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2007). Recently, Yüksel and co-workers reported plasmonic arrays of enzymatically generated Ag NPs (Yüksel et al. 2015). First, a DNA strand was spotted onto the planar glass surface in an ordered array layout. Second, a streptavidin-horseradish peroxidase complex was bound to the immobilized DNA. Finally, the deposition of “desert-rose like” Ag NPs was catalyzed by horseradish peroxidase via a redox reaction. In this catalytic process, an oxygen atom was detached from hydrogen peroxide and bound to the prostethicheme group of the enzyme causing a change of the iron oxidization state.

This technique is known as oblique (or glancing) angle vapour deposition (OAD or GLAD). Scheme of OAD procedure and SEM image of such typical structure are shown in Fig. 8. The deposition angle determines the length of the nanostructures growing on the substrate. For example, if the substrate is rotated to a specific angle such that the vapour from the metal source is incident on the substrate to the glancing angle, long preferentially cylindrical NRs growth on the surface. Typical parameters of such substrates are: NR lengths of *800–900 nm, diameters *80–90 nm, tilt angles of *71° with respect to the surface normal, NR densities of 15–25 per µm2, average spacing between rods *150 nm, EF *108 (Driskell et al.

A very close spacing between particles is beneficial for the generation of extremely strong EFs (108–1011). 2 SERS EFs 27 Fig. 4 EFs of SERS. a EF calculated for dimer of two spheres and for the corresponding isolated single Ag NP (90 nm diameter). 5 nm with vertical polarization. The colour scale is logarithmic and EFs outside the range 100–108 are shown in dark blue and dark red, respectively (adapted with permission from Xu et al. 2000. Copyright 2000 The American Physical Society). b Long-tail probability distribution of EFs in SERS (reproduced with permission from Blackie et al.