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Graphene-based nano-technology is the future of biomedical devices including biosensors and, hence, it is essential to unravel the interaction of graphene oxide (GO) with cellular membrane. Here, the structural reorganization of lipid molecules, which are the building blocks of a cellular membrane, has been demonstrated in presence of GO flakes. The membrane is mimicked by forming a stack of lipid bilayers of zwitterionic phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and its structures have been probed by X-ray reflectivity and grazing incidence X-ray diffraction techniques. Lipid-GO composites have exhibited two sets of lamellar diffraction peaks illustrating GO-rich micro-domains in the matrix of phospholipid bilayers (GO-poor phase). In these domains, the GO flakes are observed to penetrate into hydrophobic core of the bilayer altering the thickness along with the overall electron density profile of the lipid layer. The GO-poor bilayer is closely related to the phase formed by pristine lipid molecules. The lattice parameters of a body-centred rectangular unit cell formed by chains of saturated phospholipids are found to be modified in presence of GO with a significant effect on molecular tilt. The structural description of GO-membrane interaction may pave the way of discerning the physical behaviour of the composites.

Environmental benign, inexpensive, flexible, smart energy storage micro-supercapacitors, with high energy and power densities and long-term cyclic stability are appealing for next generation energy storage devices. Conventionally, highly conducting carbon-based nanomaterials with high-surface areas are extensively used as supercapacitor electrode and the introduction of metal oxides (or conducting polymers) induces pseudocapacitance and can further enhances the specific capacitance and energy density. Red mud (RM), an aluminum industry waste by-product which is a rich source of hematite phase Fe2O3. RM is environmentally hazardous due to its alkalinity and is produced at an annual rate of ~ 110 million tonnes each year, much of which is not well utilized, and left to lie in large lakes; thus, methods of finding value-added applications for RM are well sought after. In this study, we used mechanical milling to produce uniform spherical RM nanoparticles and utilized these in a flexible micro-supercapacitor device. The as-synthesized nanoparticles were decorated over a laser induced porous 3D graphene (LIG) on a polyimide substrate. The composite electrode material was characterized using transmission electron microscopy (TEM), field effect scanning electron microscopy (FESEM), X-ray photo electron spectroscopy (XPS), Raman spectroscopy and cyclic voltammetry (CV). A solid-state ionic liquid based polymer gel electrolyte was produced using a mixture of ionic liquids {[EMI][TFSI] and [EMIM][BF4]} and a PVDF polymer. Inkjet printing technique was employed to produce the silver current collector and the as fabricated inter-digitated micro-supercapacitor device (Figure 1a) exhibited an areal capacitance of 203 mF cm-2 with a higher potential window of 2.7 V, high energy density of 0.018 mW h/cm2 at 0.66 mW/ cm2 power density. RM decoration increased the energy density of the device by 3.7 fold compared with pristine LIG device (Figure 1b). Rapid lateral ion flow in the planar architecture, presence of metal oxides (mostly hematite), higher electrochemically active surface area, better charge transfer kinetics were shown to yield improvements in the energy-density and the electrochemical performance of the device. An in-depth electrochemical study also revealed that the charge storage mechanism was governed by diffusion driven pseudocapacitance. The device exhibited good robustness and could resist bending and flexing and the prototype device exhibited to power a white-light LED (Figure 1c). Overall, this work demonstrates that RM may be used as a low-cost pseudocapacitive element in supercapacitor electrodes and aid in reducing the environmental impact of the aluminium production cycle by recycling this abundant waste product. Figure 1

In recent years, metal oxide‐based, inexpensive, stable electrodes are being explored as a potent source of high performance, sustainable supercapacitors. Here, the employment of industrial waste red mud as a pseudocapacitive electrode material is reported. Mechanical milling is used to produce uniform red mud nanoparticles, which are rich in hematite (Fe2O3), and lower amounts of other metal oxides. A comprehensive supercapacitive study of the electrode is presented as a function of ball‐milling time up to 15 h. Ten‐hour ball‐milled samples exhibit the highest pseudocapacitive behavior with a specific capacitance value of ≈317 F g−1, at a scan rate of 10 mV s−1 in 6 m aqueous potassium hydroxide electrolyte solution. The modified electrode shows an extraordinary retention of ≈97% after 5000 cycles. A detailed quantitative electrochemical analysis is carried out to understand the charge storage mechanism at the electrode–electrolyte interface. The formation of uniform nanoparticles and increased electrode stability are correlated with the high performance. This work presents two significant benefits for the environment; in energy storage, it shows the production of a stable and efficient supercapacitor electrode, and in waste management with new applications for the treatment of red mud.

Polystyrene is a chemically inert synthetic aromatic polymer. This widely used form of plastic is recalcitrant to biodegradation. The exponential production and consumption of polystyrene in various sectors has presented a great environment risk and raised the problem of waste management. Biodegradation by bacteria has previously shown great potential against various xenobiotics but there are only a few reports concerning polyolefins. By screening wetland microbes, we found two bacterial species

In this report, an effort has been made to develop an efficient PbS quantum dot-sensitized photoanode by simple successive ionic layer adsorption and reduction technique to enhance the overall photovoltaic performance of PbS quantum dot-sensitized solar cells. Three strategies have been adopted for the improvement of the photovoltaic performance of PbS quantum dot-sensitized solar cells, i.e., (i) by incorporation of TiO2-Au nanocomposites, where Au nanoparticles of different sizes are embedded into a TiO2 matrix, and (ii) variation of temperature at which quantum dots are deposited (iii) by postdeposition annealing of QD-sensitized photoanode in Ar atmosphere. We have used electrophoretic deposition technique to develop the nanocomposite-doped photoanode. High-resolution transmission electron microscopy confirms that the Au particles dispersed in the TiO2 matrix vary from 2 to 50 nm and PbS quantum dot size ranges 3.5–6 nm. The optical absorption of PbS quantum dot-sensitized TiO2-Au-incorporated photoanode is substantially enhanced as confirmed from the UV-visible absorption spectra measurements. The current-voltage characteristics of all the plasmonic quantum dot-sensitized solar cells under illumination (100 mW/cm2, AM 1.5) show significant improvement in power conversion efficiency using the abovementioned strategies. The maximum power conversion efficiency observed in PbS quantum dot-based quantum dot-sensitized solar cells is 7.0%. Electroimpedance spectroscopy has been utilized to understand the recombination kinetics in these solar cells.

