Temperature dependence of the lattice vibrations of triglycine selenate

The polarized Raman spectra below 300 cm^?1 and the far infrared spectra from 400 to 30 cm^?1 of triglycine selenate were measured at various low temperatures. It was found that the Raman doublet at 44 and 38 cm^-1 observed in the paraelectric phase (space group C²_2h) was reduced to a singlet at 38 cm^?1 in the ferroelectric phase (space group C₂²). This spectral anomaly in the paraelectric phase appears to be due to the splitting of the translational mode of glycine I along the crystallographic b axis, the splitting being caused by the tunneling of glycine I across the barrier between the two potential minima which are located symmetrically on either side of the crystallographic ac plane (i.e. at $\text{b =}\text{1}\text{4}$ and $\text{3}\text{4}\text{)}$. New Raman bands which appear below the Curie temperature are also discussed.     

Multiple ionization bursts in laser-driven hydrogen molecular ion

Theoretical study on H2(+) in an intense infrared laser field on the attosecond time scale reveals that the molecular ion shows multiple bursts of ionization within a half-cycle of the laser field oscillation, in contrast to the widely accepted tunnel ionization picture for an atom. These bursts are found to be induced by transient localization of the electron at one of the nuclei, and a relation between the time instants of the localization and the vector potential of the laser light is derived. A scheme is proposed to probe the localization dynamics by an extreme ultraviolet laser pulse.     

Functionalization of mesoporous silica membrane with a Schiff base fluorophore for Cu(II) ion sensing

A Schiff base (SB) immobilized hybrid mesoporous silica membrane (SB-HMM) was prepared by immobilizing a Schiff base onto the pore surface of mesoporous silica (pore size=3.1 nm) embedded in the pores of a porous anodic alumina membrane. In contrast to the non-fluorescent analogous SB molecule in homogeneous solutions, SB-HMM exhibited intense fluorescence due to emission enhancement caused by aggregation of SB groups on the pore surface. The high quantum efficiency of the surface SB groups allows SB-HMM to function as a fluorescent sensor for Cu(II) ions in an aqueous solution with good sensitivity, selectivity and reproducibility. Under the optimal conditions described, the linear ranges of fluorescence intensity for Cu(II) are 1.2-13.8(M (R(2)=0.993) and 19.4-60 (R(2)=0.992) (M. The limit of detection for Cu(II) is 0.8 μM on basis of the definition by IUPAC (C(LOD)=3.3S(b)/m).     

Fluorescent trimethyl-substituted naphthyridine as a ligand for C-C mismatch detection in CCG trinucleotide repeats

We report on the selective binding of 2-amino-5,6,7-trimethyl-1,8-naphthyridine (ATMND) to C-C mismatch present in the hairpin structures of (CCG)(n) trinucleotide repeats that are associated with neurological diseases; this binding is accompanied by significant fluorescence quenching of ATMND.     

Enzyme catalytic membrane based on a hybrid mesoporous membrane

Immobilization of glucose oxidase (GOD) within a hybrid mesoporous membrane with 12 nm pore diameter was successfully achieved, resulting in catalytically high efficiency during flow of a glucose solution across the membrane.     

Freeze-thaw behaviour of aqueous glucose solutions--the crystallisation of cubic ice

We report on the polymorphic transitions of ice in aqueous solutions of glucose during freezing and thawing over a temperature range of 298-153 K. Emphasis is placed on the sub-glass temperature range where the systems consist of cubic ice (ice-1c) crystals embedded in a freeze concentrated, vitrified glucose solution. The systems were studied by a combination of thermal, cryomicroscopic and X-ray diffraction techniques. At the glass transition (230 K) the solution phase contained 80 mol% of unfrozen water which, on further cooling, was shown to crystallise as cubic ice (ice-1c), nucleated in the vitrified matrix. The thermal stability of the ice-1c formed was studied by annealing and isothermal changes in the diffraction patterns with time. The polymorphic transition 1c --> 1h could be fitted to first order kinetics. Contrary to currently held belief, this study has provided evidence that ice-1c can be formed directly in the bulk water phase of a vitrified solution.     

An efficient one-pot synthesis of unsymmetrical ethers: a directly reductive deoxygenation of esters using an InBr3/Et3SiH catalytic system

This study describes a novel one-pot procedure for a directly reductive conversion of the carbonyl function of esters to the corresponding ethers by Et3SiH in the presence of a catalytic amount of InBr3.