Sequential Preparation Research Articles

Magnetic gold catalysts obtained by sequential preparation for highly efficient catalytic reduction of nitroaromatics

Noble metal catalysts have received considerable interests owing to their glamorous properties and applications in heterogeneous catalysis. In this work, the magnetic Au nanoparticles catalysts were successful fabricated via sequential preparation strategy at room temperature. 4-nitrophenol was chosen as the model molecule to evaluate the catalytic reduction activity for the preparation of amines from their corresponding nitroaromatics. The results showed that the catalytic reaction related with 4-nitrophenol could be achieved in 3 min, and the catalyst could be easily reused at least 15 cycles without significant reduction in activity when the as-prepared Fe3O4@CB6@Au0.4% nanoparticles acted as the catalyst. It revealed that the as-prepared catalyst exhibited outstanding catalytic performance and cycling stability. The SEM and TEM images demonstrated that the Au species presented in composite system in the form of highly dispersed Au0 nanoparticles, playing a crucial role in the catalytic process. Therefore, the Au nanoparticles combined with Fe3O4@CB6 prepared by the sequential preparation strategy had excellent catalytic reduction properties for nitroaromatics, and the method could open a new way for the design of other highly dispersed nanometallic materials.

Quantum Dot Molecule Devices with Optical Control of Charge Status and Electronic Control of Coupling

AbstractTunnel‐coupled pairs of optically active quantum dots—quantum dot molecules (QDMs)—offer the possibility to combine excellent optical properties such as strong light‐matter coupling with two‐spin singlet–triplet () qubits having extended coherence times. The basis formed using two spins is inherently protected against electric and magnetic field noise. However, since a single gate voltage is typically used to stabilize the charge occupancy of the dots and control the inter‐dot orbital couplings, operation of the qubits under optimal conditions remains challenging. Here, an electric field tunable QDM that can be optically charged with one (1h) or two holes (2h) on demand is presented. A four‐phase optical and electric field control sequence facilitates the sequential preparation of the 2h charge state and subsequently allows flexible control of the inter‐dot coupling. Charges are loaded via optical pumping and electron tunnel ionization. One‐ and two‐hole charging efficiencies of (93.5 ± 0.8)% and (80.5 ± 1.3)% are achieved, respectively. Combining efficient charge state preparation and precise setting of inter‐dot coupling allows for the control of few‐spin qubits, as would be required for the on‐demand generation of 2D photonic cluster states or quantum transduction between microwaves and photons.

TiO2-supported Au-Ag plasmonic nanocatalysts achieved by plasma restructuring and activation

Plasmonic Au-Ag/TiO2 bimetallic nanocatalyst is regarded as a promising visible-light (VL) photocatalyst due to its wide light absorption and potentially enhanced activity. For its preparation, Au precursors usually contain Cl and co-impregnation/co-deposition suffers from AgCl precipitation, and consequently Au and Ag have to be sequentially supported. However, Au and Ag species of the sequential preparation are individually isolated and difficult to be homogeneously mixed. Here we report an Au-Ag plasmonic nanocatalyst achieved by plasma restructuring and activation from the sequential preparation. The isolated cationic Au and Ag species on the sequentially-prepared Au-Ag/TiO2 sample are restructured to be homogeneously mixed and highly activated by O2 plasma, which can be partially auto-reduced to Au-Ag bimetallic nanoparticles within the induction period of a few minutes in VL photocatalytic oxidation of CO. The Au-Ag plasmonic nanocatalyst exhibits a strongly enhanced activity in the VL photocatalytic reaction. The contribution of O2 plasma treatment and the enhancement mechanism for the Au-Ag plasmonic nanocatalyst are disclosed.

