As part of our long-term goal to design a novel type of immunosensor based on IR transduction, we devised two strategies to immobilize derivatives of the herbicide atrazine on the surface of planar gold substrates. Both strategies take advantage of the well-known formation of self-assembled monolayers of thiolates via spontaneous chemisorption of thiols or disulphides on noble metal surfaces. The first strategy involved the direct chemisorption of a disulphide derivative of atrazine, while the second strategy was based on the covalent attachment of a polymer tethered with atrazine derivatives to a previously adsorbed thiolate carrying a carboxylic acid head group. The resulting organic thin films on gold were characterised by polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and XPS. The binding of a polyclonal anti-atrazine antibody to both sensing layers was also tested and compared. It appeared that specific molecular recognition occurred only on the atrazine disulphide sensing layer.