ratio of the chiral gold rods smaller than that of the gold nanorods. Figure 2 ​​The CD spectra of a show that the chiral gold nanorods induced by L-cysteine and D-cysteine have good optical activity, and show very good symmetry, and the chiral peaks are at 572 nm and 760 nm, respectively, which is very consistent with the UV spectra. The UV and CD spectra of the C-DAμ@LAg solution with different shell thicknesses prepared in step (2) are shown in Figure 3 c. With the increase of the content of silver nitrate, the UV spectrum as a whole is blue-shifted, which indicates that silver is successfully grown on the surface of the chiral gold nanorod, and the CD does not appear to be reversed, and the chirality is greatly enhanced. When the content of silver nitrate is 20 μl, the g factor reaches the maximum, and the specific g factor is shown in Figure 3 g. When the cysteine of the chiral gold nanorod core is opposite to the cysteine in the chiral silver shell, it does not cause the chirality to be reversed.

[0051] Example 4:

[0052] A method for preparing a chiral silver shell material (C-DAμ@DAg) induced by D-cysteine, comprising the following steps:

[0053] (1) Preparation of D-chiral gold nanorods with strong chiral response, as follows:

[0054] Prepare the gold nanorod solution, and the specific preparation steps are as follows: add 250 μl of chloroauric acid solution with a concentration of 10 mM and 600 μL of sodium borohydride solution with a concentration of 10 mM prepared in ice water at 0°C to 9.75 mL of 0.1M CTAB solution, and obtain the gold nanoseed solution after reacting at room temperature for two hours; add 2 ml of 10 mM chloroauric acid solution, 40 ml of 0.1M cetyltrimethylammonium bromide solution, 0.8 mL of 1M hydrochloric acid solution, 0.32 ml of 0.1M ascorbic acid, and 0.4 ml of 0.01M silver nitrate solution into a centrifuge tube, and then immediately add 15 μl of the seed solution, shake uniformly, and react at 30°C for 12 h to obtain the gold nanorod solution.

[0055] Centrifuge 1 mL of the above gold nanorod solution at 8000 r / min for 10 min to separate the precipitate solution of the gold nanorod; add 4 ml of 40 mM cetyltrimethylammonium chloride solution, 50 μl of 5 μM D-cysteine solution, and 150 μl of 0.01M chloroauric acid solution to the solution, and mix uniformly; then add 475 μl of 0.1M ascorbic acid solution to the mixed solution, and then add deionized water to make the total volume of the mixed solution 5 mL; immediately place it in a 30°C water bath for 2 h, and then centrifuge the product at 6000 r / min for 10 min, and then re-disperse the precipitate in deionized water to obtain the chiral gold nanorod solution.

[0056] (2) Preparation of C-DAμ@DAg materials with different shell thickness, as follows:

[0057] Five groups of comparative tests were adopted. First, 1 ml of the chiral gold nanorod solution prepared in step (1) was taken, 3 ml of a 80 mM cetyltrimethylammonium chloride solution was added, 6 μl of 1 mM d-cysteine was added, and adsorption was carried out at 30°C for 1 hour. Then, 0 μl, 5 μl, 20 μl, 40 μl and 80 μl of a 10 mM silver nitrate solution was added, respectively, and immediately, an equal volume of 0.1 M ascorbic acid was added. Then, immediately, the mixture was placed in a 70°C water bath for growth for 2 hours. The product was centrifuged at 6000 r / min for 10 minutes, and the precipitate was re-dispersed in deionized water to obtain C-DAμ@DAg.

