Bullet-shaped nano motor with tail cavity structure and preparation method and application of bullet-shaped nano motor

Abstract

The invention belongs to the field of nano materials, and particularly relates to a bullet-shaped nano motor with a tail cavity structure and a preparation method and application of the bullet-shaped nano motor, and the bullet-shaped nano motor is composed of gold nano bipyramid AuNBPs located at the head and the cavity structure located at the tail. One end of the gold nano bipyramid AuNBPs is exposed outside to form a tip structure, and the other end of the gold nano bipyramid AuNBPs is wrapped by the cavity structure to form a rod-shaped structure. The invention innovatively develops a novel nano material with a bullet-shaped cavity structure, which is prepared on the basis of an in-situ replacement mode of active displacers such as H2PdCl4, K2PtCl4, KMnO4 and the like, and cavity shell layer elements on the cavity structure can be customized and adjusted according to the active displacers. The size of the cavity structure can be regulated and controlled by controlling the replacement time of the active replacement agent; the multi-alloy composition on the surface of the cavity shell layer can be adjusted by changing the types of the active displacers; the thickness of the cavity shell layer can be controlled by adjusting the concentration of the active displacer.

Description

Technical Field

[0001] The invention belongs to the field of nano materials, and in particular relates to a bullet-shaped nano motor with a tail cavity structure and a preparation method and application thereof. Background Art

[0002] Hollow nanomaterials have attracted extensive research interest from multiple disciplines due to their unique structures and excellent properties. Due to their high specific surface area, well-defined active sites, defined interstitial spaces, and adjustable mass transfer rates, hollow nanostructures can be used as excellent catalysts, supports, and reactors for various catalytic applications. However, the difficulty of their synthesis and development has greatly limited their widespread application.

[0003] Due to the easy-to-manipulate microstructure and limited local voids, studies have found that well-designed hollow micro-nanostructures have shown excellent performance as the main materials for various emerging research fields, such as catalysis, sensing, biomedicine, etc. With the great progress in the characterization of nanocrystal microstructures and the basic growth mechanism, cavity nanomaterials have become one of the research hotspots in modern nanoscience, especially the development of synthesis methods and structure-related properties. Due to the high specific surface area and clear geometric position of the cavity structure, it can be used as an ideal carrier to accommodate a large number of localized single atoms. The rational design of single-atom cavity nanomaterials may provide unique insights into the study of single-atom catalytic mechanisms and the development of catalysts for complex reactions. There are at least four types of positions in the cavity nanostructure that can fix functional molecules, namely the outer surface of the shell, the cavity inside the shell, the inner surface of the shell, and the gap between the shells. For cavity nanomaterials, by finely controlling the geometric parameters of the shell (such as porosity, pore size, pore orientation, shell thickness, cavity size, etc.), the multifunctionalization of cavity nanomaterials such as targeted carriers, precise controlled release, and surface doping can be achieved. Therefore, the development of a new type of cavity-structured nanomaterial can provide unique microscopic insights into the relevant catalytic mechanisms. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a bullet-shaped nanomotor with a tail cavity structure and a preparation method and application thereof. The present invention innovatively develops a method based on in-situ replacement of active displacers such as H2PdCl4, K2PtCl4, KMnO4 to prepare a new type of bullet-shaped cavity structure nanomaterial, and the cavity shell elements on the cavity structure can be customized and adjusted according to the active displacer. By controlling the replacement time of the active displacer, the size of the cavity structure can be regulated; by changing the type of active displacer, the multi-alloy composition on the surface of the cavity shell can be adjusted; by adjusting the concentration of the active displacer, the thickness of the cavity shell can be controlled.

[0005] To achieve the above object, the present invention is implemented by the following technical solutions:

[0006] The present invention provides a bullet-shaped nanomotor with a tail cavity structure, wherein the bullet-shaped nanomotor is composed of gold nanobipyramids AuNBPs located at the head and a cavity structure located at the tail; one end of the gold nanobipyramids AuNBPs is exposed to form a tip structure, and the other end is wrapped by the cavity structure to form a rod-shaped structure.

