Thermal effects on the structural properties of tungsten oxide nanoparticles

Tungsten oxide nanoparticles are prepared by evaporating and oxidizing the tungsten boat in helium and oxygen atmosphere and then quenched to the liquid nitrogen temperature. The as-prepared tungsten oxide nanoparticles are porous-free with uniform size. The morphology and particle size distribution of the as-prepared and after sinter treatments tungsten oxide nanoparticles are revealed by TEM and AFM. The long-range order of these nanoparticles can be examined by X-ray diffraction technique. The as-prepared nanoparticles exhibit a mixture structure of monoclinic and hexagonal crystals. Preliminary X-ray diffraction results indicate that the hexagonal structure is transformed to monoclinic structure after annealing to above 600°C. In order to better distinguish the structural properties of the tungsten oxide (WO_{3− x}) nanoparticles before and after annealing, the X-ray absorption spectrum technique is utilized; thus, the detailed local atomic arrangement of oxygen and/or tungsten can be determined. According to the XAS result, the shape of the W L₃-edge undergoes no considerable changes. This infers that structural transformation of tungsten oxide nanoparticle may be caused by the migration of oxygen after sintering. From the O K-edge of absorption spectrum, it suggests that a mixture phase structure is obtained when sintered below 300°C. And this result indicates that heat treatment to approximately 600°C produces a stable structure of a monoclinic crystal of WO₃.     

Physical Characterization of Acid-Doped Polyaniline

Polyaniline has been synthesized by the chemical and electrochemical oxidation of aniline. The conductivities increase by seven order of magnitude upon protonation. The IR absorption band near 1590 cm^?1 shifts to a lower frequency upon protonation. Visible spectra vary with the degree of protonation and the applied potential. Cyclic voltammetry indicates that polyaniline exists in several forms.     

New approach to quantum corrections in synchrotron radiation

Owing to a recent controversy over the importance of the second-order quantum corrections to the power spectrum of synchrotron radiation, we here reexamine this question by using a proper time method to calculate the forward Compton scattering of a real photon on a spin-0 charged particle in external magnetic fields. This approach, aside from being the simplest method found so far, has the feature that it resembles the classical procedure so that the quantum corrections can be identified at every stage of the computation. The option of being able to perform first the angular integration before doing the proper time integral enables us to simplify the calculation and to obtain the quantum corrections unambiguously. We find that the criterion for the quantum corrections to be important is the same as that found more than two decades ago.     

The Constituents of the Bark of Armand Pine

Twenty three compounds were isolated from the bark of Pinus armandii. These compounds include nine serratenes (1-9), a norserratenone 10, eight phenols 11-18, two flavonoids 19-20, one lignan 21, a diterpene 22 and a novel triterpendiol acetonide 23. Their structures were determined from their physical and spectral properties.     

Ferroelectric liquid crystal materials synthesized from 2(S)-[2(S)-methylbutyloxy]propanol

A new chiral alcohol, 2(S)-[2(S)-methylbutyloxy]propanol (3), containing two chiral centres has been synthesized from ethyl lactate and (S)-1-iodo-2-methylbutane. It was used as a chiral building block for the preparation of ferroelectric liquid crystal materials. Several of the new materials exhibit an enantiotropic S*_c phase with a wide temperature range. The results indicate that the molecular structure of 3 is useful for synthesizing ferroelectric liquid crystal materials.     

Antiferroelectric liquid crystals derived from a new optically active (R)-3-ethylmercapto-2-methylpropionic acid

A new optically active (R)-3-ethylmercapto-2-methylpropionic acid has been synthesized using D(-)—2,10-camphorsultam as a chiral auxiliary. The optical purity of the acid obtained was greater than 98 per cent. Its derivatives, (R)-4-(3-ethylmercapto-2-methylpropionyl)phenyl 4'-alkoxybiphenyl-4-carboxylates (EMMPPmBC; m = 7-16), have been prepared for the investigation of liquid crystalline properties as a function of peripheral alkyl chain length. Optical studies showed that all members exhibited an antiferroelectric S*c_A phase. The results also indicate that a lengthened alkyl chain length is favoured for S_cA* phase formation.     

Interstitial site of Cu in Ca

Fluorescence EXAFS was used to study the siting of a dilute solution of Cu in Ca. The Cu is interstitial in Ca, and no more than .4Å away from the center of the octahedral site. No lattice dilation was seen about the Cu atom, even though Cu is “too big” to fit into the interstitial site.