Ramasamy Srinivasan

Gas‐Sensing Properties of Needle‐Shaped Ni‐Doped SnO2 Nanocrystals Prepared by a Simple Sol–Gel Chemical Precipitation Method

The preparation of needle-shaped SnO(2) nanocrystals doped with different concentration of nickel by a simple sol-gel chemical precipitation method is demonstrated. By varying the Ni-dopant concentration from 0 to 5 wt%, the phase purity and morphology of the SnO(2) nanocrystals are significantly changed. Powder XRD results reveal that the SnO(2) doped with a nickel concentration of up to 1 wt% shows a single crystalline tetragonal rutile phase, whereas a slight change in the crystallite structure is observed for samples with nickel above 1wt%. High resolution scanning electron microscopy (HRSEM) results reveal the change in morphology of the materials from spherical, for SnO(2), to very fine needle-like nanocrystals, for Ni-doped SnO(2), annealed at different temperatures. The gas sensing properties of the SnO(2) nanocrystals are significantly enhanced after the nickel doping.

ESTIMATION OF LATTICE STRAIN, STRESS, ENERGY DENSITY AND CRYSTALLITE SIZE OF THE SPHERICAL YTTRIUM OXIDE NANOPARTICLES

Yttria nanoparticles are synthesized by co-precipitation method and as-prepared nanoparticles are annealed at various temperatures. The as-prepared and annealed particles are characterized by X-ray diffraction and transmission electron microscope (TEM). Here we estimated the lattice strain, crystallite size, deformation stress, and deformation energy density for annealed (800°C) yttrium oxide nanoparticles by Williamson-Hall-Isotropic Strain Model (W-H-ISM), W-H-Anisotropic Strain Model (W-H-ASM) and W-H-Energy Density Model (W-H-EDM) based on W-H plot from powder X-ray diffraction data. The shape and size of the nanoparticles are determined using TEM. The results of the estimated crystallite size of yttria nanoparticles by various methods agreed with the TEM results.

STRUCTURAL AND OPTICAL PROPERTIES OF Eu3+ DOPED CERIUM OXIDE NANOPHOSPHORS

Europium (3%) doped ceria nanoparticles were successfully prepared by 72 h hydrolysis assisted co-precipitation method. The average grain size of the as-prepared sample was 11 nm. The grain sizes were 12 and 18 nm for samples annealed at 500°C and 800°C respectively. The grain size effect on optical bandgap is investigated from diffuse reflectance spectroscopy (DRS). The orange and red color emissions of europium doped ceria nanoparticles were investigated by photoluminescence (PL) spectra under excitation of 330 nm. The high intense orange emission peak was found at 591 nm for as-prepared and annealed nanoparticles. This is the characteristic peak of the Eu3+ ion corresponding to the parity allowed magnetic dipole transition between the 5D0–7F1 states. Site occupancy of europium ions was estimated by Red (R)/Orange (O) intensity ratio using PL spectrum.

Nanocrystalline titanium dioxide coated optical fiber sensor for ammonia vapour detection

Fiber optic sensor is proposed based on cladding modification method for detecting ammonia emissions. Nanocrystalline titanium dioxide is used as a sensing material and spectral characteristics of the sensor are studied for different concentrations (50-500 ppm) of ammonia, methanol and ethanol. The sensor shows a linear variation in the output light intensity with the concentration. The light intensity increases for ammonia whereas it decreases for methanol and ethanol. Gas selectivity of the sensor is discussed.

Structural Characterization of Ceria Nanoparticles

Cerium oxide (Ceria) nanoparticles were successfully synthesized by hydrolysis assisted co‐precipitation method. As‐synthesized samples are annealed at 500 °C and 800 °C respectively. Crystalline nature of the sample is analyzed by X‐ray diffraction (XRD). The morphology of all the samples is investigated by transmission electron microscope (TEM) and scanning electron microscope (SEM). The average size of the nanoparticles varies between the 8 and 20 nm. Poly crystalline natures of the nanoparticles proved by selected are electron diffraction pattern (SAED). The grain size dependent absorption is demonstrated with UV‐vis spectra.