The effect of Co (cobalt) and In (indium) combinational doping on the structural and optical properties of ZnO nanoparticles

Abstract

The undoped ZnO nanoparticles, In or Co single doped ZnO nanoparticles and the In and Co combinational doped ZnO nanoparticles were synthesised through sol-gel technique. The samples were characterised using XRD, TEM, FTIR, Raman spectroscopy, UV-Vis, PL and also tested for the gas sensing applications. XRD patterns revealed that the synthesised samples were of ZnO hexagonal wurtzite structure. The lattice parameters and the bond length of all the undoped and doped ZnO samples were determined and found to be similar to that of the Bulk ZnO. The average particle size of the undoped and doped ZnO nanoparticles were calculated and found to reduce with an introduction of dopants while increasing with an increase in temperature. The strain of all the prepared samples were also determined and observed to be in an inverse relation to the particle size. TEM images showed that the synthesised samples were spherically shaped and that was in agreement with XRD results, while the EDS results showed that In and Co were successfully doped into the ZnO nanoparticles. Raman and FTIR spectroscopy indicated that the prepared samples were indeed ZnO nanoparticles which confirmed the XRD results. The UV-Vis results showed a red-shift in the energy band gap with an introduction of dopants and that was related to the reduction of the particle size, this results were consistent with the PL results. Gas sensing results showed that doping Co and In into the ZnO nanoparticles has an effect into ZnO properties. Combinational-doping of In and Co was found to increase the response to the gases CH4, CO, NH3 and H2 as compared to the undoped and singly doped ZnO nanoparticle sensors. The response\recovery time was found to be affected with introduction of In and Co. Improvements were also observed in the operating temperature and the selectivity of the single doped and co-doped ZnO nanoparticles towards different gases used in this study.