Functionalized Amphiphilic Block Copolymers and Complex Emulsions for Selective Sensing of Dissolved Metals at Liquid-Liquid Interfaces

Increasing contamination in potable water supplies necessitates the development of sensing methods that provide the speed and selectivity necessary for safety. One promising method relies on recognition and detection at the liquid-liquid interface of dynamic complex emulsions. These all-liquid materials transduce changes in interfacial tensions into optical signals via the coupling of their chemical, physical, and optical properties. Thus, to introduce selectivity, it is necessary to modify the liquid-liquid interface with an interfacially stable and selective recognition unit. To this end, we report the synthesis and characterization of amphiphilic block copolymers modified with metal chelators to selectively measure the concentrations of dissolved metal ions. We find that significant reduction in interfacial tensions arises upon quantitative addition of metal ions with high affinity toward functionalized chelators. Furthermore, measurements from UV-vis spectroscopy reveal that complexation of the block copolymers with metal ions leads to an increase in surface excess and surfactant effectiveness. We also demonstrate selective detection of iron(III) cations (Fe3+) on the mu M levels even through interference from other mono-, di-, or trivalent cations in complex matrices of synthetic groundwater. Our results provide a unique platform that couples selective recognition and modulation of interfacial behaviors and demonstrates a step forward in the development of the multiplexed sensing device needed to deconvolute the complicated array of contaminants that comprise real-world environmental samples.

Automated summary

The development of sensing methods that provide speed and selectivity is necessary to address the increasing contamination in potable water supplies. One promising method involves recognition and detection at the liquid-liquid interface. This method transduces changes in interfacial tensions into optical signals, providing selectivity. In this study, amphiphilic block copolymers modified with metal chelators were synthesized and characterized for the selective measurement of dissolved metal ions. Significant reduction in interfacial tensions and increased surface excess and surfactant effectiveness were observed when the block copolymers were complexed with metal ions. The researchers also demonstrated selective detection of iron(III) cations in complex matrices of synthetic groundwater, even in the presence of interference from other cations.