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We report on a one-step binder-free fabrication method for electrochemical double layer (EDL) capacitor electrodes consisting of vertically-oriented graphene uniformly grown on a metallic current collector. The double-layer capacitive behavior of the resulting electrode is studied in both aqueous and organic electrolytes. Compared with conventional graphene-based EDL capacitor electrode fabrication methods, this method offers the following advantages: (a) no need to use a binder, (b) open channels for better ion access, and (c) exposed edge planes for improved material wettability. These unique features lead to excellent capacitive behavior in organic electrolytes, including a specific capacitance slightly higher than that in aqueous electrolytes at the same potential scan rate and a high knee frequency (∼3174 Hz in the current work).

Synthesis of carbon nanowalls (CNWs) at atmospheric pressure is realized by using a negative normal glow discharge, which differs from prior low-pressure plasma-enhanced chemical vapor deposition methods for CNW growth and holds great potential for mass-production of CNWs. The glow discharge is characterized for electrical and optical properties. The resulting CNW structures are analyzed using transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy. The CNW growth process is examined for effects of discharge regime, discharge duration (growth time), hydroxyl radicals (water vapor), and local current density. Possible CNW growth mechanism and critical process parameters to the CNW growth and evolution are identified. OH radicals play an essential role in the initial nucleation process, but excess OH radicals accelerate the oxidation of CNWs. For a fixed growth time, there exists an optimum feed gas relative humidity and an optimum current density (∼40% and ∼9.17 A/m2, respectively, in the current work) for the growth of large and less defective CNWs with a high degree of crystallinity. Results obtained in this study can be used to tailor final properties of the as-grown CNWs for various applications.

This study demonstrates the electrical detection of protein binding by the introduction of Au nanoparticle–antibody conjugates in a carbon nanotube field effect transistor (CNTFET), in which the nanoparticle-functionalized carbon nanotube serves as the electrical conducting channel. Antibody (anti-horseradish peroxidase) and antigen (horseradish peroxidase) binding events lead to the amplitude change in the drain current, which can be sensitively detected by FET measurements. The sensor shows negligible response to mismatched proteins such as Immunoglobulin G (IgG), confirming the specificity of the biosensor. The reported CNTFET-based biosensor could be adapted to detect a variety of proteins for in vitro diagnostics.