CN108375687B

CN108375687B - Method for coating graphene on probe tip of atomic force microscope

Info

Publication number: CN108375687B
Application number: CN201810195166.1A
Authority: CN
Inventors: 段慧玲; 李学全; 邵丽华; 张凯
Original assignee: Beijing Institute Of Collaborative Innovation
Current assignee: Beijing Institute Of Collaborative Innovation
Priority date: 2018-03-09
Filing date: 2018-03-09
Publication date: 2020-12-04
Anticipated expiration: 2038-03-09
Also published as: CN108375687A

Abstract

The invention relates to a method for coating graphene on a probe tip of an atomic force microscope, which comprises the following steps: and (3) immersing an atomic force microscope probe in a polylysine aqueous solution, taking out, immersing in a graphene solution, taking out, and drying. According to the invention, the interaction of polycation of polylysine and anion on graphene is utilized, so that the acting force between the atomic force microscope probe tip and graphene is increased, the yield of the graphene-coated atomic force microscope probe tip prepared by an immersion method is greatly improved, and the yield can reach more than 90%; the method provided by the invention has the advantages of easily available raw materials, simple operation and strong practical and popularization values.

Description

Method for coating graphene on probe tip of atomic force microscope

Technical Field

The invention relates to the field of atomic force microscope preparation, in particular to a method for coating graphene on a probe tip of an atomic force microscope.

Background

An Atomic Force Microscope (AFM) is an analytical instrument that can be used to study the surface structure of solid materials including insulators. The basic principle of the atomic force microscope is as follows: one end of a micro-cantilever which is sensitive to weak force is fixed, the other end of the micro-cantilever is provided with a micro-needle point, the micro-needle point is lightly contacted with the surface of a sample, and because the weak repulsive force exists between atoms at the tip end of the micro-needle point and atoms on the surface of the sample, the micro-cantilever with the micro-needle point moves up and down in the direction vertical to the surface of the sample corresponding to an equipotential surface of the acting force between the micro-needle point and the atoms on the surface of the sample by controlling the constancy of the force during scanning. The position change of the micro-cantilever corresponding to each scanning point can be measured by an optical detection method or a tunnel current detection method, so that the information of the surface topography of the sample can be obtained.

AFM probes are basically prepared by processing Si or Si3N4 by MEMS technology, and the radius of the probe tip is generally 10 to tens of nm. The microcantilever is typically made from a silicon wafer or silicon nitride wafer that is typically 100-500 μm long and about 500 nm-5 μm thick. A typical silicon micro-cantilever is about 100 μm long, 10 μm wide, and several microns thick. Microscopes have been developed for different applications using different interaction forces between the probe and the sample, such as AFM (van der waals force), electrostatic force microscope EFM (electrostatic force) magnetic force microscope MFM (electrostatic force) lateral force microscope LFM (probe lateral deflection force), etc., and thus have corresponding probes for different kinds of microscopes. Specifically, the probes of the atomic force microscope mainly include the following probes: (1) non-contact/tap mode tip and contact mode probe: the most commonly used products have high resolution and general service life. The probe is continuously worn in the using process, and the resolution ratio is easily reduced. The method is mainly applied to surface topography observation. (2) A conductive probe: the probe is obtained by plating 10-50 nm thick Pt (and other metals for improving the bonding force of the plating layer, such as Cr, Ti, Pt, Ir and the like) on a common probe. The conductive probe is applied to EFM, KFM, SCM and the like. The resolution of the conductive probe is inferior to that of the probes in tapping and contact modes, and the conductive plating layer is easy to fall off during use, so that the conductivity is difficult to maintain for a long time. The new products of the conductive needle point are carbon nano tube needle point, diamond coating needle point, full diamond needle point and full metal wire needle point, and these new technologies overcome the short service life and low resolution of the common conductive needle point. (3) Magnetic probe: the conductive coating is applied to MFM, prepared by plating ferromagnetic layers such as Co, Fe and the like on probes in common tapping and contact modes, has poorer resolution than common probes, and is easy to fall off when in use. (4) Large length-diameter ratio probe: the large aspect ratio tips are designed and produced for measuring deep trenches and near plumb sides. The method is characterized in that: the product is not very common, the resolution ratio is very high, and the service life is general. The technical parameters are as follows: the needle tip height is more than 9 mu m; the length-diameter ratio is 5: 1; the radius of the needle tip is less than 10 nm. (5) Diamond-like carbon AFM probe/full diamond probe: one is to add a diamond-like carbon film on the tip of the silicon probe, and the other is made of all-diamond material (which is very expensive). The two diamond carbon probes have great durability, and the abrasion of the needle tip is reduced, so that the service life is prolonged.

