A polymeric precursor strategy was
developed toward precise synthesis
of uniform and size-tunable hairy fluorescent carbon dots (C-dots,
CDs). The strategy was achieved by (i) the synthesis of core–shell
6-arm starlike block copolymers of PGMA-b-PMMA (poly(glucosyl
methyacrylate), PGMA; poly(methyl methacrylate), PMMA), serving as
a precursor using atom transfer radical polymerization (ATRP) and
(ii) selective carbonization of the inner PGMA chains to generate
hairy C-dots with PMMA blocks attaching on the surfaces. The resultant
C-dots with tunable sizes showed blue to green fluorescence depending
on the excitation, size, and concentration. The large size of the
C-dots led to a significant red shift of fluorescence emission, which
was attributed to enhanced intra-C-dot Förster resonance energy
transfer (FRET) between the emitter homologues in a single C-dot.
In addition, the FRET effect between C-dots was further confirmed
by the aggregation-caused quenching characteristics and red shift
of emission at high concentrations. Interestingly, different from
the traditional fluorophores with photobleaching characteristics,
C-dots showed recoverable photoabsorption capacity and enhanced fluorescence
after the long-time exposure to UV light.