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Does shining light on gold colloids influence aggregation?

Bhattacharya S, Narasimha S, Roy A, Banerjee S - Sci Rep (2014)

Bottom Line: In the literature, the electrostatic interactions, van der Waals interactions, and the change in free energy due to ligand-ligand or ligand-solvent interactions are mainly considered to be the dominating factors in determining the characteristics of the gold aggregates.However, our light scattering and imaging experiments clearly indicate a distinct effect of light in the growth structure of the gold colloidal particles.We attribute this to the effect of a non-uniform distribution of the electric field in aggregated gold colloids under the influence of light.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Indian Institute of Technology Kharagpur, India.

ABSTRACT
In this article we revisit the much-studied behavior of self-assembled aggregates of gold colloidal particles. In the literature, the electrostatic interactions, van der Waals interactions, and the change in free energy due to ligand-ligand or ligand-solvent interactions are mainly considered to be the dominating factors in determining the characteristics of the gold aggregates. However, our light scattering and imaging experiments clearly indicate a distinct effect of light in the growth structure of the gold colloidal particles. We attribute this to the effect of a non-uniform distribution of the electric field in aggregated gold colloids under the influence of light.

No MeSH data available.


Variation of Df with concentration as obtained from light scattering measurements (red symbol).Df as obtained from 3D simulation are shown by black symbols. The solid lines are the fit to the data points with the same exponent 0.36. Inset of the figure shows the measured I(q) vs q plots for different concentrations of the sol. Solid lines are fit to the data points using I(q) = A(qRg)−Df.
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f4: Variation of Df with concentration as obtained from light scattering measurements (red symbol).Df as obtained from 3D simulation are shown by black symbols. The solid lines are the fit to the data points with the same exponent 0.36. Inset of the figure shows the measured I(q) vs q plots for different concentrations of the sol. Solid lines are fit to the data points using I(q) = A(qRg)−Df.

Mentions: In several reports2 only DLVO type potentials are used to describe fractal characteristics obtained from scattering measurements. To investigate the extent up to which it is valid, we have carried out static light scattering measurements on gold sol of different concentrations. We record I(q) for different values of q for sols of different concentrations (inset of Fig. 4) using λ = 633 nm. We fit our data set for each concentration with the equation I(q) = A(qRg)−Df, (where A is a constant that depends on the average mass of the aggregates) keeping A, Rg and Df as free fitting parameters. The variation of Df with concentration, thus obtained, is shown in Fig. 4 by filled circles. To estimate the fractal dimension of the aggregates of gold particles in the sol we considered DLVO type of interaction potential between particles, in a BD simulation, based on translational diffusion motion of the particles. Details of the simulation are available in the supplementary section (S2). The variation of Df with volume fraction, thus simulated, is shown by the black asterisks in Fig. 4. Both the simulated and experimental data points follow very similar behavior and could be fitted with the same power law. Thus, we conclude that the Brownian dynamics simulation including DLVO type of interaction potential between gold particles in the sol qualitatively explains the short-range dynamics of self-assembled aggregates. Based on our observation reported in Fig. 2 and Fig. 3, we are of the opinion that the effect of light needs to be considered in order to understand the detailed morphology and characteristics of such self-assembled gold aggregates.


Does shining light on gold colloids influence aggregation?

Bhattacharya S, Narasimha S, Roy A, Banerjee S - Sci Rep (2014)

Variation of Df with concentration as obtained from light scattering measurements (red symbol).Df as obtained from 3D simulation are shown by black symbols. The solid lines are the fit to the data points with the same exponent 0.36. Inset of the figure shows the measured I(q) vs q plots for different concentrations of the sol. Solid lines are fit to the data points using I(q) = A(qRg)−Df.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4048914&req=5

f4: Variation of Df with concentration as obtained from light scattering measurements (red symbol).Df as obtained from 3D simulation are shown by black symbols. The solid lines are the fit to the data points with the same exponent 0.36. Inset of the figure shows the measured I(q) vs q plots for different concentrations of the sol. Solid lines are fit to the data points using I(q) = A(qRg)−Df.
Mentions: In several reports2 only DLVO type potentials are used to describe fractal characteristics obtained from scattering measurements. To investigate the extent up to which it is valid, we have carried out static light scattering measurements on gold sol of different concentrations. We record I(q) for different values of q for sols of different concentrations (inset of Fig. 4) using λ = 633 nm. We fit our data set for each concentration with the equation I(q) = A(qRg)−Df, (where A is a constant that depends on the average mass of the aggregates) keeping A, Rg and Df as free fitting parameters. The variation of Df with concentration, thus obtained, is shown in Fig. 4 by filled circles. To estimate the fractal dimension of the aggregates of gold particles in the sol we considered DLVO type of interaction potential between particles, in a BD simulation, based on translational diffusion motion of the particles. Details of the simulation are available in the supplementary section (S2). The variation of Df with volume fraction, thus simulated, is shown by the black asterisks in Fig. 4. Both the simulated and experimental data points follow very similar behavior and could be fitted with the same power law. Thus, we conclude that the Brownian dynamics simulation including DLVO type of interaction potential between gold particles in the sol qualitatively explains the short-range dynamics of self-assembled aggregates. Based on our observation reported in Fig. 2 and Fig. 3, we are of the opinion that the effect of light needs to be considered in order to understand the detailed morphology and characteristics of such self-assembled gold aggregates.

Bottom Line: In the literature, the electrostatic interactions, van der Waals interactions, and the change in free energy due to ligand-ligand or ligand-solvent interactions are mainly considered to be the dominating factors in determining the characteristics of the gold aggregates.However, our light scattering and imaging experiments clearly indicate a distinct effect of light in the growth structure of the gold colloidal particles.We attribute this to the effect of a non-uniform distribution of the electric field in aggregated gold colloids under the influence of light.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Indian Institute of Technology Kharagpur, India.

ABSTRACT
In this article we revisit the much-studied behavior of self-assembled aggregates of gold colloidal particles. In the literature, the electrostatic interactions, van der Waals interactions, and the change in free energy due to ligand-ligand or ligand-solvent interactions are mainly considered to be the dominating factors in determining the characteristics of the gold aggregates. However, our light scattering and imaging experiments clearly indicate a distinct effect of light in the growth structure of the gold colloidal particles. We attribute this to the effect of a non-uniform distribution of the electric field in aggregated gold colloids under the influence of light.

No MeSH data available.