CN111139525A - Zirconium dioxide crystal and preparation method thereof - Google Patents
Zirconium dioxide crystal and preparation method thereof Download PDFInfo
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- CN111139525A CN111139525A CN202010010382.1A CN202010010382A CN111139525A CN 111139525 A CN111139525 A CN 111139525A CN 202010010382 A CN202010010382 A CN 202010010382A CN 111139525 A CN111139525 A CN 111139525A
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- 239000013078 crystal Substances 0.000 title claims abstract description 79
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 title claims abstract description 48
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 title claims abstract description 40
- 238000002360 preparation method Methods 0.000 title claims abstract description 9
- 238000000034 method Methods 0.000 claims abstract description 9
- 239000000463 material Substances 0.000 claims abstract description 7
- 239000011941 photocatalyst Substances 0.000 claims abstract description 7
- 239000000725 suspension Substances 0.000 claims description 18
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical group OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 16
- 238000000137 annealing Methods 0.000 claims description 13
- 239000007800 oxidant agent Substances 0.000 claims description 8
- 229910006213 ZrOCl2 Inorganic materials 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 5
- 238000006243 chemical reaction Methods 0.000 claims description 4
- 230000001590 oxidative effect Effects 0.000 claims description 4
- 230000001681 protective effect Effects 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims description 3
- 239000002245 particle Substances 0.000 abstract description 12
- 238000001027 hydrothermal synthesis Methods 0.000 abstract description 8
- 238000000862 absorption spectrum Methods 0.000 abstract description 7
- 230000005284 excitation Effects 0.000 abstract description 5
- RBTBFTRPCNLSDE-UHFFFAOYSA-N 3,7-bis(dimethylamino)phenothiazin-5-ium Chemical compound C1=CC(N(C)C)=CC2=[S+]C3=CC(N(C)C)=CC=C3N=C21 RBTBFTRPCNLSDE-UHFFFAOYSA-N 0.000 description 19
- 229960000907 methylthioninium chloride Drugs 0.000 description 19
- 239000000243 solution Substances 0.000 description 18
- 230000007547 defect Effects 0.000 description 11
- 230000001699 photocatalysis Effects 0.000 description 9
- 239000003054 catalyst Substances 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 238000010521 absorption reaction Methods 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 239000012153 distilled water Substances 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 238000001782 photodegradation Methods 0.000 description 6
- 239000002105 nanoparticle Substances 0.000 description 5
- 238000005424 photoluminescence Methods 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 4
- 230000015556 catabolic process Effects 0.000 description 4
- 125000004122 cyclic group Chemical group 0.000 description 4
- 238000006731 degradation reaction Methods 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 238000000103 photoluminescence spectrum Methods 0.000 description 4
- 239000002063 nanoring Substances 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 238000002336 sorption--desorption measurement Methods 0.000 description 3
- 238000003917 TEM image Methods 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 239000002086 nanomaterial Substances 0.000 description 2
- 238000013033 photocatalytic degradation reaction Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 238000009281 ultraviolet germicidal irradiation Methods 0.000 description 2
- IPCAPQRVQMIMAN-UHFFFAOYSA-L zirconyl chloride Chemical compound Cl[Zr](Cl)=O IPCAPQRVQMIMAN-UHFFFAOYSA-L 0.000 description 2
- 229910017488 Cu K Inorganic materials 0.000 description 1
- 229910017541 Cu-K Inorganic materials 0.000 description 1
- 238000001016 Ostwald ripening Methods 0.000 description 1
- 229910006251 ZrOCl2.8H2O Inorganic materials 0.000 description 1
- 229910007746 Zr—O Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000000295 emission spectrum Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000013032 photocatalytic reaction Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000008707 rearrangement Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000004627 transmission electron microscopy Methods 0.000 description 1
- 238000000870 ultraviolet spectroscopy Methods 0.000 description 1
- 238000002371 ultraviolet--visible spectrum Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
- 229910052724 xenon Inorganic materials 0.000 description 1
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/16—Oxides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
- B01J21/066—Zirconium or hafnium; Oxides or hydroxides thereof
-
- B01J35/39—
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/67—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing refractory metals
- C09K11/671—Chalcogenides
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
- C30B33/02—Heat treatment
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B7/00—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions
- C30B7/10—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions by application of pressure, e.g. hydrothermal processes
Abstract
The embodiment of the invention discloses a zirconium dioxide crystal and a preparation method thereof, wherein the zirconium dioxide crystal is annular and is a monoclinic system. The zirconium dioxide crystal of the present invention shows a wide absorption spectrum in the visible light region and a low band gap of 3.7eV, and also shows a blue light emitting property under excitation of light having a wavelength of 200nm to 400nm, and thus, it can be used as a photoluminescent material and a photocatalyst. The crystal is prepared by a hydrothermal synthesis method in one step, the crystal can be spontaneously crystallized, grown and cured by the hydrothermal reaction, and the obtained crystal has high purity, uniform appearance, narrow particle size distribution and high crystallinity.
