Evaluation of a novel silica-supported sol–gel sorbent prepared by a surface molecular imprinting technique for the selective separation of estazolam from human plasma

A molecular imprinting polymer (MIP) based on surface modification of silica gel was prepared via the sol–gel process with 3-aminopropyltriethoxysilane and phenyltrimethoxysilane as functional monomers, and estazolam as the template. The imprinted silica sorbent was characterized by Fourier Transform Infrared Spectroscopy, surface elemental analysis, and scanning electron microscopy (SEM). An MIP of agglomerated nano-particles with multi-pores was grafted onto the surface of the silica gel after hydrolytic condensation of the siloxane. The imprinted silica sorbent was used for solid phase extraction (SPE). Using water as loading solvent, the extraction efficiency for estazolam was higher compared to the use of an organic solvent. The imprinted silica sorbent was selective not only for the template, but also for the analogue. Compared to C₁₈-SPE and liquid–liquid extraction, the MIP-SPE was the most feasible technique for extraction of estazolam from human plasma; up to 98.7?±?1.2% recovery was achieved.     

Preparation of a novel molecularly imprinted polymer by the sol–gel process for sensing creatinine

A novel molecularly imprinted polymer (MIP) was prepared and used as an artificial receptor for creatinine (Cre). A sol–gel process was used to prepare the MIP. Tetraethoxysilane (TEOS) was employed as the crosslinker for the formation of a silica matrix for the MIP. Aluminum ion (Al³⁺) was chosen as the dopant to generate Lewis acid sites in the silica matrix for interactions with Cre. Through the sol–gel process, a polymeric matrix with memory sites for Cre was obtained, and this is mentioned here as the molecularly imprinted polymer for creatinine (MIP_Cre). The imprinting efficiency of MIP_Cre was evaluated by contrasting the adsorbed amount of Cre by MIP_Cre with that by the corresponding non-imprinted polymer (NIP). Creatine (Cn), N-hydroxysuccinimide (NHS), and l-tyrosine (l-tyr) were selected as interferences to study the selectivity of the MIP_Cre. The interference studies were also conducted using binary mixtures, such as Cre/Cn, Cre/NHS, and Cre/l-tyr. All these studies reveal that the MIP_Cre possess a remarkable affinity for Cre. The crucial role of Al³⁺ in this system is discussed in detail. Furthermore, the effects of concentrations of Al³⁺ and TEOS on the adsorbed amount of Cre by MIP_Cre were also investigated.     

Target-selective ion-exchange media for highly hydrophilic compounds: a possible solution by use of the “interval immobilization technique”

We prepared a crosslinked polymer as a separation and/or adsorption medium for CYN, as shown in Fig. 1. The polymers were evaluated by high-performance liquid chromatography (HPLC) and adsorption was examined under batch conditions. Results from detailed HPLC evaluation and measurement of the difference between the binding affinity for CYN and for other compounds showed the prepared polymer had specific recognition ability for CYN.     

A novel synthesis of a highly heat‐resistant organosilicon polymer using base catalysts

A new highly heatresistant polymer containing silicon, poly[(phenylsilylene)ethynylene1,3phenyleneethynylene] (MSP), was prepared by dehydrogenative coupling polymerization between phenylsilane and 1,3diethynylbenzene in the presence of base catalysts such as alkaline earth metal oxides, metal hydrides and metal alkoxides. The preparation process, catalytic activities, reaction mechanisms and polymer properties were discussed.     

Adsorption of CO2 as a method for the characterisation of the structure of alumina-pillared clay catalysts

The aim of this work was to study the effect of the metal loading on the structure of two series of cobalt and manganese pillared clay-supported catalysts. For this purpose, equilibrium data for CO₂ adsorption at 273 K were analysed using Freundlich, Langmuir and Toth isotherm models, in order to estimate the adsorption parameters and to relate them with the metal loading of the catalysts. The metal distributions on the porous structure of the catalysts were studied using the temperature programmed reduction results combined with information from the nitrogen physisorption data. Comparison of all results reveals that up to a certain metal loading, about 0.5 wt% of Co and 2 wt% of Mn, the metal oxide is well dispersed into the porous structure of the pillared clay. At higher metal loadings, bulk-metal oxide particles are formed on the external surface.     

Treatment feasibility of highly alkaline and highly radioactive liquid waste—a novel approach

Journal of Radioanalytical and Nuclear Chemistry - Typical Radioactive liquid waste with high alkalinity, high concentration of solvent degradation products along with high 134+137Cs content was...     

A novel highly selective fluorescent chemosensor for Hg（Ⅱ） in fully aqueous media

A novel fluorescent Hg~(2 ) chemosensor based on dithia-dioxa-monoaza crown ether was synthesized in four steps from inexpensive starting materials.This new sensor exhibited very strong fluorescence response to Hg~(2 ) (F_(Hg~(2 ))/F_(free)>130) and it was highly selective to Hg~(2 ) over the other metal ions by more than 45-fold.     

