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Zinc Oxide (ZnO) nanoparticles exhibit a wide range of applications owing to their unique properties such as low cost, non-toxicity, abundance in nature and suitability for doping. In the present study, ZnO and Aluminium doped Zinc Oxide (Al-ZnO) nanoparticle thin films were prepared on FTO glass substrate by sol-gel and spin coating methods. The structural and morphological characteristics of the undoped and Al-doped ZnO nanoparticles were examined by X-ray Diffraction (XRD) and High Scanning Electron Microscope (HR-SEM) analysis, respectively. The XRD studies revealed the hexagonal wurtzite structure of the as-synthesized ZnO samples and the crystallite size was estimated using Scherrer’s formula to be 28 and 30 nm respectively, in the case of the undoped and doped ZnO nanoparticles. The average particle sizes in nanoscale were analysed using FESEM and found to be 38 nm and 42 nm for the bare and doped samples. The surface area of the as-synthesised particles were correspondingly estimated as 46 m2/g and 25 m2/g and their relative pore volume and diameter were determined using BET analysis. The field dependent photoconductivity of Al-ZnO shows a significant increase as against the bare ZnO.

We present a detailed examination on the microstructural, structural, optical and electrical properties of one dimensional (1D) and three dimensional (3D) titania nanostructures in comparison with zero dimensional (0D) titania nanoparticles. Material characterization by X-ray Diffraction technique confirms the formation of anatase phased TiO2 nanoparticles and rutile phased nanorods and nanoflowers. Morphological investigations were done with Field Emission Scanning Electron Microscopy and High Resolution Transmission Electron Microscopy. Optical properties of the samples were studied using UV-Visible Diffuse Reflectance Spectroscopy and their optical band gap energies were calculated using Kubelka-Monk method. Although the 1D nanorods possess faster electron transport than the nanoparticle structure, their low surface area has detained that morphology to absorb more incident radiation. However, the 3D nanoflower morphology coupled with excellent light scattering capability and enhanced optical absorption resulted in a 7 fold increase in dark and 26 fold increase in photocurrents compared to nanorod and nanoparticles. Dye Sensitized Solar Cells (DSSCs) are developed using Safranine O dye and their I-V characteristics were examined. Improved performance of DSSC is observed in the case 3D nanoflower structures delivering efficiency of about 3.56 %. The findings of this work essentially suggest that the optical transport properties of the photoanode materials and therefore cell performances are significantly influenced by their respective morphologies.

A comparative investigation of SnO2/SiO2 nanocomposite with SnO2 nanoparticles has been conducted in the present study with the intent of learning the probable enhancement of the properties of the nanocomposite over those of the bare nanoparticles which has not been widely reported before. SnO2 nanoparticles and SnO2/SiO2 nanocomposite have been synthesized via the facile and versatile sol-gel method. The samples were characterized with X-Ray Diffraction (XRD), High Resolution Scanning Electron Microscopy (HRSEM), Brunauer Emmett Teller (BET) studies, Fourier Transform Infra-Red spectroscopy (FT-IR), UV–Visible (UV–Vis) spectroscopy and Field-dependent photo conductivity technique for the evaluation of their crystallite size, structure & morphology, surface, chemical, optical and electrical properties respectively. Scherrer’s equation was used to determine the crystallite size of the as-synthesized samples from the XRD data. The particle size of SnO2/SiO2 nanocomposite as observed through HRSEM was found to be reduced when compared with the bare SnO2 nanoparticles suggesting a possible increase in the optical band gap of the former which has been further confirmed in the optical studies. The surface area of SnO2/SiO2 nanocomposite revealed a remarkable enrichment by approximately 5 folds in comparison with that of SnO2 nanoparticles which suggests an enhancement in its corresponding optical and electrical properties. The SnO2/SiO2 nanocomposite recorded appreciated values of field-dependent photo and dark currents with several folds of augmentation thereby qualifying as an efficient photoconducting material. Attributed with an improved surface area and increased photoconducting nature, the SnO2/SiO2 nanocomposite could be presented as an excellent photoanode material for nanomaterials based Dye Sensitized Solar Cells (DSSCs).

Highly proficient Titania heterostructures were successfully developed on Fluorine-doped Tin Oxide (FTO) substrate through the facile single step hydrothermal method where 18 h of autoclaving period resulted in the formation of nanorods with a scanty topping of nanoflowers. Further, plasmon impregnation (SnO2-Ag) into the Titania heterostructures by spin coating technique yielded bilayer nanocomposite (TiO2/SnO2-Ag) films. Substantial enhancement in absorption intensity was evidenced with a slight red shift in the case of bilayer nanocomposite owing to the incorporation of the noble metal. An appreciable increase in dark and photo current was observed in both the Titania heterostructure and bilayer composite films suggesting the possibility of their application in Dye Sensitized Solar Cells (DSSCs) while the plasmon impregnated bilayer composite exhibited significantly enhanced photoconductivity than the former.

We report a comparative investigation of the characteristics of modified TiO2 nanorods grown on conducting indium tin oxide glass (ITO) substrates by two different hydrothermal methods: the direct method by which rutile TiO2 nanorods were grown directly on plain ITO substrates and the seed-mediated one using which a thin film of anatase TiO2 seed layer was laid down by spin coating and annealing prior to the growth of TiO2 nanorods on it. Microstructural analysis of the samples using X-ray diffraction confirmed their rutile nature. The average crystallite size estimated using Scherrer’s formula was found to fall in the range of 11–17 nm in both cases. Field emission scanning electron microscopy revealed the nanorod morphologies of a dandelion arrangement in the case of directly grown ones and a proper vertical orientation in the case of the seed-mediated method. UV–Vis spectroscopy analysis of both the samples exhibited redshifts with intense absorption of visible radiation, and the seed-mediated one was found to possess an increased bandgap. The transport nature of the samples was characterized by significant increase in both dark and photocurrents. The results show that the dark and photocurrent values of the directly grown TiO2 nanorods were greater than those of the seed-mediated ones by ~seven and five folds, respectively, and therefore, it could serve as efficient photoelectrodes in dye-sensitized solar cells.