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Ni(OH)2/reduced graphene oxide (RGO) core-shell hybrid nanostructure has been synthesized employing a facile and inexpensive chemical-precipitation technique. The synthesized core-shell nanostructures, comprising Ni(OH)2 at the core and RGO as shell, were then coated on commercially available Ni foam used as an electrode. Prepared Ni(OH)2/RGO nanospheres were analyzed by Raman analysis for structural information. In the Raman spectrum, the peaks at 1323 and 1612 cm−1 correspond to the D and G bands of RGO, respectively. The peaks at 468 and 335 cm−1 depict the characteristic bands of Ni(OH)2 . The core-shell morphology of the hybrid was established from Transmission Electron Microscope (TEM) images. The lattice fringes are measured to be 0.33 nm for RGO layers and 0.22 nm for Ni(OH)2 core, which correspond to (002) plane of RGO and (101) plane of Ni(OH)2. For electrochemical studies, the as-prepared Ni(OH)2/RGO hybrid was used as a battery-type electrode in supercapacitor. The results indicate that the Ni(OH)2/RGO core-shell hybrid nanostructure exhibits a maximum specific capacity of 513.8 Cg−1 at 10 mV/s with a maximum energy density of 119.4 Whkg−1 at 1250 Wkg−1 power density.

Sharp one-dimensional (1D) and two-dimensional (2D) structures are required for stable and efficient field emission. 1D metal oxide and 1D carbonaceous nanostructure material have been used widely for exciting field emission applications. On the other hand, planar, continuous 2D nanostructures have been less explored, as most often, they offer inefficient field emitters, having high turn-on field and low emission current density. A combination of 1D and 2D nanostructures is expected to improve field emission properties. In the present study, nickel oxide nanostructures were considered as 1D nanostructures, which were synthesized on cleaned, polished, nickel foil substrate by wet chemical treatment through the nano-seed mechanism. Pyramidal shape nanostructures of NiO were found onto nickel substrate. 1D nanostructure, NiO nanostructure, does not show any field emission response. Further, graphene oxide (GO) was used as the 2D nanostructure.) While nickel oxide nanostructure and graphene oxide individually demonstrated very low emission properties, hybrid of these materials show modified surface topography and enhanced field emission properties. The field emission response of graphene oxide on Ni foil shows 6.7 V/μm turn-on field and maximum current density of 28 µA/cm2, whereas graphene oxide on NiO nanostructure has enhanced field emission response. In the case of NiO–GO, the turn-on field and maximum current are 5 V/μm and 173 µA/cm2, respectively. Field emission properties are enhanced further with the reduction of the NiO–GO hybrid and depositing CNT of NiO. The maximum current density of 3.7 mA/cm2was observed for the NiO–CNT hybrid.

Attractive attributes of carbon nanotubes (CNTs),, which include high aspect ratio, excellent electrical and thermal conductivity, high melting point, and longer lifetime, have made this one-dimensional material a promising candidate for next-generation field emitters. In the present work, CNTs were grown directly on copper foil, copper foam, nickel foil and nickel foam through chemical vapor deposition. A comparison between CNT-based two-dimensional emitters, i.e. CNTs synthesized on copper and nickel foils, CNT-based three-dimensional (3D) emitters, i.e. CNTs developed on foams of copper and nickel, have been demonstrated. We observed that CNTs on foams exhibited better field emission compared to CNTs synthesized on foils. This is due to the multistage structure of the 3D foams which provides high surface area for CNT growth and hence enhanced field emission response. In the present work, a CNT sample prepared on nickel foam was observed to exhibit better field emission response compared to the other samples synthesized in the present study. This particular sample demonstrateda very low turn-on field of 0.93 V/µm, excellent field enhancement factor of 13,343 and good stability of electron emission.

The interaction between the metallic substrate and precursor suspension in the electrophoretic deposition (EPD) plays a significant role to reduce graphene oxide (GO) from suspension. Possibility of manipulating this interaction to achieve desired functional properties has been studied in this work. From the Pourbaix diagrams for metals, it was identified that modifying pH of the precursor suspension would result in different situations at the interface of the anodically polarized metallic substrate and graphene oxide (GO) aqueous suspensions. Different values of pH ensure that the metal is either passivated or corroding with varying products, in different pH regions. Such a manipulation of the substrate–suspension interface resulted in significantly different characteristics of the deposited reduced graphene oxide (r-GO) film including morphology, structural characteristics and adhesion strength with the substrate. Also, field emission characteristics of the r-GO films deposited in different conditions were studied. The results showed a distinct possibility for optimizing the field emission properties simply through modifying pH of the suspension. The field emission characteristics of deposited (GO) films could be tailored with deposition parameters.

