Room-Temperature Phosphorescence in Carbon Dots

Room-temperature phosphorescence (RTP) in carbon dots has emerged as a vibrant subfield of luminescent nanomaterials, distinguished by its long-lived afterglow, high signal-to-noise ratio and purely organic composition. Carbon dots—quasi-spherical nanoparticles typically smaller than 10 nm—combine facile, often green, synthesis routes with tunable surface chemistries that enable intersystem crossing into triplet excited states. Achieving RTP at ambient conditions requires suppression of non-radiative decay pathways through rigidification of emissive centres. Strategies include embedding dots in hydrogen-bonded networks, inorganic crystalline matrices or polymer hosts, as well as designing multi-confinement architectures and photoactivated intermediates. These approaches stabilise triplet excitons, extend phosphorescence lifetimes from milliseconds to hours and yield high phosphorescence quantum yields. The bright, persistent emission under ambient conditions has unlocked a range of applications—from bioimaging and in vivo surgical guidance to anticounterfeiting, information encryption, chemical sensing and optoelectronic devices—whilst leveraging low toxicity, cost-effectiveness and environmental sustainability.

Research from Nature Portfolio

Recent studies have introduced a photooxidation strategy to produce near-infrared afterglow carbon dots with ultralong lifetimes up to 5.9 hours. This method generates a dioxetane intermediate that slowly decomposes to release stored energy, activated by steric hindrance effects in aqueous suspension. The persistent emission at depths of 20 mm in biological tissue demonstrates potential for high-contrast surgical guidance applications. Earlier work established a multi-confined structure in which carbon dots are rigidly fixed by covalent bonds, cross-linked polymer networks and three-dimensional spatial restriction. Such hierarchical confinement yielded phosphorescence lifetimes of 5.72 s and quantum efficiencies exceeding 26%, even under harsh chemical conditions. Foundational research also revealed that water-mediated hydrogen-bonded networks between carbon dots and cyanuric acid can both rigidify carbonyl groups and extend system rigidity, resulting in visible phosphorescence lifetimes near 0.7 s in aqueous media—paving the way for ion-sensing and bioimaging in liquid environments.

Room-Temperature Phosphorescence in Carbon Dots publication trend

The graph below shows the total number of articles in room-temperature phosphorescence in carbon dots across all publications each year (not limited to Nature Index journals).

Technical terms

Carbon Dots: Nanometre-scale carbonaceous particles exhibiting size-dependent fluorescence and phosphorescence due to quantum confinement and surface-state effects.

Room-Temperature Phosphorescence (RTP): Emission of light from a triplet excited state under ambient conditions, characterised by lifetimes ranging from milliseconds to hours.

Intersystem Crossing: Non-radiative transition between singlet and triplet excited states, enabling population of phosphorescent states.

Triplet Excited State: An electronic state with two unpaired electrons of parallel spin, responsible for phosphorescent emission.

Quantum Yield: The ratio of photons emitted to photons absorbed, indicating luminescence efficiency.

References

1. High‐yield upcycling of feather wastes into solid‐state ultra‐long phosphorescence carbon dots for advanced anticounterfeiting and information encryption. Exploration (2024).
2. Photooxidation triggered ultralong afterglow in carbon nanodots. Nature Communications (2024).
3. Multiemitting Ultralong Phosphorescent Carbonized Polymer Dots via Synergistic Enhancement Structure Design. Advanced Science (2024).
4. Induction of long-lived room temperature phosphorescence of carbon dots by water in hydrogen-bonded matrices. Nature Communications (2018).
5. Ultralong lifetime and efficient room temperature phosphorescent carbon dots through multi-confinement structure design. Nature Communications (2020).
6. Controlling the fluorescence and room-temperature phosphorescence behaviour of carbon nanodots with inorganic crystalline nanocomposites. Nature Communications (2019).
7. Enabling robust and hour-level organic long persistent luminescence from carbon dots by covalent fixation. Light: Science & Applications (2022).