S. I. Belopushkin

Reduction of copper(II) ions in polyacrylic acid-polyethyleneimine complexes using X-ray radiation

The specifics of X-ray-induced reduction of copper(II) ions in the polyacrylic acid-polyethyleneimine-copper(II) (PAA-PEI-Cu2+) complexes were studied. It was found that the action of radiation led to the effective reduction of Cu2+ in the PAA-PEI-Cu2+ films swollen in an aqueous-alcohol medium. The formation of metal nanoparticles in irradiated samples was revealed by electron microscopy and X-ray diffraction techniques. Analysis of ESR data has demonstrated that the Cu2+ reduction rate increases with an increase in the initial concentration of copper ions in the samples. Formal yields of the radiation-chemical reduction of Cu2+ in the PAA-PEI complex films were found to be quite high (>100 ions per100 eV of energy absorbed by the swollen film), which can be explained by involvement of the radiolysis products of aqueous alcoholic solutions (outer medium) in the reduction processes.

The formation of metal nanoparticles in polyacrylic acid-polyethyleneimine complex upon reduction of copper(II) ions using X-ray irradiation

The features of nanoparticle formation by the radiation-chemical reduction of Cu2+ ions in polyacrylic acid-polyethyleneimine complexes have been studied. It has been shown that the swollen film/aqueous alcohol medium interphase exchange of the reducing species and the specifics of X-ray energy transfer play an important role in the formation of metal particles in the subsurface layer of polymer matrixes. An analysis of EPR and X-ray diffraction data shows that an acetaldehyde admixture increases the Cu2+ reduction rate of and enables the growth of nanoparticles.

Reactions of the radical cations of aliphatic aldehydes in freon matrices

ESR spectra of γ-irradiated, at −196 °C, solutions of acetic and propionic aldehydes in freon-11 and freon-113 affected by aldehyde concentration, temperature, and the action of light have been studied. It has been shown that the radical cations CH3CHO+ are converted into neutral radicals CH3ĊO and CH3ĊHOH and the cations CH3CH2CHO+. are converted to RĊO and CH3ĊHCHO due to ion-molecular reactions of proton transfer /CH3ĊO and CH3ĊHCHO/ of hydrogen atom transfer /CH3ĊHOH/.

Reactions of the radial cattions of acetic acid and acetic anhydride in CFCl3

The ESR spectra of γ-irradiated, at −196 °C, solutions of acetic acid and acetic anhydride were studied depending on their concentrations in CFCl3. The structure of thus produced radical cations is confirmed with the deuterium substituted analogues. It has been shown that the ion-molecular reaction of the radical cation CH2COOH+ in the isolated dimer takes place for the dilute solutions of acetic acid in CFCl3 resulting in the formation of CH3COO follwed by its decomposition to CH3+CO2 while the radicals CH2COOH are formed via secondary processes. The reactions of radical cations of acetic oxide have been also studied.

Formation of radicals in the liquid and solid-phase radiolysis of esters studied by spin trapping

The radiolysis of some esters /formates and acetates/ has been studied both in liquid and in solid states using a number of different spin traps. Specific deuteration was applied to elucidate the mechanism of radical formation. The radicals were found to result from the reactions of ester radical cations, radical anions and excited molecules. Evidence for intramolecular rearrangement in the radical cations of esters in condensed phase was obtained.

Stabilization and reactions of tetramethylurea radical cations in Freon matrices at 77 K: Intramolecular hydrogen transfer, ion-molecular reactions, and fragmentation by electron spin resonance study

ESR spectra for γ-irradiated at 77 K solutions /0.02–16%/ of tetramethylurea /TMU/ in CFCl3 and Freon-113 have been studied. TMU+. radical cations radiolytically produced in dilute solutions have been shown to undergo intramolecular hydrogen transfer upon photobleaching resulting in CH2N= type radical. Evidence for intermolecular proton transfer in TMU+. radical cations after annealing to phase transition temperature /110–120 K/ in Freon-113 was obtained. Primary radical cations of TMU+. at their ground state take part in ion-molecular reaction via proton transfer. Molecular cations in their excited states may undergo fragmentation producing Me2N radicals, which were trapped in liquid phase by t-BuNO as a spin trap.

FORMATION AND REACTIONS OF MONOMERIC AND DIMERIC RADICAL CATIONS OF ALIPHATIC KETONES IN FREON MATRICES

ESR spectra of γ-irradiated, at 77 K, acetone and CH3COEt solutions /0.1–22%/ in CFCl3 were studied. The yields of monomer and dimer radical cations of ketones and RCHCOCH3 radicals depend on ketone concentration in CFCl3. When exposed to light the dimeric radical cations are transformed into RCHCOMe, while the monomeric radical cations disappear without further radical production. Different types of solid phase ion-molecular reaction for monomer and dimer radical cations are discussed.