Poly[(3-hexylthiophene)-block-(3-semifluoroalkylthiophene)] for Polymer Solar Cells

We report the synthesis of poly[(3-hexylthiophene)-block-(3-(4,4,5,5,6,6,7,7,7-nonafluoroheptyl)thiophene)], P(3HT-b-3SFT), carried out by the Grignard Metathesis Method (GRIM). The copolymers composition was determined by (1)H and (19)F NMR spectroscopies, and gel permeation chromatography (GPC). The thin films of P(3HT-b-3SFT) were investigated by ultraviolet-visible absorption spectroscopy and atomic force microscopy (AFM). We also fabricated bulk-hetero junction (BHJ) solar cells based on blends of P(3HT-b-3SFT) and [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM). Although the composition ratio of P3SFT in P(3HT-b-3SFT) was low, the influence of P3SFT on the morphology and properties of solar cells was significant. The annealing process for the BHJ solar cells induced the formation of large domains and led to poor solar cell performance. The BHJ solar cells, based on PCBM and P(3HT-b-3SFT), prepared by the non-annealing process, had a maximum power conversion efficiency of 0.84% under 100 mW/cm(2) (AM 1.5 solar illumination) in air.     

Influence of Microstructure on the Wear Behavior of SiC-Reinforced Titanium-Matrix Composites Lubricated by Water and by Ethanol

Two kinds of SiC-reinforced titanium-matrix composites were slid against themselves in water and in ethanol to evaluate the influence of their microstructure on the wear behavior. The composites had a structure in which the SiC particles were coated with interfacial layers that consisted of Ti₅Si₃C _x and TiC, and the TiC particles were dispersed in a titanium matrix. The wear resistance of the composites was much better than that of titanium metal. The wear of the composites prepared from starting materials with a high SiC content was lower than that with a low SiC content.     

Densification of Nanocrystalline Yttria by Low Temperature Spark Plasma Sintering

We investigated the densification of undoped, nanocrystalline yttria (Y₂O₃) powder by spark plasma sintering (SPS) at sintering temperatures between 650°C and 1050°C at a heating rate of 10°C/min and an applied stress of 83 MPa. In spite of the low sinterability of the undoped Y₂O₃, a remarkable densification of the powder started at about 600°C, and a theoretical density of more than 97% was achieved at a sintering temperature of 850°C with a grain size of about 500 nm. The low temperature SPS is effective for fabricating dense Y₂O₃ polycrystals.     

Dilatometer analysis of sintering behavior of nano-CeO2 particles

Dilatometer analysis was conducted for nano-CeO₂ particles, with varying green densities. Bimodal shrinkage rate was noticed for nano-particles with respect to temperature, while single mode was observed for submicron particles. With decrease in green density, the intensity of the low temperature peak in the bimodal shrinkage rate increased compared with that of high temperature peak. The activation energies of nano-CeO₂ sintering estimated by the master sintering curve were 370 and 440 kJ/mol for temperature ranges near the low temperature peak and near the high temperature peak, respectively, while the activation energy of submicron-CeO₂ sintering was 420 kJ/mol. It was found that the low temperature peak characterized the sintering behavior of nano-CeO₂, and this peak was responsible for the enhancement in the sinterability of green compact with low density.     

Direct length comparison between regular crystalline lattice and SEM standard grating using dual tunneling unit STM

This paper presents a potential image processing method for calibrating the in-plane geometrical distortion of a scanning tunneling microscope (STM) image using a regular crystalline lattice, describes the assessment evaluation of comparative length measurement in the range of about 1 micrometer using a regular crystalline lattice as a reference scale and a dual tunneling unit-STM (DTU-STM) as a detector, and shows the results of direct length comparison between a scanning tunneling microscope (SEM) standard grating, whose pitch is 240 nm, and a regular crystalline lattice using a DTU-STM. The method is based on two-dimensional fast Fourier transform (FFT) analysis. The DTU- STM with one X-Y stage and two tunneling units independently controlled in the Z-axis direction has been utilized for comparative length measurement. To improve the measurement accuracy, the present method is used to process the raw images obtained from the DTU-STM. The results of assessment experiments, in which the cleaved surface of highly oriented pyrolytic graphite (HOPG) is used as a reference scale for measurement of lengths on the order of 1 micrometer, demonstrate the feasibility of the present image processing method and the comparative length measurement with sub-nanometer resolution using the DTU- STM. The value of the SEM standard grating pitch, which obtained from the direct length comparison with HOPG lattice spacing using the DTU-STM, was coincided with the value obtained from the conventional diffraction method within a error of 2 %.     