There are many methods for coating graphene on the tip of an atomic force microscope, and the most common method is to directly immerse the tip of the AFM into a graphene solution, take out and dry the tip. For example: patent document CN104360107A discloses a graphene-coated atomic force microscope probe and a preparation method thereof; the graphene-coated atomic force microscope probe comprises a probe substrate, a cantilever and a probe tip, wherein metal layers are arranged on the cantilever and the probe tip, and a graphene layer is also arranged on the probe tip; the preparation method of the probe comprises the following steps: (1) preparing a graphene solution: adding 5-10mg of graphene into 1mL of water, and ultrasonically dispersing in an ultrasonic cleaning instrument for 10min to prepare a graphene solution with the concentration of 5-10 mg/mL; (2) preparing a graphene-coated atomic force microscope probe: and (3) immersing the cantilever and the needle point of the atomic force microscope probe with the metal layer on the needle point into the graphene solution in the step (1), mechanically stirring for 30-60s, taking out and naturally drying.

However, since the force acting between the atomic force microscope tip and the graphene, that is, the van der waals force, is weak, there may be a case where the tip is not coated with the graphene in the dipping method, resulting in a low coating yield.

Disclosure of Invention

The invention aims to provide a method for coating graphene on a probe tip of an atomic force microscope, aiming at the problem that the yield of the existing liquid phase transfer method technology for coating the probe tip of the atomic force microscope is low. The method can improve the coating rate and yield of the graphene coated atomic force microscope needle tip.

Specifically, the method for coating graphene on the probe tip of the atomic force microscope provided by the invention comprises the following steps: and (3) immersing the atomic force microscope probe in a polylysine aqueous solution, taking out the probe without drying, directly immersing the probe in a graphene solution, taking out the probe and drying the probe to obtain the graphene oxide film.

The method provided by the invention has wide application range and has no special requirements on the material of the cargo-time substrate of the atomic force microscope probe.

In the present invention, the concentration of the polylysine aqueous solution is preferably 0.001mg/ml to 0.6mg/ml, more preferably 0.001mg/ml to 0.005 mg/ml. The time for immersing in the polylysine aqueous solution is preferably 10 to 60 seconds, and more preferably 25 to 35 seconds.

According to the invention, after the atomic force microscope probe is immersed in the polylysine aqueous solution with the specific concentration, the surface of the material can be fully modified, so that the acting force between the tip of the atomic force microscope probe and graphene is improved.

The graphene used in the present invention is not particularly limited, and the number of layers is preferably 1 to 5, and most preferably a single layer. The solvent of the graphene solution may be an organic solvent in which graphene can be dispersed, such as water, ethanol, propanol, N-methylpyrrolidone, or dimethylformamide, and an aqueous solvent is preferably used in the present invention.

Further preferably, the concentration of the graphene solution is 0.1mg/ml to 2mg/ml, and more preferably 0.8mg/ml to 1.2 mg/ml. According to the invention, a great deal of practice shows that if the concentration of the graphene is too high, the graphene coated on the AFM needle point is multi-layer, the curvature radius of the needle point is correspondingly increased, and the resolution of the needle point coated by the graphene is reduced. The time for immersing in the graphene solution is preferably 10 s-60 s, and more preferably 25-35 s.

The blow-drying is preferably performed by using nitrogen.

The invention also protects the graphene-coated atomic force microscope probe prepared by the method.

The invention further protects the application of the graphene-coated atomic force microscope probe in the preparation of an atomic force microscope.

According to the invention, the interaction of polycation of polylysine and anion on graphene is utilized, so that the acting force between the atomic force microscope probe tip and graphene is increased, the yield of the graphene-coated atomic force microscope probe tip prepared by an impregnation method is greatly improved, and the yield can reach more than 90%, preferably more than 95%; the method provided by the invention has the advantages of easily available raw materials, simple operation and strong practical and popularization values.

Drawings

FIG. 1 is a schematic illustration of the process described in example 1; in FIG. 1 (a): 1 is an atomic force microscope probe, 2 is a polylysine aqueous solution, and 4 is a culture dish or beaker containing the polylysine aqueous solution; in FIG. 1 (b): 3 is graphene solution, and 5 is a culture dish or beaker filled with the graphene solution.

