Nanoscopic assemblies between supramolecular redox active metallodendrons and gold nanoparticles:: Synthesis, characterization, and selective recognition of H2PO4-, HSO4-, and adenosine-5′-triphosphate (ATP2-) anions

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 (AB(3) units) or Brust-type direct synthesis from a 1:1 mixture of dodecanethiol and dendronized thiol (AB(9) 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 H2PO4- 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 CH2Cl2 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.