CN110468376B

CN110468376B - Carbon-coated silver nanorod array and preparation method and application thereof

Info

Publication number: CN110468376B
Application number: CN201910794516.0A
Authority: CN
Inventors: 文懋; 王美佳; 任萍; 张侃; 郑伟涛; 郑先亮
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2019-08-27
Filing date: 2019-08-27
Publication date: 2020-05-05
Anticipated expiration: 2039-08-27
Also published as: CN110468376A

Abstract

The invention relates to the technical field of functional materials, in particular to a carbon-coated silver nanorod array and a preparation method and application thereof. The preparation method of the carbon-coated silver nanorod array comprises the following steps of: providing a substrate with a metal film on the surface; heating the substrate to remove the moisture, then keeping the temperature of the substrate unchanged, sputtering by taking methane as reaction gas and a silver target as a sputtering target, and obtaining the carbon-coated silver nanorod array on the substrate. The preparation method has the advantages of simple steps, controllable process, low cost, pure product, strong bonding of the carbon-coated nano-rods and the substrate, batch production, and capability of overcoming the defects of impure products, complex operation, difficult structure control and the like of a liquid phase method and a template method, and the like.

Description

Carbon-coated silver nanorod array and preparation method and application thereof

Technical Field

The invention relates to the technical field of functional materials, in particular to a carbon-coated silver nanorod array and a preparation method and application thereof.

Background

The Ag nanorod has large specific surface area, high surface activity, high stability, strong catalytic activity, excellent antibacterial property, good conductivity, unique optical property and the like, and is widely applied to the fields of catalysis, photoelectric materials, energy sources, biomedical treatment and the like. The surface plasmon resonance of Ag enables an area electromagnetic field to be efficiently and rapidly enhanced, the nanorod is large in specific surface area, the length-diameter ratio can be adjusted and controlled, and more adsorption detection molecules are adsorbed, so that the nanorod is frequently used for Surface Enhanced Raman Spectroscopy (SERS) detection. However, the pure silver nanorod structure is easily oxidized or polluted by detection molecules or detection environment in SERS detection, and the surface adsorptivity of some organic molecules to be detected is poor, which is not beneficial to Raman enhancement.

The carbon has low solubility in liquid or solid Ag, is beneficial to in-situ precipitation and coating in the reaction process, has good stability and excellent conductivity, and can effectively protect Ag and improve the binding capacity to organic molecules when being used as a coating layer. If Jiangmeng et al adopts solvothermal reaction, precious metal is reduced by carbon quantum dots, and then the precious metal is coated and grown on the surface of the Jiangmeng et al in situ by taking crystal seeds as cores, so that the precious metal particles are prevented from agglomerating, and the precious metal nanoparticles isolated by the carbon shell layer are prepared and applied to surface-enhanced Raman spectroscopy (CN 105798289B). Therefore, the silver nanorods are coated with carbon, and the stability and the adsorption performance of the silver nanorods are hopeful to be improved.

However, the preparation method of the silver nanorod in the prior art has the problems of complex process, high cost and difficult regulation, for example, the length-diameter ratio of the synthesized Ag rod in the template method is limited by the template, the preparation and removal of the template are complicated, and the cost is high; the liquid phase synthesis method has the problems of complicated operation steps, impure products, disordered nanowire arrangement, poor binding force with a substrate and the like; the vapor phase growth process has more influencing factors, the regulation and control process is complex, and the nano rods are difficult to be arranged in order. There are great difficulties in applying these methods to the preparation of carbon-coated silver nanorod arrays. Therefore, it is highly desirable to develop a method for preparing carbon-coated silver nanorod arrays, which has simple preparation process, low cost, no by-products, and is suitable for mass production.

Disclosure of Invention

The invention aims to provide a carbon-coated silver nanorod array, and a preparation method and application thereof.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a preparation method of a carbon-coated silver nanorod array, which comprises the following steps:

providing a substrate with a metal film on the surface;

heating the substrate to remove the moisture, then keeping the temperature of the substrate unchanged, sputtering by taking methane as reaction gas and a silver target as a sputtering target, and obtaining the carbon-coated silver nanorod array on the substrate.

