Enhanced yellow-green photoluminescence at the interface of ZnO nanoparticles and multiple catechol-functionalized polycyclosiloxane nanofilms driven by selective UV light irradiation

We report a surface engineering strategy for utilizing surface defects of a wide bandgap semiconductor metal oxide ZnO nanoparticles (ZnO NPs, average diameter 4.9 ± 1.2 nm) array assembled on catechol-functionalized polycyclosiloxane (CFPS) nanofilms (9.8 ± 1.0 nm film thickness). Yellow-green photoluminescence was observed and the PL intensity increased enormously under selective UV laser light irradiation at room temperature; ZnO NPs were excited selectively at 325 nm, and no absorption at that wavelength occurred for catechol units. Two layer structures were prepared by dipping method: bilayer structure CFPS/ZnO NPs (BA), and sandwich structure CFPS/ZnO NPs/CFPS (SA). The enhancement was observed for both structures (2.5 ± 0.4 times (BA) and 8.1 ± 0.9 times (SA)), while no enhancement was observed ZnO NP arrays alone. A plausible PL enhancement mechanism was discussed by using XPS data in terms of hydration-based oxygen vacancy formation and charge trapping at the CFPS/ZnO NPs interfaces, which are responsible for the yellow-green PL luminescence enhancement.