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Laser-induced graphene (LIG) on paper substrates is a desirable material for single-use point-of-care sensing with its high-quality electrical properties, low fabrication cost, and ease of disposal. While a prior study has shown how the repeated lasing of substrates enables the synthesis of high-quality porous graphitic films, however, the process-property correlation of lasing process on the surface microstructure and electrochemical behavior, including charge-transfer kinetics, is missing. The current study presents a systematic in-depth study on LIG synthesis to elucidate the complex relationship between the surface microstructure and the resulting electroanalytical properties. The observed improvements were then applied to develop high-quality LIG-based electrochemical biosensors for uric acid detection. We show that the optimal paper LIG produced via a dual pass (defocused followed by focused lasing) produces high-quality graphene in terms of crystallinity

The persistent use of pesticides in the agriculture field remains a serious issue related to public health. In the present work, molecularly imprinted polymer thin films were developed using electropolymerization of pyrrole (py) onto gold microelectrodes followed by electrodeposition for the selective detection of chlorpyrifos (CPF). The molecularly imprinted polymer (MIP) was synthesized by the electrochemical deposition method, which allowed in-line transfer of MIP on gold microelectrodes without using any additional adhering agents. Various parameters such as pH, monomer ratio, scan rate, and deposition cycle were optimized for sensor fabrication. The sensor was characterized at every stage of fabrication using various spectroscopic, microscopic, and electrochemical techniques. The sensor requires only 2 μL of the analyte and its linear detection range was found to be 1 μM to 1 fM. The developed sensor’s limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.93 and 2.82 fM, respectively, with a sensitivity of 3.98 (μA/(μM)/ mm2. The sensor’s shelf life was tested for 70 days. The applicability of the sensor in detecting CPF in fruit and vegetable samples was also assessed out with recovery % between 91 and 97% (RSD < 5%). The developed sensor possesses a huge commercial potential for on-field monitoring of pesticides.

This work demonstrates the applicability of red mud-reduced graphene oxide (RM-rGO) nanocomposites, for the reliable and selective electrochemical detection of arsenic. The new nanocomposite materi...

To improve the production rate of MoS

The aluminum industrial waste red mud was successfully utilized as a novel adsorbent for the removal of arsenic (As) ions from water. The arsenate (As (V)) adsorption efficacy of red mud nanoparticles was also investigated. Red mud nanoparticles were prepared by ball milling raw red mud for 10 h, yielding particles’ size of 20 nm on average. The As (V) adsorption on these nanoparticles strongly depended on the size of the nanoparticles. As (V) removal increased from 58 to 83% by reducing the size of red mud particles from 200 to 20 nm. Detail kinetics and transport study confirmed the pseudo-second-order kinetic process which was governed by external mass transport. The Freundlich (and Langmuir) isotherms confirm that the arsenate adsorption capacity changes from 2.28 mg/g (1.84 mg/g) to 2.54 mg/g (1.96 mg/g) for reduction of particles from size 200 nm to 20 nm. Water filter columns made with red mud nanoparticles prepared by ball milling for 10 h showed better filtration performance than the filter packed with raw red mud. Both the hydraulic conductivity and the As (V) removal (8 mm/h and 61% respectively) of influent 1 mg/L As (V) by red mud nanoparticles were greater than the raw red mud (3.2 mm/h and 54%). The modified red mud column filters also exhibited a higher efficiency than the raw red mud filters to remove Escherichia coli and Staphylococcus aureus from the water. Overall, this research shows that nanomaterials derived from aluminum processing waste can be a promising material for water filtration.

