Edward M. Kosower

Plasmon-Resonance-Enhanced Absorption and Circular Dichroism†

Transmission electron microscopy of the silver nanoparticles formed in the presence of the l-GSH with an Ag/ ligand concentration ratio of 50:1 showed a broad particlesize distribution in the range of 2–50 nm, with no apparent change in size distribution on addition of the bimane to the

Solvent motion controls the rate of intramolecular electron transfer in solution

Abstract The fluorescence decay times (τ- F ) for conversion (by intramolecular electron transfer) of the S 1,np state into the S 1,ct state of 6-(4-methylphenyl) amino-2-naphthalenesulfon-N,N-dimethylamide (TNSDMA) correlate well with the constant-charge dielectric relaxation times [τ 1 v = (e 00 /e s ) τ 1 ] in linear alcohols. Solvent motion thus controls certain intramolecular electron transfers.

Evanescent wave infrared spectroscopy of liquids using silver halide optical fibers

Infrared spectroscopic measurements of liquids were performed in an attenuated total internal reflection cell, using infrared transparent silver halide fibers. As an example, we studied evanescent wave absorption in water. In particular, we analyzed absorption dependence on various physical parameters, such as the length of the absorbing medium and the geometry of the beam at the fiber entrance and exit faces. Absorption peaks were easily traced and experimental results correlated well with theoretical calculations. These studies may lead to practical uses of fiberoptic‐based evanescent wave spectroscopy.

Novel attenuated total internal reflectance spectroscopic cell using infrared fibers for aqueous solutions

Silver halide (AgCl:AgBr) fibers were used as the light conductor for total internal reflection measurements in a Fourier transform infrared (FTIR) spectrometer, to obtain spectra of aqueous solutions. The use of optical fibers in an attenuated total reflectance type cell with an FTIR spectrometer was demonstrated for the first time. Spectra of acetone in water and of glycine in water were acquired with the cell.

Static and dynamic electrolyte effects on excited-state behavior

Abstract After excitation of coumarin 153 in ethyl acetate, fast dielectric relaxation is succeeded by the nanosecond time scale translational relaxation of the “dipolar atmosphere” (LiClO4 ion pairs). New ways of probing medium effects on excited-state behavior are thus opened.

New insights into the mechanism of fast intramolecular electron transfer

Abstract Activationless, solvent-controlled fast intramolecular electron transfer (ET) rate constants are reported for three N-arylaminonaphthalenesulfon-N,N-dimethylamides over a wide temperature range. The conversion of the initial S 1,np state into the S 1,ct state (by a two-state mechanism) is confirmed by time-resolved spectroscopy for which appropriate simulations can be constructed.

Fourier transform infrared spectra of aqueous protein mixtures using a novel attenuated total internal reflectance cell with infrared fibers

A specially designed cell containing a silver halide (AgBr:AgCl) infrared fiber allows convenient and reproducible loading of viscous protein solutions and suspensions. Attenuated total internal reflectance measurements using an FTIR spectrometer were made for bovine serum albumin-water past. Dynamic changes in the protein films are readily followed, a technique which should be generally useful. A band assigned to a secondary structural feature, the alpha-helix, is similar in intensity to that reported (T.M. Fong, M.G. McNamee, submitted for publication).

Fast non-exponential intramolecular electron transfer reactions in pentanediol solutions

Abstract Activationless, solvent-controlled fast intramolecular electron transfer (ET) kinetics are reported for three N-arylaminonaphthalenesulfon-N,N-dimethylamides over a wide temperature range in three pentanediols. A stretched exponential decay (Williams-Watts) using the longitudinal relaxation time, τ L , fits the results. The temperature dependence of the observed dynamics is interpreted.

Kinetic studies on intramolecular electron transfer in solution

Abstract Lifetimes of the non-planar S 1 (S 1,np ) state of 6-N-4-methylphenylamino-2-naphthalenesultonic acid N,N-dimethylamide (TNSDMA), produced by picosecond pulse excitation, are the same as the risetimes of the charge-transfer S 1 (S 1,ct ) state, which itself decays at lower rates, in a series of linear alkanol solvents. Factors which influence the electron-transfer rates are noted.

The transition from non-adiabatic to solvent controlled adiabatic electron transfer kinetics. An experimental study

Abstract At sufficiently high temperatures, the solvent longitudinal dielectric relaxation time τL is less than 1 ns; the charge-transfer process converting the S1,CT to S0 of arylaminonaphthalenesulfon-N,N-dimethylamide derivatives is controlled by solvent polarity, while at lower temperatures, τL is more than 1 ns and controls the rate.