Solution behavior of poly(styrene)-block-poly(2-vinylpyridine micelles containing gold nanoparticles

Formation and structural transformation of inverse poly(styrene)-block-poly(2-vinylpyridine) micelles whose polyvinylpyridine core was loaded with HAuCl4 or with elementary gold nanoclusters was studied by combined static and dynamic light scattering. A transformation in the morphology from spherical particles (small Rg/Rh ratio) to large anisomeric objects (large Rg/Rh ratio) was observed by decreasing the concentration of the block copolymer below the critical micelle concentration. At this point, the polymer chains are molecularly dispersed and no longer able to prevent uncontrolled growth of the gold nanoclusters

A combined top-down/bottom-up approach to the microscopic localization of metallic nanodots

Periodic and aperiodic two-dimensional nanostructures with hierarchical order have been prepared by a combined top–down/bottom–up approach. This method allows 7 nm nanoparticles to be positioned with a accuracy of 10 nm or less, with a separation distance of several micrometers. The Figure is an optical dark field microscopy image of a square arrangement of Au dots on a Si wafer

Going to university in England between the wars: access and funding

The creation. coherent manipulation, and measurement of spills in nanostructures open up completely new possibilities for electronics and information processing, among them quantum computing and quantum communication. We review our results on using electron spills in quantum confirmed structures as qubits and present the recently proposed schemes for using a single quantum dot as spin-filter and spin-memory (read-out) device

Ordered deposition of inorganic clusters from micellar block copolymer films

A method is presented for generating quasiregular arrays of nanometer-sized noble metal and metal oxide clusters on flat substrates by the use of a polymer template. The approach is of general applicability to other metals and various oxides. In the first step, polymeric micelles with a polar core were generated by dissolution of poly(styrene)-block-poly(2-vinylpyridine) in toluene. These micelles were used as nanocompartments that were loaded with a defined amount of a metal precursor. The metal ions can be reduced in such a way that exactly one elemental or oxidic particle is formed in each micelle, where each particle is of equal size. By dipping a flat substrate into a dilute solution, a monolayer of the micelles was obtained whereby the embedded equally large particles became arranged in a mesoscopic quasihexagonal two-dimensional (2-D) lattice. Exposure to an oxygen plasma allowed removal of the polymer completely, leaving the naked metal particles firmly attached to the substrate in the same quasihexagonal order as in the monomicellar film. A modified procedure in which the precursor salt was not reduced before the plasma treatment yielded clusters of identical size and in the same 2-D order. The size (height) of the clusters could be varied between 1 and 15 nm depending on the concentration of the metal salt. The interparticle distance could be varied between 30 and 140 nm by using block copolymers with different lengths of the blocks. Such lattices of Au particles have been used to bind streptavidin proteins in an ordered array

Order-disorder transition in surface-induced nanopattern of diblock copolymer films

Formation of surface-induced nanopattern (SINPAT) in ultrathin diblock copolymer films is studied by scanning force microscopy and Monte Carlo simulation. The pattern is caused by strong adsorption of one of the two blocks forming a quasi-two-dimensional coil while the other block dewets this adsorption layer. Scanning force microscopy allowed to observe an order−disorder transition for a SINPAT film of polystyrene-block-poly(2-vinylpyridine) on mica when the length of the dewetting polystyrene block was varied. The experimental data are compared with the Monte Carlo simulations which demonstrate how the pattern formation depends on the degree of polymerization of the dewetting block and the unfavorable interaction potential between the different components

Modulating the Electronic and Solid-State Structure of Organic Semiconductors by Site-Specific Substitution: The Case of Tetrafluoropentacenes

The properties as well as solid-state structures, singlet fission, and organic field-effect transistor (OFET) performance of three tetrafluoropentacenes (1,4,8,11: 10, 1,4,9,10: 11, 2,3,9,10: 12) are compared herein. The novel compounds 10 and 11 were synthesized in high purity from the corresponding 6,13-etheno-bridged precursors by reaction with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate at elevated temperatures. Although most of the molecular properties of the compounds are similar, their chemical reactivity and crystal structures differ considerably. Isomer 10 undergoes the orbital symmetry forbidden thermal [4+4] dimerization, whereas 11 and 12 are much less reactive. The isomers 11 and 12 crystallize in a herringbone motif, but 10 prefers π–π stacking. Although the energy of the first electric dipole-allowed optical transition varies only within 370 cm−1 (0.05 eV) for the neutral compounds, this amounts to roughly 1600 cm−1 (0.20 eV) for radical cations and 1300 cm−1 (0.16 eV) for dications. Transient spectroscopy of films of 11 and 12 reveals singlet-fission time constants (91±11, 73±3 fs, respectively) that are shorter than for pentacene (112±9 fs). OFET devices constructed from 11 and 12 show close to ideal thin-film transistor (TFT) characteristics with electron mobilities of 2×10−3 and 6×10−2 cm2 V−1 s−1, respectively