Functional nanoscale additives for ultra-durable powder-coating polymers

Abstract  

Surface-modified titania nanoparticles were prepared and their suitability as additives for the long-term UV-photoprotection of polymer materials was investigated. It was demonstrated that the functionalization of nano-TiO₂ with different fatty acid and phosphonate-based grafting reagents has a beneficial effect on the long-term stability of polyester composites under accelerated weathering conditions. These results are of considerable interest for the development of robust organic–inorganic hybrid systems that can be utilized as transparent but UV-resistant protective layers for outdoor applications.     

Computational NQR study of a boron nitride nanocone

Abstract  

The electronic structure of a boron nitride nanocone with 240° disclination, and some properties that derive from this structure, were studied by density-functional theory calculations. In the considered model there are only hexagonal rings, with the apex and mouth of the nanocone saturated by hydrogen atoms. The model was optimized, and then the nuclear quadrupole resonance parameters were calculated at the sites of ¹¹B and ¹⁴N nuclei. The results revealed that the nuclei in the boron nitride nanocone are divided into layers with similar electronic properties. The nuclei at the apex and mouth are very important for the electronic behavior of the nanocone, with ¹¹B playing the major role.     

Applications of biopolymers I: chitosan

Abstract  

Chitosan is prepared from chitin, the second most abundant natural polymer in the world. It is primarily composed of glucosamine and N-acetyl glucosamine residues with a 1,4-β-linkage. It can be obtained by deacetylation of chitin, which is produced from shells of crustaceans, insects, and other sources. Chitosan is a nontoxic, biodegradable, and biocompatible natural polymer and can be used in a wide range of applications such as in the areas of biomedicine, membranes, drug delivery systems, hydrogels, water treatment, food packaging, etc. In this paper, some novel applications of this biopolymer in different fields are reviewed.     

Biomimetic PLGA sensor: proof of principle and application

Abstract  

Spoilage of products can mainly be attributed to microorganisms which “live on the product”, i.e. which are able to utilize and/or metabolize components and/or molecules of the product. The objective of this work was to develop and optimize sensor prototypes indicating the quality of a product “in real time”, i.e. at the time the consumer is looking at the product. The design of the presented sensors relates to optical phenomena, for example anomalous absorption and remission of light. The crucial point of the sensor prototypes is a layer sensitive to the analyte, a polymer degradable by enzymes produced by the respective microorganisms. After incubation of the sensor setup with contaminated products, the lytic enzymes released from decaying cell material change the thickness of the polymer layer and generate a colour change visible by the naked eye. Production of the sensor prototypes is very simple and inexpensive and they might be successfully integrated into product packaging.     

Baltimore PM2.5 Supersite: highly time-resolved organic compounds—sampling duration and phase distribution—implications for health effects studies

As part of the Baltimore PM2.5 Supersite study, intensive three-hourly continuous PM2.5 sampling was conducted for nearly 4 weeks in summer of 2002 and as well in winter of 2002/2003. Close to 120 individual organic compounds have been quantified separately in filter and polyurethane foam (PUF) plug pairs for 17 days for each sampling period. Here, the focus is on (1) describing briefly the new sampling system, (2) discussing filter/PUF plugs breakthrough experiments for semi-volatile compounds, (3) providing insight into phase distribution of semi-volatile organic species, and (4) discussing the impact of air pollution sampling time on human exposure with information on maximum 3- and 24-h averaged ambient concentrations of potentially adverse health effects causing organic pollutants. The newly developed sampling system consisted of five electronically controlled parallel sampling channels that are operated in a sequential mode. Semi-volatile breakthrough experiments were conducted in three separate experiments over 3, 4, and 5 h each using one filter and three PUF plugs. Valuable insight was obtained about the transfer of semi-volatile organic compounds through the sequence of PUF plugs and a cut-off could be defined for complete sampling of semi-volatile compounds on only one filter/PUF plug pair, i.e., the setup finally used during the seasonal PM2.5 sampling campaign. Accordingly, n-nonadecane (C19) with a vapor pressure (vp) of 3.25 × 10⁻⁴ Torr is collected with > 95% on the filter/PUF pair. Applied to phenanthrene, the most abundant the PAH sampled, phenanthrene (vp, 6.2 × 10⁻⁵ Torr) was collected completely in wintertime and correlates very well with three-hourly PM2.5 ambient concentrations. Valuable data on the fractional partitioning for semi-volatile organics as a function of season is provided here and can be used to differentiate the human uptake of an organic pollutant of interest via gas- and particle-phase exposure. Health effects studies often relay on PM2.5 exposure measurements taken over 24 h or longer. We found that maximum 3-h concentrations are frequently two to five times higher than that found for maximum 24-h concentrations, an important aspect when considering that short-term exposure to higher air pollution levels are more likely to overpower defense mechanisms in the human lung with subsequent adverse effects even at lower pollutant levels.     

