Chemical modification of poly(n-hexylsilane) - Synthesis of functional polysilanes bearing thienyl groups on the appended sila-alkyl side chains and their application in the generation and stabilization of silver nanoparticles

The linear polysilanes [{RR′₂Si(CH₂)_ySi(n-hex)}_x{HSi(n-hex)}_1−x]_n (1-4; R = 2-thienyl, R′ = H; R = Me, R′ = 2-thienyl; y = 2, 3) have been synthesized by hydrosilylation reaction between preformed poly(n-hexylsilane) and (2-thienyl)vinyldichlorosilane/allyl(2-thienyl)dichlorosilane/bis(2-thienyl)methylvinylsilane/allyl-bis(2-thienyl)methylsilane using AIBN as the free radical initiator. GPC analysis reveals a monomodal molecular weight distribution in each case with M_w = 2492-3280 and PDI = 1.18-1.44. The polysilane 1 (R = 2-thienyl, R′ = H, y = 2) acts as reducing agent towards silver tetrafluoroborate under mild conditions (cyclohexane, rt, 5 h) to afford spherical silver nanoparticles of size 8.4 ± 0.7 nm, as evident from the TEM and dynamic light scattering (DLS) studies. The silver nanoparticles in the polymer matrix exhibit surface plasmon absorption at 420 nm suggesting the donor-acceptor interaction between the thienyl group and the metal nanocluster surface. This stabilization effect provides long shelf life stability to the nanoparticles in solution with no sign of agglomeration even after three months.     

Existence of the multiferroic property at room temperature in Ti doped CoFe2O4

The appearance of ferroelectricity has been observed in magnetically ordered Co(Fe_1?xTi_x)₂O₄ at room temperature. Magnetization and dielectric constant is found to increase with Ti doping. It is observed from an X-ray Photoemission Spectroscopy study that Ti goes to the octahedral site with (+4) ionic state. An M–H hysteresis curve at room temperature shows the ferrimagnetic ordering and a P–E loop at room temperature clearly indicates the existence of ferroelectricity.     

Preparation and characterization of N-methylene phosphonic and quaternized chitosan composite membranes for electrolyte separations

Chitosan was functionalized either by introducing a phosphonic acid group or by quaternization of existing primary ammonium groups in order to make it a water-soluble material. Functionalized chitosans and poly(vinyl alcohol) (PVA)-based nanoporous charged membranes were prepared in aqueous media and gelated in methanol at 10 degrees C to tailor their pore structure. These membranes were extensively characterized for their physicochemical, electrochemical, and permeation characteristics using FTIR, TGA, DSC, water content, ion-exchange capacity, ionic transport properties, and membrane permeability studies. N-Methylene phosphonic chitosan (NMPC)/PVA-based membranes exhibited mild cation selectivity and quaternized chitosan (QC)/PVA composite membranes had mild anion selectivity, while a blend of NMPC-QC/PVA membranes exhibited weak cation selectivity because of formation of zwitterionic structure. Viscosity measurements and interaction studies for individual and mixed solutions of NMPC and QC were carried out for the prediction of charge interactions between -PO3H2 and -N+(CH3)3 groups and effect on molecular weight due to functionalization. Elaborate electrochemical and permeation experiments were conducted in order to predict suitability of these membranes for the separation of mono- and bivalent electrolytes based on their hydrated ionic radius, and it was found that among all the synthesized membranes, PC/QC-30 had the highest relative permeability, which may extend its suitability for electrolyte separations. Observations were correlated with equivalent pore radius of the different membranes as estimated by membrane permeability measurements.     

Working group report: Heavy-ion physics and quark-gluon plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.     

