Laser synthesis of bimetallic nanoalloys in the vapor and liquid phases and the magnetic properties of PdM and PtM nanoparticles (M = Fe, Co and Ni).

Abdelsayed, Victor; Glaspell, Garry; Nguyen, Minh; Howe, James M.; Samy
El-Shall, M. Department of Chemistry, Virginia Commonwealth
University, Richmond, VA, USA. Faraday Discussions (2008),
138(Nanoalloys), 163-180.

In this work, we present several examples of the synthesis and
characterization of bimetallic nanoparticle alloys using the Laser
Vaporization Controlled Condensation (LVCC) method. In the first
example, the vapor phase synthesis of Au-Ag, Au-Pd, and Au-Pt
nanoparticle alloys are presented. The formation of nanoalloys is
concluded from the observation of one plasmon absorption band at a
wavelength that varies linearly with the gold mole fraction in the
nanoalloy. Both XRD data and HRTEM-EDX data confirm the formation of
nanoparticle alloys and not simply mixts. of the two metal
nanoparticles. Irradn. of a mixt. of Au/Ag nanoparticles dispersed in
water with the 532 nm unfocused laser results in efficient alloying
while the 1064 nm laser radiation results only in evapn. and size redn.
of the unalloyed nanoparticles. Selective absorption of the femtosecond
780 nm radiation by large Au aggregates results in the formation of
smaller aggregates with fractal structures, and no evidence for the
Au-Ag alloy formation. The synthesis of palladium and platinum
nanoparticles alloyed with transition metals such as iron and nickel
using the LVCC method is also presented. The alloyed nanoparticles
(FePd, FePt, NiPd, NiPt, and FeNi) are found to be superparamagnetic.