Dissertation > Excellent graduate degree dissertation topics show

Controllable Synthesis and Applications of Copper, Zinc-Based Micro/nanosemiconductors

Author: LiuJun
Tutor: GengBaoYou
School: Anhui Normal University
Course: Physical and chemical
Keywords: Zinc Sulfide Zinc Oxide Cuprous Oxide Micro/nanosemiconductor Properties
CLC: TB383.1
Type: Master's thesis
Year: 2010
Downloads: 65
Quote: 0
Read: Download Dissertation

Abstract

Micro/nanomaterials possess more special physical and chemical properties than block materials owing to quantum size effects, surface effect and size effect. Also, because of band energy of semiconductor materials is wide which make the kinetic energy of electron low, therefore, the decrease of the size of semiconductor materials has huge influence to the physical and chemical properties. Comparing with block semiconductor materials, micro/nanomaterials possess unique properties, so it can be applied in many novel fields, such as chemical sensor, biosensor, photocatalytic degradation, and so on. Therefore, many works about size and morphology controllable synthesis of semiconductor materials have been reported in recent years. And, many synthesized methods have shown in these reports, which can divide into two parts: "bottom up" and "top down". "bottom up" means that using atoms, molecules or ions as precursors to prepare micro/nanomaterials, including hydrothermal method, sol-gel method, microemulsion method and so on; and "top down" means that using block materials as precursor to prepare micro/nanoscaled materials through physical or chemical routs, including chemical vapor deposition, physical vapor deposition and mechano-shattering method and so on. In various synthesis methods, adjusting reaction temperature, reaction time, ratio of reactants, and concentration of reactants and adding to appropriate surfactants, using molecule model or hard model all can control the size and morphology of products. In this paper, we choose Cu and Zn based semiconductor materials as research objects, and study the application of obtained materials in gas sensor, biosensor, and photocatalytic fields. The detail contents of this paper as follows:1. Heterostructured ZnS/Zn3(PO)2 has been prepared through hydrothermal method. The morphology of the heterostructure is hemisphere, the plane of the hemisphere is composed of Zn3(PO4)2-4H2O and the polar surface is composed of ZnS nanosheets. In our experiment, the amount of H3PO4 is critical to the morphology and structure of samples. By adjusting the amount of H3PO4, it can easily control the morphology of samples. Besides, we propose the corresponding growth mechanism for the growth process and study the photocatalytic performance of degradation of Rhodamine B under UV light irradiation. The result shows that the heterostructured ZnS/Zn3(PO4)2·4H2O can degradate 1.0x10°M Rhodamine B completely with 45 min. ZnS/Zn3 exhibits more excellent photocatalytic activity than P25 TiO2 and ZnS microspheres can be attributed to two aspects, first, the sample has high specific surface area which can increase the degradation activivity; second, the particular heterostructure make the band energy larger that can accelerate the photocatalytic reaction. 2.Self-assembled Cu2O quasi-sphere microarchitecture hasbeen synthesized through a microwave irradiation method without any surfactant or model. A possible "nucleate-ripen-split-self-assemble" mechanism has been proposed to explain the growth process. The reaction temperature is the most important factor to the morphology of the samples. Also, the concentration of the precursors has influence to the morphology of the samples. A gas sensor has been prepared based on the Cu2O quasi-sphere microarchitectures, which was used to detect the alcohol vapor and H2S gas. The testing result exhibits the sensor possesses high sensitivity, good reproducibility and the short response and recovery time is 15 s and 20 s respectively.3. Cuprous oxide with core-shell structure was prepared under room temperature through a simple reduced reaction using ascorbic as reductant. Ostwald ripening processes are proposed to explain the growth mechanism of the homogeneous Cu2O core-shell structure. Meanwhile, the influences of reaction time and temperature have been also researched for exploring the growth process. In addition, the obtained homogeneous core-shell Cu2O are modified onto a glass-carbon electrode which is applied to detect dopamine (DA) in the solution. The characterizations of electrochemical impedance spectrum (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) show that the modified electrodes exhibit high efficiency toward detection of DA. The anodic peak current (measured by DPV) increase linearly with the concentration of dopamine in the range of 3.0×10-7 to 5×10-4 M. The detection limit has been estimated to be 1.0×10-7 M. The high sensitivity of the determination of dopamine by using the modified electrode implies that homogeneous core-shell Cu2O may be of great potential in biosensor filed.4. Novel ZnO multi-layer architectures have been prepared successfully by using poly (sodium 4-styrenesulfonate) (PSS) as soft template under hydrothermal rout. The mass ratio of reactants (Zn(CH3COO)2-2H2O and PSS) plays a critical role in controllable synthesis of ZnO with different structures. The as-prepared multi-layer architectures are with a hexagonal profile and consist of many nanosheets. The thickness of these nanosheets also can be controlled by the mass ratio of reactants. The gas sensing properties of the as-synthesized ZnO multi-layers architectures are investigated in detail. The results indicate that the ZnO multi-layer architectures exhibit superior response to acetone and ethanol. The gas sensor possesses good reproducibility, and the response time and recovery time is 4 s and 6 s, respectively. These results imply that ZnO multi-layer architectures have potential application in gas sensor field.

Related Dissertations

CLC: > Industrial Technology > General industrial technology > Materials science and engineering > Special structural materials
© 2012 www.DissertationTopic.Net Mobile