[0007] As a further optimization solution of the present invention, the cavity shell elements on the cavity structure include Au, Ag and other metal elements, and the other metal elements include any one of Pd, Pt and Mn.

[0008] The present invention also provides a method for preparing a bullet-shaped nanomotor with a tail cavity structure, the preparation method comprising:

[0009] preparing Au seeds;

[0010] Using the Au seeds to induce growth and form gold nanobipyramids AuNBPs;

[0011] A layer of silver nanomaterial is coated and grown on the surface of the gold nanobipyramid AuNBPs to form AuNBPs@Ag nanorods;

[0012] Asymmetric etching is performed on the AuNBPs@Ag nanorods to obtain bullet-shaped AuNBPs@Ag nanomaterials;

[0013] The bullet-shaped AuNBPs@Ag nanomaterial is subjected to a replacement reaction to finally obtain a bullet-shaped nanomotor with a tail cavity structure.

[0014] As a further optimization scheme of the present invention, the preparation of the gold nanobipyramid AuNBPs includes:

[0015] In a solution containing hexadecyltrimethylammonium bromide, chloroauric acid, silver nitrate, hydrochloric acid and ascorbic acid, Au seeds were added to form gold nanobipyramids AuNBPs through a self-assembly and growth process.

[0016] As a further optimization scheme of the present invention, the preparation of the AuNBPs@Ag nanorods includes:

[0017] Gold nanobipyramids AuNBPs were mixed with hexadecyltrimethylammonium chloride, silver nitrate and ascorbic acid, and a silver nanolayer was grown on the surface of the gold nanobipyramids AuNBPs through a reduction reaction of silver ions.

[0018] As a further optimization scheme of the present invention, the asymmetric etching step includes:

[0019] A mixed solution containing chloroauric acid, ascorbic acid, sodium hydroxide and hexadecyltrimethylammonium bromide is prepared and stirred evenly at room temperature; the AuNBPs@Ag nanorods are added to the mixed solution and reacted in a water bath at 25-35° C. for 5-8 hours, and purified after the reaction is completed;

[0020] The purified nanorods were redispersed in a solution containing hexadecyltrimethylammonium bromide, and sodium bicarbonate, hydrogen peroxide, potassium thiocyanate and cobalt nitrate were added in sequence. The reaction was carried out in a water bath at 70-90°C for 15-20 minutes. After the reaction was completed, the nanorods were purified to obtain bullet-shaped AuNBPs@Ag nanomaterials.

[0021] As a further optimization scheme of the present invention, the steps of forming a cavity structure at the tail of the bullet-shaped AuNBPs@Ag nanomaterial include:

[0022] The bullet-shaped AuNBPs@Ag nanomaterial is dispersed in a solution containing hexadecyltrimethylammonium bromide, and then a solution containing an active displacer is added and mixed and stirred. The mixture is reacted at 50-70°C for 2-5 hours. After the reaction is completed, the mixture is purified to obtain a bullet-shaped nanomotor with a tail cavity structure.

[0023] As a further optimization scheme of the present invention, the active replacement agent includes any one of H2PdCl4, K2PtCl4, and KMnO4.

[0024] The present invention also provides an application of a bullet-shaped nanomotor with a tail cavity structure in catalytic degradation of organic dye pollutants.

[0025] As a further optimization scheme of the present invention, the organic dye pollutant includes methylene blue.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention adopts active replacement technology, which is a novel method that can effectively prepare nanomaterials with cavity structures. During the preparation process, by controlling the type, concentration and reaction time of the active replacement agent, the size of the cavity structure, the thickness of the shell layer and the composition of the shell layer elements can be accurately adjusted. The composition of the cavity shell layer elements can be customized as needed, which increases the application flexibility of the material.

[0028] (2) The present invention uses asymmetric etching technology to achieve precise control of the morphology of nanomaterials, and obtains a unique bullet-shaped morphology that gives it good directionality, wherein: the bullet-shaped structure can reduce the resistance of the nanomotor in the fluid and improve its directional movement ability in the solution; experimental results show that the prepared bullet-shaped cavity structure nanomaterials show high efficiency in catalytic degradation of methylene blue, which is of great significance for environmental governance and the chemical industry. Especially in the field of catalysis, the cavity structure can provide more active sites and improve catalytic efficiency and selectivity.

