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Nanoelectrodes have key advantages compared to electrodes of conventional size and are the tool of choice for numerous applications in both fundamental electrochemistry research and bioelectrochemical analysis. This Minireview summarizes recent advances in the development, characterization, and use of nanoelectrodes in nanoscale electroanalytical chemistry. Methods of nanoelectrode preparation include laser-pulled glass-sealed metal nanoelectrodes, mass-produced nanoelectrodes, carbon nanotube based and carbon-filled nanopipettes, and tunneling nanoelectrodes. Several new topics of their recent application are covered, which include the use of nanoelectrodes for electrochemical imaging at ultrahigh spatial resolution, imaging with nanoelectrodes and nanopipettes, electrochemical analysis of single cells, single enzymes, and single nanoparticles, and the use of nanoelectrodes to understand single nanobubbles.

This article reviews recent work involving the development and application of nanoelectrodes in electrochemistry and related areas. We first discuss common analytical methods for characterizing the size, shape, and quality of nanoelectrodes, including electron microscopy, steady-state cyclic voltammetry, scanning electrochemical microscopy, and surface modification. We then emphasize recent developments in fabrication techniques that have led to structurally well-defined nanoelectrodes. We highlight recent advances in the application of nanoelectrodes in important analytical chemistry areas, such as single-molecule studies, single-nanoparticle electrochemistry, and measurements of neurotransmitters from single neuronal cells.

Platinum (Pt) nanocrystals have demonstrated to be an effective catalyst in many heterogeneous catalytic processes. However, pioneer facets with highest activity have been reported differently for various reaction systems. Although Pt has been the most important counter electrode material for dye-sensitized solar cells (DSCs), suitable atomic arrangement on the exposed crystal facet of Pt for triiodide reduction is still inexplicable. Using density functional theory, we have investigated the catalytic reaction processes of triiodide reduction over {100}, {111} and {411} facets, indicating that the activity follows the order of Pt(111) > Pt(411) > Pt(100). Further, Pt nanocrystals mainly bounded by {100}, {111} and {411} facets were synthesized and used as counter electrode materials for DSCs. The highest photovoltaic conversion efficiency of Pt(111) in DSCs confirms the predictions of the theoretical study. These findings have deepened the understanding of the mechanism of triiodide reduction at Pt surfaces and further screened the best facet for DSCs successfully.

Acetylene black nanoparticles (AB) were dispersed into water in the presence of dihexadecyl hydrogen phosphate (DHP), and used to modify the surface of glassy carbon electrode (GCE) via solvent evaporation. Due to the high sorption ability, large surface area and numerous active sites, the AB-modified GCE showed a strong enhancement effect on the oxidation of erythromycin, and greatly increased the peak current. The oxidation mechanism was investigated at the surface of AB-modified GCE, and two oxidation peaks were observed for erythromycin. The first oxidation peak is attributed to the removal of one electron from the nitrogen atom to form an aminium cation radical, and the second peak is due to the oxidation of the chemical product of aminium cation radical. The influence of pH value, amount of AB, accumulation potential and time was also studied, and a novel electrochemical method was developed for the determination of erythromycin. The linear range is from 2 × 10 −7 to 1 × 10 −5 M, and the limit of detection is 8 × 10 −8 M (58.72 μg L −1 ).

We present the preparation, characterization, and analytical application of silica nanochannels in the size range of 5-100 nm. These cylindrical-shaped nanochannels are prepared using a simple laser-assisted mechanical pulling process, followed by partial enclosure into a glass micropipet. The nanochannels are characterized using a combination of optical microscopy, scanning electron microscopy (SEM), and resistance measurements in an electrolyte solution. The SEM results show that the nanochannel has circular geometry at the orifice. Ohmic response has been obtained from current-voltage measurements in KCl solutions using a silica nanochannel as small as 9 nm in diameter. These nanochannels have been utilized to sense single 40 nm polystyrene nanoparticles. A linear response has been observed between the detection rate and the concentration of nanoparticles in the range of 0-25 nM. The silica nanochannels have also been applied to the study of molecular transport of double-stranded DNA. Electroosmosis-driven molecular translocation has been observed for genomic-length lambda-DNA through a 9 nm nanochannel in a 3 M KCl solution.