Graphene Decorated With P-Type And N-Type Semiconductors And Their Gas-Sensing Performance

The development of efficient gas sensor device with high sensitivity, good selectivity and stability multi-phases (in gaseous or in liquid phases) performance is necessary to satisfy future societal and environmental needs. Gas sensors based on some semiconducting metal oxides (especially p-type and n-type metal oxides) are one of the most attractive sensor systems. Meanwhile, as a surprised new carbon material, graphene and reduced graphene oxide (rGO) are expected to be applied in improving gas sensing performance.In this work, a two-steps (reflux and followed-up hydrothermal) strategy was designed for the synthesis of Co3O4-ZnO/rGO ternary composite. Specifically, the initial injection and subsequent evaporation of ammonia assisted the successfully anchoring of p-type Co3O4 as well as n-type ZnO on rGO sheets. Moreover, rGO sheets and PVP also optimize the morphology of this ternary composite.Preliminary functional tests for detection of vapor and aqueous benzaldehayde are achieved. Co3O4-ZnO/rGO shows enhanced character for vapor benzaldehayde (response value reach 6.6 towards 10 ppm of benzaldehayde in air), and also presents high sensitivity towards aqueous benzaldehayde (response index come to 7.98 μA·cm-2·mM-1 sensitivity). These outstanding properties of Co3O4-ZnO/rGO indicated promising sensing application of detecting target analyte in different phases.A one-step hydrothermal strategy is developed for the synthesis of CuO-ZnO/rGO ternary composite. Compositional, morphological and structural analyses demonstrate the successfully anchoring of nano-scale p-n junctions between CuO and ZnO nanoparticles on rGO sheets. The obtained CuO-ZnO/rGO ternary composite exhibits outstanding sensing properties to acetone (the gas response value reaches 9.4 towards 10 ppm of acetone). More significantly, the ternary composite presents weaker sensing performance to ethanol, showing superior performance for effectively distinguishing acetone and ethanol. These findings highlight beneficial synergistic effects originated from large numbers of valid p-n junctions of CuO-ZnO and superior substrate characteristics of rGO sheets.