Blue and white light emission from electron irradiated polystyrene

Abstract

Promising blue and white luminescence were demonstrated from energetic electron irradiated polystyrene (PS) film which was spin coated on silicon substrate with 8µm thickness. The fluorescence properties were characterized by using photoluminescence spectroscopy. Interestingly, pristine PS did not show any visible PL emission, however, irradiated samples exhibited blue-white fluorescence emission when PS film was irradiated by electron beam at fluence from $1.7x10^{15}$ to $9.5x10^{16} cm^{-2}$ with 50 keV. The light emitting region can be patterned into any size and shape by controlling the irradiated region. In addition, by adopting PS nanostructure nanoscale light emitter can be easily made. The origins of fluorescence were analyzed with FTIR, UV/Vis and NMR spectroscopy which identify the changes in chemical structure of the irradiated PS film. The results of spectroscopy suggested that light emission of electron-irradiated PS originate from clusterization of multi ring $sp^2$ carbon cluster induced by chemical rearrangements and variation of $sp^2$ carbon cluster size caused shift of fluorescence color.