The improvement of the plasma illumination (PI) properties of a microplasma device due to the application of nanocrystalline diamond-decorated graphene nanoflakes (NCD-GNFs) as a cathode is investigated. The improved plasma illumination (PI) behavior is closely related to the enhanced field electron emission (FEE) properties of the NCD-GNFs. The NCD-GNFs possess better FEE characteristics with a low turn-on field of 9.36 V μm−1 to induce the field emission, a high FEE current density of 2.57 mA cm−2 and a large field enhancement factor of 2380. The plasma can be triggered at a low voltage of 380 V, attaining a large plasma current density of 3.8 mA cm−2 at an applied voltage of 570 V. In addition, the NCD-GNF cathode shows enhanced lifetime stability of more than 21 min at an applied voltage of 430 V without showing any sign of degradation, whereas the bare GNFs can last only 4 min. The superior FEE and PI properties of the NCD-GNFs are ascribed to the unique combination of diamond and graphene. Transmission electron microscopic studies reveal that the NCD-GNFs contain nano-sized diamond films evenly decorated on the GNFs. Nanographitic phases in the grain boundaries of the diamond grains form electron transport networks that lead to improvement in the FEE characteristics of the NCD-GNFs.

Multifunctional reduced graphene oxide (RGO) coated cloths were prepared through the thermal treatment of GO coated cloths without using any harmful reducing agent. The effect of heating temperature on the wetting properties of the cloths was also monitored through contact angle measurement. The highest contact angle 141° was observed for the RGO coated dense cloth while the highest contact angle exhibited by the RGO coated sparse cloth was 130°. The as prepared RGO coated cloths were utilized as a filter and an absorbent for oil/water separation. The RGO coated sparse cloth was utilized as a filter for the separation of an oil/water mixture while the dense cloth was utilized as an absorbent for the selective absorption of oil from water. RGO coated cloths were also explored as an antibacterial agent and the effect of the microstructure of coated cloths on their antibacterial properties was also investigated. The cloth with the dense structure exhibited higher antibacterial activity compared to the sparse cloth. A significant loss of percentage viability up to 98% was achieved using the RGO coated cloth, proving it highly efficient as an antibacterial agent, which makes it a suitable bandage material for the dressing of open wounds. Apart from being antibacterial, the RGO coated cloths are also hydrophobic in nature so they can protect wound from water and atmospheric moisture which is not possible with ordinary bandages.

Saturation magnetization (Ms) of pristine bi-/tri-layered graphene (denoted as – FLG) is enhanced by over four (4) and thirty-four (34) times to 13.94 × 10−4 and 118.62 × 10−4 emu g−1, respectively, as compared to pristine FLGs (Ms of 3.47 × 10−4 emu g−1), via plasma-based-hydrogenation (known as graphone) and nitrogenation (known as N-graphene) reactions, respectively. However, upon organo-silane treatment on FLG (known as siliphene), the saturation magnetization is reduced by over thirty (30) times to 0.11 × 10−4 emu g−1, as compared to pristine FLG. Synchrotron based X-ray absorption near edge structure spectroscopy measurements have been carried out to investigate the electronic structure and the underlying mechanism responsible for the variation of magnetic properties. For graphone, the free spin available via the conversion of the sp2 → sp3 hybridized structure and the possibility of unpaired electrons from induced defects are the likely mechanism for ferromagnetic ordering. During nitrogenation, the Fermi level of FLGs is shifted upwards due to the formation of a graphitic like extra π-electron that makes the structure electron-rich, thereby, enhancing the magnetic coupling between magnetic moments. On the other hand, during the formation of siliphene, substitution of the C-atom in FLG by a Si-atom occurs and relaxes out the graphene plane to form Si–C tetrahedral sp3-bonding with a non-magnetic atomic arrangement showing no spin polarization phenomena and thereby reducing the magnetization. Thus, plasma functionalization offers a simple yet facile route to control the magnetic properties of the graphene systems and has potential implications for spintronic applications.

Grapes (Vitis vinifera) extract was explored as a “green reducing agent” for the preparation of reduced graphene oxide (RGO) from graphene oxide (GO). The effect of reduction time on physical, chemical and optical properties of the RGO was also investigated. Synthesized RGO samples exhibited excellent activity as an adsorbent for the removal of organic dye. Proposed synthesis is environmental friendly, cost effective and promising for the large scale production of RGO.

Gold nanoparticles (Au NPs) were synthesized using Au containing CTAB gel as a precursor. The effect of concentration of NaBH4 on the structural, optical, catalytic and electrochemical properties of the Au NPs was also investigated. With the increase of NaBH4 concentration from 0.1 to 0.15 M, an increase in the particle size and change in the morphology from spherical to elliptical was observed. Absorption and emission properties of the Au NPs were also probed using UV–Vis and photoluminescence spectroscopy respectively. Synthesized Au NPs samples were explored as catalyst for the reduction of 4-nitrophenol to 4-aminophenol. Catalytic activity of Au NPs samples prepared using 0.1 and 0.15 M concentration of NaBH4 were also compared. It was found that Au NPs prepared using lower concentration of NaBH4 (Au-0.1) exhibits better catalytic activity compared to the other Au NPs sample (Au-0.15). Synthesized Au NPs were also utilized as electrode material for the detection of Pb2+ ions, results show that Au NPs modified glassy carbon electrode can detect very low concentration of Pb2+ ions (2 µM). Au-0.1 sample exhibited better electrochemical performance compared to the Au-0.15 sample.

