Synthesis of water-soluble gold clusters in nanosomes displaying robust photoluminescence with very large Stokes shift

F. G. REQUEJO; RAMALLO LÓPEZ, J.M.; M. ARTURO LÓPEZ-QUINTELA; B. SANTIAGO-GONZÁLEZ; C. VÁZQUEZ-VÁZQUEZ

ADVANCES IN COLLOID AND INTERFACE SCIENCE.

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 455 p. 154 - 162

0001-8686

This paper reports a novel procedure using nanosomes, made of bola-hydroxyl and mercapto-palmiticacids, 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 onligand-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 compartmentsdue 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 clustercomplexes (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 ofbiomolecules (through the terminal COO groups) making these systems very attractive as biomarkersand offering, at the same time, a novel general strategy of fabricating stable atom-level quantum dots withlarge Stokes shifts of great importance in many sensor applications.