We study a crystallographic etching process of graphene nanostructures where zigzag edges can be prepared selectively. The process involves heating exfoliated single-layer graphene samples with a predefined pattern of antidot arrays in an argon atmosphere at 820 • C, which selectively removes carbon atoms located on armchair sites. Atomic force microscopy and scanning electron microscopy cannot resolve the structure on the atomic scale. However, weak localization and Raman measurements -which both probe intervalley scattering at armchair edges -indicate that zigzag regions are enhanced compared to samples prepared with oxygen based reactive ion etching only.

Engineered gold nanostructured arrays with feature separation in the sub-10-nm range were fabricated and used for highly sensitive surface enhanced Raman scattering (SERS) detection of biomarkers. Nanostructuring is achieved by combining electron beam lithography with the so-called shadow evaporation technique which involves a two-step Au vapor deposition through a suspended Ge mask while the substrate is tilted in opposite directions. This results in a regular triangular surface pattern with extremely small gap distances that allow positive enhancement of the local electric fields by enabling improvements in the electromagnetic coupling between adjacent nanoparticles. The resulting SERS active surfaces are suitable for the realization of reference procedures for quantifying marker molecules like urea or creatinine at physiologically relevant concentrations.

Graphene-enhanced Raman scattering (GERS) is emerging as an important method due to the need for highly reproducible, quantifiable, and biocompatible active substrates. As a result of its unique two-dimensional carbon structure, graphene provides particularly large enhanced Raman signals for molecules adsorbed on its surface. In this work, the GERS signals of a test molecule, 4-mercaptobenzoic acid (4-MBA), with reproducible enhancement factors are discussed and compared with surface-enhanced Raman scattering (SERS) signals from highly active substrates, covered with spherical silver nanoparticles. It is shown that chemical interactions between the molecule and graphene can result in a frequency shift in the graphene-enhanced Raman signal of the molecule.

We exploit the near field enhancement of nanoantennas to investigate the Raman spectra of otherwise not optically detectable carbon nanotubes (CNTs). We demonstrate that a top-down fabrication approach is particularly promising when applied to CNTs, owing to the sharp dependence of the scattered intensity on the angle between incident light polarization and CNT axis. In contrast to tip enhancement techniques, our method enables us to control the light polarization in the sample plane, locally amplifying and rotating the incident field and hence optimizing the Raman signal. Such promising features are confirmed by numerical simulations presented here. The relative ease of fabrication and alignment makes this technique suitable for the realization of integrated devices that combine scanning probe, optical, and transport characterization.

We present an on-chip approach for the quantification of biomarkers based on isotope-dilution surface-enhanced Raman scattering (IDSERS). The full procedure was realized on a few square millimetres of a SERS-active substrate, covered with either lithographically engineered gold nanotriangles or silver nanospheres generated by galvanic displacement deposition. The use of certified reference materials combined with the ID principle ensures traceability of the quantitation to SI units. A series of substance spots was deposited onto the SERS active area and measured one by one in fast sequence. The SERS spectra were used to generate and validate a PLS model and also to predict the creatinine concentration of an unknown serum sample.