CN1924117A - Preparation method of two-dimensional plane gold nano single crystal plate - Google Patents

Abstract

The invention discloses a method for preparing a two-dimensional planar gold micro-nano single crystal disk, which consists of the following steps: (1) configuring a template, mixing a nonionic surfactant, a coating agent and a chloroauric acid solution to obtain a uniform (2) leave the lyotropic liquid crystal to react at room temperature; (3) collect the obtained product, and observe the obtained product under a transmission electron microscope to present a regular triangular or hexagonal planar structure with a side length of about 1 ~10μm, thickness 10-100nm; single crystal properties and planar structure properties of the product were characterized by transmission electron microscopy. The method of the invention has the characteristics of effective controllable product morphology and particle size, simple and easy reaction, mild conditions, low template viscosity, easy removal after reaction, large product size control range, large output, clear structure and the like.

Description

Preparation method of a two-dimensional planar gold micro-nano single crystal disk

technical field

The invention relates to a preparation method of a nanometer material, in particular to a preparation method for preparing a two-dimensional plane gold micro-nano single crystal disk by utilizing hexagonal lysotropic liquid crystal chemical reduction.

Background technique

Noble metal nanomaterials have attracted widespread attention due to their unique properties in optics, electricity, acoustics, magnetism, and mechanics, as well as their possible application prospects. Recently, people have shown great interest in non-spherical noble metal nanomaterials. Non-spherical noble metal nanoparticles such as rods, dendrites, tubes and flakes have been used in certain applications, such as nanoscale flake silver powder for improving electronic paste. It is very important to improve the electrical properties and reduce the sintering temperature of the slurry. Among them, the template method is an effective method to prepare this kind of material. Using the ordered structure of lyotropic liquid crystals to guide its structure formation has the advantages of easy removal of templates and mild reaction conditions, and is a good way to synthesize nanostructured materials. Combined with the electrochemical deposition method, Attard et al. prepared porous films of metal platinum by using the lyotropic liquid crystal hexagonal phase (G S Attard, P N Bartlett, N R BColeman, J M Elliott, J R Owen, J H Wang. Mesoporous Platinum Films from Lyotropic Liquid Crystalline Phases.Science, 1997, Vol 278, 838-840), Yan et al. obtained metallic silver nanowires by using lyotropic liquid crystal reverse hexagonal phase (L M Huang, HT Wang, Z B Wang, A Mitra, K N Bozhilov, YS Yan. Nanowire Arrays Electrodeposited from Liquid crystalline Phase. Adv. Mater., 2002, Vol 14, 61-64). Regarding the preparation of gold nanodisks, relevant reports have also appeared at home and abroad. For example, Lee et al. used ultraviolet light irradiation and heating (70°C) for treatment (Kim J.U., Cha S.H., Shin K., Jho J.Y., Lee J.C..Preparation of Gold Nanowires and Nanosheets in Bulk Block Copolymer Phases under Mild Conditions.Adv.Mater., 2004, 16(5):459-464.), Wang et al. used liquid phase reduction (Sun X., Dong S., Wang E..Large-Scale Synthesis of Micrometer-Scale Single-Crystalline Au Plates of NanometerThickness by a Wet-Chemical Route. Angew. Chem. Int. Ed., 2004, 43(46): 6360-6363; Shankar S.S., Rai A., Ankamwar B., Singh A., Ahmad A., Sastry M.. Biological Syntiesis of Triangular Gold Nanoprisms. Nature Mater., 2004, 3: 482-488.), etc. However, the above methods have disadvantages such as the need for special preparation conditions, or the size of the obtained product is small, and the mechanism is not clear.

Contents of the invention

The problem to be solved by the present invention is to provide a method for preparing a large amount of two-dimensional planar gold micro-nano single crystal disks under mild conditions by using a simple and easy-to-operate lyotropic liquid crystal hexagonal phase template.

The purpose of the present invention is achieved through the following technical solutions.

Two reaction equations involved in the chemical reduction process of the nanometer material of the present invention are as follows:

The overall reaction equation is:

The above reaction is carried out in the polar water region in the lyotropic liquid crystal formed by the surfactant and the chloroauric acid aqueous solution, wherein the nonionic surfactant forming the liquid crystal is both a template agent and a reducing agent.

The preparation method of the two-dimensional planar gold micro-nano single crystal disk of the present invention, the steps are as follows:

(1) configure the template, the nonionic surfactant of 40-50% by mass percent and the cationic surfactant of coating agent cationic surfactant of 0.5-4% by mass percent and concentration are 0.01-0.05mol/dm ^chloroauric acid solution Mix to obtain a uniform hexagonal lyotropic liquid crystal;

(2) Standing the above-mentioned lyotropic liquid crystal at room temperature for 24 to 240 hours;

(3) Wash the above sample with water, remove the surfactant, and centrifuge at 3000rpm for 15 minutes, collect the precipitated product after centrifugation with a copper grid covered with a Formvor film, and then observe it with a transmission electron microscope. The resulting product appears regular A gold micro-nano single crystal disk with a regular triangle, truncated triangle and regular hexagonal structure with a side length of 1-10 μm.