We have demonstrated that the gel-like mesophase of Cetyltrimethylammonium bromide (CTAB) can be synthesized by judicial adjustment of water to surfactant molar ratio (W 0 ), without using any additional salts, gelating agents or co-surfactants. Gel formation was found to be highly dependent on the water to surfactant molar ratio (W 0 ), with the lowest value of W 0 (41.5) resulting in rapid gel formation. Environmental scanning electron microscope (ESEM) analysis revealed that the gel was comprised of interconnected cylindrical structures. The presence of hydrogen bonding in the gel-like mesophase was confirmed by Fourier Transform Infrared spectroscopy (FTIR) analysis. Rheology measurements revealed that all the gel samples were highly viscoelastic in nature. Furthermore, Au and Ag containing CTAB gels were explored as precursors for the preparation of spherical Gold (Au) and Silver (Ag) nanoparticles using Sodium borohydride (NaBH 4 ) as reducing agent. The effects of NaBH 4 concentration on the particle size and morphology of the Au and Ag nanoparticles have also been studied.

A detailed conductive atomic force microscopic investigation is carried out to directly image the electron emission behavior for nitrogen-doped diamond nanorods (N-DNRs). Localized emission measurements illustrate uniform distribution of high-density electron emission sites from N-DNRs. Emission sites coupled to nano graphitic phases at the grain boundaries facilitate electron transport and thereby enhance field electron emission from N-DNRs, resulting in a device operation at low turn-on fields of 6.23 V/mu m, a high current density of 1.94 mA/cm(2) (at an applied field of 11.8 V/mu m) and a large field enhancement factor of 3320 with a long lifetime stability of 980 min. Moreover, using N-DNRs as cathodes, a microplasma device that can ignite a plasma at a low threshold field of 390 V/mm achieving a high plasma illumination current density of 3.95 mA/cm2 at an applied voltage of 550 V and a plasma life-time stability for a duration of 433 min was demonstrated.

This work demonstrates the applicability of one-dimensional nitrogen-doped diamond nanorods (N-DNRs) for the simultaneous electrochemical (EC) detection of Pb2+ and Cd2+ ions in an electrolyte solution. Well separated voltammetric peaks are observed for Pb2+ and Cd2+ ions using N-DNRs as a working electrode in square wave anodic stripping voltammetry measurements. Moreover, the cyclic voltammetry response of N-DNR electrodes towards the Fe(CN)(6)(/4-)/Fe(CN)(6)(/3-) redox reaction is better as compared to undoped DNR electrodes. This enhancement of EC performance in N-DNR electrodes is accounted by the increased amount of sp(2) bonded nanographitic phases, enhancing the electrical conductivity at the grain boundary (GB) regions. These findings are supported by transmission electron microscopy and electron energy loss spectroscopy studies. Consequently, the GB defect induced N-DNRs exhibit better adsorption of metal ions, which makes such samples promising candidates for next generation EC sensing devices. (C) 2018 Elsevier Ltd. All rights reserved.

Lack of control on the chirality or diameter of single-wall carbon nanotubes (SWCNTs) during synthesisis a major impediment in the path of their widespread commercialization. We demonstrate that the humble technique of catalytic chemical vapor deposition of methane, without any sophisticated catalyst preparation, can provide significant control on the diameter of the synthesized SWCNTs. The catalyst used is a solid solution of the bimetals Fe-Mo or Co-Mo in MgO. The radial breathing modes (RBMs) in the Raman spectra of SWCNTs were used to find out the diameters. Kataura plot along with RBMs was used to study the chirality of the tubes. High concentration of the catalysts (Co: Mo: MgO = 1:0.5: 15 and Fe: Mo: MgO = 1: 0.5: 30) resulted in high yields. However, most of these carbonaceous materials were impurities. Reducing the concentration not only improved the purity and crystallinity (I-D/I-G ratio similar to 0.1), but most importantly reduced the diameter spread of the SWCNTs. Majority of the SWCNTs grown using the low concentration catalysts (Co: Mo: MgO = 1: 0.5: 300 and Fe: Mo: MgO = 1: 0.5: 200) were estimated to have diameters lying between 1.13 and 1.65 nm. This narrowing of diameter spread happened for both Fe and Co catalyst systems and depended only on the concentration of the catalyst. (C) 2014 Elsevier B.V. All rights reserved.

The North Eastern Region of India is one of the richest reservoir of genetic variability and diversity of different horticultural crops that exists in plant type, morphological and physiological variations, reactions to diseases and pests, adaptability and distribution. The region spreads over an area of 2,620,230 km2 (8% of country’s geographical area) and consists of eight states. The region presents most diverse conditions for fruit growing in terms of slopes, altitudes, agro-climatic conditions and soil types etc. The altitudinal differences coupled with varied physiography contributes to great climatic variations in NE India, from near tropical to sub-alpine and sub-tropical climate. The soil of the region is rich in organic matter and is acidic to strongly acidic in reaction. The widely diverse agro-climatic conditions along with other physiographic conditions have led to immense variability among fruit crops in the region. According to National Horticulture Board, the area, production and productivity of fruit crops in the region in 2010-2011 were 412,000 ha, 3,432,100 t and 8.33 t/ha, respectively. Apart from major subtropical fruits like citrus, pineapple and banana, many temperate fruits like apple, peach, plum, strawberry, passion fruit and kiwifruit are grown in this region. Besides, major fruit species, the region is a treasure trove for many underutilized temperate fruit crops such as Persea americana, Pyrus pashia, P. indica, Prunus nepalensis, P. jenkinsii, P. avium, P. cerasus, P. serotina, Rubus ellipticus, etc. Many of these fruits are rich in nutrients and medicinal properties and have immense potential to contribute location specific food production, as they are well adapted to existing and adverse environmental conditions. Apart from providing diversification of the food base, different indigenous fruit species produce at different times of the years, ensure year round supply of nutrition. Furthermore, these crops have long been a traditional part of cropping systems. Utilization of bio resources through conventional and biotechnological interventions, development of agro-ecological zone specific farming system involving underutilized fruit crops, infrastructural development including processing, storage, transport and marketing, export oriented production programmes and border trade involving high value fruit crops and prevention of genetic erosion in non-traditional fruit species would boost fruit production in the region.

