Current Physical Chemistry - Volume 3, Issue 3, 2013

Graphene, one-atom-thick sheet of graphite, has many unique properties of high conductivity and charge carrier mobility, huge specific surface area and high energy storage as well as excellent mechanical strength. During the past several years, a variety of graphene doped electrode materials were successfully prepared and applied in lithium ion batteries. In this review, we will summarize the recent advances in the synthesis methods and its applications in lithium ion betteries. The challenges and prospects of graphene doped new electrode materials used in lithium ion batteries are also discussed.

Graphene has been attracted lots of attention for its unique properties and various applications in transistors, transparent conductors, sensors, etc. Many applications require stable and individual dispersion of graphene sheets in liquid phase. There are two ways to obtain graphene dispersion: 1) to disperse graphene powder in aqueous solution or organic solvents, 2) to exfoliate graphite into monolayer sheets in liquid phase directly. Usually, surfactants are needed to stabilize the dispersion. In this paper, recent work on preparation of graphene dispersion is reviewed, including dispersing, exfoliating, and stabilizing graphene in a variety of liquids. The dispersion of chemically derived graphene and liquidphase exfoliation of graphite are focused.

Graphene sheets have outstanding electrical, thermal, and mechanical properties. Furthermore, owing to the abundance of naturally existing graphite as the source material for graphene, it is considered an ideal reinforcing component to modify the properties of matrix, compared with other carbon nanofillers. This review will summarize the development of graphene/polymer composites, graphene/nanoparticle composites and graphene/carbon-based materials (nanotubes, fullerenes) composites in recent years, including the fabrication of nanocomposites, mechanical properties and electrical properties, thermal conductivity and thermal stability. The synergy of graphene with other types of carbon nanofillers used as hybrid reinforcing systems shows great potential and could significantly broaden the application of graphene. The relevant research will also be included in this review.

Graphene, whose discovery won the 2010 Nobel Prize in physics, has been a shining star in the material science in the past few years. Owing to its interesting electrical, optical, mechanical and chemical properties, graphene has found potential applications in a wide range of areas, including biomedicine, photocatalysis, nanoelectronics, etc. In this review, we summarize the latest progress of graphene in biological applications, including drug delivery, cancer therapies and biosensing, and discuss their opportunities and challenges in this emerging field. Furthermore, the preparation and toxicology of functionalized graphene composites are also introduced.

Graphene, a single-atom-thick planar sheet of graphite with zero-band gap, has great potential applications in nanoelectrics, biosensing, energy storage owing to its unique electrical, mechanical, and physical properties. Graphene nanoribbons (GNRs) are narrow and straight-edged stripes of graphene sheets. They are predicted to exhibit band gaps useful for field-effect transistors with high on/off ratio and carrier mobility. Over the past few years, they have attracted increasing attentions and became the attractive candidates for carbon-based nanoelectronics. This review provides a brief overview on the synthesis, properties and applications of GNRs. The effects of synthetic process on their morphology and electronic properties are discussed in detail. In addition, the applications of graphene nanoribbons in different fields have also briefly presented.

High values of Young’s modulus, excellent fracture strength, extremely high carrier mobility and optical transmittance make graphene films a promising and emerging candidate for next generation transparent and conductive electrodes for future optoelectronic devices. In this brief review, the research progress of graphene-based transparent and conductive electrode will be presented, with an emphasis on the preparation of single or few layers of graphene and their films as well as the latest developments of their applications in rapidly evolving optoelectronic devices, such as displays, solar cells and memory devices.

Clay mineral particles are interesting nanosized building blocks due to their high aspect ratio and the chemical properties. The main interest in this nanosized building blocks results essentially from the colloidal size and the permanent structural charge of the particles. Smectites or swelling clay minerals are naturally occurring nanomaterials that can be fully delaminated to elementary clay mineral platelets in dilute aqueous dispersion. This dilute aqueous smectite suspensions are well suited to convert into functional nanofilms. The functionalization is performed by ion exchange reaction with amphiphilic molecules carrying the desired functionality, such as chirality, two photon absorption, energy transfer, optical nonlinearity and magnetism, which are due to the nature of the amphiphilic cations and to the organization of both the amphiphilic molecules and the elementary clay mineral platelets. Controlling the structure of materials at the nanometre scale is of fundamental importance for tailoring such materials properties. Langmuir Blodgett films are known for a high degree of organization of organic molecules. Fundamental research into the organization of molecules at clay mineral platelets is necessary to optimize the materials for specific applications. This paper gives an overview of organo-clay hybrid Langmuir-Blodgett nano films.

