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Graphene: zinc oxide nanocomposite (GN:ZnO NC) platform was tried for the sensitive determination of para-nitrophenol (p-NP) through the electrochemical method. ZnO nanoparticles (NPs) were synthesized by the modified wet-chemical method where in potassium hydroxide and zinc nitrate were used as precursors and starch as a stabilizing agent. A green and facile approach was applied to synthesize GN:ZnO NC in which glucose was employed as a reductant to reduce graphene-oxide to graphene in the presence of ZnO NPs. The synthesized NC was characterized using scanning and high-resolution transmission electron microscopy, energy dispersive x-ray analysis, X-ray diffraction and Raman spectroscopic techniques to examine the crystal phase, crystallinity, morphology, chemical composition and phase structure. GN:ZnO NC layer deposited over the glassy carbon electrode (GCE) was initially probed for its electrochemical performance using the standard 1 mM K3[Fe(CN)6] model complex. GN:ZnO NC modified GCE was monitored based on p-NP concentration. An enhanced current response was observed in 0.1 M phosphate buffer of pH 6.8 for the determination of p-NP in a linear working range of 0.09 x10− 6 to 21.80 x10− 6 M with a lower detection limit of 8.8 x 10− 9 M employing square wave adsorptive stripping voltammetric technique at a deposition-potential and deposition-time of -1.0 V and 300 s, respectively. This electrochemical sensor displayed very high specificity for p-NP with no observed interference from some other possible interfering substances such as 2, 4-di-NP, ortho-NP, and meta-NP. The developed strategy was useful for sensitive detection of p-NP quantity in canals/rivers and ground H2O samples with good recoveries.

Palladium nanoparticle–graphene nanosheet composite (PdNP–GN) is demonstrated as an efficient electrode material in energy storage applications in supercapacitors. Palladium nanoparticle (PdNP) decorated graphene nanosheet (GN) composite was synthesized via a chemical approach in a single step by the simultaneous reduction of graphene oxide (GO) and palladium chloride from the aqueous phase using ascorbic acid as reducing agent. The materials were characterized by scanning and high resolution transmission electron microscopy, Raman, X-ray diffraction and energy dispersive X-ray spectroscopy which demonstrate that the metal nanoparticles have been uniformly deposited on the surface of graphene nanosheets. The synthesized material has been analyzed by cyclic voltammetry, electrochemical impedance spectrometry and chronopotentiometry using 1 M KCl as the supporting electrolyte for its application in electrochemical double layer supercapacitors. PdNPs-GN composite showed improved electron transfer kinetics and superior capacitive performance with large specific capacitance of 637 F g−1, excellent cyclic performance and maximum energy and power densities of 56 Wh kg−1 and 1166 W kg−1, respectively at a current density of 1.25 A g−1. This highlights the importance of the synergetic effects of electrochemically efficient Pd nanoparticles and graphene for energy storage applications in supercapacitors.

MoS2/carbon hybrid materials have been shown to be promising non-precious metal electrocatalysts for the hydrogen evolution reaction (HER). However, a facile method for synthesizing them is still a big challenge, let alone patterning them through a design. In this work, we present a novel strategy to synthesize and pattern MoS2/carbon hybrid materials as electrocatalysts for the HER through a one-step direct laser writing (DLW) method under ambient conditions. DLW on citric acid–Mo–S precursors leads to the in situ synthesis of small-sized MoS2 nanoparticles (NPs) anchored to the carbon matrix. Largely exposed catalytically active sites from the MoS2 NPs and the synergetic effect from the carbon matrix make the hybrid materials exhibit superior catalytic performance and stability for the HER in acidic solutions. Through computer-controlled laser beams we can design arbitrary patterns made of these catalysts on targeted substrates, which will open a new route for fabricating on-chip microfuel cells or catalytic microreactors.

Graphene, with its unique 2D nanostructure and excellent electrical, thermal, and mechanical properties, is considered an alternative to carbon nanotubes in nanocomposites. In this study, we present a one step approach for the deposition of iron oxide (Fe2O3) nanoparticles onto graphene sheets through solution mixture. The morphology, crystallinity, and magnetic properties of as-synthesized composites were investigated. It was shown that highly crystalline Fe2O3 nanoparticles were densely and uniformly coated on graphene surface. Magnetic measurements reveal that, as compared to weak diamagnetism of pristine graphene, graphene-Fe2O3 nanocomposites display ferromagnetic behavior with coercivity of 101 Oe, saturation magnetization of 12.6 emu g(-1), and remanent magnetization of 3.13 emu g(-1) at room temperature. The enhanced magnetic performance was attributed to the homogeneous dispersion of Fe2O3 nanoparticles in graphene matrix and such nanocomposites are promising materials for applications in magnetic media and energy storage.

Graphene nanosheets (GN) dispersed with macroporous copper oxide (macroCuO) was investigated as an electrode material for supercapacitors. A facile and cost-effective synthesis approach was used to prepare macro-structured porous copper oxide monoliths via modified Sol–Gel route. 1, 3, 5-trimethylbenzene was used as an organic structural directing agent to enhance the pore size, pore volume, pore density and surface area of the resulting CuO hybrid templated with Pluronic P-123. GN/macroCuO nanocomposite was prepared by ultrasonication of the GN and macroCuO. The macroCuO and GN/macroCuO nanocomposite were characterized using various surface analytical techniques. Electrochemical performance of the composite electrode was investigated using cyclic voltammetry and chronopotentiometry. GN/macroCuO/GCE showed pseudocapacitance behaviour due to the Faradaic type of capacitance involving redox process between Cu (0) and Cu (II) of porous copper oxide network. Electrochemical measurements revealed the maximum specific capacitance, energy density and power density of 417 F g−1, 58 Wh kg−1 and 17.85 kW kg−1, respectively for the supercapacitor based on GN/ macroCuO nanocomposite electrode at a current density of 0.9 A g−1. The fabricated supercapacitor device exhibited excellent cycle life with 91.4% of the initial specific capacitance retained after 1000 cycles. The results suggest that the hybrid composite is a promising supercapacitor electrode material.