Description
Technical Field
The invention relates to the field of functional nano materials, in particular to a zirconium dioxide crystal and a preparation method thereof.
Background
Zirconium dioxide (ZrO)2) There are three differentCrystal structure of m-ZrO respectively2: monoclinic system (< 1170 ℃), t-ZrO2: tetragonal system (1170-2370 ℃) and c-ZrO2: cubic system (greater than 2370 ℃). Zirconium dioxide is a wide band gap ceramic oxide material that has been extensively studied as a Diluted Magnetic Semiconductor (DMS) material and catalyst.
ZrO2Is largely dependent on its microscopic appearance, crystalline phase, grain size and lattice defect type.
Disclosure of Invention
The invention aims to provide a cyclic zirconium dioxide crystal and a preparation method thereof, and the cyclic zirconium dioxide crystal has excellent performance in fluorescence and photocatalytic activity as proved by experiments.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the zirconium dioxide crystal is annular and is monoclinic.
Preferably, the zirconium dioxide crystal has an outer diameter of 4nm to 50 nm.
A preparation method of zirconium dioxide crystals comprises the following steps:
adding an oxidant into the ZrOCl2 solution, and fully reacting to obtain a first suspension;
under a closed condition, heating the first suspension at 130-300 ℃, and after full reaction, obtaining a second suspension containing intermediate crystals;
separating the intermediate crystals from the second suspension; and
and annealing the intermediate crystal to obtain the zirconium dioxide crystal, wherein the zirconium dioxide crystal is annular and is a monoclinic system.
Preferably, the oxidizing agent is hydrogen peroxide.
Preferably, the concentration of the ZrOCl2 solution is 0.1M-1M.
Preferably, the pressure of the first suspension in a closed environment is 20MPa to 60MPa, and the reaction time is 10h to 72 h.
Preferably, the annealing is performed under a protective atmosphere.
Preferably, the annealing temperature is 500-1200 ℃, and the time is 1-10 h.
The invention also discloses the application of the zirconium dioxide crystal in a photoluminescence material or a photocatalyst.
The embodiment of the invention has the following beneficial effects:
the zirconium dioxide crystal with a ring structure is synthesized by a hydrothermal synthesis method in one step, the ring structure enables a large number of lattice defects to be generated in the zirconium dioxide crystal, and the lattice defects enable the zirconium dioxide crystal to have a lower energy band, a higher specific surface area and oxygen vacancies, so that outstanding advantages are shown in the aspects of fluorescence and photocatalytic activity. The hydrothermal synthesis method can enable the crystal to spontaneously crystallize, grow and mature, and the obtained crystal has high purity, uniform appearance, narrow particle size distribution and high crystallinity.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without any creative effort.
Wherein:
FIG. 1a is an XRD pattern at room temperature of ZH crystals and ZH7 crystals obtained in example 1.
FIG. 1b is a TEM image of ZH crystals prepared in example 1.
FIG. 1c is a TEM image of ZH7 crystals prepared in example 1.
