CONTROL OF LIGHT SCATTERING INDUCED SHIFT IN PHOTOLUMINESCENCE FROM CDTE QUANTUM DOTS ENCAPSULATED IN POLY‐ACRYLAMIDE GEL NANOSPHERES

Abstract

The transmission of light through a colloidal solution of hydrogel nanospheres based on poly(N‐isopropylacrylamide) (PNIPAM) polymer depends critically on the refractive index and random light scattering of the medium. These physical properties of the colloidal medium modify the photoluminescence emission from CdTe quantum dots embedded in PNIPAM nanospheres. The optical properties of the quantum dots entrapped within the gel microspheres can be modified by changing the polymer concentration due to change in refractive index or volume density of the surrounding hydrogel medium. A red‐shift of 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 resonant energy transfer induced by the larger scattering cross‐section within the medium, which results in a re‐excitation of larger‐sized quantum dots.

Keywords:

• Colloidal quantum dots
• Hydrogel
• Light scattering
• Photoluminescence
• Polyacrylamide
• Red‐shift

ACKNOWLEDGMENTS

The authors acknowledge the support from the National Science Foundation International Research Education Program and Doctoral Dissertation Enhancement Program. Dr. S. Ghosh's assistance for the Scanning Electron Microscopy measurements is gratefully acknowledged. The support from the UNT‐Global and Hispanic Research program is also acknowledged.