Figure 3: Upconversion emission properties.
a) Comparison of UC spectra from core to core-shell nanoparticles show significant enhancement in intensity at 150 W/cm2, despite 2x more concentrated cores. Inset: nanoparticles suspended in cyclohexane under 980 nm illumination at ~10 W/cm2. b) Red to green emission ratio, , of core-shell samples over two magnitudes of irradiance values. In the inset, the Gd- and Lu-shelled samples appear redder than the Y-shelled sample at low powers. c) Quantum yield of samples over two magnitudes of irradiance values. Here, guides-to-the-eye and average particle sizes (diameters) are added to highlight trends. d) Lifetime curves showing the rise and total (τtot = rise + decay) time of red emission (654 nm) under 980 nm excitation.