FIG. 1d is a schematic diagram of the growth of ZH7 crystal prepared in example 1.
FIG. 2a is an adsorption/desorption isotherm plot of ZH7 prepared in example 1.
FIG. 2b is a photograph of ZH crystals and ZH7 crystals (ahv) obtained in example 12The curve of vs. hv is shown,the inset is the absorption spectra of the ZH crystal and the ZH7 crystal.
FIG. 2c is a PL spectrum of ZH crystals and ZH7 crystals obtained in example 1.
FIG. 2d is a PL spectrum of a further excited ZH7 crystal with different wavelengths of 380 and 400 nm.
Fig. 3a is an absorption spectrum recorded at different time intervals for a MB dye solution mixed with ZH 7.
Fig. 3b is a plot of standard residual concentration of MB dye versus photodegradation time for MB dye solutions mixed with ZH7 and pure MB dye solutions.
FIG. 3c is a graph of the photodegradation rate of ZH7 crystals as a photocatalyst in cyclic operation.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention discloses a zirconium dioxide crystal which is annular and is a monoclinic system. The annular structure enables zirconium dioxide crystals to generate crystal defects, and experiments prove that the crystal defects enable the zirconium dioxide to show excellent performances in the aspects of photocatalytic activity and photoluminescence.
Preferably, the zirconium dioxide crystals have an outer diameter of 4nm to 50 nm. The smaller the volume, the larger the specific surface area, and the more significant the quantum effect due to the defect. The specific surface area of the annular structure is larger than that of spherical particles with the same volume, and the middle hollow part of the annular structure also provides an adsorption space for adsorption and larger adsorption surface area, so that the photocatalytic degradation has a remarkable effect.
The preparation method of the zirconium dioxide crystal comprises the following steps:
s10 in ZrOCl2Adding oxidant into the solution to fully reactAfter that, a first suspension was obtained. Preferably ZrOCl2The concentration of the solution is 0.1M-1M.
Specifically, ZrOCl is used2·8H2O is taken as a raw material, ZrOCl is added2·8H2Dissolving O in distilled water to form ZrOCl2And (3) solution.
Preferably, the oxidant is hydrogen peroxide, and the hydrogen peroxide can be added into distilled water to prepare hydrogen peroxide, and then the hydrogen peroxide and ZrOCl are added2The obtained ZrO is fully reacted to obtain the ZrO-containing mixed solution2A precipitated first suspension. Since the oxidizing agent of hydrogen peroxide does not contain impurity ions capable of participating in crystal crystallization, the suspension obtained as described above can be directly subjected to hydrothermal reaction. Of course, ZrOCl can also be oxidized with other oxidizing agents2·8H2Oxidation of O to ZrO2ZrO with higher purity can be obtained by separation and purification processes2。
And S20, heating the first suspension obtained in the step S10 in a closed environment at the temperature of 130-300 ℃, and fully reacting to obtain a second suspension containing intermediate crystals.
The hydrothermal reaction can make the crystal spontaneously crystallize, grow and mature, and the obtained crystal has high purity, uniform appearance, narrow particle size distribution and high crystallinity. Preferably, the pressure of the first suspension in a closed environment is 20MPa to 60MPa, and the reaction time is 10h to 72 h.
S30, separating intermediate crystals from the second suspension obtained in S20.
Specifically, the precipitate of the intermediate crystal can be collected by a centrifuge, then washed with distilled water and ethanol for multiple times to remove impurities, and then dried at 60-100 ℃ for 10-72 hours to obtain the dried intermediate crystal.
And S40, annealing the intermediate crystal obtained in the S30 to obtain a zirconium dioxide crystal.
Preferably, the annealing is carried out in a protective atmosphere, which can increase the oxygen vacancies in the final crystal obtained, improving the photocatalytic properties. Preferably, the annealing temperature is 500-1200 ℃ and the time is 1-10 h.
