Nucleation silver concentration effect

The reduction of silver chloride by hydrazine shows some points of similarity to the action of hydroxylamine, but also some important points of difference (James, 34). An induction period was obtained with the unnucleated precipitates which, under some conditions, was relatively large. However, exposure of the precipitate to actinic light had only a small effect upon the induction period and upon the subsequent course of the reaction. Previous nucleation of the precipitate by the action of hydroxylamine decreased the induction period without eliminating it, and produced little or no effect upon the subsequent course of the reaction. Addition of the dye, 3,3 -diethyl-9-methylthiacarbocyanine chloride, produced no effect until the surface of the precipitate was more than half covered. Further increase in the amount of dye added produced an irregular decrease in the reaction rate. Gelatin decreased the reaction rate, but to a smaller extent than in the hydroxylamine reaction, and a minimum rate was not attained. As the gelatin concentration increased, more and more reduced silver appeared in colloidal form in the solution. 

The understanding of the basic mechanism of photolysis of silver halide is incomplete yet vital for the planning and interpretation of experiments. This fact is illustrated by the ramifications inherent in the contemporary discussions of the latent image in silver halide. There are the conventional Gurney-Mott mechanism (1) and the thermodynamic model ((5,9). We have described the Gurney-Mott model. The thermodynamic view envisages nucleation of a supersaturated concentration of silver atoms in silver halide as induced by light. Obviously the effect of external variables is quite different in the two mechanisms. 

Abstract Silver, palladium, and rhodium nanoparticles were prepared by heterogeneous nucleation in the interlamellar space of a layered kaolinite support. Disaggregation of the lamellae of nonswelling kaolinite was achieved by intercalation of dimethyl sulfoxide. The kaolinite was suspended in various metal precursor solutions and the adsorbed metal cations were reduced with NaBH4 The diameter of the silver particles (4-10 nm) prepared in this way depends on the initial Ag" " concentration. Palladium and rhodium particles were stabilized by polymers and by the lamellae of kaolinite. The effect of the molecular mass and the concentration of the polymers on the size of the particles... 

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