活性炭复合滤嘴吸附性能的热脱附研究

采用热脱附与气相色谱-质谱联用技术对活性炭滤嘴中活性炭和乙酸纤维脱附的组分进行了定性分析,并用峰面积归一化法测定了所含挥发性成分的质量分数,活性炭脱附组分共鉴定出芳香族化合物、醛酮类、烟碱、酸类、酯类等62种挥发性化合物.结果表明方法具有较好的重现性;为评价活性炭滤嘴的吸附性能提供了一种参考方法.     

Effect of cellulose nanofiber dimensions on sheet forming through filtration

Four different cellulose nanofibers samples were prepared from northern bleached softwood kraft fibers. Fiber diameter distributions were measured from SEM images. Fiber aspect ratios ranging from 84 to 146 were estimated from fiber suspension sedimentation measurements. Three samples had heterogeneous distributions of fiber diameters, while one sample was more homogeneous. Sheet forming experiments using filters with pores ranging from 150 to 5 μm showed that the samples with a heterogeneous distribution of fiber dimensions could be easily formed into sheets at 0.2% initial solids concentration with all filter openings. On the other hand, sheets could only be formed from the homogenous sample by using 0.5% or more initial solids content and a lower applied vacuum and smaller filter openings. The forming data and estimated aspect ratios show reasonable agreement with the predictions of the crowding number and percolation theories for the connectivity and rigidity thresholds for fiber suspensions.     

Self‐Healable Electrically Conducting Wires for Wearable Microelectronics

Electrically conducting wires play a critical role in the advancement of modern electronics and in particular are an important key to the development of next‐generation wearable microelectronics. However, the thin conducting wires can easily break during use, and the whole device fails to function as a result. Herein, a new family of high‐performance conducting wires that can self‐heal after breaking has been developed by wrapping sheets of aligned carbon nanotubes around polymer fibers. The aligned carbon nanotubes offer an effective strategy for the self‐healing of the electric conductivity, whereas the polymer fiber recovers its mechanical strength. A self‐healable wire‐shaped supercapacitor fabricated from a wire electrode of this type maintained a high capacitance after breaking and self‐healing.     

The use of charcoal from agriculture waste in the speciation of iodine from well and river waters

The concentrations of iodine in fresh waters are known to be within the range of 0.5 to 35 ng·ml⁻¹, much lower than in oceanic waters. The iodine concentrations, particularly that of¹²⁹I which is significant from the radiation safety aspect, in public drinking waters have to be specified in order to verify the required level before distribution for domestic use. A modified version of an established method was used in the adsorption of iodine, iodate, total inorganic iodine and charcoal-adsorbable iodine using activated carbon prepared from oil palm kernel wastes. A thorough investigation of the physical properties of the activated carbon was carried out to determine its viability as an adsorbent for volatile species such as iodine. The iodine species were preconcentrated from water samples collected from wells in villages and from water intake points along rivers. The quantitative analysis of the species adsorbed was done by irradiating the activated charcoal loaded with the respective species in a neutron flux of 5.1·10¹² n·cm⁻²·s⁻¹ from a TRIGA MkII, nuclear reactor. Recovery experiments using spiked samples was done to provide quality assurance controls.     

Application of mesoporous carbon as a solid‐phase microextraction fiber coating for the extraction of volatile aromatic compounds

A mesoporous carbon was fabricated using MCM‐41 as a template and sucrose as a carbon source. The carbon material was coated on stainless‐steel wires by using the sol–gel technique. The prepared solid‐phase microextraction fiber was used for the extraction of five volatile aromatic compounds (chlorobenzene, ethylbenzene, o‐xylene, bromobenzene, and 4‐chlorotoluene) from tea beverage samples (red tea and green tea) prior to gas chromatography with mass spectrometric detection. The main experimental parameters affecting the extraction of the volatile aromatic compounds by the fiber, including the extraction time, sample volume, extraction temperature, salt addition, and desorption conditions, were investigated. The linearity was observed in the range from 0.1 to 10.0 μg/L with the correlation coefficients (r) ranging from 0.9923 to 0.9982 and the limits of detection were less than 10.0 ng/L. The recoveries of the volatile aromatic compounds by the method from tea beverage samples at spiking levels of 1.0 and 10.0 μg/L ranged from 73.1 to 99.1%.     