[0029] (3) The present invention adopts a one-pot hydrothermal method to prepare AuNBPs@Ag nanorods, and then obtains the cavity structure through asymmetric etching and active replacement. The whole process is simple and easy, which reduces the difficulty of preparation and technical threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a transmission electron micrograph of the bullet-shaped nanomotor prepared by high concentration H2PdCl4 (≥0.5M) substitution in Example 1.

[0031] Figure 2 This is a transmission electron micrograph of the bullet-shaped nanomotor prepared by low-concentration H2PdCl4 (<0.5M) substitution in Example 1.

[0032] Figure 3 This is a transmission electron micrograph of the bullet-shaped nanomotor prepared by high concentration K2PtCl4 (≥0.5M) substitution in Example 2.

[0033] Figure 4 This is a transmission electron micrograph of the bullet-shaped nanomotor prepared by low-concentration K2PtCl4 (<0.5M) substitution in Example 2.

[0034] Figure 5 The mapping image and line scan image of the bullet-shaped nanomotor prepared in Example 1 are shown in FIG. Figure 5 a in it is a Mapping graph, Figure 5 b in the figure is the line scan of the local features in the Mapping image.

[0035] Figure 6 The mapping image and line scan image of the bullet-shaped nanomotor prepared in Example 2 are shown in FIG. Figure 6 a in the figure is a Mapping graph. Figure 6 b in the figure is the line scan of the local features in the Mapping image.

[0036] Figure 7 The catalytic degradation rates of methylene blue by the bullet-shaped nanomotors prepared in Example 1 and Example 2 at different time points. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred implementation scheme of the present invention is described below in conjunction with specific embodiments, but it should not be understood as limiting the present invention and is only used as an example.

[0038] On the one hand, the present invention provides a bullet-shaped nanomotor with a tail cavity structure, wherein the bullet-shaped nanomotor is composed of gold nanobipyramids AuNBPs located at the head and a cavity structure located at the tail; one end of the gold nanobipyramids AuNBPs is exposed to form a tip structure, and the other end is wrapped by the cavity structure to form a rod-shaped structure.

[0039] In some embodiments, the cavity shell elements on the cavity structure include Au, Ag and other metal elements, and the other metal elements include any one of Pd, Pt, and Mn.

[0040] On the other hand, the present invention also provides a method for preparing a bullet-shaped nanomotor with a tail cavity structure, the preparation method comprising:

[0041] Synthesis of Au seeds:

[0042] Weigh 150-180 mg of hexadecyltrimethylammonium chloride (CTAC) and dissolve it in 10 ml of ultrapure water. After it is completely dissolved, add 50 μl of 50-80 mM HAuCl4 solution, followed by 9-12 mg of citric acid. Stir for 3-5 minutes, quickly add 250 μl of 30-60 mM NaBH4, stir for 3-5 minutes, and stir in an 80-90°C oil bath for 90-120 minutes.

[0043] Synthesis of AuNBPs:

[0044] Add 200 ml of 80-150 mM hexadecyltrimethylammonium bromide (CTAB), 3 ml of 20-50 mM HAuCl4 solution, 2 ml of 10-20 mM AgNO3 solution, 4 ml of 1-3 M HCl solution, and 2 ml of 80-120 mM ascorbic acid (AA) solution to a round-bottom flask, and stir at room temperature for 3-5 min. Then add 3-5 ml of the Au seeds prepared above. Incubate in a water bath at 25-35 °C for 3-5 h.

