Res. Chem. Intermed.
, Vol. 32, No. 8, pp. 709–715 (2006)
Also available online - www.brill.nl/rci
Sonochemical synthesis of ruthenium nanoparticles
, K. VINODGOPAL
and FRANZ GRIESER
Particulate Fluid Processing Center, School of Chemistry, University of Melbourne, Parkville,
Vic 3010, Australia
Department of Chemistry, Indiana University Northwest, Gary, IN 46408, USA
Received 12 January 2006; accepted 24 April 2006
Abstract—Ruthenium nanoparticles have been prepared by sonochemical reduction of a ruthenium
chloride solution using ultrasound frequencies in the range 20–1056 kHz. The reduction was
monitored by UV-Vis absorption spectrophotometry. Reduction proceeds sequentially from Ru(III)
to Ru(II) to Ru(0) and takes almost 13 h. The Ru particles produced by the ultrasound reduction have
diameters between 10 and 20 nm as measured by transmission electron microscope image.
Keywords: Ruthenium reduction; nanoparticles; sonochemistry; ultrasound; UV-Vis spectroscopy.
The sonochemical synthesis of metal nanoparticles, such as gold and platinum, by
now is well established. Several research groups have shown that ultrasound irradi-
ation of aqueous solutions containing noble metal salts produce the corresponding
colloids of the noble metal [1–5]. Whilst in most cases the exact mechanisms for
the reduction of metal complexes remain unclear, the ultrasound induced reduc-
tion is a consequence of acoustic cavitation in solution. The high temperatures and
pressures that occur within a collapsing bubble due to acoustic cavitation cause ho-
molytic dissociation of water and other species to produce reducing radicals .
In the presence of a colloid stabilizer, such as SDS, ultrasound reduction can pro-
duce nanometer-sized particles of metal colloids such as platinum, palladium, silver
and gold. Okitsu and others have demonstrated that the size of the metal parti-
cles is determined by the rate of reduction, with faster rates giving rise to smaller
particles . This reduction rate is then determined by a number of factors: the
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