Graphene quantum dots (GQDs) possess excellent optical and electrical properties that can be used in a wide variety of application. Synthesis of hybrid nanoparticles with GQDs have been known to improve the properties further. Therefore, in this method, graphene quantum dots –gold (GQD-Au) hybrid nanoparticles were synthesized using GQDs which reduces HAuCl4.3H2O to Au nanoparticles on its surface at room temperature. The GQDs with self-passivated layers were synthesized by microwave assisted hydrothermal method using glucose as a single precursor. The synthesis process does not involve the use of harmful chemicals. The whole synthesis process of GQD and GQD-Au hybrid nanoparticles takes only five minutes. The synthesized GQDs have been extracted using citrate in order to increase the stability of the hybrid nanoparticles for up to four weeks. The size of the synthesized GQD-Au hybrid nanoparticles is in the range of 5–100 nm and were found to be luminescent under UV-A illumination. The merit of the following method over other synthesis techniques include its rapidity, ease of preparation, and no requirement of elaborate synthesis procedures and/or harmful chemicals. The GQD-Au hybrid nanoparticles can be used in several applications such as luminescent coatings for glass and windowpanes for automobiles, etc. The reducing property of GQDs can further be utilized for the reduction of various metal salts (AgNO3) and organic dyes (methylene blue and methyl orange). . It presents a method/protocol-development of the luminescent GQD-Au hybrid particles of size ~ 5–100 nm. . The GQD-Au hybrid particles find potential applications in luminescent coating applications., Graphical abstract Image, graphical abstract

Free-standing films of graphene oxide (GO) are regarded as potential materials for numerous applications in different fields. However, fabricating macroscopic free-standing GO films with high throughput is a bottleneck in large-scale application of these films. Here we introduce a method suitable for the mass-scale fabrication of free-standing GO films by exploring paraffin film (Parafilm M®) as a sacrificial substrate. The method involves deposition of GO on a paraffin film and peeling of the paraffin film after swelling it with toluene to obtain free-standing film of GO. Furthermore, the GO films were reduced into highly conductive RGO films using a green reducing agent ascorbic acid. A strategy of treating GO films with CuSO4 solution prior to reduction is also designed to avoid the possible disintegration of GO films in ascorbic acid solution. A detailed comparative study on the properties of RGO films prepared via thermal and chemical treatment and through the combination of both is also reported. An investigation of the variation in the electrical conductivity of the RGO films based on the reduction method is also carried out. The hydrophobic nature of the thermally reduced RGO films is explored for the oil/water separation.

Herein, we report the effect of incorporation of two types of plasmonic nanocomposites, TiO2–Au and TiO2–Ag in different ratios, in the TiO2 photoanode of dye-sensitized solar cells (DSSCs). Electrophoretic deposition technique (EPD) has been utilized for the deposition of these nanocomposite photoanodes. The high-resolution transmission electron microscopy reveals that the nanocomposites, TiO2–Au and TiO2–Ag, have a wide size distribution of Au (5–60 nm) and Ag (20–130 nm) nanoparticles embedded in the TiO2 matrix. The UV–Visible absorption spectra of these nanocomposite films reveal the enhancement in the optical density due to the plasmonic effect. The DSSC based on photoanode consists of plasmonic nanocomposite TiO2–Au:TiO2–Ag (3:1 ratio) showed power conversion efficiency (PCE) of 10.9% which is 187% higher than that pristine TiO2 counterpart. The enhancement in the PCE has been confirmed by the photoluminescence and electro-impedance spectroscopy indicating that both Au and Ag play an important role in enhancing the PCE of DSSCs due to the plasmonic effect.

The increasing need of on-demand power for enabling portable low-power devices and sensors has necessitated work in novel energy harvesting materials and devices. In a recent work, we demonstrated the production and suitability of three-dimensional (3-D) spacer all fibre piezoelectric textiles for converting mechanical energy into electrical energy for wearable and technical applications. The current work investigates the textile performance properties of these 3-D piezoelectric fabrics including porosity, air permeability, water vapour transmission and bursting strength. Furthermore, as these textiles are intended for wearable applications, we have assessed their wear abrasion and consequently provide surface resistance measurements which can affect the lifetime and efficiency of charge collection in the piezoelectric textile structures. The results show that the novel smart fabric with a measured porosity of 68% had good air (1855l/m(2)/s) and water vapour permeability (1.34g/m(2)/day) values, good wear abrasion resistance over 60,000 rotations applied by a load of 12kPa and bursting strength higher than 2400kPa. Moreover, the antibacterial activity of 3-D piezoelectric fabrics revealed that owing to the use of Ag/PA66 yarns, the textiles exhibit excellent antibacterial activity against not only Gram-negative bacteria E. coli but they are also capable of killing antibiotic methicillin-resistant bacteria S. aureus.