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.

Due to the fact that much of the world's best solar resources are inversely correlated with population centers, significant motivation exists for developing technology which can deliver reliable and autonomous conversion of sunlight into electricity. Thermoelectric generators are gaining incremental ground in this area since they do not require moving parts and work well in remote locations. Thermoelectric materials have been extensively used in space satellites, automobiles, and, more recently, in solar thermal applications as power generators, known as solar thermoelectric generators (STEG). STEG systems are gaining significant interest in both concentrated and non-concentrated systems and have been employed in hybrid configurations with solar thermal and photovoltaic systems. In this article, the key developments in the field of thermoelectric materials and on-going research work on STEG design conducted by various researchers to date are critically reviewed. Finally, we highlight the strategic research directions being undertaken to make highly efficient thermoelectric materials for developing a cost-effective STEG system, which could serve to bring this technology towards commercial readiness.

Vertically aligned few layered graphene (FLGs) nanoflakes were synthesized by microwave plasma deposition for various time durations ranging from 30 to 600 s to yield graphene films of varying morphology, microstructure and areal/edge density. Their intrinsic electrochemical properties were explored using Fe(CN)6 3−/4− and Ru(NH3)6 3+/2+ redox species. All the FLG electrodes demonstrate fast electron transfer kinetics with near ideal ΔEp values of 60–65 mV. Using a relationship between electron transfer rate and edge plane density, an estimation of the edge plane density was carried out which revealed a moderation of edge plane density with increase in growth time. The pristine FLGs also possess excellent electrocatalytic activity towards oxygen reduction reaction (ORR) in alkaline solutions. This ORR activity can be further enhanced by exposing the pristine FLGs to nitrogen electron cyclotron resonance plasma. The metal free N-doped FLGs exhibit much higher electrocatalytic activity towards ORR than pristine FLGs with higher durability and selectivity than Pt-based catalysts. The excellent electrochemical performance of N-doped FLGs is explained in terms of enhanced edge plane exposure, high content of pyridinic nitrogen and an increase in the electronic density of states.

The capillary flow in SU8 based microfluidic devices fabricated in SF-100 by lithographic technique has been recorded and analysed in this report. Leakage free microfluidic flow is achieved by indirect bonding between polymethyl methacrylate (PMMA) coated glass lid surface and SU8 channel substrate during hard baking. The working liquids are dyed ethylene glycol, dyed ethanol, dyed isopropyl alcohol (IPA) and dyed liquid mixture (water and IPA). The capillary flow of dyed ethylene glycol is found to be slower in each device due to higher viscosity and lower surface wettability as compared to other working liquids. Square SU8 micropillar arrays (80 μm and 120 μm of side lengths) are fabricated on the glass bottom wall surface of SU8 based microchannel. The capillary flow of any particular working liquid is observed to be faster through the square micropillars of smaller side length due to their lower surface area to volume ratio in the device. Also, the capillary flow of polar liquids is found to be faster on the microchannel surface of higher polar component of surface free energy. The above results are highly significant to control the speed of capillary flow in lab-on-a-chip systems.

The simulation of counter-current capillary imbibition displacement in a fractured porous medium is performed using a two-color Lattice Boltzmann Model (LBM). The kerosene–water interface development is studied at the pore-scale, and the saturation profiles are compared with core-scale experimental results by Hatiboglu and Babadagli (2008) . An additional simulation is performed for a relatively larger porous system, which displays a relatively stable saturation growth. A relative permeability curve is obtained for the counter-current displacement process and it is compared with the corresponding co-current situation. The relative permeability of non-wetting (oleic) phase shows a concave nature i.e., initial increase followed by a subsequent decrease. Such a trend can be explained by the fact that the resident oil is displaced more easily in the initial water saturation stages until the peak of the relative permeability curve, after which the presence of water hinders further displacement of the trapped oil. Further, counter-current relative permeability curves are obtained for different values of equilibrium contact angles and interfacial tensions. The model can be used as a basis for further LBM counter-current simulations and to study the qualitative and quantitative nature of this physical process. Likewise, the relative permeability curves obtained can be useful data and provides qualitative insights in the simulation of waterflooding in naturally fractured reservoirs.

Atomically engineered oxide heterointerfaces show a range of novel phenomena not present in their bulk form, thus providing an additional knob to tune the functional properties across such interfaces. Here we show that for an oxide Schottky interface between metallic SrRuO 3 and semiconducting Nb doped SrTiO 3 (Nb:STO) the terminating surface of the substrate plays a crucial role in determining the electronic transport across it. Interestingly this is achieved by engineering a monolayer of a charge-neutral SrO layer across the Schottky interface and not by the insertion of charged layers at the interface, as has been demonstrated earlier. These changes in the energy-band line-up across a symmetric interface indicate the presence of different polar characters at the SrO and TiO 2 terminations of the substrate. Owing to the presence of the same AO layer (SrO) in both SrRuO 3 and Nb:STO, we propose an intermixing of Ru and Ti ions across the interface for the SrO terminated Nb:STO substrate. First-principles density functional theory calculations on these systems conform with our experimental findings, and indicate a resultant shift in the interfacial atomic plane stacking of SrRuO 3 at the intermixed interface, leading to a modification of the electrostatic potential at the interface. The interdependence between the interfacial band alignment to the local atomic plane displacement across an intrinsically nonpolar oxide heterointerface is a key mechanism in realizing novel electronic properties in oxide based devices.