New rapid methods of labelling by radioiodine

New methods for labelling of organic molecules by iodine radionuclides have been developed on the basis of a detailed study of processes occurring during radioiodination. Kits were preparations of iodinated radiophyarmaceuticals (e. g. hippurate, Bengal Rose, sulfobromophythalein). Further iodogene-impregnated filters were developed for labelling of non-iodinated compounds, especially proteins. Their use and preparation is quite simple and easy.     

Fabrication of novel nanoporous array anodic alumina solid-phase microextraction fiber coating and its potential application for headspace sampling of biological volatile organic compounds

In the study, nanoporous array anodic alumina (NAAA) prepared by a simple, rapid and stable two-step anodic oxidization method was introduced as a novel solid-phase microextraction (SPME) fiber coating. The regular nanoporous array structure and chemical composition of NAAA SPME fiber coating was characterized and validated by scanning electron microscopy and energy dispersive spectroscopy, respectively. Compared with the commercial polydimethylsiloxane (PDMS) SPME fiber coating, NAAA SPME fiber coating achieved the higher enrichment capability (1.7–4.7 folds) for the mixed standards of volatile organic compounds (VOCs). The selectivity for volatile alcohols by NAAA SPME fiber coating demonstrated an increasing trend with the increasing polarity of alcohols caused by the gradually shortening carbon chains from 1-undecanol to 1-heptanol or the isomerization of carbon chains of some typical volatile alcohols including 2-ethyl hexanol, 1-octanol, 2-phenylethanol, 1-phenylethanol, 5-undecanol, 2-undecanol and 1-undecanol. Finally, NAAA SPME fiber coating was originally applied for the analysis of biological VOCs of Bailan flower, stinkbug and orange peel samples coupled with gas chromatography–mass spectrometry (GC–MS) detection. Thirty, twenty-seven and forty-four VOCs of Bailan flower, stinkbug and orange peel samples were sampled and identified, respectively. Moreover, the contents of trace 1-octanol and nonanal of real orange peel samples were quantified for the further method validation with satisfactory recoveries of 106.5 and 120.5%, respectively. This work proposed a sensitive, rapid, reliable and convenient analytical method for the potential study of trace and small molecular biological VOCs by the novel NAAA SPME fiber coating.     

Concentration of iodine traces in solution by filtering through activated carbon

The retention of iodine traces (ppb) was investigated in small activated carbon filters (50 mg) from solution at a yielding rate exclusively determined by pH. Retention is approximately 100% at pH values of 4–6, while no retention of iodine traces occurs after filtering them through an activated carbon filter from very acidic and basic solutions (pH values of 1 and 11, respectively) with 0% yielding rate. Since activated carbon is a very pure material, this procedure may be an alternative method of the activation analysis of iodine traces in foodstuffs, because the half-life of ¹²⁸I, formed by (n,g) reaction, is only 25 minutes. It does not allow either the sample to be placed readily in solution or the radioisotope to be separated after irradiation with the purpose of attaining maximal accuracy and sensitivity in this type of analysis.     

Sampling volatile organic compounds using a modified solid phase microextraction device

Headspace solid phase microextraction (headspace SPME) has been demonstrated to be an excellent solvent-free sampling method. One of the major factors contributing to the success of headspace SPME is the concentrating effect of the fiber coating toward organic compounds. The affinity of the fiber coating toward very volatile analytes, such as chloromethane, may, however, not be large enough for detection at the parts per trillion concentration level. Static headspace analysis, on the other hand, is very effective for these very volatile compounds. As analyte volatility decreases, the sensitivity of static headspace analysis drops. The complementary nature of these two sampling methods can be exploited by combining the SPME device with a gastight syringe. The sensitivity of the new sampling device is better than that of SPME for very volatile compounds or that of static headspace analysis for less volatile compounds. This new method can sample a wide range of compounds from chloromethane (b.p. −24°C) to bromoform (b.p. 149°C) with estimated limits of detection at the low parts per trillion level.     

