Synthesis and optical-electrochemical gas sensing applications of Ni-doped LiFePO4 nano-particles

Ni-doped LiFePO4 particles synthesized with high purity by a one-step hydrothermal method were used for xylene detection in a self-assembled optical waveguide (OWG) and WS-30A electro-chemical gas sensors. The optical waveguide was fabricated by spin-coating a thin film of LiFe0.995Ni0.005PO4 on the surface of tin-diffused glass. Upon exposing the sensor to xylene gas, a significant change in the output light intensity was observed due to variations in the refractive index, thickness, and absorption coefficient of the film. For a range of xylene concentrations from 10 ppb to 1000 ppm, the sensor showed fast response and recovery times in addition to good reversibility and repeatability. Other substances, when present in concentrations less than 1 ppm, did not interfere with the detection of xylene gas. However, at room temperature, the LiFe0.995Ni0.005PO4 sensing film, when measured by WS-30A electro-chemical gas sensing apparatus, detected a small response (resistance change) to 100 ppm of xylene. The trends of output light changes were consistent with the changes in resistance.