Chiral spiral gold nanorod with {111} crystal face oriented growth and preparation method of chiral spiral gold nanorod

Abstract

The invention discloses a chiral spiral gold nanorod with {111} crystal face oriented growth and a preparation method of the chiral spiral gold nanorod, and belongs to the technical field of nano materials. According to the chiral spiral gold nanorod, a single-surface gold nanorod is prepared to serve as a gold seed, then a chiral inducer is used for regulating and controlling parameters such as the proportion and concentration of a growth solution and the adding amount of a gold seed solution, and thermodynamics and dynamics of nanogold growth are regulated and controlled so as to promote formation of a spiral chiral structure and reduce generation of impurities; and finally, centrifugally purifying to obtain a high-purity product. The obtained chiral spiral gold nanorod is uniform in size and stable in chiral signal, the surface plasma resonance wavelength can be simply adjusted within the range of 700-900 nm, and the technical problems that in traditional chiral plasma nanostructure preparation, efficiency is low, the structure is unstable, and nanoscale size control is difficult to achieve are solved. The method has wide application value in the fields of chiral sensing, chiral asymmetric catalysis, plasma nano antennas and the like.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, and particularly relates to a chiral helical gold nanorod grown with {111} crystal plane orientation and its preparation method. Background Technology

[0002] In recent years, chiral plasmonic nanostructures (CPNSs) have been proven to be useful for constructing broadband circular polarizers and novel photonic metamaterials due to their remarkable plasmonic circular dichroism (PCD) response over a wide spectral range. Furthermore, CPNSs can undergo enantioselective interactions with organic molecules, thus showing broad application prospects in chiral sensing, chiral separation, enantioselective catalysis, and other biological fields.

[0003] Generally, obtaining CPNSs with strong PCD response mainly relies on two preparation strategies:

[0004] The first approach involves using various organic chiral templates to form chiral components from achiral plasmon nanoparticles (NPs). However, these superstructures are unstable due to many factors, and their configuration is severely limited by the shape of the template.

[0005] The second method is the top-down approach, which involves directly fabricating CPNS with intrinsic chiral shapes such as helices and swastikas. However, these structures are always fabricated using expensive micro-nano fabrication equipment, such as electron beam lithography, which is not only costly and inefficient but also makes it difficult to overcome the processing limits to achieve precise nanoscale size control.

[0006] To overcome the shortcomings of existing technologies, the synthesis of intrinsically chiral single nanoparticles using bottom-up wet chemical methods has become a current research hotspot. Among numerous materials, gold nanorods (NRs) have attracted widespread interest due to their linearly tunable aspect ratio (SPR) along the longitudinal axis, stronger local field enhancement (compared to spherical NPs), and chemical stability or biocompatibility. Currently, the preparation of chiral gold nanorods using wet chemical methods is mainly carried out in specific chiral growth environments. By precisely controlling synthesis parameters (such as temperature, pH, surfactant concentration, type and amount of chiral inducing agent), the synergistic effect of chiral inducing agent and crystal face growth is utilized to promote the growth of helical chiral structures on the surface of gold nanorods, thereby generating a huge chiral response based on structural effects.

[0007] However, existing preparation methods often suffer from technical bottlenecks such as low yield, poor structural uniformity, and difficulty in controlling synthesis conditions, which limit their widespread application. Summary of the Invention

[0008] The first objective of this invention is to address the shortcomings of existing technologies by providing a method for preparing chiral helical gold nanorods grown with {111} crystal plane orientation. This method is simple, controllable, and yields high purity and good reproducibility of the chiral helical gold nanorods while shortening the purification time.

[0009] To achieve the above objectives, the technical solution specifically adopted by the present invention is as follows:

[0010] A method for preparing chiral helical gold nanorods grown with {111} crystal plane orientation includes the following steps:

[0011] (1) Preparation of single-surface gold nanorods

[0012] (1-1) Preparation of nano-gold seed solution: Nano-gold seed solution was synthesized using chloroauric acid solution, hexadecyltrimethylammonium bromide (CTAB) solution and sodium borohydride solution as raw materials.

[0013] (1-2) Preparation of growth solution: The growth solution was prepared using chloroauric acid solution, silver nitrate solution, hexadecyltrimethylammonium bromide solution and hydroquinone solution as raw materials.

