Rahul Krishna

Facile synthesis of hydrogenated reduced graphene oxide via hydrogen spillover mechanism

Here we demonstrate a single step approach for the facile reduction of graphene oxide (GO) to hydrogenated reduced graphene oxide (HRGO) under ambient conditions.

Resistive switching and activity-dependent modifications in Ni-doped graphene oxide thin films

The resistive switching (RS) mechanism in Ni-doped graphene oxide (GO) devices is studied. We found that RS depends strongly on the fabrication method of the GO sheet and on the electrode material. Resistive switching in GO-devices can be caused by the diffusion of ions from metallic electrode or by the migration of oxygen groups, depending on the fabrication process. We also show that GO-based structures possess activity-dependent modification capabilities, emphasized by the increase/decrease of device conductance after consecutive voltage sweeps of opposite polarity. Our results allow a better understanding of bipolar RS, towards future non-volatile memories and neuromorphic systems.

Hydrogen Storage for Energy Application

The rising population and increasing demand for energy supply urged us to explore more sustainable energy resources. The reduction of fossil fuel dependency in vehicles is key to reducing greenhouse emissions [1-2]. Hydrogen is expected to play an important role in a future energy economy based on environmentally clean sources and carriers. As a fuel of choice it is light weight, contains high energy density and its combustion emits no harmful chemical by-products. Moreover, hydrogen is considered as a green energy, because it can be generated from renewable sources and is non-polluting [3-5].

Carbon Nanotube Based Magnetic Tunnel Junctions (MTJs) for Spintronics Application

Spintronics devices exploiting the spin of the electron [1-10] are prepared to revolutionise the electronics industry. The significance of this new generation device is faster memory and lower power consumption at low electron density. The late 20th century has been considered as an era of microelectronics. However, the avalanche growth of microelectronics is a major threat to Moore’s law and spintronics may be a solution for it. From the first transistor to the signally powerful microprocessor in our recent computers, most electronic devices have employed circuits that express data as binary digits, or bits (1 and 0) represented by the existence or absence of electric charge. Unlike microelectronics, spintronics exploits spin (spin up ↑ and spin down ↓) of the electron to carry information between devices. The discovery of Giant Magnetoresistance (GMR) by Nobel Prize winners Albert Fert and Peter Grunberg had actually led to the birth of novel field spintronics [11]. Currently, most of the existing spintronic devices [12] are based on metallic systems such as magnetic tunnel junctions (MTJs) and single electron transistor [13]. On the other hand, a wealth of intriguing spin phenomena has been observed in nanoscale materials [14]. This triggered an extensive research effort on spin transport in nanoscale MTJs and other interesting phenomena were realised. One of the most important phenomena is tunnel magnetoresistance (TMR) of the MTJs. A MTJ is composed of two ferromagnetic conducting layers separated by an ultra-thin insulating layer [15-20]. The TMR was first demonstrated by M. Julliere [21]. Yakushiji et al. [22] experimentally demonstrated the influence of spin conduction on TMR. The enhancement and oscillation of TMR in ferromagnetic multiple junctions have been predicted by several authors [23-30]. However, there have been only a few experiments on spin-dependent single electron tunnelling (SET) to date [31-36] due to the difficulty in fabricating appropriate sample structures for spin-dependent SET. The desire to build spintronic devices that show larger spin dependent phenomena has led many researchers to combine single electron tunneling (SET) and spin dependent electron tunneling (SDT). The charge quantization in low capacitance magnetic tunnel junctions

Reduction of 4-nitrophenol to 4-aminophenol using a novel Pd@NixB–SiO2/RGO nanocomposite: enhanced hydrogen spillover and high catalytic performance

A nanocomposite catalyst containing palladium–nickel boride–silica and reduced graphene oxide (Pd@NixB–SiO2/RGO, abbreviated as Pd@NSG) was successfully fabricated and its enhanced hydrogen spillover mechanism and high catalytic performance towards reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) is discussed. The structure, composition and morphology of the Pd@NSG nanocomposite were characterized by various techniques. The H2 adsorption experiment directly reveals the spillover effect on the Pd@NSG nanocomposite and its enhanced H2 uptake capacity (0.7 wt%) compared to SiO2/RGO (0.05 wt%) under 50 bar pressure at RT. 4-NP reduction reaction shows remarkably high activity (120 s) of Pd@NSG compared to NixB–SiO2/RGO (7200 s) with excellent stability up to 5 cycles. Both the experiments showed the facile H2 dissociation on the Pd (active sites) activator and subsequent transportation of hydrogen atoms on receptor sites.

Conductivity enhancement and resistance changes in polymer films filled with reduced graphene oxide

The electrical properties of polymer composites based on polycarbonate (PC) and panipol CXM (CX), filled with reduced graphene oxide (rGO), were investigated. The composite preparation conditions allowed good dispersion of rGO in the polymer matrix. We show here that when used as a nanofiller in polymers, rGO offers an appreciable improvement of the electrical current in 3 orders of magnitude (from 10−10 A to 10−7 A at 10 V), as observed in current-voltage (I-V) data for both PC and CX polymers with rGO. The suggested mechanism for the observed switching effects is the migration of oxygen groups aided by both the electrical field and Joule heating. Moreover, some reset- and set- like changes similar to resistive switching were observed in the I-V data of PC and CX-based films upon the addition of rGO. Clockwise (resembling a memristive system type II) and counter-clockwise (resembling a memristive system type I) directions were detected in the I-V data of the analyzed films. According to the obtained resu...