Abstract
In this paper, we propose strain-sensitive thin films based on chemically reduced graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) without adding any further surfactants. In spite of the insulating properties of the thin-film-based GO due to the presence functional groups such as hydroxyl, epoxy, and carbonyl groups in its atomic structure, a significant enhancement of the film conductivity was reached by chemical reduction with hydro-iodic acid. By optimizing the MWCNT content, a significant improvement of electrical and mechanical thin film sensitivity is realized. The optical properties and the morphology of the prepared thin films were studied using ultraviolet-visible spectroscopy (UV-Vis) and scanning electron microscope (SEM). The UV-Vis spectra showed the ability to tune the band gap of the GO by changing the MWCNT content, whereas the SEM indicated that the MWCNTs were well dissolved and coated by the GO. Investigations of the piezoresistive properties of the hybrid nanocomposite material under mechanical load show a linear trend between the electrical resistance and the applied strain. A relatively high gauge factor of 8.5 is reached compared to the commercial metallic strain gauges. The self-assembled hybrid films exhibit outstanding properties in electric conductivity, mechanical strength, and strain sensitivity, which provide a high potential for use in strain-sensing applications.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-015-1216-5) contains supplementary material, which is available to authorized users.
Highlights
In the last decade, the increasing trend towards flexible electronic devices emphasizes their attractive perspective in numerous applications
Optical Investigation The ultraviolet-visible spectroscopy (UV-Vis) spectra (Fig. 2(a)) show two peaks at 970 and 1200 nm which are attributed to the asymmetric stretch of S(OH)2 and its first overtone [46]
It can be seen that the increase of the multiwalled carbon nanotubes (MWCNTs) content in the graphene oxide (GO) results in a linear decrease of the band gap due to the partial recovery of the πconjugation system [36,37,38]
Summary
The increasing trend towards flexible electronic devices emphasizes their attractive perspective in numerous applications. Essential components in such multifunctional devices are sensors, which should be flexible, scalable, sensitive, and robust for integration. Due to their promising electrical and mechanical properties, carbon nanotubes (CNTs) are promising nanomaterials for realization of strain sensors with high performance. Carbon-nanomaterial-filled composites have been intensively studied as multifunctional material for numerous smart applications. The induced strain alters the electrical resistance of a randomly distributed CNT network. The change of the electrical resistance results from the modification of contact arrangements and the tunneling distance between
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