Abstract: A coating made of platinum-gold alloy is provided, together with a method of its preparation by electrodeposition. The alloy is composed of more than 50 atomic percent platinum. The microstructure of the alloy consists of generally ellipsoidal grains. More than half of the grains have a major axis of 10 nm or less.

Abstract: We provide an electrochemical sensor in which working microelectrodes are arranged in an array and interconnected in parallel. The working electrodes are arranged so that in use, they are electrochemically coupled to a counter electrode structure through an electrolyte. The sensor also includes a microporous body arranged so that in use, it is situated at a boundary between a gaseous environment and the electrolyte. In another aspect, we provide a method of sensing in which a sample of gas is admitted to a liquid electrolyte maintained by pores of a porous substrate. A voltage is applied to the liquid electrolyte, and an electrical response to the applied voltage is observed, thereby to detect electrochemical evidence of an analyte within the liquid electrolyte.