Development of solid-phase microextraction followed by gas chromatography-mass spectrometry for rapid analysis of volatile organic chemicals in mainstream cigarette smoke

In this work, a novel, simple and efficient method based on solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS) was developed to the analysis of volatile organic chemicals (VOCs) in mainstream cigarette smoke (MCS). Using a simple home-made smoking machine device, extraction and concentration of VOCs in MCS were performed by SPME fiber, and the VOCs adsorbed on fiber were desorbed, and analyzed by GC-MS. The extraction fiber types and the desorption conditions were studied, and the method precision was also investigated. After the investigation, the optimal fiber was divinylbenzene/carboxen/polydemethylsiloxane (DVB/CAR/PDMS), and the optimal desorption condition was 250 degrees C for 3 min. The method precision was from 2% to 11%. Finally, the proposed method was tested by its application of the analysis of VOCs in MCS from 10 brands of cigarettes and one reference cigarette. A total of 70 volatile compounds were identified by the proposed method. The experimental results showed that the proposed method was a simple, rapid, reliable, and solvent-free technique for the determination of VOCs in MCS.     

Determination of cobalt,selenium and iodine by NAA in foodstuff by preconcentration of traces

Neutron activation analysis of cobalt, selenium and iodine requires pre-concentration of traces when the best possible conditions of sensitivity and accuracy are required at short irradiation times. The reason is ^60mCo, ^77mSe and ¹²⁸I present half-lives of 10.5 m, 17.5 s and 25 m, respectively, which do not allow neither to dissolve the sample nor to perform any radiochemical separation after irradiation. On the other hand, their emissions are located in the beginning of the spectrum (59, 161 and 441 keV, respectively) where the Compton continuum makes difficult the identification and measurement of the peaks. This paper describes how foodstuff samples are dissolved in pure HNO₃ by using conventional pressure pumps at 120–140 °C during 3–4 hours. Once cooled down the acid solution, distilled water is added and pH fixed at 1–1.5 with ammonia. 20 mg of APDC are added while stirring during 2 minutes and the solution is passed through 50 mg of activated carbon, where the Se traces are trapped. Then the filtered solution is adjusted to pH 4–6 with ammonia and passed through a fresh identical activated carbon filter where the iodine traces are caught. Finally, to the filtered solution is added 20 mg of cupferron at same pH, stirring for 2 minutes and passed through a third identical carbon filter, where the cobalt traces remain. In this way, we have the cobalt, selenium and iodine traces in three different, extremely pure carbon matrices, with a small, known mass of cobalt, selenium and iodine as background. Each filter is ready to be irradiated during a suitable time, to calculate separately at maximum sensitivity and accuracy the concentration of these three trace elements so important to human nutrition.     

固相微萃取-气相色谱/同位素质谱法测定水中挥发性有机物单体碳同位素

建立了采用75μm碳分子筛/聚二甲基硅氧烷(CAR-PDMS)纤维的固相微萃取-气相色谱/同位素质谱联用方法测定水中挥发性有机污染物碳同位素。使用浸入式固相微萃取和顶空固相微萃取方法进行实验确定在低浓度条件下最佳δ13C测试方法。通过使用顶空固相微萃取前处理技术进行单体同位素分析分析灵敏度更高,应用CSIA技术对1,2-二氯乙烯,三氯乙烯,四氯化碳进行单体同位素分析,方法的检出限为70μg/L,与样本的标准偏差小于0.3‰。该法适用于水体中微量挥发性有机污染物的同位素组成测定。     

