Temperature dependence of a1 and b2 type modes in the surface enhanced Raman from 4-Aminobenzenethiol

Dichalcogenide and Metal Oxide Semiconductor-Based Composite to Support Plasmonic Catalysis

Nanocomposites comprising plasmon active metal nanostructures and semiconductors have been used to control the charge states in the metal to support catalytic activity. In this context dichalcogenides when combined with metal oxides offer the potential to control charge states in plasmonic nanomaterials. Using a model plasmonic mediated oxidation reaction p-amino thiophenol ↔ p-nitrophenol, we show that through the introduction of transition metal dichalcogenide nanomaterial, reaction outcomes can be influenced, achieved through controlling the occurrence of the reaction intermediate dimercaptoazobenzene by opening new electron transfer routes in a semiconductor-plasmonic system. This study demonstrates the ability to control plasmonic reactions by carefully controlling the choice of semiconductors.

The influence of molecular mobility on the properties of networks of gold nanoparticles and organic ligands

We prepare and investigate two-dimensional (2D) single-layer arrays and multilayered networks of gold nanoparticles derivatized with conjugated hetero-aromatic molecules, i.e., S-(4-{[2,6-bipyrazol-1-yl)pyrid-4-yl]ethynyl}phenyl)thiolate (herein S-BPP), as capping ligands. These structures are fabricated by a combination of self-assembly and microcontact printing techniques, and are characterized by electron microscopy, UV-visible spectroscopy and Raman spectroscopy. Selective binding of the S-BPP molecules to the gold nanoparticles through Au-S bonds is found, with no evidence for the formation of N-Au bonds between the pyridine or pyrazole groups of BPP and the gold surface. Subtle, but significant shifts with temperature of specific Raman S-BPP modes are also observed. We attribute these to dynamic changes in the orientation and/or increased mobility of the molecules on the gold nanoparticle facets. As for their conductance, the temperature-dependence for S-BPP networks differs significantly from standard alkanethiol-capped networks, especially above 220 K. Relating the latter two observations, we propose that dynamic changes in the molecular layers effectively lower the molecular tunnel barrier for BPP-based arrays at higher temperatures.