[0058] The UV and TEM images of the gold nanorod solution prepared in step (1) are shown in Figure 1 Figure 1 a shows that the transverse plasmon resonance peak of the prepared gold nanorod is at 520 nm, and the longitudinal plasmon resonance peak is at 720 nm, Figure 1 b shows that the prepared gold nanorod is relatively uniform, with a width of 34 nm, a length of about 103 nm, and an aspect ratio of about 3. The UV and CD spectra of the d-cysteine chiral gold nanorod (C-DAμ) solution prepared in step (1) are shown in Figure 2 Figure 2 a shows that the transverse plasmon resonance peak of the prepared chiral gold rod is at 577 nm, which has a red shift relative to the transverse plasmon resonance peak of the gold nanorod, and the longitudinal plasmon resonance peak of the chiral gold rod is at 712 nm, which has a blue shift relative to the longitudinal plasmon resonance peak of the gold nanorod, which indicates that more gold grows on the two sides of the gold rod, making the aspect ratio of the chiral gold rod smaller than that of the gold nanorod. Figure 2 a shows that the transverse plasmon resonance peak of the prepared chiral gold rod is at 577 nm, which has a red shift relative to the transverse plasmon resonance peak of the gold nanorod, and the longitudinal plasmon resonance peak of the chiral gold rod is at 712 nm, which has a blue shift relative to the longitudinal plasmon resonance peak of the gold nanorod, which indicates that more gold grows on the two sides of the gold rod, making the aspect ratio of the chiral gold rod smaller than that of the gold nanorod. Figure 3 d shows that as the silver nitrate content increases, the UV spectrum as a whole is blue-shifted, which indicates that silver is successfully grown on the surface of the chiral gold rod, the CD appears to be reversed, and the chirality is greatly enhanced. When the silver nitrate content is 20 μl, the g factor reaches a maximum, as shown in h. Figure 3 h shows that when the cysteine of the chiral gold rod core is the same as the cysteine in the chiral silver shell, the chirality is reversed.

[0059] Example 5:

[0060] ​​A preparation method of a chiral gold nanorod core non-chiral silver shell material (C-LAμ@Ag) induced by L-cysteine, comprising the following steps:

[0061] (1) preparing L-chiral gold nanorods with strong chiral response, specifically as follows:

[0062] Preparation of gold nanorod solution, the specific preparation steps are: adding 250 μl of chloroauric acid solution with a concentration of 10 mM and 600 μL of sodium borohydride solution with a concentration of 10 mM prepared by 0 ℃ ice water into 9.75 mL of 0.1M CTAB solution, and obtaining gold nanoseed solution after reacting for two hours at room temperature; adding 2 ml of 10 mM chloroauric acid solution, 40 ml of 0.1M cetyltrimethylammonium bromide solution, 0.8 mL of 1M hydrochloric acid solution, 0.32 ml of 0.1M ascorbic acid and 0.4 ml of 0.01M silver nitrate solution into a centrifugal tube, and then immediately adding 15 μl of seed solution into the centrifugal tube, shaking uniformly, and obtaining gold nanorod solution after reacting for 12 h at 30 ℃.

[0063] Centrifuging 1 mL of the above gold nanorod solution at 8000 r / min for 10 min to separate the precipitate solution of gold nanorods; adding 4 ml of 40 mM cetyltrimethylammonium chloride solution, 50 μl of 5 μM L-cysteine solution and 150 μl of 0.01M chloroauric acid solution into the solution and mixing uniformly; then adding 475 μl of 0.1M ascorbic acid solution into the mixed solution, and then adding deionized water to make the total volume of the mixed solution 5 mL; and immediately placing the mixed solution in a 30 ℃ water bath for 2 h, and then centrifuging the product at 6000 r / min for 10 min to re-disperse the precipitate in deionized water to obtain a chiral gold nanorod solution.

[0064] (2) preparation of C-LAμ@Ag materials with different shell thicknesses, specifically as follows:

[0065] Five groups of comparative tests are adopted. First, 1 ml of the chiral gold nanorod solution prepared in step (1) is added into 3 ml of 80 mM cetyltrimethylammonium chloride solution, and then 0 μl, 5 μl, 20 μl, 40 μl and 80 μl of 10 mM silver nitrate solution is added respectively, and immediately 0.1M ascorbic acid with the same volume as the silver nitrate is added. Then, immediately placing the mixed solution in a 70 ℃ water bath for 4 h. The product is centrifuged at 6000 r / min for 10 min, and then the precipitate is re-dispersed in deionized water to obtain C-LAμ@Ag.

