A dual detecting polymeric sensor: chromogenic naked eye detection of silver and ratiometric fluorescent detection of manganese

Polymer 1, a poly(olefin) with pendant Schiff base units is prepared by reacting poly(allylamine) and 2-hydroxynapthaldehyde in methanol. The optical properties of 1 are investigated in THF:H2O (9:1) solvent system buffered at pH 7.0 ± 0.1 using HEPES. When tested against a range of physiological and environmentally relevant cations 1 displays selectivity for Ag+ from changes in the UV–vis spectra with linearity established in the range of 10–60 μM. The addition of Ag+ to a solution of 1 also causes a colour change from colourless to dark yellow meaning Ag+ is also detectable by the naked eye. In contrast, selectivity is observed for Mn2+ from changes in the emission spectra again with good linearity observed in the range of 0–50 nM. This is the first reported polymeric sensor capable of detecting both Ag+ and Mn2+ using two different detection modes.