Nanoscopic Assemblies between Supramolecular Redox Active Metallodendrons and Gold Nanoparticles: Synthesis, Characterization, and Selective Recognition of H 2 PO 4 - , HSO 4 - , and Adenosine-5′-Triphosphate (ATP 2- ) Anions Marie-Christine Daniel, ² Jaime Ruiz, ² Sylvain Nlate, ² Jean-Claude Blais, ‡ and Didier Astruc* ,² Contribution from the Groupe Nanoscience et Catalyse, LCOO, UMR CNRS N. 5802, UniVersite ´ Bordeaux I, 33405 Talence Cedex, France and LCSOB, UMR CNRS N. 7613, UniVersite ´ Paris VI, 75252 Paris, France Received November 1, 2002 ; E-mail: d.astruc@lcoo.u-bordeaux.fr Abstract: Tri- and nonaferrocenyl thiol dendrons have been synthesized and used to assemble dendronized gold nanoparticles either by the ligand-substitution method from dodecanethiolate-gold nanoparticles (AB3 units) or Brust-type direct synthesis from a 1:1 mixture of dodecanethiol and dendronized thiol (AB9 units). The dendronized colloids are a new type of dendrimers with a gold colloidal core. Two colloids containing a nonasilylferrocenyl dendron have been made; they bear respectively 180 and 360 ferrocenyl units at the periphery. These colloids selectively recognize the anions H 2PO4 - and adenosine-5′-triphosphate (ATP 2- ) with a positive dendritic effect and can be used to titrate these anions because of the shift of the CV wave even in the presence of other anions such as Cl - and HSO4 - . Recognition is monitored by the appearance of a new wave at a less positive potential in cyclic voltammetry (CV). The anion HSO4 - is also recognized and titrated by the dendronized colloid containing the tris-amidoferrocenyl units, because of the progressive shift of the CV wave until the equivalence point. These dendronized colloids can form robust modified electrodes by dipping the naked Pt electrode into a CH 2Cl2 solution containing the colloids. The robustness is all the better as the dendron is larger. These modified electrodes can recognize H2PO4 - , ATP 2- and HSO4 - , be washed with minimal loss of adsorbed colloid, and be reused. Introduction Nanoscopic supramolecular assemblies 1 between dendrimers 2 and colloids 3 should be fruitful to provide a new generation of materials that are likely to give applications as sensors, 1,4,5 catalysts, 1,3,6 and components for molecular electronics. 1,7 So far, only very few examples of assemblies between dendrimers or dendrons 8 and colloids are known. 1,9 We have been interested in such assemblies disclosing supramolecular properties in order to provide means to approach new sensors. The recognition of anions has indeed been the subject of special scrutiny, given their role in biology. 10 In particular, Beer has shown various examples of redox anion recognition by amidoferrocenes bound to endoreceptors. 11 We have addressed the use of redox-active ² University Bordeaux I. 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