The mechanism and kinetics of the electro-catalytic oxidation of hydrazine by graphene oxide platelets randomly decorated with palladium nanoparticles are deduced using single particle impact electrochemical measureme...The mechanism and kinetics of the electro-catalytic oxidation of hydrazine by graphene oxide platelets randomly decorated with palladium nanoparticles are deduced using single particle impact electrochemical measurements in buffered aqueous solutions across the pH range 2–11. Both hydrazine, N2H4, and protonated hydrazine N2H5+ are shown to be electroactive following Butler-Volmer kinetics, of which the relative contribution is strongly pH-dependent. The negligible interconversion between N2H4 and N2H5+ due to the sufficiently short timescale of the impact voltammetry, allows the analysis of the two electron transfer rates from impact signals thus reflecting the composition of the bulk solution at the pH in question. In this way the rate determining step in the oxidation of each specie is deduced to be a one electron step in which no protons are released and so likely corresponds to the initial formation of a very short-lived radical cation either in solution or adsorbed on the platelet. Overall the work establishes a generic method for the elucidation of the rate determining electron transfer in a multistep process free from any complexity imposed by preceding or following chemical reactions which occur on the timescale of conventional voltammetry.展开更多
The fabrication and electrochemical interrogation of very high density single-antibody nanoarrays is reported.Gold nanodots,15 nm in diameter,arranged in large(cm2)square arrays with a pitch of 200 nm,are used as carr...The fabrication and electrochemical interrogation of very high density single-antibody nanoarrays is reported.Gold nanodots,15 nm in diameter,arranged in large(cm2)square arrays with a pitch of 200 nm,are used as carriers for primary antibodies(immunoglobulin G(IgG)),further recognized by secondary redox-labeled detection antibodies.Ensemble scale interrogation of the antibody array by cyclic voltammetry,and nanoscale interrogation of individual nanodots by mediator tethered atomic forcescanning electrochemical microscopy(Mt/AFM-SECM),enable the occupancy of nanodots by single antibody molecules to be demonstrated.Experiments involving the competitive adsorption of antibodies of different species onto the nanodots evidence the possibility of using single-antibody nanoarrays for digital electrochemical immunoassays.展开更多
Scanning electrochemical cell microscopy(SECCM)is increasingly applied to determine the intrinsic catalytic activity of single electrocatalyst particle.This is especially feasible if the catalyst nanoparticles are lar...Scanning electrochemical cell microscopy(SECCM)is increasingly applied to determine the intrinsic catalytic activity of single electrocatalyst particle.This is especially feasible if the catalyst nanoparticles are large enough that they can be found and counted in post-SECCM scanning electron microscopy images.Evidently,this becomes impossible for very small nanoparticles and hence,a catalytic current measured in one landing zone of the SECCM droplet cannot be correlated to the exact number of catalyst particles.We show,that by introducing a ruler method employing a carbon nanoelectrode decorated with a countable number of the same catalyst particles from which the catalytic activity can be determined,the activity determined using SECCM from many spots can be converted in the intrinsic catalytic activity of a certain number of catalyst nanoparticles.展开更多
基金Open access funding provided by University of Oxford.
文摘The mechanism and kinetics of the electro-catalytic oxidation of hydrazine by graphene oxide platelets randomly decorated with palladium nanoparticles are deduced using single particle impact electrochemical measurements in buffered aqueous solutions across the pH range 2–11. Both hydrazine, N2H4, and protonated hydrazine N2H5+ are shown to be electroactive following Butler-Volmer kinetics, of which the relative contribution is strongly pH-dependent. The negligible interconversion between N2H4 and N2H5+ due to the sufficiently short timescale of the impact voltammetry, allows the analysis of the two electron transfer rates from impact signals thus reflecting the composition of the bulk solution at the pH in question. In this way the rate determining step in the oxidation of each specie is deduced to be a one electron step in which no protons are released and so likely corresponds to the initial formation of a very short-lived radical cation either in solution or adsorbed on the platelet. Overall the work establishes a generic method for the elucidation of the rate determining electron transfer in a multistep process free from any complexity imposed by preceding or following chemical reactions which occur on the timescale of conventional voltammetry.
文摘The fabrication and electrochemical interrogation of very high density single-antibody nanoarrays is reported.Gold nanodots,15 nm in diameter,arranged in large(cm2)square arrays with a pitch of 200 nm,are used as carriers for primary antibodies(immunoglobulin G(IgG)),further recognized by secondary redox-labeled detection antibodies.Ensemble scale interrogation of the antibody array by cyclic voltammetry,and nanoscale interrogation of individual nanodots by mediator tethered atomic forcescanning electrochemical microscopy(Mt/AFM-SECM),enable the occupancy of nanodots by single antibody molecules to be demonstrated.Experiments involving the competitive adsorption of antibodies of different species onto the nanodots evidence the possibility of using single-antibody nanoarrays for digital electrochemical immunoassays.
基金funding from the European Research Council(ERC)under the European Unions Horizon 2020 research and innovation programme(grant agreement CasCat[833408])well as from the European Unions Horizon 2020 research and innovation program under the Marie Sktodowska-Curie MSCA-ITN Single-Entity Nanoelectrochemistry,Sentinel[812398]+2 种基金S.S.and C.A.acknowledge the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)within the project[440951282]X.X.C.acknowledges financial support from the Liaoning BaiQianWan Talents Program,China(No.2019B042)the Excellent Young Scientific and Technological Talents Project of Educational Department of Liaoning Province,China(No.2020LNQN07).
文摘Scanning electrochemical cell microscopy(SECCM)is increasingly applied to determine the intrinsic catalytic activity of single electrocatalyst particle.This is especially feasible if the catalyst nanoparticles are large enough that they can be found and counted in post-SECCM scanning electron microscopy images.Evidently,this becomes impossible for very small nanoparticles and hence,a catalytic current measured in one landing zone of the SECCM droplet cannot be correlated to the exact number of catalyst particles.We show,that by introducing a ruler method employing a carbon nanoelectrode decorated with a countable number of the same catalyst particles from which the catalytic activity can be determined,the activity determined using SECCM from many spots can be converted in the intrinsic catalytic activity of a certain number of catalyst nanoparticles.
