The aim of the present work was to elucidate the binding mechanism and kinetics of anionic cyanine dye 3,3′-disulfopropyl-5,5′-dichlorothiacyanine sodium salt (TC) J-aggregation on the surface of silver nanoparticles (AgNPs, particle size ∼6 nm). The hybrid J-aggregate−AgNPs assembly was characterized by TEM analysis, UV−vis 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 ∼200 bonded TC molecules per AgNP and a binding constant K a = 4.8 × 10 7 M. The TC−AgNP assembly exerted concentration-dependent fluorescence quenching properties. The linearity of the Stern−Volmer 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 Stern− Volmer constant (K SV ) in the range of 10 8 M −1 . Additionally, the kinetics of J-aggregation of TC in the presence of AgNPs was studied using a stopped−flow 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.
Fe-doped zinc oxide (Zn1-xFexO, x=0, 0.05, 0.1, 0.15 and 0.20; ZnO:Fe) nanoparticles were produced using an eco-friendly and rapid microwave processing of a precipitate and tested as catalysts toward oxygen...
The structure, absorption coefficient and electrical resistivity studies on
TiN thin films are presented. The film of thickness 240 nm was grown on Si
(100) substrate by DC reactive sputtering at an average deposition rate of ~8
nm/min. After deposition the samples were annealed for 1h at 600?C and 2h at
700?C in nitrogen ambient and vacuum furnace, respectively. Structural
characterizations were performed by Rutherford backscattering spectrometry
(RBS), X-ray diffraction (XRD) and transmission electron microscopy (TEM).
The optical properties were investigated by spectroscopic ellipsometry while
a four point probe was used for electrical characterization. It was found
that the post-deposition annealing of the films did not cause any variation
in stoichiometry, but strongly affects the structural parameters such as
lattice constant, micro-strain and grain size. The observed increase in the
grain size after annealing leads to significantly lower value of the
coefficient of absorption. These changes could be directly correlated with
variation of electrical properties of TiN thin films. [Projekat Ministarstva
nauke Republike Srbije, br. III 45005]
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