0, (b) 2.6, (c) 8.7 and (d) 9.7; Radiation dose = 0.6 kGy . Influence of radiation dose Nucleation and aggregation processes in the formation of bimetallic nanoparticles could be affected by varying the absorbed dose. The rates of growth could be determined by probabilities of the collisions between several atoms, between one atom and a nucleus, and between two or more nuclei . At low radiation doses, the concentration of unreduced https://www.selleckchem.com/products/qnz-evp4593.html metal ions is higher than the nucleus concentration because of low reduction rate. Thus, the unreduced ions can ionize bimetallic nanoparticles to form large bimetallic ions before they undergo reduction and aggregation
processes to form even larger bimetallic nanoparticles. However, at higher doses, most of the metal ions are consumed during the nucleation process; therefore, the nucleus concentration is higher than the concentration of unreduced metal ions. As a result, the bimetallic nanoparticles are smaller in size at higher radiation doses . On the other hand, there is a possibility of inter- and intra-molecular crosslinking within the polymer molecules via radical interaction mechanism as secondary step in gamma-ray reduction. At higher doses, the polymer
becomes a more complex matrix due to the occurrence of inter- and intra-molecular hydrogen bonding as well as radical linkage initiated by gamma irradiation between the cyclic structure constituents of the polymer molecules Selleckchem Compound C . Therefore, it inhibits the aggregation
of colloidal nanoparticles resulting in the formation of smaller nanoparticles. For example, Rau et al. , in the synthesis of silver nanoparticles by gamma radiation in the presence of gum acacia, have found that as the irradiation dose increases the corresponding optical absorption PRKACG intensity increases with concomitant blue shifts. An increase in the intensity of optical absorption spectra indicates the increase of number of silver nanoparticles. In addition, the peak shift may be attributed to the change in particle size (Figure 7). Figure 7 Optical absorption spectra of silver nanoparticles. Optical absorption of samples when irradiated at (a) 1.0 kGy, (b) 2.0 kGy, (c) 4.5 kGy, (d) 12.0 kGy, (e) 18.0 kGy and (f) 24 kGy . It was reported that the radiation crosslinking of gum acacia molecules can directly affect the growth process of silver nanoparticles . It is important to mention here that we cannot generalize this for all kinds of polymers, for example in contrast with gum acacia, chitosan cannot find more facilitate the formation of Ag nanoparticles at higher doses and black precipitation was observed at a dose >20 kGy . However, for binary Al-Ni nanoparticles prepared by gamma radiation method the average size of particles decreased from 32.7 nm at 60 kGy dose to 4.4 nm at 100 kGy dose (Figure 8) . Figure 8 TEM images of colloidal Al-Ni nanoparticles. TEM images of Al-Ni nanoparticles at doses of (a) 60 kGy and (b) 100 kGy .