**Author details**

fabricated SERS substrates is apparently related to the homogeneous Ag distribution on the

(thermal evaporation method at a high vacuum).

PVD methods (the sputtering technique) provide a strictly controlled, stable distribution of Ag-n on nanotubular titania, thus offering suitable platforms for SERS investigations and for measurements of high-quality SERS spectra. Such spectra were obtained for pyridine, p-mercaptobenzoic acid, rhodamine and rhodamine 6G dye adsorbed on Ag-n-functionalized nanoporous layers of titania. For the SERS measurements (with R6G), excellent spectra were

Stable, reproducible and highly active platforms for SERS investigations were obtained using

The SERS enhancement induced by these new materials is associated primarily with two geometric factors: the specific surface area of the nanotubes, and an appropriate size and distribution of the Ag nanoparticles. These geometric factors (clearly visible using high-resolution microscopy) affect the properties of the metallic "nanoresonators" deposited on the TiO<sup>2</sup> nanotubes. Consequently, the probe molecules sense even slight changes on the surface, and these manifest themselves in the SERS intensity. However, the spectral differences observed result not only from the specific morphology, where the PVD techniques lead to the formation of cavities and slits that operate as adsorbed molecule resonators, but also from a specific

obtained, even for a concentration of R6G in a solution as low as 10−9 mol/l. The EF

specific morphologies that are extremely useful in Raman investigations.

**Figure 12.** SERS spectrum of R6G molecules adsorbed from a 10−9 M aqueous solution on a surface of TiO2

structures; this should make it possible to produce

) for the smallest nanotube diameter (d = 38 ± 9 nm).

nanotubes themselves. The further

value was

NT nanotubes

surface of the regular nanoporous TiO2

**4. Conclusions and outlook**

(25 V) with a silver deposit of 0.05 mg/cm2

50 Raman Spectroscopy

found to be the largest (EF = 2.8 × 106

relatively simple procedures and techniques.

interaction between the Ag nanoparticles and the TiO2

Marcin Pisarek1 \*, Jan Krajczewski2 , Marcin Hołdyński<sup>1</sup> , Tomasz Płociński<sup>3</sup> , Mirosław Krawczyk<sup>1</sup> , Andrzej Kudelski2 and Maria Janik-Czachor1

\*Address all correspondence to: mpisarek@ichf.edu.pl

1 Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland

2 Faculty of Chemistry, University of Warsaw, Warsaw, Poland

3 Faculty of Material Science and Engineering, Warsaw University of Technology, Warsaw, Poland
