阅读说明：本技术 一种调控MXenes薄膜非线性光学性能的方法 (Method for regulating and controlling nonlinear optical performance of MXenes film ) 是由 黄智鹏 李卉 张弛 于 2021-08-24 设计创作，主要内容包括：本发明涉及一种调控MXenes薄膜非线性吸收性能的方法,该方法为：取少层MXenes薄膜,采用电场调控方法对其进行表面端基控制,即实现MXenes薄膜非线性光学性能的调控。与现有技术相比,本发明通过电场调控材料表面端基氧化程度来控制材料激发态能级以及费米能级附近自由电子的态密度,使得材料的能带结构的变化具有高度可控性和可逆性。在不同的激发波长下,MXenes薄膜的非线性吸收性能随表面端基的变化具有多样性,变化高效且可逆。515nm时,表面端基-O基团的增加使得MXenes薄膜具有更大的饱和吸收特性；800nm时,表面端基-OH基团的增加导致材料具有更大的反饱和吸收特性。本发明利用表面端基控制二维材料非线性光学性能,为二维非线性光学材料的发展提供新的思路。(The invention relates to a method for regulating and controlling the nonlinear absorption performance of an MXenes film, which comprises the following steps: and (3) taking a few layers of MXenes films, and controlling the surface end groups of the MXenes films by adopting an electric field regulation and control method, so that the nonlinear optical performance of the MXenes films is regulated and controlled. Compared with the prior art, the invention controls the excited state energy level of the material and the state density of free electrons near the Fermi energy level by regulating the oxidation degree of the terminal group on the surface of the material through the electric field, so that the change of the energy band structure of the material has high controllability and reversibility. Under different excitation wavelengths, the nonlinear absorption performance of the MXenes film has diversity along with the change of surface end groups, and the change is efficient and reversible. At 515nm, the increase of surface end group-O group makes MXenes film have larger saturated absorption characteristic; at 800nm, the increase of the surface terminal group-OH group leads to a material with larger reverse saturable absorption characteristics. The invention utilizes the surface end group to control the nonlinear optical performance of the two-dimensional material, and provides a new idea for the development of the two-dimensional nonlinear optical material.)

1. A method for regulating and controlling the nonlinear optical performance of an MXenes film is characterized in that a conductive substrate loaded with the MXenes film is taken as a working electrode, a three-electrode system is constructed, voltage is applied externally, and electric field regulation and control are carried out, so that the nonlinear optical performance of the MXenes film is regulated and controlled.

2. The method for regulating and controlling the nonlinear optical properties of the MXenes film as claimed in claim 1, wherein the electrolyte used in the three-electrode system is 1M sulfuric acid solution.

3. The method as claimed in claim 1, wherein in the three-electrode system, the counter electrode is a platinum electrode and the reference electrode is a silver electrode.

4. The method as claimed in claim 1, wherein the time of the applied voltage is 20-40 s.

5. The method for regulating the nonlinear optical properties of the MXenes film according to claim 1, wherein the voltage variation range is-0.8V-0.2V.

6. The method as claimed in claim 1, wherein the conductive substrate is quartz glass.

7. The method for regulating and controlling the nonlinear optical property of the MXenes film as claimed in claim 1, wherein the MXenes film supporting conductive substrate is prepared by the following steps:

(1) dissolving lithium fluoride in hydrochloric acid solution, adding Ti₃AlC₂Centrifuging and removing the upper-layer acidic solution until the pH value of the solution is 7, and continuing to centrifuge and retaining the upper-layer solution to obtain a colloidal solution dispersed with MXenes nanosheets;

(2) and (3) placing the conductive substrate in a colloidal solution, preparing the MXenes film by a pulling method, and then drying and annealing to obtain the conductive substrate loaded with the MXenes film.

8. The method as claimed in claim 7, wherein in the step (1), the lithium fluoride, the hydrochloric acid solution and the Ti are mixed₃AlC₂The addition ratio of (A) to (B) is as follows: 1g (15-20) ml of 1g, wherein the concentration of the hydrochloric acid solution is 12M.

