In the higher frequency region from 2700 cm -1 to 3600 cm -1 , the ν s (CH 2 ) at 2860 cm -1 , ν as (CH 2 ) at 2930 cm -1 , ν as (CH 3 ) at 2960 cm -1 on Au(111)/C9t, Au(111)/PEG-C9t and Au(111)/(PEG-C9t)+ S protein are observed since DNA, PEG as well as proteins contain aliphatic chains. A very mild broad absorption around 3075 cm -1 is assigned to unsaturated CH stretching vibrations ν(C ar -H) that appears stronger on Au(111)/PEG-C9t and Au(111)/(PEG-C9t)+ S protein. Overall the IRRAS spectra indicate that the ss-DNA is attached to the gold interface and that the PEG blocking does have a strong influence on the sample structure. However, a spectroscopic examination of the nano-scale domain is not possible with this macroscopic method. Thus in the next step, the sensor fabrication is studied by nano-IR spectroscopy.