Preparation and analysis of pyrolysis oils

A critical review of the methods for producing pyrolysis waste oils was carried out, the possibilities and limitations of each approach were discussed. Liquid pyrolysis products (pyrolysis oils) are promising source of valuable chemical compounds, and can be also used as a fuel. A reliable analysis of pyrolysis oils is necessary to study their component composition, basic characteristics and to select the most suitable methods for the extraction of the necessary compounds. It is known that the results of GC-MS analysis of liquid pyrolysis products are usually ambiguous: there are problems of peaks overlapping and incorrect interpretation of the data, due to the complexity of the matrix and the multicomponent composition of the object. The paper presents data on the chemical composition of pyrolysis oils obtained by elemental analysis, IR spectroscopy, NMR spectrometry, GC-MS, GC-GC/MS. Based on the presented results, pyrolysis oil usually contains aromatic compounds, water-soluble substances and hydrocarbons. It was found out that there are conflicting data on the chemical composition of the pyrolysis oils of waste tires in the scientific literature. It is proposed to carry out sequential extraction sample preparation of pyrolysis mixtures to increase the reliability and accuracy of the componential and quantitative composition of the GC-MS method. Obviously, a reliable analysis of complex pyrolysis mixtures without preliminary targeted sample preparation seems unlikely.

Catalytic Systems for the Synthesis of Biscarbonates and Their Impact on the Sequential Preparation of Non-Isocyanate Polyurethanes

The synthesis of non-isocyanate polyurethanes (NIPUs) has recently gained great attention. In this respect, a bifunctional catalyst and an abundant metal catalyst system were investigated for the c...

Optical cellulose fiber made from regenerated cellulose and cellulose acetate for water sensor applications

In this study an optical cellulose fiber for water sensoring was prepared by using a sequential preparation strategy. The core of the fiber was prepared from dissolved cellulose, in [EMIM]OAc, which was dry–wet spun into water. The cladding layer on the cellulose core was produced by coating a layer of cellulose acetate, dissolved in acetone, using a filament coater. The chemical and optical properties of both regenerated cellulose and cellulose acetate were studied from cast films using ultraviolet–visible and Fourier-transform infrared spectroscopy measurements. Regenerated cellulose film was observed to absorb UV light, passing the visible light wavelengths. Cellulose acetate film was observed to pass the whole light wavelength range. The mechanical strength and topography of the prepared optical cellulose fiber were investigated through tensile testing and SEM imaging. The mechanical performance of the fiber was similar to previously reported values in the literature (tensile strength of 120 MPa). The prepared optical fiber guided light in the range of 500–1400 nm. The attenuation constant of the cellulose fiber was observed to be 6.3 dB/cm at 1300 nm. The use of prepared optical cellulose fiber in a water sensor application was demonstrated. When the fiber was placed in water, a clear attenuation in the light intensity was observed. The studied optical fiber could be used in sensor applications, in which easy modifiability and high thermal resistance are beneficial characteristics.Graphic abstractCoaxial cellulose acetate-regenerated cellulose fiber for transporting light in sensor optical fiber sensor applications.

Sequential Preparation of Dual‐Layer Fluorine‐Doped Tin Oxide Films for Highly Efficient Perovskite Solar Cells

A dual-layer fluorine-doped tin oxide (FTO) film has been fabricated by means of sequential spray pyrolysis for high-efficiency perovskite solar cells (PSCs). The H-FTO/L-FTO dual layer film consists of a H-FTO layer prepared at high deposition temperature (≈450 °C) and a L-FTO layer, fabricated at low deposition temperature (≈150 °C), which is used to replace the traditional compact TiO2 /FTO layer. The effects of F/Sn molar ratio, precursor solution concentration, and deposition temperature on the electrical, optical, surface morphological, and grain structural characteristics of H-FTO layers have been studied systematically. With an increase in precursor solution concentration, the mobility and carrier concentration of H-FTO increases; however, the grain size and sheet resistance decreases as the precursor solution concentration increases. A high deposition temperature results in a large grain size and enhanced haze value. The L-FTO layer expresses compact layer growth, inconsistent with the H-FTO surface structure, and possesses excellent electron collection and transport efficiency. The effect of the hole-blocking characteristics of L-FTO on the PSC performance is studied. This study provides a novel dual-layer FTO film to replace the traditional compact TiO2 /FTO layer, which is usually prepared by coating TiO2 precursor on FTO following calcination at 450 °C. The H-FTO/L-FTO dual-layer film can simplify the fabrication process and maintain a high power conversion efficiency (PCE); this results in more efficient electron transportation and blocking of holes. The champion device of PSCs with H-FTO/L-FTO shows the highest PCE of 17.37 % under the illumination of 100 mW cm-2 (AM1.5G).

