In the present study, two types of gelatin, fish gelatin and bovine gelatin, were used as dispersing medium to prepare nano-sized AgBr/I particles. It showed that thermostability and monodispersity of nano-particles formed in the fish gelatin colloid medium were significantly higher than that in the bovine one, indicating stronger colloid protective power of the fish gelatin to retard the particle growth and aggregation. The positron annihilation lifetime spectra (PALS) of the two gelatin samples obtained by positron annihilation technique (PAT) demonstrated that the lifetime of the long-lived component of positrons for the fish gelatin sample was longer than that for the bovine one, but its intensity for the fish gelatin sample was lower than that for the bovine one, implying smaller in size and lower in concentration of free-volume holes in the fish gelatin macromolecules by comparison with the bovine gelatin. It means that the fish gelatin can much more effectively protect nanoparticles against the growth and coalescence.
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