Current Organic Chemistry - Volume 19, Issue 18, 2015

Graphene oxide (GO) is a unique material due to its various functional groups involving unsaturated double bonds, epoxy/hydroxyl groups on the basal planes, and carboxylic acid groups at the edges. Thus, GO exhibits uniqueness compared to other carbon related materials (such as carbon nanotubes, graphene sheets and fullerenes) due to its pronounced potential of functionality alteration. The latter feature allows GO to behave in accordance with the various surface groups and when involved in the preparation of a composite material with a functional polymer, to lead in enhanced surface properties. Therefore, GO can be hydrophilic and disperse in water or specific polar organic solvents owing to bearing hydroxyl and carboxylic groups or exhibit minimal dispersion in polar organic solvents and/or polymer surfaces due to the π-π stacking of the GO sheets. On the other hand, two methods have been reported in the literature for the preparation of GOpolymer composites: “grafting to” [1] and “grafting from” [2], which are both based on the linking approach between the polymer and GO, without of course damaging the GO structure.

Different approaches to obtain metallic particles on graphene are discussed in this Review article and their applications in catalysis, electrocatalysis and surface enhanced Raman spectroscopy (SERS) are highlighted. Synthetic methods for well-dispersed metallic particles (Au, Ag, Pt, Pd, TiO2 and QDs) on graphene are summarized, and comparisons are made in their utilization in a plethora of applications with pure metallic particles, neat graphene and carbon nanotubes/metallic particles. The importance of utilizing different reductants and stabilizers of metal precursors, as well as the sequential addition of the initial materials (graphene oxide or reduced graphene oxide, metal salts, reductant/stabilizer), are given particular focus, in order to illustrate the strengths and weaknesses in its system. The initial concentrations and volumes of the reagents, the moles of the metal precursor, and the temperature, were found to affect the size and shape of the metal particles and the stability of the graphene/metal hybrids. In this way, the morphology of the inorganic particles on graphene can be tuned for utilization in specific applications, either industrial or biomedical, allowing the development of the next generation materials in catalysis, as sensors, contrast agents and optoelectronics.

In this mini review we discuss the interactions of polyaromatic hydrocarbons (PAHs) with graphene and the experimental approaches developed so far to create novel graphene/PAH hybrids and composite systems. The utilization of these systems in electrical, biomedical and polymer-reinforcement applications is described while special emphasis is given to environmental remediation issues.

Graphene based materials are at the center of academic attention lately. Studies have shown that graphene can be successfully combined with other materials, aiming to enhance electrical, thermal or mechanical properties. Herein, a comprehensive study of the most recent advances in the field of polymer non-covalent functionalization of graphene is presented. Solid state graphene/polymer nanocomposites are classified into three main categories, namely, thin films, three-dimensional architectures and sponge-like materials, whereas in the liquid state graphene/ homopolymer and graphene/copolymer dispersions are discussed. Finally, recent works highlighting several potential applications of graphene/polymer based materials are presented.

Due to their unique structure, the optical and mechanical properties graphene and its derivatives (e.g. graphene oxide, reduced graphene oxide) have captured the attention of a constantly increasing number of scientists with regards to biomolecule sensing. This mini review focuses on one specific type of sensor, that consisting of graphene and polyelectrolytes. Polyelectrolyte-graphene nanocomposites exhibit outstanding detection capabilities by synergistically combining the characteristics of both components, outperforming traditional sensors in many cases. Characteristics and mechanistic details of the most important polyelectrolytegraphene based sensors will be discussed in detail in addition to some current challenges and future perspectives.

Carbon nanostructures and especially graphene oxide (GO) have attracted tremendous interest in the scientific community due to the potential utilization in numerous applications in the last decade. Herein, we describe the recent advances in the field of biotechnology and biomedicine of graphene oxide/polymer hybrids as novel nanocarriers for drug and gene delivery.

Energy production and storage have become key issues due to the ever increasing demand of electricity in modern days. Rechargeable batteries are recognized as the primary power sources for applications from portable electronic devices to electric vehicles. Recently, there has been a growing interest in investigating graphene nanocomposite materials for various energy storage applications, such as electrodes in lithium batteries. With its unique structural, mechanical, and electrical properties, graphene can be a critical component in nanostructured electrode materials with improved capacity and cyclability, enabling the development of advanced batteries and new battery technologies. This paper reviews the recent achievements in graphene utilization in negative electrodes for Li-ion batteries and introduces the latest progress of flexible graphene-based Li-ion batteries. A survey of the scientific advances achieved thanks to the use of graphene in the so called “beyond Li-ion” technologies, namely Li-sulphur and Li-O2 batteries, is also presented.

In the present review article we discuss the progress that has been thus far achieved towards producing graphene nanoribbons (GNRs) with predefined dimensions and, therefore, electronic properties, by using bottom-up approaches. Some selected, representative top-down strategies are also reviewed. GNRs are graphitic carbon-based materials having nano-scale dimensions and semiconducting or metallic electronic properties depending on their geometry and dimensions. These GNRs electronic characteristics are in sharp contrast to those of graphene, the parent graphitic material, which is an atomically-thick carbon sheet with semimetal, zero band gap characteristics.