Engineering upconversion using cavity plasmonic mode of Ag hemishell capped on NaLuF4:Yb,Er@SiO2 nanosphere

Intensity enhancement and color modulation of upconversion (UC) are two challenges for its viable applications. A systematic theoretical research about the effect of cavity plasmonic mode on UC of NaLuF4:Yb,Er@SiO2 core-shell structured nanosphere capped with Ag hemishell suggests that this plasmonic structure can engineer UC. Cavity plasmonic mode can selectively improve green and red UC luminescence (UCL) using Purcell effect, via tuning the diameter of core-shell nanosphere. A position-weight emission enhancements over 21 random points are 9.3 times for green and 10.3 for red UCLs under their respective spectral matched conditions, with an assumption of the original quantum efficiency of 5%, with the intensity ratios of green UCL to red (G/R) of 3.3 and 0.87, respectively, namely with improved color purity. Taking excitation into account, the UCL is only enhanced when the cavity mode coincides with the red emission band, with red and green UCLs being enhanced by 76% and 47%. However, both intensity enhancement and color modulation deteriorate with increase of the original quantum efficiency. This insight means that using Purcell effect of Ag hemishell may enhance the intensity and achieve purer green of UCL.