Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a black gallium oxide nanoparticle with high optical absorption, high carrier separation and strong oxidation reduction and a preparation method thereof, so as to solve the problems of narrow light absorption range, low carrier separation efficiency and the like of a gallium oxide material at present.
In order to achieve the purpose, the invention provides the following technical scheme: a preparation method of black gallium oxide nano-particles comprises the following specific steps:
s1 extracting white Ga2O3Mixing and grinding the nano particles and magnesium powder, and carrying out heat preservation reaction at 500-600 ℃ under a vacuum condition to obtain a third precursor;
s2, immersing the third precursor into water for ultrasonic dispersion, adding excessive dilute hydrochloric acid, stirring for 5-6h, washing the precipitate, and drying to obtain black gallium oxide nanoparticles.
Further, in step S1, the magnesium powder is mixed with white Ga2O3The mole ratio of the nano-particles is 1.3-1.7.
Further, in step S1, the white Ga is mixed by grinding2O3The nano particles and the magnesium powder are put into a quartz tube, and the quartz tube is sealed in vacuum through oxyhydrogen flame.
Further, in step S1, the heat preservation time is 10h-11h, and the temperature rise rate is 1 ℃/min.
Further, in step S2, the third precursor is immersed in deionized water for ultrasonic dispersion for 30 ± 5 min.
Further, in step S2, the concentration of the dilute hydrochloric acid solution is 1mol L-1。
Further, in step S2, the stirring speed is 700r/min-900 r/min.
Further, in step S2, deionized water is used for the washing, and the washing is performed until the supernatant is neutral.
Further, in step S2, the drying is performed at 60 + -5 deg.C for 12 + -1 h.
The invention also provides black gallium oxide nanoparticles prepared by the preparation method.
Compared with the prior art, the invention has at least the following beneficial effects:
the invention provides black gallium oxide nanoparticles and a preparation method thereof, white gallium oxide is annealed in a vacuum reduction environment in which magnesium exists, oxygen ions of gallium oxide crystal lattices are separated, so that oxygen vacancies are formed, the periodicity of the crystal lattices is changed by the existence of the oxygen vacancies, and the electronic properties in a gallium oxide conduction band are changed, including band gap narrowing and band tail state forming, so that a gallium oxide material can absorb light in visible and near infrared regions, and further presents black, the black gallium oxide nanoparticles which can absorb visible light and near infrared light and have strong redox capability are obtained, the problem of narrow light absorption range of gallium oxide is solved, and effective support is provided for expanding the application of gallium oxide in photocatalysis and photoelectric devices.
The invention solves the problem of low carrier separation efficiency of the traditional semiconductor material, obtains the black gallium oxide material with high carrier separation, and provides a new thought and method for the follow-up research of the semiconductor material.
Detailed Description
The invention is further described with reference to the following figures and detailed description.
The invention relates to a preparation method of black gallium oxide nano-particles with high optical absorption, high carrier separation and strong oxidation reduction, which comprises the following steps:
A. preparation of white gallium oxide: 0.526. + -. 0.0005g of gallium nitrate hydrate (Ga (NO)3)3·xH2O) is dissolved in 30 plus or minus 0.5ml of deionized water, and the mixture is placed on a magnetic stirrer to be stirred uniformly, and the stirring speed is controlled at 850 r/min. Several drops of ethylenediamine (NH) were added2CH2CH2NH2) Until the pH value of the solution is about 8. Transferring the mixed solution into a high-pressure kettle with polytetrafluoroethylene as a lining, placing the high-pressure kettle in an oven at the temperature of 120 +/-1 ℃ for 12 +/-0.1 h to complete a hydrothermal reaction, pouring out supernatant after the reaction is completed and the reaction kettle is naturally cooled, repeatedly washing the precipitate with deionized water and ethanol until the pH value of the supernatant is neutral, placing the precipitate in the oven and drying the precipitate at the temperature of 60 +/-5 ℃ for 12 +/-1 h to obtain a first precursor. Grinding the first precursor by using an agate mortar until particles with uniform granularity can be seen by naked eyes, putting the first precursor into an annealing furnace for heat treatment, annealing at 700 ℃ for 2h at the heating rate of 2 ℃/min to obtain white beta-phase Ga2O3And (3) nanoparticles.
