Preparation and application of NiO nanoparticles@AlGaN nanowire photoelectrode with core-shell structure

Abstract

The application discloses a preparation and application of a NiO nanoparticle@AlGaN nanowire photoelectrode with a core-shell structure, and comprises the following steps: NiO nanoparticles are modified on AlGaN nanowires by using a dipping and calcining method to form the structure. On one hand, NiO and AlGaN form a type II heterojunction, which can promote carrier separation and effectively improve the separation efficiency of photo-generated carriers; on the other hand, the penetration depths of NiO and AlGaN for different wavelengths of light are different, so that the objects of dominant photo-generated carriers are different under different wavelengths of light, and thus the electrode can generate photoelectric currents with opposite polarities under different wavelengths of light.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology, specifically relating to the preparation and application of a NiO nanoparticle@AlGaN nanowire photoelectrode with a core-shell structure. Background Technology

[0002] Photodetectors are devices that convert optical signals into electrical signals, and they are widely used in optical communication, imaging, sensing, and measurement. Ultraviolet light is a type of light in the electromagnetic spectrum with wavelengths ranging from approximately 10 nanometers to 400 nanometers; ultraviolet detectors are devices used to detect this light. Furthermore, ultraviolet photodetectors have wide applications in space exploration, ozone monitoring, and biomedical research.

[0003] Solid-state photoconductive detectors (SPDs) suffer from long response times and high energy consumption, requiring external power supplies, which severely hinders their practical application in ultraviolet (UV) detectors. In recent years, a new type of PEC UVPD has emerged. Its working principle not only follows the typical carrier generation, separation, and migration processes in traditional solid-state photodetectors but also involves a unique electrochemical process: carrier diffusion and redox reactions at the semiconductor / electrolyte interface. PEC UVPDs have attracted widespread attention and research due to their advantages such as low power consumption, simple fabrication process, low cost, high sensitivity, fast response speed, and self-powered operation. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a NiO nanoparticle@AlGaN nanowire photoelectrode with a core-shell structure.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a NiO nanoparticle@AlGaN nanowire photoelectrode with a core-shell structure, characterized in that: the NiO nanoparticle@AlGaN nanowire photoelectrode has a core-shell structure, wherein AlGaN nanowires are used as the core and NiO nanoparticles are coated on the outer layer.

[0008] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing NiO nanoparticles@AlGaN nanowire photoelectrodes.

[0009] As a preferred embodiment of the preparation method described in this invention, the AlGaN nanowire sample is placed in precursor solution A, heated and then removed, placed in a drying oven, dried under a nitrogen atmosphere, and then calcined in a tube furnace.

[0010] In a preferred embodiment of the preparation method described in this invention, the precursor solution A is an aqueous solution of NiCl2·6H2O.

[0011] In a preferred embodiment of the preparation method described in this invention, the concentration of the precursor solution A is 0.2 M.

[0012] In a preferred embodiment of the preparation method described in this invention, the heating temperature is 30-35℃ and the heating time is 35-40 min.

[0013] In a preferred embodiment of the preparation method described in this invention, the drying temperature is 80-85℃.

[0014] In a preferred embodiment of the preparation method described in this invention, the calcination temperature is 420-450℃ and the calcination time is approximately 180-190 min.

[0015] In a preferred embodiment of the preparation method described in this invention, the AlGaN nanowire sample is obtained by growing n-type AlGaN NWs on a Si substrate using plasma-assisted molecular beam epitaxy.

[0016] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of a core-shell structured NiO nanoparticle@AlGaN nanowire photoelectrode in PEC photodetector.

[0017] Beneficial effects of this invention:

[0018] (1) The NiO nanoparticles of the present invention encapsulate the AlGaN nanowire photoelectrode and successfully form a type II heterojunction, which can promote the movement of photogenerated holes in AlGaN to NiO and the movement of photogenerated electrons in NiO to AlGaN, thereby improving the separation efficiency of photogenerated carriers and enhancing the detector performance.

[0019] (2) The NiO and AlGaN in the photoelectrode of this invention have different penetration depths for light of different wavelengths, and therefore the objects that generate dominant photogenerated carriers are different at different wavelengths. Since NiO is P-type and AlGaN is N-type, photocurrents with opposite polarities can be generated under ultraviolet light of different wavelengths, and ultraviolet light of different spectra can be distinguished according to the polarity of the photocurrent. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0021] Figure 1 The flowchart and test performance diagram of the photoelectrode prepared in Embodiment 1 of the present invention are shown.

[0022] Figure 2 The TEM line scan energy spectrum of the photoelectrode prepared in Example 1 of this invention; wherein Figure 2 Image a is a transmission electron microscope image of NiO@AlGaN nanowires (a row of diagonally arranged AlGaN nanowires). Figure 2 b is the energy spectrum diffraction pattern of a single AlGaN nanowire obtained by line scanning of the white line segment.

