Facile formation of stimuli-responsive,fluorescent and magnetic nanoparticles based on cellulose stearoyl ester via nanoprecipitation

In comparison to stimuli-responsive, multi-functional nanoparticles (NPs) from synthetic polymers, such NPs based on sustainable, naturally occurring polysaccharides are still scarce. In the present study, stable stimuli-responsive, fluorescent and magnetic NPs were fabricated using cellulose stearoyl esters (CSEs) consisting of cellulose and stearoyl groups. The multifunctional NPs with the average diameters between 80 and 250 nm were obtained after facile nanoprecipitation using CSE solutions containing Fe₃O₄-NPs. Using the aqueous solution of fluorescent rhodamine B as precipitant, NPs with rhodamine B on NP surface were obtained. Rhodamine B could be released depending on the temperature. In comparison, stearoylaminoethyl rhodamine B can be encapsulated in CSE-NPs, which renders obtained NPs reversible fluorescence in response to UV illumination and heat treatment.     

Impact of PS/SiO2 morphologies on the SERS activity of PS/SiO2/Ag nanocomposite particles

To understand the relationship between the morphology of carboxyl-functionalized polystyrene/silica (PS/SiO₂) nanocomposite microspheres and the surface-enhanced Raman scattering (SERS) performance of PS/SiO₂/Ag nanocomposite particles, core-shell and raspberry-like PS/SiO₂ composite microspheres were used as templates to prepare PS/SiO₂/Ag nanocomposite particles. The core-shell and raspberry-like structured PS/SiO₂ templates were prepared via in situ sol-gel reaction by hydrolysis tetraethyl orthosilicate (TEOS) in alkali solution. Silver nanoparticles (10–50 nm) were loaded on the PS/SiO₂ templates’ surface by chemical reduction. The morphology and structure of the PS/SiO₂/Ag particles were characterized by TEM, SEM, X-ray diffraction (XRD), and ultraviolet-visible (UV-vis) spectroscopy. Rhodamine 6G (R6G) was selected as a model chemical to study the enhancement performance of substrate constructed by PS/SiO₂/Ag nanocomposite. Results indicated that the PS/SiO₂/Ag nanocomposite prepared based on the core-shell templates showed higher SERS activity. The beneficial effect was associated with a lower specific area of core-shell structure and the larger average diameter of nanosilvers than that of the raspberry-like templates.     

Polyoxotungstate nanoclusters supported on silica as an efficient solid-phase microextraction fiber of polycyclic aromatic hydrocarbons

A highly porous silica-supported tungstophosphoric acid (PW) nanocluster was prepared for use in solid-phase microextraction (SPME) of polycyclic aromatic hydrocarbons (PAHs). The PWs represent a class of discrete transition metal-oxide nanoclusters and their structures resemble discrete fragments of metal-oxide structures of definite size and shape. Transition metal-oxide nanoclusters display large structural diversity, and their monodisperse sizes can be tuned from several Ångstroms up to 10 nm. The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The nanomaterial was immobilized on a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS. Analytical merits include limits of detection that range from 0.02 to 0.1 pg mL^?1 and a dynamic range as wide as from 0.001 to 100 ng mL^?1. Under optimum conditions, the repeatability for one fiber (n?=?3), expressed as the relative standard deviation, is between 4.3 % and 8.6 %. The method is simple, rapid, and inexpensive. The thermal stability of the fiber and the high relative recovery make this method superior to conventional methods of extraction.

The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS.     

Quantum mechanics and the structure of noble-gas clusters

The importance of quantum mechanics for the thermal behaviour of Argon clusters with special respect to phase transitions is investigated applying a Path-Integral Monte-Carlo (PIMC) method. Results for the small-angle neutron scattering function (SANS) for various cluster sizes and temperatures are presented.     

Largely enhanced molecular orientation and mechanical property of injection-molded high-density polyethylene parts via the synergistic effect of polyamide 6 in situ microfibrillar and intense shear flow

