Preparation and application of NiO nanoparticle-coated AlGaN nanowire photoelectrode with core-shell structure

Abstract

The invention discloses preparation and application of a NiO nano-particle-coated AlGaN nanowire photoelectrode with a core-shell structure, and the preparation comprises the step of modifying NiO nano-particles on an AlGaN nanowire by using a dipping and calcining method so as to form the structure. On one hand, NiO and AlGaN form a II-type heterojunction, carrier separation can be promoted, and the separation efficiency of photon-generated carriers is effectively improved; and on the other hand, the penetration depths of NiO and AlGaN to light with different wavelengths are different, so that objects for generating dominant photon-generated carriers under different wavelengths are different, and the electrode can generate light currents with opposite polarities under illumination of different wavelengths.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectric detection, and specifically relates to the preparation and application of a NiO nanoparticle@AlGaN nanowire photoelectrode with a core-shell structure. Background Art

[0002] Photoelectric detection is a device that can convert light signals into electrical signals. It is widely used in optical communications, imaging, sensing and measurement. Ultraviolet light is a type of light in the electromagnetic spectrum, with a wavelength range of approximately 10 nanometers to 400 nanometers. Ultraviolet detectors are devices used to detect this light. In addition, ultraviolet photoelectric detectors are widely used in space detection, ozone monitoring, biomedical research, etc.

[0003] Solid-state photoconductive detectors have long response times, high energy consumption, and require external power supplies, which seriously hinders the practical application of UV detectors. In recent years, a new type of PEC UVPDs has emerged. Its working principle not only follows the typical carrier generation, separation, and migration process in traditional solid-state photodetectors, but also involves a unique electrochemical process, namely, the carrier diffusion process and the redox reaction at the semiconductor / water electrolyte interface. PEC UV PDs have attracted widespread attention and research from researchers because of their advantages such as low power consumption, simple preparation process, low cost, high sensitivity, fast response speed, and self-power supply. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

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

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

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a NiO nanoparticle@AlGaN nanowire photoelectrode with a core-shell structure, characterized in that: the NiO nanoparticle@AlGaN nanowire photoelectrode is a core-shell structure, wherein the AlGaN nanowire is the core and the outer layer is coated with NiO nanoparticles.

[0008] Another object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a NiO nanoparticle@AlGaN nanowire photoelectrode.

[0009] As a preferred embodiment of the preparation method of the present invention, the AlGaN nanowire sample is placed in a precursor solution A, taken out after heating, placed in a drying oven, and dried under a nitrogen atmosphere, and the immersed and dried sample is placed in a tubular furnace for calcination.

[0010] As a preferred embodiment of the preparation method of the present invention, the precursor solution A is a NiCl2·6H2O aqueous solution.

[0011] As a preferred embodiment of the preparation method of the present invention, the concentration of the precursor solution A is 0.2M.

[0012] As a preferred embodiment of the preparation method of the present invention, the heating temperature is 30-35°C and the heating time is 35-40 minutes.

[0013] As a preferred embodiment of the preparation method of the present invention, the drying temperature is 80-85°C.

[0014] As a preferred embodiment of the preparation method of the present invention, the calcination temperature is 420-450° C. and the calcination time is about 180-190 min.

[0015] As a preferred solution of the preparation method of the present invention, the AlGaN nanowire sample is obtained by growing n-type AlGaN NWs on a Si substrate using plasma-assisted molecular beam epitaxy technology.

[0016] Another object of the present invention is to overcome the deficiencies in the prior art and provide a NiO nanoparticle@AlGaN nanowire photoelectrode with a core-shell structure for use in PEC light detection.

[0017] Beneficial effects of the present invention:

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

[0019] (2) NiO and AlGaN in the photoelectrode of the present invention have different penetration depths for light of different wavelengths, and thus different objects produce dominant photogenerated carriers at different wavelengths. Since NiO is P-type and AlGaN is N-type, they can generate photocurrents of opposite polarity under ultraviolet light of different wavelengths, and thus ultraviolet light of different spectra can be distinguished according to the polarity of the photocurrent. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0021] Figure 1 This is a flow chart for preparing the photoelectrode and a test performance diagram according to Example 1 of the present invention.

