Laser assisted decontamination of metal surface: Evidence of increased surface absorptivity due to field enhancement caused by transparent/semi-transparent contaminant particulates

Small signal absorption measurements of the incident coherent radiation by the metal surface have revealed an increase in the absorption by the surface in presence of transparent/semi-transparent particulates on it. This effect, identified as field enhanced surface absorption, has been found to increase with reduction in the average particulate size. Consequently higher laser assisted removal efficiency of contamination from a metal surface has been observed for smaller contaminant particulates. These measurements have been carried out utilizing coherent radiations of two different wavelengths so chosen that for one the particulates are totally transparent while for the other they are partially transparent.     

Synthesis, spectral characterization, catalytic and antibacterial studies of new Ru(III) Schiff base complexes containing chloride/bromide and triphenylphosphine/arsine as co-ligands

A new Ru(III) Schiff base complexes of the type [RuX(EPh₃)L] (X = Cl/Br; E = P/As; L = dianion of the Schiff bases were derived by the condensation of 1,4-diformylbenzene with o-aminobenzoic acid/o-aminophenol/o-aminothiophenol in the 1:2 stoichiometric ratio) have been synthesized from the reactions of [RuX₃(EPh₃)₃] with appropriate Schiff base ligands in benzene in the 2:1 stoichiometric ratio. The new complexes have been characterized by analytical, spectral (IR, electronic, ¹H, ¹³C NMR and ESR), magnetic moment and electrochemical studies. An octahedral structure has been tentatively proposed for all these new complexes. All the new complexes have been found to be better catalyst for the oxidation of alcohols using molecular oxygen as co-oxidant at ambient temperature and aryl–aryl coupling reactions. These complexes were also subjected to antibacterial activity studies against Escherichia coli, Aeromonas hydrophilla and Salmonella typhi.     

Accumulative charge separation inspired by photosynthesis

Molecular systems that follow the functional principles of photosynthesis have attracted increasing attention as a method for the direct production of solar fuels. This could give a major carbon-neutral energy contribution to our future society. An outstanding challenge in this research is to couple the light-induced charge separation (which generates a single electron-hole pair) to the multielectron processes of water oxidation and fuel generation. New design considerations are needed to allow for several cycles of photon absorption and charge separation of a single artificial photosystem. Here we demonstrate a molecular system with a regenerative photosensitizer that shows two successive events of light-induced charge separation, leading to high-yield accumulation of redox equivalents on single components without sacrificial agents.     

Understanding hydrogen scrambling and infrared spectrum of bare CH5+ based on ab initio simulations

A comprehensive study of the properties of protonated methane obtained from ab initio molecular dynamics simulations is presented. Comparing computed infrared spectra to the measured one gives further support to the high fluxionality of bare CH(5)(+). The computational trick to partially freezing out large-amplitude motion, in particular hydrogen scrambling and internal rotation of the H(2) moiety, leads to an understanding of the measured IR spectrum despite the underlying rapid hydrogen scrambling motion that interconverts dynamically structures of different symmetry and chemical bonding pattern. In particular, the fact that C-H stretching modes involving the carbon nucleus and those protons that form the H(2) moiety and the CH(3) tripod, respectively, result in distinct peaks is arguably experimental support for three-center two-electron bonding being operative at experimental conditions. It is proposed that hydrogen scrambling is associated with the softening of a mode that involves the bending of the H(2) moiety relative to the CH(3) tripod, which characterizes the C(s) ground-state structure. The potential energy surface that is mapped on to a two dimensional subspace of internal coordinates provides insight into the dynamical mechanism for exchange of hydrogens between CH(3) tripod and the three-center bonded H(2) moiety that eventually leads to full hydrogen scrambling.     

A novel fluorophore with dual fluorescence: local excited state and photoinduced electron-transfer-promoted charge-transfer state.

