Creation of ordered 3D tubes out of DNA origami lattices.

Hierarchical self-assembly of nanostructures with addressable complexity has been a promising route for realizing novel functional materials. Traditionally, the fabrication of such structures on a large scale has been achievable using top-down methods but with the cost of complexity of the fabrication equipment resolution and limitation mainly to 2D structures. More recently bottom-up methods using molecules like DNA have gained attention due to the advantages of low fabrication costs, high resolution and simplicity in an extension of the methods to the third dimension.

Covalent and non-covalent coupling of a Au nanocluster with a fluorophore: energy transfer, quenching and intracellular pH sensing.

Interactions between an atomically precise gold nanocluster Au(-MBA) (-MBA = mercaptobenzoic acid) and a fluorescent organic dye molecule (KU, azadioxatriangulenium) are studied. In solution, the constituents form spontaneously a weakly bound complex leading to quenching of fluorescence of the KU dye energy transfer. The KU can be separated from the complex by lowering pH, leading to recovery of fluorescence, which forms a basis for an optical reversible pH sensor.

Constructing Large 2D Lattices Out of DNA-Tiles.

The predictable nature of deoxyribonucleic acid (DNA) interactions enables assembly of DNA into almost any arbitrary shape with programmable features of nanometer precision. The recent progress of DNA nanotechnology has allowed production of an even wider gamut of possible shapes with high-yield and error-free assembly processes. Most of these structures are, however, limited in size to a nanometer scale.

Chemically Selective Imaging of Individual Bonds through Scanning Electron Energy-Loss Spectroscopy: Disulfide Bridges Linking Gold Nanoclusters.

As proof-of-principle of chemically selective, spatially resolved imaging of individual bonds, we carry out electron energy-loss spectroscopy in a scanning transmission electron microscopy instrument on atomically precise, thiolate-coated gold nanoclusters linked with 5,5'-bis(mercaptomethyl)-2,2'-bipyridine dithiol ligands. The images allow the identification of bridging disulfide bonds (R-S-S-R) between clusters, and X-ray photoelectron spectra support the finding.

Dithiol-Induced Oligomerization of Thiol-Protected Gold Nanoclusters.

Controlled synthesis of nanostructure oligomers requires detailed understanding of their wet chemistry and the forces driving the polymerization process. In this paper, we report the main factors affecting the reaction yields of a dithiol-induced synthesis of covalently bound nanocluster dimers and oligomers and present a detailed analysis of possible reaction mechanisms. We synthesize the nanocluster oligomers using monodisperse -mercaptobenzoic acid (-MBA)-protected gold nanoclusters with a nominal composition of Au(-MBA) to minimize ensemble effects on size, shape, and surface structure.

Covalently linked multimers of gold nanoclusters Au(p-MBA) and Au(p-MBA).

We present the synthesis, separation, and characterization of covalently-bound multimers of para-mercaptobenzoic acid (p-MBA) protected gold nanoclusters. The multimers were synthesized by performing a ligand-exchange reaction of a pre-characterized Au(p-MBA) nanocluster with biphenyl-4,4'-dithiol (BPDT). The reaction products were separated using gel electrophoresis yielding several distinct bands.