Controlled aryl quantum well formation on carbon nanotubes via peroxide-mediated reduction of aryl diazonium salts

Quantum well defect-modified single walled carbon nanotubes are environmentally sensitive nanomaterials with wide-ranging applications in biosensing, imaging, light harvesting, quantum computing, energy storage and catalysis. The most common method for covalent functionalization of nanotubes involves reactions with aryl diazonium salts to generate sp3 aryl defect sites. These reactions typically employ harsh conditions which result in poor control and scalability, and incompatibility with biomaterials. We describe herein a rapid aryl diazonium functionalization reaction wherein hydrogen peroxide functions as a reducing agent. The reaction conditions are mild, enabling the quantum well defect functionalization of nanotubes in aqueous solutions at room temperature, with nitrogen and oxygen gas as the primary by-products. This reaction is compatible with both DNA and synthetic polymer-wrapped nanotubes with no apparent disruption to the wrapping agent. As a result, this chemistry is highly complementary to polymer-based nanotube purification reactions such as aqueous two-phase extraction. The reaction is also compatible with unwrapped SWCNTs and in situ generation of diazonium salts from anilines, enabling substantial scalability and versatility with a greater variety of functional groups. The reaction can be easily monitored in real-time via fluorescence analysis and so can be readily controlled and terminated upon reaching the desired degree of functionalization. Overall, this reaction greatly simplifies the production of covalently functionalized carbon nanotubes, expanding their potential for industrial and biomedical applications.