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Gold-silicon core-shell nanoparticles embedded in silica matrix, evident by transmission electron microscopy and x-ray photoelectron spectroscopy were synthesized by atom beam cosputtering followed by thermal annealing. Optical absorption studies revealed localized surface plasmon resonance (LSPR), which showed regular redshift from 500to583nm with increase in annealing temperature. The observed redshifts in the LSPR peaks are in close agreement with the theoretical calculations assuming Si nanoshells surrounding Au nanoparticles. The Au–Si core-shell formation is explained by Au–Si liquid nanodroplet formation at temperatures higher than the eutectic temperature, followed by phase separation during subsequent cooling.

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Gold–polymethylmethacrylate (PMMA) nanocomposites were fabricated with a photoreduction method using UV irradiation. The irradiated samples are compared with unirradiated ones to investigate the mechanism of gold nanoparticle formation and the effect of UV irradiation and polymer matrix on the morphology of the particles. The triangular gold nanoparticles were formed in polymer medium at a specific concentration of gold salt and UV exposure. The particle size decreased when the gold salt to polymer ratio was increased. The samples were analysed using UV–Vis spectroscopy, Fourier transform infrared spectrometry, atomic force microscopy, x-ray diffraction, small angle x-ray scattering and x-ray photoelectron spectroscopy. The interfacial interaction of Au nanoparticles and PMMA polymer has been discussed.

We report the effect of the variation of diameter on the optical, magnetic, and magnetodielectric properties of the Pr–Cr-codoped BiFeO3 (BFO) nanowires (NWs). Pr–Cr-codoped BFO NWs with different diameters (18, 35, 55, 100, 150, and 250 nm) have been fabricated by employing a simple wet chemical template-assisted route. The effect of quantum confinement has been found to have a significant influence on the room-temperature photoluminescence and Raman spectra of the NWs. An interesting blue shift in the band gap emission is observed in the photoluminescence spectra of the NWs as a result of quantum confinement. The position and the intensity of the Raman peaks are found to change significantly depending on the variation in the NW diameter. The room-temperature ferromagnetism of the codoped BFO NWs increases consistently with the decrease in the diameter of the NWs because of the suppression of the spiral spin structure and the increase in the number of uncompensated for spins at the NW surface (as the surface to volume ratio increases with the decrease in the NW diameter). Strong magnetoelectric coupling is evidenced in the codoped BFO NWs with the decrease in the NW diameter. The tuning of the optical, magnetic, and magnetodielectric properties of the doped BFO NWs appears to be very promising for achieving multifunctionality in a single material.

Dose dependent structural modifications in Si(100) due to 1.5 MeV implantation of Sb have been characterized using Raman spectroscopy and Rutherford backscattering spectrometry/channeling (RBS/C) techniques. With increasing fluence, an intensity reduction of the first order Raman peak, characteristic of crystalline Si, is observed. The amorphicity in Si lattice appears at a dose of 1×1013 ions/cm2 and it increases with each dose. For a dose of 5×1014 ions/cm2 the Raman spectrum resembles that of amorphous Si. RBS/C studies also support a fully amorphized lattice at this dose though for smaller doses it suggests lower disorder. For the fluences of 1×1013 and 1×1014 ions/cm2 a coexistence of undamaged crystalline Si regions and amorphous zones is observed. Consequently, phonon confinement is observed. Lattice recovery achieved by subsequent annealing has also been investigated using Raman spectroscopy. By annealing at 600 °C, sample crystallinity is fully recovered in all the cases up to the fluence of 5×1014 ions/cm2. For higher doses small amorphicity still remains. Depth dependent measurements of the shifts in the Raman peaks demonstrate a gradient in stress which is of compressive nature near the surface region but is tensile in deeper layers. Maximum stress in the lattice appears for a dose of 1×1012 ions/cm2 which gets relaxed by the incorporation of amorphous zones at higher fluences.