Carbon dots (CDs) are an emerging
class of nanomaterials with intriguing photophysical properties.
Recently, achieving room-temperature phosphorescence (RTP) for CDs have
attracted considerable attention for biomedical and information
applications. However, the CDs based RTP materials generally require the
use of polymeric and inorganic matrix to provide the rigid environments,
which remains a great challenge to obtain matrix-free CDs with RTP.
Herein, a novel supramolecular strategy based on strong interparticle
interactions has been developed to attain this objective, by covalent
decoration of ureido-pyrimidinone (UPy, a multiple hydrogen bonding
unit) on the surface of CDs. Structural characterizations validated the
core-shell structure of the as-prepared CDs (EDTA-CDs) and demonstrated
the successful attachment of UPy via post-modification (UPy-CDs). The
presence of UPy recognition units render the strong hydrogen bonding
between UPy-CDs, which stabilizes the triplet state via rigidifying
effect. As a result, UPy-CDs exhibit matrix-free efficient RTP
(λem = 534 nm) with high brightness and long lifetime
(33.6 ms) in the solid state. Owing to the dual-emission character, we
further explored the application potential of UPy-CDs in information
encryption and anti-counterfeiting. Overall, this work provides a new
and facile strategy for achieving matrix-free phosphorescent CDs with
elegant incorporation of supramolecular chemistry.
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