Light Scattering Induced Giant Red-Shift in Photoluminescence from CdTe Quantum Dots Encapsulated in Polyacrylamide Gel Nanospheres

The photoluminescence emission from CdTe quantum dots embedded in hydrogel nanospheres based on poly(N-isopropylacrylamide) (PNIPAM) polymer is observed to be modified by the random light scattering within the colloidal medium. Photoluminescence emission from CdTe quantum dots of various size has been observed making the gel fluorescent. The optical properties of the quantum dots entrapped within the gel microspheres can be modified due to change in refractive index, volume density of the surrounding hydrogel medium. A red-shift of similar to 100 nm has been observed from quantum dots emitting in the green wavelength region as the cell length is increased. This shift is due to secondary scattering and energy transfer induced by the larger scattering cross-section within the medium which results in a re-excitation of larger sized quantum dots. (C) 2009 The Japan Society of Applied Physics