Preferably, the material of the metal thin film includes Ag or Au.

Preferably, the thickness of the metal film is 10-100 nm.

Preferably, the metal film is prepared by a magnetron sputtering method.

Preferably, the substrate is a silicon wafer or a carbon fiber cloth.

Preferably, the temperature for de-wetting is 400-800 ℃ and the time is 50-70 s.

Preferably, the sputtering gas for sputtering is argon, the working pressure of sputtering is 0.5-1.5 Pa, the temperature of the substrate in the sputtering process is 400-600 ℃, the sputtering power is 10-100W, and the sputtering time is 60-100 min.

Preferably, in the sputtering process, the flow ratio of the sputtering gas to the reaction gas is 1: 0.6-2.7.

The invention also provides a carbon-coated silver nanorod array, which is prepared by the preparation method of the technical scheme.

The invention also provides application of the carbon-coated silver nanorod array in the technical scheme as a SERS substrate.

The invention provides a preparation method of a carbon-coated silver nanorod array, which comprises the following steps: providing a substrate with a metal film on the surface; heating the substrate to de-wet, then maintaining the temperature of the substrate constant,and (3) sputtering by taking methane as reaction gas and a silver target as a sputtering target to obtain the carbon-coated silver nanorod array on the substrate. In the present invention, based on the young's equation: r is_s＝r_i+r_fcosθ(r_sIs the substrate surface energy per unit area, r_iIs the interfacial energy, r, of the substrate per unit area and the metal_fIs the metal surface energy per unit area), the diffusion of metal atoms is limited under the condition of lower energy, which is not beneficial to the occurrence of solid-state dewetting, the heating can increase the system energy, the atomic energy of the metal is enhanced, and the thermodynamic equilibrium state is rapidly reached, so that the dewetting process is effectively excited, the metal is easily gathered on the substrate in the form of nano islands to form metal nano islands, then the sputtering is carried out by taking methane as reaction gas and taking a silver target as a sputtering target, after the mixture of sputtered carbon atoms and silver atoms reaches the substrate, the silver atom migration capability is enhanced under the high-temperature condition, the carbon atoms are preferentially captured by the metal nano islands and grow by taking the metal nano islands as seeds, the carbon atoms are precipitated in situ to cover the outside due to lower solubility, and the limited Ag atoms grow transversely, thereby realizing the controllable preparation of the high-stability Ag nano-rod array, and the obtained carbon-covered silver nano-rods, The distribution is uniform.

The preparation method has the advantages of simple steps, controllable process, low cost, pure product, strong bonding of the carbon-coated nano-rods and the substrate, batch production, and capability of overcoming the defects of impure products, complex operation, difficult structure control and the like in a liquid phase method and a template method, and the like. In addition, the internal Ag nano-rods are effectively protected by carbon coating, so that the stability and the accuracy of the Ag nano-rods are improved, and the service life of the Ag nano-rods is prolonged.

Drawings

FIG. 1 is a schematic diagram of a preparation method according to the present invention;

FIG. 2 SEM image of carbon-coated silver nanorods obtained in example 1;

FIG. 3 TEM image of carbon-coated silver nanorods obtained in example 1;

FIG. 4 SEM image of carbon-coated silver nanorods obtained in example 2;

FIG. 5 SEM image of carbon-coated silver nanorods obtained in example 4;

FIG. 6 SEM image of the product obtained in comparative example 1;

FIG. 7 SEM image of the product obtained in comparative example 2;

FIG. 8 SEM image of the product obtained in comparative example 3;

FIG. 9 is a Raman spectrum of a carbon-coated silver nanorod obtained in examples 1 and 4, a product obtained in comparative examples 1-2, and silicon as an SERS substrate for detecting 4-mercaptobenzoic acid;

FIG. 10 is a Raman spectrum of the product obtained in comparative example 3 and detected 4-mercaptobenzoic acid using silicon as a SERS substrate.

Detailed Description

providing a substrate with a metal film on the surface;

The invention firstly provides a substrate with a metal film on the surface.