Adults and Nymphs Do Not Smell the Same: The Different Defensive Compounds of the Giant Mesquite Bug (<Emphasis Type="Italic">Thasus neocalifornicus</Emphasis>: Coreidae)

Heteropteran insects often protect themselves from predators with noxious or toxic compounds, especially when these insects occur in aggregations. The predators of heteropteran insects change from small insect predators to large avian predators over time. Thus, a chemical that is deterrent to one type of predator at one point in time may not be deterrent to another type of predator at another point in time. Additionally, these predator deterrent compounds may be used for other functions such as alarm signaling to other conspecifics. Defensive secretion compounds from the adult and the nymph giant mesquite bug (Thasus neocalifornicus: Coreidae) were isolated and identified by gas chromatography-mass spectrometry and NMR. The predominant compounds isolated from the nymph mesquite bugs during a simulated predator encounter were (E)-2-hexenal and 4-oxo-(E)-2-hexenal. In adults, the major compounds released during a simulated predator encounter were hexyl acetate, hexanal, and hexanol. Results from predator bioassays suggest the nymph compounds are more effective at deterring an insect predator than the adult compounds. By using behavioral bioassays, we determined the role of each individual compound in signaling to other mesquite bugs. The presence of the nymph secretion near a usually compact nymph aggregation caused nymph mesquite bugs to disperse but did not affect adults. Conversely, the presence of the adult secretion caused the usually loose adult aggregation to disperse, but it did not affect nymph aggregation. The compounds that elicited nymph behavioral responses were (E)-2-hexenal and 4-oxo-(E)-2-hexenal, while those that elicited adult behavioral responses were hexyl acetate and hexanal. The differences between the chemical composition of nymph and adult defensive secretions and alarm behavior are possibly due to differences in predator guilds.     

Influencing factors on electrochromic hysteresis performance of ruthenium purple produced by a WO3/Tris(2,2′-bipyridine)ruthenium(II)/polymer hybrid film

A [Ru(bpy)₃]²⁺ (bpy = 2,2′-bipyridine)/WO₃ hybrid (denoted as Ru-WO₃) film was prepared as a base layer on an indium tin oxide electrode by electrodeposition from a colloidal solution containing peroxotungstic acid, [Ru(bpy)₃]²⁺ and poly(sodium 4-styrenesulfonate). A ruthenium purple (RP, Fe^III₄[Ru^II(CN)₆]₃, denoted as Fe^III-Ru^II) layer was electrodeposited on a neat WO₃ film or a Ru-WO₃ film from an aqueous RP colloid solution to yield a WO₃/RP bilayer film or a Ru-WO₃/RP bilayer film, respectively. The spectrocyclic voltammetry measurement reveals that Fe^II-Ru^II is oxidized to Fe^III-Ru^II by a geared reaction of [Ru(bpy)₃]^2+/3+ and Fe^III-Ru^II is reduced by a geared reaction of H_xWO₃/WO₃ in the Ru-WO₃/RP film. These geared reactions produced electrochromic hysteresis of the RP layer. However, the absorbance change in the hysteresis was smaller than that for the Ru-WO₃/Prussian blue bilayer film reported previously, resulting from the lower electroactivities of any redox component for the Ru-WO₃/RP film. The lower electroactivities could be explained by the specific interface between the Ru-WO₃ and RP layers. It might contribute to either an increase of the interfacial resistance between the Ru-WO₃ and RP layers, or formation of the physically precise interface between the layers to make it difficult for counter ions to be transported in the interfacial liquid phase involved in the redox reactions in the film. The specific interface at the Ru-WO₃ and RP layers could be formed possibly by the electrostatic interaction between [Ru(bpy)₃]²⁺ and terminal [Ru(CN)₆]⁴⁻ moieties of RP. It could be suggested by the decreased redox potential of [Ru(bpy)₃]²⁺ in the Ru-WO₃ layer from 1.03 to 0.61 V by formation of the RP layer.     

Crystal structure of an aliphatic polyoxamide containing methyl side-groups: Poly(2-methyl-1,8-octamethyleneoxamide)

Poly (2-methyl-1,8-octametyleneoxamide) (nylon-MOMD-2) was prepared from dibutyl oxalate and 2-methyl-1,8-octamethylenediamine. The chemical structure was investigated by ¹³C nuclear magnetic resonance (¹³C NMR). The ¹³C NMR spectrum revealed that the methyl groups distribute among the four β-sites at random. The crystal structure and its temperature dependence were also investigated by molecular mechanics calculations, X-ray diffraction, and differential scanning calorimetry. The structure was determined to be monoclinic and a = 6.26 Å, b = 8.80 Å, c = 14.7 Å, and β = 50.7°. The torsion angle of the NH–CH₂ bonds has a skew conformation and there are the two distinct torsion angles in the crystal structure. The crystal structure of nylon-MOMD-2 has a disordered and statistical structure. The crystal structure shows no phase transition on heating until its melting point, although the unit cell expands in the a and b axis directions.     

N-Nitrosodimethylamine Formation from Hydrazine Compounds on Ozonation

N-Nitrosodimethylamine formation from six hydrazine compounds on ozonation was investigated. N-Nitrosodimethylamine formation yields in groundwater (pH 7) were 7.5%–89%. Results in the presence of tert-butyl alcohol indicated that N-nitrosodimethylamine was formed by reaction with molecular ozone, except for tetramethyltetrazene. From the results of effects of pH, tert-butyl alcohol and water matrix (groundwater and river water), it was suggested that reactions of tetramethyltetrazene with ozone, hydroxyl radicals, etc., were associated with N-nitrosodimethylamine formation. Some reactions restricted N-nitrosodimethylamine formation. Because N-nitrosodimethylamine formation of hydraxine compounds on chloramination was low, they are more important N-nitrosodimethylamine precursors on ozonation in actual water treatment.