On the enhanced electrocatalytic activity of Pd overlayers on carbon-supported gold particles in hydrogen electrooxidation

Palladium-gold particles with varied composition were prepared by Pd electrochemical deposition on Au nanoparticles immobilized on model carbon support. Pd-Au/C catalysts were characterized ex situ by transmission electron microscopy, energy dispersive X-ray analysis and X-ray photoelectron spectroscopy, and in situ, by underpotential deposition of hydrogen and copper adatoms, and CO stripping. Hydrogen oxidation reaction on pristine and CO-poisoned Pd-Au/C particles was studied using rotating disk electrode (RDE) technique. It was found that the decrease of the effective Pd overlayer thickness below ca. two monolayers resulted in a two-fold increase of the exchange current density of the hydrogen oxidation reaction and in significant increase of CO tolerance.     

A lithium-selective glass electrode

We pioneered the study of the electrode properties of glasses containing 80 and 85 wt % LiF and 20 and 15 wt % A1(PO₃)₃. LiF-80-based glass electrodes functioned as lithium-selective electrodes in 1-0.0001 M LiCl solutions. Contrary to aliminosilicate glasses, these glasses responded to the Li⁺ ion better than to the Na⁺ ion and were nonselective to the Hi⁺ ion. This made them promising for the development of sensors for Li⁺ ions in different solutions. Forward and reverse transitions of these glasses from the hydrogen to the lithium function and from the lithium to the sodium function are described by the equation of the simple Nikol’skii theory. Presented at the V All-Russian Conference with the Participation of CIS Countries on Electrochemical Methods of Analysis (EMA-99), Moscow, December 6–8, 1999.     

Electronic excitation energy transfer between molecules of carbocyanine dyes in complexes with DNA

Electronic excitation energy transfer has been carried out between molecules of carbocyanine dyes bound noncovalently to DNA. 3,3′,9-Triethyl-5,5′-dimethyloxacarbocyanine iodide was used as an energy donor and 3,3′-diethylthiacarbocyanine iodide as an acceptor dye. In this process, the band belonging to the donor is observed in the fluorescence excitation spectrum of the acceptor. Donor fluorescence quenching by the acceptor in the presence of DNA was studied. The results of the experiments are discussed in terms of the Dye-DNA stoichiometric complex formation and with respect to concentrating the dyes in the microphase (pseudophase) of the biopolymer.     

Study of electronic excitation energy transfer between cyanine dye molecules noncovalently bound to DNA

Electronic excitation energy transfer between molecules of carbocyanine dyes noncovalently bound to DNA was studied. 3,3′,9-Triethyl-5,5′-dimethyloxacarbocyanine iodide and 3,3′-dimethyl-9-ethyloxacarbocyanine iodide were used as energy donors, and 3,3′-diethylthiacarbocyanine iodide served as an acceptor dye. The fluorescence decay kinetics of the donors and its quenching by the acceptor in the presence of DNA were measured. The microphase model was used for interpretation of the experimental data, with allowance for concentrating dye molecules in the vicinity of DNA molecules.     

Distribution of distances in donor-acceptor pairs of cyanine dyes upon electronic excitation energy transfer in the presence of DNA

Electronic excitation energy transfer (EEET) between molecules of carbocyanine dyes, which form noncovalent complexes with DNA, has been studied by picosecond spectroscopy. Three oxacarbocyanine dyes have been used as electronic excitation energy donors, and 3,3′-diethylthiacarbocyanine iodide has served as an acceptor dye. An analysis of the kinetic dependences permitted obtaining the data on distribution of the distances in donor-acceptor pairs upon EEET. The effect of the acceptor concentration on the parameters of distribution of its molecules in the quenching microphase has been revealed.