The present investigation is aimed to find a thread between various surface textures of polycrystalline Cu–Ni alloys, in cold-rolled and annealed conditions, and the nature of graphene, grown by th...

CuO nanostructures were reported for a myriad of applications in diverse areas such as high Tc superconductors, field emitters, catalysts, gas sensors, magnetic storage, biosensors, superhydrophobic surfaces, energy materials etc. In all these applications, structural stability of the nanostructures is very important for efficient functioning of devices with a longer lifetime. Hence, it is necessary to understand the adhesion energy of these nanostructures with their substrates. In this research work, a variety of CuO nanostructures were synthesized directly on Cu foil substrate by varying only the concentration of the reagents. CuO nanostructures, thus grown, were subjected to a nano-scratch test to quantify their adhesion strength with Cu substrate. The adhesion energy was observed to be highest for nanorods and lowest for nanoribbons among all the CuO nanostructures synthesized in this work. Results of this research will be useful in predicting the service life and in improving the efficiency of CuO nanostructure-based devices.

CuO nanorods were synthesized on copper foil substrate through wet chemical approach. The effect of growth time on the field electron emission properties of CuO nanorods was studied. The field electron emission tests were performed under AC bias on the CuO nanorod (CuO NR) samples. The growth reaction time was varied between 1, 3, 7 and 11 h. It was observed that CuO NR sample which was processed for 11 h demonstrates the optimum properties such as lowest turn on field (0.56 V/µm), high current density (1.52 mA/cm2) at low electrical field (9 V/µm), good field enhancement factor and excellent stability of emitters for extended working hours which makes it suitable for applications field emission devices.

Graphene and its derivatives such as graphene oxide (GO) and reduced graphene oxide (rGO) are the potential candidates for high-performance field emission devices owing to their unique geometry and electrical properties. However, flat surface of GO and rGO results in lower field emission efficiency due to emission of electrons only from sharp edges of GO and rGO sheets. In the present study, GO and rGO layers were deposited on both CuO and Cu nanorods (NRs) to enable maximum field emission current density at low applied field via geometrical field enhancement. CuO NRs were synthesized on Cu foil using wet chemical method and Cu NRs were produced through chemical and thermal reduction of CuO NRs. GO layers were deposited on CuO and Cu NRs through dip coating method. GO was converted to rGO through thermal reduction. A comparative study of the field emission properties of CuO, GO@CuO, rGO@CuO, Cu_H 2, GO@Cu_H2, rGO@Cu_H2, Cu_NaBH4, GO@Cu_NaBH4, rGO@Cu_NaBH4 samples was performed. The basic idea behind deposition of GO and rGO sheets on CuO and Cu NRs was to create sharp protrusions in GO and rGO sheets to achieve enhanced field emission properties. Local field enhancement at the apex of sharp protrusions allows tunneling and hence emission of electrons from tips at considerable lower voltage. Highest current density and highest field enhancement factor were obtained in thermally reduced GO@CuO (i.e rGO@CuO) sample.

An increasing number of emitting sites and higher aspect ratios are constantly being added to field emission systems to further improve their properties. Such an ever-growing demand has thrown light on the development of hierarchical field emitters. Tungsten (W) and carbon nanotubes (CNT) have been commonly reported as potential field emitter materials. The present work focused on constructing a hierarchical field emitter structure of CNTs/W nanowires. The structural characterization has been studied using field emission scanning electron microscopy, high-resolution transmission electron microscopy, and x-ray diffraction to confirm the hierarchical structure formation. The carbon nanotube-tungsten nanowire hierarchical structural emitters have demonstrated high current density (31.5 mA cm−2), exceptionally low turn-on field (0.068 V μm−1), and emission stability for more than 152 h. This excellent performance could be related to the formation of a strong as well as the electrically favourable interface between tungsten nanowires and CNTs.

