Individual single-walled carbon nanotubes (SWNTs) have been suspended in aqueous media using various anionic, cationic, nonionic surfactants and polymers. The surfactants are compared with respect to their ability to suspend individual SWNTs and the quality of the absorption and fluorescence spectra. For the ionic surfactants, sodium dodecylbenzene sulfonate (SDBS) gives the most well resolved spectral features. For the nonionic systems, surfactants with higher molecular weight suspend more SWNT material and have more pronounced spectral features.

http://dns2.asia.edu.tw/~ysho/YSHO-English/1000%20WC/PDF/Nan%20Let3,%201379.pdf

Individually suspended single-walled carbon nanotubes in various surfactants

Using a recently described self-assembly process (Bayburt, T. H.; Grinkova, Y. V.; Sligar, S. G. Nano Letters 2002, 2, 853−856), we prepared soluble monodisperse discoidal lipid/protein particles with controlled size and composition, termed Nanodiscs, in which the fragment of dipalmitoylphosphatidylcholine (DPPC) bilayer is surrounded by a helical protein belt. We have customized the size of these particles by changing the length of the amphipathic helical part of this belt, termed membrane scaffold protein (MSP). Herein we describe the design of extended and truncated MSPs, the optimization of self-assembly for each of these proteins, and the structure and composition of the resulting Nanodiscs. We show that the length of the protein helix surrounding the lipid part of a Nanodisc determines the particle diameter, as measured by HPLC and small-angle X-ray scattering (SAXS). Using different scaffold proteins, we obtained Nanodiscs with the average size from 9.5 to 12.8 nm with a very narrow size distributi...

Directed self-assembly of monodisperse phospholipid bilayer Nanodiscs with controlled size.

Heterogeneous gold-based catalysis for green chemistry: low-temperature CO oxidation and propene oxidation.

The energy decomposition analysis (EDA) is a powerful method for a quantitative interpretation of chemical bonds in terms of three major components. The instantaneous interaction energy ΔEint between two fragments A and B in a molecule A–B is partitioned in three terms, namely (1) the quasiclassical electrostatic interaction ΔEelstat between the fragments; (2) the repulsive exchange (Pauli) interaction ΔEPauli between electrons of the two fragments having the same spin, and (3) the orbital (covalent) interaction ΔEorb which comes from the orbital relaxation and the orbital mixing between the fragments. The latter term can be decomposed into contributions of orbitals with different symmetry which makes it possible to distinguish between σ, π, and δ bonding. After a short introduction into the theoretical background of the EDA we present illustrative examples of main group and transition metal chemistry. The results show that the EDA terms can be interpreted in chemically meaningful way thus providing a bridge between quantum chemical calculations and heuristic bonding models of traditional chemistry. The extension to the EDA–Natural Orbitals for Chemical Valence (NOCV) method makes it possible to breakdown the orbital term ΔEorb into pairwise orbital contributions of the interacting fragments. The method provides a bridge between MO correlations diagrams and pairwise orbital interactions, which have been shown in the past to correlate with the structures and reactivities of molecules. There is a link between frontier orbital theory and orbital symmetry rules and the quantitative charge- and energy partitioning scheme that is provided by the EDA–NOCV terms. The strength of the pairwise orbital interactions can quantitatively be estimated and the associated change in the electronic structure can be visualized by plotting the deformation densities.

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Energy decomposition analysis

The three main strategies for dispersing carbon nanotubes (NTs) into a polymer matrix to get conductive nanocomposites are described, and illustrated with some appealing examples. The direct mixing of the NTs and the polymer is the ‘simplest' concept to achieve this goal. Other approaches concern the modification of either the polymer matrix or the NT walls in order to improve the wetting of the filler with the matrix material, and thus promote the incorporation of the NTs into the polymer matrix. Most promising results seem to be obtained upon the addition of a third component. The basic concept is the generation of a stable colloidal system containing both a suspension of NTs stabilized by surfactant molecules in water, and polymer latex. After removal of the water, the resulting powder can be processed into the desired shape. This versatile and environmentally benign concept offers low percolation thresholds and relatively high conductivity levels.

