chapter  4
25 Pages

Semiconductive Nanocomposite Films for Clean Environment

WithJoe H. Hsieh

Nanocrystalline materials are single-phase or multiphase polycrystalline materials having grain sizes smaller than 100 nm. Nanocrystalline materials may contain crystalline, quasicrystalline, or amorphous phases, and can be metals, ceramics, or composites (nanocomposites). Because of the

4.1 Nanocomposite Thin Films .................................................................................................. 129 4.1.1 Nanocrystalline Materials ........................................................................................ 129 4.1.2 Metal Nanoparticles .................................................................................................. 130 4.1.3 Nanocomposite Materials ......................................................................................... 130 4.1.4 Synthesis of Nanocomposite Films .......................................................................... 131

4.2 Application in Water Splitting .............................................................................................. 132 4.2.1 Progress on Electrode Materials ............................................................................... 134

4.2.1.1 TiO2 ............................................................................................................ 135 4.2.1.2 Visible-Light Photocatalytic Materials ...................................................... 135

4.2.2 Enhanced Efficiency by Nanocomposites ................................................................ 136 4.2.2.1 Metal-Semiconductor Nanocomposites .................................................... 136 4.2.2.2 Semiconductor Nanocomposites ................................................................ 140

4.3 Application in Bactericide and Water Disinfection .............................................................. 142 4.3.1 Bacteria ..................................................................................................................... 142 4.3.2 Antibacterial Materials ............................................................................................. 142 4.3.3 Applications of Antibacterial Materials ................................................................... 142 4.3.4 Mechanisms of Bactericide ...................................................................................... 143

4.3.4.1 Bactericide by Metal Ions .......................................................................... 143 4.3.4.2 Bactericide by Photocatalysis .................................................................... 144

4.3.5 Nanocomposite Thin Films for Bactericide ............................................................. 144 4.3.5.1 Enhanced Dissolution of Metal Ions .......................................................... 144 4.3.5.2 Metal-Ceramic Nanocomposites............................................................... 145 4.3.5.3 Metal-Photocatalyst Nanocomposites ....................................................... 146 4.3.5.4 Semiconductor-Semiconductor Nanocomposites ..................................... 147

4.4 Summary and Recent Developments .................................................................................... 147 References ...................................................................................................................................... 150

extremely small dimensions, a large volume fraction of the atoms is located at the grain boundaries, and this brings special properties to these materials. The properties of nanocrystalline materials are very often superior to those of conventional polycrystalline coarse-grained materials. Nano crystalline materials exhibit superior mechanical properties, such as high strength/hardness, enhanced diffusivity, improved ductility/toughness, reduced density, and reduced elastic modulus, and also have higher electrical resistivity, higher thermal expansion coefficient, and superior magnetic properties in comparison with conventional coarse-grained materials. The concepts of nanocomposites are being investigated with certain emphasis on semiconductor composites with nano-sized metal particles embedded in the matrix [1,2]. Overall, there appears to be a great potential for the nanocrystalline materials to be applied in almost every area. The extensive investigations on structureproperty correlations in nanocrystalline materials have begun to unravel the complexities of these materials and have provided many important results as well as many new concepts [3].