In the present invention, the substrate is preferably a silicon wafer or a carbon fiber cloth.

As shown in fig. 1, which is a schematic diagram of the present invention, a substrate with a metal thin film on the surface is heated to perform dewetting (i.e., heat activation, "dewetting"), metal atoms begin to agglomerate and form nano islands (i.e., metal nano islands) through diffusion, a mixture of sputtered carbon atoms and silver atoms reaches the substrate, and Ag atoms preferentially accumulate on the metal nano islands under high temperature conditions, while the carbon atoms diffuse to the outside of the metal islands, so that the carbon atoms are separated from the metal nano islands and promote the directional growth of the nano islands, thereby forming a silver nanorod array with a coating structure.

The invention preferably preprocesses the substrate and then uses the substrate to prepare the metal film; the pretreatment preferably comprises washing and drying; the cleaning comprises acetone washing, ethanol washing and water washing which are sequentially carried out; the acetone washing, the ethanol washing and the water washing are preferably ultrasonic cleaning, and the acetone washing, the ethanol washing and the water washing are preferably carried out for 15-25 min independently; the drying is preferably air-blast drying, the drying temperature is preferably 40-60 ℃, and the drying time is preferably 1-1.5 h.

In the present invention, the material of the metal thin film preferably includes Ag or Au. In the invention, the metal film can form a nano island on the substrate in the de-wetting process, so as to be beneficial to capturing silver atoms subsequently and further form a nano rod seed.

In the present invention, the thickness of the metal thin film is preferably 10 to 100nm, and more preferably 30 to 70 nm. In the present invention, a film of the above thickness facilitates formation of metal nano-islands of appropriate size during dewetting.

In the invention, the metal film is preferably prepared by a magnetron sputtering method; in the preparation process of the metal film: the metal target is parallel to the substrate, the target base distance is preferably 6-10 cm, the sputtering gas is preferably argon, the flow rate of the argon is preferably 60sccm, the working pressure is preferably 0.5-1.5 Pa, and the temperature of the substrate is preferably room temperature, more preferably 10-40 ℃, and most preferably 25 ℃; the sputtering power of the metal target is preferably 10-50W, and the sputtering time is preferably 1-5 min; the specific preparation method of the metal film preferably comprises the following steps: mounting a metal target material and a substrate in a vacuum sputtering cavity of a magnetron sputtering device, adjusting the target base distance, and vacuumizing the cavity to 4.0 multiplied by 10^-4And introducing sputtering gas to working pressure under Pa, setting the sputtering power of the metal target, and sputtering on the substrate.

After the substrate with the metal film on the surface is obtained, the substrate is heated to be dewetted, then methane is used as reaction gas, a silver target is used as a sputtering target, sputtering is carried out, and the carbon-coated silver nanorod array is obtained on the substrate.

After the substrate with the metal film is obtained, the substrate is preferably heated in a vacuum sputtering cavity of a magnetron sputtering device for dewetting. In the invention, in the de-wetting process, the atmosphere in the cavity is preferably maintained as the atmosphere in the preparation of the metal film, and the metal film forms the metal nano island on the substrate. In the invention, the temperature of the de-wetting (i.e. the temperature of the substrate) is preferably 400-800 ℃, more preferably 500-700 ℃, and the time is preferably 50-70 s.

After the dewetting is finished, the temperature of the substrate is kept unchanged, methane is used as reaction gas, and a silver target is used as a sputtering target for sputtering; the specific operation is preferably as follows: and introducing methane gas, and starting a silver target power supply to perform sputtering. In the invention, methane is used as a carbon source, in the sputtering process, the migration capacity of Ag atoms is enhanced after sputtered carbon atoms and silver atoms reach the substrate, the carbon atoms are preferentially captured by the nano-islands and grow by taking the nano-islands as seeds, the carbon atoms are precipitated in situ to be coated outside due to low solubility and the Ag atoms grow transversely in a limited area, and thus, the controllable preparation of the high-stability Ag nanorod array is realized.

