A novel organoclay with antibacterial activity prepared from montmorillonite and Chlorhexidini Acetas

A series of novel organoclays with antibacterial activity were synthesized using Ca-montmorillonite and Chlorhexidini Acetas (CA) by ion-exchange. The resultant organoclays were characterized using X-ray diffraction (XRD), high-resolution thermogravimetric analysis (HRTG) and Fourier transform infrared spectroscopy (FTIR). Their antibacterial activity was assayed by so-called halo method. In the organoclays prepared at low CA concentration, CA ions within the clay interlayer adopt a lateral monolayer while a 'kink' state or a special state with partial overlapping of the intercalated CA in the organoclays prepared at 1.0-4.0 CEC. HRTG analysis demonstrates that CA located outside the clay interlayer exists in all synthesized organoclays, resulting from the complex molecular configuration of CA. The dramatic decrease of the surface adsorbed water and interlayer water is caused by the surface property transformation and the replacement of hydrated cations by cationic surfactant. These observations are supported by the results of FTIR. Antibacterial activity test against E. coli demonstrates that the antibacterial activity of the resultant organoclays strongly depends on the content of CA. Meanwhile, the resultant organoclay shows a long-term antibacterial activity that can last for at least one year. These novel organoclays are of potential use in synthesis of organoclay-based materials with antibacterial activity.     

Arrangement, conformation, and mobility of surfactant molecules intercalated in montmorillonite prepared at different pillaring reagent concentrations as studied by solid-state NMR spectroscopy

The arrangement, conformation, and mobility of dodecyltrimethylammonium cations (DDTMA+) intercalated in montmorillonite prepared with different pillaring reagent concentrations have been studied by 13C relaxation time measurement, cross-polarization dynamics, and two-dimensional proton wide-line separation (2D WISE) spectroscopy, as well as X-ray powder diffraction (XRD). We demonstrate that the arrangement of DDTMA+ and the mobility of various groups are different, depending on the pillaring concentration, but the conformations of alkyl chains are similar. XRD experiments illustrate that at three different pillaring concentrations (DDmt0.2, DDmt0.5, and DDmt1.0), the organic cations adopt a lateral-monolayer, lateral-monolayer, and pseudotrilayer arrangement, respectively. 13C MAS NMR reveals that the alkyl chains at the three concentrations uniformly display a large amount of mixed trans and gauch conformation (disordered) and a small amount of trans conformation (ordered). 13C spin-lattice relaxation time and 1H-13C cross-polarization dynamics measurement, along with 2D WISE NMR experiments, indicate that the mobility is much different for various groups at a given concentration and for a given group at different concentrations. At each concentration N-methyl unusually possesses the highest mobility, even exceeding that of the terminal methyl; at different concentrations the N-methyl and terminal methyl in DDmt1.0 exhibit the highest mobility compared with the other two samples.     

Cationic zinc enolates as highly active catalysts for acrylate polymerization

Unprecedented cationic zinc enolates have been generated by a novel activation route involving the amido to imino ligand transformation with B(C6F5)3, structurally characterized, and utilized as highly active catalysts for the production of high molecular weight polyacrylates at ambient temperature.     

Alkanethiol monolayers at reduced and oxidized zinc surfaces with corrosion protection: a sum frequency generation and electrochemistry investigation

In this work, octadecanethiol (ODT) was demonstrated to form ordered monolayers at either electrochemically reduced or oxidized Zn surfaces, by means of sum frequency generation (SFG) spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The SFG spectra of ODT-modified Zn electrodes featured three methyl group resonances in the C-H vibrational region (2800-3100 cm(-1)). A significant decrease in interfacial capacitance and an increase in charge-transfer resistance were observed in EIS measurement after ODT modification. The alkane chain tilt angle of ODT within a monolayer at the Zn surface was estimated as 0 degrees with respect to the surface normal by interfacial capacitance measurement via EIS. CV and SFG investigation revealed that ODT monolayers undergo reductive desorption from the Zn electrode in 0.5 M NaOH at -1.66 V (vs SCE) and in 0.5 M NaClO4 at -1.62 V. The integrated charge consumed to the desorption of ODT is determined as 87 mC/cm2 from the reductive peak on CV curve, resulting in a coverage of 9.0 x 10(-10) mol/cm2 (5.4 x 10(14) molecules/cm2) if assuming the reduction follows a one-electron process. ODT monolayers show corrosion protection to underlying zinc at the early immersion stage in base, salt, and acid media. However, the protection efficiency was reduced with immersion time due to the presence of defects within the monolayers.     

