N.R. Panda

Studies on growth morphology, UV absorbance and luminescence properties of sulphur doped ZnO nanopowders synthesized by the application of ultrasound with varying input power

Sulphur doped ZnO nanopowders have been prepared by sonochemical method in continuous (CS) and pulsed (PS) modes. Precipitation time was found to vary with input power of applied ultrasound. X-ray diffraction studies show the formation hexagonal wurtzite phase of nano ZnO but variation in size, strain and lattice parameters was observed in the samples synthesized through CS and PS modes with different input power. Surface morphology of the samples changed significantly with input power of the pulse as observed from scanning electron microscopic results. Well defined and c-axis oriented nanorods and multipodes were observed with power setting of 187.5 W whereas in all other cases no definite morphology was observed. UV absorption studies show higher value of absorbance for ZnO:S. Further, the absorption band becomes sharp for the samples prepared with power setting of 225 W. PL spectra show several bands due to different transitions in the region of 400-780 nm which have been explained in the light of excitonic and defect induced transitions in ZnO.

Sonochemical synthesis of nitrogen doped ZnO nanorods: effect of anions on growth and optical properties

Sonochemical synthesis of nitrogen doped zinc oxide (ZnO:N) nanorods using acetate and nitrate of the starting materials is reported. X-ray diffraction studies reveal the formation of hexagonal wurtzite phase of ZnO in both the cases whereas the crystallite size is found to be greater in acetate route. Precursor dependent growth process is observed as the time period for precipitation is found to be different with different starting materials. Electron microscopic studies show the formation of rod like structures of ZnO and ZnO:N in both acetate and nitrate routes. But, high aspect ratio and uniformity in the morphology of ZnO:N nanorods is observed in acetate route. High resolution images and selected area diffraction patterns of ZnO:N illustrate the nanorods to be c-axis oriented in both the cases. But in nitrate medium, the growth along [0001] direction is affected due to the adsorption of NO3− ions onto polar Zn2+ surface leading to smaller length of the nanorods. FTIR studies also support these results showing the existence of sharp N–O symmetric stretching in ZnO:N in nitrate route. Photoluminescence (PL) measurements show red shift of excitonic emission band for ZnO in acetate route.

Microstructural and optical studies on sonochemically synthesized Cu doped ZnO nanoparticles

Copper doped ZnO nanoparticles were synthesized by sonochemical method varying the concentration of the impurity. Systematic investigations like X-ray diffraction (XRD) and Transmission electron microscopy (TEM) were carried out to understand the microstructural properties. The average particle sizes and all the crystallographic parameters were calculated from XRD results. This shows the formation of wurtzite phase of ZnO with average size of the particles as 53 nm and an increase of particle size with dopant concentration was also been observed. UV absorption and Fourier transformed infrared spectroscopy (FTIR) spectra revealed the absorption at wavelength < 370 nm with a remarkable red shift of absorption band and a linear decrease of transmittance with increase in doping concentrations respectively.

Facile synthesis and improved optical activity in ZnO nanocrystallites doped with coinage metals

We report the growth of well-oriented rod and flower-like nanostructures of ZnO doped with copper, gold and silver synthesized by sonochemical method. The nanostructures were grown in a nutrient solution made of zinc nitrate (Zn(NO3)2 · 6H2O) and ammonia at low temperature with varying the dopant. XRD, TEM, UV–VIS, photoluminescence and FTIR spectra were recorded to study the crystallinity, microstructure and optical properties of the samples. XRD results show the formation of hexagonal wurtzite phase of ZnO with changing lattice parameters with doping. Both direct and indirect evidences were obtained from the XRD pattern confirming the incorporation of the dopant. Enhanced UV absorbance and PL emissions for ZnO has been observed and the role of Cu, Ag and Au in altering these properties has been investigated. Shift in UV band and evolution of new visible emission bands in the Pl spectra have been explained on the basis of incorporation of impurity occupying different states in the band gap of ZnO.