Synthesis And Properties Of Nanostructured Gallium Based Oxide/Hydroxide Materials

Gallium based nanomaterial,as a significant semiconductor material,has extensive application value in the fields of photo catalytic,luminescence,optoelectronic devices.Based on the practical application of these areas,their synthetic strategy,element composition,morphology structure and physical and chemical properties have been investigated in depth,and great progress has been made.However,the performance of gallium based nanomaterial is effected by the synthesis methods,surface and interfacial structure,lattice defects,etc.,and there are still many issues to be addressed.For instance,the catalytic activity of exposed crystal face is not high and the efficiently control of the exposure of highly reactive activity crystal faces to improve its photocatalytic properties needs our further research.Usually,ZnGa₂O₄ based luminescent materials are obtained by gas phase method and solid phase method,and very high temperature is needed.Therefore,it is urgency to find method to prepare ZnGa₂O₄ based materials with full color luminescence properties at low temperature.The recombine of excellent physical and chemical properties of gallium based nanomaterial and other functional material to obtain new functional composite materials remained to be explored.In this paper we made further in-depth exploration and study with gallium based nanomaterial to solve these problems.1.Synthesis and enhanced photocatalytic activities of coexposed {111} and {110}facets ZnGa₂O₄ nanoplates.Facet-control has been a fascinating method for preparation of highly active photocatalysts.We reported surfactant-assisted synthesis of single-crystalline ZnGa₂O₄ nanoplates with coexposed {111} and {110} facets via a facile hydrothermal process.Studies of their photocatalytic properties have clearly revealed that the nanoplates with two facets coexposed exhibit superior photocatalytic activities compared with the other two types of ZnGa₂O₄ nanostructures for H2 evolution and organic contaminant degradation.DFT theoretical calculations combined with valence band XPS results indicate that the exposed {110} and {111}facets of the ZnGa₂O₄ nanoprisms exhibit different band edge positions and band structures.The two coexposed facets can form a "surface heterojunction" within single ZnGa₂O₄ nanoplates,which promotes the photo-excited electron migration to the {110} facets and hole migration to the {111} facets,respectively.Also,the difference in the hole effective mass between the two coexposed facets may help to overcome the overflow effect.Therefore,the photocatalytic activities of ZnGa₂O₄ nanoprlisms are significantly improved.Our research provides a typical example for improved photocatalytic property through surface modulation and may bring new insight into the design and fabrication of high-efficiency photocatalysts.2.Synthesis and full color emission properties of ZnGa₂O₄ nanoflowersThe synthesis of zinc gallate based luminescent materials usually requires very high temperature.Therefore,looking for low temperature synthesis method which is energy conservation and emissions reduction has been becoming the current urgent issues.In our study a hydrothermal method was used.With the aid of ethylenediamine template,undoped(ZnGa₂O₄),Mn²⁺ doped(ZnGa₂O₄:Mn²⁺)and Cr³⁺ doped zinc gallate(ZnGa₂O₄:Cr³⁺)luminescent nanomaterials are synthesized at low temperature.The luminescent materials are composed of the size of 5 micrometers nano flowers,each flower is formed by hierarchical structure with 6 to 10 nm nanosheets.With UV light irradiation,ZnGa₂O₄,ZnGa₂O₄:Mn²⁺ and ZnGa₂O₄:Cr³⁺ show blue,green and red color emission performances by the self-excited,Mn²⁺ ions and Cr³⁺ excitation respectively.Therefore,three primary colours can be obtained in the same zinc gallate based luminescent materials.Because of the influence of the surface effect,the luminescence materials have two different fluorescence lifetime.These zinc gallate based luminescent nanomaterials are expected to be used in the field of color display,biological imaging and application white LEDs.3.Synthesis and enhanced aggregation induced emission?AIE?properties of organic-inorganic hybrid nanomaterialsAttracted by their fascinating prospect of applications in biomedicine,fluorescent probes and biosensors,great efforts have been focused on AIE phenomenon.we report the design and preparation of a novel hybrid AIE system based on grafting carboxyl group functionalized salicylaldehyde azine?CA-SAA?molecules onto monodispersed colloidal GaOOH nanocubes.The aggregation is driving by strong hydrophobic attraction between CA-SAA molecules and NC surfaces.As-formed CA-SAA/GaOOH nanohybrids showed tunable sizes and dispersities upon tuning the GaOOH concentration or the relative ratio of the organic and inorganic components.One unique feature of these AIE nanohybrids is that the NC-induced aggregation avoids the introduction of a second solvent,prevents possible solvent-induced relaxation or ionization,provides better restriction of inter-and intra-molecule rotations.Compared with the AIE of CA-SAA aggregates formed in a mixed solvent,CA-SAA/GaOOH nanohybrids exhibit a distinctly blue-shifted emission,a quantum yield up to 25%compared with the highest quantum yield of 9%in THF/H2O mixtures.Our observation confirms that inorganic nano species can induce aggregation of properly modified AIE molecules and show distinct AIE features.The AIE hybrid material can be used as new organic-inorganic hybrid LEDs,bioimaging,photoelectric devics.