Plasmon-Induced Photoreaction of <i>o</i>‑Nitrobenzyl-Based Ligands under 550 nm Light

We have studied the plasmon-driven photoreaction of a dual thiol-anchored <i>o</i>-nitrobenzyl-based photouncaging ligand on silver nanoparticles. Previous results have shown that this compound strongly anchors to gold surfaces, and a 1 J/cm² dose of UV light induces the intended photoreaction, uncaging an amine on the surface. This allows for photopatterning and the selective adhesion of gold nanospheres (AuNSs) to a surface via electrostatic attraction between the positively charged amines and negatively charged AuNSs. Here, we report that when the ligand is adsorbed on a silver nanospheroid film (AgNS), an additional photoreaction induced by green light inhibits AuNSs adhesion in the UV exposed film. Our findings suggest that this is a result of the neutralization of the amine group’s ability to become charged, as opposed to the removal of the ligand from the surface of the silver nanospheroids. We hypothesize that this neutralization may be due to a form of hot-hole-induced photocatalysis, resulting in an NN double bond between two neighboring ligands. This reaction has been documented in similarly amine-terminated moieties. This neutralization allows for a more fine-tuned, plasmonically based control of the ligand’s photoreaction, as the green light exposure only affects the ligand if it has previously been cleaved by UV light, and makes it possible to perform reverse photopatterning on the surface