Abstract: An electrochemical sensor is provided containing a supporting material having a surface of noble metal such as gold or palladium to which is bound an enzyme such as glucose oxidase via binding molecules. The binding molecules are in the form of a homogenous monolayer and are bound to the metal surface by anchor groups such as thiol, disulphide or phosphine groups. The enzyme is linked to the binding molecules by an ionic bond, a covalent bond or a metal-chelate bond. The binding molecules may contain a spacer such as an alkylene chain. Coverage of the binding molecules on the metal surface is less than the maximum coverage to optimize enzyme coverage, decrease response time of the sensor and increase signal yield per surface area. The monolayer may contain diluent molecules which are not linked to an enzyme and which are bound to the metal surface via anchor groups.