Multi-emitting properties of hybrid Langmuir–Blodgett films of amphiphilic iridium complexes and the exfoliated nanosheets of saponite clay

Abstract

Mono- and multi-layered films comprised of amphiphilic cationic iridium(III) complexes hybridized with the exfoliated nanosheets of synthetic saponite were prepared by the modified Langmuir–Blodgett method. Three iridium(III) complexes with different emission maxima (λ_max) were used as incorporated complexes: [Ir(dfppy)₂(dc9bpy)]⁺ (λ_max = 500 nm) (dfppyH = 2-(4′,6′-difluorophenyl)pyridine; dc9bpy = 4,4′-dinonyl-2,2′-bipyridine) [Ir(ppy)₂(dc9bpy)]⁺ (λ_max = 550 nm) (ppyH = 2-phenylpyridine) and [Ir(piq)₂(dc9bpy)]⁺ (λ_max = 590 nm) (piqH = 1-phenylisoquinoline) for blue, yellow and red emissions, respectively. Six triple-layered films with different layer sequences were fabricated by layer-by-layer deposition onto quartz substrates. Stationary emission spectra were recorded on the prepared films under vacuum and at various oxygen pressures. Notably the change in the spectral shape at surrounding oxygen pressure depended remarkably on the layer sequence. Quenching by oxygen molecules was analyzed by applying a two-site model to the Stern–Volmer plots. The present nanometer-thick films were regarded as a benchmark for an optical device emitting different visible lights in response to oxygen pressure.