Vapor-phase Synthesis, Characterization And Photoluminescence Properties Of Quasi-one-dimensional Nanomaterials

In this paper, quasi-one-dimensional nanostractured ZnS, GeO2/ZnGeO3, MgO and ZnO have been synthesized by thermal evaporation. The morphology, structure, chemical composition and physical properties of these quasi-one-dimensional nanostructures are characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) and photoluminescence (PL) spectroscopy. Some novel methods to synthesize quasi-one-dimensional nanostructures have been developed. The growth mechanisms of one-dimensional nanostructures of different morphologies are further investigated. The relationship between photoluminescence properties and the morphologies is discussed. The following are the main contents and conclusions:1. Study on ZnS nanostructures synthesized by thermal evaporationMass production of uniform wurtzite ZnS nanostructures has been achieved by a H2-assisted thermal evaporation technique. Neither a metal catalyst nor a template was introduced in the synthesis process. X-ray diffraction analysis, scanning electron microscopy and high-resolution transmission electron microscopy observations show that the ZnS nanostructures consist of nanobelts, nanosheets with a hexagonal wurtzite structure. The as-synthesized nanobelts have a thickness of several tens of nanometers and a width of several hundreds of nanometers. The morphologies and diameters of ZnS nanostructures grown in different temperature zones are different. The ZnS nanobelts with a uniform width of tens of nanometers are formed in the temperature zone of 940-810 ℃. The ZnS nanocrystals of diameters of hundreds of nanometers are formed in the temperature zone of 810-720 ℃. The ZnS nanowires with diameters of tens of nanometers are formed in the lower temperature zone of 720-670 ℃ . The study shows that the morphology and diameter of ZnS nanostructures synthesized by thermal evaporation correlate closely with the growth temperature of ZnS nanostructures.2. Bulk-quantity synthesis and photoluminescence properties of chain-like GeO₂ /ZnGeO₃ crystal structuresBulk-quantity of uniform chain-like GeO₂/ZnGeO₃ structures has been achievedby a thermal evaporation of a Ge and Zn mixture. X-ray diffraction analysis indicates the product is mainly composed of GeO2 mixed with a bit of ZnGeO3. Scanning electron microscopy characterization shows that the structures consist of particle chains with an almost uniform distance between each particle. The chain-like structures consist of two parts: the ellipsoidal part and the linear part. Energy-dispersive spectroscopy reveals that different parts of the structure have different compositions. Room-temperature photoluminescence measurement shows that the synthesized structures have a strong emission band at a wavelength of 488.5 nm.3. Preparation and characterization of branched MgO nanostructuresMass production of branched MgO nanostructures has been achieved by a thermal evaporation way. X-ray diffraction analysis shows the product is composed of pure single-crystalline MgO. Scanning electron microscopy and transmission electron microscopy characterizations show that the MgO branched nanostructures consist of many slim nanowires grown from the thick MgO rods. The as-synthesized nanowires have a length of several tens of microns and a diameter of several tens of nanometers. The preferred growth direction of the nanowires is [001]. Room-temperature photoluminescence measurement shows that the synthesized MgO nanostructures have a strong emission band at 401 nm and a weak emission band at 502nm.4. Study on the synthesis and photoluminescence properties of ZnO nanostructures.We synthesized ZnO nanowires and nanoparticles at 800℃ in the ambience of Ar2/O2 at a flow rate of 50 sccm. We synthesized ZnO whiskers at 900 ℃ in the air. The as-synthesized nanowires have diameters in the range of 30-100 nm. The diameters of the nanoparticles are about 50 nm. The diameters of the whiskers can reach s...