Search results for "CONDENSED MATTER"
showing 10 items of 13918 documents
Co-reductive fabrication of carbon nanodots with high quantum yield for bioimaging of bacteria
2018
A simple and straightforward synthetic approach for carbon nanodots (C-dots) is proposed. The strategy is based on a one-step hydrothermal chemical reduction with thiourea and urea, leading to high quantum yield C-dots. The obtained C-dots are well-dispersed with a uniform size and a graphite-like structure. A synergistic reduction mechanism was investigated using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The findings show that using both thiourea and urea during the one-pot synthesis enhances the luminescence of the generated C-dots. Moreover, the prepared C-dots have a high distribution of functional groups on their surface. In this work, C-dots proved …
Surfactant-assisted synthesis of Cd1−xCoxS nanocluster alloys and their structural, optical and magnetic properties
2010
We report the synthesis of Co-doped CdS nanoclusters (Cd1−xCoxS) for different doping concentrations (x = 0.10, 0.20 and 0.30) and characterization of their structural, optical, and magnetic properties. The structural properties studied by X-ray diffraction revealed hexagonal-greenockite structure and a decrease of the lattice parameters (a and c) with doping, showing incorporation of Co in the lattice. The morphology of the nanoclusters was studied by scanning electron microscopy. The optical absorption studies, using diffused reflectance spectroscopy, revealed that Co doping modifies the absorption band edge. Ferromagnetic phase was observed in the magnetization measurements at room-tempe…
A new application for nickel foam in alkaline fuel cells
2009
The use of nickel foam as an electrode substrate in alkaline fuel cells (AFCs) has been investigated for bi-polar cells incorporating an electrically conducting gas diffusion layer. This contribution focuses on the cathode, and draws comparisons between nickel foam and nickel mesh substrates. One of the principal electrocatalysts for the cathodic reduction of oxygen is silver, so an improvement in electrochemical performance was obtained by electroplating the nickel foam with silver. The electrodeposition process was optimised to maximise electrochemical performance with a minimum of silver deposited. Nickel foam, which is less expensive than the usual nickel mesh, appears to be a good subs…
Electrochemical characterization of cobalt cordierites attached to paraffin-impregnated graphite electrodes
2004
The electrochemistry of α, β and μ cobalt-containing cordierites (Co2Al4Si5O18) attached to paraffin-impregnated graphite electrodes has been studied by linear scan and cyclic voltammetries in HCl+NaCl and NaOH electrolytes. This electrochemistry is compared with that of vitreous cobalt cordierite, cobalt(II) oxide and cobalt spinel aluminate (CoAl2O4), the two last taken as reference materials. Electrochemical processes involve the site-characteristic reduction of Co(II) species to cobalt metal near to −0.5 V vs. SCE and their oxidative dissolution near +0.3 V, accompanied by solid state interconversion between Co(II) and Co(III) at potentials above +0.45 V. Cordierite-modified electrodes …
Anomalous and normal Hall effect in hydrogenated amorphous Si prepared by plasma enhanced chemical vapor deposition
2010
The double sign anomaly of the Hall coefficient has been studied in p -doped and n -doped hydrogenated amorphous silicon grown by plasma enhanced chemical vapor deposition and annealed up to 500 °C. Dark conductivity as a function of temperature has been measured, pointing out a conduction mechanism mostly through the extended states. Anomalous Hall effect has been observed only in the as-deposited n -doped film, disappearing after annealing at 500 °C, while p -doped samples exhibit normal Hall effect. When Hall anomaly is present, a larger optical band gap and a greater Raman peak associated with Si-H bond are measured in comparison with the cases of normal Hall effect. The Hall anomaly wi…
Structural Changes of Titanium Oxide Induced by Chromium Addition as Determined by an X-Ray Diffraction Study
1995
Abstract An X-ray diffraction study has been carried out on a series of polycrystalline TiO 2 (anatase) catalysts containing Cr(III) at different atomic concentrations (0.2-5.0 at. %), prepared by a co-precipitation method. Analysis of the variation of the unit cell parameters of chromium-doped anatase with respect to pure anatase has allowed us to estimate the solubility limit for the system at around 1.4 at. %. There is no evidence for the existence of a separate crystalline chromium oxide phase. Temperature effects on the cell parameter and on the anatase-rutile transformation rate were also analyzed. An increase in temperature produced release of the chromium from the solid solution. At…
Anion exchange membrane based on alkali doped poly(2,5-benzimidazole) for fuel cell
2012
Abstract The properties of alkali doped poly(2,5-benzimidazole) membrane with different alkali doping levels for fuel cell application are reported in this work. The alkali doping level played an important role for the ion conductivity of the membrane. The ion conductivity significantly increased with alkali doping level. The ion conductivity also increased with the temperature. The ion conductivity of the alkali doped ABPBI membrane (alkali doping level = 0.37), reached to 2.3 × 10 − 2 S cm − 1 at room temperature and 7.3 × 10 − 2 S cm − 1 at 100 °C. The water uptake of the alkali doped ABPBI membrane was increased from 9.1% to 19.2% with increasing alkali doping level at room temperatur…
Monolayer graphene doping and strain dynamics induced by thermal treatments in controlled atmosphere
2018
Time dynamics of doping and strain induced in single layer graphene by thermal treatments up to 300 degrees C in vacuum, nitrogen, carbon dioxide and oxygen controlled atmosphere are deeply studied by Raman spectroscopy and they are compared with its morphological evolution investigated by Atomic Force Microscopy. The reaction dynamics in oxygen treatments is determined down to a time scale of few minutes as well as that of dedoping process made by water vapor treatment. The interplay of strain modification and doping effects is separated. The strain is clarified to be strongly influenced by the cooling time. The doping removal is dominated by the water vapor, showing that the concentration…
A neutron diffraction study of the glass transition in (KBr)0.47(KCN)0.53
1985
Abstract The molecular crystal (KBr) 0.47 (KCN) 0.53 has been investigated by elastic neutron diffraction at the transition from the paraelastic to the orientational glass state. The freezing temperature is characterized by the onset of a momentum transfer dependent broadening of the diffraction lines indicating the transition from a crystalline to an amorphous state.
(Z)-1-Chloro-1-[2-(2-nitrophenyl)hydrazinylidene]propan-2-one
2012
The title molecule, C9H8ClN3O3, lies on a mirror plane. Intramolecular N—H...O and N—H...Cl hydrogen bonds occur. One of the nitro O atoms is disordered (site occupancy ratio = 0.40:0.10).