Balancing Panchromatic Absorption and Multistep Charge Separation in a Compact Molecular Architecture.

A panchromatic triad and a charge-separation unit are joined in a crossbar architecture to capture solar energy. The panchromatic-absorber triad (T) is comprised of a central free-base porphyrin that is strongly coupled direct ethyne linkages to two perylene-monoimide (PMI) groups. The charge-separation unit incorporates a free-base or zinc chlorin (C or ZnC) as a hole acceptor (or electron donor) and a perylene-diimide (PDI) as an electron acceptor, both attached to the porphyrin diphenylethyne linkers.

Linking optical spectra to free charges in donor/acceptor heterojunctions: cross-correlation of transient microwave and optical spectroscopy.

The primary photoexcited species in excitonic semiconductors is a bound electron-hole pair, or exciton. An important strategy for producing separated electrons and holes in photoexcited excitonic semiconductors is the use of donor/acceptor heterojunctions, but the degree to which the carriers can escape their mutual Coulomb attraction is still debated for many systems. Here, we employ a combined pump-probe ultrafast transient absorption (TA) spectroscopy and time-resolved microwave conductivity (TRMC) study on a suite of model excitonic heterojunctions consisting of mono-chiral semiconducting single-walled carbon nanotube (s-SWCNT) electron donors and small-molecule electron acceptors.

Effect of nanotube coupling on exciton transport in polymer-free monochiral semiconducting carbon nanotube networks.

Semiconducting single-walled carbon nanotubes (s-SWCNTs) are attractive light-harvesting components for solar photoconversion schemes and architectures, and selective polymer extraction has emerged as a powerful route to obtain highly pure s-SWCNT samples for electronic applications. Here we demonstrate a novel method for producing electronically coupled thin films of near-monochiral s-SWCNTs without wrapping polymer. Detailed steady-state and transient optical studies on such samples provide new insights into the role of the wrapping polymer on controlling intra-bundle nanotube-nanotube interactions and exciton energy transfer within and between bundles.

Conductivity Tuning via Doping with Electron Donating and Withdrawing Molecules in Perovskite CsPbI Nanocrystal Films.

Doping of semiconductors enables fine control over the excess charge carriers, and thus the overall electronic properties, crucial to many technologies. Controlled doping in lead-halide perovskite semiconductors has thus far proven to be difficult. However, lower dimensional perovskites such as nanocrystals, with their high surface-area-to-volume ratio, are particularly well-suited for doping via ground-state molecular charge transfer.

Origin of Panchromaticity in Multichromophore-Tetrapyrrole Arrays.

Panchromatic absorbers that have robust photophysical properties enable new designs for molecular-based light-harvesting systems. Herein, we report experimental and theoretical studies of the spectral, redox, and excited-state properties of a series of perylene-monoimide-ethyne-porphyrin arrays wherein the number of perylene-monoimide units is stepped from one to four. In the arrays, a profound shift of absorption intensity from the strong violet-blue (B and B ) bands of typical porphyrins into the green, red, and near-infrared (Q and Q ) regions stems from mixing of chromophore and tetrapyrrole molecular orbitals (MOs), which gives multiplets of MOs having electron density spread over the entire array.

Synthesis of arrays containing porphyrin, chlorin, and perylene-imide constituents for panchromatic light-harvesting and charge separation.

Achieving solar light harvesting followed by efficient charge separation and transport is an essential objective of molecular-based artificial photosynthesis. Architectures that afford strong absorption across the near-UV to near-infrared region, namely panchromatic absorptivity, are critically important given the broad spectral distribution of sunlight. A tetrapyrrole-perylene pentad array was synthesized and investigated as a means to integrate panchromatic light harvesting and intramolecular charge separation.

Tuning the Electronic Structure and Properties of Perylene-Porphyrin-Perylene Panchromatic Absorbers.

