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Cadmium sulfide nanoflowers (CdS-NF), nanorods (CdS-NR), and its nanocomposites with polyaniline (PANI) were successfully synthesized using facile chemical methods. Transmission electron microscopy (TEM) images confirmed the growth of CdS as nanoflowers and nanorods. High-resolution transmission electron microscopy (HRTEM) images showed clear lattice fringes, indicating good crystallinity of the CdS nanostructures and the formation of interface between PANI and CdS. The photocatalytic activity of CdS nanostructures and its composites was demonstrated for the degradation of methylene blue (MB) dye under visible light irradiation. The PANI/CdS nanocomposites showed enhancement in the photocatalytic activity as compared to bare CdS nanostructures, and it is attributed to efficient charge transfer between CdS and PANI. Photoluminescence study confirmed the enhancement in photogenerated electron-hole pairs separation in CdS nanostructures after the addition of PANI. The composite of PANI with CdS-NF exhibited larger improvement in the photodegradation efficiency over CdS-NF as compared to the improvement observed in PANI/CdS-NR over CdS-NR, which is attributed to the formation of more interfacial sites between PANI and CdS nanoflowers as compared to PANI and CdS nanorods. Our present work indicates that by carefully designing the semiconductor nanomaterial composites, the photocatalytic activity can be significantly enhanced. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO), an insulating analogue to highly conducting graphene, is considered as a chemically tunable platform for optoelectronic applications. However, to be useful for such applications, detailed analysis of its optical properties with a controlled degree of de-oxidation need to be investigated. In this report, we investigated the optical behaviour of GO and chemically reduced GO (with different degrees of de-oxidation, termed as RGO-5 and RGO-10) deposited onto SiO2/Si substrates, using variable angle spectroscopic ellipsometry. GO and its chemically tuned derivatives (RGO-5 & RGO-10) have been synthesized using Hummer’s method and by its corresponding reduction using different concentrations (5 and 10 ml) of reducing agent, respectively. Optical properties such as bandgap, the refractive index, the extinction coefficient, and complex dielectric behaviour over the wavelength region 250-1650 nm have been investigated. The optical bandgap is found to reduce systematically from 3.25 eV for GO to 2.78 and 1.81 eV for RGO-5 and RGO-10 samples, respectively. Whereas, the dielectric behaviour of RGO-5 sample found to be better with a lower value of extinction coefficient as compared to GO and RGO-10 samples. [ABSTRACT FROM AUTHOR]

Three sets of single domain CoFe2O4 nanoparticles of similar sizes (~ 10 nm) with different values of intrinsic strain have been synthesized at three different growth temperatures (120, 140 and 160 °C). The optical bandgap and saturation magnetization of these similar size magnetic nanoparticles are found to be strongly dependent upon the intrinsic strain present in the nanoparticles. The optical bandgap is found to decrease from 1.84 to 1.67 eV and the saturation magnetization decreases from 66.7 to 35.1 emu/g with increase in the intrinsic strain in the nanoparticles. The presence of intrinsic strain is found to affect the cationic redistribution at the tetrahedral and the octahedral sites of the nanoparticles. The decrease in the optical bandgap of CoFe2O4 nanoparticles with increase in the intrinsic strain is correlated to the presence of more Co2+ at the tetrahedral sites. The change in the saturation magnetization is also correlated to the increase in the population of Co2+ at the tetrahedral sites with increase in the intrinsic strain resulting in an enhanced spin canting at the octahedral sites. [ABSTRACT FROM AUTHOR]