Paper
Journal of Materials Chemistry B
fabricated easily by aggregation of TPECOOH molecules dis-
persed in a THF–water mixture. They showed good mono-
dispersity, significant aggregation-induced emission properties
in aqueous solution, and were able to enter cells because of
the good affinity of the carboxyl group to the cell membrane.
Our studies show that the TPECOOH dots showed red emis-
sion, good two-photon imaging ability, low toxicity, good
photostability, large Stokes shift, and biocompatible properties.
Furthermore, they performed very well in direct long-term cell
imaging. The AIE dots may have great potential in direct long-
Fig. 6 Two-photon confocal laser scanning microscopy images (excited term cell imaging.
at 880 nm). (a) Scale bar = 50 mm. (b) Magnification of (a), and scale bar =
2
5 mm.
Acknowledgements
This research was supported by 973 Projects (2012CB933803,
still be observed after 12 days, which indicates that the
TPECOOH dots are appropriate for long-term tracing.
2014CB643605), the National Science Fund for Distinguished
Young Scholars (50925310), the National Science Foundation of
China (21374060, 51173103), and Excellent Academic Leaders
of Shanghai (11XD1403000).
For comparison, the cell imaging capability of compound 8
was also evaluated. However, the hydrophobic dots of com-
pound 8 cannot be used to label the cell even after being
cultured for 48 h. The hydrophobic nanoparticles were not
taken up into the cell, possibly because of the lack of aqueous
stability that results in precipitation and a low affinity to the
cell membrane (Fig. S11, ESI†). This comparison verified our
hypothesis that for cell imaging, the intrinsic balance between
hydrophobicity and hydrophilicity of the fluorescent molecule
plays a crucial rule in labeling and tracing cells, and the good
affinity of TPECOOH dots to cell membranes originates from
the hydrophilic carboxyl group.
Notes and references
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1
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3096 | J. Mater. Chem. B, 2015, 3, 3091--3097
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