Metal-enhanced fluorescence singlet oxygen generation

Y. Zhang, K. Aslan, M. J. Previte, and C. D. Geddes. Metal-enhanced Singlet Oxygen Generation A Consequence of Plasmon Enhanced Triplet YifiXAs Journal of Fluorescence, 2007, 17, 345-349. 

Figure 10.2 Graphical representation of Metal-Enhanced Fluorescence (Top), Metal-Enhanced Phosphorescence (Middle), and for the generation of Singlet Oxygen (Bottom). F - Fluorophore, RB - Rose Bengal, P - Phosphorescence and MEP - Metal-Enhanced Phosphorescence, 302 — triplet ground state oxygen. 102 -singlet oxygen. Adopted from ref [25].

Enhanced fluorescence, or MEF, is a result of both a net system absorption and plasmon coupling and subsequently efficient emission, but to date, it has not been possible to quantify the relative contributions of enhanced emission and net increase in the system absorption to the MEF phenomena.(23) Due to the increase in the population of the singlet excited state or net system absorption, the very presence of MEP has also suggests an increase in the population of the triplet state.(23) The presence of Metal-Enhanced Fluorescence, Phosphorescence, Metal-Enhanced singlet oxygen and superoxide anion radical generation in the same system is an effect of the enhanced absorption and emission effects of the fluorophores near-to silver, although these processes are effectively competitive and ultimately provide a route for deactivation of electronic excited states. 

Zhang, Y. X., Aslan, K., Previte, M. J. R., and Geddes, C. D. (2007). Metal-enhanced singlet oxygen generation A consequence of plasmon enhanced triplet yields Journal of Fluorescence 17 345-349. 

---