[0066] The ultraviolet and transmission electron microscope images of the gold nanorod solution prepared in step (1) are shown in Figure 1 Figure 1 ​a indicates that the transverse plasmon resonance peak of the prepared gold nanorod is at 520 nm, and the longitudinal plasmon resonance peak is at 720 nm, Figure 1 b indicates that the prepared gold nanorod is relatively uniform, with a width of 34 nm, a length of about 103 nm, and an aspect ratio of about 3. The UV, CD spectra and transmission electron microscopy of the prepared left-handed chiral gold nanorod (C-LAμ) solution in step (1) are shown in Figure 2 Figure 2 a indicates that the transverse plasmon resonance peak of the prepared chiral gold rod is at 577 nm, which has a red shift relative to the transverse plasmon resonance peak of the gold nanorod. The longitudinal plasmon resonance peak of the chiral gold rod is at 712 nm, which has a blue shift relative to the longitudinal plasmon resonance peak of the gold nanorod, which indicates that gold grows more on both sides of the gold rod, making the aspect ratio of the chiral gold rod smaller than that of the gold nanorod, Figure 2 b The transmission electron microscopy of the chiral gold rod also proves this, Figure 3 b The width of the chiral gold rod is about 70 nm, the length is about 140 nm, and the aspect ratio is about 2. Figure 3 a The CD spectrum indicates that the chiral gold rod induced by left-handed and right-handed cysteine has good optical activity, and exhibits very good symmetry, with chiral peaks at 572 nm and 760 nm, respectively, which is consistent with the UV spectrum. The UV, CD spectra of the C-LAμ@Ag solution prepared in step (2) are shown in Figure 1 c, 5a, with the increase of silver nitrate content, the overall UV spectrum is blue-shifted, but the gold chirality gradually disappears, and a weak silver chiral peak begins to appear. This indicates that the silver shell cannot cause chirality amplification and inversion, and the real working is the cysteine in the silver shell.

[0067] Example 6:

[0068] A preparation method of a chiral gold nanorod core non-chiral silver shell material (C-DAμ@Ag) induced by right-handed cysteine, comprising the following steps:

[0069] (1) preparing right-handed chiral gold nanorods with strong chiral response, specifically as follows:

[0070] ​The gold nanorod solution was prepared by adding 250 μl of 10 mM HAuCl4 solution and 600 μl of 10 mM NaBH4 solution prepared in ice water at 0°C to 9.75 ml of 0.1 M CTAB solution, and then reacting for 2 hours at room temperature to obtain a gold nanoseed solution; 2 ml of 10 mM HAuCl4 solution, 40 ml of 0.1 M CTAB solution, 0.8 ml of 1 M HCl solution, 0.32 ml of 0.1 M ascorbic acid solution and 0.4 ml of 0.01 M AgNO3 solution were added into a centrifuge tube, and then 15 μl of the seed solution was immediately added, followed by shaking and reacting for 12 hours at 30°C to obtain the gold nanorod solution.

[0071] The gold nanorod precipitate solution was obtained by centrifuging 1 ml of the above gold nanorod solution at 8000 r / min for 10 min; 4 ml of 40 mM CTAB solution, 50 μl of 5 μM D-cysteine solution and 150 μl of 0.01 M HAuCl4 solution were added into the gold nanorod precipitate solution and mixed uniformly; then 475 μl of 0.1 M ascorbic acid solution was added into the mixed solution, followed by adding deionized water to make the total volume of the mixed solution 5 ml; and then the mixed solution was immediately placed into a water bath at 30°C for 2 hours; and the product was centrifuged at 6000 r / min for 10 min, and then the precipitate was redispersed in deionized water to obtain the chiral gold nanorod solution.

