Heterojunctions of rGO/Metal Oxide Nanocomposites as Promising Gas-Sensing Materials—A Review

Abstract

Monitoring environmental hazards and pollution control is vital for the detection of harmful toxic gases from industrial activities and natural processes in the environment, such as nitrogen dioxide (NO2), ammonia (NH3), hydrogen (H2), hydrogen sulfide (H2S), carbon dioxide (CO2), and sulfur dioxide (SO2). This is to ensure the preservation of public health and promote workplace safety. Graphene and its derivatives, especially reduced graphene oxide (rGO), have been designated as ideal materials in gas-sensing devices as their electronic properties highly influence the potential to adsorb specified toxic gas molecules. Despite its exceptional sensitivity at low gas concentrations, the sensor selectivity of pristine graphene is relatively weak, which limits its utility in many practical gas sensor applications. In view of this, the hybridization technique through heterojunction configurations of rGO with metal oxides has been explored, which showed promising improvement and a synergistic effect on the gas-sensing capacity, particularly at room temperature sensitivity and selectivity, even at low concentrations of the target gas. The unique features of graphene as a preferential gas sensor material are first highlighted, followed by a brief discussion on the basic working mechanism, fabrication, and performance of hybridized rGO/metal oxide-based gas sensors for various toxic gases, including NO2, NH3, H2, H2S, CO2, and SO2. The challenges and prospects of the graphene/metal oxide-based based gas sensors are presented at the end of the review.

Surface-Oxidised Carbon Nanofibre-Based Nanofluids: Structural, Morphological, Stability and Thermal Properties

“…Known as mixed sedimentation, this phenomenon occurs when larger agglomerates settled down faster compared to smaller ones [ 29 ]. The findings could also be associated with the higher attractive van der Waals forces especially occurred between the carbon-based nanoparticles [ 30 ]. In contrast, the sedimentation was unclear at 0.5, 0.6, and 0.7 wt.%, while the 0.4 and 1.0 wt.% remained clear without sedimentation after 100 h. The observation could be attributed to the presence of hydroxyl bonds in the commercial CNFs, as evidenced by the FTIR spectra.…”

Solution-Processed Functionalized Graphene Film Prepared by Vacuum Filtration for Flexible NO2 Sensors

“…Moreover, the functionalization not only improves sensitivity but also may enhance selectivity toward specific gases even at room temperature. A wide variety of functional groups have been used, including polymers [ 18 , 19 , 20 ], metal oxides [ 21 , 22 ], metal nanoparticles [ 23 ], and small organic molecules [ 24 , 25 ]. Metalloporphyrins (MPor) and metallophthalocyanines (MPhc), as functional molecules, have attracted considerable interest due to their planar structure with metal atoms (Co, Fe, Zn, Ni, etc.)…”

Sensitive electrochemical biosensor for bisphenol A based on laccase immobilized on polypyrrole‐3‐carboxylic/Sb2O5/reduced graphene oxide hybrid nanomaterial

“…Sb 2 O 5 /reduced graphene oxide hybrid nanomaterial presents excellent electrocatalytic response [16] due to the combination of forms of graphene and metallic oxide to result in hybrid nanomaterial formation with distinct properties compared to isolated materials due to excellent thermal, mechanical, and electronic properties [17][18][19][20] of graphene species with acidic sites by Bronsted and Lewis, in addition to surface defects of Sb 2 O 5 favoring the development of electrochemical biosensors [21][22][23].…”