[0023] Figure 3 This is a TEM core-shell structure diagram of the photoelectrode prepared in Example 1 of the present invention. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0027] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available. See Table 1 for details.

[0028] Table 1

[0029] Nickel chloride, hexahydrate McLean N814831-100g Nickel nitrate hexahydrate Aladdin N140967-100g

[0030] Example 1

[0031] (1) Prepare 0.2M NiCl2·6H2O aqueous solution: Mix 2.376g NiCl2·6H2O powder with 50mL deionized water and stir for 30min with a magnetic stirrer at a speed of 180r to ensure full mixing.

[0032] (2) MBE growth of gallium nitride nanowires: p-AlGaN / n-GaN nanowire arrays were prepared on a planar Si(111) substrate by plasma-assisted MBE.

[0033] Growth of n-AlGaN nanowires: n-type AlGaN nanowires were grown on Si(100) substrates using plasma-assisted molecular beam epitaxy (PAMBE). Before loading the silicon wafer into the MBE chamber, oxides on the silicon wafer surface were removed with an HF solution. After cleaning, the silicon wafer was degassed in a load-locked chamber at 200°C for 1 hour, and then degassed in a buffer chamber at 650°C to remove any water components and organic contaminants. During nanowire growth, to reduce gallium atom desorption and increase the nucleation probability, silicon-doped GaN seeds were first nucleated on the silicon wafer at approximately 500°C for 1 minute. The nitrogen plasma source had a flow rate of 1.0 standard cubic centimeters per minute (sccm), an RF power of 300 W, and a metal source provided by a standard Knudsen cell with a beam equivalent pressure (BEP) of 6.0 × 10⁻⁶ (Ga). -8 Torr. The k-cell temperature for silicon dopant is 1180℃. After growing an n-GaN nucleation layer smaller than 3 nm, the temperature was increased to 630℃, with Al and GaN BEPs of 5 × 10⁻⁶. -8 and 9×10 -8 Under Torr conditions, the n-AlGaN layer was grown for 2 hours while the Si substrate temperature was maintained at 1180 °C, and the nitrogen plasma conditions were the same. During the growth of the Si(111) substrate, it was heated after cleaning and removal of residual oxides. A thermal infiltration pool provided controllable fluxes of Al, Ga, Si, and Mg, and nitrogen was added by an RF plasma source.

[0034] (3) Impregnation: The prepared AlGaN nanowire sample was placed in a 0.2M NiCl2·6H2O aqueous solution, heated and then removed. The impregnation concentration was 0.2M, the impregnation temperature was about 30-35℃, and the heating time was about 35-40min.

[0035] (4) Drying: Take out the impregnated sample and put it into a drying oven. Dry it in a nitrogen atmosphere at a temperature of 80-85℃.

[0036] (5) Calcination: The dried sample was placed in a tube furnace for calcination at a temperature of 420-450℃ for a time of approximately 180-190 min. The final result was a core-shell structure of NiO nanoparticles coated with AlGaN nanowires.

[0037] Figure 1 A schematic diagram of the core-shell structure obtained by the original AlGaN nanowire array and the AlGaN nanowire array coated with NiO nanoparticles.

[0038] Comparative Example 1

[0039] The difference from Example 1 is that the concentration of the impregnation solution in step (3) is 0.05M.

[0040] Comparative Example 2

[0041] The difference from Example 1 is that the concentration of the impregnation solution in step (3) is 0.1M.

[0042] Comparative Example 3

[0043] The difference from Example 1 is that the concentration of the impregnation solution in step (3) is 0.15M.

[0044] Comparative Example 4

[0045] The difference from Example 1 is that the calcination temperature in step (5) is 250°C.

[0046] Comparative Example 5

[0047] The difference from Example 1 is that the calcination temperature in step (5) is 350°C.

[0048] Comparative Example 6

[0049] The difference from Example 1 is that in step (1), NiCl2·6H2O is replaced with Ni(NO)3·6H2O.

[0050] Comparative Example 7

[0051] The difference from Example 1 is that in step (2), AlGaN nanowires are replaced with GaN nanowires.

[0052] Comparative Example 8

[0053] The difference from Example 1 is that NiCl2·6H2O from step (1) is not added.

[0054] Comparative Example 9

[0055] The difference from Example 1 is that the AlGaN nanowires of step (2) are not added.

[0056] Example 2

[0057] This study used a CHI760E electrochemical workstation manufactured by Shanghai Chenhua Instrument Co., Ltd., and employed a three-electrode configuration for photoelectrochemical (PEC) performance testing. The specific testing steps are as follows: sodium sulfate was used as the electrolyte, with the working electrode being the sample under test, the reference electrode being a silver / silver chloride electrode, and the counter electrode being a platinum mesh electrode. To simulate actual illumination conditions, LED beads with wavelengths of 255 nm and 365 nm were selected as the light source. A shutter mechanism was used to rapidly turn the light irradiance on and off without turning off the light source, thus precisely controlling the illumination time. The performance of Examples 1 and Comparative Examples 1-10 was recorded at a bias voltage of 0 V and a wavelength of 1 mW cm⁻¹. -2 Photocurrent density under illumination (J) ph The photoresponse rate (R) was calculated, and the results are shown in Table 2.