Wherein, the nonionic surfactant described in step (1) is polyoxyethylene-polyoxypropylene-polyoxyethylene copolymer (EO ₂₀ PO ₇₀ EO ₂₀ , Pluronic P123).

Wherein, the cationic surfactant described in step (1) is cetyltrimethylammonium bromide.

Wherein, the mass percent of the nonionic surfactant described in step (1) is preferably 43-46wt%.

Wherein, the mass percentage of the cationic surfactant described in step (1) is preferably 1-2 wt%.

Wherein, the concentration of the chloroauric acid solution described in step (1) is preferably 0.02-0.04 mol/dm ³ .

Wherein, the standing time described in step (2) is preferably 48 to 150 hours.

Wherein, the gold micro-nano single crystal disk described in step (3) has a thickness of 10-100 nm.

Wherein, the EO ₂₀ PO ₇₀ EO ₂₀ (Pluronic P123) and the cetyltrimethylammonium bromide of 1% mass percent and 0.03mol /dm ³ mixed with chloroauric acid solution, and the standing reaction time is 120h.

Adopt the method of the present invention to prepare two-dimensional planar gold micro-nano single crystal disk, the obtained gold micro-nano single crystal disk has a regular triangular or hexagonal structure (as shown in Figure 3), and the side length is about 1-10 μm; the product Both the single crystal properties and the two-dimensional planar structural properties are characterized by transmission electron microscopy (as shown in Figure 4 and Figure 5), which can be applied to the fields of electronic devices and catalysis.

Compared with the existing technology of using lyotropic liquid crystal electrodeposition nanomaterials and other technologies for preparing two-dimensional gold discs, the method of the present invention has the following advantages: by controlling the ratio of protective agent/reductant and other reaction conditions, it can Effectively control the particle size and particle shape; the reaction is simple and easy, eliminating the uncontrollable mass transfer factors of electrochemical deposition; the template reaction is easy to remove, the reaction conditions are mild and controllable, and no other energy consumption is required, which is more It is beneficial to cost saving; controlled by the ordered template structure of the liquid crystal, the obtained product has a large amount and a clear structure, and the artificial control of the product structure and output is realized.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings.

Figure 1 is the phase diagram of the two-component system of Pluronic P123 and water, which is the basis for how to configure the lyotropic liquid crystal template.

Figure 2 is the small-angle X-ray scattering curve of lyotropic liquid crystal obtained by mixing Pluronic P123 with chloroauric acid aqueous solution (0.03M), further indicating that the template is a hexagonal phase.

Fig. 3 is a transmission electron microscope photograph of the product, and it can be observed that there are regular triangular or hexagonal nanostructures with a side length of about 4-10 μm and a thickness of 10-100 nm.

Figure 4 is the electron diffraction pattern of various shapes and individual particles of the product, wherein, a: triangle, b and c: truncated triangle, d: hexagon, e: single particle, indicating that the obtained single nanoparticles are all single crystals.

Figure 5 is an oblique electron microscope photo of the product, where a, b and c are three single crystal disks of different shapes, and d, e and f correspond to the product when the sample is tilted at -50°, indicating that the product has a two-dimensional plane structure.

Detailed ways

Embodiment 1. The preparation method of two-dimensional planar gold micro-nano single crystal disk, the steps are as follows:

(1) select mass percent as EO ₂₀ PO ₇₀ EO ₂₀ (Pluronic P123), 0.5wt% hexadecyltrimethylammonium bromide and 0.02mol/dm ³ chloroauric acid solution mixing of 40wt% to obtain uniform hexagonal Compatible liquid crystal;

(2) The above-mentioned lyotropic liquid crystal is left standing at room temperature, and the reaction time is 48h;

(3) The above sample was washed with water to remove the surfactant, and centrifuged at 3000 rpm for 15 minutes, and the precipitated product obtained after centrifugation was collected with a copper mesh covered with a Formvor membrane. The appearance of the product obtained by observing with a transmission electron microscope is a mixture of spherical particles and regular-shaped gold micro-nano single crystal disks, the side length of the gold micro-nano single crystal disks is 1-5 μm, and the thickness is 10-50 nm.

