The SiO 2 -Fe 3 O 4 core-shell nanostructures were synthesized by sol-gel chemistry. The morphological features of the nanostructures were examined by field emission scanning electron microscopy which revealed the core-shell nature of the nanoparticles. X-ray diffraction studies evidenced the formation of SiO 2 -Fe 3 O 4 core-shell nanostructures with high degree of homogeneity. The elemental composition of the SiO 2 -Fe 3 O 4 core-shell nanostructures was determined by energy-dispersive X-ray spectroscopy analysis. Fourier transform infrared spectroscopy showed the Si-O-Fe stretching vibrations. On analysis of the optical properties with UV-Vis spectra and Tauc's plot, it was found that the band gap of SiO 2 -Fe 3 O 4 core-shell nanostructures diminished to 1.5 eV. Investigation of the electrical properties of the core-shell nanostructures using field-dependent conductivity measurements presented a significant increase in photoconductivity as compared to those of its single components, thereby rendering them as promising candidates for application as photoelectrodes in dye-sensitized solar cells.

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We report a comparative investigation of the characteristics of modified TiO 2 nanorods grown on conducting indium tin oxide glass (ITO) substrates by two different hydrothermal methods: the direct method by which rutile TiO 2 nanorods were grown directly on plain ITO substrates and the seed-mediated one using which a thin film of anatase TiO 2 seed layer was laid down by spin coating and annealing prior to the growth of TiO 2 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 TiO 2 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.

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