Smart Materials & Structures

Graphene (monolayer and few layers) is a two-dimensional material with the large anisotropy between in-plane and outof-plane directions. Carbon nanowalls (CNWs) are few-layer graphenes with open boundaries, standing vertically on a substrate. Th e sheets form a self-supported network of mazelike-wall structures. CNWs and similar graphene structures can be synthesized by several plasma enhanced chemical vapor deposition (PECVD) techniques. CNWs are sometimes decorated with metal nanoparticles and biomolecules. Th e structure of CNWs with large surface area would be suitable for the platform in electrochemical and biosensing applications. CNW fi lms can be potentially used as electrodes of electrochmical sensor,capacitor, dye-sensitized solar cell, polymer electrolyte fuel cell (PEFC), and implantable glucose fuel cell (GFC). Among these, CNW electrodes in fuel cells should be decorated with catalytic nanoparticles such as Pt. From a practical point of view, control of CNW structures including spacing between adjacent nanowalls and crystallinity is signifi cantly important. Moreover, formation method of catalytic metal nanoparticles should be established. We carried out CNW growth using PECVD employing CH4/H2/Ar mixtures with emphasis on the structure control of CNWs. We report the eff ects of ion bombardment and catalytic metals on the nucleation of vertical nanographenes to realize active control of interspace between adjacent walls. Moreover, CNW surface was decorated with Pt nanoparticles by the reduction of chloroplatinic acid or by the metal-organic chemical deposition employing supercritical fl uid. We also report the performances of hydrogen peroxide sensor, PEFC and GFC, where CNW electrode was used.