Embodiment 2. The preparation method of two-dimensional planar gold micro-nano single crystal disk, the steps are as follows:

(1) select mass percent as 45wt% EO ₂₀ PO ₇₀ EO ₂₀ (Pluronic P123), 1wt% hexadecyltrimethylammonium bromide and 0.03mol/ ^dm chloroauric acid solution mix, obtain uniform hexagonal phase Lyotropic liquid crystals;

(2) The above-mentioned lyotropic liquid crystal is left standing at room temperature, and the reaction time is 120h;

(3) The above sample was washed with water to remove the surfactant, and centrifuged at 3000 rpm for 15 minutes, and the precipitated product obtained after centrifugation was collected with a copper mesh covered with a Formvor membrane. The appearance of the product obtained by observation with a transmission electron microscope is gold disc-shaped particles with regular shape. The side length of the single crystal disc is about 4-10 μm and the thickness is 10-100 nm, as shown in FIG. 3 . Further electron diffraction analysis (as shown in FIG. 4 ) and oblique observation experiments (as shown in FIG. 5 ) of the product showed that the product was a gold single crystal and had a two-dimensional planar structure.

Embodiment 3. The preparation method of two-dimensional planar gold micro-nano single crystal disk, the steps are as follows:

(1) Selecting mass percent as 50wt% Pluronic P123, 4wt% cetyltrimethylammonium bromide mixed with 0.04mol/ ^dm chloroauric acid solution to obtain a uniform hexagonal lyotropic liquid crystal;

(2) The above-mentioned lyotropic liquid crystal is left standing at room temperature, and the reaction time is 240h;

(3) The above sample was washed with water to remove the surfactant, and centrifuged at 3000 rpm for 15 minutes, and the precipitated product obtained after centrifugation was collected with a copper mesh covered with a Formvor membrane. The appearance of the product obtained by observing with a transmission electron microscope is a regular-shaped gold micro-nano single crystal disk, the side length is 2-10 μm, and the thickness is 10-100 nm.

Claims (10)

1. A method for preparing a two-dimensional planar gold micro-nano single crystal disk, which is prepared by using a hexagonal phase solution-induced liquid crystal chemical reduction method, and the equation is as follows The overall reaction equation is: Specific steps are as follows: (1) configuration template, the nonionic surfactant of 40-50% by mass percentage and the cationic surfactant of 0.1-4% by mass percentage are mixed with the concentration of 0.01-0.05mol/ ^dm chloroauric acid solution to obtain Uniform hexagonal lyotropic liquid crystal; (2) Standing the above-mentioned lyotropic liquid crystal at room temperature for 24-240 hours; (3) Wash the above sample with water, remove the surfactant, and centrifuge at 3000rpm for 15 minutes, collect the precipitated product after centrifugation with a copper mesh covered with Formvor film, and then observe it with a transmission electron microscope. The resulting product is regular The structure of regular triangle, truncated triangle and regular hexagon is a gold micro-nano single crystal disc with side length of 1-10 μm. 2. the preparation method of a kind of two-dimensional planar gold micro-nano single crystal disk as claimed in claim 1, is characterized in that, the nonionic surfactant described in step (1) is polyoxyethylene-polyoxypropylene-polyethylene oxide Oxyethylene copolymer. 3. the preparation method of a kind of two-dimensional planar gold micro-nano single crystal disk as claimed in claim 1 is characterized in that, the cationic surfactant described in step (1) is cetyltrimethylammonium bromide . 4. the preparation method of a kind of two-dimensional planar gold micro-nano single crystal disk as claimed in claim 1 or 2 is characterized in that, the mass percent of the nonionic surfactant described in step (1) is 43-46% . 5. The method for preparing a two-dimensional planar gold micro-nano single crystal disk as claimed in claim 1 or 3, wherein the mass percentage of the cationic surfactant in step (1) is 1-2%. 6 . The method for preparing a two-dimensional planar gold micro-nano single crystal disc according to claim 1 , wherein the concentration of the chloroauric acid solution in step (1) is 0.02-0.04 mol/dm ³ . 7. The method for preparing a two-dimensional planar gold micro-nano single crystal disk as claimed in claim 1, wherein the standing reaction time in step (2) is 48-150 hours. 8. The method for preparing a two-dimensional planar gold micro-nano single crystal disc as claimed in claim 1, wherein the thickness of the gold micro-nano single crystal disc of the product in step (3) is 10-100 nm. 9. the preparation method of a kind of two-dimensional planar gold micro-nano single crystal disk as claimed in claim 1 or 2 or 3, is characterized in that, in the described step (1), the selection mass percent is 45% polyoxyethylene- Polyoxypropylene-polyoxyethylene copolymer and 1% by mass of cetyltrimethylammonium bromide are mixed with 0.03mol/dm ³ chloroauric acid solution. 10. The method for preparing a two-dimensional planar gold micro-nano single crystal disk according to claim 1 or 7, wherein the standing reaction time of the step (2) is 120 h.

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