In this paper, we report the covalent immobilisation of spiropyran on
silica microbeads of 5 μm diameter and subsequent evaluation of the
photoswitchable behaviour and light-modulated ion-binding properties of the
spiropyran modified silica microbeads towards a range of different metal ions.
The beads can be effectively switched using light emitting diodes between a
white spiropyran form (by irradiation with a white 430–760 nm light emitting
diode) and a pink merocyanine form (upon irradiation with a UV light 375 nm
emitting diodes) that undergoes, under exposure to certain metal ions (such as
Cu2+ and Zn2+, final concentration of 7.7 × 10–4 M in ethanol solution), a
further reversible spectral and colour change due to the formation of
merocyanine-metal ion complexes. Furthermore, the accumulated ions can
subsequently released from the beads on demand using light emitting diodes to
reform the inactive spiro form.
Keywords: photoreversible ion binding;