纳米纤维素/MXene柔性电子器件的制备及应用研究进展

纳米纤维素/MXene复合材料兼顾MXene优异的导电性能、丰富的表面官能团和超高比表面积,以及纳米纤维素基材料优良的力学性能和机械稳定性,成为应用于柔性传感、电磁屏蔽、能源储存等领域的热门材料。本文对纳米纤维素/MXene复合材料的制备方法进行论述,重点阐述其作为柔性电子器件在压力传感器、电磁屏蔽材料、超级电容器中的性能及最新研究进展,归纳总结纳米纤维素/MXene复合材料所面临的挑战,并对其未来发展趋势进行展望。     

中空磁性Fe3O4纳米球/MXene复合棉织物的制备及其电磁屏蔽性能

为优化导电织物对电磁波的阻抗匹配性，减少电磁波的二次污染，在棉织物中引入磁损耗材料中空Fe₃O₄纳米球，并通过层层组装的方法将其与过渡金属碳化物/氮化物(MXene)结合制备中空磁性Fe₃O₄纳米球/MXene复合棉织物，探究中空磁性Fe₃O₄纳米球对复合棉织物电磁屏蔽性能的影响规律和作用机制。借助超景深显微镜、扫描电子显微镜和矢量网络分析仪对中空磁性Fe₃O₄纳米球/MXene复合棉织物的形貌结构和电磁屏蔽性能进行表征与分析。结果表明：通过水热合成制备的Fe₃O₄具有中空球状形貌和尖晶石晶体结构，颗粒尺寸较为均匀，为(271.9±4.6) nm;随着Fe₃O₄/MXene负载循环次数的增加，复合棉织物的方阻逐渐减小，最低为(10.5±1.7)Ω/,并展现出较好的透气性；复合棉织物的电磁屏蔽性能也逐渐增强，最高电磁屏蔽效能可达...     

二维碳化物在柔性电磁吸波领域的研究进展

针对传统电磁屏蔽材料因反射电磁波导致二次污染,现有吸波材料厚重、易腐蚀、柔韧性差、吸波频带窄等问题,归纳总结了新型二维过渡金属碳/氮化合物(MXene)及其柔性复合材料在吸波领域的应用研究。分析了MXene所具有的本征缺陷、官能团、高导电率、大的比表面积对吸波性能的影响,提炼出MXene及其柔性复合材料的吸波机制。指出MXene及其柔性复合材料可以通过改变化合物结构和形态结构、层层自组装、复合改性等方法,制备以吸收电磁波为主的电磁屏蔽材料,为新一代轻质超薄、柔性宽频、吸收型电磁屏蔽材料的发展及其在便携可穿戴电子设备上的应用提供了研究方向。     

纳米纤维素/二维材料纳米复合材料在水处理领域的应用进展

近年来,纳米纤维素在水处理领域受到广泛关注。纳米纤维素的羟基对带有离子结构的污染物表现出一定的吸引力,通过表面改性还可进一步提高其捕获能力。将纳米纤维素和石墨烯等二维材料复合能够制备高性能纳米复合材料,提高材料对污染物的选择性。本文介绍了纳米纤维素和常见的几种二维材料,综述了纳米纤维素/二维材料复合材料在水处理领域的应用,包括过滤、吸附、光催化降解3种处理方法,并对不同二维材料与纳米纤维素复合后在水处理领域应用中的差异进行了比较。     

二维过渡金属碳/氮化合物复合纤维在智能可穿戴领域的应用进展

针对传统纤维难以满足当前智能可穿戴设备需求,现有复合纤维大都不能兼具导电性能好、力学性能优、储能特性强等问题,归纳总结了一种新型二维过渡金属碳/氮化合物(MXene)复合纤维在智能可穿戴领域中的研究进展。首先从纤维制备角度介绍了MXene复合纤维的制备方法,包括涂覆法、双辊法、静电纺丝法和湿法纺丝法等,并分析了各种方法的优劣;然后对制备的MXene复合纤维在现阶段电磁屏蔽、超级电容器、柔性传感器等领域的应用进行系统介绍;最后对MXene复合纤维在智能可穿戴领域的未来发展进行展望,为新一代导电性高、力学性能优异、高能量储存复合纤维的研究提供新的思路。     

