Rice husk (RH) has now become a source for a number of silicon compounds, including silicon carbide, silica, silicon nitride, silicon tetrachloride, zeolite, and pure silicon. The applications of such materials derived from rice husks are very comprehensive. The methods of synthesizing these silicon-based materials from RHs and their applications are reviewed in this paper.

Silicon-Based Materials from Rice Husks and Their Applications

Space charge regions in solid two-phase systems and their conduction contribution—I. Conductance enhancement in the system ionic conductor-'inert' phase and application on AgC1:Al2O3 and AgC1:SiO2

Photocatalysis represents a unique class of chemical transformations. It utilizes the energy delivered by light and drives reactions that are difficult, sometimes even impossible, to carry out in dark. When used for thermodynamically uphill reactions such as photosynthesis, photocatalysis promises a sustainable solution to large scale solar energy storage. Despite the longstanding interest in this process and research efforts, existing photocatalysis demonstrations are limited to academic laboratory settings. Chief among the reasons for the slow progress is the lack of suitable photocatalyst materials for large scale applications. For the purpose of effective light absorption, charge separation, and charge transfer, a large number of photocatalytic materials, including conventional semiconductors and emerging photoelectronic materials such as nanoscale plasmonic metal particles, quantum dots, and 2D materials, have been studied. This Review is written to summarize these recent efforts from a broad materia...

Photocatalysis: From Fundamental Principles to Materials and Applications

Chalcogenide films with reversible amorphous-crystalline phase transitions have been commercialized as optically rewritable data-storage media, and intensive effort is now focused on integrating them into electrically addressed non-volatile memory devices (phase-change random-access memory or PCRAM). Although optical data storage is accomplished by laser-induced heating of continuous films, electronic memory requires integration of discrete nanoscale phase-change material features with read/write electronics. Currently, phase-change films are most commonly deposited by sputter deposition, and patterned by conventional lithography. Metal chalcogenide films for transistor applications have recently been deposited by a low-temperature, solution-phase route. Here, we extend this methodology to prepare thin films and nanostructures of GeSbSe phase-change materials. We report the ready tuneability of phase-change properties in GeSbSe films through composition variation achieved by combining novel precursors in solution. Rapid, submicrosecond phase switching is observed by laser-pulse annealing. We also demonstrate that prepatterned holes can be filled to fabricate phase-change nanostructures from hundreds down to tens of nanometres in size, offering enhanced flexibility in fabricating PCRAM devices with reduced current requirements.

Solution-phase deposition and nanopatterning of GeSbSe phase-change materials.

Extending the absorption to the visible region by tuning the optical band-gap of semiconductors and preventing charge carrier recombination are important parameters to achieve a higher efficiency in the field of photocatalysis. The inclusion of reduced graphene oxide (rGO) support in photocatalysts is one of the key strategies to address the above-mentioned issues. In this study, rGO supported AgI-mesoTiO2 photocatalysts were synthesized using a sonochemical approach. The physical effects of ultrasound not only improved the crystallinity of AgI-mesoTiO2 but also increased the surface area and loading of the AgI-mesoTiO2 nanocomposite on rGO sheets. The low intense oxygen functionalities (C-O-C and COOH groups) peak observed in the high resolution C1s spectrum of a hybrid AgI-mesoTiO2-rGO photocatalyst clearly confirmed the successful reduction of graphene oxide (GO) to rGO. The interfacial charge transfer between the rGO and the p-n junction of heterostructured photocatalysts has decreased the band-gap of the photocatalyst from 2.80 to 2.65 eV. Importantly, the integration of rGO into AgI-mesoTiO2 composites serves as a carrier separation centre and provides further insight into the electron transfer pathways of heterostructured nanocomposites. The individual effects of photo-generated electrons and holes over rGO on the photocatalytic degradation efficiency of rhodamine (RhB) and methyl orange (MO) using AgI-mesoTiO2-rGO photocatalysts were also studied. Our experimental results revealed that photo-generated superoxide (O2(-)˙) radicals are the main reactive species for the degradation of MO, whereas photo-generated holes (h(+)) are responsible for the degradation of RhB. As a result, 60% enhancement in MO degradation was observed in the presence of rGO in comparison to that of the pure AgI-mesoTiO2 photocatalyst. This is due to the good electron acceptor and the ultrafast electron transfer properties of rGO that can effectively reduce the molecular oxygen to produce a large amount of reactive O2(-)˙ radicals. However, in the case of RhB degradation, h(+) is the main reactive species which showed a slightly increased photocatalytic activity (12%) in the presence of rGO support where the role of rGO is almost negligible. This study suggests the effective roles of rGO for the degradation of organics, i.e., the rate of photocatalytic degradation also depends on the nature of compound rather than rGO support.

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Carrier separation and charge transport characteristics of reduced graphene oxide supported visible-light active photocatalysts.

Large grain polycrystalline silicon from rice husk

Ionic conductivity and dielectric measurements in single crystal β-AgI

Silver halides are notable for exhibiting both ionic and electronic conductivity which is responsible for their widespread use in photography. Due to differences in ionicity and bonding, their properties vary from the highly ionic silver fluoride to the more covalent silver iodide. These fundamental properties such as defect formation energies, carrier mobilities and band-structures, particularly of silver iodide, have only recently been determined. One interesting finding is the presence of high surface fields, caused by differences between interstitial and vacancy formation energies, which results in separation of photo-generated electron hole pairs. This throws new light on the photographic process and on the suitability of silver bromide as a photographic material.a-AgI is also the first fast ion conductor to be discovered. Structural instability, low defect formation energy and optimum cation size are responsible for this phenomenon but existing models fail to explain all the experimental results. Recent microwave conductivity and neutron scattering experiments which provide fresh insight are discussed.

/pdf/physics-of-silver-halides-and-their-applications-34o23v94yl.pdf

Physics of silver halides and their applications

Electrical and optical properties of amorphous semiconducting GeSe and GeSbSe films

A two-chip analog micropower hearing aid circuit is developed which is based on a low voltage three micron CMOS process. The novel features of the circuit are the use of adaptive biasing of MOS Translinear Loop (MTL) circuit and an innovative application of an adaptive technique in reducing the value of a degenerating linearising resistor in the input differential stage of the AGC block. The above two measures enable reduction of power consumption and external component count. Class-D amplifier provides high conversion efficiency at the output stage. The proposed configuration is now under integration for developing a one chip general purpose CMOS analog hearing aid with capability to operate with 1.0 volt supply voltage.

P.A. Govindacharyulu

Papers

Large grain polycrystalline silicon from rice husk

Ionic conductivity and dielectric measurements in single crystal β-AgI

Physics of silver halides and their applications

Electrical and optical properties of amorphous semiconducting GeSe and GeSbSe films

A micropower analog hearing aid on low voltage CMOS digital process