With a rapidly growing population, development of new materials, techniques and devices which can provide safe potable water continues to be one of the major research emphases of the scientific community. While the development of new metal oxide catalysts is progressing, albeit at a slower pace, the concurrent and rapid development of high surface area catalyst supports such as graphene and its functionalised derivatives has provided unprecedented promise in the development of multifunctional catalysts. Recent works have shown that metal oxide/graphene composites can perform multiple roles including (but not limited to): photocatalysts, adsorbents and antimicrobial agents making them an effective agent against all major water pollutants including organic molecules, heavy metal ions and water borne pathogens, respectively. This article presents a comprehensive review on the application of metal oxide/graphene composites in water treatment and their role as photocatalyst, adsorbent and disinfectant in water remediation. Through this review, we discuss the current state of the art in metal oxide/graphene composites for water purification and also provide a comprehensive analysis of the nature of interaction of these composites with various types of pollutants which dictates their photocatalytic, adsorptive and antimicrobial activities. The review concludes with a summary on the role of graphene based materials in removal of pollutants from water and some proposed strategies for designing of highly efficient multifunctional metal oxide/graphene composites for water remediation. A brief perspective on the challenges and new directions in the area is also provided for researchers interested in designing advanced water treatment strategies using graphene based advanced materials.

Field emission (FE) has been extensively explored from various exotic low dimensional carbon nanomaterials, such as amorphous carbon films, 1 single and multiwalled carbon nanotubes (CNTs), 2 tubular graphitic cones, 3 vertically aligned nanowalls, 4 few-layered graphene (FLG) nanoflakes, 5,6 and, more recently, from doped and pristine graphene. 7,8 Graphene, a two-dimensional monatomic plane layer of hexagonally arrayed sp 2-hybridized carbon atoms forms the backbone of all the above-mentioned carbon nanostructures. 9 The highly desirable properties of graphene, such as atomic thickness, excellent electrical conductivity, and high aspect ratio, make it an ideal candidate for field emission applications. 7-9 Also, as compared to CNTs, the presence of a large number of edges may render graphene superior for electron tunneling. 7 Although FE in CNTs is highly efficient, it has been shown that heteroatom doping by elements, such as nitrogen, can further reduce the effective tunneling potential barrier, thereby reducing the turn-on field and significantly increasing the electron emission current. 10,11 Nitrogen acts as an electron donor in CNTs because it has five valence electrons and causes a shift in the Fermi level (E F) to the conduction band and increases the electron density of states (DOS). In the case of graphene, theoretical studies have shown that substitutional heteroatom doping can modulate the band structure of graphene, leading to a metal-semiconductor transition, thereby expanding the applications of graphene. 12,13 Although Malesevic et al. 5 and Qi et al. 6 have shown the field emission behavior of pristine and Ar plasma-treated FLG nanoflakes, respectively, to the best of our knowledge, until now, there ' EXPERIMENTAL SECTION The synthesis of FLGs was carried out in a SEKI MPECVD deposition system, equipped with a 1.5 kW, 2.45 GHz microwave source. The substrates used were bare n-type heavily doped Si wafers (resistivity < 0.005 Ω cm) (10 mm  10 mm). Prior to growth, the substrates were pretreated with N 2 plasma at 650 W at 40 Torr while the substrate temperature was maintained at 900°C. Synthesis was then carried out using CH 4 /N 2 (gas flow

Scalable production of high-quality MoS 2 nanosheets remains challenging for industrial applications and research in basic sciences. N-methyl-2pyrrolidine (NMP) is a commonly used solvent for exfoliation of MoS 2 nanosheets having further disadvantage of slow volatility rate. The present study demonstrates a cost-effective facile chemical route to synthesize few-layer MoS 2 nanosheets using acetone as a solvent and by varying bulk initial concentration of samples to scale up the production in large scale to fulfill the demand for potential applications. In our study, we aim to obtain stable growth of high quality few layer MoS 2 nanosheets by long sonication times. Optical absorption spectra, Raman spectra, size of nanosheets and layer thickness of as-grown MoS 2 nanosheets were found to be matching with those obtained from other synthesis methods. Effective photocatalytic performance of MoS 2 nanosheets without being consumed as a reactant was experimented by decomposing Methylene Blue dye in aqueous solution under irradiation of visible light. This study provides an idea to synthesize low-cost, sustainable and efficient photocatalytic material in large scale for the next generation to control water pollution quite efficiently by protecting the environment from the contamination coming from these dyes.

Significant enhancement in supercapacitor performance was achieved via the synthesis of nanocrystalline RuO 2 on vertically aligned Few Layered Graphene (FLG) nanoflakes, synthesized on bare n-type heavily doped silicon substrates by microwave plasma chemical vapour deposition. The RuO 2 nanoparticles (diameter <2 nm) were deposited using a combination of low base pressure radio frequency magnetron sputtering and subsequent electrochemical cycling in acidic media. The welldispersed RuO 2 nanoparticles on FLGs achieve a specific capacitance of the order of 650 F g À1. The specific capacitance of RuO 2-FLGs is significantly higher than pristine sputtered RuO 2 ($320 F g À1) and FLGs ($6 F g À1) indicative of the synergistic effect between the FLGs and RuO 2. In addition, the fabricated RuO 2-FLG supercapacitors show excellent cycling capability with approximately 70% retention of initial specific capacitance over 4000 cycles at high charging-discharging rates of 500 mV s À1. The superior electrochemical performance is attributed to the good electronic conductivity of the FLGs as well as high utilization of well-dispersed RuO 2 nanoparticles on FLGs.

Thermoelectric materials have been extensively used in space satellites, automobiles, and, more recently, in solar thermal application as power generators. Solar thermoelectric generators (STEGs) have enjoyed rapidly improving efficiency in recent years in both concentrated and non-concentrated systems. However, there is still a critical need for further research and development of their materials and systems design before this technology can deployed for large-scale power generation.