Nanomaterials: Graphene rolls off the press

The Application of Graphene and Its Derivatives to Energy Conversion, Storage, and Environmental and Biosensing Devices

Graphene (GR) and its derivatives are promising materials on the horizon of nanotechnology and material science and have attracted a tremendous amount of research interest in recent years. The unique atom-thick 2D structure with sp(2) hybridization and large specific surface area, high thermal conductivity, superior electron mobility, and chemical stability have made GR and its derivatives extremely attractive components for composite materials for solar energy conversion, energy storage, environmental purification, and biosensor applications. This review gives a brief introduction of GR's unique structure, band structure engineering, physical and chemical properties, and recent energy-related progress of GR-based materials in the fields of energy conversion (e.g., photocatalysis, photoelectrochemical water splitting, CO2 reduction, dye-sensitized and organic solar cells, and photosensitizers in photovoltaic devices) and energy storage (batteries, fuel cells, and supercapacitors). The vast coverage of advancements in environmental applications of GR-based materials for photocatalytic degradation of organic pollutants, gas sensing, and removal of heavy-metal ions is presented. Additionally, the use of graphene composites in the biosensing field is discussed. We conclude the review with remarks on the challenges, prospects, and further development of GR-based materials in the exciting fields of energy, environment, and bioscience.

The roles of lithium-philic giant nitrogen-doped graphene in protecting micron-sized silicon anode from fading

A stable Si-based anode with a high initial coulombic efficiency (ICE) for lithium-ion batteries (LIB) is critical for energy storage. In the present paper, a new scalable method is adopted in combination with giant nitrogen-doped graphene and micron-size electrode materials. We first synthesize a new type of freestanding LIB anode composed of micron-sized Si (mSi) particles wrapped by giant nitrogen-doped graphene (mSi@GNG) film. High ICE (>85%) and long cycle life (more than 80 cycles) are obtained. In the mSi@GNG composite, preferential formation of a stable solid electrolyte interphase (SEI) on the surface of graphene sheets is achieved. The formation and components of SEI are identified for the first time by using UV-resonance Raman spectroscopy and Raman mapping, which will revive the study of formation and evolution of SEI by Raman. New mechanism is proposed that the giant graphene sheets protect the mSi particles from over-lithiation and fracture. Such a simple and scalable method may also be applied to other anode systems to boost their energy and power densities for LIB.

Electronic transport in monolayer graphene with extreme physical deformation: ab initio density functional calculation

The electronic transport properties of monolayer graphene with extreme physical deformation are studied using ab initio calculations. The aim is to explore the influence of physical bending on transport properties and identify the most important geometrical parameter. The transmission spectra are relatively insensitive to the geometrical parameters in low-energy regions-even in the extreme case of uniaxial bending. The results suggest that graphene, with its superb electromechanical robustness, could serve as a viable nanoscale material platform in a wide spectrum of applications such as photovoltaics, flexible electronics, and 3D carbon chips.

The current state of engineered nanomaterials in consumer goods and waste streams: the need to develop nanoproperty-quantifiable sensors for monitoring engineered nanomaterials

As nanomaterials are harnessed for medicine and other technological advances, an understanding of the toxicology of these new materials is required to inform our use. This toxicological knowledge will be required to establish the medical and environmental regulations required to protect consumers and those involved in nanomaterial manufacturing. Nanoparticles of titanium oxide, carbon nanotubes, semiconductor quantum dots, gold, and silver represent a high percentage of the nanotechnology currently available or currently poised to reach consumers. For these nanoparticles, this review aims to identify current applications, the current methods used for characterization and quantification, current environmental concentrations (if known), and an introduction to the toxicology research. Continued development of analytical tools for the characterization and quantification of nanomaterials in complex environmental and biological samples will be required for our understanding of the toxicology and environmental impact of nanomaterials. Nearly all materials exhibit toxicity at a high enough concentration. Robust, rapid, and cost effective analytical techniques will be required to determine current background levels of anthropogenic, accidental, and engineered nanoparticles in air, water, and soil. The impact of the growing number of engineered nanoparticles used in consumer goods and medical applications can then be estimated. This will allow toxicological profiles relevant to the demonstrated or predicted environmental concentrations to be determined.