[0045] Synthesis of AuNBPs@Ag nanorods:

[0046] The AuNBPs prepared above were purified by centrifugation at 9500rpm for 8-12min, and purified by centrifugation twice. The purified AuNBPs were then redispersed in ultrapure water until the absorbance was 0.5-1. 10-30ml of the redispersed AuNBPs were added to 30ml, 30-50mM CTAC solution. Stir and disperse for 3-5min, then add 300-400μl of AgNO3 solution, stir and disperse for 3-5min, and then add 0.1-0.5M ascorbic acid, which is half the volume of the AgNO3 solution. Water bath at 50-70℃ for 3-6h. After the reaction is complete, centrifuge and purify at 9500rpm for 8-12min, and redisperse in 10-20ml ultrapure water.

[0047] Asymmetric etching of AuNBPs@Ag nanorods:

[0048] Add 750μl of 0.01-0.03M HAuCl4 solution, 500μl of 0.1-0.3M AA solution, 500μl of 0.05-0.15M NaOH solution, and 50ml of 0.1-0.3M CTAB solution to a round-bottom flask. After adding all the solution, stir at room temperature for 3-5min. Then add 10-15ml of the above-dispersed AuNBPs@Ag nanorods and place in a water bath at 25-35℃ for 5-8h. After the reaction is complete, centrifuge at 9500rpm for purification.

[0049] The AuNBPs@Ag nanorods purified by centrifugation were redispersed in 200ml of 1-5mM CTAB solution. Then, 2ml of 0.1-0.5M NaHCO3 solution, 2ml of 0.1-0.5M H2O2 solution, 1ml of 0.05-0.15M KSCN solution, and 2ml of 10-30μM Co(NO3)2 solution were gradually added. Incubate in a water bath at 70-90℃ for 15-20min. Centrifuge at 9500rpm for purification.

[0050] Mechanism analysis of asymmetric etching: In the asymmetric etching process, HAuCl4 is used to break the balance and perform asymmetric etching. - The standard electrode potential of Au / Au is 1.002, and the standard electrode potential of Ag / AgCl is -0.222. - The standard electrode potentials of Au / Au and Ag / AgCl indicate that the redox reaction between the two can proceed spontaneously. Therefore, during the etching process, HAuCl4 can replace the Ag in the AuNBPs@Ag rods with free Ag. +, thus achieving the purpose of etching. However, due to the high symmetry of the two ends of the AuNBPs@Ag rod, the HAuCl4 etching process initially proceeds from both ends simultaneously, but as the etching reaction occurs, the etching reaction at one end must first break the balance, and under the action of reaction kinetics, the subsequent HAuCl4 etching process will be concentrated on the end that breaks the balance, thus leading to the occurrence of asymmetric etching.

[0051] Preparation of AuNBPs@Ag cavity structure:

[0052] The purified AuNBPs@Ag was redispersed in 5 ml of 0.1-0.5 M CTAB, mixed and stirred for 3-5 min, and then 100 μl of 0.01-0.07 M H2PdCl4 / K2PtCl4 / KMnO4 was added for replacement. The reaction was carried out in an oven at 50-70 ° C for 2-5 h. After the reaction was complete, centrifugation was performed at 9500 rpm to purify the nanomotor with a tail cavity structure.

[0053] Cavity structure formation mechanism:

[0054] PtCl6 2- / PtCl4 2- The standard electrode potential is 0.68v, PdCl4 2- / Pd standard electrode potential is 0.75v, MnO4 - / Mn 2+ The standard electrode potential is 1.507v, the standard electrode potential of Ag / AgCl is -0.222v, compared with PtCl6 2- / PtCl4 2- 、MnO4 - / Mn 2+ 、PdCl4 2- The standard electrode potentials of Ag / Pd and Ag / AgCl show that the redox reaction between the two can proceed spontaneously. Therefore, H2PtCl6, H2PdCl4 and KMnO4 can replace the Ag in the Ag rod with free Ag in the solution. + Since the substitution reaction between H2PtCl6, H2PdCl4 and KMnO4 and Ag rods is relatively mild, and different from the severe etching of HAuCl4, it will not achieve the etching effect of HAuCl4, but will be replaced into a cavity structure. Then, by controlling the substitution time (2-5h), the remaining elemental Ag content in the Ag rod can be controlled, thereby achieving the purpose of controlling the thickness of the cavity Ag shell.

