Graphene oxide based free-standing films for humidity and hydrogen peroxide sensing

We have synthesized free-standing films of graphene oxide (GO), reduced graphene oxide (rGO) and graphene oxide-manganese oxide composite (GMC) for humidity and hydrogen peroxide sensing applications. Structural and morphological characterizations of these free-standing films were performed using X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The presence of anionic sites in the form of oxygen functional groups (OFGs) at the surface of GO along with its hydrophilic nature makes GO a unique candidate as a suitable material for humidity and hydrogen peroxide sensing. In contrast, rGO has a relatively lower fraction of OFGs, higher electrical conductivity and hydrophobicity compared to GO. We estimate the response time, recovery time and stability of free-standing films over multiple sensing-degassing cycles of the as chemically prepared GO, rGO and GMC films for humidity sensing. We observed a dramatic improvement in both the response and recovery times for rGO and GMC films compared to GO film at relatively low humidity, while at higher humidity percentages, rGO film has the best response and recovery times compared to GMC and GO films. Regarding stability, GO was found to be more stable over multiple sensing cycles compared to rGO and GMC at high humidity values. In addition to this, we observed that the addition of metal oxide to GO makes GMC film more selective for hydrogen peroxide sensing in comparison to GO and rGO film at a lower concentration.