General and highly efficient fluorinated-N-heterocyclic carbene–based catalysts for the palladium-catalyzed Suzuki–Miyaura reaction

A general and highly efficient trifluoromethylated-N-heterocyclic carbene (NHC)-based catalyst for the palladium-catalyzed Suzuki–Miyaura reaction was reported. In the presence of the catalyst, reactions of non-activated aryl chlorides and triflates with aryl boronic acids occurred at room temperature with good to excellent yields (63–98%). In addition, catalysts generated from a combination of Pd(OAc)₂/imidazolium salt 6a is not only effective for the coupling of heteroaryl boronic acid with aryl halides and heteroaryl halides, but also efficient for coupling of other heteroaryl halides and heteroaryl boronic acids. Finally, the catalyst is highly effective for Suzuki–Miyaura reaction of aryl bromides and chlorides with 0.01–0.1 mol % loading if the temperature was raised at refluxed THF/H₂O.     

Preparation and properties of VO2 thin films by a novel sol–gel process

Vanadium dioxide (VO₂) thin films were fabricated using a simple and novel sol–gel process in which V₂O₅ was used as the vanadium source; oxalic acid was used as the reducing agent; and polyvinyl alcohol was used as the film former to control the viscosity of the VO₂ precursor solution and bond vanadium ions. The microstructure and surface morphology of VO₂ films were studied by X-ray diffraction and scanning electron microscopy, respectively. The results showed that using polyvinyl alcohol forms porous nanostructure of VO₂ films with a uniform grain size of ~25 nm. The measured optical reflectance shows well-defined phase transition as observed by an increase of reflectance upon heating above the transition temperature from ~11 to ~30 % at 1,100 nm. Upon cooling, the expected hysteresis is observed.     

Synthesis and characterization of a novel core–shell magnetic nanocomposite via surface-initiated RAFT polymerization for highly efficient and selective adsorption of uranium(VI)

Journal of Radioanalytical and Nuclear Chemistry - In this work, the nanoparticles possessing a macro-initiator (MNPs@SCSOEt) were firstly obtained by surface-initiated RAFT polymerization. The...     

Direct regiospecific and highly enantioselective intermolecular α-allylic alkylation of aldehydes by a combination of transition-metal and chiral amine catalysts

The first direct intermolecular regiospecific and highly enantioselective α-allylic alkylation of linear aldehydes by a combination of achiral bench-stable Pd(0) complexes and simple chiral amines as co-catalysts is disclosed. The co-catalytic asymmetric chemoselective and regiospecific α-allylic alkylation reaction is linked in tandem with in situ reduction to give the corresponding 2-alkyl alcohols with high enantiomeric ratios (up to 98:2 e.r.; e.r.=enantiomeric ratio). It is also an expeditious entry to valuable 2-alkyl substituted hemiacetals, 2-alkyl-butane-1,4-diols, and amines. The concise co-catalytic asymmetric total syntheses of biologically active natural products (e.g., Arundic acid) are disclosed.     

A highly active and selective palladium pincer catalyst for the formation of α-aryl ketones via cross-coupling

Several air and moisture stable Pd(II) pincer complexes were synthesized via oxidative addition of Pd(0) to novel PheBox pincer ligand precursors. Low loadings (1 mol%) of the Pd complex [t-BuPhebox-Me(2)]PdBr are capable of efficiently promoting the selective α-monoarylation of a variety of ketones with numerous aryl bromides in only 1 h at 70 °C with 82-99% yields.     

Magnetic nanosensors for highly sensitive and selective detection of bacillus Calmette-Guérin

With current concerns of the global threat from tuberculosis, it has become important to rapidly identify the bacteria. Traditional technologies involving isolation and amplification of the pathogenic bacteria are complicated and time-consuming. In this work, we describe a sensitive NMR-based detection method to identify bacteria via bacteria-induced self-assembly of magnetic nanoparticles. Bacillus Calmette-Guérin (BCG) was used as a surrogate for Mycobacterium tuberculosis. We prepared the probes by covalent immobilization of the anti-BCG monoclonal antibody onto carboxylic acid-functionalized magnetic nanoparticles. Once a solution containing BCG was introduced, the probes switched from a well dispersed state to an aggregated one, leading to a distinct and dose-dependent change in the spin-spin relaxation time (T2) of the solution. Thus the qualitative and quantitative detection method for BCG was established. The method provides specific detection of as few as 8 bacterial cells per millilitre in experimental samples within 1 hour, which will be promising for rapid detection of M. tuberculosis in clinical samples.     