Hierarchically Structured Porous SnO2/TiO2 Materials with Design Controllable Phases and Enhanced Photocatalytic Activity

To increase the photogenerated carrier separation and reduce the electron-hole recombination process for photocatalysts performance. In this article, hierarchically macroporous structured TiO2/SnO2 materials with controllable composition and phases have been successfully synthesized by using a typical process. This method involves several sequential preparation steps: (1) preparation of core-shell structure SnO2/PS submicrospheres by hydrothermal method; (2) preparation of TiO2/SnO2/PS submicrospheres by assembling amorphous TiO2 on surface of SnO2/PS submicrospheres; (3) direct calcination of TiO2/SnO2/PS submicrospheres to eventually produce hierarchically structured TiO2/SnO2 materials with pores-in-pores. With rutile phases TiO2, TiO2/SnO2 macroporous materials show significantly enhanced catalytic activity when used as photocatalysts for the degradation of Rhodamine B under UV irradiation. The photodegradation ratio of Rhodamine B was 96% for 25 min.

Tandem chalcone-sulfonamide hybridization, cyclization and further Claisen–Schmidt condensation: Tuning molecular diversity through reaction time and order and catalyst

We here report the synthesis of novel chalcone-sulfonamide compounds based on the hybridization at 2′ position and nitro substitution at the side chalcone phenyl ring followed by tandem cyclization into quinolinone derivatives and then a further aldol condensation only as a function of the reaction time. Therefore, for the first time, we have controlled the sequential preparation of chalcone-sulfonamide hybrids, quinolinones and then (E)-3-ene-2,3-dihydroquinolinones simply stopping reaction over increasing time periods. Furthermore, a new molecular scaffold based on a chalcone-(bis)sulfonamide hybrid has been gotten through changing the sequence of coupling reactions and catalyst. This study means practical and useful ways of constructing in high yields new biologically active compounds bearing diversified molecular scaffolds.

“One-pot” sequential preparation of isoquinoline-1,3(2H,4H)-dione derivatives by reacting N-alkyl(aryl)-N-methacryloyl benzamides with benzyl alcohols and sodium benzenesulfinates

Two cascade coupling reactions were developed between N-alkyl(aryl)-N-methacryloyl benzamides and readily available benzyl alcohols or sodium benzenesulfinates. Through a radical cyclization strategy, these one-pot sequential reactions provided two simple and efficient approaches to the synthesis of a variety of isoquinoline-1,3(2H,4H)-dione derivatives in high yields with a broad substrate scope. These compounds are valuable molecules in drug discovery.

