Nanostructured gold surfaces as reproducible substrates for surface‐enhanced Raman spectroscopy

Abstract

Raman spectroscopy is a common tool for the qualitative and quantitative chemical analysis of molecules. Although the unique identification of molecules is possible via their vibrational lines, high concentrations (mmol/l) are needed for their nonresonant excitation owing to their low scattering cross section. The intensity of the Raman spectra is amplified by the use of the surface-enhanced Raman scattering (SERS) technique. While the use of silver sols results only in a limited reproducibility of the Raman line intensities, lithographically designed, nanostructured gold surfaces used as SERS-active substrates should, in principle, combine the high sensitivity with better reproducibility. For this purpose, we have produced gratings of gold dots on Si(001) surfaces by means of electron beam lithography. Qualitative and quantitative investigations of crystal violet (CV) performed using nanostructured surfaces give high reproducibility and enhancement of the Raman lines. The substrates are reusable after cleaning; all results presented could be obtained from a single SERS substrate. For the experiments very low laser powers were used.

Probing Innovative Microfabricated Substrates for their Reproducible SERS Activity

“…Therefore gold nanodot arrays are the most common reproducible SERS-active substrates produced by electron beam lithography, as described in the literature. [24,27] We use the electron backscatter effect differently. Instead of writing the sharp-edged structures in a straight line, we exposed dense arrays of round holes.…”

“…[32,33] However, sufficient reproducibility of the pattern generation is rather complicated due to the formation of non-reproducible multilayers or distorted monolayers of beads, thus preventing the ideal mask geometry over a large scaled area of several tens of square microns. As our goal was the preparation of SERS arrays across a few hundred square microns, we therefore chose electron beam lithography, a common method for preparing reproducible SERS arrays, [24][25][26][27] which furthermore permits a later transfer to nanoimprint techniques.…”

“…Electron beam lithography is known to yield reproducible SERS-active substrates. [24][25][26][27] However, so far mostly gold nanodot arrays with dot-distances of at least 50 nm were used as SERS substrates. The requirements for SERS-active substrates exhibiting high enhancement factors are sharp or needle-like edge features with distances of only a few nanometers (less than 10 nm) between the nanostructures.…”

Nanoparticles and Nanostructures for Biophotonic Applications

“…The characteristic vibrational bands of CV are observed in the SERS spectrum (CV NP trace). Intense Raman bands centered at around 591, 882, 927 and 1189 cm -1 can be attributed to the N-H 2 rocking vibration, two benzene group bending, out-of phase N-H 2 rocking vibration, and combination of N-H 2 rocking and C-H X rocking, respectively (Vogel, 2000;Sackmann et al, 2007). CV molecules chemisorbed over a flat Au film are also shown in Fig.12c.…”

SERS Study of Tetrodotoxin (TTX) by Using Silver Nanoparticle Arrays

“…Several kinds of substrate including island film, nanoparticles, and lithographic surface can provide rough metallic surface. There are many techniques available to fabricate nanoparticles [17], such as electron-beam lithography [18,19], dip-pen nanolithography [20], and nanosphere lithography (NSL) [21][22][23]. Among these techniques, NSL has several advantages including the capability of fabricating many different substrates at fast speed and at low cost.…”