Optical properties of US nanocrystal covered by polymer chains on the surface

We prepared novel CdS nanocrystal by colloid technique; CdS nanocrystal possessing polyethylene glycol tethered chains (PEG-TC) on the surface. A relatively sharp optical absorption peak was observed at around 3.4 eV. The size of the nanocrystal was estimated by the peak energy to be 4-5 nm in diameter. A very broad photoluminescence (PL) peak centered at 2.4 eV was observed when excited at 3.8 eV. The PL spectra excited at lower photon energy indicates that the PL peak is composed of 2.5, 2.3 and 1.7-1.8 eV peaks. When we excited the specimen below 2.7 eV, PL spectra of colloid solution and cast film of PEG-TC CdS was very different. The difference in the recombination processes between PEG-TC US ensemble and isolated PEG-TC US is discussed in the present paper. (C) 2003 Elsevier Science B.V. All rights reserved.