[0022] Figure 2 TEM line scan spectrum of the photoelectrode obtained in Example 1 of the present invention; wherein Figure 2 a is a transmission electron microscope image of NiO@AlGaN nanowires (a row of slanted AlGaN nanowires). Figure 2 b is the energy spectrum diffraction pattern of a single AlGaN nanowire scanned by 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 DESCRIPTION

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0025] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present 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 term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0027] Unless otherwise specified, all raw materials used in the examples of the present invention are commercially available, as shown in Table 1 for details.

[0028] Table 1

[0029] name Commercial channels Part Number Nickel chloride hexahydrate Maclean N814831-100g Nickel nitrate hexahydrate Aladdin N140967-100g

[0030] Example 1

[0031] (1) Prepare 0.2 M NiCl2·6H2O aqueous solution: Mix 2.376 g NiCl2·6H2O powder and 50 mL deionized water, and stir under a magnetic stirrer for 30 min at a speed of 180 r to allow the mixture to fully blend.

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

[0033] Growth of n-AlGaN nanowires: n-type AlGaN NWs were grown on Si(100) substrates using plasma-assisted molecular beam epitaxy (PAMBE). Before loading the silicon wafer into the MBE chamber, the oxide on the surface of the silicon wafer was removed with an HF solution. After cleaning, the silicon wafer was vented in a load lock chamber at 200°C for 1 hour and then vented in a buffer chamber at 650°C to remove any water components and organic contaminants. During the growth of the nanowires, in order to reduce the desorption of gallium atoms and increase the nucleation probability, the silicon-doped GaN seeds were first nucleated on the silicon wafer at ≈500°C for 1 min. The flow rate of the nitrogen plasma source was 1.0 standard cubic centimeters per minute (sccm), the RF power was 300W, the metal source was provided by a standard Knudsen cell, and the beam equivalent pressure (BEP) value was (Ga)6.0×10 -8 Torr. The k-cell temperature of silicon dopant is 1180℃. After the growth of n-GaN nucleation layer less than 3nm, the temperature is increased to 630℃, and the Al and GaN BEPs are 5×10 -8 and 9×10 -8 The n-AlGaN layer was grown for 2 h at 2000 MHz and 4000 MHz under 0.17 V / min conditions, while the Si substrate temperature was maintained at 1180 °C under the same nitrogen plasma conditions. During the growth of the Si(111) substrate, the residual oxide was cleaned and removed before heating. The thermal infiltration cell provided controlled fluxes of Al, Ga, Si and Mg, and the RF plasma source added nitrogen.

[0034] (3) Impregnation: The prepared AlGaN nanowire sample is placed in a prepared 0.2M NiCl2·6H2O aqueous solution, and taken out after heating. The impregnation concentration is 0.2M, the impregnation temperature is about 30-35°C, and the heating time is about 35-40min.

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

[0036] (5) Calcination: The dried sample is placed in a tube furnace for calcination at a temperature of 420-450°C for about 180-190 min. Finally, a core-shell structure of AlGaN nanowires coated with NiO nanoparticles is obtained.

[0037] Figure 1 Schematic diagram of the core-shell structure of 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 by Ni(NO)3·6H2O.

[0050] Comparative Example 7

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

[0052] Comparative Example 8

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

[0054] Comparative Example 9

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

[0056] Example 2

[0057] This study used the CHI760E electrochemical workstation produced by Shanghai Chenhua Instrument Co., Ltd., and used a three-electrode configuration for photoelectrochemical (PEC) performance testing. The specific test steps are as follows: sodium sulfate is used as the electrolyte, wherein the working electrode is the sample to be tested, the reference electrode is a silver / silver chloride electrode, and the counter electrode is a platinum mesh electrode. In order to simulate actual lighting conditions, we selected LED lamp beads with wavelengths of 255nm and 365nm as light sources. The shutter can be used to quickly turn on and off light irradiation without turning off the light source, thereby accurately controlling the illumination time. The examples 1 and comparative examples 1-10 were recorded at 0V bias voltage, 1mW cm -2 Photocurrent density under illumination (J ph ), and the photoresponsivity (R) is calculated. The results are shown in Table 2.