9. The method as claimed in claim 7, wherein in step (1), Ti is added₃AlC₂Then, stirring the mixture for 20 to 30 hours at a temperature of between 30 and 40 ℃.

10. The method as claimed in claim 7, wherein the step (2) of preparing the MXenes film by the Czochralski method comprises the following steps: soaking the conductive substrate in MXenes colloidal solution for 3 min at 1-3mm s^-1Constant speed of withdrawal, room temperature airDrying for 5 minutes, and repeating the operation for a plurality of times;

the annealing process conditions specifically comprise: annealing is carried out in a nitrogen atmosphere at 100-300 ℃ for 1-3 hours.

Technical Field

The invention belongs to the technical field of nonlinear optics, and relates to a method for regulating and controlling the nonlinear optical performance of an MXenes film.

Background

Nonlinear optical materials are of great interest for their potential applications in the fields of laser systems, optical confinement, photodetectors, optical communications, data storage, image transmission, and the like. Transition metal carbide (MXenes) is a novel two-dimensional material, and due to the excellent conductivity of the MXenes, the MXenes material has wide application in the fields of transparent conductors, energy storage, photo-thermal conversion, electromagnetic interference and the like. However, the current MXenes materials have the problem of inconsistent nonlinear optical properties, and therefore, the MXenes materials need to be researched.

Meanwhile, most of the two-dimensional third-order nonlinear optical materials, such as graphene, black phosphorus, transition metal sulfide, MXenes, two-dimensional perovskites, and the like, have been used so far. Since the nonlinear optical properties have great correlation with the structure of a two-dimensional material, the material structure is extremely sensitive to the preparation conditions, and it is difficult to control and synthesize a material with desired properties. The unstable nonlinear optical performance of the materials significantly limits the practical application of the materials, so that an effective strategy for developing nonlinear optical materials with stable performance is highly needed to explore a regulation and control means applicable to a wide range of nonlinear optical performance. To date, methods of modulating the response of nonlinear optical materials include: (1) controlling the average size or number of layers of the material; (2) constructing a heterostructure or a nano hybrid to control charge delocalization transfer; (3) and (4) doping atoms. Different methods have different processes, some methods have complex experimental operation, some methods have low controllability and can not realize effective response, and some methods have insignificant effect on performance, thereby being not beneficial to the regulation and control of nonlinear optical performance.

Disclosure of Invention

The invention aims to provide a method for regulating and controlling the nonlinear optical performance of an MXenes film, so as to overcome the technical problems of unstable nonlinear absorption performance, complex experimental operation and the like of the conventional MXenes film. The surface end group is widely existed in the two-dimensional material, has great effect on the photoelectric property of the two-dimensional material, controls the surface end group to control the nonlinear optical property of the material, and is a modulation means which is suitable for wide nonlinear optical materials. The surface end group of the material is controllably and reversibly controlled through electric field regulation, so that the energy band structure and the carrier distribution in the material are changed, the nonlinear optical performance of the MXenes film is controlled, and the MXenes film nonlinear optical material with stable nonlinear absorption performance is obtained.

The purpose of the invention can be realized by the following technical scheme:

a method for regulating and controlling the nonlinear optical performance of an MXenes film comprises the steps of taking a conductive substrate loaded with the MXenes film as a working electrode, constructing a three-electrode system, applying voltage and regulating and controlling an electric field, and thus realizing the regulation and control of the nonlinear optical performance of the MXenes film.

Furthermore, the electrolyte used in the three-electrode system is a 1mol/L sulfuric acid solution.

Furthermore, in the three-electrode system, the counter electrode is a platinum electrode, and the reference electrode is a silver electrode.

Furthermore, the time of the applied voltage is 20-40 s.

Further, the voltage variation range is-0.8V to 0.2V (with respect to the silver electrode), and may be selected to be-0.4V or-0.7V (with respect to the silver electrode).

Further, the conductive substrate is quartz glass.

