Farmaceutico

Various approaches to separation, recovery, and redispersion
of high-value colloids, such as ultracentrifugation, 2 solvent
evaporation,3 the addition ofantisolvent CO2,4 and temperature
control,5,6 are being actively investigated. More recently, the
flocculation of NPs has been induced by UV light. 7 QuantumsizedCd-NPs have been applied as semiconductors and Zn-NPs
have found a number of technological applications (e.g., in thin
film electroluminescent devices,8,9 thephotochemical production
of hydrogen in solar cells,10 and IR windows11). Therefore, it is
particularly important to investigate novel separation and recoverymethods in order to reuse valuable nanomaterials.
A number of synthesis routes are routinely employed for the
preparation of stable NPs,12-14 andwater-in-oil (w/o) microemulsions
(MEs) are a suitable reaction medium for the nucleation
and growth ofNPs. The size and shape of the colloids can be
controlled bychanging the surfactant nature or system composition.
12 Water-in-decane (w/d) MEs can be readily formulated to
display liquid-liquid (L-L)-type phase separationabove a
critical temperature Tc: for T > Tc the systems resolve cleanly
into two coexisting ME phases, each with essentially the same
droplet size but havingdifferent volume fractions (φ).1 In this
work,AOT-stabilized CdS and ZnS NPs, incorporated intoAOT
w/d MEs, are cleanly separated and concentrated simply byemploying a critical-type L-L phase transition. This approach
is simple and can be potentially applied generally toNPs dispersed
in a supporting colloidal fluid.