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Abstract
In this Article we have used new approaches to investigate a well-known chemical process, the propagation of electrochemical signals through a thin glass membrane. This process, which has been extensively studied over the last century, is the basis of the response of a potentiometric glass pH sensor; however, no amperometric glass sensors have yet been reported because of its high ohmic resistance. Voltammetry at nanoelectrodes has revealed that water molecules can diffuse through nanometre-thick layers of dry glass and undergo oxidation/reduction at the buried platinum surface. After soaking for a few hours in an aqueous solution, voltammetric waves of other redox couples, such as Ru(NH3)63+/2+, could also be obtained at the glass-covered platinum nanoelectrodes. This behaviour suggests that the nanometre-thick insulating glass sheath surrounding the platinum core can be largely converted to hydrated gel, and electrochemical processes occur at the platinum/hydrogel interface. Potential applications range from use in nanometre-sized solid-state pH probes and determination of the water content in organic solvents to glass-modified voltammetric sensors and electrocatalysts. Glass is widely used as an electrical insulator in electrodes, but in spite of its high resistance, 100-nm-thick layers of glass have now been shown to be sufficiently conductive for electrochemical measurements. Obtaining redox couples through glass-covered nanoelectrodes suggests that the pH response of the glass is due to the formation of a hydrogel layer in acidic solution. Cite this article
Velmurugan, J., Zhan, D. & Mirkin, M. Electrochemistry through glass. Nature Chem 2, 498–502 (2010). https://doi.org/10.1038/nchem.645 