Effect of Water Content on the Morphology of ZnO Powders Synthesized in Binary Solvent Mixtures by Glycol Process

Abstract

ZnO materials with a range of different morphologies have been successfully synthesized via a simple double-solvothermal method in the presence of glycine. The morphologies of the products can be controlled from superstructures to microrods by adjusting the amount of water in the EtOH/H 2 O system. Photoluminescence (PL) studies reveal that the more amount of water was used, the stronger PL relative intensity of the green emission is, but the weaker ultraviolet emission. This might be attributed to the more defects of the products when the more water was used. The catalytic studies show that all the samples have good abilities to decrease decomposition temperature around 3006C and the decomposition temperature lowers with the increase of the relative intensity of ZnO green emission. C ontrol of the structure, size, and shape of inorganic materials has received increased attention in current materials syntheses due to the fact that they play very important roles in correlating to their magnetic, electrical, optical, and other properties [1][2][3][4] . Over the past two decades, a wide range of one-dimensional nanostructures, such as wires, rods, belts, and tubes, has been prepared [5][6][7][8] . So far, based on these 1D forms, intensive attention has been attracted to realization of 3D superstructures by patterning micro-/nano-structured building blocks with complex geometry, due to their unique properties for potential applications 9,10 . Commonly, surfactants are used as additives to assist the synthesis of materials with 3D superstructures. Therefore, developing facile, solution-based, morphology-controlled methods to fabricate novel self-assembled architectures remains challenge.Zinc oxide (ZnO), an important semiconductor with a band gap of 3.37 eV at room temperature, has attracted great interests due to its unique properties and wide applications in field effect transistors, chemical sensors, transparent conductors, and ultraviolet light emitting devices [11][12][13][14] . The properties of ZnO are strongly dependent on its morphology and aspect ratio, as well as on the size, orientation, and density of the crystal [15][16][17] . And these structural characteristics have important applications in optoelectronics and photocatalysts. ZnO with different morphologies has been produced by various synthetic methods 18. The solution based methods, such as solvothermal/hydrothermal and sol-gel processes, are attractive because the synthesis conditions used are mild and the processes are very simple. Compared to the conventional hydrothermal/solvothermal process, in which commonly only one kind of solvent is used, a double-solvothermal or a mixed-solvothermal process would have much greater influences on the structural control for various materials, because the properties of the mixed solvent can be controlled by adjusting the type and volume ratio of the solvents 19 . In biomineralization, organisms can exert great control over mineral deposition from the solution phase by using biological molecules as matrices o...

Effect of Microwave Radiation Power on the Size of Aggregates of ZnO NPs Prepared Using Microwave Solvothermal Synthesis

“…Many forms could be obtained in the microwave synthesis of ZnO nanomaterials (NMs), e.g., spherical particles, rods, flowers, needles, whiskers and layers [ 11 , 12 , 18 , 24 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ], where the control of ZnO NMs size is possible by changing the synthesis duration, substrate concentration, substrate type, process temperature, solvent type, pH and addition of surfactants [ 11 , 18 , 19 , 38 , 39 , 40 , 41 , 42 , 43 ]. However, the size control of the forming aggregates is not a very commonly discussed aspect of ZnO NPs synthesis.…”