Jayaprakash Khanderi

Synthesis and sensoric response of ZnO decorated carbon nanotubes

ZnO nanoparticles of size 2–10 nm were generated in situ from the single source precursor [2-(methoxyimino)propanoato]zinc(II), ([CH3ONCCH3COO]2Zn·2H2O) onto multiwalled carbon nanotubes (MWCNTs) at low temperature (150 °C). The degree of ZnO coverage on the MWCNTs can be tuned and is dependent upon the ZnO precursor concentration. A plausible growth mechanism based on surface saturation of as-deposited precursor on the MWCNTs has been proposed. The X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) indicate the nano-crystalline nature of the ZnO particles. Scanning electron microscopy (SEM) and TEM investigations of the ZnO deposition revealed a dense and homogeneous deposition along the complete periphery of the MWCNT. The ZnO/MWCNT nanocomposite hybrid materials were further electronically characterized by micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectroscopy (UV-Vis) as well as room temperature photoluminescence (PL). The nanostructured ZnO/MWCNT composite shows a better sensing performance when compared to bare MWCNTs in the detection of low CO levels (20–200 ppm).

Binary Au/MWCNT and Ternary Au/ZnO/MWCNT Nanocomposites: Synthesis, Characterisation and Catalytic Performance

Gold nanoparticles of 10-24 and 5-8 nm in size were obtained by chemical citrate reduction and UV photoreduction, respectively, on acid-treated multiwalled carbon nanotubes (MWCNTs) and on ZnO/MWCNT composites. The shape and size of the deposited Au nanoparticles were found to be dependent upon the synthetic method used. Single-crystalline, hexagonal gold particles were produced in the case of UV photoreduction on ZnO/MWCNT, whereas spherical Au particles were deposited on MWCNT when the chemical citrate reduction method was used. In the UV photoreduction route, n-doped ZnO serves as the e(-) donor, whereas the solvent is the hole trap. All materials were fully characterised by UV/Vis spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and BET surface analysis. The catalytic activity of the composites was studied for the selective hydrogenation of alpha,beta-unsaturated carbonyl compound 3,7-dimethyl-2,6-octadienal (citral). The Au/ZnO/MWCNT composite favours the formation of unsaturated alcohols (selectivity=50% at a citral conversion of 20%) due to the presence of single-crystalline, hexagonal gold particles, whereas saturated aldehyde formation is favoured in the case of the Au/MWCNT nanocomposite that contains spherical gold particles.

A molecular approach to Cu doped ZnO nanorods with tunable dopant content

A novel molecular approach to the synthesis of polycrystalline Cu-doped ZnO rod-like nanostructures with variable concentrations of introduced copper ions in ZnO host matrix is presented. Spectroscopic (PLS, variable temperature XRD, XPS, ELNES, HERFD) and microscopic (HRTEM) analysis methods reveal the +II oxidation state of the lattice incorporated Cu ions. Photoluminescence spectra show a systematic narrowing (tuning) of the band gap depending on the amount of Cu(II) doping. The advantage of the template assembly of doped ZnO nanorods is that it offers general access to doped oxide structures under moderate thermal conditions. The doping content of the host structure can be individually tuned by the stoichiometric ratio of the molecular precursor complex of the host metal oxide and the molecular precursor complex of the dopant, Di-aquo-bis[2-(methoxyimino)-propanoato]zinc(II) 1 and -copper(II) 2. Moreover, these keto-dioximato complexes are accessible for a number of transition metal and lanthanide elements, thus allowing this synthetic approach to be expanded into a variety of doped 1D metal oxide structures.