(Invited) Melanin-Inspired Functionalization of Single-Walled Carbon Nanotubes for Optical Detection of Metals

Abstract

The accumulation of metal ions in organisms and the presence of heavy metals in water cause adverse effects on ecosystems and result in numerous human health issues such as cancer and neurogenerative diseases. Therefore, the development of novel platforms for metal-scavenging and rapid metal detection for in situ applications are of high importance. Here, this challenge is tackled by taking advantage of the metal chelation ability of a melanin-inspired material in combination with the near-infrared (NIR) fluorescence response of single-walled carbon nanotubes (SWCNTs) to surface binding. SWCNTs are functionalized by a melanin-like substance, obtained by enzymatic oxidative polymerization of a fluorenylmethyloxycarbonyl-tyrosine (FmocY) precursor. The resulting multicomponent system (SWCNT-FmocYOx) serves as a metal-ion scavenging platform that concurrently reports on metal binding with optical signal transduction. Upon binding of a library of mostly divalent transition metal-ions, the fluorescence emission of the functionalized SWCNTs is modulated, showing a concentration-dependent response with a limit of detection in the nanomolar range. Metal-binding and removal from water of up to 98% are further shown via inductively coupled plasma mass spectrometry. The SWCNT-FmocYOx hybrid system presents a novel platform with NIR optical signal for real-time feedback on metal-ion scavenging.