Micro Ring Resonator based CO2 Gas Sensor using PbSe Quantum Dots

In this paper, we introduce a micro-ring resonator-based highly sensitive carbon dioxide sensor. For this purpose, a valley is created in the core of the ring and PbSe quantum dots (QDs) are deposited in the valley and the sensor is exposed to CO2 gas. In this way, the refractive index of the PbSe QDs increases with an increase in the concentration of gas flow, and then the resonance frequency of the ring resonator shifts. The designed sensor operates almost linearly over a wide range of concentrations for CO2 gas and shows a high resonance shift at different concentrations of CO2 gas. The detection limit for the designed sensor is 0.001% of CO2 gas which is more sensitive than previously reported sensors based on microring resonators. The frequency shifts are investigated by changing the width of the valley. The minimum width of the valley was determined for the evanescent field in which only the outer core of the ring affects the resonant frequency. Also, the modal analysis of the designed ring resonator waveguide is investigated to determine the minimum core width.

A Highly Sensitive Room Temperature CO2 Gas Sensor Based on SnO2-rGO Hybrid Composite

A tin oxide (SnO2) and reduced graphene oxide (rGO) hybrid composite gas sensor for high-performance carbon dioxide (CO2) gas detection at room temperature was studied. Since it can be used independently from a heater, it emerges as a promising candidate for reducing the complexity of device circuitry, packaging size, and fabrication cost; furthermore, it favors integration into portable devices with a low energy density battery. In this study, SnO2-rGO was prepared via an in-situ chemical reduction route. Dedicated material characterization techniques including field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) were conducted. The gas sensor based on the synthesized hybrid composite was successfully tested over a wide range of carbon dioxide concentrations where it exhibited excellent response magnitudes, good linearity, and low detection limit. The synergistic effect can explain the obtained hybrid gas sensor’s prominent sensing properties between SnO2 and rGO that provide excellent charge transport capability and an abundance of sensing sites.