[0072] (2) Preparation of C-DAμ@Ag materials with different shell thicknesses, which was carried out as follows:

[0073] Five groups of comparative tests were carried out. First, 1 ml of the chiral gold nanorod solution prepared in step (1) was added with 3 ml of 80 mM CTAB solution, and then 0 μl, 5 μl, 20 μl, 40 μl and 80 μl of 10 mM AgNO3 solution was added respectively, and immediately the same volume of 0.1 M ascorbic acid solution as the AgNO3 solution was added. Then the solution was immediately placed into a water bath at 70°C for 4 hours. The product was centrifuged at 6000 r / min for 10 min, and then the precipitate was redispersed in deionized water to obtain C-DAμ@Ag.

[0074] The UV and TEM images of the gold nanorod solution prepared in step (1) are shown in Figure 1 Figure 1 a shows that the transverse plasmon resonance peak of the prepared gold nanorod is at 520 nm, and the longitudinal plasmon resonance peak is at 720 nm, Figure 2 b shows that the prepared gold nanorod is relatively uniform, with a width of 34 nm, a length of about 103 nm and an aspect ratio of about 3. The UV and CD spectra of the D-cysteine chiral gold nanorod (C-DAμ) solution prepared in step (1) are shown in Figure 2 a and b.​Figure 2 a indicates that the transverse plasmon resonance peak of the prepared chiral gold rod is at 577 nm, which is red-shifted relative to the transverse plasmon resonance peak of the gold nanorod, and the longitudinal plasmon resonance peak of the chiral gold rod is at 712 nm, which is blue-shifted relative to the longitudinal plasmon resonance peak of the gold nanorod, which indicates that more gold grows on both sides of the gold rod, making the aspect ratio of the chiral gold rod smaller than that of the gold nanorod. Figure 2 a The CD spectrum indicates that the chiral gold rods induced by left-handed and right-handed cysteine have good optical activity, and exhibit very good symmetry, with chiral peaks at 572 nm and 760 nm, respectively, which is consistent with the UV spectrum. The UV and CD spectra of the C-DAμ@Ag solution with different shell thicknesses prepared in step (2) are as follows: Figure 2 d, 5b shows that with the increase of silver nitrate content, the overall UV spectrum is blue-shifted, but the gold chirality gradually disappears, and a weak silver chiral peak begins to appear. This indicates that the silver shell does not cause chirality amplification and inversion, and the real working material is the cysteine in the silver shell.

[0075] Results analysis of examples 1-6:

[0076] (1) Analysis of the properties of chiral silver shell material (C-LAμ@LAg) induced by left-handed cysteine:

[0077] Figure 5 a indicates that the thickness of the chiral silver shell has a great regulating effect on the chiral gold nanorod. When the gold core and the cysteine in the silver shell are the same, both are left-handed cysteine, with the increase of the thickness of the silver shell, the plasmon resonance peak is gradually blue-shifted, and with the further increase of the thickness of the chiral silver shell, the UV is further blue-shifted, and the CD begins to invert, and the chirality is greatly enhanced, when the amount of silver nitrate is 20 μl, the g factor reaches the maximum, and the positive and negative values of the g factor are opposite to those of the initial chiral gold nanorod core. Figure 1 d-f shows that the silver shell grows more on the four corners of the chiral gold rod, and the thickness of the silver shell on the four corners is about 10-15 nm, and the thickness of the silver shell on the side is about 3-7 nm. With the further increase of the thickness of the silver shell, the chirality of gold begins to weaken, and a silver chiral peak begins to appear.

[0078] (2) Analysis of the properties of chiral silver shell material (C-LAμ@DAg) induced by left-handed cysteine:

[0079] Figure 1b shows that the thickness of the chiral silver shell has a great control effect on the chiral gold nanorod. When the cysteine in the gold core and the silver shell is opposite, the plasmon resonance peak gradually blue shifts with the increase of the thickness of the silver shell. Continue to increase the thickness of the chiral silver shell, the ultraviolet continues to blue shift, but the CD does not appear to reverse, and the chirality is greatly enhanced. When the amount of silver nitrate is 20 μl, the g factor reaches the maximum, and the positive and negative values of the g factor of the initial chiral gold nanorod core are the same. Figure 1 g-i shows that the silver shell grows more in the four corners of the chiral gold rod, and the thickness of the silver shell in the four corners is about 10-15 nm, and the thickness of the silver shell on the side is about 3-7 nm. With the further increase of the thickness of the silver shell, the chirality of gold begins to weaken, and the chirality peak of silver begins to appear.