In the invention, the sputtering gas for sputtering is preferably argon, the working pressure of sputtering is preferably 0.5-1.5 Pa, more preferably 0.8-1.2 Pa, the temperature of the substrate in the sputtering process is preferably 400-600 ℃, and the sputtering power is preferably 10-100W, more preferably 30-80W; the time for sputtering is preferably 60-100 min, and more preferably 70-80 min. In the invention, the length-diameter ratio of the carbon-coated silver nanorod can be adjusted by regulating the temperature of the substrate and the sputtering power of the silver target in the deposition process, the sputtering power is combined with other parameters to be beneficial to obtaining the nanorod with uniform structure and size, and the nanorod with non-uniform size and more disordered structure can be obtained by overhigh or overlow power.

In the invention, in the sputtering process, the flow ratio of the sputtering gas to the reaction gas is preferably 1: 0.6-2.7, more preferably 1: 1-2.5, and most preferably 1: 1.5-2.0. In the embodiment of the invention, the flow rate of the sputtering gas is preferably 30sccm, and the flow rate of the reaction gas is preferably 20-80 sccm; the total deposition rate of the film is preferably 10-18 nm/min. In the invention, the thickness of the carbon coating layer can be regulated and controlled by regulating and controlling the proportion of the reaction gas, and the higher the proportion of the reaction gas is, the thicker the carbon coating layer is.

After sputtering is finished, the cavity is preferably cooled to room temperature, products are taken out, and the carbon-coated silver nanorod array is obtained on the substrate.

The invention also provides a carbon-coated silver nanorod array, which is prepared by the preparation method in the technical scheme; the diameter of the carbon-coated silver nanorod is preferably 50-250 nm, the length of the carbon-coated silver nanorod is preferably 500-1100 nm, the thickness of the carbon-coated layer is preferably 8-12 nm, and carbon of the carbon-coated layer is amorphous carbon.

The invention also provides application of the carbon-coated silver nanorod array in the technical scheme as a SERS substrate. The carbon-coated silver nanorod array provided by the invention has a good Raman signal enhancement effect and is an excellent SERS substrate.

The carbon-coated silver nanorod array and the preparation method and application thereof provided by the invention are described in detail with reference to the following examples, but the invention should not be construed as being limited by the scope of the invention.

Example 1

1) Taking a silicon wafer as a substrate, and placing the substrate in an acetone solution for ultrasonic cleaning for 20 min; then putting the substrate into ethanol and ultrasonically cleaning for 20 min; finally, ultrasonically cleaning the substrate in deionized water for 20min, taking out the substrate, and drying the substrate in a drying oven at 60 ℃ for 1.5 hours to obtain a clean substrate;

2) putting the cleaned substrate into a vacuum cavity of a magnetron sputtering device, adjusting the deposition angle to be 0 degree, taking an Au target as a metal target, installing the metal target to ensure that the distance between the Au target and the substrate is 10cm, and vacuumizing the cavity to 4 multiplied by 10^-4Pa below;

3) introducing sputtering gas Ar gas, setting the flow rate of the Ar gas to be 60sccm, the working pressure to be 0.8Pa, the substrate temperature to be 25 ℃, the sputtering power to be 50W, sputtering for 5min, and closing the target power supply to obtain an Au film on the substrate; the thickness of the obtained Au film is 60 nm;

4) heating the substrate to 400 ℃ in an argon atmosphere with the pressure of 0.8Pa, preserving the temperature for 60s, keeping the temperature of the substrate unchanged, and introducing CH₄Adjusting the argon flow to 40sccm, CH₄The flow rate was 20sccm and,and (3) starting an Ag target power supply to sputter under the working pressure of 0.8Pa, wherein the temperature of the substrate is 400 ℃ in the sputtering process, the sputtering power is 30W, after sputtering for 55min, closing the Ag target power supply, cooling to room temperature in the cavity, taking out a sample, and obtaining the carbon-coated silver nanorod array on the substrate.