Sequential Preparation of Series of Ternary Solutions

For ternary (and more general multicomponent) liquid-phase systems, solution preparation is a necessary step in measuring thermodynamic and transport property data and in identifying compositions useful in specific applications. We consider a ternary system comprised of liquid components A, B, and C (typically, nonelectrolytes), fully miscible over the entire range of composition. Achieving uniform coverage of the ternary triangle of compositions, with mass fraction increments of $$ {1 \mathord{\left/ {\vphantom {1 N}} \right. \kern-0pt} N} $$ corresponding to mass fractions of $$ w_{\text{A}} = {m \mathord{\left/ {\vphantom {m N}} \right. \kern-0pt} N} $$ , $$ w_{\text{B}} = {n \mathord{\left/ {\vphantom {n N}} \right. \kern-0pt} N} $$ , $$ w_{\text{C}} = 1 - w_{\text{A}} - w_{\text{B}} $$ , for $$ 0 \le m \le N $$ and $$ 0 \le m + n \le N $$ , requires preparation of $$ {{(N + 1)(N + 2)} \mathord{\left/ {\vphantom {{(N + 1)(N + 2)} 2}} \right. \kern-0pt} 2} $$ solutions. If the minimum quantity required for each composition is characterized in terms of a volume, as for, say, viscometry, then the volume required, if each solution is prepared directly from pure components, will grow with N more rapidly than quadratically. We develop an approach that mixes previously prepared solutions to make new compositions, and substantially reduces the amount of material needed. We illustrate this approach in detail when the components are liquids with the same density, miscible in all compositions, with no volume change on mixing, and each solution can be fully recovered to prepare subsequent solutions. For $$ N = 10 $$ , only nine units are required, compared to 66 units for the conventional approach, while the number of weighings is reduced by 55%. Modifications to deal with cases in which the pure components have different densities, some material is not recovered after measurement, and the components have different costs, are discussed.

Self-Assembled, Iridescent, Crustacean-Mimetic Nanocomposites with Tailored Periodicity and Layered Cuticular Structure.

Natural high-performance materials inspire the pursuit of ordered hard/soft nanocomposite structures at high fractions of reinforcements and with balanced molecular interactions. Herein, we develop a facile, waterborne self-assembly pathway to mimic the multiscale cuticle structure of the crustacean armor by combining hard reinforcing cellulose nanocrystals (CNCs) with soft poly(vinyl alcohol) (PVA). We show iridescent CNC nanocomposites with cholesteric liquid-crystal structure, in which different helical pitches and photonic band gaps can be realized by varying the CNC/PVA ratio. We further show that multilayered crustacean-mimetic materials with tailored periodicity and layered cuticular structure can be obtained by sequential preparation pathways. The transition from a cholesteric to a disordered structure occurs for a critical polymer concentration. Correspondingly, we find a transition from stiff and strong mechanical behavior to materials with increasing ductility. Crack propagation studies using scanning electron microscopy visualize the different crack growth and toughening mechanisms inside cholesteric nanocomposites as a function of the interstitial polymer content for the first time. Different extents of crack deflection, layered delamination, ligament bridging, and constrained microcracking can be observed. Drawing of highly plasticized films sheds light on the mechanistic details of the transition from a cholesteric/chiral nematic to a nematic structure. The study demonstrates how self-assembly of biobased CNCs in combination with suitable polymers can be used to replicate a hierarchical biological structure and how future design of these ordered multifunctional nanocomposites can be optimized by understanding mechanistic details of deformation and fracture.

Glycosaminoglycan functionalization of mechanically and topologically defined collagen I matrices.

Collagen I and glycosaminoglycans (GAGs) are major components of the extracellular matrix in mammals and widely used for in vitro cell culture matrices. While composition, network microstructure and mechanics of these matrices sensitively determine cell fate, they are hard to adjust independently during matrix reconstitution. We report on a sequential preparation procedure of collagen I matrices, which allows a defined adjustment of network topology and mechanics in combination with GAG functionalization. Collagen I solution concentrations of 1.5 to 7 mg ml-1 allowed to vary topology (pore size) and elasticity of resulting networks with Young's moduli of 5 to 220 Pa. Zero-length crosslinking using carbodiimide chemistry increased Young's modulus 3 to 5 times without changing network topology. An optional covalent binding of hyaluronan and synthetically sulfated hyaluronan to the preformed matrices led to topologically unaffected networks with a stable functionalization with ∼30 μg GAG per mg collagen. While sulfated GAGs were stably attached to collagen I networks via physisorption or covalent binding at neutral and acidic conditions, non-sulfated hyaluronan required acidic conditions and covalent binding for stable attachment. In conclusion, this approach provides options to independently adjust biophysical and biochemical parameters of collagen I networks for in vitro studies.

