(150d) Investigation of Tethered Thermoresponsive N-Isopropylacrylamide Hydrogel Thin Films Via the Incorporation of Cadmium Selenide/Zinc Selenide Nanoparticles

Semiconductor quantum dots (QDs) are highly luminescent nanocrystals that exhibit narrow emission wavelengths tunable by changing the nanoparticle diameter and elemental components. Incorporation of QDs into a cross-linked hydrophilic polymer matrix forms an optically active scaffold. The QDs can be incorporated into the polymer matrix through hydrogen bonding, covalent attachment to the preformed polymer matrix, and/or in-situ gelation using the QDs as a cross-linking agent. The polymer matrix can be selected such that it undergoes rapid volume changes to external stimuli gradients such as temperature or pH, due to a balance between polymer elastic energy and osmotic pressure. For surface-confined thin films, volume changes are known to occur in the millisecond regime, a timescale ideal for actuator and sensor applications. The importance of these hydrogel-nanoparticle hybrid materials is twofold, (i) utilization of the QD emission in biosensing configurations, and (ii) characterization of the polymer matrix and cross-link junction dynamics through the use of optical techniques such as surface plasmon resonance (SPR) and fluorescence correlation spectroscopy (FCS). Here we report the incorporation of CdSe/ZnSe semiconductor QDs into temperature sensitive N-isopropylacrylamide copolymer thin films, and the analysis of the materials optical properties as a function of polymer conformation for thin tethered films.