Electrochemical Solid-State Phase Transformations of Silver Nanoparticles
journal contributionposted on 2012-03-28, 00:00 authored by Poonam Singh, Kate L. Parent, Daniel A. Buttry
Adenosine triphosphate (ATP)-capped silver nanoparticles (ATP–Ag NPs) were synthesized by reduction of AgNO3 with borohydride in water with ATP as a capping ligand. The NPs obtained were characterized using transmission electron microscopy (TEM), UV–vis absorption spectroscopy, X-ray diffraction, and energy-dispersive X-ray analysis. A typical preparation produced ATP–Ag NPs with diameters of 4.5 ± 1.1 nm containing ∼2800 Ag atoms and capped with 250 ATP capping ligands. The negatively charged ATP caps allow NP incorporation into layer-by-layer (LbL) films with poly(diallyldimethylammonium) chloride at thiol-modified Au electrode surfaces. Cyclic voltammetry in a single-layer LbL film of NPs showed a chemically reversible oxidation of Ag NPs to silver halide NPs in aqueous halide solutions and to Ag2O NPs in aqueous hydroxide solutions. TEM confirmed that this takes place via a redox-driven solid-state phase transformation. The charge for these nontopotactic phase transformations corresponded to a one-electron redox process per Ag atom in the NP, indicating complete oxidation and reduction of all Ag atoms in each NP during the electrochemical phase transformation.
Cyclic voltammetryhydroxide solutionsNP incorporationAg atomsAg atomSilver NanoparticlesAdenosine triphosphateelectrochemical phase transformationATP capsnontopotactic phase transformationssilver halide NPsUVelectrode surfacesTEM250 ATPAg 2O NPsphase transformationtransmission electron microscopyAg NPsAgNO 3halide solutions