Anion sensing with cobalt corrinoid grafted quartz crystal microbalances

Corrin macrocycles are well known for their interesting and multifaceted coordination chemistry at the axial positions of the cobalt center. In this work, the use of such cobalt corrinoids as sensitive elements for sorption based chemical sensors like the quartz crystal microbalance (QCM) is described for the first time. This approach of fast and reversible ion detection extends the versatility and applicability of this class of metal-containing ionophores and colorimetric indicators. QCMs were grafted with aquacyano and dicyano cobalt corrinoids and assessed in their sensing characteristics during exposure to cyanide, thiocyanate, and other ionic species as well as selected organic compounds. The liquid sensing characteristics of the corronoids were found to be excellent. Sensors reach equilibrium in <3 s from the stable baseline after analyte exposure and the responses are fully reversible. Sensors of high sensitivity and selectivity for cyanide have been obtained with detection limits at 1 μM. At the same time, the sensitivities to common organic compounds are negligible. The results demonstrate that corrin grafted QCMs exhibit enormous potential as chemical sensors for the detection of anions, especially cyanide, in aqueous samples.