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The measurement of key molecules in individual cells with minimal disruption to the biological milieu is the next frontier in single-cell analyses. Nanoscale devices are ideal analytical tools because of their small size and their potential for high spatial and temporal resolution recordings. Here, we report the fabrication of disk-shaped carbon nanoelectrodes whose radius can be precisely tuned within the range 5-200 nm. The functionalization of the nanoelectrode with platinum allowed the monitoring of oxygen consumption outside and inside a brain slice. Furthermore, we show that nanoelectrodes of this type can be used to impale individual cells to perform electrochemical measurements within the cell with minimal disruption to cell function. These nanoelectrodes can be fabricated combined with scanning ion conductance microcopy probes which should allow high resolution electrochemical mapping of species on or in living cells.

The development of innovative techniques for the functionalization of carbon nanotubes that preserve their exceptional quality, while robustly enriching their properties, is a central issue for their integration in applications. In this work, we describe the formation of a covalent network of porphyrins around MWNT surfaces. The approach is based on the adsorption of cobalt(II) meso-tetraethynylporphyrins on the nanotube sidewalls followed by the dimerization of the triple bonds via Hay-coupling; during the reaction, the nanotube acts as a template for the formation of the polymeric layer. The material shows an increased stability resulting from the cooperative effect of the multiple π-stacking interactions between the porphyrins and the nanotube and by the covalent links between the porphyrins. The nanotube hybrids were fully characterized and tested as the supported catalyst for the oxygen reduction reaction (ORR) in a series of electrochemical measurements under acidic conditions. Compared to similar systems in which monomeric porphyrins are simply physisorbed, MWNT-CoP hybrids showed a higher ORR activity associated with a number of exchanged electrons close to four, corresponding to the complete reduction of oxygen into water.

Scanning electrochemical microscopy (SECM), is a recent analytical technique in electrochemistry, which was developed in the 1990s and uses microelectrodes to probe various surfaces. Even with the well-known disc microelectrodes, the system geometry is not as simple as in regular electrochemistry. As a consequence even the simplest experiments, the so-called positive and negative feedback approach curves, cannot be described with exact analytical expressions. This review gathers all the analytical expressions available in the SECM literature in steady-state feedback experiments. Some of them are claimed as general expressions, other are presented as approximate. Their validity is discussed in the light of the current understanding and computer facilities.

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Organic semiconductors have great potential for producing hydrogen in a durable and economically viable manner, as they rely on readily available materials and can be solutionprocessed over large areas. With the objective of building efficient hybrid organic-inorganic photoelectrochemical cells, we combined a noble metal-free and solution-processable catalyst for proton reduction, MoS 3 , and a poly-(3-hexylthiophene):phenyl-C 61 -butyric acid methyl ester (P3HT:PCBM) bulk heterojunction (BHJ). Different interfacial layers were investigated to improve the charge transfer between P3HT:PCBM and MoS 3 . Metallic Al\Ti interfacial layers led to an increase of the photocurrent up to 8 mA cm −2 at reversible hydrogen electrode (RHE) potential with a 0.6 V anodic shift of the HER onset potential, a value close to the open circuit potential of the P3HT:PCBM solar cell. A 50 nm thick C 60 layer also works as interfacial layer, with current density reaching 1 mA cm −2 at RHE potential. Moreover, two recently highlighted 1 figures-of-merit, measuring the ratio of power saved, Φ saved,ideal and Φ saved,NPAC , were evaluated and discussed to compare the performances of various photocathodes assessed in a three-electrode configuration. Φ saved,ideal and Φ saved,NPAC use the RHE and a non-photoactive electrode with identical catalyst as dark electrode, respectively. They provide different information especially for the differentiation of the role of the photogenerating layer and the role of the catalyst. Best results were obtained with the Al\Ti metallic interlayer, with Φ saved,ideal and Φ saved,NPAC reaching 0.64 % and 2.05 % respectively.

This study correlates the work function of the hole-extracting layer and the efficiency of photocathodes for the photo-production of hydrogen.

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