Photocatalysis of TiO2 Sheets Prepared by Templating Filter Paper

Titanium dioxide sheet photocatalysts composed of interwoven microstrips were successfully synthesized using filter paper as templates. The synthesized samples were characterized by means of Fourier transform infrared spectroscopy, surface area analyzer, thermogravimetric analysis, powder X-ray diffraction, and scanning electron microscopy. The photocatalytic activities of the samples were evaluated by the degradation of methyl orange in an aqueous solution under UV-illumination. The results demonstrated that the paper-like TiO₂ sheets with the optimum proportion of anatase/rutile (10/1) had the highest photoactivity. And the presence of the filter paper fiber can improve the crystallinity, raise the anatase-rutile transformation temperature and contribute to the formation of being paper-like. A detailed formation mechanism for TiO₂ sheets is proposed.     

Microstructure and properties of polyacrylonitrile based carbon fibers

The microstructure of polyacrylonitrile (PAN)-based carbon fibers with different mechanical properties was investigated. It was found that the tensile strength of the PAN-based carbon fibers generally decrease with the increase in the modulus. The properties of PAN-based carbon fiber are mainly controlled by the microstructure and microvoids. The increase in size and orientation of graphite crystallites follows the decrease in interlayer space of graphite sheets, which accompanies the increase in modulus and decrease in tensile strength of the carbon fibers. Simultaneously, the increase in the modulus of the carbon fibers accompanies the merging of the elliptical microvoids along the fiber axis and the turbostratic graphite in the carbon fibers transforms into 3D ordered graphite lamellar structure. This work provides useful information on tailoring the mechanical properties of carbon fibers by adjusting the microstructure.     

活性碳纤维的结构修饰及其吸附氙性能的研究

活性炭纤维对氙的吸附容量与其孔结构密切相关，为了提高活性炭纤维对氙气的吸附容量，本文分别用亚甲基蓝、对硝基苯酚等有机物，或氯化钠、碘等无机化合物填充的方法修饰活性炭纤维的孔结构；以及利用高锰酸钾或硝酸等氧化处理修饰活性炭纤维的表面化学性质，同时，利用低温氮等温吸附表征了这些改性活性炭纤维的孔结构，以及通过光电子能谱表征了改性活性炭纤维的表面化学结构，上述化合物充填或氧化改性活性炭纤维对氙的吸附性能的研究结果表明，适量化合物填充，或合适浓度硝酸对活性炭纤维的表面处理，可以有效地修饰活性炭纤维的孔结构或改变活性炭纤维表面对氙的亲和力。因而可有效地提高改性活性炭纤维对氙的吸附容量。     

Preparation and application of a coated‐fiber needle extraction device

In this study, a needle‐trap device with fibers coated with a molecularly imprinted polymer was developed for separation. A number of heat‐resistant Zylon filaments were longitudinally packed into a glass capillary, followed by coating with a molecularly imprinted polymer. Then, the molecularly imprinted polymer coating was copolymerized and anchored onto the surface of the fibers. The bundle of synthetic fibers coated with the molecularly imprinted polymer was packed into a 21G stainless‐steel needle and served as an extraction medium. The coated‐fiber needle extraction device was used to extract volatile organic compounds from paints and gasoline effectively. Subsequently, the extracted volatile organic compounds were analyzed by gas chromatography. Calibration curves of gaseous benzene, toluene, ethylbenzene, and o‐xylene in the concentration range of 1–250 μg/L were obtained to evaluate the method, acceptable linearity was attended with correlation coefficients above 0.998. The limit of detection of benzene, toluene, ethylbenzene, and o‐xylene was 11–20 ng/L using the coated‐fiber needle‐trap device. The relative standard deviation of needle‐to‐needle repeatability was less than 8% with an extraction time of 20 min. The loss rates after storage for 3 and 7 days at room temperature were less than 30%.     

