Enhanced photocycloreversion reaction of diarylethene polymers attached to gold nanoparticles in the solid state

The photochromic reactivity of diarylethene polymers attached to gold nanoparticle in the solid state was investigated. The photochromic diarylethene polymers around the gold nanoparticle exhibited reversible photochromism upon alternating irradiation with ultraviolet (UV) and visible light even in the solid state. The local surface plasmon resonance (LSPR) band of the gold nanoparticle in the solid state was red-shifted in comparison with that dispersed in a solution because of the closer interparticle distance. Alternating irradiation with UV and visible light led to the photoreversible changes in the LSPR band because the refractive index of the diarylethene polymer shell changes along with the photochromic reaction of the diarylethene polymers. However, the behavior of the spectral changes significantly depended on the irradiation wavelength. It reveals that the photocycloreversion reaction heterogeneously took place in the shell of the diarylethene polymers upon irradiation at longer wavelength to be enhanced in proximity to the gold nanoparticles. The promotion of the photoreaction is due to the plasmonic enhancement effect both in the vicinity and in the gap of the gold nanoparticles.