A two-step, low-temperature thermal chemical vapor deposition (CVD) process, which uses camphor for synthesizing continuous graphene layer on Cu substrate is reported. The growth process was performed at lower temperature (800 °C) using camphor as the source of carbon. A threezone CVD system was used for controlled heating of precursor, in order to obtain uniform graphene layer. As-grown samples were characterized by X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM). The results show the presence of 4–5 layers of graphene. As-grown graphene transferred onto a glass substrate through a polymer-free wet-etching process, demonstrated transmittance ~91% in visible spectra. This process of synthesizing large area, 4–5 layer graphene at reduced temperature represents an energy-efficient method of producing graphene for possible applications in opto-electronic industry.

Field emission is a process of electron emission from the surface of a material through quantum tunneling in the presence of an applied electric field. Emission of electrons from a material becomes easy if material is synthesized in the form of nanoscale sharp tips. In the present work, we synthesized one dimensional nanostructures (1-D) such as copper oxide (CuO) nanorods and carbon nanotubes (CNTs) by wet chemical and chemical vapor deposition (CVD) methods, respectively. As the electron field emission (FE) from the flat surface of graphene is challenging, the reduced graphene oxide (RGO) was coated on CuO nanorods and CNTs to prepare RGO based hybrids for field emission. Basic idea to support RGO on 1-D nanostructures was to produce high density sharp protrusions/ridges in RGO sheets. A comparison between the FE characteristics of 1-D nanostructures and RGO based hybrid emitters was performed.

CuO nanostructures were reported for a myriad of applications in diverse areas such as high

Field emitters have found ample variety of applications from field emission displays to high power microwave generators. Though a myriad of materials have been considered for emitter application, carbon nanotubes (CNT) are prominent to offer outstanding field emission characteristics, owing to its nano-dimensions and excellent electrical transport properties. While nano-apex of CNTs aids in achieving high field enhancement factor, its high electrical conductivity ensures minimum resistance to electron flow. Next-generation field emitters demand to show high emission current, at a lower applied electric field, which can be achieved by a three-dimensional (3-D) emitter structure. In this research work, a 3-D hierarchical field emitter structure was synthesized involving carbon nanotubes (CNT) on copper nanowires (Cu NW). Field emission characterization of this hierarchical structure in DC bias showed a low turn-on field of 1.8–2.1 V/µm and maximum current density of 1.84 mA/cm2. CuNW–CNT emitter also demonstrated a remarkable emission stability of nearly 8 h which is very significant for practical applications. Properties of the field emitter CuNW–CNT hierarchical emitter was correlated with its morphology.

Ever since the more-than-decade-old discovery of application of mechanical exfoliation to obtain graphene, this 2-dimensional material was known for its soaring promise in various applications, owi...

Hexagonal boron nitride (BN) is structural analogues to graphitic structure of carbon. Similar to graphene and carbon nanotubes, BN also has nanosheets structure, also known as white graphene and nanotubes structure. These BN nanostructures show excellent properties, such as high stability, mechanical strength and resistant to chemicals. Synthesis of BN nanosheets is easier as compared to synthesis of its 1D nanostructure due its hexagonal layered structure, in which stacks are attached with each other by weak Van der Waals forces. In the present work, synthesis and applications of 1D and 2D nanostructures are discussed. Growth of BN nanotubes on tungsten substrate was performed by using copper as catalyst with a simple and easy method. Synthesis of fluorescent BN nanoflakes was performed using solid precursor, boric oxide and urea for boron and nitrogen, in a high-temperature furnace under argon atmosphere. The product was ultrasonicated in water to get completely stable dispersion of fluorescent nanoflakes as final product. Both The product was then characterized by FESEM, TEM, FTIR. The fluorescence behaviour of BN nanoflakes was also measure and applied for bioimaging of breast cancer cells (MCF-7).

