Photo- and radiation-induced preparation of nanocrystalline copper and cuprous oxide catalysts

Spherical copper nanoparticles have been prepared by photo- or radiation-induced reduction of aqueous solutions containing 10-3 mol.dm-3 copper sulphate or formate, 1.3 mol.dm-3 propan-2-ol and polyvinyl alcohol as a stabilizer. Increase of initial copper concentration to 10-2 mol.dm-3 resulted in formation of different reaction product-octahedral cuprous oxide nanoparticles. Solutions were irradiated by means of electron beam, 60Co γ rays (dose rate 70 Gy.h-1) or by 400 W medium-pressure mercury lamp and were characterised by UV-Vis spectrophotometry, X-Ray Powder Diffraction, TEM and SEM. Pink to violet colour of colloidal copper solutions corresponded to measured copper surface plasmon band at circa 580 nm and has been found to be very sensitive to oxygen, which causes dissolution of particles. Therefore, the influence of purging by nitrogen gas prior to irradiation was thoroughly examined and has been found to only hinder, not alter irradiation effects. Moreover, the evolution of absorption spectrum of colloidal copper solution in contact with air has been measured, revealing interesting non-monotonous dependence on the air exposure time, probably caused by formation of protective oxide layer. Catalytic activity of prepared cuprous oxide has been measured by catalytic decomposition of hydrogen peroxide and has been found to be higher or comparable to commercial cuprous oxide. (author)