here. An important observation is the broad feature from 1650 cm -1 to 1770 cm -1 which is associated with ν(C --O) of nucleobases in DNA. This band is significantly important to provide insight into the molecular distributions in the final sensor because it is specific to ss-DNA while the blocking agent has no absorbance in this region. Hence, the absorbance maximum of this band was imaged in the following.