Synthesis of some chiral liquid crystals and study of the effect of intramolecular hydrogen bonding on the phase behaviour

The synthesis of three new series of chiral Schiff's bases containing benzilideneaniline and 2-hydroxybenzilideneaniline moieties as mesogenic cores is presented. Differential scanning calorimetry, optical polarizing microscopy and X-ray diffraction measurements were used to study the phase transition temperatures and behaviour. The results reveal that most of these materials show chiral smectic mesomorphism.     

Preparation of Ce-Zr-O solid solution

A single phase solid solution of Ce-Zr-O can be made by using NH₄HCO₃ solution as precipitating agent. The influence of preparation conditions, such as pH, Zr⁴⁺/(CO₃ ^2-+HCO₃ ^-) and Ce³⁺/Zr⁴⁺ ratio on the formation of the solid solution were investigated. The results show that a single phase Ce-Zr-O solid solution can be formed only under a narrow window of preparation conditions, indicating that some compounds are formed in the precipitating process. The compound may contain Ce³⁺, Zr⁴⁺, CO₃ ^2-, HCO^3-, and OH^-. The solid solution so prepared can be described as Ce_0.37Zr_0.63O₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

液晶光定向层材料

本文综述了近10年来液晶显示用光定向层材料领域的研究现状和进展情况，主要概述了光降解型、光致异构型、光交联型以及自组装等材料，并对目前报道的液晶光定向机理进行了总结和归纳。     

THz spectroscopic investigation of 2,4-dinitrotoluene

We have investigated the terahertz (THz) spectrum of 2,4-DNT by using Fourier transform infrared spectroscopy in the 0.2–19.5 THz region. We also examined low-frequency intermolecular or phonon modes between 0.2 and 1.8 THz via THz time-domain spectroscopy. The extracted absorption coefficient and refractive index of an intermolecular band at 1.08 THz are 110 cm⁻¹ and 1.67, respectively. Density functional theory (DFT) was applied to obtain structure and vibrational frequencies of 2,4-DNT. The calculated results are in agreement with the experimental data. Observed vibrational frequencies have been interpreted using DFT. Two intermolecular or phonon modes were identified at 1.08 and 2.52 THz.     

Microwave-assisted clean synthesis of 6-aryl-2,4-diamino-1,3,5-triazines in [bmim][PF6]

An efficient and green approach was developed to prepare 6-aryl-2,4-diamino-1,3,5-triazines from corresponding arylnitriles and dicyanodiamide in ionic liquid [bmim][PF₆] under computer-controlled microwave irradiation. Particularly valuable features of this method included the short reaction time, good yield, convenient operation and eco-friendly solvent.     

Multiple Regulation Effects of Ammonium Acetate on ZnO Growth Process in Chemical Bath Deposition

Chemical bath deposition method has been used to synthesize a variety of ZnO morphology structures. However, the specificity and interaction of acetate and ammonium ions with ZnO crystal during the growth process remain elusive. This study contributes to understand the roles of ammonium acetate on the growth mechanism of ZnO in Zn(NO₃)₂-HMTA system. The growth process indicates that the nucleation experienced Zn²⁺-layered basic zinc salts (LBZs)-ZnO process, while the self-assembled unit changed from urchin-shaped, rod-shaped to a fully coupled twin-shaped structure with increasing ammonium acetate concentration. Ammonium acetate dominates the growth process by combing the ligand-ligand interaction of acetate ions binding to the same Zn-rich (0001) polar surface and ammonium ions regulating hexamethylenetetramine (HMTA) hydrolysis. Relatively regular hexagonal wurtzite structure and a dissolve-renucleation-regrowth process which retains the twin-shaped template and renucleates at the same position are observed at ∼10 mM ammonium acetate. Photoelectrochemistry (PEC) measurements show that the uniform hexagonal ZnO rods (Y-10, the sample named as Y-x (x represents x mM ammonium acetate, herein, x is 10 mM)) have a maximum photocurrent density of 1.54 mA cm⁻² at 1.23 V (vs. RHE), much higher than that of the dumbbell-shaped ZnO rods (Y-50, 0.20 mA cm⁻²) at the same voltage. These results provide a further explanation of morphology regulation mechanisms on ZnO synthesis processes and pave the road for more practical applications.     

Structure-Activity Relationship, Cytotoxicity and Mode of Action of 2-Ester-substituted 1,5-Benzothiazepines as Potent Antifungal Agents

Our studies examined the structural features responsible for the antifungal activity of 2-ethoxycarbonyl-1,5- benzothiazepine （7a）. Three series of 1,5-benzothiazepine derivatives were synthesized and screened for their antifungal activity. The results suggested that the ethoxycarbonyl group at the 2 position and the imine moiety on the seven-membered ring are essential for activity. The most potent of the synthesized analogues （7a, 7b） were further studied by evaluating their cytotoxicity and mode of action （for 7a）. The results showed that compounds 7a and 7b were relatively safe for BV2 cells, but compound 7a interfered with Cryptococcus neoformans cell wall integrity by increasing the chitinase activity. Therefore, compound 7a was considered safe as an antifungal agent for animal cells.     

A new method for preparing TiO2 catalyst honeycombs without sintering

Composite catalyst honeycombs without sintering were prepared via kneading, mulling, extrusion molding, and solidifying at room temperature with the magnesite oxychloride gels modified by nano-rice husk ash (RHA) as a solidifying agent. The effects of nano-RHA and composite water-resistant agents on the water resistance of magnesite materials were studied. The solidification of the modified magnesite gels on TiO₂ catalyst honeycombs was analyzed. The experiments show that the proportional addition of nano-RHA markedly increases the water resistance of magnesite materials without reducing the bending strength, and the softening coefficient increases from 0.29 to 0.78. With further addiition of the complex water-resistant agents, the softening coefficient increases from 0.78 to 0.97. The optimal mass ratio of MgO in the solidifying agent to TiO₂ is 4:1, and the bending strength of unsintered catalyst honeycombs is 11.46 MPa. The desulfurization rate and denitration rate of this composite catalyst honeycomb on simulation smoke was 97 and 65 %, respectively, in 3 h.     

Nanosized Carbon Macrocycles Based on a Planar Chiral Pseudo Meta-[2.2]Paracyclophane

Structural designs combining cycloparaphenylenes (CPPs) backbone with planar chiral [2.2]paracyclophane ([2.2]PCP) lead to optical-active chiral macrocycles with intriguing properties. X-ray crystal analysis revealed aesthetic necklace-shaped structures and size-dependent packages with long-range channels. The macrocycles exhibit unique photophysical properties with high fluorescence quantum yield of up to 82 %, and the fluorescent color varies with ring size. In addition, size-dependent chiroptical properties with moderately large CPL dissymmetry factor of 10⁻³ and CPL brightness in the range of 30–40 M⁻¹ cm⁻¹ were observed.