Syntheses of graphene-based materials for bioelectrochemical and photothermal applications

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This dissertation aims to explore bioelectrochemical- and photothermal-related applications using graphene-based composite materials. A highly durable microbial fuel cell (MFC) and a highly sensitive electrochemiluminescence (ECL) biosensor for the detection of 3,3′,5-triiodothyronine (T3) were designed using reduced graphene oxide as the coating material as well as the biomolecule carrier, attributing to high electroconductivity and high surface to volume ratio of graphene. In addition, because of the intrinsic high photothermal conversion rates, carbon materials integrated with poly(N- isopropylacrylamide) (PNIPAM) can be used for the applications of a smart window and a near-infrared (NIR) light-controllable valve. First, through a facile and cost-effective dip-coating process, carbon materials-coated melamine sponge was fabricated for MFC’s bioanode, providing a conductive network for the transfer of electrons and excellent biocompatibility for the proliferation of Escherichia coli. The scaffold with high porosity and large specific area not only provided a large specific area for the immobilization of E. coli but also possessed high mass transfer rate, improving the MFC performance with a maximum current density of 335 Am3 and a remarkably durable lifetime of 20 days at 37 °C. Then, a nanoprobe used in an ECL biosensor was designed, comprising three components, silver nanoparticles decorated with functionalized GO, a ruthenium complex, and an anti-T3 antibody, using the features of high aspect surface ratio, high conductivity, and numerous moieties of GO. By supplying electricity, the GO-based nanoprobe underwent electrophoresis to the anode at which ECL was induced, generating a signal corresponding to the T3 molecule concentration. T3 was quantitatively measured in the range from 0.1 pg/mL to 0.8 ng/mL with a detection limit of 0.05 pg/mL. In addition, the novel immunosensor exhibited good specificity in the presence of serum. Subsequently, smart glasses loaded with GO-impregnated PNIPAM hydrogel were also prepared. By uniformly intercalating photothermic GO within a thermotropic PNIPAM hydrogel, this automatically smart glass could transform its transparency from 92% to 0% under the sunshine; as a result, screening sunlight and preventing further increase in temperature of a space. In addition, the GO-impregnated thermotropic hydrogel absorbed colored organic solvents, affording a smart glass with arbitrary color. Finally, an eco-friendly, facile, and efficient method was proposed using dopamine as the base for the secondary immobilization of titanium oxide (TiO2) and PNIPAM on carbon fiber clothes (CFCs), which render CFCs with properties of superhydrophobicity and thermo-responsiveness. A CFC with periodic superhydrophobic-hydrophilic patterns comprising TiO2@CFC and PD-coated hydrophilic striped patterns exhibited excellent performance for water harvesting at rates of 206 mg cm2 h1. In addition, the results reported in the dissertation indicated that the modification of a surface with characteristics of temperature responsiveness demonstrates significant potential for the adjustment of water evaporation, as well as NIR-controllable valves.