Fabrication of flexible silicon nanowires by self-assembled metal assisted chemical etching for surface enhanced Raman spectroscopy

A homogenous array of flexible gold coated silicon nanowires was fabricated by the combination of nano spheres lithography and metal assisted chemical etching to obtain highly effective Surface Enhanced Raman Spectroscopy (SERS) substrates. 3D nanostructures with different aspect ratios and well-defined geometries were produced by adjusting the fabrication parameters in order to select the best configuration for SERS analysis. The optimum flexible nanowires with an aspect ratio of 1 : 10 can self-close driven by the microcapillary force under exposure to liquid and trap the molecules at their metallic coated ``fingertips'', thus generating hot spots with ultrahigh field enhancement. The performance of these SERS substrates was evaluated using melamine as the analyte probe with various concentrations from the millimolar to the picomolar range. Flexible gold coated SiNWs demonstrated high uniformity of the Raman signal over large area with a variability of only 10% and high sensitivity with a limit of detection of 3.20 x 10(-7) mg L-1 (picomolar) which promotes its application in several fields such food safety, diagnostic and pharmaceutical. Such an approach represents a low-cost alternative to the traditional nanofabrication processes to obtain well ordered silicon nanostructures, offering multiple degrees of freedom in the design of different geometries such as inter-wire distance, density of the wires on the surface as well as their length, thus showing a great potential for the fabrication of SERS substrates

Influence of growth conditions of hydrogenated amorphous silicon carbide on optical properties of the interfacial layer in SiC-based photodevice

The attention has been focused on the optical properties of structures of the form Au/MS/a-Si_{1-x}C_x:H/Si(100)/Al as a function of the deposition temperature of the a-Si_{1-x}C_x:H films. The amorphous SiC:H films were obtained for different temperatures ranging from 150°C up to 500°C. By photoluminescence, blue emission from all the structures was observed at room temperature and a high emission was obtained for sample whose amorphous film was deposited at 500°C. The spectral response of Au/MS/a-Si_{1-x}C_x:H/Si(100)/Al structures with a-Si_{1-x}C_x:H film deposited at 250°C, exhibits a maximum value at λ=950 nm while for structure with a-Si_{1-x}C_x:H film obtained at 150°C, a maximum value of λ was observed at 400 nm

Investigation of the antioxidant potential and total phenolics of Bubonium gravelence aerial parts

Antioxidant potential of aqueous extract of the aerial parts of Bubonium gravelence was evaluated using superoxide and 1, 1-diphenyl, 2-picryl hydrazyl (DPPH) radical scavenging, phosphomolybdenum, reducing power and cyclic voltammetry. In DPPH radical scavenging activity, the IC50 value of the aqueous extract was found to be 0.152±0.05 mg/mL. In the phosphomolybdenum and reducing power tests, the extract has an activity in the order of 19 ± 0.45 and 47.42 expressed as μg of ascorbic acid equivalents per mg of extract, respectively. Moreover, the aqueous extract of Bubonium graveolens showed an antioxidant activity of the radical reduction O2•- in the order of 65.11 ± 1.4 at 1 mg / mL doses, The cyclic voltammetry of the Bubonium graveolens aqueous extract indicates one oxidation irreversible peak at 430 mV/(Ag/AgCl)

Aluminium-induced crystallization of amorphous silicon films deposited by DC magnetron sputtering on glasses

Amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) films were deposited by DC magnetron sputtering technique with argon and hydrogen plasma mixture on Al deposited by thermal evaporation on glass substrates. The a-Si/Al and a-Si:H/Al thin films were annealed at different temperatures ranging from 250 to 550 °C during 4 h in vacuum-sealed bulb. The effects of annealing temperature on optical, structural and morphological properties of as-grown as well as the vacuum-annealed a-Si/Al and a-Si:H/Al thin films are presented in this contribution. The averaged transmittance of a-Si:H/Al film increases upon increasing the annealing temperature. XRD measurements clearly evidence that crystallization is initiated at 450 °C. The number and intensity of diffraction peaks appearing in the diffraction patterns are more important in a-Si:H/Al than that in a-Si/Al layers. Results show that a-Si:H films deposited on Al/glass crystallize above 450 °C and present better crystallization than the a-Si layers. The presence of hydrogen induces an improvement of structural properties of poly-Si prepared by aluminium-induced crystallization (AIC

Optical and spectroscopic characterizations of Algerian silica raw material to predict high quality solar-grade silicon

We assess the potential use as raw material for photovoltaics of Algerian silica samples from the quartz veins of the Tirek deposit and quartz sandstones of the Ain Barda deposit. With 97-98% purity, they all require enrichment before their industrial utilization. Acid leaching and gravimetric separation are used to remove the impurities at the grain boundaries and within the crystal lattice. We obtain course, middle, and fine products. The acid leaching process and the gravimetric separation increase the content of SiO2 up to 99.68%; the residue concentration of iron, alumina and zirconium is decreased to 70, 72 and 58 ppm respectively. These values are in agreement with requirements for silica as raw material destined for solar-grade silicon production. (C) 2016 Elsevier B.V. All rights reserved

Photochemical Conversion of CO₂ into Methyl Alcohol Using SiC Micropowder under UV Light

In our study, microparticles SiC powder was investigated as a catalyst for CO₂ photoreduction into methanol under UV light. The photochemical conversion of methanol was studied as function of time of exposition, the concentration and the grain size of the catalyst. The selectivity of the used catalyst to promote methanol formation was noticed. It was noticed also that the grain size and concentration have a great impact on the photochemical conversion of CO₂ to methanol. The best yield of methanol was achieved when a concentration of 0.75 M of SiC powder of 17 μm grain size and an exposure time to UV light of 2 h where assured. Maximum molar concentration of methanol achieved was under UV irradiation of 365 nm. Therefore, the catalytic property of silicon carbide has proved its efficiency in the photochemical conversion of CO₂ into alcohol thus far under UV light

Lithium-drifted silicon for harsh radiation environments

A model describing the passivation by Li atoms of acceptors arising from radiation damage in Si detectors has been developed. Our studies indicate that it is possible to produce a protocol that will allow the in-situ recovery of lithium-drifted Si particle detectors under irradiation by high-energy particles. Our model for particle damage recovery is supported by preliminary results on the recovery of old, degraded detectors

Effect of electrodeposition duration on the morphological and structural modification of the flower-like nanostructured ZnO

International audienceFlower-like morphology of ZnO thin films were successfully electrodeposited via a one-step route only by changing electrodeposition duration and potential at a fixed concentration on n-Si (100) in 78.10 À4 M Zn (NO 3) 2 , 6H 2 O and 0.1 M KNO 3 solution at 70 C without using any catalyst, additives or seed layer. The as electrodeposited products were characterized by X-ray diffraction, scanning electronic microscopy and photoluminescence. The effects of the electrodeposition potential and duration on the morphology, structure and photoluminescence properties were studied. The results show that the product morphology changes with a change in the applied voltage and electrodeposition duration. Well defined shape of flower-like ZnO morphology was generated under the limited conditions of À1.2 V for 60 min, with (002) preferred orientation. Strong UV emission is obtained in the case of ZnO flower like morphology electrodeposited at À1.2 V for 60 min. The band-gap energy value of ZnO flower-like, determined from optical reflectance spectra, is 3.37 eV