Effect of Indium and Antimony Doping on SnS Photoelectrochemical Solar Cells

Single crystals of pure SnS, indium （In） and antimony （Sb） doped SnS are grown by the direct vapor transport technique. Two doping concentrations of 5 at. % and 15 at. % are employed for both In and Sb dopants. In total, five samples are studied, i.e., pure SnS, 5at.% In-doped SnS, 15at.% In-doped SnS, 5at.% Sb-doped SnS and 15at.% Sb-doped SnS single crystals. The energy dispersive analysis of x-ray （EDAX） and x-ray diffraction （XRD） analysis show that all the five as-grown single crystal samples possess near perfect stoichiometry and orthorhombic structure, respectively. The doping of In and Sb in SnS is established from the EDAX data and from the shift in the peak positions in XRD. Photoeleetroehemical （PEC） solar cells are fabricated by using the as- grown single crystal samples along with iodine/iodide electrolytes. Mott-Schottky plots for different compositions of iodine/iodide electrolytes show that O. 025 M 12 ＋ 1 M Nal＋2 M Na2 S04 ＋0.5 M 1-12 S04 will be the most suitable electrolyte. Study of efficiency （η） and fill factor for different intensities of illuminations at room temperature is carried out for the five samples. The In-doped SnS single crystals show better PEC efficiency than the undoped and Sl〉doped SnS single crystals.     

Molecular precursors for the preparation of homogenous zirconia-silica materials by hydrolytic sol-gel process in organic media. Crystal structures of [Zr{OSi(O(t)Bu)3}4(H2O)2]·2H2O and [Ti(O(t)Bu){OSi(O(t)Bu)3}3

[Zr(OPr(i))(4)·Pr(i)OH] reacts with [HOSi(O(t)Bu)(3)] in anhydrous benzene in 1:1 and 1:2 molar ratios to afford alkoxy zirconosiloxane precursors of the types [Zr(OPr(i))(3){OSi(O(t)Bu)(3)}] (A) and [Zr(OPr(i))(2){OSi(O(t)Bu)(3)}(2)] (B), respectively. Further reactions of A or B with glycols in 1:1 molar ratio afforded six chemically modified precursors of the types [Zr(OPr(i))(OGO){OSi(O(t)Bu)(3)}] (1A-3A) and [Zr(OGO){OSi(O(t)Bu)(3)}(2)] (1B-3B), respectively [where G = (-CH(2)-)(2) (1A, 1B); (-CH(2)-)(3) (2A, 2B) and (-CH(2)CH(2)CH(CH(3)-)} (3A, 3B)]. The precursors A and B are viscous liquids, which solidify on ageing whereas the other products are all solids, soluble in common organic solvents. These were characterized by elemental analyses, molecular weight measurements, FAB mass, FTIR, (1)H, (13)C and (29)Si-NMR studies. Cryoscopic molecular weight measurements of all the products, as well as the FAB mass studies of 3A and 3B, indicate their monomeric nature. However, FAB mass spectrum of the solidified B suggests that it exists in dimeric form. Single crystal structure analysis of [Zr{OSi(O(t)Bu)(3)}(4)(H(2)O)(2)]·2H(2)O (3b) (R(fac) = 11.9%) as well as that of corresponding better quality crystals of [Ti(O(t)Bu){OSi(O(t)Bu)(3)}(3)] (4) (R(fac) = 5.97%) indicate the presence of a M-O-Si bond. TG analyses of 3A, B, and 3B indicate the formation of zirconia-silica materials of the type ZrO(2)·SiO(2) from 3A and ZrO(2)·2SiO(2) from B or 3B at low decomposition temperatures (≤200 °C). The desired homogenous nano-sized zirconia-silica materials [ZrO(2)·nSiO(2)] have been obtained easily from the precursors A and B as well as from the glycol modified precursors 3A and 3B by hydrolytic sol-gel process in organic media without using any acid or base catalyst, and these were characterized by powder XRD patterns, SEM images, EDX analyses and IR spectroscopy.     

Time-resolved time-dependent photo-acoustic spectroscopy of NO2 in a high frequency multi-resonant cavity

The paper reports the pulsed laser-based time-resolved time-dependent Photo-acoustic (PA) spectroscopy of NO₂ gas in a specially designed multi mode-Resonant PA Cell which is made of Stainless Steel and has a “Q” value of the order of 79. Furthermore the designed cell allows us to excite some of the longitudinal, radial and azimuthal resonance modes of the photo-acoustic signals simultaneously in a very efficient manner. The presence of many newly excited modes occur at 7050 Hz, 10350 Hz and 14650 Hz frequencies is observed for the first time in NO₂ at room temperature. These results are obtained by employing second harmonics i.e. λ=532 nm pulses from Q-switched Nd:YAG laser having 7 ns pulse duration. Some of the new acoustic spectrum lines at higher frequencies are recorded between 0.5–10 ms data acquisition time, which also extends the frequency monitoring range of our system. The study also highlights some of the important aspects such as the decaying behavior of some of these resonant acoustic spectrum lines occur on the expense of others as well as the saturation behavior of some other modes in the NO₂ gas sample. The estimated low level detection limit of NO₂ buffered in air is of the order of 17.9 ppbV.     

