Patent ID: 6933153

Claim:
A method for producing a metal ion-specific capacity affinity sensor suitable for determining the presence of a certain heavy metal ion of interest in a contacting solution by capacitance measurement, comprising the steps of: a) providing a piece of a noble metal having a surface; b) providing a first self-assembling monolayer-forming molecule comprising a coupling group; c) contacting said noble metal piece in step a) with the first self-assembling monolayer-forming molecule in step b), thereby obtaining a first self-assembling monolayer on said surface of said noble metal piece; d) contacting said first self-assembling monolayer on said noble metal piece with a molecule specifically binding said heavy metal ion, thereby coupling said molecule to said first self-assembling monolayer; and e) contacting the piece obtained in step d) with a second self-assembling monolayer-forming molecule, thereby obtaining a noble metal surface that is at least 90% covered with a self-assembling monolayer, wherein the coupling reaction in step d) is carried out in presence of polyethylene-glycol-diglycidyl-ether such that the polyethylene-glycol-diglycidyl-ether entraps the molecule and facilitates the coupling of said molecule to the first self assembling monolayer.