[0055] The present invention also provides an application of a bullet-shaped nanomotor with a tail cavity structure in catalytic degradation of organic dye pollutants, wherein the organic dye pollutants include methylene blue.

[0056] The experimental methods or test methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are obtained from conventional commercial channels or prepared by conventional methods unless otherwise specified.

[0057] Example 1

[0058] Weigh 150 mg of hexadecyltrimethylammonium chloride (CTAC) and dissolve it in 10 ml of ultrapure water. After it is completely dissolved, add 50 μl of 50 mM HAuCl4 solution, followed by 9 mg of citric acid. Stir for 3 min, quickly add 250 μl of 30 mM NaBH4, stir for 3 min, and stir in an 80°C oil bath for 90 min.

[0059] Add 200 ml of 80 mM hexadecyltrimethylammonium bromide (CTAB), 3 ml of 20 mM HAuCl4 solution, 2 ml of 10 mM AgNO3 solution, 4 ml of 1 M HCl solution, and 2 ml of 80 mM ascorbic acid (AA) solution to a round-bottom flask and stir for 3 min at room temperature. Then add 3 ml of the Au seeds prepared above. Incubate in a water bath at 25 °C for 3 h.

[0060] The AuNBPs prepared above were purified by centrifugation at 9500rpm for 8min, and centrifuged twice. The purified AuNBPs were then redispersed in ultrapure water until the absorbance was 0.5. 10ml of the redispersed AuNBPs was added to 30ml, 30mM CTAC solution. Stir and disperse for 3min, then add 300μl of AgNO3 solution, stir and disperse for 3min, and then add 0.1M ascorbic acid with half the volume of the AgNO3 solution. Water bath at 50℃ for 3h. After the reaction is complete, centrifuge and purify at 9500rpm for 8min, and redisperse in 10ml ultrapure water.

[0061] Add 750μl of 0.01M HAuCl4 solution, 500μl of 0.1M AA solution, 500μl of 0.05M NaOH solution, and 50ml of 0.1M CTAB solution to a round-bottom flask. After adding all the solution, stir at room temperature for 3min. Then add 10ml of the above-dispersed AuNBPs@Ag nanorods and place in a water bath at 25℃ for 5h. After the reaction is complete, centrifuge at 9500rpm for purification.

[0062] The AuNBPs@Ag nanorods purified by centrifugation were redispersed in 200 ml of 1 mM CTAB solution. Then, 2 ml of 0.1 M NaHCO3 solution, 2 ml of 0.1 M H2O2 solution, 1 ml of 0.05 M KSCN solution, and 2 ml of 10 μM Co(NO3)2 solution were gradually added. The mixture was placed in a water bath at 70°C for 20 min. The mixture was centrifuged at 9500 rpm for purification.

[0063] The purified AuNBPs@Ag was redispersed in 5 ml of 0.1 M CTAB and stirred for 5 min. Then 100 μl of 0.01 M H2PdCl4 was added for replacement and reacted in an oven at 50 °C for 2 h. After the reaction was complete, the bullet-shaped nanomotor was obtained by centrifugation at 9500 rpm.

[0064] Example 2

[0065] Weigh 160 mg of hexadecyltrimethylammonium chloride (CTAC) and dissolve it in 10 ml of ultrapure water. After it is completely dissolved, add 50 μl of 60 mM HAuCl4 solution, followed by 10 mg of citric acid. Stir for 5 min, quickly add 250 μl of 50 mM NaBH4, stir for 5 min, and stir in a 90°C oil bath for 120 min.

[0066] Add 200 ml of 100 mM hexadecyltrimethylammonium bromide (CTAB), 3 ml of 30 mM HAuCl4 solution, 2 ml of 15 mM AgNO3 solution, 4 ml of 2 M HCl solution, and 2 ml of 100 mM ascorbic acid (AA) solution to a round-bottom flask and stir for 5 min at room temperature. Then add 4 ml of the Au seeds prepared above. Incubate in a water bath at 30 °C for 5 h.