[0058] Table 2

[0059]

[0060]

[0061] Note: "-" indicates that the photoelectrode fabrication failed and no relevant data is available.

[0062] Table 2 shows that adjusting the concentration of the nickel chloride impregnation solution significantly affects the responsivity of the photoelectrode under different wavelengths of ultraviolet light. Firstly, NiO is a p-type semiconductor, which generates a negative photocurrent under its absorbable light, while AlGaN is an n-type semiconductor, generating a positive photocurrent under its absorbable light. AlGaN exhibits the strongest absorption at 255 nm but almost no absorption at 365 nm. In contrast, NiO shows the strongest absorption at 365 nm but almost no absorption at 255 nm.

[0063] Modifying AlGaN nanowires with NiO nanoparticles leads to improved photoresponse at 255 nm. The reason is that AlGaN plays a major role at 255 nm; AlGaN and NiO form a type II heterojunction, which promotes the efficiency of photogenerated carrier separation.

[0064] The greater the number of NiO nanoparticles modified on AlGaN nanowires, the higher the photoresponse at 365 nm. Reason: NiO is the dominant component at 365 nm; a higher number of NiO nanoparticles naturally leads to a higher photoresponse at 365 nm, corresponding to an increased concentration of the impregnating precursor solution.

[0065] However, it's inevitable that an increase in the number of NiO nanoparticles will lead to a decrease in photoresponse at 255nm. There are two reasons for this: firstly, the nanoparticles are too thick and block light from reaching AlGaN; secondly, NiO can also absorb 255nm ultraviolet light, and because NiO is a p-type semiconductor, the direction of charge carrier flow under illumination is exactly opposite to that of n-type AlGaN, thus reducing the photoresponse rate to some extent. Furthermore, since AlGaN does not absorb 365nm ultraviolet light, while NiO can, the photoresponse at 365nm increases with increasing impregnation solution concentration.

[0066] Table 2 also shows that changing the calcination temperature will result in no photoresponse under 365nm ultraviolet light. This may be because calcining the impregnated sample at 350℃ is insufficient to form NiO. Figure 3 This invention utilizes a combination of impregnation and calcination to form a core-shell structure of NiO nanoparticles coated with AlGaN nanowires.

[0067] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing a NiO nanoparticle@AlGaN nanowire photoelectrode with a core-shell structure, characterized in that: include, Prepare a 0.2M NiCl2·6H2O aqueous solution: Mix 2.376g of NiCl2·6H2O powder with 50mL of deionized water and stir with a magnetic stirrer for 30min at a speed of 180r to ensure complete mixing; MBE growth of gallium nitride nanowires: n-AlGaN / n-GaN nanowire arrays were fabricated on a planar Si substrate by plasma-assisted MBE. Before loading the silicon wafer into the MBE chamber, oxides on the silicon wafer surface were removed with an HF solution. After cleaning, the silicon wafer was degassed in a load-locked chamber at 200°C for 1 hour, and then degassed in a buffer chamber at 650°C to remove any water and organic contaminants. During nanowire growth, to reduce gallium atom desorption and increase the nucleation probability, silicon-doped GaN seeds were first nucleated on the silicon wafer at approximately 500°C for 1 minute. The nitrogen plasma source had a flow rate of 1.0 standard cubic centimeters per minute and an RF power of 300 W. The Ga metal source was provided by a standard Knudsen cell, and the beam equivalent pressure was 6.0 × 10⁻⁶. −8 Torr; the k-cell temperature for silicon dopant is 1180℃; after growing an n-GaN nucleation layer smaller than 3nm, the temperature is increased to 630℃, with Al and Ga BEPs of 5×10⁻⁶ respectively. −8 and 9×10 −8 Under Torr conditions, the n-AlGaN layer was grown for 2 hours while the Si substrate temperature was maintained at 1180℃, the flow rate of the nitrogen plasma source was 1.0 standard cubic centimeters / minute, and the RF power was 300W. The prepared AlGaN nanowire samples were placed in a 0.2M NiCl2·6H2O aqueous solution, heated, and then removed. The impregnation concentration was 0.2M, the impregnation temperature was 30-35℃, and the heating time was 35-40min. Take out the impregnated sample and place it in a drying oven to dry it under a nitrogen atmosphere at a temperature of 80-85℃. The dried sample was placed in a tube furnace and calcined at a temperature of 420-450℃ for 180-190 min; finally, a core-shell structure of NiO nanoparticles coated with AlGaN nanowires was obtained.

Images