Ks. Mayya et al., An optical absorption investigation of cross-linking of gold colloidal particles with a small dithiol molecule, B CHEM S J, 73(8), 2000, pp. 1757-1761
The controlled aggregation of colloidal metal particles is a problem of tec
hnological importance in the generation of, for example, quantum wires. In
this communication, we present results of an optical absorption spectroscop
y investigation of the flocculation of gold colloidal particles capped with
a small bifunctional molecule (1,3-propanedithiol). The self-assembly of t
he dithiol molecule on the gold surface leads to thiol surface functionaliz
ation of the colloidal particles, which may thereafter be used to chemicall
y cross-link the gold clusters. Optical absorption measurements performed i
mmediately after capping the gold colloidal particle surface with the dithi
ol molecules clearly show the growth of a long-wavelength component, indica
ting that the clusters aggregate in open string-like structures. Increasing
the surface coverage of the dithiol molecules on the clusters leads to a g
reater flocculation rate, but prevents the formation of large gold clusters
in direct contact, as indicated by X-ray diffraction measurements of the a
ggregates. This approach of controlled cross-linking of colloidal particles
may have important applications in the generation of metal cluster network
s.