Some Mechanochemical Considerations on the Numbers of Spins Induced by Ultraviolet Light

Abstract

Abstract The number of spins/g (NOS) generated in a binary powder of glycolic acid and silica–alumina (SA) increased during ultraviolet (UV) irradiation. After stopping illumination, the NOS value was found to decrease up to a constant number of sping/g (CNS), which was remarkably greater than the NOS value obtained before UV irradiation. The CNS values, thus obtained, were influenced not only by the calcination temperature of SA (Tea) and by the atmosphere of storage, but also by the duration of UV irradiation (DI). The values of CNS obtained at a low Tca (below 400°C) were also influenced by the time interval between stopping shaking and the start of UV irradiation (ti). Values of NOS having attained CNS remained unchanged for a long period, but finally began to decrease. The duration of CNS (DCNS) was also affected by Tca, the atmosphere of storage, DI, and ti DCNS decreased when CNS increased, and became unchanged when CNS reached a constant value. Values of CNS and DCNS induced by UV light were also influenced by the size of SA particles and by the mechanical energy given by shaking or compressing. Such mechanochemical effects are available, at least for studying the generation mechanism of UV-induced surface activity, for an improvement of the reproducibility of physicochemical data obtained during or after UV irradiation, and for the method of obtaining materials of constant efficiency.