Investigation of Microstructure Effect on NO₂ Sensors Based on SnO₂ Nanoparticles/Reduced Graphene Oxide Hybrids

Abstract

The microstructures of metal oxide-modified reduced graphene oxide (RGO) are expected to significantly affect room-temperature (RT) gas sensing properties, where the microstructures are dependent on the synthesis methods. Herein, we demonstrate the effect of microstructures on RT NO2 sensing properties by taking typical SnO2 nanoparticles (NPs) embellished RGO (SnO2 NPs-RGO) hybrids as examples. The samples were synthesized by growing SnO2 NPs on RGO through hydrothermal reduction (SnO2 NPs-RGO-PR), which display the advantages such as high reactivity of the SnO2 surface with NO2, more oxygen vacancies (OV) and chemisorbed oxygen (OC), close contact between SnO2 NPs and RGO, and large surface area, compared to the samples prepared by one-pot hydrothermal synthesis from Sn4+ and GO (SnO2 NPs-RGO-IS), and the assembly of SnO2 NPs on RGO (SnO2 NPs-RGO-SA). As expected, the SnO2 NPs-RGO-PR-based sensor presents high sensitivity towards 5 ppm NO2 (65.5%), but 35.0% for the SnO2 NPs-RGO-IS-based sensor and 32.8% for the SnO2 NPs-RGO-SA-based sensor at RT. Meanwhile, the corresponding response time and recovery time calculated by achieving 90% of the current change of the SnO2 NPs-RGO-PR-based sensor for exposure to NO2 is 12 s and to air is 17 s, respectively, whereas 74/42 s for the SnO2 NPs-RGO-IS-based sensor and 77/90 s for the SnO2 NPs-RGO-SA-based sensor. The results can prove the tailoring sensing behavior of the gas sensor according to different structures of materials.

A Review on Metal Oxide-Graphene Derivative Nano-Composite Thin Film Gas Sensors

“…SEM image of hydrothermally grown SnO 2 nanoparticles and rGO composites reported by (a) Zhang et al [33] and (b) Peng et al [41]. a high concentration of oxygen vacancy [40,42] and Pt-activated SnO 2 nanoparticles-rGO hybrid [41]. Transmission electron micrograph (TEMs) of SnO 2 quantum dot decorated on rGO surface is represented in Figure 2(a-c).…”

“…Response time and recovery time varied from 1 s to 220 s and 1 s to 1552 s, respectively, as shown in Table 1. Wang et al confirmed that the uniform distribution of SnO 2 nanoparticles on rGO sheets is an effective factor for enhanced NO 2 sensing performances [42]. The p-n junction existed in the interface of nanoparticle and rGO contributed to good room temperature NO 2 sensing properties which is associated with the valid electron flow from SnO 2 nanoparticle to rGO.…”

“…Hydrothermal is one of the commonly reported techniques for preparing metal oxide nanoparticles-rGO composites. Among different metal oxides, SnO 2 nanoparticles were reported extensively to prepare nano-hybrid with rGO for efficient gas sensing application [33][34][35][36][37][38][39][40][41][42]. SnO 2 /rGO [33][34][35] nano-hybrid was prepared by facile hydrothermal treatment where precursor was prepared with mixture of SnCl 4 , HCl, H 2 O, and GO (or rGO).…”

“…Hydrazine hydrate was then added to the mixer to reduce GO Figure 2. TEM images of hydrothermally grown SnO 2 nanoparticles and rGO composites (a) SnO 2 quantum dot on rGO film surface [36], (b) high resolution (HR) TEM image of SnO 2 NPs on rGO [40], and (c) dense SnO 2 NPs on rGO [42]. at 110°C for 8 h [44].…”

Assembly with copper(ii) ions and D–π–A molecules on a graphene surface for ultra-fast acetic acid sensing at room temperature

“…In the past few years, graphene-based gas sensing materials have attracted considerable interest because of numerous advantages, such as a high response, short response time, low detection limit, and low working temperature (i.e., room-temperature). [7][8][9] In addition, the distinctive morphology of graphene endues a sensitive response to small changes in an ambient environment, and the functionalization of graphene nanosheets with various "guests" (i.e., organic molecules and nanoparticles) offers a unique selectivity for the resultant gas sensors. [10][11][12][13] It is known that the supramolecular assembly of graphene would retain the inherent structure of graphene and construct a better functional gas sensing scaffold.…”