Study of polyaniline conducting/electroactive polymer as sensor for some agricultural phosphorus pesticides

Abstract  

Due to their wide applications as insecticides, pesticides, chemical warfare agents, etc., detection of organophosphorus compounds is of great importance. This paper deals with application of polyaniline conducting polymer (PANi) as a sensor material for detection of some agricultural organophosphorus compounds that are commonly used as insecticides and pesticides. The compounds employed in this investigation are dichlorvos, trichlorophon, and chlorpyrifos. The effects of some important parameters such as concentration, thickness of the polymer film, etc., on electrical conductivity and conductivity stability for these compounds have also been investigated. In situ electrical conductivity measurements were performed using a standard direct-current (DC) four-point probe technique. It was found that adsorption and desorption of these compounds on PANi film cause measurable change in the resistance of conducting polymers.     

Analysis of ketone‐based neurosteroids by reactive low‐temperature plasma mass spectrometry

Rationale

Neurosteroids are important signalling molecules that modulate neuronal activity. Their low concentrations and low volatility make neurosteroid detection and quantification by ambient mass spectrometry challenging. Here we develop a reactive low‐temperature plasma mass spectrometry (LTP‐MS) method and demonstrate its potential for fast screening and quantification of neurosteroids in mouse brain.

Methods

Ketone‐based neurosteroids were analysed with the LTP‐MS method. The plasma of the LTP was heated in order to improve the desorption efficiency of low‐volatility neurosteroids. Methylamine with a concentration of 500 ppbv was employed as the reactive reagent. Neurosteroids in mouse brain tissue extracts were detected in 70 s with mass errors less than ±3 ppm due to coupling of the ion source with a high‐performance mass spectrometer.

Results

Reaction between neurosteroids and methylamine, seeded into the LTP gas stream, resulted in the formation of protonated methylamine–neurosteroid adducts with 5‐ to 100‐fold abundances, compared to [M + H]⁺ ions detected in non‐reactive LTP‐MS. The lowest detectable concentrations of neurosteroid standards were in the range of ng/mL. Concentrations of neurosteroids in male and female mouse brain extracts as determined with reactive LTP‐MS were on the level of ng/g, comparable to results obtained with high‐performance liquid chromatography–tandem mass spectrometry.

Conclusions

The developed reactive LTP‐MS is capable of providing sensitive identification and quantification of ketone‐based neurosteroids in mouse brain extracts with minimal sample treatment, and showcases the potential of reactive LTP‐MS as a tool for fast screening of neurosteroid levels in brain.

     

Content of micronutrients,mineral and trace elements in some Mediterranean spontaneous edible herbs

Background

The analysis of mineral elements composition was determined in three wild edible herbs (Cichorium intybus L., Sonchus asper L. and Borago officinalis) collected in seven different sampling sites which were characterized by different pollution grade. The detection of mineral elements (Ca, K, Mg and Na), micronutrients (Cu, Fe, Li, Mn and Zn) and heavy metals (As, Cd, Hg, Ni and Pb) was performed.

Results

The results obtained show that in most cases a direct relationship appeared between the amount of elements and the sampling sites. The highest concentrations of heavy metals were found in samples grown in polluted soils. These evaluations showed that contaminants in plants may reflect the environmental state in which they develop.

Conclusion

The examined species are a good source of mineral elements and micronutrients, making them particularly adapt to integrate a well-balanced diet. The accumulation of heavy metals showed that contaminants in plants may reflect the environmental state in which they develop. Results showed high concentrations of heavy metals in samples taken in locations characterized by high human activity and in some samples from the local market, of which no one knows the collection area.

     

Evaluation of in vivo solid phase microextraction for minimally invasive analysis of nonvolatile phytochemicals in Amazonian plants

Introduction

Although solid phase microextraction (SPME) has been used extensively for fingerprinting volatile compounds emitted by plants, there are very few such reports for direct insertion SPME. In this research, direct contact of SPME probes with the interstitial fluid of plants was investigated as a method for phytochemical analysis.

