Application of Semiconductor Nanomaterials
in Catalysis and Medical Sciences
A Scientific Document submitted to
National Center for Catalysis Research
Indian Institute of Technology, Chennai for
10th Catalysis orientation programme-2009
Discipline of Inorganic Materials and Catalysis
Central Salt and Marine Chemicals Research Institute
Council of Scientific and Industrial Research (CSIR)
GB Marg, Bhavnagar – 364 002
2. Application of Semiconductor Nanomaterials
2.1 Semiconductor Nanomaterials in Catalysis
2.1.1 Semiconductor Nanomaterials for Environmental Purification 2.1.2 Semiconductor Nanomaterials for Hydrogen Production 2.1.3 Semiconductor Nanomaterials for Green Organic Transformations
3. Semiconductor Nanomaterials in Medical Sciences
3.1 Semiconductor Nanomaterials for Detection of Protein and DNA 3.2 Semiconductor Nanomaterials for Stem Cell imaging 4. Conclusion
A semiconductor is a material that has an electrical conductivity between a conductor and an insulator. In semiconductors, the highest occupied energy band, valence band is completely filled with electrons and the empty next band is conduction band. The resistivities of the semiconductor can be altered by up to 10 orders of magnitude by doping or external biases. In the case of conductors, that have very low resistivities, the resistance is difficult to alter, and highest occupied energy band is partially filled with electrons and insulator has extremely high resistivities. It is difficult to alter the resistivity through doping or external fields and the band gap between the valence band and conduction band is large. In a metallic conductor, current is carried by the flow of electrons. In semiconductors, current can be carried either by the flow of electrons or by the flow of positively-charged holes in the electron structure of the material.
In the past 10 years, nanomaterials with diameters in the range of 1-20 nm, has become a major interdisciplinary area of research interest and their extremely small feature size; have the potential for wide-ranging industrial, biomedical, and electronic applications. Surface and interfaces are very important for nanomaterials, but in the case of bulk materials, relatively small percentage of atoms will be at or near a surface or interface. In nanomaterials, the small feature size ensures that many atoms, perhaps half or more in some cases, will be near interfaces. Surface properties such as energy levels, electronic structure, and reactivity can be quite different from interior states, and give rise to quite different material properties. Nanocapsules and nanodevices may present new possibilities for drug delivery, gene therapy, and medical diagnostics. In 1991, S. Iijima  has reported the first observation of carbon nanotubes. Carbon nanotubes have been shown to have unique properties, stiffness and strength higher than any other material. Carbon nanotubes are reported to be thermally stable in vacuum up to 2800 °C, to have a capacity to carry an electric current a thousand times better than copper wires, and to have twice the thermal conductivity of diamond. Carbon nanotubes are used as reinforcing particles in nanocomposites, but also have many other potential applications. They could be the basis for a new era of electronic devices smaller and more powerful than bulk materials. The nanocomputer was already made based on carbon nanotubes. The materials having size in the range of nanometer scale, having unique properties than bulk materials.
Recently there has been substantial interest in the preparation, characterization and application of semiconductor nanoparticles that play a major role in several new technologies. When the size of semiconductor materials reduces to nanoscale, their physical and chemical...
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