Edward M. Eyring

Piezoelectric detection of photoacoustic signals

Piezoelectric detection of photoacoustic signals offers a number of advantages over the better known microphonic technique for condensed phase samples. Experimental techniques are greatly simplified by taking advantage of the acoustic impedance match offered by solid state detectors with solid or liquid samples. Such piezoelectric detectors prove suitable for ac steady state measurements as well as impulse-transient response detectors. Several example spectra of Nd(III) are presented with emphasis on the effects of the fluorescence-lifetime in Nd:glass laser material.

Mass Spectrum of Propane: Isotope Effect and Metastable Ions

The mass spectra of propane and of propane‐2,2‐d2 have been calculated assuming that the mass spectra result from successive and competing unimolecular reactions following initial vertical ionization of the parent molecules. Reasonable agreement with experiment is found for the change in mass spectral pattern with deuterium substitution. The metastable ion peaks are shown to be a normal part of the mass spectrum.

Direct blue dye solutions: photo properties

Abstract Weakly fluorescing azo dyes can be used as photothermal sensitizing agents in the photodynamic therapy (PDT) of some forms of cancer and other diseases. A desirable property of such a dye is that it will dissipate most of its excitation energy by nonradiative decay processes rather than by fluorescence or energy transfer to dioxygen. The maximum absorbance wavelengths, the fluorescence quantum yields Φ F , the mean fluorescence wavelengths, and threshold dye concentrations below which Φ F does not decrease with rising dye concentrations are reported for nine azo dyes that appear to have the correct optical properties for application as photothermal sensitizing agents.

Kinetics of micelle dissociation by a light-scattering temperature jump method

Abstract The temperature-jump relaxation method now widely used in fast reaction kinetics has been modified for application to micellar kinetics. Time-dependent intensities of scattered white light following a 9° temperature jump, have been separately measured for aqueous solutions of sodium dodecyl sulfonate, dodecylammonium chloride, and dodecylpyridinium iodide. First-order dissociation rate constants have been computed from the observed relaxation times for micelles of each of these three ionic surfactants. These dissociation rate constants range from 4 sec−1 at 35°C for dodecyl-ammonium chloride and 17 sec−1 at 45°C for sodium dodecyl sulfonate up to 120 sec−1 at 35°C for dodecylpyridinium iodide. These numerical values include uncertainties in the aggregation numbers from which they were calculated.

Production of diethyl carbonate from ethanol and carbon monoxide over a heterogeneous catalytic flow reactor

Abstract Diethyl carbonate (DEC) is a candidate for use as an oxygen-containing additive in gasoline and diesel fuel to diminish pollutant emissions. The synthesis of DEC by the oxidative carbonylation of ethanol in the gas phase over heterogeneous CuCl 2 /PdCl 2 catalysts supported on activated carbon (AC) has been investigated using a laboratory-scale continuous flow reactor with online GC/MS. Influences of various reaction conditions and catalyst pretreatment on the DEC yield and selectivity have been tested. Yield of DEC at 150 °C reached a maximum of 12.5 wt.% and was found to increase with an increase of residence time, reaction temperature, and reaction pressure as expected. The relationship between CO flow rate and production of DEC showed three distinct regions of DEC production. A by-product, diethoxymethane (DEM), was formed when ethanol was introduced in stoichiometric excess. Catalyst pretreated with KOH presented the best catalytic performance, and all metal hydroxides tested enhanced the yield of and selectivity for DEC simultaneously. However, the CuCl 2 /PdCl 2 /AC–KOH catalyst with a higher OH/Cu mole ratio than 2.0 showed an even lower DEC yield than that found using a CuCl 2 /PdCl 2 /AC catalyst without KOH.

Synthesis of nanosize-controllable copper and its alloys in carbon shells

Nanosize-controllable Cu, Ag, Pd, Ni, CuPd alloy and Cu-Ag bimetal encapsulated in inert carbon shells can be synthesized by carbonization of metal-cyclodextrin complexes with a remarkable capability of experimentally determining the size-dependent melting temperature depression of many metal or alloy nanoparticles.

Normalizing Infrared FT Photoacoustic Spectra of Solids

Abstract Photoacoustic spectroscopy (PAS) has only recently emerged as a tool for the investigation of the vibrational spectra of condensed matter and surface adsorbates. Qualitative infrared (IR) photoacoustic spectra of various solid materials have been reported both dispersively1–5 and in the Fourier transform mode.6–11 In order to obtain quantitative information from a photoacoustic spectrum (as would be needed to monitor kinetics of surface reactions or for analytical purposes) it is necessary to convert the single beam spectrum into a double beam spectrum by ratioing against the spectral profile of the source radiation as it impinges on the sample. This is called source normalization.

The effect of phloretin on red cell nonelectrolyte permeability.

SummaryThe effect of phloretin on permeability of small nonelectrolytes into human red cells was shown to be bimodal for hydrophilic molecules and nonbimodal for lipophilic molecules. At low phloretin concentrations (<0.1mm) hydrophilic as well as lipophilic nonelectrolyte permeation was increased. At high phloretin concentrations (>0.1mm) the permeability of hydrophilic molecules was decreased, whereas lipophilic molecule permeability continued to be increased. These results suggest that the mechanism for phloretin acting on red cell nonelectrolyte pathways is different for hydrophilic molecules, as compared to lipophilic permeant molecules. The pH of the red cell buffer suspension also influenced the effect of phloretin on nonelectrolyte permeability and the keto or un-ionized form of phloretin (present at low pH), which is known to have a greater affinity for the membrane, had a larger effect on hydrophilic nonelectrolyte permeability than the ionized form of phloretin.

Kinetics of octylphenyl polyoxyethylene alcohol micelle dissociation by a stopped-flow technique

Abstract The kinetics of dissociation of micelles of the nonionic detergent octylphenyl polyoxyethylene alcohol in aqueous solution and in 0.1 M KCl at 25° were studied by a stopped flow technique. The rate constant of dissociation of the first detergent molecule from the micelle, kn, n-1, was found equal to 510 sec−1. A value of 73 sec−1 for kn, n−1 had been found previously, using a temperature jump technique. These results suggest that the rate determining step seen in a temperature jump experiment is not the release of the first molecule of detergent from the micelle.

Quantitative Determination of Catalytic Surface Adsorption Sites by Fourier Transform Infrared Photoacoustic Spectroscopy

The use of Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) as a method for quantitative analysis of surface adsorption sites is demonstrated. Mid-IR information about the amount of adsorption is available with the sampling advantages of PAS: ability to analyze opaque materials with minimal sample preparation, qualitative information about both gas [CO(g)] phase and adsorbed [CO(ads)] species, a sealed sample environment for control of the gas phase in contact with the sample, and the ability to monitor in situ reaction kinetics. In this study a calibration curve is constructed for the amount of CO(g) in the sample cell with a silica internal reference. This calibration curve is utilized to calculate the amount of CO(ads) by subtraction on a catalytic surface where both CO(g) and CO(ads) exist at equilibrium. Using standard parameters from gas titration/volume uptake studies, the surface covered and the percentage of active sites on the surface are determined. This analysis combines the qualitative analytical capabilities of PAS with quantitative analysis, thus demonstrating another facet of the usefulness of FT-IR/PAS in addressing unusual problems.