The synthesis of carbon nanotubes (CNTs) was a revolutionary step in the field of nanotechnology. Being structurally analogous to CNTs, boron nitride nanotubes (BNNTs) are also of high interest, specifically for their high mechanical strength and chemical resistance. Compared to CNTs, the synthesis of BNNTs is quite challenging due to the issues related to maintaining stoichiometry and high temperature growth conditions. The selection of the catalyst and a suitable substrate is a major challenge for the growth of BNNTs. Here, we report a novel catalytic growth process of BNNTs, in which copper nanoparticles were chosen as the catalyst and tungsten as the substrate. This combination was found to be promising for the direct synthesis of multiwall BNNTs (MW-BNNTs) on a conducting substrate. This method opens up doors for the direct application of BNNTs in the field of electronics, optoelectronics and piezoelectric devices.

In this study, soda lime glass was reported to use as transparent conducting electrode. Soda lime glass was made conducting with graphene film deposited through simple, low cost, scalable and easy to operate thin film deposition technique. Graphene oxide was dip-coated on soda lime glass, followed by reduction into rGO by thermal annealing in two different atmospheres Ar and Ar+H2 at 500 °C. Bonding strength of GO and rGO (Ar and Ar+H2 treated) with soda lime glass were measured through nanoscratch technique to understand the adhesion behavior of film with substrate. There was no significant effect of reduction atmosphere found on transmittance of the films. However, films, reduced in Ar+H2 atmosphere, showed the low sheet resistance than reduced in Ar only. Highest transmittance of 97.98% and lowest sheet resistance of 12.5×103 Ω/sq were calculated under different processing conditions.

Dissociative chemisorption of CH4/H2 gas mixture during graphene growth was investigated on commercially available Ni and Ni-33wt.% Cu substrates. Catalytic activity of both the substrates was severely decreased by employing very low gas pressure, thereby allowing the examination of very initial stages of dissociative-chemisorption. The chemisorption characteristics of the nickel rich nickel-copper alloy were interestingly found to be similar to those of pure copper, i.e., preferential adsorption of hydrogen over methane. These observations led to an in-depth understanding of the graphene growth mechanism on these substrates.

Reduced graphene oxide coated soda lime glass can act as an alternative transparent/conducting electrode for many opto-electronic applications. However, bonding between the deposited reduced graphene oxide film and the glass substrate is important for achieving better stability of the coating and an extended device lifetime. In the present study, delamination energy of reduced graphene oxide on soda lime glass was quantified by using nanoscratch technique. Graphene oxide was deposited on soda lime glass by dip coating technique and was thermally reduced at different temperatures (100 °C, 200 °C, 300 °C, 400 °C and 500 °C) and treatment time (2 h, 3 h, 4 h, 5 h and 10 h) in Ar (95%) with H 2 (5%) atmosphere. An inverse behavior of delamination energy with temperature and treatment time was observed, which could be correlated with the removal of oxygen functional groups. Sheet resistance of the film demonstrated a steady decay with increasing temperature and treatment time. Functional groups attached to the graphene planes have more influence on conductivity than groups attached to the edges. Removal of functional groups could also be related to optical transmittance of the samples. Knowledge generated in this study with respect to delamination energy, sheet resistance and optical transmittance could be extensively used for various opto-electronic applications.

In order to deal with the challenge of biofilms and its associated infections, it is important to develop some efficient methodology which prevents the formation of biofilms over the surfaces. Herein, we have successfully developed an antibacterial and antibiofilm composite using non-toxic and hydrophobic nanomaterial, graphene nanoplatelets, via facile two step methodology including functionalization and subsequent hydrothermal treatment. The as-prepared composites were characterized using FE-SEM, FTIR and Raman spectroscopy to obtain morphological, compositional and structural details. In addition, the antibacterial efficiency of these composites was investigated against antibiotic resistant S. aureus and E. coli. Afterwards, graphene composite based epoxy coatings were prepared on glass substrate and tested for their antibiofilm efficiency against methicillin resistant S. aureus strain. The abundant presence of hydroxyl groups over the surface due to tannic acid, hydrophobicity of graphene and epoxy and remarkable antibacterial efficiency of tannic acid (TA), silver (Ag) and graphene synergistically enhance the antibiofilm efficiency of such coatings. This work presents a new strategy to develop a multifunctional coating and subsequently lessen the risk of biofilm assisted infections.

