Abstract
Hybrids between biopolymeric materials and low-cost conductive carbon-based materials are interesting materials for applications in electronics, potentially reducing the need for materials that generate environmentally harmful electronic waste. Herein we investigate a scalable ball-milling method to form graphene nanoplatelets (GNPs) by milling graphite flakes with aqueous dispersions of proteins or protein nanofibrils (PNFs). Aqueous GNP dispersions with high concentrations (up to 3.2 mg mL–1) are obtained under appropriate conditions. The PNFs/proteins help to exfoliate graphite and stabilize the resulting GNP dispersions by electrostatic repulsion. PNFs are prepared from hen egg white lysozyme (HEWL) and β-lactoglobulin (BLG). The GNP dispersions can be processed into free-standing films having an electrical conductivity of up to 110 S m–1. Alternatively, the GNP dispersions can be drop-cast on PET substrates, resulting in mechanically flexible films having an electrical conductivity of up to 65 S m–1. The drop-cast films are investigated regarding their thermoelectric properties, having Seebeck coefficients of about 50 μV K–1. By annealing drop-cast films and thus carbonizing residual PNFs, an increase of electrical conductivity, coupled with a modest decrease in Seebeck coefficient, is obtained resulting in materials displaying power factors of up to 4.6 μW m–1 K–2.
Highlights
Graphene sheets are built up from hexagonally arranged sp2-hybridized carbon atoms
A ball-milling procedure has been developed where graphite is milled with protein nanofibrils (PNFs) and under appropriate conditions aqueous dispersions with a high concentration of graphene nanoplatelets (GNPs) are obtained
Excess PNFs can, if desired, be removed by centrifugation in order to achieve conductive GNPs ink that can be processed into mechanically flexible conductive films
Summary
Graphene sheets are built up from hexagonally (honeycomb) arranged sp2-hybridized carbon atoms. The electrical conductivity of the GNPs exfoliated by PNFs were measured on samples drop-cast and dried on a glass substrate, and it was found that the conductivity of the samples containing excess protein was lower than the instrument detection limit. Due to the difficulty of accurately measuring thermal conductivity, an alternative parameter, the power factor defined as S2σ, is often employed for evaluation of thermoelectric materials.[31] We determined the Seebeck coefficient for the different PNF:GNP films. This is comparable to materials systems such as PEDOT/rGO, PEDOT:PSS/ graphene, and PANi/Graphene.[52,54,55]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