Fertility desires, choice of hormone replacement and the effect of length of time since menopause on bone density in women with premature ovarian insufficiency: a review of 223 consecutive new referrals to a tertiary centre.

Premature ovarian insufficiency can have significant implications for the affected women. This review assesses the fertility desires, choice of hormone replacement, and the effect of time since menopause on the bone density of these women. This is a retrospective analysis of 223 consecutive new referrals. The average age (mean [± standard deviation]) of the women was 37.35 (± 5.88) years, with 24.1% (n = 19/79) presenting within 12 months of the onset of symptoms, most commonly, vasomotor type symptoms (n = 98/223; 43.9%). Of the women included, 58.7% (n = 131/223) took hormone replacement therapy (HRT), most commonly, an oral (n = 90/131; 68.7%) sequential preparation (n = 91/131; 69.5%), with a significant number of women >40 years of age preferring the transdermal route (n = 26/54; 48.1%; p<0.01). A total of 37.7% (n = 84/223) of the women expressed concerns regarding their future fertility, more notable in women ≤ 40 years (n = 72/142; 50.7%; p < 0.01). Of these, 41.7% (n = 35/84) took HRT, most commonly, a sequential regimen (n = 26/35; 74.3%) with oral estradiol (n = 30/35; 85.7%); 69.5% (n = 155/223) of the women had had a bone densitometry scan performed, with 66.5% (n = 103/155) showing normal bone mineral density (BMD), but a greater likelihood of having reduced BMD the greater the time delay in presentation. No difference was seen for the three broad categories of BMD when further analysed for the cause of premature ovarian insufficiency, but a significant difference was noted for the spinal Z-scores, whereby women who underwent a surgically induced menopause were noted to have lower BMD compared with the other causes (p < 0.01). These findings can be useful in counselling women and guiding clinicians in their management of women with premature ovarian insufficiency.

A standardized and reproducible urine preparation protocol for cancer biomarkers discovery.

A suitable and standardized protein purification technique is essential to maintain consistency and to allow data comparison between proteomic studies for urine biomarker discovery. Ultimately, efforts should be made to standardize urine preparation protocols. The aim of this study was to develop an optimal analytical protocol to achieve maximal protein yield and to ensure that this method was applicable to examine urine protein patterns that distinguish disease and disease-free states. In this pilot study, we compared seven different urine sample preparation methods to remove salts, and to precipitate and isolate urinary proteins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles showed that the sequential preparation of urinary proteins by combining acetone and trichloroacetic acid (TCA) alongside high speed centrifugation (HSC) provided the best separation, and retained the most urinary proteins. Therefore, this approach is the preferred method for all further urine protein analysis.

CompASM: an Amber-VMD alanine scanning mutagenesis plug-in

Alanine scanning mutagenesis (ASM) of protein–protein interfacial residues is a popular means to understand the structural and energetic characteristics of hot spots in protein complexes. In this work, we present a computational approach that allows performing such type of analysis based on the molecular mechanics/Poisson– Boltzmann surface area method. This computational approach has been used largely in the past and has proven to give reliable results in a wide range of complexes. However, the sequential preparation and manual submission of dozens of files has been often a major obstacle in using it. To overcome these limitations and turn this approach user-friendly, we have designed the plug-in CompASM (computational alanine scanning mutagenesis). This software has an easy-to-use graphical interface to prepare the input files, run the calculations, and analyze the final results. CompASM was built in TCL/TK programming language to be included in VMD as a plug-in. The CompASM package is distributed as an independent platform, with script code under the GNU Public License from http://compbiochem.org/Software/compasm/Home.html.