Further, the preparation process of the conductive substrate loaded with the MXenes film comprises the following steps:

(1) dissolving lithium fluoride in hydrochloric acid solution, adding Ti₃AlC₂Centrifuging and removing the upper-layer acidic solution until the pH value of the solution is 7, and continuing to centrifuge and retaining the upper-layer solution to obtain a colloidal solution dispersed with MXenes nanosheets;

(2) and (3) placing the conductive substrate in a colloidal solution, preparing the MXenes film by a pulling method, and then drying and annealing to obtain the conductive substrate loaded with the MXenes film.

Further, in step (1), lithium fluoride, hydrochloric acid solution and Ti₃AlC₂The addition ratio of (A) to (B) is as follows: 1g (15-20) ml of 1g, wherein the concentration of the hydrochloric acid solution is 12M.

Further, in the step (1), Ti is added₃AlC₂Then, stirring the mixture for 20 to 30 hours at a temperature of between 30 and 40 ℃.

Furthermore, in the step (2), the specific process for preparing the MXenes film by the pulling method comprises the following steps: soaking the conductive substrate in MXenes colloidal solution for 3 min at 1-3mm s^-1Is pulled out at a constant speed and air-dried at room temperature for 5 minutesRepeating the above operations for several times;

further, in the step (2), the annealing process conditions specifically include: annealing is carried out in the nitrogen atmosphere at the temperature of 100-300 ℃ for 1-3 hours so as to improve the bonding force between the MXenes film and the quartz substrate.

The method controls the nonlinear optical performance of the MXenes film by means of regulating the terminal group on the surface of the material through an electric field with high controllability and reversibility, and then controls the excited state energy level of the material and the state Density (DOS) of free electrons near the Fermi energy level by regulating the oxidation degree of the terminal group on the surface of the material through the electric field, so that the change of the energy band structure of the material has high controllability and reversibility. Under different laser wavelengths, the nonlinear absorption performance of the MXenes film has diversity along with the change of surface end groups, and the change is efficient and reversible. Under the excitation of 515nm laser, the increase of surface end group-O group makes MXenes film have larger saturated absorption characteristic; under the excitation of 800nm laser, the increase of the surface terminal group-OH group leads to the material to have larger reverse saturated absorption characteristics. The invention utilizes the surface end group to control the nonlinear optical performance of the two-dimensional material, and provides a new idea for the development of the two-dimensional nonlinear optical material. Meanwhile, the method has the advantages of simple process flow, easy operation, high controllable reversibility, potential mass production and the like, and can be used as an ideal method for controlling the nonlinear performance of the MXenes film.

The electric field range of the invention is determined by repeated experiments according to the redox voltage condition of the MXenes film, the selected voltage range can not only meet the condition that the terminal group on the surface of the material is obviously changed, but also not be too large, the too large voltage range can cause the irreversible oxidation reaction of the material, and simultaneously electrolysis of water can be initiated, and the conditions are not favorable for the experiment and influence the reliability of data.

Compared with the prior art, the invention has the following advantages:

(1) the surface end group of the MXenes material is controlled by an electric field to controllably and reversibly change the energy band structure of the material, and the nonlinear optical performance of the material is controlled, so that the MXenes film nonlinear optical material with stable nonlinear absorption performance is obtained;

(2) the method has the advantages of simple process flow, easy operation and low cost, and is expected to realize industrial production.

Drawings

FIG. 1 is a schematic diagram of the present invention for regulating and testing the nonlinear optical performance of MXenes films;

FIG. 2 shows MXenes film Ti₃C₂(OH)_x、Ti₃C₂O_xAnd Ti₃C₂(OH)_x[H⁺](ii) a raman spectral image of;

FIG. 3 shows MXenes film Ti₃C₂(OH)_x、Ti₃C₂O_xAnd Ti₃C₂(OH)_x[H⁺]Ultraviolet-visible transmission spectrum image of (a);

FIG. 4 is a density of states (DOS) image of MXenes films with different surface end groups;

FIG. 5 is T for the products obtained in examples 1 to 4, comparative examples 1 and 2_NL-z-pattern and nonlinear absorption coefficient summary.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

In the following examples, unless otherwise specified, all the conventional commercially available raw materials or conventional processing techniques in the art are indicated.