Chemical and Materials Engineering Department, University of Alberta, Edmonton, Alberta T6G 2V4, CanadaDifferent shapes and sizes of multiwalled carbon nanotubes (MWCNTs) were prepared by the thermal chemicalvapor deposition (CVD) process using ferrocene and toluene on conducting (cobalt/silicon), semiconducting(silicon) and insulating (quartz) substrates to investigate the change in surface morphology, microstructure andelectron “eld emission properties. The lengths and diameters of the MWCNTs were estimated from the scanningand transmission electron microscopy, revealing that although the lengths were not identical, changing withinm, there was no signi“cant change in diameter. The I

Fly ash samples collected from the hoppers of various electric fields of electrostatic precipitator attached to two different units (1 and 2) of a Super Thermal Power Plant were critically examined in respect of their particle size distribution and shape. Particle size analysis of each of the samples collected over a period of three months from the dust hoppers of seven fields of each unit (unit 1 and 2) reveals that in general ash particles collected from the hoppers of field 1 are coarser and show bimodal distribution. Ashes from hoppers for other fields of electrostatic precipitator are finer. Ashes from unit 2 have a smaller particle size than those of unit 1. The particle size of the ashes decrease along field 1 to field 7 for both units, with field 7 ashes being the finest. Ashes from fields 5–7 of both the units contain significant amounts of ultrafine particles (particle diameter ϕ < 5 μm). Shape analysis reveals that ash particles of fields 1 and 2 are irregular in shape and the rest are...

Microstructural properties of ultrathin (1–10 nm) tetrahedral amorphous carbon (ta-C) films are investigated by Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy, X-ray Photoelectron Spectroscopy, Raman spectroscopy and Atomic Force Microscopy (AFM). The CK-edge NEXAFS spectra of 1 nm ta-C films provided evidence of surface defects (C―H bonds) which rapidly diminish with increasing film thickness. A critical thickness for stabilization of largely sp 3 matrix structure distorted by sp 2 sites is observed via the change of π*C═C peak behavior. Meanwhile, an increase in the film thickness promotes an enhancement in sp 3 content, the film roughness remains nearly constant as probed by spectroscopic techniques and AFM, respectively. The effect of thickness on local bonding states of ultrathin ta-C films proves to be the limiting factor for their potential use in magnetic and optical storage devices.

Surface and bulk properties of the Filtered Cathodic Vacuum Arc prepared nitrogenated tetrahedral amorphous carbon (ta-C:N) films were characterized by X-ray Photoelectron Spectroscopy (XPS), Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), Raman spectroscopy, Atomic Force microscopy and contact angle techniques. An increase in the Nitrogen (N) content of the films is accompanied by a reduction in the sp3 fraction, confirmed via the deconvolution of the C 1 s XPS spectra. Critical Raman parameters such as peak position and peak width of the G band, defect ratio, ID/IG and skewness of the G line were analyzed as a function of N content. ToF-SIMS showed the variance of chemical composition with the increase in the sputtering depth. While some amount of incorporated oxygen and hydrogen were observed for all films; for high N content ta-C:N films signature of CN bonds was evident. Surface energies (both polar and dispersive components) for these ta-C:N films were analyzed in a geometric mean approach. Contact angle measurements using both deionized water and ethylene glycol reveal that upon the insertion of nitrogen into ta-C films, the initial change in the contact angle is sharp, followed by a gradual decrease with subsequent increase in N content. The variation of contact angle with increasing N content corresponds to an increase of the total surface energy with an increase of the polar component and a decrease of the dispersive component.

Vertically aligned few layered graphene (FLG) nanoflakes were synthesised on silicon substrates by microwave plasma enhanced chemical vapour deposition (MPECVD) method. Transmission electron microscopy (TEM) shows that the structures have highly graphitized terminal planes of 1–3 layers of graphene. Raman spectroscopy revealed a narrow G band with a FWHM of ∼23 cm−1 accompanied by a strong G′ (2D) band, with a FWHM of ∼43 cm−1 and an IG/IG′ ratio of 1, which are all the characteristics of highly crystallized few layered graphene. The FLG electrodes demonstrate fast electron transfer (ET) kinetics for Fe(CN)63−/4− redox system with an electron transfer rate, ΔEp, of 60 mV. Platinum (Pt) nanoparticles of ∼6 nm diameter were deposited on as grown FLGs using magnetron DC sputtering for methanol oxidation studies. When used as electrodes for methanol oxidation, a mass specific peak current density of ∼62 mA mg−1 cm−2 of Pt is obtained with a high resistance to carbon monoxide (CO) poisoning as evident by a high value of 2.2 for the ratio of forward to backward anodic peak currents (If/Ib).

Multiwalled carbon nanotubes (CNTs) were grown on silicon substrates by thermal chemical vapour deposition (CVD) and microwave plasma CVD (MPCVD). In this manuscript, an attempt has been made to compare the growth mechanism and electrical and micro-structural properties of CNTs grown by two different methods. CNTs in MPCVD is grown by tip-growth mechanism whereas in TCVD it is grown by base-growth mechanism. To compare these techniques, the CNT samples were examined using scanning and transmission electron microscopy, Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy. Growth rates were 10 and 0.6 μm/min, for thermal CVD and MPCVD, respectively. Diameters ranged from ∼40–60 nm for thermal CVD grown CNTs, and 20–50 nm for MPCVD-grown CNTs. Deposition over 2″ diameter silicon wafers was achieved for the MPCVD growth technique. XRD and Raman studies revealed good crystallinity for both growth methods. However, thermal CVD grown CNTs showed more defects, with a crystallite size of ∼20 nm, compared to ∼37 nm for MPCVD. Static water contact angles of thermal CVD and MPCVD samples were 155° and 136°, respectively, indicating greater hydrophobicity for thermal CVD-grown CNTs. The electrical resistance was 75.40 Ω for MPCVD-grown CNTs, but 782.10 Ω for thermal CVD samples. Field emission studies revealed β values for thermal CVD and MPCVD samples, of 8010 and 13,570, with turn-on fields of 0.96 and 0.60 V/μm, respectively.

