title: Synthesis of water-soluble gold clusters in nanosomes displaying robust photoluminescence with very large Stokes shift.
abstract: This paper reports a novel procedure using nanosomes, made of bola-hydroxyl and mercapto-palmitic acids, for the production of gold clusters with robust luminescent emissions and very large Stokes shifts. It shows that these results cannot be explained by the currently accepted mechanism based on ligand-to-metal charge transfer absorptions involving electron-rich ligands attached to the cluster core. Exhaustive characterization of the cluster samples using Mass Spectrometry, HR-TEM/STEM, XPS, EXAFS, and steady-state and time-resolved luminescence allows to deduce that a mixture of two cluster sizes, having non-closed shell electronic configurations, are firstly generated inside the nanosome compartments due to the difference in bonding strength of the two types of terminal groups in the fatty acids. This initial bimodal cluster size distribution slowly evolves into very stable, closed-shell Au cluster complexes (Au6-Au16 and Au5-Au14) responsible for the observed luminescent properties. The very small (≈1.2 nm) synthesized cluster complexes are water soluble and suitable to be used for the conjugation of biomolecules (through the terminal COO(-) groups) making these systems very attractive as biomarkers and offering, at the same time, a novel general strategy of fabricating stable atom-level quantum dots with large Stokes shifts of great importance in many sensor applications.
authors.affiliation: Laboratorio de Magnetismo y Nanotecnología, Instituto de Investigaciones Tecnológicas, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Santiago-González
authors.affiliation: Laboratorio de Magnetismo y Nanotecnología, Instituto de Investigaciones Tecnológicas, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Vázquez-Vázquez
authors.affiliation: Laboratorio de Magnetismo y Nanotecnología, Instituto de Investigaciones Tecnológicas, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain.
authors.forename: M C
authors.initials: MC
authors.lastname: Blanco-Varela
authors.affiliation: Centro de Química-Física Molecular and IN - Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal.
authors.forename: J M
authors.initials: JM
authors.lastname: Gaspar Martinho
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas - INIFTA (CONICET, UNLP), Diagonal 113 y calle 64, 1900 La Plata, Argentina.
authors.forename: J M
authors.initials: JM
authors.lastname: Ramallo-López
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas - INIFTA (CONICET, UNLP), Diagonal 113 y calle 64, 1900 La Plata, Argentina.
authors.forename: F G
authors.initials: FG
authors.lastname: Requejo
authors.affiliation: Laboratorio de Magnetismo y Nanotecnología, Instituto de Investigaciones Tecnológicas, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain. Electronic address: malopez.quintela@usc.es.
authors.forename: M A
authors.initials: MA
authors.lastname: López-Quintela
keywords: Cluster–cluster complexes; Large Stokes shifts; Luminescent gold clusters; Nanosomes