title: Spiropyran-modified gold nanoparticles: reversible size control of aggregates by UV and visible light irradiations.
abstract: UV or visible light irradiation of gold nanoparticles (AuNPs) modified with a thiol-terminated spiropyran dye promotes reversible aggregation or dispersion of AuNPs. This is facilitated by the electrostatic repulsion/attraction between the AuNPs controlled by the ring-opening/closing photoisomerization of the surface dyes. This photochemical method successfully produces aggregates of AuNPs with tunable sizes (20-340 nm) and narrow size distributions (standard deviation <34%) in a reversible manner. In addition, the formed aggregates, even when left in the dark condition, scarcely change their sizes because the stacking interaction between the ring-opened forms of surface dyes suppresses thermal reverse isomerization and maintains the attractive force between the AuNPs.
authors.affiliation: Research Center for Solar Energy Chemistry and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University , Toyonaka 560-8531, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Shiraishi
authors.forename: Eri
authors.initials: E
authors.lastname: Shirakawa
authors.forename: Kazuya
authors.initials: K
authors.lastname: Tanaka
authors.forename: Hirokatsu
authors.initials: H
authors.lastname: Sakamoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ichikawa
authors.forename: Takayuki
authors.initials: T
authors.lastname: Hirai
mesh_terms: D001578:Benzopyrans / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D007536:Isomerism; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000528:radiation effects / Q000648:ultrastructure; D009574:Nitro Compounds / Q000737:chemistry*; D010316:Particle Size; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D014466:Ultraviolet Rays
chemical_list: D001578:Benzopyrans; D007211:Indoles; D009574:Nitro Compounds; C088184:spiropyran; D006046:Gold