N-Type TiO2-Based Reusable Sensor for Photon-Assisted Cd(II) Ion Detection

Exponential growth of industrialization has triggered the need of a cheap and reusable water quality monitoring system to maintain drinkable water standards. This present work demonstrates n-type hierarchical flower-like nanostructured TiO
₂
on p-Si/SiO
₂
substrate to fabricate compact photon-assisted resistive sensor for Cd(II) ions detection in wastewater. The sensor presented a maximum response of 2.2 times for 50 ppm Cd(II) ions with a fast response and recovery times of 3.5 and 3.8 s, respectively, under white light irradiation. The limit of detection was calculated as ~100 ppb. Reusability study showed a maximum recovery of ~95.45% after three wash cycles along with a high degree of selectivity toward Cd(II) ions over six other common heavy metal ion contaminants. A mathematical model has been put forward relating the surface potential of TiO
₂
and sensor response which depended highly on surface defects. The effect of light on sensor performance has also been expressed mathematically and its dependence on the heterogeneity of the sensing layer has been explained. Hence, the proposed sensor may be utilized for continuous water quality monitoring over its conventional counterparts in the market.