[0080] (3) Properties analysis of chiral gold nanorod core induced by dextrorotatory cysteine and chiral silver shell material induced by levorotatory cysteine (C-DAμ@LAg):

[0081] Figure 2 c shows that the thickness of the chiral silver shell has a great control effect on the chiral gold nanorod. When the cysteine in the gold core and the silver shell is opposite, the plasmon resonance peak gradually blue shifts with the increase of the thickness of the silver shell. Continue to increase the thickness of the chiral silver shell, the ultraviolet continues to blue shift, but the CD does not appear to reverse, and the chirality is greatly enhanced. When the amount of silver nitrate is 20 μl, the g factor reaches the maximum, and the positive and negative values of the g factor of the initial chiral gold nanorod core are the same. With the further increase of the thickness of the silver shell, the chirality of gold begins to weaken, and the chirality peak of silver begins to appear.

[0082] (4) Properties analysis of chiral gold nanorod core induced by dextrorotatory cysteine and chiral silver shell material induced by dextrorotatory cysteine (C-DAμ@DAg):

[0083] Figure 2 d shows that the thickness of the chiral silver shell has a great control effect on the chiral gold nanorod. When the cysteine in the gold core and the silver shell is the same, both are dextrorotatory cysteine, the plasmon resonance peak gradually blue shifts with the increase of the thickness of the silver shell. Continue to increase the thickness of the chiral silver shell, the ultraviolet continues to blue shift, the CD begins to reverse, and the chirality is greatly enhanced. When the amount of silver nitrate is 20 μl, the g factor reaches the maximum, and the positive and negative values of the g factor of the initial chiral gold nanorod core are opposite. With the further increase of the thickness of the silver shell, the chirality of gold begins to weaken, and the chirality peak of silver begins to appear.

[0084] (5) Properties analysis of chiral gold nanorod core induced by levorotatory cysteine and non-chiral silver shell material (C-LAμ@Ag):

[0085] Figure 2a indicates that the non-chiral silver shell thickness has a greater regulatory effect on the chiral gold nanorod. When there is no cysteine in the silver shell, as the silver shell increases, the ultraviolet continues to further blue shift, the chirality of gold begins to weaken, and as the silver shell further increases, the chirality peak of gold almost completely disappears, but a weak silver chirality peak begins to appear.

[0086] (6) Properties analysis of chiral gold nanorod core non-chiral silver shell material (C-DAμ@Ag) induced by dextro-cysteine:

[0087] Figure 5 Figure 3 Figure 4 Figure 3 Figure 4 Figure 3 Figure 3 Figure 5 Figure 5 b indicates that the non-chiral silver shell thickness has a greater regulatory effect on the chiral gold nanorod. When there is no cysteine in the silver shell, as the silver shell increases, the ultraviolet continues to further blue shift, the chirality of gold begins to weaken, and as the silver shell further increases, the chirality peak of gold almost completely disappears, but a weak silver chirality peak begins to appear.

[0088] The shell-regulated discrete chiral gold core silver shell nanomaterial preparation method of the application has the advantages of simple and convenient operation, short time, low energy consumption, small raw material loss, low preparation cost, good repeatability and reproducibility, and can prepare monodisperse intrinsic chiral gold nanoparticles, which have very stable and controllable chiral plasmon signals in the visible light region; these controllable monodisperse noble metal nanoparticles are very suitable for enhancing surface detection (such as enhancing surface Raman effect, biological imaging, etc.), and have wide applicability and promotional value.

[0089] The shell-regulated discrete chiral gold core silver shell nanomaterial preparation method of the application not only realizes wide-range regulation of the chiral signal of the chiral gold nanoparticles, but also realizes chiral amplification and inversion of the chiral gold nanoparticles by regulating the silver shell.