In order to synthesize defect free, highly crystalline single phase nanostructured bismuth chalcogenides, we have investigated the effects of several reaction conditions including, solvents, temperatures, reaction time, and reducing agents. A small variation in the reaction method resulted in Bi2Te3 with different morphologies, ranging from nanosize particles, rods, platelets, and tubes to nanosheets. The materials were characterized by powder X-ray crystallography, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray analysis, Raman spectroscopy, and four-probe current (I)–voltage (V) analysis. An optimized reaction condition allowed the synthesis of single-phase, impurity-free hexagonal nanoplates with size varying between 50 nm and 500 nm and thickness varying between 45 nm and 55 nm in a reproducible manner. The Raman spectra of the optimized hexagonal plates and sheets showed infra red (IR)-active modes around 118 cm−1 resulting from symmetry breaking, a characteristic feature of nanostructured Bi2Te3. Additional peaks at 94 cm−1 in the nanosheets, resulting from the surface phonon mode further confirmed the ultrathin Bi2Te3 structures. The I–V measurements on the optimized surface showed an n-type semiconducting behavior. The surface current measured as a function of applied voltage is two orders of magnitude higher than that across the stacked pellet in ambient conditions and much higher compared to previously published data on few quintuplet-thick Bi2Te3 nanofilms. The highlights of this study are the optimal solvothermic reaction conditions and their impact on obtaining defect free, highly crystalline single phase bismuth chalcogenides.

We demonstrate electron transport characteristics of newly synthesized NiO nanoparticles on p-type Si substrate using scanning tunneling microscopy (STM). The resistivity and conductivity were determined to be 1.7×104 Ω.cm and 5.8×10−5 Ω.cm for Ni(OH) 2 and 3.1×105 Ω.cm and 3.2×10−6 Ω.cm for NiO, respectively. Additionally, we also exemplify the characteristics features of graphene flakes with NiO nanoparticles on Si substrate through STM. The results of this study show that hydrothermally synthesized NiO can have useful applications in conductor and semiconductor industries.

Here we report evidence of enhanced magnetic properties of carbon nanotubes (CNTs) and multilayer graphene (MLG) decorated with Co 3 O 4 nanoparticles (NPs). These 1∶1 CNTs/Co 3 O 4 and MLG/Co 3 O 4 nano-composites were prepared by a one-step ultrasonic treatment in sodium dodecylbenzene sulfonate (SDBS) surfactant. Structure and morphology of the composites were verified using X-ray diffraction, scanning and transmission electron microscopy, and Raman spectroscopy. Magnetization (M) vs. magnetic field (H) measurements at room temperature in H up to 2.5 kOe showed that the measured M= MS at 2.5 kOe in both the CNT/Co 3 O 4 and MLG/Co 3 O 4 nanocomposites is enhanced by a factor of about 2.5 as compared to MS expected from the simple addition of MS measured for the two components of the nanocomposites. This is surprising since Co 3 O 4 is a paramagnet at room temperature. These enhanced magnetic properties in the nanocomposites likely result from contributions from Co3+ ions which being in the low-spin S=0 state are non-magnetic in pristine Co 3 O 4 but become magnetic in the reduced crystalline symmetry of the interface layers in CNTs/Co 3 O 4 and MLG/Co 3 O 4 .

A newly developed “interrupted creep” experiment has been used to study the physical aging of a low molecular weight polystyrene, Tg∼69 °C. The results of the new experiment are compared to those obtained from traditional “periodic creep” experiments. The interrupted creep experiment provides information about the viscosity, the recoverable creep compliance and the steady-state compliance, Js, during aging. Low molecular weight polystyrene was chosen because it exhibits a steady-state compliance that is a strong function of temperature. Aging was conducted at three temperatures, 68.2, 65.7 and 61.0 °C, using both down-jump and up-jump experiments. The behavior observed in the new experiments mirrors the behavior observed in the traditional experiments. In addition, the new experiments allow the first ever determination of how Js evolves during aging. The change of Js with aging time was calculated using the relationship between the shift factors, obtained from the recoverable creep compliance data, and th...

Anisotropic diamagnetism of pristine graphite and graphene is well known. Here, evidence of significant induced ferromagnetism in multilayer graphene (MLG) decorated with ferrimagnetic Fe3O4 particles is reported. This MLG-Fe3O4 nano-composite was prepared by a one-step ultrasonic treatment at 75 °C in the surfactant sodium dodecyl-benzene-sulfonate. To verify the phase structure and morphology of the composite, X-ray diffraction, scanning and transmission electron microscopy, scanning tunneling electron microscopy, and Raman spectroscopy were employed. Room temperature data of magnetization versus magnetic field showed that the saturation magnetization MS = 58.6 emu/gm for pristine Fe3O4 increased to MS = 158.4 emu/gm for a 1:1 composite of Fe3O4 to MLG. These results lead to induced MS = 253 emu/gm in MLG resulting from its proximity to Fe3O4. Similar experiments on Fe3O4 to single walled carbon nanotubes (SWNT) composite did not show any induced magnetism in SWNT.