[0067] The AuNBPs prepared above were purified by centrifugation at 9500rpm for 12min, and centrifuged twice. The purified AuNBPs were then redispersed in ultrapure water until the absorbance was 0.7. Take 20ml of the redispersed AuNBPs to 30ml, 40mM CTAC solution. Stir and disperse for 5min, then add 350μl of AgNO3 solution, stir and disperse for 5min, and then add 0.3M ascorbic acid with half the volume of the AgNO3 solution. Water bath at 60℃ for 5h. After the reaction is complete, centrifuge and purify at 9500rpm for 10min, and redisperse in 15ml ultrapure water.

[0068] Add 750μl of 0.02M HAuCl4 solution, 500μl of 0.2M AA solution, 500μl of 0.10M NaOH solution, and 50ml of 0.2M CTAB solution to a round-bottom flask. After adding all the solution, stir at room temperature for 5min. Then add 12ml of the above-dispersed AuNBPs@Ag nanorods and place in a water bath at 30℃ for 6h. After the reaction is complete, centrifuge at 9500rpm for purification.

[0069] The AuNBPs@Ag nanorods purified by centrifugation were redispersed in 200 ml of 3 mM CTAB solution. Then, 2 ml of 0.3 M NaHCO3 solution, 2 ml of 0.3 M H2O2 solution, 1 ml of 0.10 M KSCN solution, and 2 ml of 20 μM Co(NO3)2 solution were gradually added. Incubate in a water bath at 80 °C for 30 min. Centrifuge at 9500 rpm for purification.

[0070] The purified AuNBPs@Ag was redispersed in 5 ml of 0.3 M CTAB and stirred for 5 min. Then 100 μl of 0.05 M K2PtCl4 was added for replacement. The mixture was reacted in an oven at 60 °C for 4 h. After the reaction was complete, the bullet-shaped nanomotor was obtained by centrifugation at 9500 rpm.

[0071] Example 3

[0072] Weigh 180 mg of hexadecyltrimethylammonium chloride (CTAC) and dissolve it in 10 ml of ultrapure water. After it is completely dissolved, add 50 μl of 80 mM HAuCl4 solution, followed by 12 mg of citric acid. Stir for 5 min, quickly add 250 μl of 60 mM NaBH4, stir for 5 min, and stir in a 90°C oil bath for 120 min.

[0073] Add 200 ml of 150 mM hexadecyltrimethylammonium bromide (CTAB), 3 ml of 50 mM HAuCl4 solution, 2 ml of 20 mM AgNO3 solution, 4 ml of 3 M HCl solution, and 2 ml of 120 mM ascorbic acid (AA) solution to a round-bottom flask and stir for 5 min at room temperature. Then add 5 ml of the Au seeds prepared above. Incubate in a water bath at 35 °C for 5 h.

[0074] The AuNBPs prepared above were purified by centrifugation at 9500rpm for 12min, and centrifuged twice. The purified AuNBPs were then redispersed in ultrapure water until the absorbance was 1. 30ml of the redispersed AuNBPs were added to 30ml, 50mM CTAC solution. Stir and disperse for 5min, then add 400μl of AgNO3 solution, stir and disperse for 5min, and then add 0.5M ascorbic acid with half the volume of the AgNO3 solution. Water bath at 70℃ for 6h. After the reaction is complete, centrifuge and purify at 9500rpm for 12min, and redisperse in 20ml ultrapure water.

[0075] Add 750 μl of 0.03M HAuCl4 solution, 500 μl of 0.3M AA solution, 500 μl of 0.15M NaOH solution, and 50 ml of 0.3M CTAB solution to a round-bottom flask. After adding all the solution, stir at room temperature for 5 min. Then add 15 ml of the above-dispersed AuNBPs@Ag nanorods and place in a water bath at 35°C for 8 h. After the reaction is complete, centrifuge at 9500 rpm for purification.