The test proves that: the final zirconium dioxide crystal obtained by the invention is an annular monoclinic crystal, and shows a wide absorption spectrum and a low band gap of 3.7eV in a visible light region (400-800 nm). Further, since it exhibits blue light emission even when excited by light having a wavelength of 200nm to 400nm, it is useful as a photoluminescent material. In addition, the zirconium dioxide crystal finally obtained by the invention has lower energy band, higher specific surface area and oxygen vacancy, and shows excellent photocatalytic performance under ultraviolet irradiation, so the zirconium dioxide crystal can also be used as a photocatalyst.
Provided is a concrete embodiment.
Example 1
6.445g of ZrOCl2.8H2O was dissolved in 40mL of distilled water, while 24mL of hydrogen peroxide was prepared and dissolved in 40mL of distilled water. Thereafter, the two solutions were mixed, and the final solution was stirred for 15 minutes. The mixed solution was then transferred to a 100 ml teflon-lined stainless steel autoclave and maintained at 140 ℃ for 24 hours in an electronic oven. Thereafter, the autoclave was allowed to cool naturally to room temperature. Then, the sample was collected at 5000 rpm for 1 hour by a centrifuge, and washed with distilled water and ethanol several times to remove impurities. Finally, the sample was dried at 80 ℃ for 18h, at which time an intermediate crystal, designated ZH, was obtained. The prepared sample was further annealed at 700 ℃ for 4h to give the final crystal, designated ZH 7.
The crystal properties of the ZH and ZH7 samples obtained in example 1 were analyzed by x-ray diffractometer (Bruker-AXS-D8) and Cu-K α radiation (λ ═ 1.54 angstroms.) the size and shape of the ZH7 sample was investigated by transmission electron microscopy (HITACHI-H-8100). The absorption spectra of the sample in the range of 200-800nm were recorded by Perkin Elmer Lambda 35 UV-Vis spectrophotometer, the magnetic properties of the sample were characterized by a fluorescence spectrometer (Spex-Fluorology 3, FL3-22) using a 450w xenon lamp as excitation source and an excitation wavelength of 300nm, the Photoluminescence (PL) emission spectra of the synthesized sample were recorded, the magnetic properties of the sample were characterized by a vibrating sample magnetometer (MicroSenseEV 7). finally, n2 adsorption/desorption isotherms were plotted and the BET (Brunauer, Emmett and Teller) specific surface areas were calculated.
To investigate the crystalline phases of ZH and ZH7,XRD measurements were performed at room temperature and the diffractogram is shown in figure 1 a. The x-ray diffraction pattern of ZH7 shows clear monoclinic phase peaks (matching JCPDS card number 88-2390) at 2 theta ≈ 17.4 °, 24.4 °, 28.1 °, 31.4 °, 34.4 °, 35.2 °, 38.6 °, 40.7 °, 44.8 °, 50.1 °, 54.0 °, 55.3 °, 57.8 °, 60.0 °, 65.6 °, 71.2 ° and 75.1 °. As can be seen from fig. 1a, when ZH7 was held at an elevated temperature of 700 ℃, the sample ZH showed a pure monoclinic phase. Zr in ZH74+Is 7, the strong covalent bond of Zr-O tends to be 7 times the coordination number, which is why ZH7 is thermodynamically stable at low temperatures. Furthermore, the sharp peaks and high intensity peaks in ZH7 compared to ZH indicate that the synthesized samples had a large increase in crystallinity after annealing. According to the Scherrer equation, the average grain sizes of ZH and ZH7 were 4.1nm and 9.8nm, respectively.
The morphology of samples ZH and ZH7 was studied by TEM measurements as shown in fig. 1b and 1c, respectively. In sample ZH, very small nanoparticles can be seen in the different beams. However, in sample ZH7, spherical nanoparticles can be found, which indicates that after heat treatment, the small bundle nanoparticles grow into spherical nanoparticles. From FIG. 1c, it can also be seen that in sample ZH7, the nanoparticles contain small pores, making them a ring structure. This cyclic morphology can provide additional surface area, thereby improving the performance of the sample as a photocatalyst. The outer diameter of the ring structure ranged from 4nm to 50nm, and the average particle size of sample ZH7 was 23.1 nm.