[0058] Table 2

[0059]

[0060]

[0061] Note: “-” indicates that the photoelectrode preparation failed and no relevant data is available.

[0062] As can be seen from Table 2, adjusting the concentration of the nickel chloride solution has a significant effect on the response rate of the photoelectrode under different wavelengths of ultraviolet light. First, NiO is a p-type semiconductor, which can generate negative photocurrent when it absorbs light, and AlGaN is an n-type semiconductor, which can generate positive photocurrent when it absorbs light. AlGaN has the strongest absorption at 255nm, but basically no absorption at 365nm. In comparison, NiO has the strongest absorption at 365nm, but basically no absorption at 255nm.

[0063] Modifying NiO nanoparticles on AlGaN nanowires will lead to improved photoresponse at 255nm. Reason: AlGaN plays a major role at 255nm. AlGaN and NiO form a type II heterojunction, which promotes the efficiency of photogenerated carrier separation.

[0064] The more NiO nanoparticles modified on the AlGaN nanowires, the higher the photoresponse at 365nm. Reason: NiO plays a major role at 365nm, and the more NiO nanoparticles there are, the higher the photoresponse at 365nm will be, corresponding to the increase in the concentration of the immersion precursor solution.

[0065] However, it is inevitable that the photoresponse at 255nm will decrease as the number of NiO nanoparticles increases. There are two reasons: on the one hand, the nanoparticles are too thick to block the light from irradiating AlGaN; on the other hand, NiO can also absorb 255nm ultraviolet light, and because NiO is a p-type semiconductor, the flow direction of carriers in the body under light is just opposite to that of n-type AlGaN, which will reduce the photoresponse rate to a certain extent. In addition, since AlGaN does not absorb 365nm ultraviolet light, but NiO can, the photoresponse at 365nm will increase with the increase of the concentration of the immersion solution.

[0066] It can also be seen from Table 2 that changing the calcination temperature will result in no light response under 365 nm ultraviolet light, which may be because calcining the impregnated sample at 350 °C is not enough to form NiO. Figure 3 The present invention uses a method combining impregnation and calcination to form a core-shell structure of NiO nanoparticles covering AlGaN nanowires.

[0067] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the present invention.

Claims

1. A NiO nanoparticle@AlGaN nanowire photoelectrode with a core-shell structure, characterized in that: The NiO nanoparticle@AlGaN nanowire photoelectrode is a core-shell structure, wherein the AlGaN nanowire is the core and the outer layer is coated with NiO nanoparticles.

2. The method for preparing the NiO nanoparticle@AlGaN nanowire photoelectrode according to claim 1, characterized in that: The method comprises placing an AlGaN nanowire sample in a precursor solution A, taking it out after heating, placing it in a drying oven, drying it in a nitrogen atmosphere, and placing the immersed and dried sample in a tube furnace for calcination.

3. The preparation method according to claim 2, characterized in that: The precursor solution A is a NiCl2·6H2O aqueous solution.

4. The preparation method according to claim 3, characterized in that: The concentration of the precursor solution A is 0.2M.

5. The preparation method according to claim 2, characterized in that: The heating temperature is 30-35°C and the heating time is 35-40 minutes.

6. The preparation method according to claim 2, characterized in that: The drying temperature is 80-85°C.

7. The preparation method according to claim 2, characterized in that: The calcination temperature is 420-450° C., and the calcination time is about 180-190 minutes.

8. The preparation method according to claim 2, characterized in that: The AlGaN nanowire sample is obtained by growing n-type AlGaN NWs on a Si substrate using a plasma-assisted molecular beam epitaxy technique.

9. Application of the NiO nanoparticle@AlGaN nanowire photoelectrode with core-shell structure as claimed in claim 1 in PEC light detection.

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