[0076] The AuNBPs@Ag nanorods purified by centrifugation were redispersed in 200 ml of 5 mM CTAB solution. Then, 2 ml of 0.5 M NaHCO3 solution, 2 ml of 0.5 M H2O2 solution, 1 ml of 0.15 M KSCN solution, and 2 ml of 30 μM Co(NO3)2 solution were gradually added. Incubate in a water bath at 90 °C for 30 min. Centrifuge at 9500 rpm for purification.

[0077] The purified AuNBPs@Ag was redispersed in 5 ml of 0.5 M CTAB and stirred for 5 min. Then 100 μl of 0.07 M KMnO4 was added for replacement and reacted in an oven at 70 °C for 5 h. After the reaction was complete, the bullet-shaped nanomotor was obtained by centrifugation at 9500 rpm.

[0078] Figure 1 This is a transmission electron micrograph of the bullet-shaped nanomotor prepared by high concentration H2PdCl4 (≥0.5M) substitution in Example 1. Figure 2 This is a transmission electron micrograph of a bullet-shaped nanomotor prepared by substitution with low concentration H2PdCl4 (<0.5M) in Example 1. Figure 1 and Figure 2 It can be seen that it is composed of high-contrast AuNBPs and low-contrast hollow Ag shells. By using H2PdCl4 substitution, the elemental Ag in the solid AuNBPs@Ag shell is replaced with AgCl precipitation, thereby obtaining the AuNBPs@Ag hollow structure, and at the same time, the residual Pd is replaced in the Ag hollow shell. Figure 1 To use high concentration H2PdCl4 (≥0.5M) for replacement, Figure 2 Use low concentration H2PdCl4 (<0.5M) to replace Figure 1 It can be seen that its shell is significantly thicker than that replaced by low concentration H2PdCl4 (<0.5M).

[0079] Figure 3 This is a transmission electron micrograph of the bullet-shaped nanomotor prepared by high concentration K2PtCl4 (≥0.5M) substitution in Example 2. Figure 4 This is a transmission electron micrograph of a bullet-shaped nanomotor prepared by substitution with low concentration K2PtCl4 (<0.5M) in Example 2. Figure 3 and Figure 4 It can be seen that it is composed of high-contrast AuNBPs and low-contrast hollow Ag shells. By using K2PtCl4 substitution, the elemental Ag in the solid AuNBPs@Ag shell is replaced with AgCl precipitation, thereby obtaining the AuNBPs@Ag hollow structure, and at the same time, the residual Pt is replaced in the Ag hollow shell. Figure 3 In order to use high concentration K2PtCl4 (≥0.5M) for replacement, Figure 3 It can be seen that its shell is significantly thicker than that replaced by low concentration K2PtCl4 (<0.5M).

[0080] Figure 5 The mapping image and line scan image of the bullet-shaped nanomotor prepared in Example 1 are shown in FIG. Figure 5 a in the figure is a Mapping graph. Figure 5 b in the figure is the line scan of the local features in the Mapping figure. Figure 5 From a in , we can see that Au is mainly distributed in the bipyramid structure and the cavity shell. In addition, Ag and Pd are also distributed in the cavity shell. Figure 5 From b, we can see that the distribution of each element is highly consistent with the line scanning direction, indicating that the bullet-shaped nanomotor with a tail cavity structure was successfully prepared.

[0081] Figure 6 The mapping image and line scan image of the bullet-shaped nanomotor prepared in Example 2 are shown in FIG. Figure 6 a in the figure is a Mapping graph. Figure 6 b in the figure is the line scan of the local features in the Mapping figure. Figure 6 From a in , we can see that Au is mainly distributed in the bipyramid structure and the cavity shell. In addition, Ag and Pt are also distributed in the cavity shell. Figure 6 From b, we can see that the distribution of each element is highly consistent with the line scanning direction, indicating that the bullet-shaped nanomotor with a tail cavity structure was successfully prepared.

[0082] Figure 7 The catalytic degradation rates of methylene blue by the bullet-shaped nanomotors prepared in Example 1 and Example 2 at different time points. Figure 7 It can be seen that compared with the control group with only H2O added, the catalytic degradation efficiency of the cavity AuNBPs@Ag replaced by K2PtCl4 and H2PdCl4 for methylene blue is as high as 85% and 92% within 60 min, showing a high catalytic degradation efficiency for organic dyes.

