Sitakshi Gupta; Chhaya Ravikant
Abstract
Nowadays, gas sensors are fast becoming an imperative part of modern life with extensive applications in domestic safety, environmental monitoring, industrial process control, public security, medical applications and chemical warfare assessment amongst many others. The detection of minor gas leaks has ...
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Nowadays, gas sensors are fast becoming an imperative part of modern life with extensive applications in domestic safety, environmental monitoring, industrial process control, public security, medical applications and chemical warfare assessment amongst many others. The detection of minor gas leaks has been a challenging area of research, particularly in view of the hazards to human health and safety posed by toxic gases like NO2, NO, CO, NH3 etc and combustible gases like methane, hydrogen gas and some volatile organic compounds. Thus it is imperative to evolve and employ simple yet reliable gas sensing mechanisms with optimum response and selectivity towards even low concentration of analyte gas at room temperature. Most of the conventional gas sensors are based on metal-oxide semiconductors which are low-cost, exhibit good sensitivity and fast response/recovery. Zinc oxide is one such n-type semiconducting oxide, which has been widely studied for gas sensing response due to its ease of fabrication, high sensitivity and environment-friendly nature. However, the operating temperature of such sensors is usually high (>200°C) owing to the wide band-gap (3.37 eV) and high electrical resistance (kΩ-MΩ), which limits their practical utilization. In order to be used in hazard monitoring and home/workplace safety, the gas sensors need to be sensitive to gas exposure in mild operating conditions. As an alternative, more recently, graphene and its derivatives like pristine graphene (PG), reduced graphene oxide (rGO) etc. have been studied for sensing applications owing to their exceptional electronic and physical properties such as high carrier mobility at room temperature, good thermal stability, high mechanical strength, ballistic conductivity and large specific surface area. These sensors show high sensitivity at low operating temperatures (down to room temperature) towards low concentrations of analyte gas. However most of these rGO based sensors exhibit relatively longer response/recovery times than metal-oxide based gas sensors. Hence, nanocomposites formed by hybridizing graphene or its derivatives with metal-oxide nanoparticles are being explored as gas sensing materials. Combining reduced graphene oxide with zinc oxide to form hybrid nanostructures is particularly interesting because not only do they display the individual properties of the metal oxide NPs (faster response/recovery times) and of graphene (high electronic conductivity leading to efficient room temperature gas response), but may also have synergistic effects leading to better sensitivity as a gas sensing material. Here we present a review of the recent progress in rGO-ZnO nanocomposites based gas sensors. Copyright © 2018 VBRI Press.
E. Murugan; K Kalpana
Abstract
Graphene functionalized with Poly(amidoamine) dendrimer stabilized PdNPs (r-GO-PAMAM-Pd) composite was prepared through facile experimental routes and characterized by FT-IR, XRD, Raman, SEM and EDAX techniques. Initially, poly(amidoamine) generation 3 (PAMAM (G3)) dendrimer was functionalized on graphene ...
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Graphene functionalized with Poly(amidoamine) dendrimer stabilized PdNPs (r-GO-PAMAM-Pd) composite was prepared through facile experimental routes and characterized by FT-IR, XRD, Raman, SEM and EDAX techniques. Initially, poly(amidoamine) generation 3 (PAMAM (G3)) dendrimer was functionalized on graphene oxide (GO) and the resulting matrix was loaded with PdNPs through stabilization and thus produced excellent conducting composite material. The electro-catalytic activity of this composite was inspected by coating on bare GCE and thus produced stable and efficient GC-r-GO-PAMAM (G3)-Pd electrode and this in turn demonstrated for the oxidation of formic acid (FA). The occurrence of the oxidation reaction was monitored by cyclic voltammetric (CV) and linear sweep voltammetric (LSV) techniques in 0.5 M H2SO4 medium at the potential window of -0.3 to 1.0 V vs. Ag/AgCl, v = 50 mVs-1. The observed peak potential for the new electrode was located at 0.15V and compared with existing electrodes derived from different GO/Pd composites.The comparative results reveals that the newly designed electrode shown an excellent catalytic activity, more resistant to the surface poisoning and the anodic onset potential was more negative than the reported electrodes. This improved electro-catalytic performance are due to the contribution of synergetic effect of GO, dendrimer and PdNPs. Copyright © 2018 VBRI Press.
