Tryptophan-Derived Polynorbornene–Multiwalled Carbon Nanotube Fluorescent Chemosensors for Cu²⁺ Detection and Thiol Discrimination

Polymer-carbon nanotube hybrids were synthesized via the ring-opening metathesis polymerization (ROMP) of a tryptophan-derived polynorbornene and norbornene-functionalized multiwalled carbon nanotubes (MWCNTs) using a Grubbs M31 catalyst. Successful copolymerization was confirmed by proton nuclear magnetic resonance, transmission electron microscopy, thermogravimetric analysis, and Raman spectroscopy, ensuring the nanostructural integrity. The hybrids functioned as fluorescent chemosensors, exhibiting strong quenching in response to Cu2+, Fe3+, Pb2+, and Zn2+, with MWCNTs enhancing the metal ion adsorption. They achieved detection limits of 16.23–47.40 μM for Cu2+ and Fe3+ and displayed selective fluorescence recovery with cysteine over homocysteine and glutathione. Detection in human serum validated their efficacy in complex biological media, with cytotoxicity and cellular uptake studies confirming biocompatibility, suggesting the potential for further in vivo application with safety. These results demonstrate the potential of ROMP-based polymer–nanotube hybrids for biomedical and environmental sensing applications.