The techniques of gamma-radiolysis, UV photolysis and hydrogen-induced reduction of aqueous palladium perchlorate to ultrafine particles of Pd,.
Journal of Radioanalytical and Nuclear Chemistry, Vol. 256, No. 3 (2003) 565–569
Preparation of alumina stabilized aqueous Pd colloid by reduction using gamma-radiolysis, UV-photolysis and H2 S. C. Tripathi,1* M. Kumar2 2 Radiation
1 Fuel Reprocessing Division, Chemistry and Chemical Dynamics Division, Bhabha Atomic Research Centre, Mumbai - 400 085, India
(Received December 4, 2002)
The techniques of gamma-radiolysis, UV photolysis and hydrogen-induced reduction of aqueous palladium perchlorate to ultrafine particles of Pd, in the presence of alumina sol, have been studied. As compared to H2-induced reduction, both UV photolytic and gamma-radiolytic reduction methods lead to a very stable, brown colored Pd colloid with relatively less absorption in the higher wavelength region and possessing much smaller volume average particle size (62 and 61 nm, respectively). Higher concentration of alumina sol and increase in pH from 1.8 to 7.2, favour the formation of smaller sized particles as determined by the dynamic light scattering technique.
Introduction Small metal clusters are of great interest because of their non-linear optical and special catalytic properties. Palladium possesses unique properties as a metal and stabilized ultra-fine particles, which trigger and catalyse various chemical synthesis of industrial importance. Hence, special research interests have been witnessed all over the world for studying the formation and novel chemical applications of ultra-fine palladium metal particles in colloidal form and on various inorganic supports.1–4 Among various techniques, radiolytic and photolytic reduction of aqueous metal ions are important methods for producing homogeneous dispersions of metal clusters. Such reduction studies, with both singleand multi-metallic composite systems, have been reported.5–10 Generally, characteristics of the metal colloids produced by various methods depend upon various factors such as the nature of precursor chosen for reduction, the type of reducing species involved in the reduction technique, the rate of formation of the reducing species, the nature and the concentration of the stabilizer used as well as the pH of the solution etc. In the present study, gamma-radiolytic, UV photolytic and hydrogen-induced reduction of aqueous palladium perchlorate to ultra-fine particles of palladium in the presence of alumina sol has been studied. The effect of pH and alumina sol concentration on the formation of Pd particles has been investigated using optical absorption spectra and dynamic light scattering techniques. Experimental Palladium chloride (BDH), iso-propanol (SISCO Res. Lab., India) and spectrograde acetone (Spectra, India) were used. Palladium perchlorate was prepared by
dissolving PdCl2 in HCl and fuming it repeatedly with perchloric acid until a solution, with typical absorption maximum at 379 nm was obtained.11 Alumina sol was prepared by the hydrolysis of aluminum isopropoxide, as reported in the literature.12 All other chemicals used were of G.R. or AnalaR grade and were generally used as received. Water purified with a nanopure system (conductivity
