title: Generation and detection of single metal nanoparticles using scanning electrochemical microscopy techniques.
abstract: Different pathways towards the generation and detection of a single metal nanoparticle (MNP) on a conductive carbon support for testing as an electrocatalyst are described. Various approaches were investigated including interparticle distance enhancement, electrochemical and mechanical tip-substrate MNP transfer onto macroscopic surfaces, scanning electrochemical microscopy (SECM)-controlled electrodeposition, and the use of selective binding monolayers on carbon fiber electrodes (CFEs) for solution-phase-selective adsorption. A novel SECM technique for electrodepositing MNPs on CFE tips immersed 100-200 nm below the electrolyte level was developed and used to generate single Pt and Ni nanoparticles. Following their generation, we demonstrate electrocatalytic detection of Fe3+ on individual Pt particles with the CFE in a Fe3+/H2SO4 solution. We also describe an approach of attaching MNPs to CFEs by controlling the composition of monolayers bonded to the CFE. By employing a monolayer with a low ratio of binding (e.g., 4-aminopyridine) to nonbinding molecules (e.g., aniline) and controlling the position of the CFE in a colloidal Pt solution with a SECM, we attached a single 15 nm radius Pt nanoparticle to the CFE. Such chemisorbed Pt particles exhibited a stronger adhesion on surface-modified CFEs and better mechanical stability during proton reduction than MNPs electrodeposited directly on the CFE.
authors.affiliation: Department of Chemistry and Biochemistry and the Center for Nano and Molecular Science and Technology, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Ran
authors.initials: R
authors.lastname: Tel-Vered
authors.forename: Allen J
authors.initials: AJ
authors.lastname: Bard
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry; D004563:Electrochemistry; D004566:Electrodes; D008855:Microscopy, Electron, Scanning / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013499:Surface Properties
chemical_list: D010984:Platinum; D002244:Carbon; D009532:Nickel