The high-density polyethylene (HDPE)/polyamide 6 (PA6) in situ microfibrillar composites (HAM-C) were fabricated by the “extrusion-hot stretch-quenching” technique, in which PA6 microfibrillar had diameters lying in the range 0.55 to 1.05 μm. Then the HAM-C and pure HDPE were processed by multi-melt multi-injection molding (MMMIM). The effect of PA6 in situ microfibrillar and secondary melt penetration on the crystalline morphologies and mechanical properties was investigated using a variety of characterization techniques including differential scanning calorimetry (DSC), rheological experiments, scanning electron microscopy (SEM), synchrotron two-dimensional small-angle X-ray scattering (SAXS), and tensile testing. It was found that PA6 microfibrillar not only acted as a heterogeneous nucleation agent, but also prolonged the relaxation time of HDPE matrix by suppressing the mobility of HDPE molecular chains. It was revealed, from observing the morphologies, that the presence of PA6 microfibrillar not only facilitated the formation of transcrystalline superstructures on its surface, but also induced much more oriented crystals nearby as a result of the amplified local shear field. Furthermore, SAXS results confirmed that the degree of orientation of the injection-molded HAM-C part (HAM-M) was largely enhanced. Finally, the tensile testing showed that the tensile strength and Young’s modulus of the HAM-M sample were enhanced by 38.8 and 54.6 %, respectively, when compared with pure HDPE parts. This work provides a promising way to tailor the crystalline structure of the injection-molded parts.     

Heat of reaction and curing of epoxy resin

The heat of reaction and kinetics of curing of diglycidyl ether of bisphenol-A (DGEBA) type of epoxy resin with catalytic amounts of ethylmethylimidazole (EMI) have been studied by differential power-compensated calorimetry as a part of the program for the study of process monitoring for composite materials. The results were compared with those from 1∶1 and 1∶2 molar mixtures of DGEBA and EMI. A method of determination of heat of reaction from dynamic thermoanalytical instruments was given according to basic thermodynamic principles. The complicated mechanism, possibly involving initial ionic formation, has also been observed in other measurements, such as by time-domain dielectric spectroscopy. The behavior of commercially available DGEBA resin versus purified monomeric DGEBA were compared. The melting point of purified monomeric DGEBA crystals is 41.4 °C with a heat of fusion of 81 J/g. The melt of DGEBA is difficult to crystallize upon cooling. The glass transition of purified DGEBA monomer occurs around ?22 °C with aΔC _p of 0.60 J/K/g.     

Structural and thermal properties of HDPE/n-AlN polymer nanocomposites

High-density polyethylene (HDPE) containing various volume fractions (0–20 vol%) of aluminum nitride nanoparticles (n-AlN) is prepared by melt mixing. Structural and morphological characterizations of the prepared composites are carried out by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and atomic force microscopy (AFM). Thermal stability and degradation kinetics of HDPE/AlN (nano) composites are investigated by Thermogravimetric analysis (TG). HR-TEM micrographs confirm fairly uniform dispersion of AlN nanoparticles, as well as the existence of long interconnected chain-like aggregates. AFM images also confirm homogeneous dispersion of n-AlN in the polymer matrix. Roughness analysis from the AFM data indicates the presence of substantial undulation from the mean surface level. Thermogravimetric data indicate small improvement in the thermal stability of the composites. Kinetic parameters, viz., the activation energy (E _a), frequency factor (A), and reaction order (n) are estimated using the isoconversional methods of Kissinger, Flynn–Wall–Ozawa (FWO), KAS, and Friedman. Activation energies (E _a) calculated by the above four models display nearly similar features and are enhanced by the presence of AlN nanoparticles. Kinetics of degradation of HDPE-AlN (nano) composites follows a first-order reaction.     

Hazard analysis of tetrahydrofuran and dimethylsulfoxide mixture solvents for efficient use in reaction processes

Organic solvents are often used in mixture solvent systems to optimize synthetic reactions. However, they may also produce unexpected effects, some of which may be hazardous and cause a runaway reaction and/or lead to an accident. Thus, the proper accident scenarios and thermal risk assessment models are needed to use mixture solvents more safely and efficiently. For chemical process safety, Stoessel suggests the systematic assessment of accident scenarios. However, if scenarios are changed by the properties of mixture solvents, Stoessel’s concept does not cover them. Our previous study evaluated characteristic scenarios of mixture solvents based on Stoessel’s model. In this study, as a characteristic scenario pattern, we focused on the energy release of the solvent and the material derived from degraded solvent and investigated them experimentally using tetrahydrofuran (THF) and dimethylsulfoxide (DMSO) as a representative mixture solvent. From hazard and scenario identification of THF and DMSO, we assumed that THF peroxide and DMSO play roles in energy release. THF containing peroxide and DMSO were mixed, and thermal analysis and chemical composition analysis were performed. Our results indicated that DMSO promotes the decomposition of THF peroxide, and the decomposition temperature of DMSO decreases upon mixing with degraded THF. Therefore, we verified the scenario pattern of energy release of solvent and the material derived from degraded solvent.     