The morphology of the carbon-coated silver nanorod array obtained in the embodiment is characterized, and the results are shown in fig. 2 and 3, wherein fig. 2 is an SEM image, and fig. 3 is a TEM image. As can be seen from fig. 2, the uniformly distributed carbon-coated silver nanorod array is obtained in the present embodiment, the carbon coating layer is amorphous carbon, and the obtained carbon-coated silver nanorod array has a diameter of 100-200 nm and a length of 520-1100 nm; the carbon coating layer thickness of the carbon-coated silver nanorods was measured by fig. 3 to be 10 nm.

Example 2

1) Taking carbon fiber cloth as a substrate, and placing the substrate in an acetone solution for ultrasonic cleaning for 20 min; then putting the substrate into ethanol and ultrasonically cleaning for 20 min; finally, ultrasonically cleaning the substrate in deionized water for 20min, taking out the substrate, and drying the substrate in a drying oven at 60 ℃ for 1.5 hours to obtain a clean substrate;

3) introducing sputtering gas Ar gas, setting the flow rate of the Ar gas to be 60sccm, the working pressure to be 0.8Pa, the substrate temperature to be 25 ℃, the sputtering power to be 40W, sputtering for 5min, closing the target power supply, and obtaining an Au film on the substrate; the thickness of the obtained Au film is 50 nm;

4) heating the substrate to 600 ℃ in an argon atmosphere with the pressure of 0.8Pa, preserving the temperature for 60s, and then introducing CH₄Adjusting the argon flow to 40sccm, CH₄And (3) starting an Ag target power supply to perform sputtering at the sputtering temperature of 500 ℃ and the sputtering power of 40W under the working pressure of 0.8Pa with the flow of 20sccm for 55min, closing the Ag target power supply, cooling to room temperature in the cavity, taking out the sample, and obtaining the carbon-coated silver nanorod array on the substrate.

The morphology of the carbon-coated silver nanorod array obtained in the embodiment is characterized, and the result is shown in fig. 4, wherein (a) is a low-power SEM image, and (b) is a high-power SEM image. As can be seen from FIG. 4, the uniformly distributed carbon-coated silver nanorod array is obtained in the present embodiment, the carbon coating layer is amorphous carbon, and the diameter of the obtained carbon-coated silver nanorod array is 100-250 nm, and the length of the obtained carbon-coated silver nanorod array is 500-1000 nm.

The thickness of the carbon coating layer was measured to be 9nm by TEM test.

Example 3

A carbon-coated silver nanorod array was prepared as in example 2, except that the Au target in step 3) was replaced with an Ag target, the sputtering power of the Ag target in step 4) was 40W, and the thickness of the resulting metal thin film was 40 nm.

According to SEM representation, the carbon-coated silver nanorod array with uniform distribution and size is obtained, the carbon coating layer is amorphous carbon, the diameter of the obtained carbon-coated silver nanorod array is 100-200 nm, and the length of the obtained carbon-coated silver nanorod array is 500-1000 nm.

The carbon coating layer thickness of the carbon-coated silver nanorod is 10 nm.

Example 4

A carbon-coated silver nanorod array was prepared according to the method of example 3, except that the sputtering power in step 4) was 20W.

The morphology of the product obtained in this example was characterized, and the result is shown in fig. 5, in which the diameter of the carbon-coated silver nanorod was 50-100 nm, and the length was 600-1100 nm. This shows that the sputtering power is reduced and the aspect ratio is increased, i.e., the aspect ratio of the carbon-coated silver nanorods can be adjusted by adjusting the sputtering power.

The thickness of the carbon coating layer of the carbon-coated silver nanorods was measured to be 11 nm.

Comparative example 1

A carbon-coated silver nanorod array was prepared as in example 1, except that the operation of heating the substrate in step 4) was omitted and the substrate was maintained at 25c while the Ag target was sputtered.

The morphology of the product obtained in the comparative example is characterized, and the result shows that the surface of the obtained product is a smooth and compact film without the characteristics of the nano-rods, as shown in fig. 6. The reason is that atoms at room temperature have insufficient migration capability after reaching the substrate and cannot combine into clusters to form nano islands, and then Ag cannot be preferentially captured, nucleated and aggregated in the sputtering process, so that a two-dimensional amorphous film is formed.