B. Preparing black gallium oxide: in a glove box, magnesium powder with the molar ratio of 1.3-1.7 and the white beta-phase Ga prepared in the step A are mixed2O3Grinding and uniformly mixing the nano particles in an agate mortar to obtain a second precursor; the second precursor was charged into a quartz tube, and vacuum-sealed by means of an oxyhydrogen flame. And placing the sealed quartz tube in an annealing furnace, carrying out heat preservation reaction at 500-600 ℃ for 10-11h at the heating rate of 1 ℃/min to obtain a third precursor. After natural cooling, the third precursor is immersed into deionized water for ultrasonic separationDispersing for 30 + -5 min, and adding 1mol L of the mixture-1Dilute hydrochloric acid solution and stir for 5-6h, and the stirring speed is controlled at 700-900 r/min. Washing with deionized water for several times, and drying in a 60 + -5 deg.C oven for 12 + -1 h to obtain black gallium oxide;
white gallium oxide is annealed in a reducing environment in the presence of magnesium, resulting in the dissociation of oxygen ions from the gallium oxide lattice, thereby forming oxygen vacancies. The periodicity of the crystal lattice is changed by the existence of the oxygen vacancy, so that the electronic properties in the conduction band of the gallium oxide are changed, including band gap narrowing and band tail state forming, and the gallium oxide material can absorb light in visible and near infrared regions to further show black.
In the step B:
(1) for safety reasons, the milling and mixing of magnesium powder and gallium oxide must be carried out in a glove box filled with argon and milled uniformly to ensure sufficient contact between the magnesium powder and the gallium oxide.
(2) Magnesium powder was chosen because of its metal reactivity which meets the requirements of the experiment and its relative safety.
(3) In order to completely reduce white gallium oxide to black gallium oxide, an excess of magnesium powder is required.
(4) The oxyhydrogen flame is selected for vacuum sealing in order to ensure that the reaction environment is nearly free of oxygen.
(5) The annealing treatment in the annealing furnace is a necessary condition for generating oxygen vacancies.
(6) The product was ultrasonically dispersed in deionized water to remove salts that may be present while precipitating unreacted magnesium powder.
(7) The excessive dilute hydrochloric acid can not only remove magnesium powder and magnesium oxide, but also can not react with black gallium oxide.
Example 1:
A. preparation of white gallium oxide: 0.526g of gallium nitrate hydrate (Ga (NO)3)3·xH2O) is dissolved in 30ml of deionized water and is placed on a magnetic stirrer to be stirred uniformly, and the stirring speed is controlled at 850 r/min. Several drops of ethylenediamine (NH) were added2CH2CH2NH2) Until the pH of the solution is about 8. Transferring the mixed solution into polytetrafluoroethyleneThe hydrothermal reaction was completed in a lined autoclave and placed in an oven at 120 ℃ for 12 hours. And after the reaction is finished and the reaction kettle is naturally cooled, pouring out supernatant liquid, repeatedly washing the precipitate with deionized water and ethanol, and drying the precipitate in an oven at 60 ℃ for 12 hours to obtain a first precursor. Grinding the first precursor by using an agate mortar until particles with uniform granularity can be seen by naked eyes, putting the first precursor into an annealing furnace for heat treatment, annealing at 700 ℃ for 2h at the heating rate of 2 ℃/min to obtain white beta-phase Ga2O3And (3) nanoparticles. Hydrothermal method and white Ga obtained by post-annealing2O3An irregular nanoparticle structure with pores is shown (as shown in FIG. 1a), and the diameter of the nanoparticle is about 550-620 nm.
B. Preparing black gallium oxide: in a glove box, 0.0385g of magnesium powder and 0.2g of white beta-phase Ga obtained in step A were mixed2O3Grinding and uniformly mixing the nano particles in an agate mortar to obtain a second precursor; the second precursor was charged into a quartz tube and vacuum-sealed by means of an oxyhydrogen flame. And (3) placing the sealed quartz tube in an annealing furnace, and carrying out heat preservation reaction for 10h at 500 ℃ at the heating rate of 1 ℃/min to obtain a third precursor. After natural cooling, the third precursor is immersed into deionized water for ultrasonic dispersion for 30min, and then 4ml of 1mol L of the third precursor is added-1Dilute hydrochloric acid solution and stir for at least 5h, and the stirring speed is controlled at 700 r/min. And washing with deionized water for several times, and drying in an oven at 60 ℃ for 12h to obtain black gallium oxide. Black Ga2O3The irregular nanoparticle structure (as shown in fig. 1b) is still present, and the main morphological features of the surface are changed, and more pores are present.
In order to characterize the crystal quality of gallium oxide nanoparticles, XRD spectroscopy was performed on black gallium oxide samples using a DX-2700 type X-ray diffractometer, and the results are shown in fig. 2. In FIG. 2, significant β -Ga is found2O3The diffraction peak intensity of black gallium oxide is close to that of white gallium oxide, which indicates that the obtained black gallium oxide has high crystal quality.
