卤素离子触发亚铁四面体笼的自旋状态转换

合理构筑了3个具有固态自旋交叉特性的亚铁四面体笼状化合物1~3。单晶X射线衍射分析证实了化合物是由6个咪唑席夫碱配体和4个亚铁离子组装形成的边导向封顶胶囊结构。金属中心占据四面体的顶点,而配体组成了四面体的边。这些笼状化合物的内部空腔被咪唑基团环绕,而外部则被取代苯环包围。一个阴离子客体被限域在笼状化合物空腔内,并与笼状化合物主体产生较强的相互作用。当在笼状化合物的乙腈溶液中加入卤素离子（Cl^-和Br^-）时,溶液的颜色和MLCT峰强度会发生明显变化,表明亚铁四面体笼状化合物的自旋状态由低自旋向髙自旋发生了转换。     

New Tools for Investigating Electromagnetic Hot Spots in Single‐Molecule Surface‐Enhanced Raman Scattering

Surface‐enhanced Raman scattering (SERS) is quickly growing as an analytical technique, because it offers both molecular specificity and excellent sensitivity. For select substrates, SERS can even be observed from single molecules, which is the ultimate limit of detection. This review describes recent developments in the field of single‐molecule SERS (SM‐SERS) with a focus on new tools for characterizing SM‐SERS‐active substrates and how they interact with single molecules on their surface. In particular, techniques that combine optical spectroscopy and microscopy with electron microscopy are described, including correlated optical and transmission electron microscopy, correlated super‐resolution imaging and scanning electron microscopy, and correlated optical microscopy and electron energy loss spectroscopy.     

Dual switchable six-ring bent-core liquid crystals with azo linkages exhibiting B1 and B2 mesophases

A new series of asymmetric bent-core compounds were synthesised using azo linkages with equal as well as unequal terminal alkyl chains and their photo and electrical switching properties investigated. The mesomorphic properties were characterised using polarised optical microscopy, X-ray diffraction and differential scanning calorimetry. The lower homologues of the series of compounds show a B₁ phase whereas higher homologues exhibit a B₂ phase. The B₂ phase shows an anticlinic-antiferroelectric switching behaviour during electro-optic measurements. The photo-switching properties of the azobenzene containing bent-core molecules were investigated using ultraviolet-visible spectroscopy. The trans to cis photo isomerisation was observed at 25 s whereas reverse processes took 14 h in chloroform.     

Inhibition of CTAB on the Corrosion of Mild Steel in Hydrochloric Acid

The inhibition effect of cetyl trimethyl ammonium bromide (CTAB) on the corrosion of mild steel in 1.0 mol L^?1 hydrochloric acid (HCl) has been studied at different temperatures (25–60°C) by weight loss and potentiodynamic polarization methods. The results reveal that CTAB behaves as an effective inhibitor in 1.0 mol L^?1 HCl, and the inhibition efficiency increases with the inhibitor concentration. Polarization curves show that CTAB is a mixed-type inhibitor in hydrochloric acid. The results obtained from weight loss and polarizations are in good agreement. The effect of immersion time on corrosion inhibition has also been examined and is discussed. The adsorption of inhibitor on mild steel surface obeys the Langmuir adsorption isotherm equation. Thermodynamic parameters have been obtained by adsorption theory. The inhibition effect is satisfactorily explained by the parameters.     

The Role of Column Switching in Analysing Complex Samplest

Abstract

Our objective in using column switching is primarily to achieve the desired separation in the minimum analysis time. Complimentary to this aim is the need for sample and column cleanup followed by column re-equilibration. Finally, all operations should be capable of automation. Fundamental to column switching methodology is the concept of Zone cutting, where part of the chromatogram is transferred to another column. This forms the basis of sample cleanup and is a very versatile and powerful method. Multiple zone cutting is also possible to further increase the scope of cleanup or to minimise analysis time. Zone cutting is also complimentary to the techniques of trace enrichment and recycling. Examples will be given involving the use of these techniques in the analysis of complex matrices such as urine, plant extracts, wine and serum. The latter will be used to propose a novel approach to the quantitative analysis of anti-convulsants in serum using hexobarbital as internal standard.     

