Nanoliter-scale, regenerable ion sensor: sensing with a surface functionalized microstructured optical fibre

The first nanoliter-scale regenerable ion sensor based on a microstructured optical fibre (MOF) is reported. The air holes of the MOF are functionalized with a monoazacrown bearing spiropyran to give a switchable sensor that detects lithium ions down to 100 nM in nanoliter-scale volumes. Ion binding is turned on and off on upon irradiation with light, with the sensor being unaffected by multiple rounds of photoswitching. Unbound ions are flushed from the fibre in the ‘off’ state to allow the sensor to be reused. The integration of an ionophore into the sensor paves the way for the development of highly specific light-based sensing platforms that are readily adaptable to sense a particular ion simply by altering the ionophore design.

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