Toolbox for Dispersing Carbon Nanotubes into Polymers To Get Conductive Nanocomposites

The [As@Ni12@As20]3– ion was prepared from As73– and Ni(COD)2 in ethylenediamine solutions and isolated as the Bu4P+ salt (As, arsenic; Ni, nickel; COD, cyclooctadiene; Bu, butyl; P, phosphorus). The anion contains an icosahedral [Ni12(μ12-As)]3– fragment that resides at the center of an As20 dodecahedral (fullerene) cage to give an onion-skin–like [As@Ni12@As20]3– cluster with Ih point symmetry. The icosahedron and pentagonal dodecahedron are reciprocal platonic solids, and the 32 surface atoms form a dimpled geodesic sphere composed of 60 triangular faces. In the gas phase, the [As@Ni12@As20]3– ion sequentiallyloses all 21 As atoms to form a series of Ni12As21–x clusters where 0 ≤ x ≤ 21, inclusively.

https://science.sciencemag.org/content/sci/300/5620/778.full.pdf

Interpenetrating As20 fullerene and Ni12 icosahedra in the onion-skin [As@Ni12@As20]3- ion.

Ethylenediamine (en) solutions of K4Pb9 react with toluene solutions of ML4 (M = Pt, Pd, L = PPh3; M = Ni, L2 = COD) and 2,2,2-crypt to give M@Pb122- cluster anions (M = Pt (1), Pd (2), Ni (3)) as the [K(2,2,2-crypt)]+ salts in low (Ni) to good (Pt) yields. The ions have near perfect Ih point symmetry and have been characterized by X-ray diffraction, 207Pb NMR and LDI-TOF mass spectrometry studies. For M = Ni, the primary product formed is the D4d Ni@Pb102- cluster that has also been structurally characterized. The M@Pb102- clusters (M = Pd, Pt) and the new Zintl ions closo-Pb102- and closo-Pb122- were formed in the gas phase but have not been detected in solution or the solid state. The structural trends of these series of clusters have been investigated through DFT calculations. The Ni@Pb102- cluster is dynamic on the 207Pb NMR time scale at −45 °C and 104.7 MHz. The M@Pb122- ions show unusually deshielded 207Pb NMR chemical shifts that presumably arise from σ-aromatic effects associated with their high...

The Pb122- and Pb102- Zintl Ions and the M@Pb122- and M@Pb102- Cluster Series Where M = Ni, Pd, Pt

[Pt@Pb12]2−

The closo-Pb102− Zintl ion in the [Ni@Pb10]2− cluster

The closo-[Sn 9 M(CO) 3 ] 4 - ions where M = Cr (1), Mo (2), W (3) were prepared from [LM(CO) 3 ] precursors (L = mesitylene, cycloheptatriene), K 4 Sn 9 , and 2,2,2-cryptand in ethylenediamine/toluene solvent mixtures. The [K(2,2,2-cryptand)] + salts are very air and moisture sensitive and have been characterized by IR, 1 1 9 Sn, and 1 3 C NMR spectroscopy and single-crystal X-ray diffraction studies. Complexes 1- 3 form bicapped square-antiprismatic 10-vertex 22-electron closo structures in which the [M(CO) 3 ] units occupy cluster vertices. For 1 and 2, the clusters have C 4 v symmetry in the solid state in which the {M(CO) 3 } fragments occupy capping positions with Sn 9 4 ions that are bound to the metal in an η 4 fashion. For 3, the {M(CO) 3 } fragment occupies a position in the square plane with an η 5 -Sn 9 4 - ion and C s point symmetry. For 1-3, a dynamic equilibrium exists between the η 4 and η 5 structures yielding three 1 1 9 Sn NMR signals that reflect the three chemically distinct Sn environments of the higher symmetry C 4 v structure. The 1 1 9 Sn NMR chemical shifts and coupling constants show solvent and temperature dependencies due to the equilibrium process. A triangular-face rotation mechanism is proposed to describe the dynamic behavior.

Bryan Eichhorn

Papers

Interpenetrating As20 fullerene and Ni12 icosahedra in the onion-skin [As@Ni12@As20]3- ion.

The Pb122- and Pb102- Zintl Ions and the M@Pb122- and M@Pb102- Cluster Series Where M = Ni, Pd, Pt

[Pt@Pb12]2−

The closo-Pb102− Zintl ion in the [Ni@Pb10]2− cluster

The closo-[Sn9M(CO)3]4− Zintl Ion Clusters where M=Cr, Mo, W: Two Structural Isomers and Their Dynamic Behavior