Ultraviolet Photoluminescence of Carbon Nanospheres and its Surface Plasmon-Induced Enhancement

Ultraviolet (UV) light can be used in versatile applications ranging from photo-electronic devices to biomedical imaging. In the development of new UV light sources, in this study, stable UV emission at approximate to 350 nm is unprecedentedly obtained from carbon nanospheres (CNSs). The origin of the UV fluorescence is comprehensively investigated via various characterization methods, including Raman and Fourier transform infrared analyses, with comparison to the visible emission of carbon nanodots. Based on the density functional calculations, the UV fluorescence is assigned to the carbon nanostructures bonded to bridging O atoms and dangling -OH groups. Moreover, a twofold enhancement in the UV emission is acquired for Au-carbon core-shell nanospheres (Au-CNSs). This remarkable modification of the UV emission is primarily ascribed to charge transfer between the CNSs and the Au surface.