Preparation and photodynamic antibacterial/anticancer effects of ultralong-lifetime room-temperature phosphorescent N-doped carbon dots

Room-temperature phosphorescent (RTP) N-doped carbon-dots (CNDs) featuring eco-friendliness, low cost and high biocompatibility, are ideal photodynamic antibacterial and anticancer nanomaterials. However, the existing CNDs are limited by low singlet oxygen (¹O₂) quantum yield, which has become a bottleneck in the development of CNDs. One basic reason is the short T₁-state exciton lifetime of CNDs. Herein, triethylenetetramine hexaacetic acid was used to synthesize CNDs via a one-step hydrothermal method. CNDs are characterized with low toxicity, high biocompatibility and ultralong-lifetime RTP (URTP). In addition to the URTP (average lifetime 414 ms) under solid conditions, CNDs even had URTP (average lifetime 320 ms) in a water environment. The ultralong T₁ exciton lifetime largely extends the collision time between T₁ state excitons and O₂ and prolongs the energy transfer time, not only improving the quantum yield (0.63) of singlet oxygen (¹O₂) in solution, but also facilitating the photodynamic antibacterial and anticancer effects.

The URTP CNDs largely extends the collision time between T₁ state exciton and O₂, which improve quantum yield of singlet oxygen (¹O₂) in solutions, facilitating the photodynamic antibacterial and anticancer effects.