The aim of this study is to assess in vitro cytotoxic effects of titania nanostructures and carbon nanotubes (CNTs) by exposing A549 lung epithelial cell line to these materials. Titania nanotubes (TiNTs) were grown by hydrothermal treatment of TiO2 nanoparticles, followed by annealing them at 400 ◦C. The titania nanostructures obtained on annealing (mixture of nanotubes and nanorods) were hollow and open ended, containing 3–5 layers of titania sheets, with an internal diameter ∼3–5nm and external diameter ∼8–10 nm, and a specific surface area of 265m2/g. As-supplied single walled (SWCNTs) and microwave plasma enhanced chemical vapour deposition (MPCVD) grown multi walled carbon nanotubes (MWCNTs) were used in this study. The lengths and diameters of the SWCNTs were 5–10nm and 0.5–3nm respectively. The lengths and diameters of the MWCNTs were 25–30m and 10–30nm respectively. The cell viability was evaluated using the MTT (3-(4,-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium) assay. No significant cytotoxic effects of titania nanostructures were observed over a period of a week of testing time, while the presence of CNTs in some cases demonstrated significant cytotoxic effects. Finally, possible reason of cytotoxicity is discussed in the light of microstructures of materials. © 2011 Elsevier B.V. All rights reserved.

Vertically aligned few-layered graphene (FLG) nanoflakes were synthesized on bare silicon (Si) substrates by a microwave plasma enhanced chemical vapor deposition method. In situ nitrogen (N(2)) plasma treatment was carried out using electron cyclotron resonance plasma, resulting in various nitrogen functionalities being grafted to the FLG surface. Compared with pristine FLGs, the N(2) plasma-treated FLGs showed significant improvement in field emission characteristics by lowering the turn-on field (defined at 10 mu A/cm(2)) from 1.94 to 1.0 V/mu m. Accordingly, the field emission current increased from 17 mu A/cm(2) at 2.16 V/mu m for pristine FLGs to about 103 mu A/cm(2) at 1.45 V/mu m for N-doped FLGs. Furthermore, N-doped FLG samples retained 94% of the starting current over a period of 10 000 s, during which the fluctuations were of the order of +/- 10.7% only. The field emission behavior of pristine and N(2) plasma-treated FLGs is explained in terms of change in the effective microstructure as well as a reduction in the work function as probed by X-ray photoelectron valence band spectroscopy.

In this work, we have developed a polyacrylate-coated graphene-oxide and then chemically reduced them into graphene. We found that polyacrylate coating can improve the colloidal stability of both graphene-oxide/graphene. They show good colloidal stability in different aqueous buffer solution with pH ranging from 5 to 10, and these solutions are stable for more than a month. The polyacrylate-coated grapheme oxide/graphene has been characterized by X-ray photoemission spectroscopy (XPS) and micro-Raman spectroscopy. Based on good colloidal stability, this graphene-oxide/graphene is most suitable for the biological application.

A systematic study is reported of the growth of vertically aligned few layered graphene (FLG) nanoflakes on Si (100) substrates by microwave plasma enhanced chemical vapour deposition (MPECVD) method. Asymmetric grazing incident angle X-ray diffraction (GIAXRD) studies revealed a structural transformation, from nanocrystalline graphite layers to FLG, with the increase of growth time. As the growth time increased we observed a preferred vertical orientation of FLGs accompanied by a sharp decrease in the d002 spacing. Transmission electron microscopy shows these structures have highly graphitized edge planes which terminate in a few layers (1–3) of graphene sheets. Detailed Raman studies not only support the structural transformation but also confirm that the process occurs via the sudden release of stress in nanocrystalline turbostratic graphite films. Graphical plot of all major Raman parameters (such as G peak position, ID/IG value, FWHM of D, G, and G′ peaks) vs.growth time shows a well defined trend. Using the graphical plots a tentative trajectory of the Raman parameters is proposed, which can be very useful in understanding structural transformation during growth process. Finally, a possible growth mechanism of FLGs is presented.

Single crystalline zinc oxide (ZnO) nanoneedles have been grown on Au coated Si (1 0 0) substrates in an inert gas atmosphere by physical vapor deposition (PVD) process. A mixture of ZnO and graphite powder was used as precursor for the production of nanoneedles. Their structure has been assessed by a range of techniques including scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The synthesized ZnO nanoneedles have tip diameter around 30 nm and average length of ∼5 μm. The XRD patterns and HRTEM measurements revealed the highly crystalline phase of wurtzite single crystalline structure, with a preferred 〈0 0 0 1〉 growth direction. Field emission from these nanoneedles was investigated and a low turn on voltage of 5.07 V μm −1 at a current density of 10 μA cm −2 was observed.

Room temperature transformation from anatase (A-TiO2) to rutile (R-TiO2) thin films through an intermediate mixed phase on stainless steel driven by a controlled oxygen flow rate (OFR) is investigated. Such OFR dependent phase transition is confirmed by X-ray diffraction and also consistent with X-ray absorption spectroscopy at Ti L and O K-edges, showing a long range ordering in TiO6 octahedral symmetry. X-ray photoelectron spectroscopy reveals a gradual reduction in Ti2O3 and/or TiO intermediate phases with increasing OFR. Finally, an enhanced photocatalytic activity is observed in the mixed phase and discussed in terms of photo-generated charge transport in the type-II staggered band structure between A-TiO2 and R-TiO2 phases.

'Co-filled' and 'Fe-filled' multiwall carbon nanotubes (MWCNTs) were grown using microwave-plasma chemical vapour deposition (MPCVD) and thermal chemical vapour deposition (TCVD) methods respectively, and their structural and magnetic properties were studied for magnetic device applications. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show the average tube length approximate to 80-500 mu with outer (inner) diameter approximate to 20-50 (approximate to 10-20) nm for MWCNTs prepared by both methods. The diffraction peaks of both x-ray diffraction patterns show the interlayer distance, d(002) approximate to 3.36 , which is comparable to the graphite structure (d(002) = 3.35 ). The graphitic crystallite sizes (L-a) of MPCVD (TCVD) synthesized MWCNTs are approximate to 24.78 nm (approximate to 22.13 nm) as obtained from the intensity ratio of (I-D/I-G) D-peak, the disordered structure of graphite and G-peak, the C-C bond in graphitic structure of Raman spectra. The magnetization of 'Fe-filled' TCVD grown MWCNTs is much higher than 'Co-filled' MPCVD grown MWCNTs due to the formation of higher content of Fe-C and/or Fe-oxides in the MWCNT structures. The higher magnetic coercivity approximate to 2900 Oe and formation of isolated single-domain Fenanoparticles in 'Fe-filled' TCVD grown MWCNTs, as found from SEM / TEM micrographs, makes the ferromagnetic MWCNTs a promising material for the high-density magnetic recording media.

