title: Self-assembly of thiolated cyanine aggregates on Au(111) and Au nanoparticle surfaces.
abstract: Heptamethinecyanine J-aggregates display sharp, intense fluorescence emission making them attractive candidates for developing a variety of chem-bio-sensing applications. They have been immobilized on planar thiol-covered Au surfaces and thiol-capped Au nanoparticles by weak molecular interactions. In this work the self-assembly of novel thiolated cyanine (CNN) on Au(111) and citrate-capped AuNPs from solutions containing monomers and J-aggregates has been studied by using STM, XPS, PM-IRRAS, electrochemical techniques and Raman spectroscopy. Data show that CNN species adsorb on the Au surfaces by forming thiolate-Au bonds. We found that the J-aggregates are preferentially adsorbed on the Au(111) surface directly from the solution while adsorbed CNN monomers cannot organize into aggregates on the substrate surface. These results indicate that the CNN-Au interaction is not able to disorganize the large J-aggregates stabilized by π-π stacking to optimize the S-Au binding site but it is strong enough to hinder the π-π stacking when CNNs are chemisorbed as monomers. The optical properties of the J-aggregates remain active after adsorption. The possibility of covalently bonding CNN J-aggregates to Au planar surfaces and Au nanoparticles controlling the J-aggregate/Au distance opens a new path regarding their improved stability and the wide range of biological applications of both CNN and AuNP biocompatible systems.
authors: CHIDECAR, Departamento de Química Orgánica, FCEN, UBA, Ciudad Universitaria, Pabellón II, Buenos Aires, 1428, Argentina.
authors: Guillermo O
authors: GO
authors: Menéndez
authors: Emiliano
authors: E
authors: Cortés
authors: Doris
authors: D
authors: Grumelli
authors: Lucila P
authors: LP
authors: Méndez De Leo
authors: Federico J
authors: FJ
authors: Williams
authors: Nicolás G
authors: NG
authors: Tognalli
authors: Alejandro
authors: A
authors: Fainstein
authors: María Elena
authors: ME
authors: Vela
authors: Elizabeth A
authors: EA
authors: Jares-Erijman
authors: Roberto C
authors: RC
authors: Salvarezza
mesh_terms: D003486:Cyanides / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D003486:Cyanides; D046911:Macromolecular Substances; D013438:Sulfhydryl Compounds; D006046:Gold