In Vitro Canal and Isthmus Debris Removal of the Self-Adjusting File, K3, and WaveOne Files in the Mesial Root of Human Mandibular Molars

IntroductionThe purpose of this study was to compare the effectiveness of debris removal between the Self-Adjusting File (SAF), WaveOne, and K3 file systems in the mesial roots of mandibular molars. In addition, the SAF was tested as a potential adjunct after instrumentation with other systems. MethodsThe mesial roots of 30 extracted mandibular molars were mounted in resin by using the K-Kube, sectioned at 2 and 4 mm from working length, and randomly placed into 3 groups: K3 group, sequential preparation with K3 files to an apical size of 35/.04; WaveOne group, preparation with WaveOne primary file; and SAF group, preparation with SAF. Images were taken before instrumentation, after instrumentation, after final irrigation, and after SAF adjunct irrigation. A cleanliness percentage was calculated by using interactive software. Comparisons between groups were analyzed with repeated-measures analysis of variance and post hoc tests (P < .05). ResultsThere was no significant difference in canal cleanliness among the groups, but the WaveOne was significantly worse for isthmus cleanliness. Use of the SAF as an adjunct only significantly improved canal cleanliness in the K3 group at the 2-mm level by an average of 1.7%. ConclusionsThere was no difference in canal cleanliness between the 3 file systems; however, the SAF and K3 files performed significantly better than the WaveOne with respect to isthmus cleanliness. When used as a final irrigation adjunct device after instrumentation, the SAF provided a significant improvement only in a subset of the K3 group.

Synthesis and characterization of new biodegradable comb‐dendritic triblock copolymers

AbstractA series of well‐defined dumbbell‐shaped triblock copolymers consisting of linear poly(ethylene glycol) (PEG) and comb‐like poly(ε‐caprolactone) (PCL) with varied PCL arm lengths have been synthesized via the sequential preparation of different generation terminal dendronized PEG and ring‐opening polymerization of ε‐caprolactone. The copolymers were characterized using Fourier transform infrared, 1H NMR and 13C NMR spectroscopy and gel permeation chromatography. Differential scanning calorimetry was performed to measure the glass transition temperature, melting point and degree of crystallinity and the PEG segment and PCL segment crystallization temperatures. The crystallization of the copolymers was also studied using X‐ray diffraction. The dumbbell‐shaped copolymers were further used to construct microspheres using a double emulsion method. Scanning electron microscopy and dynamic light scattering results showed the size of the microspheres was about 2 to 4 µm and the size distribution was quite narrow. Copyright © 2012 Society of Chemical Industry

ChemInform Abstract: Indium‐Catalyzed Reductive Esterification of a Carboxylic Acid: Sequential Preparation of an Ester and Symmetrical Ether.

AbstractReductive dimerization of aliphatic carboxylic acids with triethylsilane in the presence of InBr3—H2SO4 catalyst provides access towards carboxylic esters (II) and (V).

Synthesis of CaCO3 nanoparticles via citrate method and sequential preparation of CaO and Ca(OH)2 nanoparticles

AbstractCalcium carbonate nanoparticles were synthesized via so‐called sol–gel citrate method using calcium nitrate as precursor in presence of different concentration of citric acid, selected to be 0.0, 0.5, 1.25 and 2.5 times of the concentration of the precursor, on calcining at 600 °C for 5 h. Stable phase of the calcite is formed in presence of citric acid. The roles of organic additive concentration, calcination temperature and sonication on the particle size of the products were investigated. Calcium oxide nanoparticles were prepared by facial calcination of the resulted product at 900 °C for 5 h. Calcium hydroxide nanoparticles, however, were synthesized on sonication of the product for 20 min in water at room temperature. Samples were characterized by XRD and FT‐IR studies. Crystallite size of samples was calculated by XRD data and was measured by TEM analysis. The specific surface are (SSA) of samples was calculated by the XRD data and compared by the measured BET. (© 2012 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)