서강대학교

초록/요약

Graphene (GR) is a flat monolayer of sp2-bonded single carbon atoms densely packed into a honeycomb crystal lattice. Due to its unique characteristics, GR is expected to contribute to enhanced nano-electronic, catalysts, bio-electronic devices, etc. However, the single-layered GR sheets have a tendency to form irreversible aggregates or even to restack easily due to π-π stacking and van der Waals attraction. It is expected that the two-dimensional (2D) GR sheets not only reduce their effective sensing ability but also compromise their properties, such as the accessible sensing surface area on the working electrode. Therefore, this study introduces three-dimensional (3D) GR and 3D GR based nanocomposites for preventing of aggregation and restacking, and then applied to various promising electrochemical applications such as glucose biosensor, prostate specific antigen (PSA) immunosensor, and direct methanol fuel cells (DMFCs). Chapter 1 describes the backgrounds as well as objectives and summary of this thesis and Chapter 2 shows the characteristics of 3D GR and 3D GR based nanocomposites. Aerosol process was employed to synthesize the 3D GR based nanocomposites using a colloidal mixture of graphene oxide and various precursors. The morphology of 3D GR based nanocomposites was generally the shape of a crumpled paper ball. The 3D GR based nanocomposites showed higher specific surface area than 2D GR sheets and tightly packed into a near 3D form without significantly losing surface area. 3D GR based metal oxide and metal nanocomposites such as GR-titanum dioxide, GR-platinum, GR-gold, and GR-platinum-silver (GR-TiO2, GR-Pt, GR-Au, and GR-Pt-Ag) are applied to an enhanced glucose biosensor in Chapter 3 and 4. The amperometric response of the glucose biosensor fabricated by the GR-TiO2 nanocomposite was linear against a concentration of glucose ranging from 0 to 8 mM. The as-prepared glucose biosensor based on the GR-TiO2 nanocomposite showed higher catalytic performance for glucose redox than a pure TiO2 and GR biosensor. All the biosensors based on the GR-metal samples exhibited a higher current flow as well as clear redox peaks, which resulted in a superior ability of the catalyst in terms of an electrochemical reaction. The amperometric response of the glucose biosensor based on the 3D GR-metal nanocomposites indicated the high sensitivity. Highly sensitive and label-free detection of the PSA remains a challenge in the diagnosis of prostate cancer. Here, a novel 3D electrochemical immunosensor capable of sensitive and label-free detection of PSA is reported in Chapter 5. This unique immunosensor was equipped with a highly conductive 3D GR-Au nanocomposite modified electrode. This novel 3D immunosensor functioned very well over a broad linear range of 0-10 ng/mL with a low detection limit of 0.59 ng/ml. Furtherrmore, it exhibited a significantly increased electron transfer and high sensitivity toward PSA. Satisfactory selectivity, reproducibility, and stability of the 3D immunosensor were also exhibited. The 3D GR decorated with Pt (3D GR-Pt) and Pt-Au alloy nanoparticles (3D GR/PtAu) are prepared and applied to electrocatalysts for methanol oxidation reaction in Chapter 6. The 3D GR/PtAu exhibited a high specific surface area and an electrochemical surface area (ECSA) up to 238 and 325 m2/g, respectively. The as-prepared 3D GR-Pt and 3D GR/PtAu showed the highest electrocatalytic activity for the methanol oxidation reaction compared with commercial Pt-carbon black. Their electrocatalytic activity showed furthermore the highest performance in the world for the methanol oxidation reaction. The increased electrocatalytic activity was attributed to the high specific surface area of 3D formation and the effective surface structure of Pt-Au alloy nanoparticles. Chapter 7 contains the general conclusions of all topics discussed in Chapter 2 to Chapter 6.