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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.


(a) Microscopic image of the colloidal droplet after evaporation of the solvent. The close-up optical microscopic views of the aggregates are recorded near the edge (white marked region) of the dried drop. Morphology of gold colloid fractals grown in (b) normal light and c) darkness. (d) DLA clusters as generated from simulation with sticking probability 0.1 with total length as 450 units and particle size as one unit.
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f2: (a) Microscopic image of the colloidal droplet after evaporation of the solvent. The close-up optical microscopic views of the aggregates are recorded near the edge (white marked region) of the dried drop. Morphology of gold colloid fractals grown in (b) normal light and c) darkness. (d) DLA clusters as generated from simulation with sticking probability 0.1 with total length as 450 units and particle size as one unit.

Mentions: We studied close-up views of gold colloidal aggregates. Drops of the above colloidal sol (diluted to 1:8 volume ratio) were transferred on a glass plate and were allowed to dry. Fig. 2(a) presents the characteristic image of the drop on the glass substrate after evaporation. The microscopic images are recorded at the edge of the dried drop [position shown as the white square in Fig. 2(a)]. The aggregates were grown both in light as well as in darkness. To grow the aggregate in darkness, the drop of the colloid was transferred on the plate just after the preparation and then was kept in dark approximately 10 hours till it fully dried, before exposing to light for imaging. In light the drops were fully dried within 4 hrs. Temperature and humidity of both sets were maintained same. Fig. 2(b) and (c) show characteristic optical microscopic images of the particle aggregates grown under the above conditions. It is clear from Fig. 2 that the morphology of the aggregate is different when grown in the presence and absence of light. In light, the general shape of the structure is characterized by perpendicular growths at different points of a main stem. On the other hand, in darkness, it is more like a snowflake-like growth around a nucleating area. We performed power spectral analysis of the microscopic images (details available in supplementary section, S1) to verify the length scale which defines the observed fractal features. The fractal dimension was estimated to be 1.7 ± 0.2 and 1.9 ± 0.2 for Fig. 2(b) and (c), respectively. The morphologies of the particle aggregates grown on NaOH treated glass plate and silicon substrate were observed to be very similar to that shown in Fig. 2, indicating that interactions between glass surface, the particles, and the medium do not play any major role in determining the observed morphology of the aggregates.


Does shining light on gold colloids influence aggregation?

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

(a) Microscopic image of the colloidal droplet after evaporation of the solvent. The close-up optical microscopic views of the aggregates are recorded near the edge (white marked region) of the dried drop. Morphology of gold colloid fractals grown in (b) normal light and c) darkness. (d) DLA clusters as generated from simulation with sticking probability 0.1 with total length as 450 units and particle size as one unit.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: (a) Microscopic image of the colloidal droplet after evaporation of the solvent. The close-up optical microscopic views of the aggregates are recorded near the edge (white marked region) of the dried drop. Morphology of gold colloid fractals grown in (b) normal light and c) darkness. (d) DLA clusters as generated from simulation with sticking probability 0.1 with total length as 450 units and particle size as one unit.
Mentions: We studied close-up views of gold colloidal aggregates. Drops of the above colloidal sol (diluted to 1:8 volume ratio) were transferred on a glass plate and were allowed to dry. Fig. 2(a) presents the characteristic image of the drop on the glass substrate after evaporation. The microscopic images are recorded at the edge of the dried drop [position shown as the white square in Fig. 2(a)]. The aggregates were grown both in light as well as in darkness. To grow the aggregate in darkness, the drop of the colloid was transferred on the plate just after the preparation and then was kept in dark approximately 10 hours till it fully dried, before exposing to light for imaging. In light the drops were fully dried within 4 hrs. Temperature and humidity of both sets were maintained same. Fig. 2(b) and (c) show characteristic optical microscopic images of the particle aggregates grown under the above conditions. It is clear from Fig. 2 that the morphology of the aggregate is different when grown in the presence and absence of light. In light, the general shape of the structure is characterized by perpendicular growths at different points of a main stem. On the other hand, in darkness, it is more like a snowflake-like growth around a nucleating area. We performed power spectral analysis of the microscopic images (details available in supplementary section, S1) to verify the length scale which defines the observed fractal features. The fractal dimension was estimated to be 1.7 ± 0.2 and 1.9 ± 0.2 for Fig. 2(b) and (c), respectively. The morphologies of the particle aggregates grown on NaOH treated glass plate and silicon substrate were observed to be very similar to that shown in Fig. 2, indicating that interactions between glass surface, the particles, and the medium do not play any major role in determining the observed morphology of the 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.