Rami Reddy Devarapalli

High efficiency electron field emission from protruded graphene oxide nanosheets supported on sharp silicon nanowires

Graphene oxide (GO) potentially has applications in vacuum microelectronic devices for realization of field emission displays. Graphene and its derivatives are expected to be efficient field emitters due to their unique electrical properties. However, the flat sheet structure of graphene or GO allows electron field emission only from the edges of graphene and GO nanosheets. In order to extract maximum field emission current density at lower applied voltage from the GO nanosheets, we supported and stretched them on sharp tips of silicon nanowires (SiNWs). Highly efficient and stable field emission with low turn-on field was observed for these SiNW–GO heterostructures. The sharp protrusions created by stretching of the GO nanosheets on SiNWs locally enhance the electric field and thus enhance the field emission characteristics. The dominant use of silicon in electronic devices makes this approach robust for the development of field emission devices using graphene based field emitters.

Vertical arrays of SiNWs–ZnO nanostructures as high performance electron field emitters

Multicomponent hybrid materials of nanostructured building blocks are essential for the development of complex devices and advanced applications due to their role as either functional or interconnecting elements. This study introduces a simple and cost effective strategy for the synthesis of vertical arrays of silicon nanowires and ZnO nanostructures (nanorod and multipod structures). Formation of vertical nanostructured arrays is confirmed by SEM and HRTEM imaging as well as XRD and Raman measurements. We have investigated field emission properties of the as-synthesized vertical nanostructured arrays. Our results show that these SiNWs–ZnO nanostructures are highly efficient and stable field emitters.

Facile Green Synthesis of BCN Nanosheets as High-Performance Electrode Material for Electrochemical Energy Storage.

Two-dimensional hexagonal boron carbon nitride (BCN) nanosheets (NSs) were synthesized by new approach in which a mixture of glucose and an adduct of boric acid (H3 BO3 ) and urea (NH2 CONH2 ) is heated at 900 °C. The method is green, scalable and gives a high yield of BCN NSs with average size of about 1 μm and thickness of about 13 nm. Structural characterization of the as-synthesized material was carried out by several techniques, and its energy-storage properties were evaluated electrochemically. The material showed excellent capacitive behaviour with a specific capacitance as high as 244 F g(-1) at a current density of 1 A g(-1) . The material retains up to 96 % of its initial capacity after 3000 cycles at a current density of 5 A g(-1) .

C@SiNW/TiO2 Core-Shell Nanoarrays with Sandwiched Carbon Passivation Layer as High Efficiency Photoelectrode for Water Splitting

One-dimensional heterostructure nanoarrays are efficiently promising as high performance electrodes for photo electrochemical (PEC) water splitting applications, wherein it is highly desirable for the electrode to have a broad light absorption, efficient charge separation and redox properties as well as defect free surface with high area suitable for fast interfacial charge transfer. We present highly active and unique photoelectrode for solar H2 production, consisting of silicon nanowires (SiNWs)/TiO2 core-shell structures. SiNWs are passivated to reduce defect sites and protected against oxidation in air or water by forming very thin carbon layer sandwiched between SiNW and TiO2 surfaces. This carbon layer decreases recombination rates and also enhances the interfacial charge transfer between the silicon and TiO2. A systematic investigation of the role of SiNW length and TiO2 thickness on photocurrent reveals enhanced photocurrent density up to 5.97 mA/cm2 at 1.0 V vs.NHE by using C@SiNW/TiO2 nanoarrays with photo electrochemical efficiency of 1.17%.

Glucose-Derived Porous Carbon-Coated Silicon Nanowires as Efficient Electrodes for Aqueous Micro-Supercapacitors

In this study, we report on carbon coating of vertically aligned silicon nanowire (SiNWs) arrays via a simple hydrothermal process using glucose as carbon precursor. Using this process, a thin carbon layer is uniformly deposited on the SiNWs. Under optimized conditions, the coated SiNWs electrode showed better electrochemical energy storage capacity as well as exceptional stability in aqueous system as compared to uncoated SiNWs. The as-measured capacitance reached 25.64 mF/cm(2) with a good stability up to 25000 charging/discharging cycles in 1 M Na2SO4 aqueous solution.

Plasmon-enhanced photocurrent generation from click-chemically modified graphene.

The visible-light response of Au nanoparticles (AuNPs) assembled on rGO through different molecular bridges was investigated by transient photocurrent generation. We prepared rGO with two self-assembled monolayers (SAMs), one linear and the other with aromatic triazoles through a click cycloaddition reaction. A fivefold photocurrent enhancement was observed for triazole linkers over the aminopropyltrimethoxysilane (APTMS) linker. Cyclic voltammetry (CV) and impedance measurements also suggest fast electron transfer on account of the low resistance offered by the click-modified rGO surface whereby introduction of triazoles offers the efficient bridge between the donor AuNPs and acceptor rGO.

Quantum dot-decorated silicon nanowires as efficient photoelectrodes for photoelectrochemical hydrogen generation

Quantum dot-decorated wide band gap semiconductors, such as TiO2, ZnO, SnO2, etc., which have electron mobilities of less than 200 cm2 V−1 S−1 have been well studied as the photoelectrodes for photovoltaics and photoelectrochemical water splitting. Herein, we report CdSe quantum dot decorated-silicon nanowires (SiNWs) as photoelectrodes for photoelectrochemical water splitting. SiNWs have a comparatively higher electron mobility than metal oxides. A photocurrent density of around 6.1 mA cm−2 was obtained for the CdSe/SiNWs photoelectrode, which is nearly five times higher than that for SiNWs alone and which also shows a good transient photocurrent response. The band energy level alignment was also studied between Si and CdSe by observing the corresponding flat band potentials from a Mott–Schottky analysis.

Functional silicon nanostructures derived from drying-mediated self-assembly of gold nanoparticles

Self-assembly of nanoparticles is an efficient technique where nanobuilding blocks spontaneously organize into ordered structures by thermodynamic and other constraints. We demonstrate that multifunctional Silicon (Si) nanostructures with unique morphologies like sheets, plates and flakes can be etched chemically by taking an advantage of natural self-assembly of gold nanoparticles (AuNPs) characterized with drying kinetics under external stimuli. We further demonstrated antireflection properties of the as-synthesized Si nanostructures.