The present study investigates the patterned growth of carbon nanotubes (CNTs) by microwave plasma assisted chemical vapor deposition (MPCVD) and their field emission (FE) properties. The nanosphere monolayers were used as a mask for deposition of ultrathin (~ 3 nm) cobalt (Co) layer by DC sputtering. Periodic arrays of Co catalyst islands were obtained after the removal of spheres. Microscopic and Raman spectroscopic studies revealed the patterned growth of multiwall CNTs on catalyst islands. The CNTs length was around 10 µm and diameter was of 40–60 nm. The field emission properties were also compared with I–V characteristics of the un-patterned CNTs grown under the same conditions. The onset fields for un-patterned and patterned samples were nearly the same, 0.64 V/µm and 0.67 V/µm, respectively for a 10 µA current.

Vertically aligned carbon nanotube (VACNT) arrays were synthesized using a microwave-plasma-enhanced chemical vapor deposition (MPECVD) system for polymer electrolyte fuel cell (PEMFC) electrode applications. Platinum nanoparticles (Pt NPs) were deposited on as grown VACNT arrays by a DC sputtering system. Pt NPs in the size range of 3–5 nm were formed on the CNT surfaces. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and electron microscopy were employed to study the structural and chemical bonding changes post deposition of Pt NPs. Variable particle density along the nanotube length was observed with cluster formation on tip ends and individual Pt NPs forming farthest away from tip ends. Change observed in the C1s and N1s core level spectra and its possible implications on the Pt/VACNT properties were also discussed.Copyright Elsevier

We explored the hot embossing method for transferring vertically aligned carbon nanotubes (CNTs) into microfluidic channels, fabricated on poly-methyl-methacrylate (PMMA). Patterned and unpatterned CNTs were synthesized by microwave plasma-enhanced chemical vapour deposition on silicon to work as a stamp. For hot embossing, 115°C and 1 kN force for 2 min were found to be the most suitable parameters for the complete transfer of aligned CNTs on the PMMA microchannel. Raman and SEM studies were used to analyse the microstructure of CNTs before and after hot embossing. The PMMA microparticles with dimensions (approx. 10 µm in diameter) similar to red blood cells were successfully filtered using laminar flow through these microfluidic channels. Finally, a microfluidic-based point-of-care device for blood filtration and detection of bio-molecules is drawn schematically.

In this study we fabricated a silicon-based stamp with various microchannel arrays, and demonstrated successful replication of the stamp micro-structure on poly methyl methacrylate (PMMA) substrates. We used maskless UV lithography for the production of the micro-structured stamp. Thermal imprint lithography was used to fabricate microfeatured fluidic platforms on PMMA substrates, as well as to bond PMMA lids on the fluidic platforms. The microfeature in the silicon-based (silicon wafer coated with SU-8) stamp includes microchannel arrays of approximately 30 μm in depth and 5 mm in width. We produced various channels without pillars, as well as with SU-8 pillars in the range of 50–100 μm wide and 6 μm in height. PMMA discs of 1 mm thickness were utilized as the molding substrate. We found 10 kN applied force and 100 °C embossing temperature were optimum for transferring the micro-structure to the PMMA substrate.

Tetrahedral amorphous carbon (ta-C) films were studied with and without applying fixed pulse bias and frequency at variable pulse widths in double bent Filtered Cathodic Vacuum Arc (FCVA) system. Both from Raman and X-ray photoelectron spectroscopy (XPS) analyses it has been observed that the ratio of sp 3 /sp 2 is maximal at pulse width of 15 µs with fixed pulse bias 3 kV and frequency 200 Hz. Increasing or decreasing pulse width from this threshold value accompanies the decreasing sp 3 content in the film. It is also observed that with applying pulse bias width at said frequency and bias voltage G peak position was shifted to lower values and after reaching a minimum at 15 µs G peak position shifted to higher wave numbers. At the 15 µs pulse width, 3 kV bias voltage and 200 Hz frequency we have formed ta-C films with maximum sp 3 content. This study clearly suggests that it is possible to tune the ta-C film's most important properties such as percentage of sp 3 content, internal stress, and hardness by applying pulse width at particular frequency and bias voltage.

The laminar motion of fluid in microchannels is the necessary criteria for integrated microfluidic system as lab-on-a-chip. Experiments were conducted to investigate laminar flow characteristics of dyed water through photoresist microchannels with square pillars. We found that the pillar dimensions on the channel surfaces have significant impact on the flow rate. The evaluated Reynolds number was less than unity in each microfluidic flow. The compatibility between the pillar sizes and corresponding air-water meniscus movement in microfluidic flow has been reported. [DOI: 10.1380/ejssnt.2009.330]

Gel is an intermediate phase of solid and liquid, which exhibits properties of both, and this unique feature of gel has made it an excellent choice as a reaction medium for the nanomaterials synthesis. Herein, we report use of oil swollen surfactant gels as reaction medium and exfoliation medium, for the synthesis of metals (Au, Ag) nanoparticles and graphene, respectively. Confined growth of metals (Au and Ag) nanoparticles, has been achieved by exploring tween 80 based surfactant gel as a reaction medium. Au NPs prepared within tween 80 gel were found to be spherical with size ∼5nm, arranged in template micelles. Heating triggered the growth of Au nanoparticles and particles of various shapes including triangles, rods and pentagonal, were produced. Au and Ag containing tween 80 gels were found to be promising as catalysts for the nitrophenol reduction. Apart from separate synthesis of Au and Ag nanoparticles, bimetallic (Au-Ag) nanoparticles have also been synthesized by taking advantage of selective reducing property of tween 80. First time CTAB gel has been utilized as an exfoliation medium for the quick exfoliation of graphite into graphene sheets, eliminating the necessity of any external driving force such as sonication or heating, to reinforce exfoliation.

