Niepelt et al. Nanoscale Research Letters 2011, 6:511 http://www.nanoscalereslett.com/content/6/1/511 Page 3 of 7 Figure 1 Schematic view of the biofunctionalization of ZnO. In a toluene environment, (a) the bifunctional GOPS molecule is attached to the ZnO nanowire surface. In a second step, (b) the oligonucleotide is linked to the epoxy group of the GOPS [6]. major distribution to the nanowire intensity fluctuations to the thickness variations along the wire axis. To con- firm this estimation, we also functionalized a single crys- talline ZnO bulk sample and investigated the DNA surface coverage. The sample is showing a homogeneous fluorescence of the functionalized area (not shown here, see Additional file 1), underlining that the GOPS Table 1 DNA sequence and fluorescence markers of the oligonucleotides used for the ZnO nanowire biofunctionalization 5’-Modification Sequence from 5’-3’ 3’-Modification C6-aminolink TCT TAG TTC CTC GTG TAC GAC TTT TTT C6-aminolink TCT TAG TTC CTC GTG TAC GAC TTT TTT FITC Cy3 treatment is applicable for the successful accumulation of DNA monolayer to ZnO surfaces. The observed thickness variations might result from furnace-related instabilities of the growth conditions. With a scaled-up and improved setup, it is possible to overcome this issue easily [20]. However, it is possible that due to the uneven nano- wire surface of the samples, a uniform coverage of the nanowire with DNA molecules might be hampered. Nanowires sticking together during the silanization pro- cess could also lead to a non-uniform DNA coverage. Additionally, damages of the DNA layer during the imprint could result in the same layer inhomogeneity. Nanowires grown from a seed array [20] could be used to avoid non-uniform coverage due to shadowing effects and facilitate a non-destructive nanowire imprint pro- cess. Therefore, the intensity fluctuations of the