Investigation on ion movement in the fringe-field switching mode depending on resistivity of alignment layer and dielectric anisotropic sign of liquid crystal

Adsorption and desorption of ions at interface between liquid crystal and alignment layer in liquid crystal displays play a crucial role in residual direct current voltage associated with image sticking. In this article, the dependency of such adsorption and desorption of ions on resistivity of alignment layer and sign of liquid crystal dielectric anisotropy in the fringe-field liquid crystal cell has been investigated. Our studies show that the time constant of ions during adsorption and desorption depends upon resistivity and dielectric constant of liquid crystal and alignment layer, and most strongly influenced by the resistivity of alignment layer such that the one with lower resistivity in two orders shows much faster adsorption and desorption at the interface than that of the one with higher resistivity.     

Fast switching of vertically aligned negative liquid crystals by optically hidden relaxation

We propose a method for fast switching of vertically aligned (VA) negative liquid crystals (LCs) by hiding the relaxation process of LCs. During the turn-off process, a strong in-plane electric field is applied for a short duration of time instead of relying solely on the slow relaxation of LCs. The LC molecules are rotated to the transmission axis of one of the polarisers by the applied in-plane electric field, resulting in turn-off switching that is 5.8 times faster than that of a conventional VA cell. By applying an overdriving scheme, we experimentally obtained a total response time of 3.3 ms.     

A new type of two-dimensional packed + capillary column GC system. I. Theory

Summary To match the need of high efficiency capillary column (plate number N₂, Plate height H₂ and carrier gas linear velocity U₂), a new high efficiency packed column (N₁, H₁ and U₁) at high carrier gas velocity with small capacity factor has been developed in the light of theoretical discussion of factors effecting the column efficiency utilization ratio.     

Tribo-corrosion behavior of Zn-Ni-Cu and Zn-Ni-Cu-TiB2 coated mild steel

In this investigation , Zn-Ni-Cu and Zn-Ni-Cu-TiB₂ were coated on a mild steel specimen using a high velocity oxy fuel thermal spray (HVOF) process. The surface morphology and coated powder distribution of coated specimens were characterized using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray-Elemental mapping. The pin-on-disc (ASTM G99-17) method was used to examine the wear resistance of the coated and uncoated mild steel specimens. Both coated Zn-Ni-Cu and Zn-Ni-Cu-TiB2 on mild steel saw reduced wear volume loss than uncoated mild steel. The coated samples of Zn-Ni-Cu and Zn-Ni-Cu-TiB2 on Mild Steel were put through a scratch test to determine the adhesion strength of the coating with the substrate. The adhesion strength of coated Zn-Ni-Cu and Zn-Ni-Cu TiB2 mild steel was higher than that of untreated mild steel, indicating a solid link between the coating and substrate and minimal delamination. Using the Vickers hardness test to measure the hardness caused by the coating, it was shown that coated samples of Zn-Ni-Cu and Zn-Ni-Cu-TiB2 coated mild steel had significantly higher hardness than uncoated mild steel. Using ASTM G1-03 and ASTM G-31 standards, a 0.2 M HCl immersion cycle test was conducted for 28 days to test the corrosion resistance of coatings in an acidic media (672Hrs). When compared to Zn-Ni-Cu and Zn-Ni-Cu-TiB2 coated mild steel, the weight loss for the uncoated mild steel was significantly larger. Additionally, XRD examination showed that coated samples had less rust on their surface than uncoated samples. Both Zn-Ni-Cu and Zn-Ni-Cu-TiB2 on Mild Steel were anti-corrosive, as evidenced by increased corrosion potential and reduced corrosion current density when compared to uncoated mild steel, according to electrochemical impedance spectroscopy (EIS)/Tafel study in 0.2 MHCl. The outcomes of each test were very encouraging and demonstrated the durability of these coatings against wear and corrosion.