Graphene/PVA buckypaper for strain sensing application

Abstract

Strain sensors in the form of buckypaper (BP) infiltrated with various polymers are considered a viable option for strain sensor applications such as structural health monitoring and human motion detection. Graphene has outstanding properties in terms of strength, heat and current conduction, optics, and many more. However, graphene in the form of BP has not been considered earlier for strain sensing applications. In this work, graphene-based BP infiltrated with polyvinyl alcohol (PVA) was synthesized by vacuum filtration technique and polymer intercalation. First, Graphene oxide (GO) was prepared via treatment with sulphuric acid and nitric acid. Whereas, to obtain high-quality BP, GO was sonicated in ethanol for 20 min with sonication intensity of 60%. FTIR studies confirmed the oxygenated groups on the surface of GO while the dispersion characteristics were validated using zeta potential analysis. The nanocomposite was synthesized by varying BP and PVA concentrations. Mechanical and electrical properties were measured using a computerized tensile testing machine, two probe method, and hall effect, respectively. The electrical conducting properties of the nanocomposites decreased with increasing PVA content; likewise, electron mobility also decreased while electrical resistance increased. The optimization study reports the highest mechanical properties such as tensile strength, Young’s Modulus, and elongation at break of 200.55 MPa, 6.59 GPa, and 6.79%, respectively. Finally, electrochemical testing in a strain range of ε ~ 4% also testifies superior strain sensing properties of 60 wt% graphene BP/PVA with a demonstration of repeatability, accuracy, and preciseness for five loading and unloading cycles with a gauge factor of 1.33. Thus, results prove the usefulness of the nanocomposite for commercial and industrial applications.

Comparison of Chloroplast Genomes among Species of Unisexual and Bisexual Clades of the Monocot Family Araceae

“…We observed K a /K s < 1 due to higher K s than K a for most of the protein-coding genes. These results are consistent with previous studies of angiosperm chloroplast genomes, including the family Araceae, as purifying selection pressure mostly acts on the genes of chloroplast genomes [10,12,19,65]. However, a higher K a /K s was also reported in some species of Araceae in which most of the genes were under positive selection [42].…”

“…The signatures of positive selection in chloroplast genes in these species might be due to the different types of stresses that they face in their respective ecological niches. The same genes were found to be under positive selection in various other species as well [12,17,65,81,82].…”

“…The inf A gene encodes translation initiation factor I, but we found this gene to be non-functional in all species. This gene is also reported to be non-functional or absent in the chloroplast genomes of other angiosperms, including species of Araceae [10][11][12]19,36,65]. Hence, it is suggested that either this gene is transferred to the nuclear genome as an active functional gene or a functional copy of this important gene already exists in the nuclear genome [39,66].…”

“…Recently, complete chloroplast genome sequences were successfully employed to elucidate the phylogenetic relationships among closely related or taxonomically difficult taxa [27,28]. Availability of chloroplast genomes provides quality tools for endangered species conservation, accurate barcoding, and avoiding intentional and unintentional adulteration of medicinal plants [1,29,30]. Moreover, chloroplast genomes play an important role in the identification and determination of the purity of commercial cultivars [1,31].…”

Green Synthesis of Clean Edge Graphene Nanosheets Using Natural Precursor

“…The vibration stretches of symmetric C-H bonds produce the peak at 2990 cm -1 . The peak at wavelength 1612 cm -1 corresponds to aromatic C=C stretching bonds, which are the skeleton of the graphinic structure and confirms the formation of graphene nanosheet [25].…”