Scattering on Aggregates

1 Scattering on Aggregates in the Rayleigh-Debye-Gans Limit 

1 Rayleigh-Debye-Gans (RDG) Scattering of Single A regates 

The factor PCq) or its orientation average Pig) is called form factor. 

For instance, the optical contrast for silica particles suspended in water is mr 1 0.09 the analogue value for titania particles is approx. 1. Hence, RDG scattering cannot, in principle, be applied to titania suspension. It is, however, possible to assume Rayleigh scattering when the titania particles are very fine (ka 1, x 50 nm). In contrast, optical scattering in aqueous silica suspensions can be approximated by RDG scattering for particle sizes up to 200 nm. 

In this equation, 7sca p is the scattering intensity of the primary particles, which is proportional to the form factor P(q) when RDG scattering applies. The factor agg(q) reflects the aggregate structure and depends on the aggregate orientation. 

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Light Scattering on Aggregates with Intracluster Multiple Scattering... 

Nikoobakht, B. and El-Sayed, M.A. (2003) Surface-enhanced Raman scattering studies on aggregated gold nanorods. Journal of Physical Chemistry A, 107,... 

Flocculation studies (6) indicated that the mechanism of steric stabilization operates for the PMMA dispersions. The stability of PMMA dispersions was examined further by redispersion of the particles in cyclohexane at 333 K. Above 307 K, cyclohexane is a good solvent for PS and PDMS, and if the PS-PDMS block copolymer was not firmly anchored, desorption of stabilizer by dissolution should occur at 333 K followed by flocculation of the PMMA dispersion. However, little change in dispersion stability was observed over a period of 60 h. Consequently, we may conclude that the PS blocks are firmly anchored within the hard PMMA matrix. However, the indication from neutron scattering of aggregates of PS(D) blocks in PMMA particles may be explained by the observation that two different polymers are often not very compatible on mixing (10) so that the PS(D) blocks are tending to... 

Schematic representations, like those shown in the Scheme 1, are very useful to indicate the chemical composition of the various species and to discuss the interaction between the various building blocks. Furthermore, as one can understand from the representations shown in Figures 9 and 10, the species with high nuclearity exhibit a ttu-ee-dimensional branching structure of the type of those shown by otherwise completely different dendrimers based on organic components. Therefore, endo- and exo-receptor properties can be expected, which are currently under investigation. Furthermore, aggregation of decanuclear complexes has also been demonstrated by dynamic light-scattering and conductivity experiments. Systematic studies on aggregation properties have, however, not been performed yet.

Zou, X. Q. and Dong, S. J. (2006). Surface-enhanced Raman scattering studies on aggregated silver nanoplates in aqueous solution. J. Phys. Chem. B 110 21545-21550. 

Bosnick KA, Jiang J, Brus LE (2002) Fluctuations and local symmetry in single-molecule Rhodamine 6G Raman scattering on silver nanocrystal aggregates. J Phys Chem B 106 8096... 

Kneipp K, Kneipp H (2006) Surface-enhanced Raman scattering on silver nanoparticles in different aggregation stages. Isr J Chem 46(3) 299-305... 

Kimura H, Kolokolova L, Mann I Optical properties of cometary dust constraints firom numerical studies on light scattering by aggregate particles, Astron Astrophys 407(1) L5-L8, 2003. 

Rarity, J.G. and Pusey, P.N. (1986). Light scattering from aggregating systems static, dynamic (QELS) and number fluctuations. In On Growth and Form, Stanley, H.E. and Ostrowsky, N. (eds). Martinus Nijhoff, Boston, MA, pp. 218-222. 

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