title: Determination of redox reaction rates and orders by in situ liquid cell electron microscopy of Pd and Au solution growth.
abstract: In-situ liquid cell transmission and scanning transmission electron microscopy (TEM/STEM) experiments are important, as they provide direct insight into processes in liquids, such as solution growth of nanoparticles, among others. In liquid cell TEM/STEM redox reaction experiments, the hydrated electrons e(-)aq created by the electron beam are responsible for the reduction of metal-ion complexes. Here we investigate the rate equation of redox reactions involving reduction by e(-)aq generated by the electron beam during in situ liquid TEM/STEM. Specifically we consider the growth of Pd on Au seeds in aqueous solutions containing Pd-chloro complexes. From the quantification of the rate of Pd deposition at different electron beam currents and as a function of distance from a stationary, nanometer-sized exciting beam, we determine that the reaction is first order with respect to the concentration of hydrated electrons, [e(-)aq]. By comparing Pd- and Au-deposition, we further demonstrate that measurements of the local deposition rate on nanoparticles in the solution via real-time imaging can be used to measure not only [e(-)aq] but also the rate of reduction of a metal-ion complex to zerovalent metal atoms in solution.
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Eli A
authors.initials: EA
authors.lastname: Sutter
authors.forename: Peter W
authors.initials: PW
authors.lastname: Sutter
mesh_terms: D006046:Gold / Q000737:chemistry*; D008854:Microscopy, Electron; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry*; D010316:Particle Size; D012996:Solutions; D013499:Surface Properties
chemical_list: D012996:Solutions; D010165:Palladium; D006046:Gold