Light-harvesting architectures that afford strong absorption across the near-ultraviolet to near-infrared region, namely, panchromatic absorptivity, are potentially valuable for capturing the broad spectral distribution of sunlight. One previously reported triad consisting of two perylene monoimides strongly coupled to a free base porphyrin via ethyne linkers (FbT) shows panchromatic absorption together with a porphyrin-like S1 excited state albeit at lower energy than that of a typical monomeric porphyrin. Here, two new porphyrin-bis(perylene) triads have been prepared wherein the porphyrin bears two pentafluorophenyl substituents.

Effects of Strong Electronic Coupling in Chlorin and Bacteriochlorin Dyads.

Achieving tunable, intense near-infrared absorption in molecular architectures with properties suitable for solar light harvesting and biomedical studies is of fundamental interest. Herein, we report the photophysical, redox, and molecular-orbital characteristics of nine hydroporphyrin dyads and associated benchmark monomers that have been designed and synthesized to attain enhanced light harvesting. Each dyad contains two identical hydroporphyrins (chlorin or bacteriochlorin) connected by a linker (ethynyl or butadiynyl) at the macrocycle β-pyrrole (3- or 13-) or meso (15-) positions.

Manufacturing Method for Core-Shell Metal Nanoparticle Structure Having Excellent Oxidation Stability Using Cu@Ag Core-Shell Nanoparticles.

As the development of manufacturing technology for electronic devices, propresses it is necessary to study manufacturing technologies for mass storage, low-volume, improved reliability, and low cost materials for electronic devices used in data communication. The noble metals are the most commonly used raw materials used in such manufacturing. However, the raw materials (Ag, Pt, etc.

Enhanced crystallinity of epitaxial graphene grown on hexagonal SiC surface with molybdenum plate capping.

The crystallinity of epitaxial graphene (EG) grown on a Hexagonal-SiC substrate is found to be enhanced greatly by capping the substrate with a molybdenum plate (Mo-plate) during vacuum annealing. The crystallinity enhancement of EG layer grown with Mo-plate capping is confirmed by the significant change of measured Raman spectra, compared to the spectra for no capping. Mo-plate capping is considered to induce heat accumulation on SiC surface by thermal radiation mirroring and raise Si partial pressure near surface by confining the sublimated Si atoms between SiC substrate and Mo-plate, which would be the essential contributors of crystallinity enhancement.

Strongly conjugated hydroporphyrin dyads: extensive modification of hydroporphyrins' properties by expanding the conjugated system.

We report the synthesis and basic photophysical characterization of strongly conjugated hydroporphyrin (chlorin and bacteriochlorin) dyads. Hydroporphyrins are connected at their respective 13 (β) or 15 (meso) positions by ethynyl or butadiynyl linkers. Synthesis entails a series of palladium-catalyzed reactions, starting from appropriate bromobacteriochlorin or bromochlorin.

Copper nanoparticles incorporated with conducting polymer: effects of copper concentration and surfactants on the stability and conductivity.

Copper nanoparticles are prepared in aqueous solution by reducing copper ions with hydrazine hydrate in the presence of cetyl trimethylammonium bromide (CTAB) and polyvinylpyrrolydone (PVP) as stabilizers. With only CTAB was used as stabilizer, copper nanoparticles are aggregated and partially oxidized to Cu(2)O. When both PVP and CTAB were used, dispersed copper nanoparticles with 56 nm diameter were obtained.

Delivery of interleukin-18 gene to lung cancer cells using cationic emulsion.

Interleukin-18 (IL-18) is known to reduce melanoma lung metastases through various mechanisms. For the delivery of IL-18 gene into the lung, three different cationic emulsions as non-viral vectors were formulated using the same components of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), 1,2-dioleoyl-sn-glycero-3-trimethylammonium propane (DOTAP), and Tween 80 with distinct oils. By using the small particle size of physicochemically stable E3, the complex of E3/plasmid DNA encoding IL-18 (16:2.

Cervical myelopathy secondary to atlas hypoplasia - reports of 3 adult cases -.

There have been paucity of reports on atlas hypoplasia, and as a result this condition is not clearly defined, nor well understood. The authors reported three cases of atlas hypoplasia that were found in adults who presented with myelopathic symptoms. On radiographic examination, it was found that the anterior-posterior diameter of the atlas was remarkably narrower in all three cases in comparison with normal persons.