Employing electrostatic self-assembly of tailored nickel sulfide nanoparticles for quasi-solid-state dye-sensitized solar cells with Pt-free counter electrodes

A low cost, low-temperature processable, highly efficient nickel sulfide counter electrode is demonstrated. Using the tailored, preformed nickel sulfide nanoparticles and electrostatic self-assembly, a novel counter electrode was fabricated that exceeded the efficiency of a conventional Pt-based cell.     

A facile reduction of Eu3+ to Eu2+ in gadolinium monosulfide nanoparticles using a mixed solvent of oleic acid/hexadecylamine

We prepared GdS:Eu(3+) by simple thermal decomposition under 1-dodecanethiol. A reduction process was observed from Eu(3+) to Eu(2+) when oleic acid and hexadecylamine were injected into GdS:Eu(3+). Under UV excitation, GdS:Eu(3+) showed an intense orange-red emission and GdS:Eu(2+) showed a broad green band.     

Generation of sub-micron-sized droplets,by continuous extensional flow

A method is devised to generate sub-micron-sized droplets without surfactants by using a continuous extensional flow. By using the extensional flow judiciously the physical limits on the viscosity ratio of the dispersed and dispersing media could be overcome. The strain hardening behavior of the Boger fluid under the extensional flow gave a synergic effect to generate the smaller droplets. It was shown that the drop size could be decreased to a sub-micron scale and the droplet size distribution was much narrower compared to the case of the conventional shear (stirring) method. This method is also applicable when the two phases are compatible.     

Phorbasones A and B, sesterterpenoids isolated from the marine sponge Phorbas sp. and induction of osteoblast differentiation

Two new sesterterpenoids, phorbasones A (1) and B (2), were isolated from the Korean marine sponge Phorbas sp. Their complete structures were elucidated by spectral data and chemical reactions. Phorbasone A exhibited a positive effect on the calcium deposition activity in C3H10T1/2 cells. The biogenic origin of the core structure is believed to be through a novel rearrangement from the ansellone carbon structure.     

Soft-core potentials in thermodynamic integration: comparing one- and two-step transformations

Molecular dynamics-based free energy calculations allow the determination of a variety of thermodynamic quantities from computer simulations of small molecules. Thermodynamic integration (TI) calculations can suffer from instabilities during the creation or annihilation of particles. This "singularity" problem can be addressed with "soft-core" potential functions which keep pairwise interaction energies finite for all configurations and provide smooth free energy curves. "One-step" transformations, in which electrostatic and van der Waals forces are simultaneously modified, can be simpler and less expensive than "two-step" transformations in which these properties are changed in separate calculations. Here, we study solvation free energies for molecules of different hydrophobicity using both models. We provide recommended values for the two parameters α(LJ) and β(C) controlling the behavior of the soft-core Lennard-Jones and Coulomb potentials and compare one- and two-step transformations with regard to their suitability for numerical integration. For many types of transformations, the one-step procedure offers a convenient and accurate approach to free energy estimates.     

Negative differential resistance in ZnO coated peptide nanotube

We investigate the room temperature electronic transport properties of a zinc oxide (ZnO) coated peptide nanotube contacted with Au electrodes. Current–voltage (I–V) characteristics show asymmetric negative differential resistance (NDR) behavior along with current rectification. The NDR phenomenon is observed in both negative and positive voltage sweep scans, and found to be dependent on the scan rate and humidity. Our results suggest that the NDR is due to protonic conduction arising from water molecule redox reaction on the surface of ZnO coated peptide nanotubes rather than the conventional resonant tunneling mechanism.     

Dispersion of multi-walled carbon nanotubes in PDMS/PB blend

In this study, the sequential dispersion of multi-walled carbon nanotubes (CNTs) in PDMS/PB (polydimethylsiloxane/polybutene) blends and the change of blend morphology by the dispersion of CNTs were investigated by rheological and morphological observations. The dispersion of CNTs into PDMS/PB blend was accomplished by the dilution of the CNT master (2?wt.% CNT in PDMS) in PDMS/PB blend using an extensional mixer. The morphological study shows that under the extensional flow, CNTs in the dispersed CNT master phase are mainly broken up by tip-streaming and the continuous pinching-off of PDMS drops during morphology evolution enhances the dispersion of CNT. It has been shown that CNTs can be disentangled as in the case of dispersing CNTs in a Boger fluid. Rheological data and TEM observations show that it is not simply a mixing of two phases and the CNTs in the master phase can be dispersed in the single CNT level.     

Dynamic simulation of arbitrarily shaped particles in shear flow

A new simulation framework was created for modeling the dynamics of arbitrarily shaped particles dispersed in Newtonian fluid. Theoretical complexity usually restricts suspension simulations to those for spheroids. This new simulation is loosely based on the Stokesian Dynamics method including long range hydrodynamic interaction and uses spheres as building components for greater particulates of arbitrary shape. This approach is capable of accurately reproducing the dynamics of an isolated arbitrarily shaped particle. As verification, the simulated results are compared against known results for a rod-like particle. An elongated rod-shaped structure made from linked spheres is shown to reproduce the well-known elongated ellipsoidal particle dynamics described by [Jeffrey Proc R Soc Lond A 102:161–179, 1923]. The predicted orbital period and spin rates for a fiber in shear are reproduced and compare well with theoretical prediction over a wide aspect ratio range. Predicted particle dynamics for other shaped particles are then demonstrated.