Nanois a big prefix-word. Much of contemporary chemistry focuses on small scale structures, and indeed, molecular science is intrinsically on the nanometer scale. Selecting material for this review of “nanoelectrochemistry” involved a necessary arbitrariness of defining what “nano” means. Here, it refers to a dimensional scale of electrodes and electrochemical events, as opposed to time or volume or mass. Still, most of molecular chemistry fits within the 1-1000 nm range of dimensions, as does a substantial body of charged or conducting substances, e.g., microand nanoparticles, colloids, emulsions, and aerosols. The topology of conducting substances can have nanoscopic dimensions, with mesoporous materials such as areogels and xerogels being contemporary examples. These are important topics, as are nanoparticle applications in bioanalysis, catalysis, and electrocatalysis, and nanomaterials such as fullerenes, carbon nanotubes and networks, semiconductor nanoparticles, and arrays of nanoelectrodes and nanopores. With apologies to those topics, I have chosen to whittle the scenery down to the electrochemistry of nanoparticles, and single nanoelectrodes and nanopores. Within these, attention will be biased toward metal nanoparticles having dimensions of only a small number of nanometers, because it is in the 10 nm and lower size range where many significant recent advances have been made. Similarly, I will focus mainly on single nanoelectrodes and nanopores, as opposed to arrays thereof. The literature cited here is predominantly not over a decade old; a lot has happened, and quickly. I hope the reader will find it an interesting decade. What has promoted the rapid advances in the 1-10 nm range of dimensions? For nanoparticles, progress has been stimulated by synthetic innovations; for single nanoelectrodes and single nanopores, similarly by advances in methods of fabrication. Further, while making something that is really small can be special, it does not push science forward unless one can demonstrate its size and shape and chemical composition. So some substantial attention will be given to developments in fabrication and characterization. Knowing what you have prompts the more interesting and burning questions of how do its properties (of any kind, spectroscopic, electron transfer, etc). depend on its size, on the dimensions of other substances and structures that it interacts with (as in a nanopore), on the particular geometry of the small size, and of course on the extent that the chemist and electrochemist can tailor the composition and/or surface of the small particle/electrode/pore object to further expand its range of properties and usefulness. The authors cited in this report are leaving the first trackssto some extent tentative trackssin the scientific sand in these areas of nanoscience.

Nanoelectrochemistry: metal nanoparticles, nanoelectrodes, and nanopores.

Carceplexes and Hemicarceplexes

Films of monolayer protected Au clusters (MPCs) with mixed alkanethiolate and omega-carboxylate alkanethiolate monolayers, linked together in a network polymer by carboxylate-Cu2+-carboxylate bridges, exhibit electronic conductivities (sigma(EL)) that vary with both the numbers of methylene segments in the ligands and the bathing medium (N2, liquid or vapor). A chainlength-dependent swelling/contraction of the film's internal structure is shown to account for changes in sigma(EL). The linker chains appear to have sufficient flexibility to collapse and fold with varied degrees of film swelling or dryness. Conductivity is most influenced (exponentially dependent) by the chainlength of the nonlinker (alkanethiolate) ligands, a result consistent with electron tunneling through the alkanethiolate chains and nonbonded contacts between those chains on individual, adjacent MPCs. The sigma(EL) results concur with the behavior of UV-vis surface plasmon adsorption bands, which are enhanced for short nonlinker ligands and when the films are dry. The film conductivities respond to exposure to organic vapors, decreasing in electronic conductivity and increasing in mass (quartz crystal microgravimetry, QCM). In the presence of organic vapor, the flexible network of linked nanoparticles allows for a swelling-induced alteration in either length or chemical nature of electron tunneling pathways or both.

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Electron hopping conductivity and vapor sensing properties of flexible network polymer films of metal nanoparticles.

Photochemistry of metal nitrosyl complexes. Delivery of nitric oxide to biological targets

The electrochemical redox reactions of organic polymers bearing robust unpaired electrons were investigated to determine the applicability of these polymers to rechargeable batteries. Such an “orga...

Organic Radical Battery Approaching Practical Use

A discussion of electrochemical techniques for the detection of nitric oxide

This paper reports the discovery of three remarkable solvent mixtures that extend the useable range of electrochemical voltammetry in fluid electrolyte solutions to temperatures that approach the boiling point of liquid nitrogen. As part of an ongoing effort to develop the methodology to fabricate electrodes from copper oxide ceramic superconductors and study their response below their superconducting critical temperature, T{sub c} we found it necessary to extend the limits of low-temperature electrochemistry. Gold microband electrodes are employed in the present report to explore the voltammetric limits of the new low-temperature solvents.

Fluid Electrolyte Solutions for Electrochemistry at Near Liquid Nitrogen Temperatures

The redox conductivity of mixed valent poly(vinylferrocene) films is measured by a steady state method using interdigitated array electrodes. Spectroelectrochemistry shows that the Fc/Fc + site concentration ratio has a simple Nernstian dependence on applied potential. Measurements of the bimolecular Fc/Fc + electron self-exchange rate constant using concentration gradient- and electrical gradient-driven electron transfers are in agreement and give an average value of 2×10 5 M -1 s -1 for dry N 2 bathed films. The solid state dispersive transport model of Scher, Montroll, and Pfister is used in interpretation of the electrical potential gradient-driven electron transport

Solid State Electron Self-Exchange Dynamics in Mixed Valent Poly(vinylferrocene) Films

Electron self-exchange rates in a site-dilutable osmium bipyridine redox polymer

An electrode sensor which may be used to specifically and quantitatively measure nitric oxide is provided, as well as a method of preparing and using such an electrode sensor to measure nitric oxide concentration in solution.

Melani G. Sullivan

Papers

A discussion of electrochemical techniques for the detection of nitric oxide

Fluid Electrolyte Solutions for Electrochemistry at Near Liquid Nitrogen Temperatures

Solid State Electron Self-Exchange Dynamics in Mixed Valent Poly(vinylferrocene) Films

Electron self-exchange rates in a site-dilutable osmium bipyridine redox polymer

Nitric oxide-specific electrode