2 research outputs found
Mechanism and Kinetics of JâAggregation of Thiacyanine Dye in the Presence of Silver Nanoparticles
The
aim of the present work was to elucidate the binding mechanism
and kinetics of anionic cyanine dye 3,3â˛-disulfopropyl-5,5â˛-dichlorothiacyanine
sodium salt (TC) J-aggregation on the surface of silver nanoparticles
(AgNPs, particle size âź6 nm). The hybrid J-aggregateâAgNPs
assembly was characterized by TEM analysis, UVâvis spectrophotometry,
and fluorescence measurements. In the elucidation of TC binding on
the surface of AgNPs, they were considered as macromolecules with
several binding sites and TC dye was considered as a ligand. Scatchard
and Hill analysis revealed that TC binding was a random process rather
than cooperative, with âź200 bonded TC molecules per AgNP and
a binding constant <i>K</i><sub>a</sub> = 4.8 Ă 10<sup>7</sup> M. The TCâAgNP assembly exerted concentration-dependent
fluorescence quenching properties. The linearity of the SternâVolmer
relation, accounting for both static and dynamic quenching, indicated
that only one type of quenching occurred, suggesting that AgNPs quenched
the fluorescence of TC with an extraordinarily high SternâVolmer
constant (<i>K</i><sub>SV</sub>) in the range of 10<sup>8</sup> M<sup>â1</sup>. Additionally, the kinetics of J-aggregation
of TC in the presence of AgNPs was studied using a stoppedâflow
technique. Kinetic measurements were performed as a function of the
TC and AgNP concentration, yielding sigmoidal kinetic curves. The
concentration dependence of the parameters of the kinetic curves indicated
that J-aggregate formation on the AgNP surface occurred via a two-step
process; the first was adsorption of the initial dye layer, followed
by the growth of consecutive layers
Kinetics of J-Aggregate Formation on the Surface of Au Nanoparticle Colloids
The kinetics of J-aggregate assembly on the surface of
noble metal
nanoparticle colloids are described, providing new mechanistic insight
into the interaction of the dye molecules with the surface of metal
nanoparticles. We specifically studied the J-aggregation of a thiacyanine
dye (TC, 3,3â˛-disulfopropyl-5,5â˛-dichlorothiacyanine
sodium salt) on the surface of gold nanoparticle colloids. The hybrid
J-aggregateâAu colloidal dispersions were characterized by
UVâvis spectrophotometry, fluorescence measurements, zeta potential
measurements, and TEM analysis. Kinetic measurements were carried
out using a stopped-flow method, indicating that the J-aggregate formation
on the surface occurs via a two-step process. The first step includes
adsorption of the initial dye layer, followed by an order of magnitude
slower growth of consecutive layers. Activation parameters determined
from the fluorescence measurements yielded further details about the
nature of the interaction