Ultraviolet phosphorescent carbon nanodots

Abstract

Phosphorescent carbon nanodots (CNDs) have generated enormous interest recently, and the CND phosphorescence is usually located in the visible region, while ultraviolet (UV) phosphorescent CNDs have not been reported thus far. Herein, the UV phosphorescence of CNDs was achieved by decreasing conjugation size and in-situ spatial confinement in a NaCNO crystal. The electron transition from the px to the sp2 orbit of the N atoms within the CNDs can generate one-unit orbital angular momentum, providing a driving force for the triplet excitons population of the CNDs. The confinement caused by the NaCNO crystal reduces the energy dissipation paths of the generated triplet excitons. By further tailoring the size of the CNDs, the phosphorescence wavelength can be tuned to 348 nm, and the room temperature lifetime of the CNDs can reach 15.8 ms. As a demonstration, the UV phosphorescent CNDs were used for inactivating gram-negative and gram-positive bacteria through the emission of their high-energy photons over a long duration, and the resulting antibacterial efficiency reached over 99.9%. This work provides a rational design strategy for UV phosphorescent CNDs and demonstrates their novel antibacterial applications.

An Overview on Carbon Quantum Dots Optical and Chemical Features

“…Furthermore, the complex network of hydrogen bonds contributed to the system rigidity, decreasing the nonradiative relaxation. Phosphorescence was also observed in xGQDs: Song et al [ 116 ] exploited the UV phosphorescence of CQNDs by reducing the graphitic domains or reducing the mobility of CD domains by adding sodium isocyanate crystals. The authors proved that the electron transition from the p x to the sp 2 orbital of the nitrogen generated an orbital angular momentum able to populate the triplet state.…”

Shallow Traps in Carbon Nitride Quantum Dots to Achieve 6.47 s Ultralong Lifetime and Wavelength‐Tunable Room Temperature Phosphorescence

“…[ 9–11 ] It is extremely difficult to obtain ultralong lifetime RTP CDs due to the weak spin–orbit coupling constants, the high vulnerability of the excited triplet state toward solvent and oxygen, and other nonradiative transition processes. [ 12–14 ]…”

“…[9][10][11] It is extremely difficult to obtain ultralong lifetime RTP CDs due to the weak spin-orbit coupling constants, the high vulnerability of the excited triplet state toward solvent and oxygen, and other nonradiative transition processes. [12][13][14] Most CDs are embedded in a rigid matrix to realize RTP emission. For example, Zhao et al encapsulated CDs in polyvinyl alcohol polymer matrix to achieve a phosphorescence lifetime of 380 ms. [15] Yu's group confined CDs in situ in the zeolite matrix during the solvothermal crystallization process to develop thermally activated delayed fluorescence (TADF) materials with a 350 ms lifetime.…”

Photoactivated organic phosphorescence by stereo-hindrance engineering for mimicking synaptic plasticity

“…Ultralong organic phosphorescence (UOP) is a unique persistent luminescent behavior of organic materials. It lasts for a period of time after the stoppage of excitation, receiving considerable attention in optoelectronics and bioelectronics recently 1 – 3 . For a long time, researches related to phosphorescence are mainly based on metal-containing complexes 4 , 5 .…”