In the last couple of years, dilute magnetic semiconductor (DMS) has drawn significant interest in the scientific community. Primarily this is due to its potential for application in spintronic devices. The euphoria acquired momentum following the theoretical prediction that diamagnetic ZnO can be made ferromagnetic even at room temperature by doping with transition metal (TM) ions such as Mn. The exact nature of the ferromagnetic coupling of spins in such materials is a matter of debate. Actually the impurity phase assisted ferromagnetism is not intended. The observed ferromagnetism should definitely be intrinsic. Claims and counterclaims in this issue are the key of this debate. However, one important understanding has evolved that defects play crucial role in stabilizing the ferromagnetic state in DMS systems. Some kind of defects or disorder favors ferromagnetism and others compete with this phenomenon. An effort will be made to present the contemporary scenario of research in this field. So far as discussion of synthesis of TM doped ZnO is concerned both bulk pellet and films will be investigated. Emphasis will be made for development of TM doped ZnO nanostructured samples. Low cost simple synthesis route of formation will be highlighted for its cost-effectiveness in comparison to sophisticated physical methods. A thorough investigation will be made for characterization of the samples. Structural, morphological, electrical, optical and the most crucial magnetic properties of TM doped ZnO will be discussed. So far as magnetic properties are concerned a careful analysis will be made from the results of field and temperature-dependent dc magnetization measurements and further from ac susceptibility measurement. The correlation between defects and observed intrinsic ferromagnetism of the samples, the crucial role of valence state of TM in achieving intrinsic ferromagnetism and the analysis of X-ray photoelectron spectroscopy data that is crucial in determining valence state of TM will be discussed. Energetic ion beam irradiation is an efficient tool for introducing defect states in solid materials particularly for semiconductors. There is a wide range of studies of ion irradiation effects on TM doped ZnO. Actually controlled formation of defects along the trajectory of the ion beam modifies chemical and physical properties of the specimens. A careful attempt will be made to explore that formation of defects by ion beam irradiation somehow favors in achieving intrinsic ferromagnetism in the samples or not, since proper correlation of defects and magnetic properties of TM doped ZnO samples can really enhance the potential of this field of scientific research. To develop TM doped ZnO as a perfect DMS system, synthesis and characterization have to be done in a very specific way. Controlled formation of defects is a key in case of synthesis and ion beam irradiation can be manifested suitably in this respect. Characterization of defects for TM doped ZnO would be given prior importance to unfold the role they play.

The aim of the present work is to analyse the dependence of the interaction energy between β-cyclodextrin and linear guest molecules on the composition and atomic distribution of the latter. The intermolecular energy is modelled by a Lennard-Jones potential where the molecular composition is represented by different parameters (σ1 ,ε1 ,σ2 ,ε2, p,mi), and a continuum description of the guest and cavity walls. The magnitude of the interaction energy depends mainly on the molecular composition, although the shape of this curve is a consequence of the atomic distribution giving rise to representations resembling well potentials or two minima separated by a potential barrier. The shape of this interaction potential does not depend on the symmetry of the molecular configuration, but it is related to the position of the larger atoms in the linear guest.

TiO2 nanoparticles were prepared by the sol–gel method using sodium dodecyl sulfonate, triton, tetrabutyl ammonium bromide surfactants and tested for the removal of Orange 2G dye from aqueous under UV light. The synthesized photocatalysts were characterized by XRD, FTIR, TEM, and BET measurements. The XRD patterns indicated that the crystalline phase of TiO2 is mainly anatase with crystallite sizes of 17.7-12.6 nm. BET measurements revealed that the surface area of TiO2 in the range of 293.62- 83.49 m2/g. The obtained results showed that the TiO2 nanoparticles prepared with the use of tetrabutyl ammonium bromide (TTAB) had a higher photocatalytic activity. The results indicated that the TTAB can remove 98% of the dye under optimum operational conditions of a dosage of 4 g/L, pH= 3 and a contact irradiation time of 28 hrs for initial dye concentrations of 1.5 x 10-5 mol/L.