Optimization of KOH etching process to obtain textured substrates suitable for heterojunction solar cells fabricated by HWCVD

In this work, we have studied the texturization process of (100) c-Si wafers using a low concentration potassium hydroxide solution in order to obtain good quality textured wafers. The optimization of the etching conditions have led to random but uniform pyramidal structures with good optical properties. Then, symmetric heterojunctions were deposited by Hot-Wire CVD onto these substrates and the Quasi-Steady-State PhotoConductance technique was used to measure passivation quality. Little degradation in the effective lifetime and implicit open circuit voltage of these devices (< 20 mV) was observed in all cases. It is especially remarkable that for big uniform pyramids, the open-circuit voltage is comparable to the values obtained on flat substrates.

Progress in a-Si:H/c-Si heterojunction emitters obtained by Hot-Wire CVD at 200°C

In this work, we investigate heterojunction emitters deposited by Hot-Wire CVD on p-type crystalline silicon. The emitter structure consists of an n-doped film (20 nm) combined with a thin intrinsic hydrogenated amorphous silicon buffer layer (5 nm). The microstructure of these films has been studied by spectroscopic ellipsometry in the UV-visible range. These measurements reveal that the microstructure of the n-doped film is strongly influenced by the amorphous silicon buffer. The Quasy-Steady-State Photoconductance (QSS-PC) technique allows us to estimate implicit open-circuit voltages near 700 mV for heterojunction emitters on p-type (0.8 Ω·cm) FZ silicon wafers. Finally, 1 cm 2 heterojunction solar cells with 15.4% conversion efficiencies (total area) have been fabricated on flat p-type (14 Ω·cm) CZ silicon wafers with aluminum back-surface-field contact.

Bulk silica-based luminescent materials by sol-gel processing of non-conventional precursors

The sol-gel synthesis of bulk silica-based luminescent materials using innocuous hexaethoxydisilane and hexamethoxydisilane monomers, followed by one hour thermal annealing in an inert atmosphere at 950oC-1150oC, is reported. As-synthesized hexamethoxydisilane-derived samples exhibit an intense blue photoluminescence band, whereas thermally treated ones emit stronger photoluminescence radiation peaking below 600 nm. For hexaethoxydisilane-based material, annealed at or above 1000oC, a less intense photoluminescence band, peaking between 780 nm and 850 nm that is attributed to nanocrystalline silicon is observed. Mixtures of both precursors lead to composed spectra, thus envisaging the possibility of obtaining pre-designed spectral behaviors by varying the mixture composition.

Analysis of bulk and surface contributions in the neutron skin of nuclei

The neutron skin thickness of nuclei is a sensitive probe of the nuclear symmetry energy and has multiple implications for nuclear and astrophysical studies. However, precision measurements of this observable are difficult to obtain. The analysis of the experimental data may imply some assumptions about the bulk or surface nature of the formation of the neutron skin. Here we study the bulk or surface character of neutron skins of nuclei following from calculations with Gogny, Skyrme, and covariant nuclear mean-field interactions. These interactions are successful in describing nuclear charge radii and binding energies but predict different values for neutron skins. We perform the study by fitting two-parameter Fermi distributions to the calculated self-consistent neutron and proton densities. We note that the equivalent sharp radius is a more suitable reference quantity than the half-density radius parameter of the Fermi distributions to discern between the bulk and surface contributions in neutron skins. We present calculations for nuclei in the stability valley and for the isotopic chains of Sn and Pb.

Highly selective transport of mercury(II) ion through a bulk liquid membrane

In this work carrier-facilitated transport of mercury(II) against its concentration gradient from aqueous 0.04 M hydrochloric acid solution across a liquid membrane containing isopropyl 2-[(isopropoxycarbothiolyl)disulfanyl]ethane thioate (IIDE) as the mobile carrier in chloroform has been investigated. Sodium thiocyanate solution (1.6 M) was the most efficient receiving phase agent among several aqueous reagents tested. Various parameters such as investigated. Under optimum conditions the transport of Hg(II) across the liquid membrane is more than 97% after 2.5 h. The carrier, IIDE, selectively and efficiently could able to transport Hg (II) ions in the presence of other associated metal ions in binary systems.

Simultaneous determination of gemifloxacin and diuretics in bulk, pharmaceutical dosage forms and human serum by RP-HPLC

An isocratic reversed phase high-performance liquid chromatographic (RP-HPLC) method has been developed for the simultaneous determination of gemifloxacin and diuretics (hydrochlorothiazide and furosemide) in bulk, dosage formulations and human serum at 232 nm. Chromatographic separation was achieved on Purospher Start C18 (250 mm x 4.6 mm, 5 µm) column using mobile phase, methanol: water: acetonitrile (70:25:5 v/v/v) adjusted to pH 3.0 via phosphoric acid 85% having flow rate of 0.8 mL min -1 at room temperature. Calibration curves were linear over range of 0.5-10 µg mL -1 with a correlation coefficient ± 0.999. LOD and LOQ were in the ranges of 0.75-2.56 µg mL -1. Intra and inter-run precision and accuracy results were 98.26 to 100.9.

