A quantitative, multi-responsive sensing method for transition metal ions was developed by utilizing anionic hydrogels. The hydrogels, composed of acrylamido-methylpropane sulfonic acid, co-polymerized with polyacrylic acid, respond to the formation of a transition metal hexacyanoferrate complex, such as Prussian blue, with altered conductivity, swelling, vibrational, and colorimetric characteristics with sub-ppm detection limits. The eleven transition metal ions investigated in this paper are Cu2+, Fe2+, Mn2+, Ni2+, Pb2+, Co2+, Sn2+, Cd2+, Zn2+, Mo5+, and Ag+; the hydrogels demonstrated opposite quantitative trends depending on the type of ion present. These trends followed Hofmeister series principles involving strength of headgroup-ion interactions, as well as the expected trends regarding alteration of water viscosity. The adherence to these principles was confirmed by Raman spectroscopy and investigation of the effect of altering the supporting electrolyte. These robust, flexible hydrogel sensors, which can be optimized by alteration of the headgroups present, demonstrate suitability for field-ready identification and quantification of transition metal ions.

Multi-responsive hydrogel sensors for transition metal ions via Hofmeister series principles

255th National Meeting (2018)

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