In this report, few- and multilayer graphene was fabricated on different substrates by pulsed laser ablation of a highly ordered pyrolytic graphite target under optimized growth conditions, using a pulsed nanosecond Q-switched Nd:YAG laser at 355 nm (3.5 eV). The nondestructive micro-Raman spectroscopic study on our samples has revealed few- and multilayer graphene formation. The number of graphene layers was found to be reduced with the increase in growth temperature. At substrate temperature of 750 °C, the ratio of intensities (I 2D/I G) was calculated from the Raman spectra of the graphene samples to be 0.15 which confirms the multilayer graphene formation, while for graphene film grown at 800 °C, I 2D/I G ratio was 0.27 indicating formation of less than five layers of graphene or few-layer graphene. The thickness of few- and multilayer graphene was also confirmed using atomic force microscopy, whereas the microstructure of few- and multilayer graphene was investigated using scanning electron microscopy. The electrical properties in function of growth temperature were evaluated with two-point probe measurements. This work presents a simple, fast, and controllable alternative effective laser technique to synthesize few- or multilayer graphene.

Black phosphorus (BP) is known to human beings for almost a century. It started receiving more attention of scientists and researchers worldwide in last three years, with its ability to exist in two-dimensional (2D) form, popularly known as phosphorene. In the post-graphene-discovery period, phosphorene is probably receiving most attention, owing to its excellent properties and hence, high potential for practical applications in the field of electronics, energy and infrastructure. In this article, attractive properties of phosphorene, which makes it unique and comparable with graphene or transition metal dichalcogenides (TMDs), are highlighted. As the question of its environmental instability remains critical, a comprehensive overview of synthesis methods of phosphorene and black phosphorus are presented, to inspire in-situ methods of phosphorene synthesis and fabrication towards improving further investigation into this wonder material. In addition, the article also focuses on opportunities in nano-electronics, optoelectronics, energy conversion/storage, sensors etc arising from phosphorene’s remarkable properties.

Graphene nanoplatelets (GNP) reinforced aluminum matrix composites, with ≤5 wt% GNP content, were synthesized by spark plasma sintering (SPS). GNPs were found to withstand severe conditions of high pressure and temperature during processing. Strength of composite was observed to be depending on the content and uniform dispersion of GNP in aluminum matrix, as verified by scanning electron micrographs. X-ray diffraction analysis confirmed that no reaction products exist at Al-GNP interface in significant amount. Instrumented indentation studies revealed improvement in hardness by 21.4% with 1 wt% GNP. This is due to the presence of stronger reinforcement, which provides high resistance to matrix against deformation. Improvement in yield strength and tensile strength was 84.5% and 54.8%, respectively, with 1 wt% GNP reinforcement. Properties deteriorated at higher concentration due to agglomeration of GNP. Reinforcing effect of GNPs, in terms of strengthening of composite, is found to be dominated by Orowan strengthening mechanism. Pinning of grains boundaries by GNPs led to uniform grain size distribution in the composites structure. Overall, graphene reinforcement has offered 86% improvement in specific strength of aluminum matrix.

A variety of CuO nanostructures have been synthesized directly on copper foils by room temperature oxidation of copper through wet chemical method. Alkaline condition necessary for the growth process was maintained by the application of NaOH and NH3 precursors. pH of the solution and reaction time were selected as the process variables. Formation of CuO was confirmed by X-ray diffraction pattern analysis. Evolution of morphologies of the phases formed was characterized by field emission scanning electron microscopy, leading to elucidation of the growth mechanism. Different types of CuO nanostructures were observed to be formed at different process parameters, selected for the present study. Field emission characteristics of CuO nanorods and CuO nanoflakes were also investigated. Emission current density of CuO nanorods and CuO nanoflakes were determined to be 0.90 mA/cm2 and 0.48 mA/cm2, respectively. Huge difference in the emission current density indicates that field emission properties of CuO nanostructures are strongly affected by their morphology.

Exciting properties of carbon nanotube has proven it to be a promising candidate for field emission applications, if its processing cost can be reduced effectively. In this research, a new electrochemical technique is proposed for growing carbon nanotubes in selective areas by thermal chemical vapour deposition. In this process, electrochemical processing is used to create localized pits and deposition of catalysts, which act as roots to support growth and alignment of the CNTs on copper substrate. CNTs grown thus were characterized and studied using scanning electron microscope, transmission electron microscope and Raman spectroscopy, elucidating presence of multiwall carbon nanotubes (MWCNT). These CNT emitters have comparatively lower turn-on field and higher field enhancement factor.