[0090] In summary, the shell-regulated discrete chiral gold core silver shell nanomaterial preparation method of the application has the advantages of simple and convenient operation, short time, low energy consumption, small raw material loss, low preparation cost, good repeatability and reproducibility, and can prepare monodisperse intrinsic chiral gold nanoparticles, which have very stable and controllable chiral plasmon signals in the visible light region; these controllable monodisperse noble metal nanoparticles are very suitable for enhancing surface detection (such as enhancing surface Raman effect, biological imaging, etc.), and have wide applicability and promotional value. The shell-regulated discrete chiral gold core silver shell nanomaterial preparation method of the application not only realizes wide-range regulation of the chiral signal of the chiral gold nanoparticles, but also realizes chiral amplification and inversion of the chiral gold nanoparticles by regulating the silver shell.

[0091] The above examples are more typical embodiments of the present application, and are not any limitation to the present application. Therefore, according to the general idea of the present application, the process parameters described by the skilled in the art are adjusted and modified, as long as the concept of the present application is not deviated or beyond the scope defined by the present claims, which should be within the protection scope of the present application.

Claims

1. A method for preparing discrete chiral gold-core silver-shell nanomaterials with shell-controlled structure, characterized in that: Includes the following steps: (1) Hexadecyltrimethylammonium chloride and cysteine ​​were added sequentially to the anisotropic gold nanorod solution, mixed evenly, and then adsorbed. Chloroauric acid and ascorbic acid were added to react. After the reaction was completed, the nanorods were dispersed by centrifugation to obtain discrete chiral gold nanorods. The centrifugation speed was 4000 r / min to 6000 r / min, and the centrifugation time was 5 min to 10 min. The adsorption time in step (1) was 1 hour, and the adsorption temperature was 30℃. (2) Hexadecyltrimethylammonium chloride and cysteine ​​are added sequentially to the solution containing the chiral gold nanorods, mixed evenly, and then adsorbed. Silver nitrate and ascorbic acid are then added for reaction. The resulting product is centrifuged to obtain the shell-controlled discrete chiral gold core-silver shell nanomaterial. In step (2), the concentration of chiral gold nanorods in the chiral gold nanorod solution ranges from 0.5 to 1.5 mM, the concentration of hexadecyltrimethylammonium chloride is 50 mM to 100 mM, and the concentration of cysteine ​​is 1 µM to 4 µM. The concentration of silver nitrate is 0-300µM, and the concentration of ascorbic acid is 0-3mM; the product is centrifuged at a speed of 4000r / min~6000r / min for 5min-10min; the adsorption time in step (2) is 1 hour, and the adsorption temperature is 30℃; the reaction time in step (2) is 2 hours, and the reaction temperature is 70℃; the discrete chiral gold core-silver shell nanomaterial includes a chiral gold core and a chiral silver shell covering the chiral gold core, the particle size of the chiral gold core is 50-150nm, and the thickness of the silver shell is 3-30nm.

2. The preparation method according to claim 1, characterized in that: In step (1), the concentration of gold nanorods in the anisotropic gold nanorod solution ranges from 0.5 to 1 mM.

3. The preparation method according to claim 1, characterized in that: In step (1), the concentration of hexadecyltrimethylammonium chloride used is 20mM~40mM; the concentration of cysteine ​​is 40nM-100nM.

4. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of ascorbic acid to chloroauric acid is (20~40):

1.

5. A discrete chiral gold-core silver-shell nanomaterial with shell-controlled structure, characterized in that, The discrete chiral gold core-silver shell nanomaterial prepared according to any one of claims 1 to 4 comprises a chiral gold core and a chiral silver shell covering the chiral gold core.

6. The discrete chiral gold-core silver-shell nanomaterial with shell-controlled structure according to claim 5, characterized in that, The chiral gold core has a particle size of 50–150 nm, and the silver shell has a thickness of 3–30 nm.

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