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Diarylethene molecules used as molecular switches are envisioned as components of molecular electronic devices These photochromic molecules exhibit high thermal stability resistance to fatigue and switching efficiency Nevertheless the switching of most diarylethenes DAEs is asymmetric their photocycloreversion reaction possessing a much lower quantum yield than that of their photocyclization reaction A strategy to solve that asymmetric switching issue was tested it consisted in connecting the diarylethene molecules to gold nanoparticles AuNPs Indeed gold nanoparticles exhibit both a localized surface plasmon resonance LSPR very useful for the monitoring of the adsorption of the DAEs at the surface of the AuNPs and a plasmonic nanoantenna effect This nanoantenna effect generating a large enhancement of the electromagnetic field in the close vicinity of the nanoparticle was expected to increase the efficiency of the photocycloreversion reaction its quantum yield leading to a more symmetric switching The switching of the dithienylethene DTE molecules was first characterized for the molecules alone in solution Then the functionalization of 28 nm gold nanoparticles deposited on ITO by the DTE molecules was monitored in situ by UV-visible spectroscopy Switching measurement on the samples ITO AuNPs DTE were performed by UV-visible spectroscopy combined with an irradiation set-up It resulted that for the diarylethene molecules chosen for this study connected to 28 nm AuNPs although the switching capacity was preserved upon grafting on the AuNPs the quenching was largely dominant As a consequence a slowing of the photo-induced reactions was caused and not an acceleration Gold nanoparticles were also studied at the unique nanoparticle scale by AFM and hypermicroscopy dark field microscopy coupled to UV-visible spectroscopy On the one hand the functionalization of individual 51 nm gold nanoparticles was monitored by hypermicroscopy Switching measurements were then conducted on the diarylethenes molecules beard by single AuNPs revealing that this switching was comparable to the one previously measured on a more global scale On the other hand asymmetric plasmonic dimers made of a 51 nm AuNP and a 28 nm AuNP were prepared and characterized

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Diarylethenes used as molecular switches for the connection of gold nanoparticles

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