Spectrophotometric and spectrofluorimetric determination of some drugs containing secondary amino group in bulk drug and dosage forms via derivatization with 7-Chloro-4-Nitrobenzofurazon

Sensitive and selective spectrophotometric and spectrofluorimetric methods have been developed for determination of some drugs such as Pramipexole, Nebivolol, Carvedilol, and Eletriptan, which commonly contain secondary amino group. The subject methods were developed via derivatization of the secondary amino groups with 7-Chloro-4-Nitrobenzofurazon in borate buffer where a yellow colored reaction product was obtained and measured spectrophotometrically or spectrofluorimetrically. Concentration ranges were found as 2.0 to 250 μg mL-1 and 0.1 to 3.0 μg mL-1, for spectrophotometric and spectrofluorimetric study, respectively. The described methods can be easily applied by the quality control laboratories in routine analyses of these drugs in pharmaceutical preparations.

Simple and sensitive spectrophotometric methods for the analysis of mesalamine in bulk and tablet dosage forms

Three simple, sensitive, economical and reproducible spectrophotometric methods (A, B and C) are described for determination of mesalamine in pure drug as well as in tablet dosage forms. Method A is based on the reduction of tungstate and/or molybdate in Folin Ciocalteu's reagent; method B describes the reaction between the diazotized drug and α-naphthol and method C is based on the reaction of the drug with vanillin, in acidic medium. Under optimum conditions, mesalamine could be quantified in the concentration ranges, 1-30, 1-15 and 2-30 µg mL-1 by method A, B and C, respectively. All the methods have been applied to the determination of mesalamine in tablet dosage forms. Results of analysis are validated statistically.

Theoretical investigations of the bulk modulus in the tetra-cubic transition of PbTiO3 material

Resulting from ion displacement in a solid under pressure, piezoelectricity is an electrical polarization that can be observed in perovskite-type electronic ceramics, such as PbTiO3, which present cubic and tetragonal symmetries at different pressures. The transition between these crystalline phases is determined theoretically through the bulk modulus from the relationship between material energy and volume. However, the change in the material molecular structure is responsible for the piezoelectric effect. In this study, density functional theory calculations using the Becke 3-Parameter-Lee-Yang-Parr hybrid functional were employed to investigate the structure and properties associated with the transition state of the tetragonal-cubic phase change in PbTiO3 material.

Argentimetric assay of ranitidine in bulk drug and in dosage forms

Two simple, rapid and cost-effective methods based on titrimetric and spectrophotometric techniques are described for the assay of RNH in bulk drug and in dosage forms using silver nitrate, mercury(II)thiocyanate and iron(III)nitrate as reagents. In titrimetry, an aqueous solution of RNH is treated with measured excess of silver nitrate in HNO3 medium, followed by determination of unreacted silver nitrate by Volhard method using iron(III) alum indicator. Spectrophotometric method involve the addition a known excess of mercury(II)thiocyanate and iron(III)nitrate to RNH, followed by the measurement of the absorbance of iron(III)thiocyante complex at 470 nm. Titrimetric method is applicable over 4-30 mg range and the reaction stoichiometry is found to be 1:1 (RNH: AgNO3). In the spectrophotometric method, the absorbance is found to increase linearly with concentration of RNH which is corroborated by the correlation coefficient of 0.9959. The system obey Beer's law for 5-70 µg mL-1. The calculated apparent molar absorptivity and sandell sensitivity values are found to be 3.27 ´ 10³ L mol-1 cm-1, 0.107 µg cm-2 respectively. The limits of detection and quantification are also reported for the spectrophotometric method. Intra-day and inter-day precision and accuracy of the methods were evaluated as per ICH guidelines. The methods were successfully applied to the assay of RNH in formulations and the results were compared with those of a reference method by applying Student's t and F-tests. No interference was observed from common pharmaceutical excipients. The accuracy of the methods was further ascertained by performing recovery tests by standard addition method.

Simple and sensitive spectrophotometric methods for the determination of acebutolol hydrochloride in bulk sample and pharmaceutical preparations

A direct, extraction-free spectrophotometric method has been developed for the determination of acebutolol hydrochloride (ABH) in pharmaceutical preparations. The method is based on ion-pair complex formation between the drug and two acidic dyes (sulphonaphthalein) namely bromocresol green (BCG) and bromothymol blue (BTB). Conformity to Beer's law enabled the assay of the drug in the range of 0.5-13.8 µg mL-1 with BCG and 1.8-15.9 µg mL-1 with BTB. Compared with a reference method, the results obtained were of equal accuracy and precision. In addition, these methods were also found to be specific for the analysis of acebutolol hydrochloride in the presence of excipients, which are co-formulated in the drug.