[0014] (1-3) Growth of single-surface gold nanorods: Take an appropriate amount of the gold nanorod seed solution obtained in step (1-1) and add it to the growth solution obtained in step (1-2), stir, and place it in a water bath for heating and incubation to obtain a single-surface gold nanorod solution; the single-surface gold nanorods have a particle size of 10-15 nm and a length of 80-100 nm.

[0015] (2) Preparation of chiral helical gold nanorods

[0016] (2-1) Chiral induction incubation: Prepare chiral incubation environment solution: Mix 5-10 mM L-cysteine ​​solution and 15-30 mM 4-aminobenzylthiophenol solution at a volume ratio of 4-6:1 to obtain a mixed solution, then add hexadecyltrimethylammonium bromide solution, then add single-surface gold nanorods, stir evenly and incubate in water bath.

[0017] (2-2) Chiral growth: Silver nitrate solution, chloroauric acid solution and ascorbic acid solution were added sequentially to the solution after incubation in step (2-1), and the solution was heated in a water bath to obtain a crude solution of chiral helical gold nanorods.

[0018] (3) Purification of chiral helical gold nanorods

[0019] Centrifuge the crude solution of chiral helical gold nanorods obtained in step (2), take the centrifuged product, add hexadecyltrimethylammonium bromide solution, centrifuge again, and redisperse the precipitate in pure water to obtain a chiral helical gold nanorod solution.

[0020] This invention achieves high yield by adjusting parameters such as the ratio and concentration of the growth solution and the amount of gold seed solution added, so that single-surface gold nanorod seed solution can be grown under suitable conditions to obtain chiral helical gold nanorods. After purification, impurities are further reduced to obtain high-purity chiral helical gold nanorods.

[0021] Step (1-1) is the crystal nucleus formation step. Sodium borohydride has strong reducing properties and can reduce ionic gold to atomic gold. The atoms aggregate into nuclei to form 3-15 nm nano-gold seeds, which are then used as crystal nuclei to synthesize single-surface gold nanorods.

[0022] Preferably, in step (1-1), the step of preparing the nano-gold seed solution is as follows: mixing 0.01-0.05 M chloroauric acid solution with 0.05-0.2 M CTAB solution, stirring until clear, then adding 0.01-0.06 M sodium borohydride solution, mixing, and aging to obtain the nano-gold seed solution, wherein the volume ratio of the chloroauric acid solution, CTAB solution, and sodium borohydride solution is 0.05-0.25:4.65-18.6:0.1-0.6.

[0023] More preferably, in step (1-1), the aging conditions are: 25-30℃, 2-3 h.

[0024] Preferably, in steps (1-3), the temperature of the water bath is 15-40 ℃ and the time is 5-10 h.

[0025] Step (2) is the chiral growth step. By adjusting parameters such as the ratio and concentration of the chiral inducer and the amount of single-surface gold nanorod solution added, the thermodynamics and kinetics of the growth of gold nanorods are controlled, thereby promoting the spiral growth of single-surface gold nanorods.

[0026] Preferably, in step (2-1), the volume ratio of L-cysteine ​​solution to 4-aminothiophenol solution is 5:1.

[0027] Preferably, in step (2-1), the temperature of the water bath is 15-30 ℃; temperature has a great influence on growth after chiral incubation; the time is 2-3 h.

[0028] Preferably, in step (2-1), the volume ratio of the mixture, the hexadecyltrimethylammonium bromide solution, and the single-surface gold nanorod solution is 1-2:25-75:50-150.

[0029] Preferably, in step (2-1), the concentration of the hexadecyltrimethylammonium bromide solution is 0.05-0.2 M.

[0030] Preferably, in step (2-2), the volume ratio of silver nitrate solution, chloroauric acid solution and ascorbic acid solution is 1-4:1-4:1-4.

[0031] Preferably, in step (2-2), the concentration of silver nitrate solution is 0.01-0.05 M, the concentration of chloroauric acid solution is 0.01-0.05 M, and the concentration of ascorbic acid solution is 0.04-0.2 M.

[0032] Preferably, in step (2-2), the water bath heating temperature is 60-90℃ and the time is 1-4 h.

[0033] Preferably, in step (3), the centrifugation conditions are 7000-8000 g for 5-15 min.