Objective

Medicinal plants from the Amazon have been the source of numerous drugs used in western medicine. However, a large number of species used in traditional medicine have not been characterized chemically, partly due to the difficulty of field work. In this project, the phytochemical composition of plants from several genera was fingerprinted by combining convenient field sampling by solid phase microextraction (SPME) with laboratory analysis by LC-MS. The new method was compared with classical sampling followed by liquid extraction (LE).

Methodology

SPME probes were prepared by coating stainless steel wires with a mixture of polyacrylonitrile and either RP-amide or HS-F5 silica particles. Sampling was performed by inserting the microextraction probes into various tissues of living plants in their natural environment. After in vivo extraction, the probes were sealed under vacuum and refrigerated until analyzed. The probes were desorbed in mobile phase and analyzed on a Waters Acquity UPLC with triple quadrupole mass spectrometer in positive ion mode.

Results

Twenty Amazonian plant species were sampled and unique metabolomic fingerprints were obtained. In addition, quantitative analysis was performed for previously identified compounds in three species. Comparison of the fingerprints obtained by in vivo SPME with those obtained by LE showed that 27% of the chromatographic features were unique to SPME, 57% were unique to LE, and 16% were common to both methods.

Conclusion

In vivo SPME caused minimal damage to the plants, was much faster than traditional liquid extraction, and provided unique fingerprints for all investigated plants. SPME revealed unique chromatographic features, undetected by traditional extraction, although it produced only half as many peaks as ethanol extraction.     

聚合物孔材料的制备*

聚合物孔材料的制备和应用研究已经成为聚合物科学和材料科学热点,制备聚合物孔材料的方法发展很快。本文综述了聚合物孔材料的制备方法,包括胶体晶模版法、水模版法、超临界二氧化碳发泡法、自组装法等。其中本课题组首次提出的无模版自组装法操作简单、无需模版、环境友好,具有广阔的发展前景。     

Method of micro-sampling human dentine collagen for stable isotope analysis

Rationale

Sampling of dentine for stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope ratios in the direction of tooth growth allows the study of temporal changes to the diet and physiological stress of an individual during tooth formation. Current methods of sampling permanent teeth using 1 mm increments provide temporal resolution of 6–9 months at best depending on the tooth chosen. Although this gives sufficient sample sizes for reliable analysis by mass spectrometry, sectioning the dentine across the incremental structures results in a rolling average of the isotope ratios. A novel method of incremental dentine collagen sampling has been developed to decrease the collagen increment size to 0.35 mm along the incremental structures, thus reducing averaging and improving the temporal resolution of short-term changes within the δ¹³C and δ¹⁵N values.

Methods

This study presents data for a MicroMill-assisted sampling method that allows for sampling at 0.35 mm width × 1 mm depth increments following the incremental growth pattern of dentine. A NewWave MicroMill was used to sample the demineralised dentine section of modern donated human third molars from Sudan and compared to data from the same teeth using the 1 mm incremental sectioning method 2 established by Beaumont et al.

Results

The δ¹³C and δ¹⁵N isotopic data showed an increased temporal resolution, with each increment providing data for 2–4 months of dentine formation.

Conclusions

The data show the potential of this method for studying dietary reconstruction, nutritional stress, and physiological change with greater temporal resolution potentially to seasonal level and with less attenuation of the δ¹³C and δ¹⁵N values than was previously possible from human dentine.

     

A polymer inclusion membrane based on the ionic liquid trihexyl(tetradecyl)phosphonium chloride and PVC for solid–liquid extraction of Zn(II) from hydrochloric acid solution

Abstract  

Extraction of Zn(II) from aqueous solution using polymer inclusion membranes based on poly(vinyl chloride) containing the phosphonium-based ionic liquid trihexyl(tetradecyl)phosphonium chloride (Cyphos^? IL 101) is described. Zn(II) could efficiently be extracted from 5 M hydrochloric acid solution with membranes containing 30 wt% Cyphos IL 101, whereas back-extraction was successfully achieved with 1 M sulfuric acid. Prepared membranes were evaluated in terms of stability in air as well as in terms of leaching of the ionic liquid from the membranes in aqueous solution.     