A photoionization study of the van der Waals molecule C2H4 · HCl

The dissociation energy of the C₂H₄ · HCl van der Waals complex was determined to be 3.18±0.73 kcal mol^?1 by a dissociative photoionization technique. C₂H₄ · HCl was produced by free expansion of a 1:4 mixture of C₂H₄ in HCl and the clusters were ionized with tunable synchrotron radiation. The photoionization efficiency function of (C₂H₄ · HCl)⁺ from C₂H₄ · HCl was determined between 600 and 1,300 Å and the onset for (C₂H₄ · HCl)⁺ was established as 1,163±2 Å = 10.66±0.02 eV; these values give ΔH _f ⁰ (C₂H₄ · HCl) = ?10.7±0.7 kcal mol^?1 and ΔH _f ⁰ (C₂H₄·HCl⁺)=235.1±0.9 kcal mol^?1. A complex ion dissociation energyD ₀(C₂H₄ · HCl⁺) = ?0.3±0.9 kcal mol^?1 was calculated from the results. The major features on the PIE curve for C₂H₄ · HCl⁺ can be analyzed in terms of the known energetic features of C₂H ₄ ⁺ and HCl. An extended energy diagram for the C₂H₄ + HCl system is presented.     

Thermal decomposition of polymethylmethacrylate synthesized with anionic catalysts

TG and DTA data are used to show that the thermal decomposition of polymethylmethacrylate (PMMA) synthesized with anionic catalysts depends on the nature of the catalyst. It is found that the thermal stability of PMMA obtained by using anionic amide catalysts is higher than that of radical PMMA and of PMMA obtained with other anionic catalysts, and depends on the temperature of polymerization and on the molecular weight of the polymer.     

Mechanism and improvement of complex formation between LPS and polymyxin B that is immobilized on an ion exchanger

Polymyxin B was immobilized on the ion exchanger, Amberlite IRC-50. The modified support was used as an adsorbent for lipopolysaccharide ofE. coli from a phosphate buffer at pH = 7.0 and T = 20°C. The insertion of a spacer, 6-amino hexanoic acid, improved the adsorption capacity of the modified carrier significantly. Upon partial acetylation (25%) of primary amino groups of immobilized Polymyxin B, the adsorption capacity of the support was halved. From our results, it is concluded that the complex formation between lipopolysaccharide and immobilized Polymyxin B is based on both lipophilic, as well as electrostatic, interactions. Convenient procedures for the immobilization of the ligands and the characterization of the ion exchanger are described.     

Visual detection of arginine,histidine and lysine using quercetin-functionalized gold nanoparticles

We report on the use of quercetin-functionalized gold nanoparticles (QC-AuNPs) as a colorimetric probe for the amino acids arginine (Arg), histidine (His) and lysine (Lys). The method is based on the aggregation of the QC-AuNPs that is caused by these amino acids and leads to a visually detectable color change from red to blue. The absorption maxima shift from 525 nm to 702, 693, and 745 nm, respectively. Aggregations are confirmed by dynamic light scattering (DLS) and transmission electron microscopic techniques (TEM). The effects of the QC concentration, temperature and reaction time for the preparation of QC-Au NPs were tested. Other amino acids do not interfere. Under the optimal conditions, linear relationships exist between the absorption ratios at 702/525 nm (for Arg), 693/525 nm (for His), and 745/525 nm (for Lys) over the concentrations ranges from 2.5–1,250 μM (Arg) and 1–1,000 μM (His and Lys), respectively. The respective limits of detection are 0.04, 0.03, and 0.02 μM. The method provides a useful tool for the rapid visual and instrumental determination of the three amino acids. Figure

We report the use of quercetin as novel reagent for preparation and functionalization of gold nanoparticles to colorimetric sensing of three aminoacids (arginine, histidine and lysine). This is based on the aggregation of QC-AuNPs induced by three aminoacids.     

Functionalization of cellulose with epoxy groups via γ-initiated RAFT-mediated grafting of glycidyl methacrylate

Glycidyl methacrylate (GMA), was grafted from cellulose by the combination of radiation-induced initiation and the reversible addition-fragmentation chain transfer (RAFT) polymerization technique, leading to epoxy functionalized surfaces that enable further modifications. Cumyl dithiobenzoate and 2-cyanoprop-2-yl dithiobenzoate were employed as the RAFT agents. The effects of absorbed dose, monomer and RAFT agent concentrations and solvent choice on grafting yield were investigated. Characterization of the synthesized copolymers by ATR-FTIR spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, thermal analysis and contact angle measurements revealed the grafting of poly(glycidyl methacrylate) (PGMA) from cellulose. Size-exclusion chromatography analysis indicated the difficulty of controlling the polymerization of GMA due to branching and/or crosslinking reactions that might occur in PGMA structure under γ-radiation.     

