Alexander Finnemore

Metal oxide nanoparticles (MONPs) have widespread usage across many disciplines, but monitoring molecular processes at their surfaces in situ has not been possible. Here we demonstrate that MONPs give highly enhanced (×10(4)) Raman scattering signals from molecules at the interface permitting direct monitoring of their reactions, when placed on top of flat metallic surfaces. Experiments with different metal oxide materials and molecules indicate that the enhancement is generic and operates at the single nanoparticle level. Simulations confirm that the amplification is principally electromagnetic and is a result of optical modulation of the underlying plasmonic metallic surface by MONPs, which act as scattering antennae and couple light into the confined region sandwiched by the underlying surface. Because of additional functionalities of metal oxides as magnetic, photoelectrochemical and catalytic materials, enhanced Raman scattering mediated by MONPs opens up significant opportunities in fundamental science, allowing direct tracking and understanding of application-specific transformations at such interfaces. We show a first example by monitoring the MONP-assisted photocatalytic decomposition reaction of an organic dye by individual nanoparticles.

Gyroid-structured calcite crystals are grown by templating though self-assembled copolymer films. The remarkable triply periodic minimal surface is perfectly replicated on the nanometer scale, while single crystallinity is maintained. This is a wholly synthetic route to a crystal morphology found in biological systems, only on a smaller length scale.

Templating against atomically flat materials allows creation of smooth metallic surfaces. The process of adding the backing (superstrate) to the deposited metals has proven to be the most difficult part in producing reliable, large-area, solvent-resistant substrates and has been the subject of recent research. In this paper we describe a simple and inexpensive liquid glass template-stripping (lgTS) method for the fabrication of large area ultraflat gold surfaces. Using our lgTS method, ultraflat gold surfaces with normals aligned along the <111> crystal plane and with a root-mean-square roughness of 0.275 nm (over 1 μm(2)) were created. The surfaces are fabricated on silica-based substrates which are highly solvent resistant and electrically insulating using silicate precursor solution (commonly known as "liquid glass") and concomitant mild heat treatment. We demonstrate the capabilities of such ultraflat gold surfaces by imaging nanoscale objects on top and fabricating microelectrodes as an example application. Because of the simplicity and versatility of the fabrication process, lgTS will have wide-ranging application in imaging, catalysis, electrochemistry, and surface science.