Liquid Phase Synthesis And Characterization Of Nanostructured Functional Oxides（Cu₂O、ZnO、Bi₂O₃ And SnO₂）

Nanostructured functional oxides belong to a very important class of functional materials.Therein,the micro/nano Cu2O,ZnO,Bi2O3 and SnO2 have the characteristics of safety,non-toxicity and environmentally friendly along with excellent optoelectronic,catalytic and electrochemical properties and so these oxides have important application potentials in the field of semiconductor devices,solar cells,biosensors and photocatalysis.At present,although the researches of low-dimensional micro/nano metal oxides nanomaterials have made considerable progress by using liquid phase preparation method,the development of green,simple and batch controlled preparation technology is still challenging.In this paper,green eco-friendly gallic acid which used both as reductant and crystal growth modifier was firstly used to prepare micro/nano Cu2O,ZnO,Bi2O3 and SnO2 in a controlled manner by liquid-phase reduction method without any other surfactants.The effects of synthesis conditions including pH value,initial material ratio,reaction temperature,titration speed and reaction time on the phase and morphology of the synthesized product were studied.The main research results are as followed:(1)The micro/nano Cu2O with different morphologies were successfully controllable synthesized with gallic acid.The results show that the morphology of Cu2O crystal changes from irregular sphere,linear,rod,cube,icosahedron to hexahedron with the increase of pH value.At pH=10,the reactant concentration ratio of c(Cu2+):c(GA)has a great influence on the Cu2O morphology.With the concentration increase of Cu2+ ratio,the morphology of Cu2O changed continuously with polyhedron,linear,dumbbell and cuboid.In addition,the holding temperature and the mixing titration speed also affect the morphology of Cu2O crystals.The growth mechanism of Cu2O crystals with different morphologies is different:i.e.the linear shape Cu2O gradually changes from coarse-grained polycrystalline to smooth-surfaced Cu2O single-crystal through Ostwald ripening and directional growth,and the cubic Cu2O crystal grows into a typical step growth mechanism.The photocatalytic degradation of methyl orange by linear shape Cu2O gradually increased with the increase of light irradiation time,and the degradation rate of Cu2O was 78%after 3 h light exposure.The degradation rate of cubic shape Cu2O was small.(2)ZnO,Bi2O3 and SnO2 with different morphologies were prepared by liquid-phase method by using gallic acid as a growth regulator.The morphology of ZnO crystals changed from short column to long rod with the increase of pH value.When reactant concentration ratio of c(Zn2+):c(GA)was changed,the morphology of ZnO changed from rod to needle as the proportion of Zn2+ increased.The formation process of ZnO is the growth of nanoparticle aggregates into single-crystal rods with smooth surface by orientated attachment.In addition,barium and flaky Bi2O3 could be obtained using different starting salts.Both linear and rod-shaped Bi2O3 could be attained through changing the pH adjustment method.The nano SnO2 could only be generated at a specific pH=10.(3)Using liquid reduction method,Cu2O/ZnO,Bi2O3/SnO2,Cu2O/SnO2 nanocomposites powders can be prepared by one-step method through the reduction of gallic acid and the control of crystal morphology.