Nanoplasmonics and surface enhanced spectroscopy

Temperature driven plasmon-exciton coupling in thermoresponsive dextran-graft-PNIPAM / Au nanoparticles / CdTe quantum dots hybrid nanosystem
Yeshchenko O.A.1, Khort P.S.1, Kutsevol N.V.2, Kapush O.3, Dzhagan V.1,3
1Physics Department and 2Chemistry Department, Taras Shevchenko National University of Kyiv, 60 Volodymyrs'ka str., 01601 Kyiv, Ukraine. 
E-mail: yes@univ.kiev.ua
2 V. Ye. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, 45 Nauky ave., 03028 Kyiv, Ukraine.

The temperature driven plasmon-exciton coupling in thermoresponsive dextran-graft-PNIPAM / Au nanoparticles / CdTe quantum dots (D-g-PNIPAM / Au NPs / CdTe QDs) hybrid nanosystem was studied. A significant (0.84 eV) splitting of the absorption peak was observed in the absorption spectrum of the nanosystem, which reflects the fact of formation of plexcitons, occurring due to strong plasmon-exciton coupling. An increasing with time plasmonic enhancement of the photoluminescence of CdTe QDs was revealed, as a result of the penetration of quantum dots into the volume of the D-g-PNIPAM / Au NPs hybrid nanosystem and bonding to it. The heating-cooling cycle of the aqueous solution of the studied nanosystem leads to a reversible quenching-recovery alteration of the QD photoluminescence. The quenching was rationalized as a result of an increased probability of nonradiative resonance energy transfer (RET) from CdTe QDs to Au NPs, which occurs due to shortening of the NP-QD distance, caused by shrinking of the macromolecule due to cooling-induced lower critical solution temperature phase transition. Increasing the NP-QD distance in the heating stage recovers the QD PL intensity. The observed effect opens up opportunities for the controlled reversible temperature-driven tuning of the photoluminescence intensity of D-g-PNIPAM / Au NPs / CdTe QDs nanosystem, which is highly important for its potential use in photonics and biomedical applications.