Abstract
Ammonia (NH3) is a widely used industrial gas that poses serious risks to human health and the environment even at low concentrations, necessitating the development of reliable and sensitive detection systems. In this study, Gd/SiO2 thin films were fabricated via DC magnetron sputtering and investigated as electrochemical sensing materials for room-temperature NH3 detection. The films were comprehensively characterized by XRD, SEM-EDX, and XPS to assess their structural, morphological, and chemical properties. The results revealed a homogeneous nanogranular morphology and a uniform distribution of oxidized gadolinium species on the SiO2 substrate. The sensing performance was evaluated by chronoamperometry at a constant applied potential. The Gd/SiO2 sensor exhibited a stable and reproducible current response over an NH3 concentration range of 1–60 ppm, with two distinct linear regions. This behavior may be attributed to a change in the sensing mechanism with increasing NH3 concentration, likely related to the progressive occupation and partial saturation of active adsorption sites, as well as to modifications in surface reaction kinetics. The calculated sensitivities were 0.0179 µA ppm?¹ (1–15 ppm) and 0.0405 µA ppm?¹ (15–60 ppm), with a low limit of detection of 0.34 ppm. The improved sensing performance is attributed to enhanced surface reactivity, increased oxygen vacancy concentration, and more efficient charge transfer processes induced by Gd incorporation.