Scaffold membranes for selective adsorption of α-tocopherol by phase inversion covalently imprinting technique

A molecular-imprinted membranes targeted to α-tocopherol (α-Toc) were prepared by phase inversion of polymer containing covalently bound template group to the polymer through ester group. For preparation of such polymer, a template-containing monomer, α-tocopherol methacrylate (α-TMA) was synthesized and copolymerized with acrylonitrile (AN). Phase inversion of the AN copolymer was carried out from the DMSO solution in water non-solvent. After membrane formed, removal of the template was performed in treatment with HCl acid solution. It was observed that the amounts of α-Toc bound to imprinted and non-imprinted membranes in ethanol/water (1:1%, v/v) were 20.8 ± 0.4 and 2.2 ± 0.1 μmol/g, respectively. Scatchard analysis indicated that the imprinted membranes exhibited high affinity and good selective binding of α-Toc relative to its analogs, δ-Toc, and 4-chromanol (4-Chr). Evidences showed that separation was achieved with separation factor of 15.5 for α-Toc/4-Chr in ethanol/water 1:1% (v/v) solution by simple filtration procedure with high flux permeation.     

Pseudo-crown ether having AIE and PET effects from a TPE-CD conjugate for highly selective detection of mercury ions

A new tetraphenylethylene-cyclodextrin（TPE-CD） conjugate with a linkage composed of long triethylene glycol chain and triazole ring on the CD rim has been designed and synthesized. The TPE-CD conjugate exists in a stretched form in DMSO and enhances its fluorescence after addition of a small amount of water due to aggregation-induced emission（AIE） effect. However, in the presence of a large amount of water, the TPE unit will enter the cyclodextrin cavity to form a folded self-inclusion compound....     

Synthesis and characterization of a novel organic–inorganic hybrid supramolecular recognition material and its selective adsorption for cesium

To separate Cs(I) from highly active liquid waste, a macroporous silica-based 25, 27-bis(iso-propyloxy)calix[4]arene-26,28-crown-6 (BiPCalix[4]C6) supramolecular recognition material, BiPCalix[4]C6/SiO₂–P, was synthesized and characterized by SEM, FT-IR, and TG-DSC. The adsorption properties of BiPCalix[4]C6/SiO₂–P and a macroporous polymer-based supramolecular recognition composite, BiPCalix[4]C6/XAD-7, were compared. It was found that BiPCalix[4]C6/SiO₂–P exhibited better adsorption ability and faster adsorption dynamics than BiPCalix[4]C6/XAD-7. The adsorption isotherm of Cs(I) onto BiPCalix[4]C6/SiO₂–P was studied at 298 K and it was well described by Langmuir isotherm model. The complex composition between BiPCalix[4]C6/SiO₂–P and Cs(I) was determined as 1:1 type by investigating the effect of the concentrations of BiPCalix[4]C6, Cs(I), and H⁺ on the adsorption. Meanwhile, the selectivity of BiPCalix[4]C6/SiO₂–P towards Na(I), K(I), Rb(I), Cs(I), Sr(II), Ba(II), Ru(III), Mo(VI), La(III), and Y(III) was investigated.     

Dynamics of carbide formation in iron-supported catalysts of the Fischer–Tropsch process promoted by copper and potassium

The kinetics of the formation of iron carbides during the activation of iron-coated catalyst for Fischer–Tropsch synthesis promoted by copper and potassium, and by carbon monoxide and syngas, is studied. It is established that the presence of copper lowers the initial temperature of hematite reduction to magnetite and leads to the formation of carbide in both CO and СО/Н₂. Potassium slows the rate of magnetite formation, but it accelerates the formation of iron oxide. It is shown that the rate of carbide formation during magnetite reduction for catalysts is half that in the reaction of hematite reduction to magnetite in both CO and СО/Н₂.     

Characterization of a titanium(IV)–porphyrin complex as a highly sensitive and selective reagent for the determination of hydrogen peroxide: a computational chemistry approach and a critical review

The Ti–TPyP reagent, i.e. an acidic aqueous solution of the oxo[5,10,15,20-tetra(4-pyridyl)porphyrinato] titanium(IV) complex, TiO(tpyp), was developed as a highly sensitive and selective spectrophotometric reagent for determination of traces of hydrogen peroxide. Using this reagent, determination of hydrogen peroxide was performed by flow-injection analysis with a detection limit of 0.5 pmol per test. The method was actually applied to determination of several constituents of foods, human blood, and urine mediated by appropriate oxidase enzymes. The reaction specificity of the TiO(tpyp) complex for hydrogen peroxide was clarified from the viewpoint of the reaction mechanisms and molecular orbitals based on ab initio calculations. The results provided a well-grounded argument for determination of hydrogen peroxide using the Ti–TPyP reagent experimentally. This review deals with characterization of the high sensitivity and reaction specificity of the Ti–TPyP reagent for determination of hydrogen peroxide, to prove its reliability in analytical applications. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A new tripodal rhodamine B derivative as a highly selective and sensitive fluorescence chemosensor for copper(Ⅱ)

A new tripodal rhodamine B derivative 2 was designed and synthesized by tripodal trialdehyde and rhodamine B hydrazide for the first time. This derivative could be used as a fluorescent chemosensor for the selective and sensitive determination of copper(II) in Tris-HCl buffer and ethanol aqueous mixed media. Under the optimum conditions described herein,fluorescence enhancement at 557/577 nm was linearly related to the concentration of copper(II) in the range of 0.10 to 10.00×10-5 mol·L-1,with a corre-latio...