தற்போதைய செயற்கை மற்றும் அமைப்புகள் உயிரியல்
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Review on the Synthesis Method of Nano Composites and Approach to Making Semiconductors Visible Light Active

Abdu Hussen Ali*

Many studies have been concentrated on the degradation of toxic organic compounds in waste water via photo catalysis of various semiconductors. It has attracted great attention in modern science because of its potential in solving many current environmental problems such as air and water pollution. The common photo catalysts are primarily nano composite metal oxides, are known to be good photo catalysts for the degradation of several environmental contaminants due to their high photosensitivity, stability and non-toxic nature. There are different approaches for the synthesis of nanomaterials: Top down and bottom up approaches. Top-down approach is best approach and refers to successive cutting of a bulk material to get nano sized particles. These applications have their interest in controlling particle size, particle shape, size distribution, particle composition and degree of particle agglomeration. Some nanoparticles have large band-gap which leads to high recombination rate of photo generated electron-hole pairs limits their utilization for photo catalytic applications. More recently, significant efforts have also been made to develop new or modified semiconductor photo catalysts that are capable of using visible-light (λ=400 nm-700 nm) including semiconductor coupling, metal ion doping, nonmetallic element doping, and sensitization with organic dyes. Coupling of two semiconductor nanoparticles with different band gap widths has been demonstrated in many studies as one of the most effective ways to reduce the recombination of electron-hole pairs and consequently, achieving a higher photo catalytic activity. Moreover, the ternary nano composites have high visible light photo catalytic activity and organic dyes can be decomposed efficiently, implying the higher photo catalytic activity of the ternary nano composites.