疏水型纳米纤维素/纳米ZnO复合材料的制备及性能表征

将纳米纤维素与纳米Zn O在一定条件下机械搅拌,制备了纳米纤维素/纳米Zn O复合溶胶。通过硬脂酸对其进行改性,并将所得的改性后的复合溶胶在130℃下鼓风干燥2h,即可得到疏水型纳米纤维素/纳米Zn O复合材料。采用场发射扫描电镜、傅里叶红外光谱和接触角分析仪对复合材料的表面形貌和疏水性进行了表征。结果表明,复合粒子经硬脂酸表面改性后引入了憎水基团甲基,形成微/纳米双重粗糙结构,使得复合材料具备一定的疏水性能。     

木质素/TiO2复合纳米颗粒合成及纳米纤维素基紫外屏蔽膜制备

本研究利用碱木质素作为生物模板诱导剂,通过水热法成功合成了一种具有良好紫外屏蔽性能的木质素/TiO_2复合纳米颗粒。结果表明,木质素/TiO_2复合纳米颗粒具有锐钛矿晶型、良好的纳米粒径和热稳定性。同时,证实了木质素的含氧官能团和TiO_2表面羟基发生类酯化反应,从而使木质素与TiO_2形成包覆嵌顿式结构的复合材料。在此基础上,研究了木质素/TiO_2复合纳米颗粒与纳米纤维素水凝胶制备薄膜材料的抗紫外性能。结果表明,添加质量分数10%的木质素/TiO_2复合纳米颗粒的纳米纤维素薄膜在全紫外线波段(200～400 nm)吸收了约90%的紫外线,表明木质素/TiO_2复合纳米颗粒具有良好的紫外屏蔽能力。     

不同维度纳米纤维素基复合材料的制备及其在储能器件中的应用

纳米纤维素是一种可持续的绿色纳米材料,独特的结构使其成为发展下一代高效、环保储能器件的新选择。采用原位聚合、共混、层层自组装等方法可将纳米纤维素与碳材料、导电高分子、无机纳米粒子、过渡金属氧化物等光电材料复合形成具有导电和储能效应的多功能纳米复合材料。本文对不同维度的纳米纤维素基复合材料的制备方法及其在储能器件中应用的最新研究进展进行了综述并介绍了纳米纤维素基复合材料在储能领域未来发展中亟待解决的问题和发展方向及重点。     

纤维素/磁性纳米复合纤维的制备方法

使用磁性纳米复合纤维制得的特种纸具有优良的性质和广阔的应用前景,受到越来越多的关注。将磁性纳米粒子与纤维素纤维复合制备磁性纳米复合纤维,采用造纸方法抄造磁性纸,赋予其磁响应、防伪、电磁波屏蔽等功能,可以开拓纤维素纤维应用新领域、增加纸张新品种。     

纤维素/MXene复合气凝胶的制备及其对亚甲基蓝的吸附机制

将新型二维纳米材料掺杂进凝胶三维结构框架材料得到复合凝胶，可以增强凝胶对亚甲基蓝染料(MB)吸附能力，对于研究去除印染废水具有重要意义。以微晶纤维素为凝胶框架材料，MXene(MX)为功能掺杂剂，通过冷冻干燥法制备纤维素/MXene复合气凝胶。利用扫描电子显微镜、傅里叶红外光谱、EDS元素分析等表征其微观形貌及化学结构，并探究对亚甲基蓝的吸附作用。结果表明：制备的MXene呈现二维层状结构，掺杂后复合气凝胶呈现三维多孔结构，且MXene的加入提高了复合气凝胶的孔隙率；复合气凝胶的吸附效果远远高于纯纤维素气凝胶，对亚甲基蓝的吸附率高达80%;当温度为20℃,染料溶液初始质量浓度为50 mg/L时，复合气凝胶质量为100 mg,吸附效果最佳，通过动力学模型拟合分析，复合气凝胶吸附亚甲基蓝染料主要吸附过程为化学吸附。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.