Highly responsive carbon dioxide sensing by graphene/Al2O3 quantum dots composites at low operable temperature

Novel chemiresistive gas sensors based on graphene/Al2O3 quantum dots composites were fabricated and examined for carbon dioxide sensing. Composite samples with different wt% of graphene (20-80 wt%) mixing in constant 1 g Al2O3 were prepared and characterized by X-ray diffraction, transmission electron microscopy along with selected area electron diffraction, ultraviolet-visible spectroscopy, fluorescence spectroscopy and thermo gravimetric-differential thermal analysis. The experimental results showed that the graphene/Al2O3-based chemiresistor exhibited much higher sensing response and it enhanced linearly with addition of graphene. The gas sensing mechanism was discussed on the basis of defect chemistry through fluorescence measurements. 80 wt% graphene/Al2O3 composite exhibited good sensing response (10.84) at room temperature, low operating temperature (398 K), fast response time (14 s) and recovery time (22 s) along with good stability.