Page 117 - Science at the nanoscale

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June 9, 2009
5.3. Surface stabilisation
are dissolved separately in aqueous phase. Two microemulsions
of the same water content were then prepared and stirred together.
The frequent collisions of the reverse micelles would lead to 107 ch05
exchange of contents inside the water pool, thus initiating the
reaction. The final sizes of the nanoparticles prepared depend
mainly on the water content and intermicellar exchange rate. In
the literature, many nanoparticles prepared with narrow size dis-
tribution have been reported using microemulsion method.
Further Reading
G. Cao, Nanostructures and Nanomaterials – Synthesis, Properties and
Applications (Imperial College Press, 2004).
P. Atkins and J de Paula, Physical Chemistry, 7th Edition (Oxford
University Press, 2002).

Exercises
5.1. Once the nanostructures are agglomerated, the smaller the
individual nanostructures, the more difficult it is to sepa-
rate the agglomerates. Explain.
5.2. Molecules can adsorb onto surfaces in two ways —
“Physisorption” (i.e. physical adsorption) and “Chemisorp-
tion” (i.e. chemical adsorption). Discuss and distinguish
between the two.
5.3. In the discussion of catalytic activity, it is sometimes
argued that the activity will be highest when the strength
of adsorption on the catalyst surface is intermediate. Try
to rationale this argument — why shouldn’t the adsorp-
tion be strong, and what is the effect of nanometre size in
this aspect?
5.4. Discuss briefly the effect of addition of salts into a colloidal
mixture.