Phosphatase activities of fractions of the venom of Renard's viperVipera ursini renardi

The separation of the venom of Renard's viper by filtration through Sephadex G-75 gel has been performed and phosphatase activities have been determined in the fractions and in the course of separation. The bulk of the activity of the phosphatases investigated was concentrated in the high-molecular-weight fractions I and II. A correlation has been found in the distribution of the DNase and ATP-pyrophosphatase activities with the phosphodiesterase activity in the venom fractions. There is no correlation in the distribution of the RNase and phosphodiesterase activity.     

Photochemical synthesis of perfluoropolyether (PFPE) nanocomposites containing PFPE oligomer stabilized magnetite nanoparticles

Magnetite nanoparticles were synthesized and their post-synthesis surface modification was carried out with triethoxy terminated perfluoropolyether (PFPE) oligomers. The surface-treated nanoparticles were then dispersed in a UV-curable difunctional methacrylic PFPE oligomer. Thin films prepared from the resulting stable suspensions were photopolymerized. The obtained nanocomposites showed good distribution of the surface-treated magnetite nanoparticles in the polymer matrix. The surface treatment of magnetite nanoparticles with perfluoropolyether oligomers thus was found to be effective in preventing nanoparticle segregation and aggregation, ensuring therefore an increased compatibility with the PFPE matrix.     

Isolation and purification of biopolymers by affinity chromatography. VI. Preparation and properties of an affinity adsorbent with a polysaccharide spacer for the purification of proteolytic enzymes

A new affinity sorbent has been synthesized — soybean trypsin inhibitor (STI)-amylopectin-hydrazidosuccinyl-Sepharose — and its properties have been studied in comparison with those of an analogous adsorbent without the spacer STI-Sepharose. The STI-amylopectin-hydrazidosuccinyl-Sepharose adsorbent has been used for the purification of trypsin from porcine pancreas and of callicrein from human blood plasma.     

SDS 800 — The new data system for quantitative depth profiling of inhomogeneous samples by SIMS

More than 13 years of SIMS application field experience of numerous users of the ATOMIKA Ionmicroprobes have been the basis for the new SIMS Data System SDS 800. The hardware and software concept of the SDS 800, therefore, pays special attention to the following requirements:

1. Convenient set-up, modification and re-use of the measuring parameter sets for easy, time-saving operation.
2. Individual parameter selection from the very broad range of SIMS measuring parameters for optimum SIMS data quality.
3. Multitasking operation for simultaneous handling of SIMS measurement, data processing, data output and of auxiliary techniques.
4. Simultaneous depth profile/ion image acquisition and processing to enhance data quality and to validate data interpretation.
5. User-friendly data processing and output.

     

The role of octanol in the extraction of hydrochloric acid by trilaurylamine dissolved in benzene

The extraction of hydrochloric acid by trilaurylamine (TLA) dissolved in benzene was studied in the presence and in absence of n-octanol. The extraction of HCl was found to be enhanced by the addition of octanoi to the organic phase. In order to explain this effect by means of the law of mass action, the systems TLA-HCL-benzene and n-octanol-HCl-benzene as well as TLA-octanol-benzene were also studied. It was found that TLA reacts with octanol to form a complex, TLAROH, while the octanol itself associates in benzene to form dimers and tetramers, although it does not extract HCl alone from the dilute solutions used in the present study. The enhancement of the extraction of HCl by TLA upon the addition of n-octanol could be described by the formation of the species TLA·ROH·HCl and its stability constant was determined.     

Coupling of effector molecules to solid supports

In view of the limited stability of the isourea bond, formed in ligand coupling to CNBractivated polysaccharides, an alternative to this current activation method has been developed. 2,4,6-Trifluoro-5-chloropyrimidine (FCP), known as a reactive group in reactive dyes, was used to activate Sepharose. Under appropriate conditions a thermally stable product with unimpaired beaded structure was obtained, which was reactive toward amines and mercaptans. Coupling with hexamethylenediamine, aniline, and ethanethiol, respectively, yielded an incorporation of 0.2-2.7, 0.9-1.7, and 1.1 mmol ligand/g dry agarose. The stability of immobilized ligands based on FCP-Sepharose between pH 4 and 8 was about 200 times higher as compared to products originating from CNBr-Sepharose; ligand leakage was only 0.5 x 10^p-3%/h. The possibility of obtaining a high degree of substitution is a further advantage of the FCP activation. In addition, the FCP-activated Sepharose can be stored in the wet state at 4°C without substantial decrease in coupling capacity. The FCP analogs 2,4,5,6-tetrachloro- and 2,4,5,6-tetrafluoropyrimidine, and other polymers (cellulose, Sephadex, aminomethylpolystyrene) appeared to be applicable also.