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Light-Selective Nanofilms of Quantum Dot-Poly(ethylene-co-vinyl acetate) Synthesized with Supercritical CO2

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journal contribution
posted on 23.04.2009, 00:00 by William Z. Xu, Paul A. Charpentier
The synthesis of polymer nanocomposites with incorporated quantum dots (QDs) has been attracting significant interest due to their unique applications in a variety of fields. Here we explored the synthesis and characterization of novel QD-poly(vinyl acetate) (PVAc) and poly(ethylene-co-vinyl acetate) (PEVA) nanocomposites for application as light-selective nanofilms. Both CdS and CdS-ZnS core−shell QDs were synthesized by means of pyrolysis of single molecular precursors at 180 °C, and then functionalized with a methoxysilane group for subsequent attachment to polymer chains by using sol−gel chemistry. These novel materials were examined with FTIR, EDX elemental analysis, solubility tests, photoluminescence, and UV−vis spectroscopy for characterization of the QDs, indicating successful synthesis and functionalization. The functionalized QDs were then used to synthesize novel QD-PVAc and QD-PEVA nanocomposites via a one-pot technique in supercritical carbon dioxide (scCO2), which acts as a solvent and drying agent for the sol−gel chemistry linking the QDs to the polymer chains. In the synthesis of QD-PVAc, the characteristic emission peak of the QDs was quenched attributed to phase separation in the nanocomposites. By stabilizing the QDs with an excessive amount of ligands and controlling the reaction conditions, light-selective QD-PEVA nanofilms were successfully synthesized by using a two-step technique in scCO2. The synthesized QD-PEVA nanofilms displayed significant absorption in the UV and violet regions of the electromagnetic spectrum, while providing a characteristic emission in the region from orange to red light. This novel synthesis route can be applied to the synthesis of other light-selective nanofilms by varying the quantum dot and polymer systems.