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 – Exiguobacterium sibiricum strain DR11 and Exiguobacterium undae strain DR14 which showed promising biodegradation potential against polystyrene. In this study, we report the degradation of non-irradiated solid polystyrene material after incubation with these isolates. Growth studies suggested that the Exiguobacterium strains utilize polystyrene as a carbon source. Moreover, our data suggest that polymer degradation was initiated by biofilm formation over the PS surface leading to alteration in the physical properties of the material. Surface property analysis by AFM revealed significantly enhanced roughness resulting in reduced surface hydrophobicity of polystyrene. Fourier-transfer infrared (FT-IR) spectroscopic analysis showed breakdown of polystyrene backbone by oxidation. The extent of deterioration was further determined by percent weight reduction of polystyrene after incubation with bacteria. Our data support the fact that strains of extremophile bacterium Exiguobacterium are capable of degrading polystyrene and can be further used to mitigate the environmental pollution caused by plastics.

We have studied the optimum deposition conditions for the improvement of oxygen and carbon dioxide gas barrier performance of functional diamond-like carbon (DLC) thin films. The a-C:H: a-C:H:Si, a-C:H:N and ta-C:N thin films with 10–400 nm thickness were deposited on polyethylene terephthalate (PET) substrates by the radio frequency plasma-enhanced chemical vapour deposition method. To study the microstructure of the PET coated films, we have used the Raman spectroscopy, X-ray photoelectron spectroscopy, nano-indentation and surface profilometry. The gas barrier property were analysed and found that the a-C:H:N's are 5–10 times better gas barrier properties than that of uncoated PET substrates. These thin layer PET coated thin films could be use in food packaging and biomedical applications.

In this article, we report the modification of the electronic and magnetic properties of few-layered graphene (FLG) nanoflakes by nitrogen functionalization carried out using radio-frequency plasma-enhanced chemical vapor deposition (rf-PECVD) and electron cyclotron resonance (ECR) plasma processes. Even though the rf-PECVD N2 treatment led to higher N-doping levels in the FLG (4.06 atomic %) as compared to the ECR process (2.18 atomic %), the ferromagnetic behavior of the ECR FLG (118.62 × 10–4 emu/g) was significantly higher than that of the rf-PECVD FLG (0.39 × 10–4 emu/g) and pristine graphene (3.47 × 10–4 emu/g). Although both plasma processes introduce electron-donating N atoms into the graphene structure, distinct dominant nitrogen bonding configurations (pyridinic, pyrrolic) were observed for the two FLG types. Whereas the ECR plasma introduced more sp2-type nitrogen moieties, the rf-PECVD process led to the formation of sp3-coordinated nitrogen functionalities, as confirmed through Raman measurem...

The thermal stability and tribological performance of silicon- and oxygen-incorporated diamond-like carbon (DLC) and silicon doped-DLC films were investigated. The DLC and DLC:Si are deposited on various (silicon, stainless steel and aluminium) substrates within the thickness range 200–400 nm by radio frequency plasma-enhanced chemical vapour deposition (PECVD) method. Carbon dioxide (CO2) precursor gas is used to reduce the hydrogen content and to increase the adhesion of the films to the substrate. The X-ray photoelectron spectroscopy, Raman spectroscopy, surface profilometry and nano-indentation are used to study the chemical composition, microstructure, thermal stability and mechanical properties of the films. For CO2 precursor made DLC samples, Raman parameters did not show any significant change up to temperature 500 °C. The lowest coefficient of friction was found to be 0.298 for the DLC:Si film prepared with CO2 at room temperature and corresponded lowest wear rate of 1.77 × 10− 10 mm3/Nm. The micro-structural properties at various annealing temperature were critically analysed by monitoring graphitization behaviour and oxidation of the film surface.

