Singlet oxygen production by fluorescence resonance energy transfer (FRET) from green and orange CdSe/ZnS QDs to protoporphyrin IX (PpIX)

► CdSe/ZnS QDs were coated by using mercaptopropionic acid or polyethylenimine. When activated by LEDs, QDs transferred their energy to protoporphyrin IX (PpIX). ► Electron exchange between excited PpIX and triplet oxygen produced singlet oxygen. ► The singlet oxygen (1O2) produced could be used in the treatment of Escherichia coli. The QDs and PpIX were also entrapped into the sol-gel matrix GA to produce the 1O2.