[0083] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A bullet-shaped nanomotor with a tail cavity structure, characterized in that: The bullet-shaped nanomotor is composed of gold nanobipyramids AuNBPs at the head and a cavity structure at the tail; one end of the gold nanobipyramids AuNBPs is exposed to form a tip structure, and the other end is wrapped by the cavity structure to form a rod-shaped structure.

2. The bullet-shaped nanomotor with a tail cavity structure according to claim 1, characterized in that: The cavity shell elements on the cavity structure include Au, Ag and other metal elements, and the other metal elements include any one of Pd, Pt and Mn.

3. A method for preparing a bullet-shaped nanomotor with a tail cavity structure, characterized in that: The preparation method comprises: preparing Au seeds; Using the Au seeds to induce growth and form gold nanobipyramids AuNBPs; A layer of silver nanomaterial is coated and grown on the surface of the gold nanobipyramid AuNBPs to form AuNBPs@Ag nanorods; Asymmetric etching is performed on the AuNBPs@Ag nanorods to obtain bullet-shaped AuNBPs@Ag nanomaterials; The bullet-shaped AuNBPs@Ag nanomaterial is subjected to a replacement reaction to finally obtain a bullet-shaped nanomotor with a tail cavity structure.

4. The method for preparing the bullet-shaped nanomotor with a tail cavity structure according to claim 3, characterized in that: The preparation of the gold nanobipyramid AuNBPs includes: In a solution containing hexadecyltrimethylammonium bromide, chloroauric acid, silver nitrate, hydrochloric acid and ascorbic acid, Au seeds were added to form gold nanobipyramids AuNBPs through a self-assembly and growth process.

5. The method for preparing the bullet-shaped nanomotor with a tail cavity structure according to claim 3, characterized in that: The preparation of the AuNBPs@Ag nanorods comprises: Gold nanobipyramids AuNBPs were mixed with hexadecyltrimethylammonium chloride, silver nitrate and ascorbic acid, and a silver nanolayer was grown on the surface of the gold nanobipyramids AuNBPs through a reduction reaction of silver ions.

6. The method for preparing the bullet-shaped nanomotor with a tail cavity structure according to claim 3, characterized in that: The asymmetric etching step comprises: A mixed solution containing chloroauric acid, ascorbic acid, sodium hydroxide and hexadecyltrimethylammonium bromide is prepared and stirred evenly at room temperature; the AuNBPs@Ag nanorods are added to the mixed solution and reacted in a water bath at 25-35° C. for 5-8 hours, and purified after the reaction is completed; The purified nanorods were redispersed in a solution containing hexadecyltrimethylammonium bromide, and sodium bicarbonate, hydrogen peroxide, potassium thiocyanate and cobalt nitrate were added in sequence. The reaction was carried out in a water bath at 70-90°C for 15-20 minutes. After the reaction was completed, the nanorods were purified to obtain bullet-shaped AuNBPs@Ag nanomaterials.

7. The method for preparing the bullet-shaped nanomotor with a tail cavity structure according to claim 3, characterized in that: The steps of forming the tail cavity structure of the bullet-shaped AuNBPs@Ag nanomaterial include: The bullet-shaped AuNBPs@Ag nanomaterial is dispersed in a solution containing hexadecyltrimethylammonium bromide, and then a solution containing an active displacer is added and mixed and stirred. The mixture is reacted at 50-70°C for 2-5 hours. After the reaction is completed, the mixture is purified to obtain a bullet-shaped nanomotor with a tail cavity structure.

8. The method for preparing the bullet-shaped nanomotor with a tail cavity structure according to claim 7, characterized in that: The active replacement agent includes any one of H2PdCl4, K2PtCl4, and KMnO4.

9. Use of the bullet-shaped nanomotor with a tail cavity structure as claimed in claim 1 or 2 in catalytic degradation of organic dye pollutants.

10. The use according to claim 9, characterized in that: The organic dye contaminants include methylene blue.

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