Microstructural and compositional studies of liquid-phase deposition derived PbTiO3 thin films on LaNiO3 substrates

PbTiO₃ thin films were successfully deposited on the LaNiO₃ (LNO) substrates by the liquid-phase deposition (LPD) method and post-annealing at various temperatures. The structure, morphology and composition of the films were investigated by some analytical techniques. The as-deposited films are amorphous and composed of densely packed spherical particles. The films with the grain size of 180 nm start to decompose and crystallize into perovskite structure at 450 °C and show a perovskite single phase with tetragonal structure after annealing at 650 °C. X-ray photoelectron spectroscopy (XPS) analysis reveals that the as-deposited film contains fluorine and carbon as major impurities. Fluorine could be completely eliminated by annealing at 650 °C in air.     

Cavity resonant mode in a metal film perforated with two-dimensional triangular lattice hole arrays

The transmission property of metallic films with two-dimensional hole arrays is studied experimentally and numerically. For a triangular lattice subwavelength hole array in a 150 nm thick Ag film, both cavity resonance and planar surface modes are identified as the sources of enhanced optical transmissions. Semi-analytical models are developed for calculating the dispersion relation of the cavity resonant mode. They agree well with the experimental results and full-wave numerical calculations. Strong interaction between the cavity resonant mode and surface modes is also observed.     

Withangulatin I, a new cytotoxic withanolide from Physalis angulata

A new withanolide, withangulatin I (2), was isolated from the whole plant of Physalis angulata. Its structure was established as (20S,22R)-15alpha-acetoxy-5beta,6beta-epoxy-14alpha-hydroxy-1,4-dioxo-witha-2,16,24-trienolide on the basis of chemical and spectroscopic methods including 2D-NMR and circular dichroism (CD) experiments. Withangulatin A (1) and withangulatin I (2) were tested for their cytotoxic activities against two human cancer cell lines, colorectal carcinoma COLO 205 and gastric carcinoma AGS, in vitro. Compounds 1 and 2 exhibited inhibitory activities against these two human cancer cells with IC(50) values of 16.6 and 1.8 and 53.6 and 65.4 muM, respectively.     

Lanostane-type triterpenoids from Diospyros discolor

Four new lanostane-type triterpenes, 24-ethyl-3beta-methoxylanost-9(11)-en-25-ol (1), 3beta-methoxy-24-methylenelanost-9(11)-en-25-ol (2), 3beta-methoxy-25-methyl-24-methylenelanost-9(11)-en-21-ol (3) and 3beta-methoxy-24-methyllanosta-9(11),25-dien-24-ol (4) together with three known triterpenes, betulinaldehyde, betulinic acid methyl ester, and ursaldehyde have been isolated from the methanol extract of the twigs of Diospyros discolor. The structures of those new compounds were elucidated by spectroscopic methods.     

Conversion of squid pens to chitosanases and dye adsorbents via Bacillus cereus

Research on Chemical Intermediates - The purpose of this study was to reclaim squid pens for the production of chitosanases and biosorbents of food colorants and industrial dyes via Bacillus cereus...     

Fabrication and characterization of core-shell photonic crystals via a dipping process

High-quality polystyrene (PS) colloidal photonic crystals in large area were fabricated in 24 h via a capillary-enhanced process. Then, the photonic crystals with core-shell structure were obtained by incorporating silica nanoparticles into the interstitial space of opal template via a dipping process. The filling ratio (V_silica) of interstitial space could be manipulated by dipping colloidal crystals into suspensions with different concentrations of silica nanoparticles, which in turn renders the obtained core-shell photonic crystals. The absorptive peak of opal without dipping process is at 445 nm as measured by UV–vis spectrometry. The filling ratios of 0.130, 0.167 and 0.253 can be calculated according to the modified Bragg's Law, which corresponds to the absorptive peaks for core-shell opals at 453, 463 and 469 nm obtained from suspensions with silica nanoparticles of 0.017, 0.122, and 0.244 wt%, respectively. Therefore, by using this dipping process, the characteristic absorption wavelength for photonic crystal will be varied easily, efficiently and cost effectively than that by traditional methods for constructing opal from monodispersed colloids of different diameters.     

Ab Initio Construction of Quasiadiabatic Potential-Energy Surfaces for Cycloaddition Reactions of Ethene and Substituted Allylic Cations

The nature of some well known 2π + 2π cycloaddition reactions was studied by explicit construction of the quasiadiabatic potential-energy surfaces for the cycloaddition of ethene and various monosubstituted allylic cations. Such surfaces determined by ab initio MO computations are particularly suitable for analysis of symmetry selection rules. By examining the characteristics of such surfaces, we have studied the substituent effect and the role played by the positive charge in such systems. Qualitative discussion based on simplified MO, involving fewer electrons, is also given.     

Influence of humidity on the fabrication of high-quality colloidal crystals via a capillary-enhanced process

Three-dimensional colloidal crystals have attracted a great deal of attention because of their potential use in photonic crystal, sensors, and other applications, but the bottlenecks in fabricating colloidal crystals include longer processing time and the lack of large-area ordered samples. A proposed capillary-enhanced method, which is a novel, efficient process for fabricating high-quality colloidal crystals in 24 h, is reported. It is necessary for increasing the processing rate by elevating the evaporation temperature but commonly resulted in the deposition of less-ordered crystals. However, high-quality colloidal crystals can be obtained in a controlled high-humidity system, resulting from the existence of secondary capillary forces present in high ambient humidity. Furthermore, the effect of secondary capillary forces will be confirmed, and it will increase with increasing humidity levels according to the semiquantitative analysis view of the surface thermodynamic behavior of small particles, including the modified Kelvin and Young-Laplace equations. Therefore, it can fine tune the relative position of the neighboring particles in the microarray and efficiently decrease the number of defects, resulting in the formation of perfect colloidal crystals with the assistance of enhanced secondary capillary forces.