Graphene is a monolayer graphite sheet which consists of sp² carbon. Since it was isolated in 2004, it has been expected to be used as a new material for various applications such as semiconductors and transparent electrodes due to its attractive properties. High throughput synthesis methods are urgently required for industrial application. Therefore, some synthesis methods such as chemical vapor deposition (CVD) on metals and epitaxial growth on SiC have been developed. In terms of high yield and easiness, chemical exfoliation via graphene oxide (GO) is the most appropriate method. We can obtain plenty of monolayer sheets on many kinds of substrates by this method. In addition, the size of the GO sheets is more than 100 µm. However, the quality of graphene produced from graphene oxide is quite low compared with graphene synthesized by other methods. Therefore, many researchers have tried to improve its quality using various methods. This review introduces some results for the high throughput synthesis of graphene from GO explaining the advantages and disadvantages of each method.

Graphene has received much attention because of its unique properties with various expected applications. To now methods for its growth of graphene have been mainly catalytic chemical vapor deposition, heat-treatment of SiC, and the reduction of graphene-oxide. However, there still is room for methods that are more simple, cost-effective, and large scale. In this contribution, we review the synthesis and characterization of graphene from agricultural waste such as rice husks. The graphene obtained from rice husk possesses a unique structure with clean edges, nanosize holes, and topological defects in the carbon lattice, which could trigger novel physicochemical properties. It is envisaged that graphene from rice husks opens the possibility of developing various applications due to its inexpensive, simple and scalable production.

For ultra-high sensitive sensing at room temperature, the resonance properties such as the resonant frequency and Q factor of a graphene mechanical resonator were improved by fluorine surface modification and applying a tensile stress. The surface of a membrane-type mono-layer graphene mechanical resonator with a size of 2 µm×2 µm was fluorinated using XeF₂ gas, and the effect of the fluorine surface modification on its resonance was investigated. We found that the Q factor was increased by a factor of 7.7 after fluorination for 30 s. In addition, the fabrication of a double-clamped beam graphene resonator with a high Q factor was achieved by applying a tensile stress induced by the shrinkage of a SU-8 resist. A graphene resonator 10 µm long, 300 nm wide and consisting of 5 layers was fabricated. A superior Q factor of 7723 was achieved at room temperature in a vacuum of 10⁻³ Pa. These methods are expected to be key techniques in order to obtain an ultra-high sensitive sensing device based on a graphene mechanical resonator.

We developed a biomolecular interface on the surface of graphene (or graphene oxide) to detect biologically important proteins such as cancer markers. Here, graphene behaves as an efficient acceptor for fluorescence resonance energy transfer (FRET) over the entire visible wavelength region. Graphene works simultaneously as a strong adsorbate for single-stranded DNAs (ssDNAs) such as aptamers by a π-π interaction in the sp² domain. In our system, the graphene surface is modified with a pyrene-aptamer-dye probe. The segments work as a linker to the graphene surface, a selective protein recognition part, and a fluorescence detection tag. The system allows us to perform molecular detection on a solid surface, which constitutes a powerful tool for realizing an on-chip sensor. Using the on-chip sensor, detection of the target protein is possible simply by adding a sample smaller than 1 µL to a sensor chip and is complete in about a minute. Here we review our recent achievements using the on-chip biosensor, which include the simultaneous detection of multiple target molecules on a single chip, the molecular design of a probe for enhancing the sensitivity, and a quantitative comparison of the sensing performance using graphene and graphene oxide platforms.

Thermoplastic epoxy composites are commonly used for electronic devices and building repairs. Advances in the mixing processes of nanoparticles with large surface areas that leads to improved mechanical and rheological properties of epoxy composites have generated a growing interest in inorganic and organic nanocomposites over the past two decades. In the past decade, many research groups have reported the physicochemical properties of graphene oxide (GO) and chemically-modified GO-based epoxy nanocomposites. However, the characteristics of chemically-modified GO affect the curing process of the epoxy resin and the resulting properties of the composite. In this review, we explore the theoretical and experimental relationships between mechanical and rheological properties and the chemical structure of chemically-modified GO in relation to the applicable curing process. Based on these relationships, design strategies to improve the properties of epoxy composites can be realized, which can potentially lead to applications in new fields.