Applications of Morphology-Controlled Semiconductor-Based Nanocomposites

Abstract

Chapter 1 reports a brief overview of semiconductor nanomaterials havnig peculiar optical and physical properties. Especially, theses novel features are strongly related to three crucial parameters such as shape, size, and surface conditions. Thus, the size and shape-dependent phenomenon of nanosized-materials are explained in detail. In addition, efficient synthetic approaches, as well as application strategies, to well-defined nanocrystals with controlled shape and size are also described. <br/> Chapter 2 describes that SnO2/ZnS nanocomposites of SnO2 quantum dots (QDs)-deposited ZnS nanorods having highly enhanced photocatalytic activity and photostability have been fabricated via a facile two-step hydrazine-assisted hydrothermal process without involving any surface treatments. A rational synthesis of high-quality SnO2/ZnS heterojunction nanocomposites via a simple and friendly manner has been reported for the first time. Furthermore, The incorporation of SnO2 QDs increases the photocatalytic efficiency of ZnS nanorods due to the following reasons: high separation of photogenerated charge carriers owing to type II band configuration, direct contact at interfaces, increased active surface sites, and extended the light absorption range to the visible region. Thus, our prepared SnO2/ZnS nanocomposites are considered to have great potential for photodegradation nanocatalysts in the field of waste-water treatment.<br/> Chapter 3 presents that Cu(I)-exchanged ZnS nanoadsorbents having highly efficient adsorption performances toward cationic dyes and heavy metals have been fabricated via facile cation exchange using pristine ZnS nanostructures as templates. Their surface properties such as surface charges and areas have been controlled by adjusting the molar ratio of Cu to Zn (RCu/Zn). The adsorption efficiency of Cu-exchanged ZnS nanoadsorbents is highest at a RCu/Zn value of 0.4 because the net surface charges of the nanocomposites resulting from the substitution of Cu(I) ions for Zn(II) ions in the ZnS lattice are electronically most negative. Furthermore, the adsorption of cationic dyes to our nanoadsorbents is found to be mainly driven by attractive electrostatic interactions while van der Walls forces also play a role. Overall, our prepared Cu-exchanged ZnS nanoadsorbents are suggested to have great potential applicability in the treatment of wastewater containing cationic dyes or heavy metals.<br/> In Chapter 4, the thickness and the morphologies of silver nanoshells have been tuned facilely and eco-friendly via laser irradiation. The irradiation of nanosecond laser pulses has transformed silver seeds or nanoparticles adsorbed to the silica surfaces of Ag@SiO2 nanostructures into silver nanoshells, producing Ag@SiO2@Ag nanostructures having highly enhanced catalytic performances. The catalytic degradation of rhodamine B has been found to occur on silver nanoshells (k1 process) or on core silver nanospheres (k2 process)