Titania–zeolite Y composites were synthesized by a facile solid-state dispersion method. The synergistic effects of porous zeolite structure and novel photocatalysis properties of titania nanoparticles were exploited. The physical properties of the composites were characterized by scanning electron microscopy, energy-dispersive X-ray, X-ray diffraction, diffuse reflectance spectroscopy, fourier transform infra-red spectroscopy and photoluminescence spectroscopy. Porosity and surface area of the composites were determined from Brunauer–Emmett–Teller studies. The antibacterial effect and the photocatalysis properties of these composites were studied. Composites exhibited higher growth reduction of Escherichia coli and Staphylococcus aureus as compared with the pure forms (P25 titania and zeolite Y). Maximum growth reduction of both types of bacterial cells (gram-positive as well as gram-negative) was observed with 20% titania–zeolite composite. The composite demonstrated 40 and 30% enhancement in the growth reduction of E. coli and S. aureus, respectively, as compared with the pure forms; 10% composite exhibited 50% enhancement in the photocatalysis efficiency of methylene blue dye degradation as compared with P25 titania nanoparticles and led to a complete removal of the dye in the first 60 min of photocatalysis process. Mechanisms for both applications have been proposed in light of the observed results.

Recent studies shows laser-induced graphene (LIG) based electrodes can be very effective for electrochemical sensing applications. In this work, we aim to develop a stable ion selective membrane (ISM) based sweat sensor using laser-induced graphene (LIG) as the electrode material. However, the surface of pristine LIG is hydrophobic. Hence, coating these hydrophobic LIG films with ISM produces low sensitivity in sensing applications. In this study, UV-Ozone irradiated laser-induced graphene (LIG) based electrodes were explored for sensing biomarkers like ion in sweat. Solid-state ion-selective electrodes (ISEs) sensitive to ions were fabricated by a two-step drop-coating process of polyvinyl chloride solution containing plasticizer, ionophore, and ion-exchanger on the LIG electrode. We found the ozone treatment process significantly increased the electrochemical active surface area (EASA) and porosity of the pristine LIG. Hydrophobic to hydrophilic transition induced by UV-Ozone treatment reduced the contact angle (CA), resulting in better permeation of the ion-selective membrane (ISM) into the ozonized LIG film. Raman spectroscopy and IR absorption studies indicate physisorption of ozone on LIG. The concentration of the ISM solution has a great influence on attachment to the O-LIG film. Here, we report the applicability of O-LIG as an electrochemical sensor towards the detection of sodium ion () using the open circuit potential (OCP) method. The performance of ozonized LIG (O-LIG) electrodes was much better than pristine LIG and screen printed carbon electrodes. The sensitivity of 60.2 ± 0.9 mV/ decade to Na+ ions and a lower limit of detection of 1 × 10-6 M was achieved using O-LIG based ISEs. Response time of the O-LIG based electrodes were around 1 min. The current study demonstrates that the LIG-based electrodes can be used as a flexible electrochemical sensing platform and is suitable for future wearable sensing devices. Keywords Laser-induced graphene; ion-selective electrode; wearable sensors; electrochemical sensor; sweat sensor.

3-D vertically aligned few-layered graphene (FLGs) nanoflakes synthesised using microwave plasma enhanced chemical vapour deposition are melt-impregnated with partially reduced graphene oxide-sulfur (PrGO-S) nanocomposites for use in lithium–sulfur batteries. The aligned structure and the presence of interconnected micro voids/channels in the 3-D FLG/PrGO-S electrodes serves as template not only for the high sulfur loading (up to 80 wt%, areal loading of 1.2 mg cm−2) but also compensates for the volume changes occurring during charge–discharge cycles. The inter-connectivity of the electrode system further facilitates fast electronic and ionic transport pathways. Consequently, the binder-free 3-D FLG/PrGO-S electrodes display a high first-cycle capacity (1320 mA h g−1 at C/20), along with excellent rate capability of ∼830 mA h g−1 and 700 mA h g−1 at 2C and 5C rates, respectively. The residual functional groups of PrGO (–OH, –C–O–C– and –COOH) facilitate fast and reversible capture of Li+ ions while confining the polysulfide shuttles, thus, contributing to excellent cycling capability and retention capacity. The 3D electrodes demonstrate excellent capacity retention of ∼80% (1040 mA h g−1 at C/10) over 350 charge–discharge cycles. Comparatively, the 2-D planar PrGO-S electrodes displayed poor electronic conductivity and can only provide 560 mA h g−1 after 150 cycles, thereby further highlighting the vital role of the electrode morphology in improving the electrochemical performance of Li–S batteries.