As shown in FIG. 1d, the zirconium dioxide crystal prepared by the present invention is a particle with smaller particle size before hydrothermal reaction, during the hydrothermal reaction, the particle with smaller particle size starts to aggregate, nucleate and grow, the annealing heat treatment process makes the crystal continue Ostwald ripening, i.e. the smaller particle dissolves and the larger particle grows up, so the average size of the particle increases, the crystallinity of the crystal becomes higher, and the atom rearrangement in the crystal is more regular.
Calculation of m-ZrO Using BET (Brunauer, Emmett and Teller) analysis2Surface area of nanoring, FIG. 2a shows m-ZrO2N of nanoring2Adsorption/desorption isotherms. Expected m-ZrO2The nanoring has a diameter of 83.4m2In terms of/gHigh surface area, whereas the surface area of ZH is 43.7m2/g。
The UV-VIS absorption spectra recorded for the ZH and ZH7 samples in the 200-800nm range are shown in the inset of FIG. 2 b. In the ultraviolet band, a strong absorption band, Zr, is observed at 235nm for sample ZH7 due to the excitation of electrons from the valence band VB to the conduction band CB4+D0, no signal corresponding to the d-d transition is found in the visible region. However, ZH7 has high absorption characteristics in the visible light range of 400-800nm, indicating that ZH7 has a defect that forms a ring-shaped structure, and the transition from VB to the defect level causes absorption in the visible region. It can also be seen that ZH7 has a higher absorption range, and is a desirable choice for improving photocatalytic activity. As shown in FIG. 2b, use (ahv)2The vs hv curve calculates the optical bandgap (Eg) values for samples ZH and ZH 7. The direct bandgaps of ZH and ZH7 were 5.2 and 3.7eV, respectively. The decrease in the band gap value of ZH7 may be due to annealing-induced ZrO2The particle size of the nanostructure is increased.
FIG. 2c records PL spectra of ZH and ZH7 at impurity and defect sites in samples with an excitation wavelength of 300 nm. In the PL spectrum, the broad peak is a combination of two peaks centered in the ultraviolet region of 390nm (3.17eV) and in the visible region of 440nm (2.81 eV). When the sample ZH7 (fig. 2d) was further excited with different wavelengths 380 and 400nm, a blue emission band centered at 440nm appeared sharply. The broad emission band of the visible region may be attributed to ZrO2Hollow single ionized oxygen vacancies and defects in the middle of the ring structure. These defects and vacancies form localized states between VB and CB. It can also be seen from fig. 2 c: the PL intensity of ZH7 was found to be higher than ZH, indicating that the sample annealed in an oxygen-poor or oxygen-free environment, more vacancies were formed.
Therefore, the zirconium dioxide crystal finally obtained by the present invention exhibits a broad absorption spectrum and a low band gap of 3.7eV in the visible light region (400nm to 800 nm). Further, since it exhibits blue light emission even when excited by light having a wavelength of 200nm to 400nm, it is useful as a photoluminescent material.
Verification of photocatalytic degradation
The photocatalytic activity of the synthesized ZH and ZH7 was tested by monitoring the photodegradation of MB dye in aqueous solution, taking Methylene Blue (MB) dye as an example. 1mg/L of MB dye was dissolved, and catalyst ZH7(1g/L) was added to prepare 50mL of an aqueous solution. The final solution was irradiated with a 365nm wavelength ultraviolet lamp. The residual concentration of the MB dye was monitored by measuring the intensity of the absorption band at 663nm using an ultraviolet-visible spectrophotometer (Lambda-35, Perkin-Elmer).
Figure 3a shows the absorption spectra recorded at different time intervals for a MB dye solution mixed with ZH 7. The results show that the intensity of the main absorption band centered at 663nm gradually decreases with the irradiation time due to the degradation of the MB dye.
