A 3D Chemically Modified Graphene Hydrogel for Fast, Highly Sensitive, and Selective Gas Sensor

Abstract

Reduced graphene oxide (RGO) has proved to be a promising candidate in high‐performance gas sensing in ambient conditions. However, trace detection of different kinds of gases with simultaneously high sensitivity and selectivity is challenging. Here, a chemiresistor‐type sensor based on 3D sulfonated RGO hydrogel (S‐RGOH) is reported, which can detect a variety of important gases with high sensitivity, boosted selectivity, fast response, and good reversibility. The NaHSO3 functionalized RGOH displays remarkable 118.6 and 58.9 times higher responses to NO2 and NH3, respectively, compared with its unmodified RGOH counterpart. In addition, the S‐RGOH sensor is highly responsive to volatile organic compounds. More importantly, the characteristic patterns on the linearly fitted response–temperature curves are employed to distinguish various gases for the first time. The temperature of the sensor is elevated rapidly by an imbedded microheater with little power consumption. The 3D S‐RGOH is characterized and the sensing mechanisms are proposed. This work gains new insights into boosting the sensitivity of detecting various gases by combining chemical modification and 3D structural engineering of RGO, and improving the selectivity of gas sensing by employing temperature dependent response characteristics of RGO for different gases.

Rapid and Selective NH3 Sensing by Porous CuBr

“…Polyaniline sensors detect 40 ppb NH 3 at ≥90% RH,9 but these are usually for single‐use only as they recover too slowly. Other polymers like PEDOT:PSS nanowires feature higher LODs of 100 ppb,10 which is even higher for carbon‐based reduced graphene oxide (1.2 ppm in dry air)11 and 3D sulfonated reduced graphene oxide hydrogels (1.5 ppm) 12. Finally, metal‐oxides can also detect sub‐ppm NH 3 concentrations (e.g., Si‐doped MoO 3 with LODs of 51 ppb at 90% RH25 and pure MoO 3 of 280 ppt in dry air26) but these require typically elevated operational temperatures (e.g., 400–450 °C).…”

Hydrogels for Medical and Environmental Applications

“…C) 3D chemically modified graphene hydrogel. Reproduced with permission . Copyright 2017, Wiley‐VCH.…”

“…Graphene present in the hydrogel, which comes with defects and functionalities, has shown to have a better adsorption energy for NO 2 than NH 3 . The same group then went on to improve this graphene‐based composite, employed with a microheater and functionalizing it with NaHSO 3 , found that the responses increased 118.6, and 58.9 times for NO 2 and NH 3 , respectively (Figure C) . This sulfonated‐graphene hydrogel was also found to have a high responsivity for volatile organic compounds.…”

Versatile Aerogels for Sensors

“…Different from the traditional inorganic aerogels which is brittle, the CNT and graphene aerogels can be endowed with good flexibility, compressibility, and even stretchability by structural design . Moreover, because of the high degree of graphitization, the CNT and graphene aerogels possess superior thermal and chemical stability, and electrical properties than common carbon aerogels and can be used in many fields . As a supporting material, carbon aerogel can supply a 3D porous and electrically conductive network for fast mass transport and electron transfer, and large surface area for the depositing and avoiding the ripening and aggregation of active particles .…”

“…Graphene is a promising candidate for the gas sensors for detecting individual gas due to its exceptionally low‐noise property, however, the graphene‐based sensors without any modification always exhibit an inferior selectivity . The chemical modification and introduction of heterostructure materials in the 3D graphene network have been proved to be efficient ways to prepare high‐performance gas sensors . For example, HSO 3 − with lone‐pair electrons was used to modify the graphene sheets, and the resultant modified graphene network showed an enhanced selectivity of NO 2 due to the weak interaction between HSO 3 − and NO 2 .…”