RADIOLYTIC PRODUCTION OF METALLIC NANOCLUSTERS IN A QUATERNARY MICROEMULSION SYSTEM S. Kapoor, S. Adhikari, C. Gopinathan, and J.P. Mittal* 1 Chemistry Group, Bhabha Atomic Research Centre, Mumbai 400 085, India (Communicated by C.N.R. Rao) (Received July 3, 1998; Accepted September 23, 1998) ABSTRACT The reduction of CdSO 4 , {Pd 3 [SSP(OC 2 H 5 ) 2 ](Ph 3 P) 2 S 2 }, CuCl, and CuSO 4 has been investigated using pulse and gamma radiolysis technique in water- in-oil microemulsion. Rate constants for the reduction of these compounds by e 2 (aq) were found to be much lower, compared to those for the same compounds in aqueous solution. The bimolecular rate constants were corre- lated with the “water-pool” size, location of the compounds, and surrounding environment. After the compounds were bombarded by a large number of electron pulses, the formation of colloidal Cd, Cu, and Pd was observed. The formation of colloidal Cu was faster in the case of CuCl than in that of CuSO 4 . Morphologies of colloidal Cd and Pd were determined by electron micros- copy. © 1999 Elsevier Science Ltd KEYWORDS: A. nanostructures, C. electron microscopy INTRODUCTION The high specific area of metallic microaggregates, with their ability to transfer electrons readily to corresponding bulk metals, makes this highly dispersed state of matter important in several diversified fields, such as catalysis, photography, and optics [1,2]. Different techniques have been employed for preparing these particles [3–16]. Recently, it was shown [17] that the size and shape of the particles can be controlled by choosing a suitable ratio of the concentration of capping polymer material to the concentration of metal ion. Inverse *To whom correspondence should be addressed. Fax: 191-22-5505151 or 5519613. E-mail: mittaljp@ magnum.barc.ernet.in. Materials Research Bulletin, Vol. 34, No. 8, pp. 1333–1343, 1999 Copyright © 1999 Elsevier Science Ltd Printed in the USA. All rights reserved 0025-5408/99/$–see front matter PII S0025-5408(99)00126-9 1333