Showing papers by "Alison M. Funston published in 2018"
TL;DR: In this article, the authors investigate the transformation of single crystal gold nanorod surface morphology over extended growth times, showing that the surface morphology transitions from faceted to curved, consistent with the primary control of the AgNO3 over aspect ratio occurring at the symmetry breaking point.
18 citations
TL;DR: This work proposes an alternative approach to construct multiple, structurally different, nanoparticle assemblies from just a few complementary nanoparticle-functionalised DNA strands, and exploits local minima in the potential energy landscape of hybridised nanoparticles-DNA structures by employing kinetic control of the assembly.
Abstract: Developments in DNA nanotechnology offer control of the self-assembly of materials into discrete nanostructures. Within this paradigm, pre-assembled DNA origami with hundreds of DNA strands allows for precise and programmable spatial positioning of functionalised nanoparticles. We propose an alternative approach to construct multiple, structurally different, nanoparticle assemblies from just a few complementary nanoparticle-functionalised DNA strands. The approach exploits local minima in the potential energy landscape of hybridised nanoparticle-DNA structures by employing kinetic control of the assembly. Using a four-strand DNA template, we synthesise five different 3D gold nanoparticle (plasmonic) tetrameric isomers, akin to molecular structural isomers. The number of different structures formed using this approach for a set of DNA strands represents a combinatorial library, which we summarise in a hybridisation pathway tree and use to achieve deposition of tetrahedral assemblies onto substrates in high yield. The ability to program nanoparticle self-assembly pathways gives unprecedented access to unique plasmonic nanostructures.
10 citations
TL;DR: The results with anions provide clear evidence for carborane conjugation that might be exploited in molecular wire materials, which are classically composed of all π-conjugated molecules.
Abstract: Optical electron transfer (intervalence) transitions in radical anions of p-carborane oligomers attest to delocalization of electrons between two p-carboranes cages or a p-carborane and a phenyl ring. Oligomers of the 12 vertex p-carborane (C2B10H12) cage, [12], with up to 3 cages were synthesized, as well as p-carboranes with one or two trimethylsilylphenyl groups, [6], attached to the carbon termini. Pulse radiolysis in tetrahydrofuran produced radical anions, determined redox potentials by equilibria and measured their absorption spectra. Density functional theory computations provided critical insight into the optical electron transfer bands and electron delocalization. One case, [6–12–6], showed both Robin–Day class II and III transitions. The class III transition resulted from a fully delocalized excess electron across both benzene rings and the central p-carborane, with an electronic coupling Hab = 0.46 eV between the cage and either benzene. This unprecedented finding shows that p-carborane bridge...
9 citations
TL;DR: The three-dimensional morphological control of the individual metallic nanocrystals in a coupled structure imposes an electric field localization and enhancement in all three dimensions as discussed by the authors, which can be exploited to exploit the properties of the three dimensions.
Abstract: The three-dimensional morphological control of the individual metallic nanocrystals in a coupled structure imposes an electric field localization and enhancement in all three dimensions. We exploit...
8 citations
TL;DR: TheNear-field optical properties of mesoscale crystalline gold plates were examined using near-field scanning optical microscopy with a focus on the effects of modifying morphology and excitation conditions.
Abstract: Meso-scale plasmons are supported by structures with dimensions on the order of tens of plasmon wavelengths. Metal structures at this length-scale are promising for the design and engineering of structures to direct the flow of optical energy and generate high intensity, localized electric fields. The near-field optical properties of mesoscale crystalline gold plates were examined using near-field scanning optical microscopy with a focus on the effects of modifying morphology and excitation conditions. Excitation of surface plasmon polaritons (SPPs) at plate edges and their subsequent propagation and interference as radial waves across the surface results in nodes of enhancement of the near-field on the plate surface at specific positions within the plate. The spatial position of the near-field enhancement may be directed by controlling either, or both, the boundary conditions (plate shape) and polarization of the excitation light.
6 citations
TL;DR: In this paper, the lateral assembly of gold nanorods into arrays, which leads to strong color changes due to surface plasmon coupling, was studied, and the first example of gap modes in colloid systems, an optical mode in which light waves propagate in the channels between the gold rods, were demonstrated.
Abstract: The assembly of metal nanocrystals offers a flexible method for creating new materials with tunable, size-dependent optical properties. Here we study the lateral assembly of gold nanorods into arrays, which leads to strong colour changes due to surface plasmon coupling. We also demonstrate the first example of gap modes in colloid systems, an optical mode in which light waves propagate in the channels between the gold rods. Such modes resonate at wavelengths which strongly depend on the gap width and length.
5 citations