In the following examples, titanium carbide MXenes films were synthesized in small layers by the micro dense layering (mld) method. Generally, lithium fluoride (1.0g) was dissolved in hydrochloric acid solution (18mL,12M), and Ti was added₃AlC₂(1.0g), and stirred at 35 ℃ for 24 hours. Centrifuging the obtained solution at 3500rpm for 5 minutes, removing the upper layer acid solution, repeating the above operations until the pH value of the solution is 7, wherein the upper layer solution in the centrifugal tube is black green, centrifuging at 3500rpm for 30 minutes, and retaining the black upper layer solution to obtain the colloidal solution dispersed with MXenes nanosheets. By a pulling methodMXenes films were deposited on quartz substrates. The quartz substrate was immersed in MXenes colloidal solution for 3 minutes at 2mm s^-1The tube was pulled out at a constant speed, air-dried at room temperature for 5 minutes, and the soaking was repeated 5 times. The film on the back of the substrate was washed with ethanol and dried under vacuum. In order to improve the bonding force between the MXenes film and the quartz substrate, annealing is carried out for 2 hours at 200 ℃ in a nitrogen atmosphere to obtain the loaded MXenes film Ti₃C₂(OH)_xThe quartz substrate of (1). Electrochemical ion insertion employs CHI760E electrochemical workstation (shanghai chenhua instruments ltd) which employs an i-t Curve procedure to perform the electrochemical redox process.

Example 1:

synthesis of titanium carbide MXenes film Ti by MILD method₃C₂(OH)_x. As shown in FIG. 1, for MXenes film Ti₃C₂(OH)_xPerforming surface end group control: the method comprises the steps of taking a quartz substrate loaded with an MXenes film as a working electrode, sealing 1M sulfuric acid electrolyte between the working electrode and bare quartz, inserting a platinum wire and a silver wire into the electrolyte, respectively taking the platinum wire and the silver wire as a counter electrode and a reference electrode, reacting for 30s under the voltage of 0.2V to realize the oxidation process from-OH groups to-O groups, and obtaining the MXenes film Ti₃C₂O_x. It was then tested for nonlinear response at a wavelength of 515nm at a single beam nonlinear transmission setting.

MXenes film Ti evaluation by single beam nonlinear Transmission in open Aperture Z-Scan System (Z-scan)₃C₂O_xThe result of the nonlinear response shows that the nonlinear absorption changes from reverse saturated absorption to saturated absorption, and the value beta of the nonlinear absorption is_eff＝-1020cm/GW。

Example 2:

synthesis of titanium carbide MXenes film Ti by MILD method₃C₂(OH)_x. By loading MXenes film Ti₃C₂(OH)_xThe quartz substrate of (1M) was used as a working electrode, and a sulfuric acid electrolyte was sealed between the working electrode and bare quartz. Inserting a platinum wire and a silver wire into the electrolyte, respectively serving as a counter electrode and a reference electrode, reacting for 30s under the voltage of-0.8V to realize the reduction from-O group to-OH groupObtaining MXenes film Ti by the original process₃C₂(OH)_x[H⁺]. The non-linear response test is carried out on the single-beam non-linear transmittance setting under the wavelength of 800 nm.

MXenes film Ti evaluation by single beam nonlinear Transmission in open Aperture Z-Scan System (Z-scan)₃C₂(OH)_x[H⁺]The result of the nonlinear response shows that the nonlinear absorption is reverse saturable absorption, and compared with MXenes film without surface end group control (the test result is shown in comparative example 2), the nonlinear absorption is enhanced, and the value beta is_eff＝113cm/GW。

Comparative example 1:

synthesis of titanium carbide MXenes film Ti by MILD method₃C₂(OH)_x. Directly without surface end group control, under 515nm wavelength and single beam nonlinear transmissivity setting, MXenes film Ti₃C₂(OH)_xA non-linear response test is performed.

MXenes film Ti evaluation by single beam nonlinear Transmission in open Aperture Z-Scan System (Z-scan)₃C₂(OH)_xThe nonlinear response result shows that the nonlinear absorption is reverse saturated absorption, and the value is as follows: beta is a_eff＝153cm/GW。

Comparative example 2:

synthesis of titanium carbide MXenes film Ti by MILD method₃C₂(OH)_x. Directly without surface end group control, under 800nm wavelength and single beam nonlinear transmissivity setting, MXenes film Ti₃C₂(OH)_xA non-linear response test is performed.

