Nanometric Film Functionalization for Surface Modification

New techniques have been developed for functionalizing surfaces with nanometer-thick organic films, useful for attaching bio-molecules in sensors and biosensors. This method involves a novel surface functionalization technique that anchors alkyl chains at low potentials. It utilizes a process where aryl radicals from dazonium salts, which typically react with surfaces, are instead redirected to create reactive aliphatic radicals.

This is achieved using the 2,6-dimethylphenyl radical, which does not bind to surfaces like other aryl radicals but instead helps in generating alkyl radicals that attach to glassy carbon surfaces, forming stable nanometer-thick alkyl films. This process is more energy-efficient than direct reduction, with a 2eV advantage.

The method also allows for creating complex, mixed bifunctional nanometer films by reacting an aromatic radical with RI or RBr on the surface. These films can trap other molecules, contributing to the field of nanomedicine, especially in targeted drug delivery using polymeric nanoparticles.

Key findings include the following:

• Transfer of iodine atoms from alkyl iodides to sterically hindered aryl radicals, bypassing surface competition;
• Durability of grafted alkyl chains, resisting harsh conditions like ultrasonication, boiling solvents, and extreme voltage changes;
• Capability to form mono- or multilayer films ranging from 1 to 5 nm;
• Comprehensive characterization using techniques like IR, XPS, electrochemistry, ellipsometry, and water contact angle measurements.

Additionally, this method can be adapted to graft nanomaterials onto non-conductive surfaces using a reducing agent in solution instead of an electrode.