Influence of metal (W, Pd)-doping on gas sensing properties of the NiO flower-like thin films for o-xylene detection

Undoped NiO, W-doped NiO and Pd-doped NiO nanoflowers were prepared by hydrothermal, or precipitation method using NiSO4, WCl6 and PdCl2 as precursor compounds. The characterizations and microstructural analyses were performed by powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray analysis (EDAX). Thin films of these materials were prepared and the gas adsorption properties of the prepared thin films were investigated towards o-xylene vapor. The influence of doping on o-xylene adsorption was studied. To this intent, thin films were deposited by dip-coating on quartz substrates and fixed onto the end of an optical fiber. This device worked in reflection mode, and transduction took place in the light that traveled through the core of the fiber. W-doped NiO exhibited superior performance to o-xylene compared to the other two samples. The response time, sensitivity and recovery time for undoped NiO, W-doped NiO and Pd-doped NiO thin films towards o-xylene were found as (∼50 s, 0.08 and ∼5 min), (∼35 s, 0.19 and ∼1 min), and (∼20 s, 0.10 and ∼3 min), respectively. Other volatile organic compounds such as benzene, toluene, ethanol, methanol and acetone vapors were also tested by W-doped NiO and the sensitivity order was o-xylene > toluene > benzene > acetone > ethanol > methanol.