A novel nanocomposite consisting of π-conjugated 2-aminoterephthalic acid (ATA) coated iron oxide (Fe3O4) nanoparticles and reduced graphene oxide (RGO) has been synthesized using a facile combination of wet-chemistry and low-power sonication. The ATA–Fe3O4/RGO nanocomposites exhibited a high specific capacitance of the order of 576 F g−1; significantly higher than that of pristine Fe3O4 (132 F g−1) and RGO (60 F g−1) counterparts, indicative of a synergistic effect between the ATA–Fe3O4 and RGO components. Furthermore, the maximum energy storage density was calculated to be 75 W h kg−1 (at a current density of 6 A g−1). The charging–discharging analysis showed promising long-term stability with nearly 86% retention of the capacitance after 5000 cycles. The superior capacitive behaviour of these ATA–Fe3O4/RGO nanocomposites is attributed to the synergistic effect of the π-conjugated ATA coating on Fe3O4 which enhances the pseudo-capacitive charge transfer process of Fe3O4 and works in conjunction with the surface functional groups (such as carboxylic, amino and amide) present on the RGO surface, providing enhanced double layer capacitance. Thus, the current system exploits the advantages of both the double layer capacitors and pseudocapacitors in a hybrid structure.

In the present work, the suitability of Aloe vera (AV) as a ‘green reducing agent’ has been investigated for the reduction of graphene oxide (GO). The extent of reduction was studied by varying the amount of AV. The physical and chemical properties of the GO and reduced graphene oxide (rGO) were investigated using UV-Vis spectrophotometry, FT-IR spectroscopy, High Resolution Transmission Electron Microscopy (HRTEM) and Selected Area Electron Diffraction (SAED). Partially reduced graphene oxide sheets obtained with 7.5 g of AV (rGO-7.5) demonstrated a maximum reduction efficiency of about 73% as evident from FT-IR data. Cyclic voltammetry and electrochemical impedance spectroscopy studies revealed a significant enhancement in current density and a decrease in charge transfer resistance for the rGO-7.5 sample. Moreover, the as prepared rGO-7.5 sample showed a remarkable dye removal ability with a maximum efficiency of ∼98%. The enhanced surface area, π–π interaction and strong electrostatic attraction were correlated with the dye removal capability. The adsorption kinetics were also studied and pseudo second order adsorption phenomena were confirmed. The recyclability of the rGO-7.5 sample was further investigated and an excellent desorption capability was established.

Metals (Zr, Zn and Cu) containing oil swollen surfactant gels have been utilized as precursors for the preparation of metal oxides (ZrO2, ZnO and CuO) nanoparticles. No metal alkoxide, external gelating agent or any other intricate molecule have been utilized to reinforce gelation; gel stage has been achieved simply through judicial adjustment of water to surfactant ratio and salinity of the reaction mixture. Unlike, several previously published reports, in this approach surfactant has been added not to just increase the viscosity of solution but it has also formed rod shaped gelatinous micelles in response to the variation in water to surfactant ratio, which endowed mechanical strength to the gel. The effect of nature of metal salt on mechanical properties of gel has also been investigated. Zn and Cu containing cetyltrimethylammonium bromide (CTAB) gels have been found to be strongest and weakest, respectively. Metal containing CTAB gels were heat treated at various temperatures (600, 700 and 800 °C) in order to obtain metal oxides nanoparticles. The effect of calcination temperature on crystallinity, particle size and morphology of the metal oxides nanoparticles has also been investigated. A comparison between ZrO2 nanoparticles prepared using conventional sol gel and oil swollen surfactant gel method has also been carried out in terms of crystallinity, particle size and optical property.

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

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.

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.

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.

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 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.

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.