Fig. 3b shows the standard residual concentration of MB dye versus photodegradation time for MB dye solutions mixed with ZH7 and pure MB dye solutions. The results show that pure MB dye solution had little degradation (< 5%) under 120 minutes of continuous uv irradiation, while the MB dye solution degradation rate of ZH7 sample increased 85.8% under the same irradiation time. The photocatalytic reaction yields are higher in the presence of ZH7 catalyst, probably due to the lower band gap, higher specific surface area of ZH7 and the high density of oxygen vacancies in ZH 7. Since the light-induced molecular reactions take place on the catalyst surface, the large surface area of ZH7 provides more interaction between the dye molecules and the catalyst, thereby improving the catalytic performance of the catalyst.
The photocatalytic stability and recoverability of ZH7 catalyst was tested by cycling, as shown in fig. 3c, the photodegradation rate of MB dye remained essentially unchanged after three cycles of repeated use.
The mechanism of photodegradation is: when electron-hole pairs are generated after UV irradiation of MB dye suspensions, the generated holes are associated with OH-Ions react, electrons and dissolved O2The reaction takes place. This process results in the OH radicals entering the aqueous solution from the radical, the OH radicals entering the aqueous solution and the functional groups c-s of the MB dye+Degradation of dye molecules to CO2、SO4 2-、NO3 -、H2O and H+。
Therefore, the zirconium dioxide crystal finally obtained by the invention has lower energy band, higher specific surface area and oxygen vacancy, and shows excellent photocatalytic performance under ultraviolet irradiation, so the zirconium dioxide crystal can also be used as a photocatalyst.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.
Claims (9)
1. Zirconium dioxide crystal is characterized in that the zirconium dioxide crystal is annular and is monoclinic.
2. The zirconium dioxide crystal according to claim 1, characterized in that the zirconium dioxide crystal has an outer diameter of 4nm to 50 nm.
3. A preparation method of zirconium dioxide crystals is characterized by comprising the following steps:
at ZrOCl2Adding an oxidant into the solution, and fully reacting to obtain a first suspension;
under a closed condition, heating the first suspension at 130-300 ℃, and after full reaction, obtaining a second suspension containing intermediate crystals;
separating the intermediate crystals from the second suspension; and
and annealing the intermediate crystal to obtain the zirconium dioxide crystal, wherein the zirconium dioxide crystal is annular and is a monoclinic system.
4. The method of claim 3, wherein the oxidizing agent is hydrogen peroxide.
5. The method of claim 3, wherein the ZrOCl2The concentration of the solution is 0.1M-1M.
6. The preparation method according to claim 3, wherein the pressure of the first suspension in the closed environment is 20MPa to 60MPa, and the reaction time is 10h to 72 h.
7. The method of claim 1, wherein the annealing is performed under a protective atmosphere.
8. The method according to claim 1 or 7, wherein the annealing temperature is 500 ℃ to 1200 ℃ and the annealing time is 1h to 10 h.
9. Use of the zirconium dioxide crystal according to any one of claims 1 to 2 in a photoluminescent material or a photocatalyst.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05111737A (en) * | 1991-03-29 | 1993-05-07 | Toshiba Ceramics Co Ltd | Connecting ring for horizontal continous casting |
| CN1915836A (en) * | 2006-09-01 | 2007-02-21 | 清华大学 | Method for preparting Nano powder of zirconia |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05111737A (en) * | 1991-03-29 | 1993-05-07 | Toshiba Ceramics Co Ltd | Connecting ring for horizontal continous casting |
| CN1915836A (en) * | 2006-09-01 | 2007-02-21 | 清华大学 | Method for preparting Nano powder of zirconia |
Non-Patent Citations (1)
| Title |
|---|
| SACHIN KUMAR,ET AL.: "One-step hydrothermal synthesis of high surface area m-ZrO2 nanorings with lower band gap, blue emission and high photocatalytic activity", 《JOURNAL OF MATERIALS SCIENCE: MATERIALS IN ELECTRONICS》 * |
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