125Materials for Nanosensors
to a surrounding array of molecules or anions [ligands, complexing agents])
with millisecond lifetimes. Fluorescence from single QDs has been observed
longer than from most other individual uorophores enabling to collect a
larger number of photons. Further, the synthetic protocol of QDs with dif-
ferent emission wavelengths is simpler and reaction time is the dot size-
controlling variable.
What are the disadvantages of quantum dots? Disadvantages of QDs include
the toxicity of the component heavy metals Cd or Pb used in II–VI semicon-
ductor dots, the most widely used QDs. Furthermore, the inorganic nature
of QDs renders them inherently insoluble in aqueous media. Also, the larger
hydrodynamic radii (the effe