Detailed Description

The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

The atomic force microscope probes used in the following examples were purchased from manufacturers: nanosors, type: PPP-CONTPt, product batch number: Lot.No. 07/201.

Polylysine used in the following examples was purchased from the manufacturer: beijing SolarbioScience and Technology co.ltd, lot.no. 20170920;

graphene used in the following examples was purchased from manufacturers: first feng nano, goods number: 100052.

example 1

The embodiment provides a method for coating graphene on a probe tip of an atomic force microscope, and a schematic diagram of the method is shown in fig. 1; the method specifically comprises the following steps:

(1) modification of polylysine: taking 10mL of polylysine aqueous solution 2 with the concentration of 0.001mg/mL into a culture dish 4, immersing an atomic force microscope probe into the polylysine aqueous solution 2 for 30 seconds, and taking out;

(2) dipping in a graphene solution: and (3) putting 10mL of graphene water solution 3 with the concentration of 1mg/mL into a culture dish 5, immersing the atomic force microscope probe treated in the step (1) in the culture dish for 30 seconds, taking out, and drying by nitrogen to obtain the graphene probe.

Example 2

This example provides a method for coating graphene on a probe tip of an atomic force microscope, which is different from example 1 only in that: the concentration of the polylysine aqueous solution is 0.01 mg/ml.

Example 3

This example provides a method for coating graphene on a probe tip of an atomic force microscope, which is different from example 1 only in that: the concentration of the polylysine aqueous solution is 0.5mg/ml, and the concentration of the graphene solution is 2 mg/ml.

Comparative example

Referring to the method provided in example 1 of patent document CN104360107A, the method of coating graphene on the tip of the atomic force microscope probe same as the above examples includes:

(1) preparing a graphene solution: adding 5mg of graphene into 1mL of water, and ultrasonically dispersing in an ultrasonic cleaning instrument for 10min to prepare a graphene solution with the concentration of 5 mg/mL;

(2) preparing a graphene-coated atomic force microscope probe: and (2) immersing the needle tip of the atomic force microscope probe into the graphene solution in the step (1), mechanically stirring for 60s, taking out and naturally drying.

Through detection, the graphene coating rate and the graphene thickness of the obtained product, which can be realized by the methods of the above examples and comparative examples, are shown in table 1.

Table 1: result of graphene coating

	Graphene coating ratio (%)	Graphene thickness (nm)
			Example 1	95％	0.44
Example 2	93％	1
			Example 3	95％	1
Comparative example	85％	0.34

As can be seen from the results in Table 1, the scheme provided by the application can obviously improve the coating rate of the graphene on the probe tip of the atomic force microscope, is simple to operate and has extremely high popularization value.

Although the invention has been described in detail hereinabove by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that many modifications and improvements can be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims

1. A method for coating graphene on a probe tip of an atomic force microscope is characterized by comprising the following steps: immersing an atomic force microscope probe in a polylysine aqueous solution, taking out, immersing in a graphene solution, taking out, and drying;

wherein the concentration of the polylysine aqueous solution is 0.001mg/ml to 0.005mg/ml, and the concentration of the graphene solution is 0.8mg/ml to 1.2 mg/ml.

2. The method according to claim 1, wherein the time for immersion in the aqueous solution of polylysine is 10 to 60 seconds.

3. The method according to claim 2, wherein the immersion time in the aqueous solution of polylysine is 25 to 35 seconds.

4. The method according to any one of claims 1 to 3, wherein the number of graphene layers is 1 to 5.

5. The method of claim 4, wherein the number of graphene layers is 1.

6. The method according to claim 4, wherein the solvent of the graphene solution is water, ethanol, propanol, N-methylpyrrolidone, or dimethylformamide.

7. The method according to claim 6, wherein the solvent of the graphene solution is water.

8. The method according to claim 4, wherein the time for immersion in the graphene solution is 10s to 60 s.

9. The method according to claim 6, wherein the time for immersion in the graphene solution is 10s to 60 s.

10. The method according to claim 8, wherein the time for immersion in the graphene solution is 25-35 s.

11. The method according to claim 9, wherein the time for immersion in the graphene solution is 25-35 s.

12. The graphene-coated atomic force microscope probe prepared by the method of any one of claims 1 to 11.

13. Use of the graphene coated atomic force microscope probe of claim 12 for preparing an atomic force microscope.