Smart fluorescent core/shell nanoparticles
Abstract
In this work, we have developed the coating of ZnO semiconductor nanoparticles (NPs) (quantum dots, QDs) by responsive polymer by performing the growing by controlled polymerization (ARGET-ATRP) of poly(N-isopropyl acrylamide) (PNIPAM) from the QDs surfaces. Each step of the synthesis process was monitored by FT-IR, UV-vis, and fluorescence spectroscopies, dynamic light scattering (DLS) and by high resolution transmission electron microscopy experiments. The influence of the polymerization time on the final photophysical properties of the nanomaterials was enlightened and could be attributed to the thickness the polymer shell. The responsive behavior of the ZnO/polymer nanohybrids was studied by DLS. Results obtained showed that below 32°C the core/shell nanoparticles were perfectly dispersible in water, while above that temperature they started to agglomerate. This phenomenon is related to the collapse of the polymer brushes at the surface of the QDs, and lead to hydrophobic surfaces which prevent their dispersion in water.