Using an ultraviolet-visible spectrophotometer model F-7000,characterization of Black Ga2O3The optical absorption properties of the particles, the results are shown in FIG. 3. It is obvious from the figure that white gallium oxide has strong absorption in the far ultraviolet band (200-; however, the prepared black gallium oxide has absorption in the ultraviolet band, and the absorption range of the black gallium oxide extends to the visible light band. The optical band gap of the black gallium oxide is calculated through a corresponding Tauc formula, and compared with the optical band gap of the white gallium oxide of 4.54eV, the optical band gap of the black gallium oxide prepared by the metal reduction method is reduced to 3.81 eV.
A Hitach F-7000 type fluorescence spectrometer is used for researching the migration and recombination processes of photo-generated electron-hole pairs in the semiconductor, and a PL spectrogram of black and white gallium oxide under the excitation of 265nm light is shown in figure 4. It is evident from the figure that the spectral intensity of black gallium oxide is greatly reduced compared to white gallium oxide, which indicates that the separation efficiency of the photo-generated electron-hole pairs of black gallium oxide is very high.
A BRUKER E500-9.5/12 spectrometer was used to characterize the presence of oxygen vacancies in black gallium oxide, and figure 5 is an EPR plot of black, white gallium oxide at room temperature. As is evident from the figure, black gallium oxide has a strong signal peak at g ═ 1.99, while white gallium oxide has no distinct resonance peak, indicating the presence of oxygen vacancies in black gallium oxide.
The photocatalytic redox ability of gallium oxide was tested using a xenon lamp model S350500 and a uv-vis spectrophotometer model TU-1901. FIG. 6 is a graph showing the degradation curves of 50mg black gallium oxide and 50mg white gallium oxide respectively in 50mL of 10mg/L rhodamine b solution through photocatalytic degradation, and it can be seen from the graph that the photocatalytic degradation time of black gallium oxide is shortened from 120min to less than 50min compared with white gallium oxide, and the photodegradation efficiency is greatly improved.
The prepared black gallium oxide is still black after being placed at room temperature for half a year, and the color does not turn white or deteriorate along with time, which shows that the black gallium oxide prepared by the invention has good stability at room temperature;
example 2
Step a is the same as example 1;
and B:
preparing black gallium oxide: in a glove box, 0.0334g of magnesium powder and 0.2g of white beta-phase Ga obtained in step A were mixed2O3Grinding and uniformly mixing the nano particles in an agate mortar to obtain a second precursor; the second precursor was charged into a quartz tube and vacuum-sealed by means of an oxyhydrogen flame. And (3) placing the sealed quartz tube in an annealing furnace, and carrying out heat preservation reaction at 550 ℃ for 11h at the heating rate of 1 ℃/min to obtain a third precursor. After natural cooling, the third precursor is immersed into deionized water for ultrasonic dispersion for 35min, and then 4ml of 1mol L of the third precursor is added-1Dilute hydrochloric acid solution and stir for 5h, and the stirring speed is controlled at 700-900 r/min. Washing with deionized water for several times, and drying in an oven at 55 ℃ for 13h to obtain black gallium oxide.
Example 3
Step a is the same as example 1;
and B:
preparing black gallium oxide: in a glove box, 0.0436g of magnesium powder and 0.2g of white beta-phase Ga from step A were mixed2O3Grinding and uniformly mixing the nano particles in an agate mortar to obtain a second precursor; the second precursor was charged into a quartz tube and vacuum-sealed by means of an oxyhydrogen flame. And (3) placing the sealed quartz tube in an annealing furnace, and carrying out heat preservation reaction for 10h at the temperature of 600 ℃, wherein the heating rate is 1 ℃/min, so as to obtain a third precursor. After natural cooling, the third precursor is immersed into deionized water for ultrasonic dispersion for 25min, and then 4ml of 1mol L of the third precursor is added-1And (5) diluting the hydrochloric acid solution and stirring for 6 hours, wherein the stirring speed is controlled at 800 r/min. Washing with deionized water for several times, and drying in a 65 ℃ oven for 11h to obtain black gallium oxide.
The results prove that the black gallium oxide nanoparticles prepared by the method have the advantages of high optical absorption, high carrier separation, strong redox capability and the like, and provide effective support for expanding the application of gallium oxide in photocatalysis and photoelectric devices. In addition, the invention provides a new idea and method for the subsequent research of semiconductor materials.