MXenes film Ti evaluation by single beam nonlinear Transmission in open Aperture Z-Scan System (Z-scan)₃C₂(OH)_xThe nonlinear response result shows that the nonlinear absorption is reverse saturated absorption, and the value is as follows: beta is a_eff＝67cm/GW。

As shown in FIG. 2, 621cm in the in situ Raman spectrum^-1Is Ti₃C₂(OH)_xCharacteristic peak of (1), 621cm when a positive voltage is applied to the sample^-1The peak is shifted to 593cm^-1And 593cm^-1Is Ti₃C₂O_xWhile applying a negative voltage to the sample, 593cm^-1The peak returns to 621cm^-1Peak(s). It discloses MXenes thin films of Ti₃C₂(OH)_xA change in surface end groups during an electrochemical process, the surface end groups converting from-OH groups to-O groups when a positive voltage is applied, the surface end groups converting from-O groups to-OH groups when a negative voltage is applied.

The linear transmission spectra in fig. 3 show that MXenes films with different surface end groups have different optical absorption properties.

The different surface end groups MXenes films of figure 4 show different defect level state Densities (DOS) in the bandgap.

T of FIG. 5_NLThe z-pattern indicates that MXenes films with different surface end groups, the increased oxidation of the surface end groups under 515nm laser excitation gives MXenes films with greater saturable absorption characteristics than untreated MXenes films; under the excitation of 800nm laser, the reduction of the oxidation degree of the surface end group leads to the material to have larger reverse saturation absorption characteristic. c-d is MXenes film Ti₃C₂(OH)_x、Ti₃C₂O_xAnd Ti₃C₂(OH)_x[H⁺]Summary of nonlinear absorption coefficients.

Example 3:

most of them were the same as in example 1 except that in this example, the voltage was adjusted to-0.8V.

Example 4:

most of them were the same as in example 2 except that in this example, the voltage was adjusted to 0.2V.

Example 5:

most of them were the same as in example 1 except that in this example, the voltage was adjusted to 0.1V.

Example 6:

most of them were the same as in example 1 except that in this example, the voltage was adjusted to-0.2V.

Example 7:

most of them were the same as in example 1 except that in this example, the voltage was adjusted to-0.5V.

Example 8:

most of them were the same as in example 2 except that in this example, the voltage was adjusted to 0.1V.

Example 9:

most of them were the same as in example 2 except that in this example, the voltage was adjusted to-0.2V.

Example 10:

most of them were the same as in example 2 except that in this example, the voltage was adjusted to-0.5V.

Example 11:

most of the same as in example 1, except that in this example, the reaction time was changed to 20 s.

Example 12:

most of them were the same as in example 1 except that in this example, the reaction time was changed to 40 s.

Example 13:

compared to example 1, most of them were the same except that in this example, the hydrochloric acid solution (18mL,12M) was changed to hydrochloric acid solution (15mL, 12M).

Example 14:

compared to example 1, most of them were the same except that in this example, the hydrochloric acid solution (18mL,12M) was changed to hydrochloric acid solution (20mL, 12M).

Example 15:

compared with example 1, most of them are the same except that in this example, stirring at 35 ℃ for 24 hours is changed to stirring at 30 ℃ for 20 hours.

Example 16:

compared with example 1, most of them are the same except that in this example, stirring at 35 ℃ for 24 hours is changed to stirring at 40 ℃ for 30 hours.

Example 17:

most of them were the same as in example 1 except that in this example, the annealing was carried out at 200 ℃ for 2 hours in a nitrogen atmosphere, and the annealing was carried out at 100 ℃ for 1 hour in a nitrogen atmosphere.

Example 18:

most of them were the same as in example 1 except that in this example, the annealing was carried out at 200 ℃ for 2 hours in a nitrogen atmosphere, and the annealing was carried out at 300 ℃ for 3 hours in a nitrogen atmosphere.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.