M Parthibavarman, B Renganathan, D Sastikumar – Current Applied Physics, 2013
We have successfully synthesized Co doped SnO2 nanoparticles by a simple microwave irradiation technique. Powder X-ray diffraction results reveal that the SnO2 doped with cobalt concentration from 0 to 5 wt% crystallizes in tetragonal rutile-type structure. The products were annealed at 600°C for 5 hrs in ambient atmosphere in order to improve crystallinity and structural perfection. Transmission electron microscopy (TEM) studies illustrate that both the undoped and Co doped SnO2 crystallites form in spherical shapes with an average diameter of 30 – 15 nm, which is in good agreement with the average crystallite sizes calculated by Scherrer’s formula. A considerable red shift in the absorbing band edge was observed with increasing of Co content (0-5 wt %) by using UV-Vis diffuse reflectance spectroscopy (DRS). Oxygen-vacancies, tin interstitial and structural defects were analyzed using photoluminescence (PL) spectroscopy. Electron paramagnetic resonance (EPR) spectroscopic studies clearly showed that the Co2+ was incorporated in to the SnO2 host lattice. Ethanol gas sensitivity of pure and Co-doped (5 wt%) SnO2 nanoparticles were experimented at ambient temperature using optical fiber based on clad-modified method. By modifying the clad exposure to ethanol vapor, the sensitivities were estimated to be 18 and 30 counts/100 ppm for undoped and Co-doped SnO2 nanoparticles, respectively. These results show that the Co doping into SnO2 enhances its ethanol gas sensitivity significantly… It consists of a white light source (Model SL1, Stellar Net Inc., USA) with emission wavelengths from 100 to 2000 nm and a miniature fiber optic spectrometer (EPP-2000, Stellar Net Inc., USA) with spectral response from 100 to 1100 nm…
Fig. 3. UV-Vis DRS of SnO2 with different Co content (a) reflectance spectra (b) Kubelka-Munk model (as prepared samples) (c) reflectance spectra (d) Kubelka-Munk model (annealed samples).
Fig. 4. Photoluminescence spectra of SnO2 with different Co content (a) pure SnO2 (b) Co 0.5 wt % (c) Co 3% (d) Co 5 wt% (annealed samples).
Ø Fig. 7. Spectral response of ethanol gas sensor for pure SnO2 nanoparticles at room temperature.
Ø Fig. 8. Spectral response of ethanol gas sensor for Co (5 wt %) doped SnO2 nanoparticles at room temperature
