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Abstract Transparent microelectrodes have received much attention from the biomedical community due to their unique advantages in concurrent crosstalk‐free electrical and optical interrogation of cell/tissue activity. Despite recent progress in constructing transparent microelectrodes, a major challenge is to simultaneously achieve desirable mechanical stretchability, optical transparency, electrochemical performance, and chemical stability for high‐fidelity, conformal, and stable interfacing with soft tissue/organ systems. To address this challenge, we have designed microelectrode arrays (MEAs) with gold‐coated silver nanowires (Au–Ag NWs) by combining technical advances in materials, fabrication, and mechanics. The Au coating improves both the chemical stability and electrochemical impedance of the Au–Ag NW microelectrodes with only slight changes in optical properties. The MEAs exhibit a high optical transparency >80% at 550 nm, a low normalized 1 kHz electrochemical impedance of 1.2–7.5 Ω cm², stable chemical and electromechanical performance after exposure to oxygen plasma for 5 min, and cyclic stretching for 600 cycles at 20% strain, superior to other transparent microelectrode alternatives. The MEAs easily conform to curvilinear heart surfaces for colocalized electrophysiological and optical mapping of cardiac function. This work demonstrates that stretchable transparent metal nanowire MEAs are promising candidates for diverse biomedical science and engineering applications, particularly under mechanically dynamic conditions. 

Abstract Although most class (b) transition metals have been studied in regard to CH₄activation, divalent silver (Ag^II), possibly owing to its reactive nature, is the only class (b) high‐valent transition metal center that is not yet reported to exhibit reactivities towards CH₄activation. We now report that electrochemically generated Ag^IImetalloradical readily functionalizes CH₄into methyl bisulfate (CH₃OSO₃H) at ambient conditions in 98 % H₂SO₄. Mechanistic investigation experimentally unveils a low activation energy of 13.1 kcal mol⁻¹, a high pseudo‐first‐order rate constant of CH₄activation up to 2.8×10³ h⁻¹at room temperature and a CH₄pressure of 85 psi, and two competing reaction pathways preferable towards CH₄activation over solvent oxidation. Reaction kinetic data suggest a Faradaic efficiency exceeding 99 % beyond 180 psi CH₄at room temperature for potential chemical production from widely distributed natural gas resources with minimal infrastructure reliance.