Synthesis of 3,7-diiodo-2,6-di(thiophen-2-yl)benzo[1,2-b:4,5-b']difurans: functional building blocks for the design of new conjugated polymers

3,7-Diiodo-2,6-di(thiophen-2-yl)benzo[1,2-b:4,5-b']difurans are efficiently prepared by an iodine-promoted double cyclization. This new heterocyclic core is readily modified by the attachment of alkyl chains for improved solubility. The use of these compounds for the synthesis of new conjugated polymers is also reported.     

Structural and optical characterization of Ag-doped TiO2 nanoparticles prepared by a sol–gel method

Undoped and silver-doped TiO₂ nanoparticles (Ti_1?x Ag _x O₂, where x?=?0.00?C0.10) were synthesized by a sol?Cgel method. The synthesized products were characterized by X-ray diffraction (XRD), particle size analyzer (PSA), scanning electron microscope (SEM), and UV?CVisible spectrophotometer. XRD pattern confirmed the tetragonal structure of synthesized samples. Average crystallite size of synthesized nanoparticles was determined from X-ray line broadening using the Debye?CScherrer formula. The crystallite size was varied from 8 to 33?nm as the calcination temperature was increased from 300 to 800?°C. The incorporation of 3 to 5% Ag⁺ in place of Ti⁴⁺ provoked a decrease in the size of nanocrystals as compared to undoped TiO₂. The SEM micrographs revealed the agglomerated spherical-like morphology of particles. SEM, PSA, and XRD measurements show that the particles size of the powder is in nanoscale. Optical absorption measurements indicated a red shift in the absorption band edge upon silver doping. Direct allowed band gap of undoped and Ag-doped TiO₂ nanoparticles measured by UV?CVis spectrometer were 3.00 and 2.80?eV, respectively, at 500?°C.     

Aqua mediated indium(III) chloride catalyzed synthesis of fused pyrimidines and pyrazoles

The utilization of water as solvent and indium trichloride as promoter for the three-component combinatorial synthesis of a variety of bioactive pyrimidine and pyrazole derivatives (2–10) from aldehydes, 1,3-dicarbonyl compounds, and electron-rich amino heterocycles like 6-amino-1,3-dimethyl uracil and 3-methyl-1-phenyl-1H-pyrazol-5-amine catalyzed by indium trichloride under reflux has been studied. A new class of pyrimidine derivatives (2) has also been synthesized and the structure was confirmed by single crystal X-ray analysis. The reactions are environmentally benign, reaction product could be isolated easily and the catalyst could be recycled, which makes it an appealing synthetic protocol.     

Pd-catalyzed amination of 6-halo-2-cyclopropyl-3-(pyridyl-3-ylmethyl) quinazolin-4(3H)-one

6-Halo-2-cyclopropyl-3-(pyridyl-3-ylmethyl) quinazolin-4(3H)-one derivatives have been synthesized and utilized for amination reactions with aryl, heteroaryl and alkyl amines. Optimization of reaction conditions with different catalysts, ligands, bases, and solvents was conducted. The combination of Pd₂(dba)₃ with DavePhos (L3) proved to be best for these conversions in the presence of NaO^tBu in 1,4-dioxane at 100 °C. The relative reactivities of 6-bromo and 6-chloro-2,3-disubstitued quinazolinones with p-toluidine were conducted and as anticipated the 6-bromo analogue was totally consumed and 6-chloro derivative was completely unreactive.     

Asymmetric aldol additions: use of titanium tetrachloride and (-)-sparteine for the soft enolization of N-acyl oxazolidinones, oxazolidinethiones, and thiazolidinethiones.

Asymmetric aldol additions using chlorotitanium enolates of N-acyloxazolidinone, oxazolidinethione, and thiazolidinethione propionates proceed with high diastereoselectivity for the Evans or non-Evans syn product depending on the nature and amount of the base used. With 1 equiv of titanium tetrachloride and 2 equiv of (-)-sparteine as the base or 1 equiv of (-)-sparteine and 1 equiv of N-methyl-2-pyrrolidinone, selectivities of 97:3 to > 99:1 were obtained for the Evans syn aldol products using N-propionyl oxazolidinones, oxazolidinethiones, and thiazolidinethiones. The non-Evans syn aldol adducts are available with the oxazolidinethione and thiazolidinethiones by altering the Lewis acid/amine base ratios. The change in facial selectivity in the aldol additions is proposed to be a result of switching of mechanistic pathways between chelated and nonchelated transition states. The auxiliaries can be reductively removed or cleaved by nucleophilic acyl substitution. Iterative aldol sequences with high diastereoselectivity can also be accomplished.     

Radiation effect on temperature distribution in three-dimensional Couette flow with suction or injection

A theoretical analysis of three-dimensional Couette flow with radiation effect on temperature distribution has been analysed, when the injection of the fluid at the lower stationary plate is a transverse sinusoidal one and its corresponding removal by constant suction through the upper porous plate is in uniform motion. Due to this type of injection velocity, the flow becomes three-dimensional. The effect of Prandtl number, radiation parameter and injection parameter on rate of heat transfer has been examined by the help of graphs. The Prandtl number has a much greater effect on the temperature distribution than the injection or radiation parameter.