Phase behaviour study and spectroscopic characterization of quantum dots-polymer self-assembled aggregates

Abstract

Here we present a simple and flexible method for the synthesis MSA-capped CdTe QDs by coacervation with oppositely charged polyelectrolyte, poly(diallyldimethylammonium chloride) PDADMAC. A continuous series of different phases, from initially clear (C1) to turbid (T1) then precipitate (P), turbid (T2) and clear (C2) has been observed for QD solution upon increasing the concentration of polyelectrolyte solution. However, no such variation is observed in case of neutral PVP (Polyvinylpyrrolidone), indicating specific electrostatic interaction behind the observed phase behaviours. The morphologies and photoluminescence properties of the coacervates in the T1 and T2 regions were explored using field emission scanning electron microscopy (FESEM). These luminescent coacervates are quite stable in neutral and basic pH (pH- 6.7- 10), whilst, very much unstable in acidic pH (pH- 3-5). Ionic strength study of T1 and T2 region is carried out with NaCl. We have further demonstrated the efficient encapsulation of dyes and proteins – FITC, Rhodamine 6G, Nile blue, HSA and BSA into the colloidal droplets without any structural disruption. A simple system for encapsulation like the one presented here might be useful for a range of different application such as drug delivery, bioimaging and sensing.