Organo-modified mesoporous silica for sorption of carbon dioxide

Abstract  

Organo-modified mesoporous silica SBA-15 has been studied for sorption of carbon dioxide (CO₂). The SBA-15 sample was functionalized with a branched chain polymer, polyethylenimine (PEI), of different molecular weights (1,300 and 2,000 g mol⁻¹). Surface modification was carried out by impregnation of silica by PEI or by grafting with (3-chloropropyl)triethoxysilane, followed by substitution of chlorine atoms by PEI ligands. The prepared modified mesoporous materials were characterized by nitrogen adsorption/desorption at 77 K, high-resolution transmission electron microscopy, small-angle X-ray scattering, and thermal methods. Sorption of CO₂ was studied by gravimetric method at 303 K. The total amount of sorbed CO₂ varied between 0.19–0.67 mmol/g for respective samples. Regeneration of the materials after adsorption was achieved by thermal treatment at 343 K.     

Screening of conditions controlling spectrophotometric sequential injection analysis

Background  

Despite its potential benefits over univariate, chemometrics is rarely utilized for optimizing sequential injection analysis (SIA) methods. Specifically, in previous vis-spectrophotometric SIA methods, chemometrically optimized conditions were confined within flow rate and reagent concentrations while other conditions were ignored.     

Metal Nanoparticles on Polymer Surfaces: 1. A New Method of Determining Glass Transition Temperature of the Surface Layer

New experimental approach allowing to study the structure and properties of polymer surface layers at a nanolevel is proposed. According to this method, metal nanoparticles are first adsorbed on a polymer surface from colloidal solution, then resultant system is stepwise annealed, and the particle embedding in a polymer is examined with atomic force microscope. Potentialities of the method are demonstrated using the gold nanoparticles–polystyrene system (including polystyrene modified with the UV radiation) as an example. It was established that the glass transition temperature of polystyrene surface layer is noticeably lower compared with the bulk value and decreases even more after the UV modification of a polymer surface. Possible use of the results obtained for the solution of other, independent problem, namely for the creation of two-dimensional nanocomposites by embedding nanoparticle monolayer ensemble in the surface layer of a glassy polymer at a temperature lower than the glass transition temperature of its bulk is analyzed.     

Polymer Brushes by the “Grafting to” Method

This paper focuses on the attachment of densely grafted polymer layers (polymer brushes) to various inorganic and polymeric substrates by the “grafting to” method. A brief overview of synthesis of polymer brushes by the method is first provided, with emphasis on chemical approaches to polymer attachment. The second part of the paper covers the synthesis of polymer layers via a recently developed macromolecular anchoring layer approach. Several examples of application of the grafting technique are presented for generation of hydrophobic, hydrophilic, gradient, and switchable surfaces.

     

Conductivity,thermal and morphology studies of PEO based salted polymer electrolytes

Polymer electrolyte has been prepared via solution-casting technique. The polymer electrolytes are formed from polyethylene oxide (PEO) and lithium hexafluorate is used as the doping salt. The conductivity increases from 10⁻⁹ to 10⁻⁴ S cm⁻¹ upon the addition of various concentrations of salt. The results reveal that the conductivity increases with increasing temperature when the salt concentration increases up to 20 wt% The conductivity for 20 wt% of salt remains similar to the conductivity for 15 wt% of salt at 318 K. Differential scanning calorimetry studies show that the melting transition temperature and crystallinity decreases upon the addition of various concentrations of salt. Thermogravimetric analysis (TGA) results indicate that a significant effect on the thermal stability of polyethylene–lithium salt composites. SEM images reveal that the morphology of polymer electrolyte's surface changes when various concentrations of salt are added into the polymer system.     

Direct synthesis of nitriles from aldehydes using tetrabutylammonium tribromide in aqueous ammonia

Abstract  

A convenient method for direct conversion of aldehydes into nitriles has been developed by using tetrabutylammonium tribromide in aqueous ammonia.     

Determination of micromolar concentrations of strong acids in chloroform by protonation of tetraphenylporphyrin

Abstract  

The protonation of tetraphenylporphyrin followed by spectrophotometric detection of the resulting dihydrogen tetraphenylporphyrin dication has been evaluated as a means to determine micromolar concentrations of strong acids in chloroform. The equilibrium constants for the process are large (>10¹⁰ for benzenesulfonic and methanesulfonic acids), but not large enough to ensure stoichiometric conversion to the dication unless only order of magnitude precision is required. The incorporation of a correction term in the stoichiometric approximation, based on a dilution of the analytical sample, yields an acceptable result for these two acids.