We present a comparative study where carbon nanostructures were prepared by electron and ion beam methods. Thin films of 10×10 μm2 area were prepared and analysed by Raman analysis, nanoindentation, energy dispersive X-ray analysis (EDX) and atomic force microscopy (AFM). The material formed is not soft and graphitic, but of intermediate hardness (6–13 GPa) and with Raman spectral features similar to those of hydrogenated amorphous carbon, although it contains a significant Ga content (up to 25 at. %). This study was used to form sharp AFM supertip structures which were used to image sintered ceramic samples and films of aligned carbon nanotubes. Compared to traditional Si tips, this gave an improved rendering of the sample’s aspect ratio although the resolution is limited by the diameter of the C supertips.

The nature of bonding in tetrahedral amorphous carbon nitride (ta-C:N) films deposited by filtered cathodic vacuum arc (FCVA) technique was studied with near edge X-ray absorption fine structure (NEXAFS), X-ray photoelectron and Raman spectroscopies. The interpretation and interrelation of these spectra are discussed. The changes in the local structure were systematically studied as a function of nitrogen content. Deconvolution of the C 1 s and N 1 s XPS spectra shows that the sp 3 –C fraction decreases with an increase in nitrogen content. The π* peak at the C K (carbon K) and at the N K (nitrogen K) edges were systematically studied. Comparison of intensities of the π * peak confirms the formation of CN bond at the expense of CC bond. Analysis of NEXAFS spectra at N K edge revealed as the nitrogen concentration in the films increases, the π */ σ * intensity ratio increases, indicating that there is an increase of the amount of C N bond relative to the C–N bonds. Raman parameters, such as G peak width, I D / I G ratio, skewness of the G line ( Q ), were critically analysed in terms of N content and sp 2 content of the films. We demonstrate that the combined study of normalised Raman, XPS and NEXAFS spectra is very useful in determining the role of nitrogen incorporation in the structure of ta-C films. The hardness values, measured by nanoindentation technique reduced at higher (>7 at.%) N content films.

Amorphous carbon (a-C) films have been produced by unbalanced magnetron sputtering (UBMS) on silicon (Si), aluminium (Al), and chromium (Cr) substrates as a function of substrate bias voltage. The chemical bonding configurations were investigated by Raman and near-edge X-ray absorption fine structure (NEXAFS) spectroscopies. It was found that the structural changes induced by bias voltage are substrate-dependent, revealing the key role of the substrate type on film microstructures. The Raman G peak position and I-D/I-G ratio were strongly dependent on substrate material and negative bias voltage. Negative bias voltage had a small effect on the structure of carbon films on metal substrates (Al and Cr). However, the films on silicon showed significant change in the structure with bias voltage. The intensity and area of pi* peak at the C K (carbon) edge increased with the increase of substrate bias voltage. The NEXAFS analysis was in agreement with Raman observations, which clearly indicated an increase Of sp(2) content with increasing bias voltage. The films deposited in the low-bias voltage regime (50-100 V) showed reduced sp(2) configurations. The possible changes of structure with substrate bias are thoroughly discussed. (c) 2004 Elsevier B.V. All rights reserved.

Tetrahedral amorphous carbon nitride (ta-C:N) films obtained by filtered cathodic vacuum arc deposition have been investigated by Near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The C K (carbon K) edge NEXAFS spectra clearly revealed the increase of C N bonds with the increase of nitrogen concentration. The C K edge NEXAFS analysis further showed that the content of the surface defect (mainly C–H bonds) decreased with the increase of nitrogen in the films. As the nitrogen concentration increased a pronounced change in the π* features were observed at the N K (nitrogen K) edge. The origin of the N K edge π* peaks are mainly due to the formation of C N bonds and nitrogen substitution in the graphite network. Polarization dependent NEXAFS measurements showed an angular distribution of CN bonds. The electrical resistivity of the ta-C:N films decreased at higher nitrogen concentration and this may be from the development of graphite-like structures in these films. The electrical measurements were confirmed further with electrochemical measurements.

Two sets of experiments were carried out for both ta-C and ta-C:N films prepared by filtered cathodic vacuum arc deposition (FCVA). For the first experiment films were prepared as a function of arc current ranging from 30 to 100 A with a film thickness of approximately 70 nm. In the second experiment a series of films was prepared as a function of thickness ranging from 30 to 100 nm at 80 A arc current. Raman studies showed that for ta-C and ta-C:N films, an arc current of 100 A produced films with the lowest sp 2 configurations as well as the highest density values. The effect of thickness on ta-C and ta-C:N films revealed different trends. Raman and XRR analysis identified a decrease in sp 2 content and an increase in density as film thickness was increased for ta-C films. However ta-C:N films exceeding 70 nm showed an increasing trend in sp 2 content whilst a significant drop in density was observed.

In this report, tetrahedral amorphous carbon (ta-C), hydrogenated amorphous carbon (a-C:H), silicon doped tetrahedral amorphous carbon (ta-C:Si:H), and silicon doped hydrogenated amorphous carbon (a-C:H:Si) films with thickness in the range 50–370 nm have been produced by PECVD (Plasma Enhanced Chemical Vapour Deposition) and FCVA ( Filtered Cathodic Vacuum Arc) techniques on Polyethylene terepthalate (PET) and polycarbonate (PC) substrates. The paper is concerned with exploring the links between the atomic structure, gas barrier performance in carbon based films deposited on polymer substrates. A range of techniques including XRR, NEXAFS, Raman, surface profilometry, nano-indentation and water vapour permeation analysis were used to analyze the microstructure and properties of the films. The intensity and area of π* peak at the C K (carbon) edge of the NEXAFS spectra was lower in the FCVA films in comparison to that of PECVD ones confirming the higher sp 3 content of FCVA films. The surface of ta-C films showed a network of micro-cracks, which is detrimental for gas barrier application. However, the surfaces of both ta-C:H:Si and a-C:H:Si silicon-incorporated films were almost free of cracks. We also found that the incorporation of Si into both types of DLC films lead to a significant reduction of water vapour transmission rate.