Journal of Applied Crystallography

Volume 40, Supplement (April 2007)

External fields

J. Appl. Cryst. (2007). 40 (Supplement), s73-s77

A combined small-angle scattering study of a chemical reaction at specific sites and reaction-induced self-assembly as a problem in open non-equilibrium phenomena

T. Hashimoto, H. Tanaka, S. Koizumi, K. Naka and Y. Chujo

Abstract: As a problem in open non-equilibrium phenomena, small-angle scattering (SAS) studies of chemical reactions at specific sites and reaction-induced self-assembly of a system which is obtained by mixing two stable solutions of palladium acetate [Pd(OAc)₂] in N,N-dimethylformamide and the second-generation polyamidoamine dendrimer in methanol are presented. The self-assembly was studied using a combination of neutron and X-ray SAS. The results revealed that the self-assembly involves the initial formation of aggregates of an average radius of 20 nm composed of the dendrimers and Pd(OAc)₂ followed by formation of palladium nanoparticles of a radius of 2.0 nm inside the aggregates. The aggregates were found to provide a special field for a chemical reaction for reduction of Pd(II) ions with methanol and for the self-assembly of the reduction products of Pd(0) atoms into nanoparticles. The nanoparticles are found to be trapped and stabilized in the aggregates.

Keywords: SAXS; SANS; PAMAM; open non-equilibrium phenomena; stable solutions; self-assembly.