Widely Varying Kondo and Magnetic Interactions in Molecule Gold Nanostructured Materials by Changing the Gold Nanoarchitecture.

Delocalized-localized electron interactions are central to strongly correlated electron phenomena. Here, we study the Kondo effect, a prototypical strongly correlated phenomena, in a tunable fashion using gold nanostructures (nanoparticle, NP, and nanoshell, NS) + molecule cross-linkers (butanedithiol, BDT). NP films exhibit hallmark signatures of the Kondo effect, including (1) a log temperature resistance upturn as temperature decreases in a metallic regime, and (2) zero-bias conductance peaks (ZBCPs) that are well fit by a Frota function near a percolation insulator transition, previously used to model Kondo peaks observed using tunnel junctions.

Visible Out-of-plane Polarized Luminescence and Electronic Resonance in Black Phosphorus.

Black phosphorus (BP) is unique among layered materials because of its homonuclear lattice and strong structural anisotropy. While recent investigations on few-layer BP have extensively explored the in-plane (, ) anisotropy, much less attention has been given to the out-of-plane direction (). Here, the optical response from bulk BP is probed using polarization-resolved photoluminescence (PL), photoluminescence excitation (PLE), and resonant Raman scattering along the zigzag, out-of-plane, and armchair directions.

Graphene field-effect transistors as bioanalytical sensors: design, operation and performance.

Graphene field-effect transistors (GFETs) are emerging as bioanalytical sensors, in which their responsive electrical conductance is used to perform quantitative analyses of biologically-relevant molecules such as DNA, proteins, ions and small molecules. This review provides a detailed evaluation of reported approaches in the design, operation and performance assessment of GFET biosensors. We first dissect key design elements of these devices, along with most common approaches for their fabrication.

Large Kondo effect in assemblies of Au nanoparticles linked with alkanedithiol electron bridges.

Using a prototypical nanoparticle-molecule assembly, namely alkanedithiol-linked gold nanoparticle films, we observe hallmark signatures of the Kondo effect in conductance vs. voltage as well as temperature measurements. Its contribution to temperature dependence of conductance is much larger than those from all other temperature-dependant effects up to 300 K by >20-fold - much larger than previous reports of the Kondo effect using other platforms.

Controlled hierarchical assembly of gold nanoparticles in macroscopic films: from densely packed monolayers to networks of micropores and nanobundles.

The present study demonstrates the ability of excess, weakly amphiphilic n-alkanethiols (n = 4, 12, 18) and solvent composition to tune through a wide range of large-scale, macroscopic architectures formed by alkanethiol-capped Au nanoparticles (NPs). Both the alkanethiols and NPs are significantly hydrophobic species and compete for surface area at an air-water interface. When solutions of the two species are spread on a large (50 cm) water surface in a Teflon well, a thin film forms and exhibits co-existing macroscopic regions with various distinct NP self-assembled architectures, namely a close packed monolayer, a network phase characterized by micron-sized pores (micropores) surrounded by quasi-linear bundles of nanoparticles, and finally aggregates.

Influence of low energy barrier contact resistance in charge transport measurements of gold nanoparticle+dithiol-based self-assembled films.

Gold-thiol self-assembly is a widely employed strategy for engineering electronic devices using molecules and other nanostructures as building blocks. However, device behavior is expected to be governed by both building block architecture and contact effects. In order to elucidate the role of the latter in such devices, we have studied conductance of n-butanedithiol-linked Au nanoparticle (NP) films using different types of electrode configurations, namely, four-probe versus two-probe and break junctions before versus after dielectric break down of contact resistance.