Zhiqin Cao

Synthesis of β-Ga2O3 nanorods

Abstract β-Ga 2 O 3 nanorods with diameters of 10–60 nm were synthesized through a simple gas reaction method and were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The SEM image showed that most of the nanorods were straight. XRD, SAED and HRTEM indicated that the nanorods were monoclinic Ga 2 O 3 single crystals.

Superior optical properties of Fe3+–W18O49 nanoparticles prepared by solution combustion synthesis

Modification by metal-doping allows the design of new nanomaterials with enhanced optical properties. In this paper, the photocatalytic effects of Fe3+-doped W18O49 nanorods prepared by solution combustion synthesis were studied for the first time. The Fe3+-doped W18O49 powders were investigated by X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction, and X-ray photoelectron spectroscopy. The powders were well-crystalline with diameters ranging from 50 nm to 250 nm and the length decreasing from more than 10 μm to 4 μm on average. The photoluminescence (referred to as PL here after) spectrum showed that the emission intensity increased with increasing Fe3+ doping, suggesting that more defects were generated. Moreover, this novel composite catalyst displayed excellent photocatalytic efficiency towards the degradation of organic compounds in aqueous media under UV-visible light irradiation. In particular, 0.5 wt% Fe3+-doped W18O49 had the best photocatalytic efficiency. This improvement was mainly attributed to the synergistic effect between Fe3+ and W18O49 nanopowders and the defects in the nanostructure caused by doping.

The formation of CuO porous mesocrystal ellipsoids via tuning the oriented attachment mechanism

We report a new chemical reaction route to synthesizing CuO porous mesocrystal ellipsoids via decomposition of copper vanadium oxide under hydrothermal conditions. By finely tuning the oriented attachment growth mechanism of CuO, a porous mesocrystal structure was synthesized. Structural and morphological evolutions of the CuO product were investigated and the formation of CuO porous mesocrystal ellipsoids here was essentially determined by the amount of ammonium metavanadate. An oriented nanoparticle aggregation with tailoring of the structure, including compact mesocrystals and porous mesocrystals, could be achieved in different concentrations of reactants. The strategy of constructing the structure via an oriented attachment growth mechanism could be applied to the synthesis of other nanomaterials with complex structures.

Solution combustion synthesis of Ni–Y2O3 nanocomposite powder

Abstract Ni–Y 2 O 3 nanocomposite powder with uniform distribution of fine oxide particles in the metal matrix was successfully fabricated via solution combustion process followed by hydrogen reduction. The combustion behavior was investigated by DTA-TG analysis. The influence of urea to nickel nitrate (U/Ni) ratio on the combustion behavior and morphology evolution of the combusted powder was investigated. The morphological characteristics and phase transformation of the combusted powder and the reduced powder were characterized by FESEM, TEM and XRD. The HRTEM image of Ni–Y 2 O 3 nanocomposite powder indicated that Y 2 O 3 particles with average particle size of about 10 nm dispersed uniformly in the nickel matrix.

Facile route for synthesis of mesoporous graphite encapsulated iron carbide/iron nanosheet composites and their electrocatalytic activity

Mesoporous graphite encapsulated Fe3C/Fe nanosheet composites have been synthesized by a facile template free method using ferric nitrate, glycine and glucose as raw materials. X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and Raman spectrometer have been used to characterize the composites. The formation process and morphology of the products have been discussed in detail. Interestingly, this facile route can synthesize graphite encapsulated Fe3C, Fe3C/Fe and Fe composites with two dimensional nanosheet structure by tuning the reaction temperature and the Fe3C and Fe nanoparticles with size less than 30nm are well dispersed on the carbon sheet. The mesoporous graphite encapsulated Fe3C/Fe nanosheet composites with a high specific surface area have application in non-noble metal electrocatalysis for hydrogen evolution reaction.

Ultrafast synthesis of amorphous VOx embedded into 3D strutted amorphous carbon frameworks–short-range order in dual-amorphous composites boosts lithium storage

Crystalline vanadium oxides have some unique advantages, including abundant material sources, high energy density, and a typical layered structure, making them promising anode candidates for lithium-ion batteries. However, the intrinsic low electrical conductivity and volume expansion side effects severely limit their capacity and cyclability at high charge/discharge rates. Herein, unique dual-amorphous composites with 3D strutted amorphous carbon sheet framework encapsulated amorphous vanadium oxide particles have been prepared by an ultrafast (within one minute), ultralow temperature (172 °C), one-step and large-scale combustion synthesis method. We demonstrate that the dual-amorphous VOx/C composites provide a large number of accessible active sites and defects for lithium ion intercalation/deintercalation and are self-accommodative to tolerate volume expansion. Another noteworthy point is the short-range ordered atomic arrangement observed in amorphous VOx that exhibits a larger interlayer spacing (d(001) = 4.80 A) than other crystalline vanadium oxides. This particular structure has the potential to accommodate more lithium ions and tolerate the volume expansion. Meanwhile the 3D hierarchical porous sheet-like structure facilitates the transfer of electrons and lithium ions. The electrochemical measurements show excellent lithium storage performance with high capacity, good rate capability and long-term cycling stability of the composites.

The role of dissolution in the synthesis of high-activity organic nanocatalysts in a wet chemical reaction

The synthesis of high-activity nanocrystals (NCs) is a key factor in the field of nanocatalysis. By combining nucleation/growth with the dissolution of crystals in a reaction–diffusion system for the first time, we achieved a simple strategy for the one-step synthesis of high-activity uniform nanocatalysts without capping agents (CAs) via simply adjusting the reaction time of the wet chemical reaction (WCR). In this work, the shape evolution of hydrate tetraphenyl-porphyrin zinc (ZnTPP·H2O, ZnP) NCs was systematically studied during the reaction of their precursor with water. Regular, thermodynamic octahedral ZnP NCs can be synthesized at the 3rd hour, and typical rough step-type cuboctahedron NCs can be obtained after 3 days due to the occurrence of chemical dissolution in the multistep WCR. Our results reveal that the crystal dissolution process involves the disappearance of low-energy facets followed by the appearance of high-energy facets. Furthermore, ZnP/rubrene heterojunctions can be easily prepared based on the rough NCs. Compared with regular octahedral ZnP NCs and even nanosheets with more active {020} facets, the rough and heterostructured ZnP NCs exhibit higher performance in photocatalytic hydrogen evolution (PHE). These findings provide a convenient method to synthesize highly active nanocatalysts in a multistep WCR.