available polycyclic aromatic hydrocarbon (PAH) precursors with
strong acid and followed by hydrothermal reduction with hydrazine hydrate is
reported. Transmission electron microscopy (TEM) and atomic force microscopy
(AFM) characterizations indicate that the size and height of GQDs are
in the range of 5–10 nm and 0.5–2.5 nm, respectively. PAH, which has more
benzene rings, generally forms GQDs with relatively larger size. The GQDs
show high water solubility, tunable photoluminescence, low cytotoxicity, and
good optical stability, which makes them promising fl uorescent probes for
cellular imaging. In addition, the fl uorescence of GQDs shows a sensitive and
selective quenching effect to Fe 3+ with a detection limit of 5 × 10 ?9 M .
By combination with the Fe 2+ /Fe 3+ redox couple, the PL GQDs are able to
detect oxidant, using H 2 O 2 as an example. This study opens up new opportunities
to make full use of GQDs because of their facile availability,
cost-effective productivity, and robust functionality.