控制两相邻结构地震动响应的Maxwell模型流体阻尼器优化参数研究

运用被动连接单元减小相邻结构的振动被证明是一种行之有效的手段。将两相邻结构简化为两单自由度体系,用Maxwell模型模拟连接两相邻结构的流体阻尼器,分别导出了在地面白噪声激励下主结构平均振动能量最小或两相邻结构总平均振动能量最小这两个控制目标下流体阻尼器优化参数的一般表达式,该优化参数仅与两相邻结构的相对自振频率和相对质量有关,也讨论了两相邻结构的相对自振频率和相对质量对控制效果的影响。最后,运用具有不同相对参数的三类相邻结构在El Centro 1940 NS地震波作用下时域响应的数值结果说明了这种被动优化流体阻尼器能够非常有效地减小在地震作用下两相邻结构的振动响应。     

Surface Plasmon Resonance‐based Inhibitive Immunoassay Coupled with Dummy Template Molecularly Imprinted Polymer Solid Phase Extraction for On‐line Analysis of Trace Clenbuterol

A new indirect inhibitive immunoassay using surface plasmon resonance (SPR) coupled with molecularly imprinted polymer (MIP) was developed and applied for the analysis of trace clenbuterol (CL). A MIP coating using phenylephrine as the dummy template was synthesized in a flexible quartz capillary (30 cm×0.25 mm i.d.) by in situ polymerization technique, which then was used as the online solid phase extraction (SPE) tube before SPR detection. The thickness of the coating was 198 nm on average, illustrated by scanning electron microscope (SEM) image. The mechanism for adsorption of CL on dummy template MIP was found to be a Freundlich isotherm and pseudo‐second‐order model. The immunoassay was conducted on BIAcore 3000 biosensor automatically without pre‐treatment. The calibration curve was generated by linear fit in the range of 0.1–10 ng L^‐1 and 10–100 ng L^‐1. The detection limit was 0.1 ng L^–1, which is super sensitive. This method was directly applied for the analysis of real‐world samples without pretreatment.     

C4 Cumulene and the Corresponding Air‐Stable Radical Cation and Dication

A neutral C₄ cumulene 1 that includes a cyclic alkyl(amino) carbene (cAAC), its air‐stable radical cation 1 ^.+, and dication 1 ²⁺ have been synthesized. The redox property of 1 ^.+ was studied by cyclic voltammetry. EPR and theoretical calculations show that the unpaired electron in 1 ^.+ is mainly delocalized over the central C₄ backbone. The commercially available CBr₄ is utilized as a source of dicarbon in the cumulene synthesis.     

A low frequency piezoelectric power harvester using a spiral-shaped bimorph

We propose a spiral-shaped piezoelectric bimorph power harvester operating with coupled flexural and extensional vibration modes for applications to low frequency energy sources. A theoretical analysis is performed and the computational results show that the spiral structure has relatively low operating frequency compared to beam power harvesters of the same size. It is found that to optimize the performance of a piezoelectric spiral-shaped harvester careful design is needed.     

KrFH体系的势能函数与反应动力学研究(Ⅰ)基态KrFH的分析势能函数

使用ａｂｉｎｉｔｉｏ计算ＨＦ／ＬＡＮＬ２ＤＺ方法优化出了基态ＫｒＨＦ为Ｃ∞ｖ结构，而基态ＫｒＦＨ为Ｃｓ结构，同时，计算了平衡几何和离解能，并用ａｂｉｎｉｔｉｏ计算ＭＰ２／ＬＡＮＬ２ＤＺ方法计算了谐性力常数。应用多体项展式法导出了ＫｒＦＨ（Ｘ１Ａ′）体系的分析势能函数，研究了势能面上的主要特征     

Blue upconversion luminescence in Tm3+/Yb3+ co-doped new oxyfluoride tellurite glass

The thermal stability, Raman spectrum and upconversion properties of Tm3+/Yb3+ co-doped new oxyfluoride tellurite glass are investigated. The results show that Tm3+/Yb3+ co-doped oxyfluoride tellurite glass possesses good thermal stability, lower phonon energy, and intense upconversion blue luminescence. Under 980-nm laser diode (LD) excitation, the intense blue (475 nm) emission and weak red (649 nm) emission corresponding to the 1G4 → 3H6 and 1G4 → 3F4 transitions of Tm3+ ions respectively,were simultaneously observed at room temperature. The possible upconversion mechanisms are evaluated.The intense blue upconversion luminescence of Tm3+/Yb3+ co-doped oxyfluoride tellurite glass can be used as potential host material for the development of blue upconversion optical devices.