Surface Modification Effects on Single-Walled Carbon Nanotubes for Multimodal Optical Applications

Optical nanoscale technologies often implement covalent or noncovalent strategies for the modification of nanoparticles, whereby both functionalizations are leveraged for multimodal applications but can affect the intrinsic fluorescence of nanoparticles. Specifically, single-walled carbon nanotubes (SWCNTs) can enable real-time imaging and cellular delivery; however, the introduction of covalent SWCNT sidewall functionalizations often attenuates SWCNT fluorescence. Herein, we leverage recent advances in SWCNT covalent functionalization chemistries that preserve the SWCNTs pristine graphitic lattice and intrinsic fluorescence and demonstrate that such covalently functionalized SWCNTs maintain fluorescence-based molecular recognition of neurotransmitter and protein analytes. We show that the covalently modified SWCNT nanosensor fluorescence response towards its analyte is preserved for certain nanosensors, presumably dependent on the steric hindrance introduced by the covalent functionalization that hinders noncovalent interactions with the SWCNT surface. We further demonstrate that these SWCNT nanosensors can be functionalized via their covalent handles to self-assemble on passivated microscopy slides, and discuss future use of these dual-functionalized SWCNT materials for multiplexed applications.