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The fabrication of semiconducting materials with controlled size and morphology is an exciting, rapidly expanding research area for realizing the peculiar physical/chemical properties and the possible practical applications at the nano-to-microscale. Also, the technological applications for nanocomposites of organic/inorganic materials are of great interest in scientific research due to their unique and tunable electronic and optical properties. The semiconducting materials at nanoscale are widely used for the manufacturing of various electronic, electrical and photovoltaic devices owing to their unique band structure, optical properties, good charge mobility and ability to absorb photons from light. Among various photovoltaic devices, a regenerative photoelctrochemical solar cell called DSSC is a promising photovoltaic device for achieving reasonably high conversion efficiency as compared to the conventional silicon solar cells. Various metal oxide semiconducting nanomaterials such as ZnO, TiO2, SnO2, Nb2O5 and CeO2-based thin film electrodes and their nanocomposites have also shown comparably good conversion efficiency of DSSC due to their good optical and electronic properties. These semiconducting metal oxides possess high surface area which is essential for acquiring a high amount of dye adsorption which leads to higher light harvesting efficiency and photocurrent density. Additionally, the morphology and sizes of these semiconducting materials, particularly one dimensional (1D) nanostructures like nanorods (NRs), nanowires (NWs) and nanotubes (NTs)-based electrodes have shown increased electron transfer during the operation of DSSCs. However, there is still a demand for improvements such as the development of a sophisticated potential technology for achieving high photovoltaic properties. On the other hand, the metal oxide and its nanocomposites are also highly capable for the photocatalytic oxidation of organic compounds/ pollutants from waste water. The use of organic dyes, chemicals and heavy metals in many textile and other industries are the major pollutants in water. These harmful organic dyes cause injuries to the ingestion systems, lungs and the respiratory systems of humans. At present, the removal of these dyes from polluted or waste water is an important issue for balancing the ecosystem. Several conventional methods like coagulation, reverse osmosis and adsorbents are extensively employed to remove organic dye from waste water. However, the installations of these methods are highly expensive and also incapable of complete removal of dyes. Recently, the photocatalytic processes have been accepted as promising and effective ways to decompose the organic pollutants into less dangerous matter. Thus, they are considered as efficient and cost-effective alternatives for water remediation. In this chapter, we have briefly discussed the metal oxides like TiO2, and ZnO and their nanocomposites for their potential applications of DSSCs and their photocatalytic degradation. The chapter includes the brief literature surveys, properties and the latest research advancements/trends for the development of various metal oxide nanomaterials, and the nanocomposites of organic/inorganic nanomaterials. The preparation methods, morphologies, and physical and chemical properties of metal oxides have a significant impact on the optical, electrical and electronic properties of the nanomaterials, and on the performance of DSSCs and enhancement of the rate of photocatalytic degradation in dye remediation. [ABSTRACT FROM AUTHOR]

The polyaniline/zinc oxide (PANI/ZnO) nanocomposites were prepared by in situ polymerization of aniline monomer with ZnO nanomaterials and applied as a photocatalyst for the degradation of methylene blue (MB) dye. The morphological observations elicited the agglomerations of PANI sheets which occurred due to the interaction between PANI and ZnO nanomaterials in PANI/ZnO nanocomposites. As compared to pristine PANI, the UV-vis spectra exhibited that the absorption peak of π- π* transitions considerably shifted to higher wavelength at 360 nm from 325 nm in the nanocomposites. The photocatalytic activity results indicated the substantial degradation of MB dye by ~76% over the surface of PANI/ZnO nanocomposite catalyst under light illumination. The PANI/ZnO nanocomposites showed three times higher photocatalytic activity to MB dye degradation compared to pristine PANI might due to high photogenerated electron (ē)-hole (h) pairs charge separation. [ABSTRACT FROM AUTHOR]

Binary dopant mixture of (ZrO2/AgI) (v/v) is prepared in different ratios to enhance the conductivity of the synthesized PANI. DC conductivity of (ZrO2/AgI) (v/v) doped PANI samples is measured in the temperature range (300‐400K). The calculated values of pre‐exponential factor (σ0) indicates that conduction is taking place through hopping process due to localized states present near the Fermi level. Structural changes due to interaction of dopant species with PANI are studied through FT‐IR and Photoluminescence characterization. Photoluminescence (PL) spectra of the doped samples occurred in the form of peaks and the intensities of these peaks vary according to the concentration of dopant mixture. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2682–2687, 2007 [ABSTRACT FROM AUTHOR]