In this paper, we prepared fluorescence-tunable water-soluble CdS quantum dots (QDs) with hex-
ametaphosphate
as
stabilizers
by
a
simple
route.
The
prepared
CdS
QDs
were
utilized
to
detect
calcium ion (Ca2+) based on an obvious fluorescence enhancement of CdS QDs induced by Ca2+. The
results
demonstrated
there
was
an
excellent
linear
relationship
between
the
fluorescence
intensity
of
hexametaphosphate-capped
CdS
QDs
and
Ca2+ concentration
in
the
range
from
10
mol/L
to
400
mol/L
and the detection limit for Ca2+ was 4 mol/L. Furthermore, fluoride ions (F−) can react with Ca2+ to gener-
ate
the
insoluble
calcium
fluoride
that
would
inhibit
the
Ca2+-induced
fluorescence
enhancement
of
CdS
QDs. Therefore, the designed Ca2+-induced fluorescence enhancement system was also able to effectively
detect fluoride.