Absorption and emission spectra of 9-N,N-dimethylaniline decahydroacridinedione (DMAADD) have been studied in different solvents. The fluorescence spectra of DMAADD are found to exhibit dual emission in aprotic solvents and single emission in protic solvents. The effect of solvent polarity and viscosity on the absorption and emission spectra has also been studied. The fluorescence excitation spectra of DMAADD monitored at both the emission bands are different. The presence of two different conformation of the same molecule in the ground state has lead to two close lying excited states, local excited (LE) and charge transfer (CT), and thereby results in the dual fluorescence of the dye. A CTstate involving the N,N-dimethylaniline group and the decahy droacridinedione chromophore as donor and acceptor, respectively, has been identified as the source of the long wavelength anomalous fluorescence. The experimental studies were supported by ab initio time dependent-density functional theory (TDDFT) calculations performed at the B3LYP/6-31G* level. The molecule possesses photoinduced electron transfer (PET) quenching in the LE state, which is confirmed by the fluorescence lifetime and fluorescent intensity enhancement in the presence of transition metal ions.     

Reactions of sulphuryl fluoride,sulphuryl chlorofluoride and sulphuryl chloride with amines

The reactions of sulphuryl fluoride, sulphuryl chlorofluoride and sulphuryl chloride with the amines tert-butylamine, benzylamine, piperidine, pyridine and quinoline have been investigated. The primary and secondary amines react with the elimination of hydrogen halides and formation of SN bonds whereas tertiary amines form 1:2 adducts.     

Analysis of ergosteroids. VIII: Enhancement of signal response of neutral steroidal compounds in liquid chromatographic-electrospray ionization mass spectrometric analysis by mobile phase additives

The signal response of moderately polar to nonpolar neutral steroidal compounds in positive ion mode was significantly improved in electrospray ionization mode by addition of volatile organic acids (trifluoroacetic acid, acetic and formic) at concentrations much lower than those normally employed for high-performance liquid chromatographic separations of ionic compounds. Each of the three acids enhanced the sensitivity, the order being: formic acid (approximately 50-200 ppm, v/v) > acetic acid (100-500 ppm) > trifluoroacetic acid (5-20 ppm). Higher concentrations caused decrease in the sensitivity. The extent of increase in the sensitivity was compound specific and also depended on the nature of organic modifier present in the mobile phase. Acetic acid was the acid of choice for the 'wrong-way-round' ionization of sulfate conjugates. The postcolumn addition of silver nitrate produced highly stable (M + Ag)+ adducts with concomitant increase in signal response and reduction in baseline noise.     

A full interionic potential for Na(1+x)Zr(2)Si(x)P(3-x)O(12) superionic conductors

Most inorganic solids are made up of octahedral and tetrahedral units interconnected to give an infinite framework. Use of computer simulation to study these materials has not been as prevalent as in the organic or biomolecules. Na(1+x)Zr(2)Si(x)P(3-x)O(12) is a typical inorganic solid with ZrO(6) octahedra and (Si/P)O(4) tetrahedra which are shown along with a few Na(+) sites marked M1, M2, and M3. We report here a full interionic potential which reproduces the structure and conductivity of these solids. This augurs well for the study of other inorganic solids.     

A study on the reaction of silicon tetrahalides with phosphorus pentoxide and of alkali metal fluorosilicates with phosphorus pentoxide and sulphur trioxide

Silicon tetrahalides, SiX₄ (X=F, Cl, Br) and the fluorosilicates of sodium and potassium react with phosphorus pentoxide above 300°C. The tetrahalides give rise to the corresponding phosphoryl halides and silica, while the fluorosilicates form the corresponding metal fluorophosphates and silicon tetrafluoride. The reaction of the fluorosilicates of sodium and potassium with sulphur trioxide occurs at room temperature to give rise to the corresponding metal fluorosulphates and silicon tetrafluoride.     

Molecular complexes of paraquat with anilines

The U V-VIS spectra of molecular complexes of paraquat with ring and N-substituted anilines have been recorded in methanol and 50% v/v aqueous methanol. All the complexes exhibited well-resolved charge transfer bands in the wavelength region where neither of the components have any absorption. The energies of charge transfer bands of the substituted aniline-paraquat complexes bear linear relationships with the ionization potentials obtained from the substituted aniline-TCNE complexes, indicating π - π interaction between paraquat and the donors. Both ring and N-substituents have effects on the positions of the CT bands as well as on the stabilities of the complexes. The positions of the CT bands are shifted to shorter wavelengths and the stabilities of the complexes decrease on going from methanol to aqueous. methanol.