[0034] A second objective of this invention is to provide chiral helical gold nanorods synthesized by the above method.

[0035] The chiral helical gold nanorods described above have uniform size and stable chiral signals. The controllable helical depth of the chiral helical gold nanorods allows their plasmon resonance absorption peak to be tuned in the range of 700-900 nm, which has broad application prospects in chiral sensing, chiral asymmetric catalysis, and plasma nanoantennas.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) The method of this invention is simple and controllable. By introducing a chiral inducing agent and CTAB during the secondary growth of a single-surface gold rod, the bromide ions in CTAB preferentially adsorb onto the {100} crystal plane of the gold nanorod, rather than the {111} crystal plane. It has a stronger passivation effect on the {100} crystal plane: it selectively adsorbs onto the {100} side of the gold nanorod, inhibiting the atomic deposition and growth rate of this crystal plane; while the {111} end face is affected by Br - With weak adsorption capacity and lower stability of the CTAB bilayer, it becomes the main deposition site for gold atoms, ultimately driving the anisotropic growth of gold nanorods along the {111} crystal orientation. This enables the thermodynamics and kinetics of gold nanorod growth to be controlled, promoting chiral helical growth while reducing the growth of impurities, revealing the unique role of bromide ions in constructing chiral plasmonic nanostructures.

[0038] (2) The method of the present invention has high efficiency in synthesizing chiral helical gold nanorods with a yield of over 70%. After purification and removal of impurities, the purity of the chiral helical gold nanorods reaches over 85%.

[0039] (3) The chiral helical gold nanorods prepared by the method of the present invention have uniform size and their surface plasmon resonance wavelength can be easily adjusted between 700 and 900 nm. They have good applicability and broad application prospects. Attached Figure Description

[0040] Figure 1 This is a TEM image of the single-surface gold nanorod solution in Example 1.

[0041] Figure 2 The image shows the UV absorption spectrum of the single-surface gold nanorod solution in Example 1.

[0042] Figure 3 This is a TEM image of the helical gold nanorods in Example 2.

[0043] Figure 4 The image shows the ultraviolet absorption spectrum of the spiral gold nanorods in Example 2.

[0044] Figure 5 The image shows the circular dichroism spectrum of the helical gold nanorods in Example 2.

[0045] Figure 6 This is a crystal plane analysis diagram of the helical gold nanorods in Example 2.

[0046] Figure 7 This is a TEM image of the gold nanorod solution obtained in Comparative Example 1.

[0047] Figure 8 This is a TEM image of the chiral helical gold nanorod solution obtained in Comparative Example 2.

[0048] Figure 9 TEM image of a solution of helical gold nanorods regulated by iodine ions. Detailed Implementation

[0049] The present invention will be further described below with reference to the embodiments.

[0050] Example 1: Preparation of single-surface gold nanorod solution

[0051] (1) Preparation of nano gold seed solution: 0.25 mL of 10 mM chloroauric acid solution was added to 10 mL of 0.1 M hexadecyltrimethylammonium bromide solution and stirred thoroughly until the mixed solution was clear, transparent and slightly yellow. Then 0.6 mL of 0.01 M sodium borohydride solution was added and stirred vigorously for 2 min to mix. After aging at 30℃ for 2 h, nano gold seed solution was obtained.

[0052] (2) Preparation of growth solution: 20 mL of 10 mM chloroauric acid solution and 4.8 mL of 10 mM silver nitrate solution were added to 380 mL of 10 mM hexadecyltrimethylammonium bromide solution in sequence, stirred evenly, and then 20 mL of 0.1 M hydroquinone solution was added and stirred vigorously for 2 min to obtain the growth solution.

[0053] (3) Growth of single-surface gold nanorods: Take 1.6 mL of (1) seed solution and add it to (2) growth solution. Stir vigorously for 2 min and place in a 30℃ water bath for heating and incubation for more than 8 h to obtain single-surface gold nanorod solution.

[0054] TEM images of single-surface gold nanorod solutions are shown below. Figure 1 As shown, the synthesized single-surface gold nanorods are rod-shaped with a particle size of 10-15 nm and a length of 80-100 nm. Their UV-Vis absorption spectra are as follows. Figure 2 It exhibits two characteristic absorption peaks (510-550 nm is the TSPR peak, and 700-850 nm is the LSPR peak).

