Design of ZnO/N-Doped Graphene Nanohybrid Incorporated RF Complementary Split Ring Resonator Sensor for Ammonia Gas Detection

The integration of nanomaterials with the microwave technology is a significant step toward the development of low-cost and low-power RF gas sensors. But, the issues associated with materials like insignificant surface area and poor conductivity, are barriers for the rapid detection of wide range of gas concentrations. In this paper, we demonstrate the proof-of concept using an RF complementary split ring resonator (CSRR) integrated ZnO/N-doped graphene (NGN) nano-hybrid to study the gas sensing properties. This RF device senses the presence of ammonia based on the change in the electrical conductivity of the nanohybrid material upon gas exposure. For this, we have designed and fabricated various new CSRR structures, namely, the meander (M-CSRR) and the CSRR, with the concentric-etched square pattern (SP-CSRR) other than the conventional CSRR (C-CSRR). The fabricated CSRRs are coated with the solvothermal methodically prepared ZnO/NGN nanomaterials and a comparison among them is also made. The comparison revealed that the SP-CSRR coated ZnO/NGN sensor had the maximum shift in the S21 resonance frequency (Δf
_S21
= 13 MHz at 100 ppm) among all at room temperature. Furthermore, the SP-CSRR-ZnO/NGN sensor exhibited a large-S21 frequency shift of 133 MHz for 500 ppm of ammonia and has shown excellent reproducibility with 0.05% of variation. We have also projected the plausible sensing mechanism for this RF sensing device.