(688c) Fluorescent Single-Walled Carbon Nanotubes for Dilute Divalent Metal Cation Sensing

Colloidal single-walled carbon nanotubes (SWCNTs) offer a promising platform for the nanoscale engineering of molecular recognition. Optical sensors have been recently designed through the modification of non-covalent corona phases of SWCNTs. Specifically, DNA are of great interest due to the breadth of the design space and our ability to control these molecules with sequence specificity at scale. Utilizing these constructs for metal ion sensing is a natural extension of this technology due to DNA’s well-known coordination chemistry. Additionally, understanding metal ion interactions of these constructs allows for improved sensor design for use in complex aqueous environments. In this work, we study the interactions between dilute divalent metal cations and DNA-SWCNT under the most controlled experimental conditions for SWCNT optical sensor studies to date. We found that best practices for the study of colloidal SWCNT analyte responses involve mitigating the effects of ionic strength, dilution kinetics, laser power and analyte response kinetics. We also discover that DNA-SWCNTs offer two unique sensing states at pH 6 and 8. The combined set of sensors in this work allows for the differentiation of Hg²⁺, Pb²⁺, Cr²⁺ and Mn²⁺. Finally, we implemented Hg²⁺ sensing in the context of portable detection within fish tissue extract, demonstrating nanomolar level detection.