[0055] Example 2: Preparation of chiral helical gold nanorods

[0056] (1) Chiral induction incubation: Prepare chiral incubation environment solution: Mix 5 mM L-cysteine ​​solution and 15 mM 4-aminobenzylthiophenol solution at a volume ratio of 5:1. Take 12 μL of the mixture and add it to 300 μL of 0.1M hexadecyltrimethylammonium bromide solution. Take 1000 μL of (1) gold nanorods and add them to the above mixture. Stir well and incubate in a water bath at 30℃ for 3h.

[0057] (2) Chiral growth: 8 μL of 0.01 M silver nitrate solution, 14 μL of 0.01 M chloroauric acid solution and 15 μL of 0.1 M ascorbic acid solution were added to the incubated solution in (1) in sequence, and the solution was heated in a water bath at 70℃ for 1 h until the solution turned light purple to obtain a crude solution of chiral helical gold nanorods.

[0058] (3) Purification of chiral helical gold nanorods: Centrifuge the crude chiral helical gold nanorod solution from step (2) at 7500 rpm for 10 min, collect the centrifuged product, add hexadecyltrimethylammonium bromide solution, centrifuge again, and redisperse the precipitate in pure water to obtain a chiral helical gold nanorod solution. TEM images of the chiral helical gold nanorod solution are shown below. Figure 3 As shown, its spiral depth is 12 nm. Its UV-Vis absorption spectrum is as follows. Figure 4 It exhibits two characteristic absorption peaks (550 nm and 650 nm). The circular dichroism chromatogram of the chiral helical gold nanorod solution is shown below. Figure 5Its maximum CD signal is -340 mdeg. Its crystal plane analysis is as follows: Figure 6 This proves that it has a {111} crystal plane.

[0059] Comparative Example 1: CTAB only added during the preparation of gold nanorods

[0060] (1) Incubation: Take 300 μL of 0.1M hexadecyltrimethylammonium bromide solution and add 1000 μL of (1) gold nanorods to the above mixture and stir evenly. Incubate in a water bath at 30℃ for 3h.

[0061] (2) Growth: Add 8 μL of 0.01 M silver nitrate solution, 14 μL of 0.01 M chloroauric acid solution and 15 μL of 0.1 M ascorbic acid solution to the incubated solution in (1) in sequence, and heat in a water bath at 70℃ for 1 h until the solution turns light purple to obtain a crude solution of secondary growth gold nanorods.

[0062] (3) Purification of secondary-grown gold nanorods: Centrifuge the crude solution of secondary-grown gold nanorods from step (2) at 7500 rpm for 10 min, take the centrifuged product, add hexadecyltrimethylammonium bromide solution, centrifuge again, and redisperse the precipitate in pure water to obtain the secondary-grown gold nanorod solution. TEM images of the secondary-grown gold nanorod solution are shown below. Figure 7 As shown, under chiral incubation, the reduced gold / silver particles randomly adhered to the surface of the gold rod.

[0063] Comparative Example 2: Only L-cysteine ​​and 4-aminothiophenol were added during the preparation of gold nanorods.

[0064] (1) Incubation: Prepare chiral incubation environment solution: Mix 5 mM L-cysteine ​​solution and 15 mM 4-aminobenzylthiophenol solution at a volume ratio of 5:1. Take 12 μL of 5 mM L-cysteine ​​solution and add it to 1000 μL of (1) gold nanorods and stir evenly. Incubate in a water bath at 30℃ for 3h.

[0065] (2) Chiral growth: 8 μL of 0.01 M silver nitrate solution, 14 μL of 0.01 M chloroauric acid solution and 15 μL of 0.1 M ascorbic acid solution were added to the incubated solution in (1) in sequence, and the solution was heated in a water bath at 70℃ for 1 h until the solution turned light purple to obtain a crude solution of chiral helical gold nanorods.

[0066] (3) Purification of chiral helical gold nanorods: Centrifuge the crude chiral helical gold nanorod solution from step (2) at 7500 rpm for 10 min, collect the centrifuged product, add hexadecyltrimethylammonium bromide solution, centrifuge again, and redisperse the precipitate in pure water to obtain a chiral helical gold nanorod solution. TEM images of the chiral helical gold nanorod solution are shown below.Figure 8 As shown, the surface of the gold bar has protrusions but is smooth, and the spiral structure is not obvious, proving that the presence of CTAB plays a crucial role in sharpening the spiral morphology.