Functional Mutations in and Characterization of VHH Against Helicobacter pylori Urease

Manipulation of clinically significant antibodies can effectively improve the processes of diagnosis and treatment. Affinity maturation process has a significant role in improvement of antibodies efficiency. Error-prone PCR technique is one of the proposed methods for improvement of the affinity of antibodies. In the present research, a method was applied to camel heavy-chain antibody (VHH, nanobody) raised against UreC subunit of urease enzyme from Helicobacter pylori. This VHH was used as a starting molecule to construct a highly diversified phage displayed VHH library. The constructed library of nanobody mutants was subjected to several rounds of panning against UreC antigen. High-affinity mutant was selected. Our VHH (HMR23) showed 1.5-fold higher binding activity than the parental VHH. In addition, the mutant VHH presented a better performance in inhibition of urease activity at low concentrations retaining its specificity and thermal stability.     

Instrumental detection limit and sensitivity of K and L shell X‐ray emission lines of 17Cl, 37Rb,and 38Sr elements using PC‐WDXRF spectrometer

This work was aimed to improve the instrumental detection limit and sensitivity of ₁₇Cl, ₃₇Rb, and ₃₈Sr elements present in solid samples by using the advanced polychromatic wavelength dispersive X‐ray fluorescence spectrometry method. Instrumental measuring parameters, as well as study of calibration curves of K and L shell spectral lines, were evaluated to select the best conditions for ₁₇Cl, ₃₇Rb, and ₃₈Sr quantification. From the results, it was observed that the detection limits of the Rb Kα and Sr Kα spectral lines were lower than those of the Kβ_1,3 and Lα spectral lines. From the calibration curves, it was concluded that Kα spectral lines are more suitable than Kβ_1,3 and Lα lines to identify the traces of ₁₇Cl, ₃₇Rb, and ₃₈Sr elements in different types of solid samples.     

Multi-wavelength generation using a bismuth-based EDF and Brillouin effect in a linear cavity configuration

The generation of a multiple wavelength source using a bismuth-based erbium-doped fiber (Bi-EDF) in a linear cavity configuration is demonstrated. The configuration uses a pair of optical circulators at the input and output ends of the cavity to form a resonator for multi-wavelength generation in conjunction with optical couplers to inject the Brillouin pump (BP) and to tap the output at the two ends. The Brillouin erbium fiber laser (BEFL) comb with a 2.15 m of Bi-EDF has a wavelength spacing of 0.09 nm and operates in long-wavelength (L-) band region. A stable output laser comb of 50 lines is obtained at a BP of 1568.2 nm and 5 dBm and two 1480 nm pumps at 120 mW. The injected BP wavelength and power as well as the 1480 nm pump powers have a great effect on the number of lines and output power of the BEFL. This configuration is compact due to the use of the significantly shorter Bi-EDF as the linear gain medium, and can be made more compact by replacing the single-mode fiber with highly non-linear fibers such as holey fibers.     

Effect of binding and conformation on fluorescence quenching in new 2',7'-dichlorofluorescein derivatives

[structure: see text] Symmetrical and unsymmetrical 2',7'-dichlorofluorescein (DCF) derivatives have been synthesized by means of Mannich reactions and an aromatic Claisen rearrangement. NMR and fluorescence spectroscopic studies reveal the correlation between the conformations, the photoinduced electron transfer mechanism, and fluorescent intensities of these DCF derivatives. Two quenching nitrogen atoms cooperatively and reversibly suppress the fluorescence of the chromophore.     

Ionic conduction in KBr-KI mixed crystals

Ionic conductivity of KBr_1?xI_x (0 ? x ? 0.5) mixed crystals has been studied as a function of temperature in the range of 2 ionic conductivity and lowers the activation energy appreciably which is consistent with our earlier results on AgBr-AgI mixed crystals, and proposal that the purely elastic displacements (lattice strain) caused by the very “wrong size” of the substituent ions is primarily responsible for the behavior. The strain thus produced is expected to cause “lattice loosening” and hence lowering of the melting points (T_m) or the enthalpy of formation of the Schottky defects (H_s). A semiquantitative calculation shows this to be the case.