Flexible,Stretchable, and Rechargeable Fiber‐Shaped Zinc–Air Battery Based on Cross‐Stacked Carbon Nanotube Sheets

The fabrication of flexible, stretchable and rechargeable devices with a high energy density is critical for next‐generation electronics. Herein, fiber‐shaped Zn–air batteries, are realized for the first time by designing aligned, cross‐stacked and porous carbon nanotube sheets simultaneously that behave as a gas diffusion layer, a catalyst layer, and a current collector. The combined remarkable electronic and mechanical properties of the aligned carbon nanotube sheets endow good electrochemical properties. They display excellent discharge and charge performances at a high current density of 2 A g⁻¹. They are also flexible and stretchable, which is particularly promising to power portable and wearable electronic devices.     

Flexible,Stretchable, and Rechargeable Fiber‐Shaped Zinc–Air Battery Based on Cross‐Stacked Carbon Nanotube Sheets

The fabrication of flexible, stretchable and rechargeable devices with a high energy density is critical for next‐generation electronics. Herein, fiber‐shaped Zn–air batteries, are realized for the first time by designing aligned, cross‐stacked and porous carbon nanotube sheets simultaneously that behave as a gas diffusion layer, a catalyst layer, and a current collector. The combined remarkable electronic and mechanical properties of the aligned carbon nanotube sheets endow good electrochemical properties. They display excellent discharge and charge performances at a high current density of 2 A g^?1. They are also flexible and stretchable, which is particularly promising to power portable and wearable electronic devices.     

Radioanalytical Determination of Biogenic Volatile Iodine Emitted from Aqueous Environmental Samples

A reliable method using ¹²⁵I tracer for direct determination of volatile iodine formed in aqueous environmental samples was established. Soil solution, seawater and bacterial cell suspension were selected as model samples, and incubated with ¹²⁵I^–. Volatile inorganic and organic iodine species produced during incubation were collected in silver wool and activated charcoal traps, separately the efficiency of the traps, the storage conditions of ¹²⁵I^– stock solution and the procedures to expel the dissolved volatile iodine from the sample solutions were examined. Formation of biological volatile iodine was observed in all samples, and the dominant iodine species was found to be organic iodine. The advantages of this method are its simplicity, low cost and low detection limit.     

Assembly of well-aligned multiwalled carbon nanotubes in confined polyacrylonitrile environments: electrospun composite nanofiber sheets

Highly oriented, large area continuous composite nanofiber sheets made from surface-oxidized multiwalled carbon nanotubes (MWNTs) and polyacrylonitrile (PAN) were successfully developed using electrospinning. The preferred orientation of surface-oxidized MWNTs along the fiber axis was determined with transmission electron microscopy and electron diffraction. The surface morphology and height profile of the composite nanofibers were also investigated using an atomic force microscope in tapping mode. For the first time, it was observed that the orientation of the carbon nanotubes within the nanofibers was much higher than that of the PAN polymer crystal matrix as detected by two-dimensional wide-angle X-ray diffraction experiments. This suggests that not only surface tension and jet elongation but also the slow relaxation of the carbon nanotubes in the nanofibers are determining factors in the orientation of carbon nanotubes. The extensive fine absorption structure detected via UV/vis spectroscopy indicated that charge-transfer complexes formed between the surface-oxidized nanotubes and negatively charged (-CN[triple bond]N:) functional groups in PAN during electrospinning, leading to a strong interfacial bonding between the nanotubes and surrounding polymer chains. As a result of the highly anisotropic orientation and the formation of complexes, the composite nanofiber sheets possessed enhanced electrical conductivity, mechanical properties, thermal deformation temperature, thermal stability, and dimensional stability. The electrical conductivity of the PAN/MWNT composite nanofibers containing 20 wt % nanotubes was enhanced to approximately 1 S/cm. The tensile modulus values of the compressed composite nanofiber sheets were improved significantly to 10.9 and 14.5 GPa along the fiber winding direction at the MWNT loading of 10 and 20 wt %, respectively. The thermal deformation temperature increased with increased MWNT loading. The thermal expansion coefficient of the composite nanofiber sheets was also reduced by more than an order of magnitude to 13 x 10(-6)/ degrees C along the axis of aligned nanofibers containing 20 wt % MWNTs.