Effect of isomeric butanols on the temperature corresponding to the adiabatic compressibility minimum of water

The effect of isomeric butanols on the temperature corresponding to the adiabatic compressibility minimum of water (T _β) was studied using a variablepath interferometer working at 3 MHz. The structural contribution to the shift inT _β, [ΔT _βstr]_exp, was found to be positive and to increase with concentration to a maximum atX ₂?0.0193, 0.0100, and 0.0090 fort-butanol, sec-butanol, and isobutanol, respectively. The results have been explained on the basis of stabilization of water structure at low concentrations of alcohol. The quantity [ΔT _βstr]_exp forn-butanol is practically zero at low concentrations, while at high concentrations it is negative, indicating rupture of the hydrogen-bonded structure of water by this solute. At any given concentration,t-butanol > sec-butanol > isobutanol >n-butanol is the order of increasing structural contribution to the shift inT _β. Theoretical values of the structural contribution to the shift inT _β are in good agreement with the experimental data.     

Study of phase transition and volume thermal expansion in a rare-earth (RE) oxyfluoride system by high-temperature XRD (RE=La, Nd, Sm, Eu and Gd)

Volume thermal expansion behaviour of a number of rare-earth oxyfluorides (REOF) have been studied using high-temperature X-Ray diffractometry (HT-XRD) in the 298–1075 K range in air. The studies revealed an anomalous expansion for each compound associated with phase transition. The phase transition temperature and the coefficient of volume thermal expansion of five compounds in REOF series determined by this method are reported and compared with our earlier results obtained by dilatometry.     

Solid-state diphotocyclization of iso- and terephthalaldehydes via dihalogen substitution

The supramolecular nonbonded C-H...X interactions between formyl hydrogens and ortho-halogen atoms (Br/Cl) have been exploited to achieve conformational control in the solid state of dimethyl-substituted iso- and terephthaladehydes (1-3) for unprecedented diphotocyclization. It is shown that the dihalogen substitution also contributes to the stability of the benzocyclobutenols relative to their precursor photoenols, so that the solid-state photolysis of dialdehydes 2b, 2c, and 3b leads to diphotocyclization to afford respectable yields of bis-benzocyclobutenols.     

One-electron oxidation of toluidine blue. A pulse radiolysis study

The one-electron oxidation of toluidine blue by specific oxidising radicals such as Cl ₂ ⁻ , Tl(II), N₃, Br ₂ ⁻ etc. has been studied by employing the pulse radiolysis technique. The Br ₂ ⁻ radical was found to be less efficient in oxidising toluidine blue as compared to Cl ₂ ⁻ ., Tl⁺² and N₃. The semioxidised species exhibited only onepK _a indicating the presence of two conjugate acid-base forms whose spectral and kinetic features were evaluated. Reaction of OH radicals with the dye gave rise to a transient species which exhibited spectral and kinetic features different from that of the semioxidised species indicating that the mode of reaction of OH is different.     

In situ fabricated porous filters for microsystems

Porous filters were fabricated inside a microchannel using emulsion photo-polymerization. The porosity of the filter is dependent on the composition of the pre-polymer mixture. The morphology and flow resistance of four filters with varying water and cross-linker concentrations was studied. The porous filter was used to separate samples, such as whole blood to cell/serum components, based on size. The efficiency of cell/serum separation by the porous filter was tested by performing a glucose-6-phosphate dehydrogenase assay and was found to be comparable to separation by centrifuge. The porous filter thus mimics the functionality of the centrifuge, with the added benefits of no power requirements and ability to handle small sample volumes.     

An investigation on visible luminescence of Ho activated LBTAF glasses

Different concentrations of Ho³⁺-doped lead borate titanate aluminum fluoride (LBTAFHo) glasses with chemical composition of PbO-H₃BO₃-TiO₂-AlF₃-Ho₂O₃ were prepared by the melt quenching method. The spectral properties were investigated using the absorption, emission and decay measurements. The experimental oscillator strengths were calculated from the area under the absorption bands. Applying Judd-Ofelt theory, the intensity parameters (Ω_{λ=2, 4, 6}) were calculated, by the least square fit approach from which the radiative transition rates, luminescence branching ratios and radiative decay times were determined. The photoluminescence spectra revealed the quenching of luminescence intensity beyond 1.0 mol% of Ho³⁺ ion concentration. To investigate the luminescence potentiality of ⁵F₄→⁵I₈ emission level, the effective bandwidth and the stimulated emission cross-section were determined. The quenching in experimental decay time is attributed to the resonance energy transfer among the excited Ho³⁺ ions.     

Electrical,Mechanical, and Thermal Properties of Poly(4,4′-Cyclohexylidene Diphenylene-m-Benzene/Toluene-2,4-Disulfonate)

Abstract

The films of poly(4,4′-cyclohexylidene diphenylene-m-benzene disulfonate) (PSBB, 0.610 mm thick) and poly(4,4′-cyclohexylidene diphenylene-toluene-2,4-disulfonate) (PSBT, 0.537 mm thick) showed 8.23 ± 0.25 and 9.6 ± 0.245 kV, respectively, as the dielectric breakdown voltage (ac) in air at room temperature. The same films have 8.8 × 10¹¹ and 7.2 × 10¹⁴ ω°Cm volume resistivity. PSBB (40 μm thick) and PSBT (50 μm thick) films have tensile strengths of 1971 and 1677 kg/cm² and percent elongations of 1.3 and 1.2, respectively. The static hardnesses of PSBB (0.178 mm thick) and PSBT (0.190 mm thick) at three different loads (15–60 g) are 12.8–15.5 and 14.5–16.5 kg/mm², respectively. PSBB and PSBT are thermally stable up to about 355°C in an N₂ atmosphere and involve two-step degradation. DSC and DTA showed T _g at about 125–127 and 138–142°C, respectively, for PSBB and PSBT in N₂. PSBB and PSBT have comparable breakdown voltages and volume resistivity with some useful plastics whereas they have superior T _g and thermal stability with retention of excellent solubility in common solvents over polysulfonates without a cardo group. Thus, the cardo (cyclo-hexyl) group has enhanced thermal and mechanical properties with excellent solubility and easy processing.     

Catalytic deactivation of gold surface as a consequence of Prussian blue electrodeposition and removal

It is shown that the gold surface is catalytically deactivated and smoothened upon removal of the Prussian blue (PB)–gold nanocomposite formed on the gold surface. Atomic force microscopy proves surface smoothening after PB removal. The voltammetric responses of Ru(NH₃)₆Cl₃ on the smoothened surface remain unaffected, but the reactions that involve multistep and inner-sphere electron transfer are affected on the smoothened surface as exemplified by hydroquinone, ferrous oxalate redox reactions, and oxygen reduction. These effects are attributed to catalytic deactivation as a consequence of removal of the active sites.

Solvent-Free Esterification of Carboxylic Acids and Alcohols in the Presence of Silphos [PCl3-n(SiO2)n] as a Heterogeneous Phosphine Reagent

An efficient solvent-free method for the preparation of esters from various aromatic and aliphatic acids with primary, secondary, and tertiary alcohols using a heterogeneous phosphine reagent, silphos [PCl_3-n(SiO₂)_n], in good yields is reported.