Research on graphene/nanostructure hybrid materials has been gaining momentum in recent years, with wide-ranging applications in gas sensing and detection. Specifically, noble metal decorated graphene-based novel structures were found to be extremely sensitive and selective owing to the synergistic effect of the compound configuration. In this article, recent developments in graphene/noble metal nanostructure hybrids and their promising potential in gas sensing applications has been highlighted. More significantly, an understanding of the electronic mechanism of gas sensing is presented with a specific emphasis on electron transfer and junctions effects at the graphene/nanostructure interfaces. Finally, the future research prospects of application of bi-metallic and tri-metallic nanostructure/graphene-based hybrids and the challenges in this new and rapidly growing domain are discussed.

Here we report application of commercially available soda lime glass as transparent, conducting electrodes. Transparent glass substrate, without any surface preparation, was coated with reduced graphene oxide (rGO), through a simple, scalable, easy-to-operate and low-cost deposition technique to render conductivity to it. The process involved dip coating of graphene oxide (GO) solution on soda lime glass, followed by reduction of GO to rGO by thermal annealing process at 500 °C in Ar or Ar + H2 atmosphere. Though there was no significant effect of atmosphere (Ar or Ar + H2 gases) on the transmittance of the electrode, lower sheet resistance was observed in the films reduced under Ar + H2 cover, as compared to those reduced in only Ar atmosphere. The highest transmittance of 97.98% and lowest sheet resistance of 12.55 × 103 Ω/sq was achieved under different processing conditions. De-bonding energy of GO and rGO (Ar and Ar + H2 treated) with the soda lime glass was also quantified using nanoscratch technique to throw light on the adhesion behavior of the film with the substrate.

This article shows the efficacy of transition metal (Ni) as a top layer on glass in the formation of graphene domain. Graphene films were grown on glass substrates from highly ordered pyrolytic graphite by pulsed laser deposition (PLD), with the help of 250 nm thick Ni thin film. The as-synthesized graphene films were characterized by UV–Vis spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and Optical microscopy. The Raman spectroscopic measurement reveals that catalytic film of Ni enhanced the characteristic 2D-peak of graphene on glass substrate, indicating formation of graphene domain; while similar peaks were not detected in the absence of Ni. Moreover, Raman spectrum has shown less structural disorder in the resulting graphene film with the presence of Ni surfactant. The surface morphology of the as-synthesized graphene film was studied by scanning electron microscopy and optical microscopy. The present study shows an effective and exciting route to obtain high-quality graphene on glass substrates using PLD. Keywords: Graphene, PLD, Raman spectroscopy, UV–visible spectroscopy, SEM, XPS

For more than two decades, carbon nanotubes (CNTs) have shown great potential for a wide range of applications. Several methods are known to synthesize CNTs, though only a few of them are able to produce good quality and economically available CNTs. Chemical vapor deposition (CVD) is one of those methods that produce economically feasible and good quality CNTs onto specific substrates, even with nanopatterning. However, growing CNTs by CVD at temperatures below 700 °C remained a long-time challenge, as this meant keeping a host of low-melting materials out of bounds for direct CNT growth on them. In this work, CNTs have been synthesized directly onto a low-melting, conducting substrate, aluminum, by thermal CVD, at a temperature as low as 550 °C and up to as high as 650 °C (just below the melting point of aluminum). The diameters of the grown CNTs were observed to be influenced by process parameters, e.g., temperature and pressure. The effect of synthesis parameters on CNT diameters was verified by scanning electron microscopy and transmission electron microscopy. The quality of the CNTs was checked by Raman spectroscopy, selected area electron diffraction pattern of transmission electron microscopy, and XPS. It was observed that an increase in temperature and pressure had a significant effect on the diameters of the CNTs. Randomly entangled CNTs were measured to have an average diameter of 28 nm at 550 °C and one atmospheric (760 Torr) pressure, whereas it was observed to be 78 nm at a temperature of 650 °C and pressure of 0.01 Torr. The field emission response, i.e., the turn-on field (2.5 V/μm) and the maximum emission current density (2.17 mA/cm2) of the CNTs synthesized at the temperature of 550 °C and pressure of 1 atm (760 Torr) was found to be excellent.