title: Optical switching of coupled plasmons of Ag-nanoparticles by photoisomerisation of an azobenzene ligand.
abstract: The optical switching of coupled plasmons of silver nanoparticles derivatised with a photoisomerisable azobenzene ligand is presented. It is shown that nanoparticle clusters, linked with an azobenzene dithiol molecule, display switchable optical properties. The photoisomerisation of the linker molecule was used to vary the separation between nanoparticles, which was monitored by changes in the UV-Vis-spectra of the plasmon band of adjacent nanoparticles. A red-shift due to the appearance of a coupled longitudinal plasmon band was observed resulting from the formation of nanoparticle clusters. The maximum absorbance wavelength of this secondary plasmon band was altered by isomerisation of the linker and the spectral changes observed were in good agreement with theory and earlier measurements for gold. Evidence of energy transfer between a nanoparticle and an azobenzene terminated monothiol attached to it was also observed in the UV-Vis spectra.
authors.affiliation: Laboratory of Physical Chemistry and Electrochemistry, Helsinki University of Technology, FIN-02015, HUT, Finland.
authors.forename: Päivi
authors.initials: P
authors.lastname: Ahonen
authors.forename: David J
authors.initials: DJ
authors.lastname: Schiffrin
authors.forename: Jerzy
authors.initials: J
authors.lastname: Paprotny
authors.forename: Kyösti
authors.initials: K
authors.lastname: Kontturi
mesh_terms: D001391:Azo Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000528:radiation effects; D004735:Energy Transfer; D006046:Gold / Q000737:chemistry; D007536:Isomerism; D008024:Ligands; D046529:Microscopy, Electron, Transmission / Q000379:methods; D008958:Models, Molecular; D015394:Molecular Structure; D053758:Nanoparticles / Q000737:chemistry*; D055095:Optics and Photonics; D010777:Photochemistry; D012680:Sensitivity and Specificity; D012834:Silver / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D020349:Surface Plasmon Resonance; D013499:Surface Properties; D014466:Ultraviolet Rays
chemical_list: D001391:Azo Compounds; D008024:Ligands; D012834:Silver; D006046:Gold; C009850:azobenzene