Comparative example 2

The carbon-coated silver nanorod array was prepared as in example 3, except that, when the metal thin film was prepared in step 3), the sputtering time was 20min, and the thickness of the resulting Ag film was 300 nm.

The morphology of the product obtained in the comparative example is characterized, and the result is shown in fig. 7, the product obtained in the comparative example has extremely thick nano-pillars, the structure is quite uneven, part of the rod-shaped structure collapses, and the diameter and the length of the carbon-coated silver nano-rods are 80-260 nm and 700-1600 nm respectively. The thicker metal film is not beneficial to forming the nano islands with uniform distribution and the subsequent formation of the silver nano rods.

Comparative example 3

A carbon-coated silver nanorod array was prepared according to the method of example 2, except that an argon atmosphere was maintained in step 4), and methane was not introduced.

The morphology of the product obtained in the comparative example is characterized, and the result shows that a thick columnar crystal film is formed, and the nanorod characteristic with high length-diameter ratio is not generated, as shown in fig. 8. The reason is that without adding a carbon source (i.e., a reaction gas), silver atoms cannot grow along nano islands but grow in a layer-island mixed mode, resulting in the formation of a columnar crystalline thin film with a minute gap.

Application example

4-mercaptobenzoic acid is adopted as a probe molecule (Raman signal is positioned at 1078 cm)^-1And 1588cm^-1Etc.) with ethanol as solvent to a concentration of 10^-5A test solution of M; respectively cutting the products obtained in examples 1 and 4 and comparative examples 1-3 into small blocks of 5mm multiplied by 5mm, adding probe molecules into a pure silicon wafer to be used as a comparison test, dripping a solution, and then air-drying to carry out a Raman spectrum test; the excitation wavelength is detected to be 532nm, the detection power is 10.7mW, the laser intensity is 50 percent, and the integration time is 10 s. The results of the tests are shown in FIGS. 9 and 10.

As can be seen from fig. 9 and 10, the carbon-coated silver nanorods obtained in examples 1 and 4 all have significant enhancement effect when used as a SERS substrate for raman spectroscopy test, and the pure silicon sheet has no enhancement effect after being added with probe molecules, and the enhancement effects of comparative examples 1 and 2 are very poor, which indicates that the carbon-coated silver nanorods obtained in comparative example 2 have non-uniform structure and are not significant in enhancement effect compared with the above two; the two-dimensional amorphous film obtained in comparative example 1 cannot enhance Raman signal and is sp-enhanced²And sp³The carbon peak is divided into D peak and G peak (corresponding to 1325cm respectively) by bonding mode^-1And 1595cm^-1) (ii) a Comparative example 3 had no significant enhancement.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a carbon-coated silver nanorod array is characterized by comprising the following steps:

providing a substrate with a metal film on the surface;

heating the substrate to remove the wetting, then keeping the temperature of the substrate unchanged, sputtering by taking methane as reaction gas and a silver target as a sputtering target, and obtaining a carbon-coated silver nanorod array on the substrate;

the material of the metal film comprises Ag or Au; the thickness of the metal film is 10-100 nm;

the temperature for de-wetting is 400-800 ℃, and the time is 50-70 s;

the temperature of the substrate in the sputtering process is 400-600 ℃.

2. The method according to claim 1, wherein the metal thin film is prepared by a magnetron sputtering method.

3. The production method according to claim 1, wherein the substrate is a silicon wafer or a carbon fiber cloth.

4. The method according to claim 1, wherein the sputtering gas is argon, the working pressure of the sputtering is 0.5 to 1.5Pa, the power of the sputtering is 10 to 100W, and the sputtering time is 60 to 100 min.

5. The preparation method according to claim 1 or 4, wherein the flow ratio of the sputtering gas to the reaction gas in the sputtering process is 1: 0.6-2.7.

6. A carbon-coated silver nanorod array prepared by the preparation method of any one of claims 1-5.

7. Use of the carbon-coated silver nanorod array of claim 6 as a SERS substrate.