ZnSe:Cu@ZnS core/shell quantum dots synthesis by photochemical method for ethanol gas sensing

Abstract

In the present study, ZnSe, ZnSe:Cu and ZnSe:Cu@ZnS core/shell quantum dots (QDs) were synthesized at room temperature using the new and fast microwave-assisted photochemical approach recently reported by the authors. Gas sensors based on these QDs were made and their sensitivity was studied in response to different flows of ethanol gas. Morphology and elemental analyses (conducted via FESEM, TEM, EDS and Map) were performed alongside XRD line profile analysis using Halder-Wagner approach. TEM results showed that the synthesized QDs exhibited spherical morphology of particles with an average size of approximately 20 nm, except for ZnSe:Cu(1.5 %)@ZnS (including nanorods). Ethanol gas sensing measurements were conducted under ambient conditions. Coating the Cu (1.5 mol%)-doped cores with ZnS increased the sensitivity, while the undoped samples exhibited the opposite trend. Among the fabricated sensors, the most sensitive one was made of ZnSe without microwave irradiation (MWIR), although it lacked desired stability. Meanwhile, ZnSe:Cu(1.5 %)@ZnS nanorods were identified as the most sensitive (optimal) sample, demonstrating favorable stability. Consequently, the gas sensitivity of the optimal sample to various ethanol gas flow rates was tested. It was observed that gas sensitivity increased with increasing flow rate up to 150 ml/min and decreased somewhat at higher flow rates.