[0067] Comparative Example 3: Replacing bromide ions with iodide ions

[0068] The preparation was carried out according to the method of Example 2. In the preparation, the hexadecyltrimethylammonium bromide solution in step (1) was replaced with hexadecyltrimethylammonium iodide (CTAI) of the same concentration and volume, while the other conditions remained unchanged, and gold nanorods were prepared.

[0069] With Br - Different, I - It preferentially adsorbs on the {111} crystal plane, significantly more so than on the {100} crystal plane. Its mechanism of action is selective adsorption and growth inhibition on the {111} crystal plane. - Completely covering the {111} crystal plane, with only the {100} crystal plane growing, ultimately forming a non-helical "nano-arrowhead" morphology. For example... Figure 9 As shown, I - Growth inhibition was achieved through selective adsorption on the {111} crystal plane, interfering with Br - - The core process of chiral ligands synergistically regulates the directional growth of {111}, ultimately leading to the disappearance of the helical structure.

Claims

1. A method for preparing chiral helical gold nanorods grown with {111} crystal plane orientation, characterized in that, Includes the following steps: (1) Preparation of single-surface gold nanorods (1-1) Preparation of nano-gold seed solution: Nano-gold seed solution was synthesized using chloroauric acid solution, hexadecyltrimethylammonium bromide solution and sodium borohydride solution as raw materials; (1-2) Preparation of growth solution: The growth solution was prepared using chloroauric acid solution, silver nitrate solution, hexadecyltrimethylammonium bromide solution and hydroquinone solution as raw materials; (1-3) Growth of single-surface gold nanorods: The gold nanorod seed solution is added to the growth solution, stirred and placed in a water bath for heating and incubation to obtain a single-surface gold nanorod solution; (2) Preparation of chiral helical gold nanorods (2-1) Chiral induction incubation: Prepare chiral incubation environment solution: Mix 5-10 mM L-cysteine ​​solution and 15-30 mM 4-aminobenzylthiophenol solution at a volume ratio of 4-6:1 to obtain a mixed solution, then add hexadecyltrimethylammonium bromide solution, then add single-surface gold nanorods, stir evenly and incubate in water bath; (2-2) Chiral growth: Add silver nitrate solution, chloroauric acid solution and ascorbic acid solution to the solution after incubation in step (2-1), and heat in a water bath to obtain a crude solution of chiral helical gold nanorods; (3) Purification of chiral helical gold nanorods The crude solution of chiral helical gold nanorods was centrifuged, and the centrifuged product was added to a hexadecyltrimethylammonium bromide solution. After centrifugation again, the precipitate was redispersed in pure water to obtain a solution of chiral helical gold nanorods.

2. The preparation method according to claim 1, characterized in that, In steps (1-3), the water bath temperature is 15-40℃ and the time is 5-10 h.

3. The preparation method according to claim 1, characterized in that, In step (2-1), the water bath temperature is 15-30℃ and the time is 2-3 hours.

4. The preparation method according to claim 1, characterized in that, In step (2-1), the volume ratio of the mixture, hexadecyltrimethylammonium bromide solution and single-surface gold nanorod solution is 1-2:25-75:50-150.

5. The preparation method according to claim 4, characterized in that, In step (2-1), the concentration of the hexadecyltrimethylammonium bromide solution is 0.05-0.2 M.

6. The preparation method according to claim 1, characterized in that, In step (2-2), the volume ratio of silver nitrate solution, chloroauric acid solution and ascorbic acid solution is 1-4:1-4:1-4.

7. The preparation method according to claim 6, characterized in that, In step (2-2), the concentration of silver nitrate solution is 0.01-0.05 M, the concentration of chloroauric acid solution is 0.01-0.05 M, and the concentration of ascorbic acid solution is 0.04-0.2 M.

8. The preparation method according to claim 1, characterized in that, In step (2-2), the water bath heating temperature is 60-90℃ and the time is 1-4 h.

9. The preparation method according to claim 1, characterized in that, In step (3), the centrifugation conditions are 7000-8000 g and the time is 5-15 min.

10. A chiral helical gold nanorod, characterized in that, It is prepared by the method described in any one of claims 1-9.

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