Synthesis of large pore-diameter SBA-15 mesostructured spherical silica and its application in ultra-high-performance liquid chromatography

A modified synthesis approach for spherical large pore-diameter SBA-15 mesoporous silica (SLP-SBA-15) with particle size range of 0.5–1 μm was being reported. It was worth mentioning that in this improved methodology, the use of cetyltrimethylammonium bromide (CTAB) as co-template significantly reduced the self-assembly time from 24 h to 45 min. Moreover, under reflux condition, the reaction time could be further shortened by reducing the aging time from 48 h to 6 h. The resultant SLP-SBA-15 was thereafter successfully functionalized and packed into an ultra-high-performance liquid chromatography (UHPLC) column for the separation of aromatic compounds. A variety of characterizations demonstrated that the silica products exhibited a well-ordered 2d hexagonal mesostructure with well-formed spherical morphology. pore-diameter can be enlarged up to 8.2 nm without affecting the structural order. The SLP-SBA-15 samples showed excellent thermal and hydrothermal stabilities. The octadecyltriethoxysilane functionalized SLP-SBA-15 (SLP-C18-SBA-15) was demonstrated to be an effective stationary phase in UHPLC application because the column exhibited significantly reduced column pressure (2800 psi) at a flow rate of 0.4 ml/min. Accordingly, it would afford greater flexibility for tuning of the flow rate to meet the fast separation requirement.     

Effect of (chloride salt) electrolytes on the mixed micellization of (equimolar) a cationic gemini (dimeric) surfactant and a cationic conventional (monomeric) surfactant

Herein we report the effect of (chloride salt) electrolytes on the mixed micellization of (equimolar) a cationic gemini (dimeric) surfactant, hexanediyl-1,6-bis(dimethylcetylammonium bromide) (16-6-16), and a cationic conventional (monomeric) surfactant, cetyltrimethylammonium bromide (CTAB) in aqueous solutions. In absence and presence of (chloride salt) MCl (where M?Li, Na, and K) electrolytes, the critical micelle concentration (CMC) of mixed (16-6-16 + CTAB) surfactants was measured by surface tension measurements. With increasing the concentration of electrolyte, the CMCs were increasing. The surface properties and the thermodynamic parameters of the mixed micellar systems were also evaluated. From these evaluated thermodynamic parameters, it was found that in presence of electrolyte the stability of the mixed micellar system is more.     

Shape-controlled synthesis of highly monodisperse and small size gold nanoparticles

We describe here that fine control of nanoparticle shape and size can be achieved by systematic varia-tion of experimental parameters in the seeded growth procedure in aqueous solution. Cubic and spherical gold nanoparticles are obtained respectively. In particularly, the Au cubes are highly mono-disperse in 33±2 nm diameter. The experimental methods involve the preparation of Au seed particles and the subsequent addition of an appropriate quantity of Au seed solution to the aqueous growth solutions containing desired quantities of CTAB and ascorbic acid (AA). Here, AA is a weak reducing agent and CTAB is not only a stable agent for nanoparticles but also an inductive agent for leading increase in the face of nanoparticle. Ultraviolet visible spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM) are used to characterize the nanoparticles. The results show that the different size gold nanoparticles displayed high size homogenous distribution and formed mono-membrane at the air/solid interface.     

Highly Sensitive and Selective Voltammetric Sensor Fullerene Modified Glassy Carbon Electrode for Determination of Cefitizoxime in Solubilized System

The usefulness of fullerene modified glassy carbon electrode in mediating the reduction of cefitizoxime in solubilized system has been demonstrated. Due to the unique structure and extraordinary properties, fullerene shows higher catalytic efficiency towards cefitizoxime reduction. The kinetic parameters, electron transfer coefficient (α) and rate constant (K₀) across the modified electrode are 0.37 and 0.1081/s respectively. The proposed square‐wave voltammetric method is linear over the concentration range 1.2–10.3 µg/mL. The limit of detection (LOD) is found 0.27 ng/mL. High sensitivity and selectivity together with low detection limit of the electrode response make it suitable for the determination of cefitizoxime.     

