Hexagonal arrays of plasmonic gold nanopyramids on flexible substrates for surface-enhanced Raman scattering

Surface-enhanced Raman scattering (SERS) with pyramidal nanostructures increases the signal of Raman active analytes, since hotspots form at the edges and tip of a nano-pyramid under illumination. 2D hexagonal arrays of pyramidal nanostructures with a quadratic base are fabricated through cost-effective nano-sphere lithography and transferred onto elastomeric polydimethylsiloxane (PDMS). By making use of the {111} crystal plane of a silicon (100) wafer, an inverted pyramidal array is etched, which serves as the complementary negative for the gold nanostructures. Either a continuous gold thin-film with protruding pyramids or separate isolated nano-pyramids are produced. Three main fabrication strategies are presented, in which a linker molecule between the PDMS and the gold is mandatory to increase the weak Au-PDMS adhesion. 3-Mercaptopropyltriethoxysilane (MPTS) is able to bind to both PDMS and to the gold structures, thus strongly increasing stability under mechanical strain. The SERS enhancement is verified by Raman mapping of 4-mercaptobenzoic acid (4-MBA) molecules. Fabrication on a flexible substrate paves the way for future applications on curved surfaces or insitu tunable resonances.

Electrical Conductivity Study of the Adsorbate-Induced Si(111) Surface Reconstructions after C60 Adsorption

Electrical conductance of Si(111)6×6-Tl and Si(111)β√3×√3-Bi surfaces has been monitored in the course of fullerenes deposition. It has been found that dependence of surface conductivity on the adsorbed C60 dose can be understood in terms of charge transfer induced by interaction of fullerene molecules and substrate which can be explained by the acceptor-like behavior of fullerenes. For the Si(111)6×6-Tl surface decreasing of conductance is connected with depletion of metallic bands of the Tl double layer. For the Si(111)β√3×√3-Bi surface the conductivity is almost unchanged with C60 dose, but due to the fact that C60 layer on this surface form close-packed hexagonal arrays in the layer-by-layer mode, it can be used as a template for alkali-induced ultra-thin fulleride formation.

Hexagonal array formation by intermolecular halogen bonding using a binary blend of linear building blocks: STM study

A bicomponent blend of linear building blocks leads to intermolecular halogen bonding, resulting in the formation of hexagonal arrays.