Automated Plasmon-Selective Laser Writing in Mesoporous Thin Films Through Decoupling of the Initiator Absorption and Plasmon Wavelength.

Enhancing nanopore functionalization precision is relevant to advance future-relevant technologies such as molecular sensing, separation, catalysis, and energy conversion. An interesting approach for high-resolution polymerization is to use nanoscale light sources like surface plasmons. To design polymer functionalization in artificial mesopores, Au nanospheres (AuNSs) are implemented into mesoporous silica thin films, harnessing their plasmon for visible-light near-field-induced polymerization initiation. AuNSs are incorporated at defined layer height, pursuing local placement of polymer along the pore depth. Using photoiniferter as photoreactive initiator for reversible-addition-fragmentation chain-transfer (RAFT) polymerization requires demarcated photoreactivity of both moieties, the AuNSs and the photoiniferter. A high reactivity of AuNSs concomitant to the photostability of the photoiniferter is observed. The wavelength-dependence of the polymerization initiation is investigated, focusing on wavelength separation of iniferter absorption and plasmon generation. Wavelength-dependent cooperativity effects between AuNSs, the photoiniferter, and the photocatalyst are explored to understand potential radiative and nonradiative polymerization induction mechanisms of the plasmon-induced polymerization. Ultimately, plasmon-selective polymerization is integrated into direct laser writing, affording precise lateral polymer functionalization of mesoporous membranes. Aiming at further miniaturized polymer functionalization, a strategy to attain spatial control over polymer placement in an automated process, paving the way to directed ionic movement through mesoporous membranes, is provided.