State of the Art in Alcohol Sensing with 2D Materials

Abstract

Since the discovery of graphene, the star among new materials, there has been a surge of attention focused on the monatomic and monomolecular sheets which can be obtained by exfoliation of layered compounds. Such materials are known as two-dimensional (2D) materials and offer enormous versatility and potential. The ultimate single atom, or molecule, thickness of the 2D materials sheets provides the highest surface to weight ratio of all the nanomaterials, which opens the door to the design of more sensitive and reliable chemical sensors. The variety of properties and the possibility of tuning the chemical and surface properties of the 2D materials increase their potential as selective sensors, targeting chemical species that were previously difficult to detect. The planar structure and the mechanical flexibility of the sheets allow new sensor designs and put 2D materials at the forefront of all the candidates for wearable applications. When developing sensors for alcohol, the response time is an essential factor for many industrial and forensic applications, particularly when it comes to hand-held devices. Here, we review recent developments in the applications of 2D materials in sensing alcohols along with a study on parameters that affect the sensing capabilities. The review also discusses the strategies used to develop the sensor along with their mechanisms of sensing and provides a critique of the current limitations of 2D materials-based alcohol sensors and an outlook for the future research required to overcome the challenges.

Keywords: 2D materials; Alcohol probes; Electrochemical detectors; Ethanol metabolites; Sensors and biosensors.

Fig. 1

Comparing graphene oxide, reduced graphene, and highly reduced (cleared) graphene

Fig. 2

Schematic representation of some of the introduced GO and rGO production methods

Fig. 3

General scheme of a sensor. The interaction of an analyte with the selective receptor, coupled to a transducer, transfers a measurable signal to processing systems

Fig. 4

a TEM image of BCNs derived from BC gels. b TEM image of a graphene-BCN membrane. c AFM image of the structure of the graphene-BCN sensor. d Molecular structure of BCNs before and after modification with TEMPO. e Chemical reaction on BCNs caused by TEMPO-modification. f FTIR spectra of pristine BCNs and modified BCNs. Adapted with permission from Ref. [197]. Copyright 2017 Nature

Fig. 5

a rGO-based multisensor array. b–e SEM and AFM images of the chip. f A height profile of the film. g Schematic of the experimental set-up for sensor measurements. Adapted with permission from Ref. [199]. Copyright 2013 Royal Society of Chemistry

Fig. 6

a SEM image of the TiO₂ nanotubes, and the inset showing the opening top of the tubes, b, c HRTEM images of the MoS₂–TiO₂ composites, and the elemental distribution in the inset of b, d the response and recovery curves of the MoS₂–TiO₂ sensor to various ethanol concentrations from 50 to 700 ppm at 150 °C. e Sensitivity of the MoS₂–TiO₂ sensor at different concentrations of ethanol. Adapted with permission from Ref. [207]. Copyright 2016 Elsevier

Fig. 7

a–c SEM images at different magnification of hexagonal ZnCo₂O₄ grown on Ni foam using 0.2 mmol urea, d SEM image showed the increase in the sheets thickness with increasing the urea content, e sensor signal–time curve showing the fast response and slow recovery of the sensor, f the effect of the concentration on the sensor signal for various gases. Adapted with permission from Ref. [203]. Copyright 2018 Elsevier

Fig. 8

a SEM image of the Co₃O₄ microspheres, b, c TEM images of the hollow Co₃O₄ microspheres showing that the microspheres are composed of 2D nanosheets, d dynamic gas sensing transients of the sensors to ethanol with different concentrations at 220 °C. e Response of the sensor to various ethanol concentrations at 220 °C. f Long-term stability of the sensor to 30 ppm ethanol at 220 °C. Adapted with permission from Ref. [201]. Copyright 2017 Elsevier