Synthesis of Uniform Gold Nanorods with Large Width to Realize Ultralow SERS Detection

In this work, we successfully demonstrate high-yield synthesis of high-quality gold nanorods (Au NRs) with width ranging from 6.5 nm to 175 nm by introducing heptanol molecules as secondary templating agents during cetyltrimethylammonium bromide-templated, seeded growth method. The results show that an appropriate concentration of heptanol molecules not only alter the micellization behavior of CTAB in water, but also help silver ions impact the symmetry-breaking efficiency of additional Au−NP seeds in addition to enhancing the utilization of gold precursors. Moreover, the generality and versatility of the present strategy for synthesis of Au NRs with flexible controlled dimensions are further demonstrated by successful synthesis of Au NRs with the assistance of other fatty alcohols with properly long alkyl chains. Furthermore, when arrays of vertically aligned Au NRs with large width (AVA−Au_120×90 NRs) are used as SERS substrates, they can achieve the ultralow limit of detection for crystal violet (10⁻¹⁶ M) with good reliability and reproducibility, and the rapid detection and identification of residual harmful substances.     

Rheological Properties and Crosslinking Rheo-Kinetics of CMHEC/CTAB Synergistic Systems

Aiming at synergistic interaction between carboxymethyl hydroxyethyl cellulose (CMHEC) and cetyltrimethyl ammonium bromide (CTAB), mixtures of CMHEC and CTAB solutions were investigated, employing relative viscosity and rheological measurements. The effects of mass ratio of CMHEC and CTAB solutions, temperature, and polysaccharide concentration on relative viscosities of CMHEC/CTAB systems were studied. Rheological method was used to study rheo-kinetics of the isothermal crosslinking process for CMHEC/CTAB synergistic fracturing fluid, and the novel crosslinking rheo-kinetics equation was established. The results showed the strong synergism between CMHEC and CTAB, resulting in a higher relative viscosity, storage modulus G′, and loss modulus G″ than that of separate ones. CMHEC/CTAB systems behave as pseudoplastic fluids with considerable thixotropy and viscoelasticity, and the flow behavior can be well described by Carreau?Williamson model. The crosslinking rheo-kinetics equation can well describe the isothermal crosslinking process at different shear rates. The model parameters are well-defined and reasonable.     

水热法制备ZnS纳米线

以十六烷基三甲基溴化铵(CTAB)为表面活性剂，利用水热法通过二吡啶硫氰酸锌分解制备了ZnS纳米线，并用SEM、XRD、EDX和HR-TEM等方法对其纳米结构进行了表征。实验结果表明，反应时间和表面活性剂浓度是决定纳米ZnS最终形貌的关键因素，CTAB起到了纳米线生长的分子-诱导模板作用。     

片层花状氧化镁的制备及其吸附性能研究

本文以十六烷基三甲基溴化铵(CTAB)作为结构导向剂,利用尿素在高温条件下受热分解生成的二氧化碳与氯化镁反应,通过层-层自组装制备出具有片层花状结构的氧化镁,并以其对含Pb(Ⅱ)溶液的吸附为探针反应,研究其对重金属离子的吸附性能。实验结果表明,所制备氧化镁的前驱体为碱式碳酸镁;经过600℃焙烧后,得到的片层花状氧化镁比表面积大于60 m2.g-1,具有良好的吸附性能;对含Pb(II)溶液的吸附过程符合Langmuir等温吸附,最大吸附量达到320 mg.g-1。     

纳米棒状MAl2O4:Eu2+, Dy3+(M=Sr, Ba)长余辉发光材料的制备与性能

利用硝酸铝、硝酸锶/硝酸钡、尿素为原料,以一定比例H2O/正丁醇/CTAB的混合液作传递压力的介质进行反应,然后将得到的前驱体在还原气氛下高温煅烧,得到亮度高、余辉时间长的MAl2O4∶Eu^2＋,Dy^3＋纳米结构长余辉发光材料。TEM测试表明,高温煅烧后得到的MAl2O4∶Eu^2＋,Dy^3＋均为棒状结构,其激发光谱和发射光谱均为宽带,主发射峰分别为513和498 nm,是典型的Eu^2＋5d→4f跃迁。在对单掺Eu^2＋与双掺Eu^2＋,Dy^3＋比较的过程中,明显发现双掺Eu^2＋和Dy^3＋的强度增加,且余辉增强。材料的余辉强度随时间的变化由最初的快减过程和随后的慢减过程组成,符合I=t^-1.1双曲线规律。该方法操作简单,在不同的温度和时间下均合成出了棒状MAl2O4∶Eu^2＋,Dy^3＋,不需球磨,可直接应用。