Fe_3O_4/Au磁性复合材料的制备及表征

本文首先通过多醇法制备粒径可控的四氧化三铁纳米粒子,通过硅烷偶联剂对四氧化三铁纳米粒子进行胺基化修饰,胺基化修饰四氧化三铁纳米粒子与羧基表面的Au纳米粒子通过静电相互作用制备得到Fe_3O_4/Au复合纳米材料。透射电子显微镜、红外光谱仪、能谱仪等表征揭示成功制备具有core-/Satelite结构Fe_3O_4/Au复合纳米材料。     

静电纺丝法制备PEO/Fe_3O_4磁性纳米纤维

以聚氧化乙烯(PEO)为聚合物纺丝原料、卵蛋白粉(LDB)为分散剂,通过静电纺丝技术制备一系列不同四氧化三铁(Fe_3O_4)含量的Fe_3O_4/PEO复合纳米材料。经傅里叶红外光谱仪测试,显示纳米复合材料中存在Fe_3O_4。采用数显黏度计、导电率仪和扫描电子显微镜对制备的复合纳米材料的形态及物相组成进行表征,并分析了Fe_3O_4的加入对复合纳米材料可纺性的影响。结果表明,PEO与Fe_3O_4比例为10∶3时,复合纳米材料的可纺性最好,纤维平均直径达110 nm。     

基于阳离子改性的四氧化三铁的结构与性能优化

为提高空气气氛下阳离子改性的四氧化三铁(Fe_3O_4)的结构与性能,进一步优化了聚二烯丙基二甲基氯化铵(PDDA)改性的Fe_3O_4的制备工艺。利用X射线衍射仪、粒度分析仪、透射电子显微镜、振动样品磁强计等进行表征与测试,研究了利用化学共沉淀法制备Fe_3O_4纳米粒子的过程中,PDDA在Fe_3O_4晶粒成型的不同阶段进行改性对最终产品质量的影响。结果表明:当PDDA在Fe_3O_4晶粒成型后直接进行改性,其包覆厚度适宜,包覆率约为2.01%;包覆外观均匀,表现为Fe_3O_4纳米粒子均匀分散于PDDA中;得到的磁性复合纳米粒子磁性最强,可高达3.47×10~5A/m。     

KGM/纳米ZnO复合膜透湿性工艺优化

以魔芋葡甘露聚糖(KGM)为基料,利用纳米ZnO对其进行共混改性,制备KGM/纳米ZnO复合膜,在单因素试验基础上,以纳米ZnO浓度、甘油浓度、反应时间为主要影响因素,以水蒸气透过系数(WVP)为响应值,采用Box-Behnken响应面法对KGM/纳米ZnO复合膜的制备工艺进行优化。结果表明,纳米ZnO浓度对复合膜WVP的影响不显著,甘油浓度和反应时间对复合膜WVP的影响显著, KGM/纳米ZnO复合膜的最佳工艺条件为:纳米ZnO浓度0.60%、甘油浓度0.68%、反应时间61 min。在此条件下制得的复合膜的水蒸气透过系数为0.082 2 g·mm/(m~2·h·k Pa)。     

Fe_3O_4@SiO_2磁性纳米材料的制备及结构调控

本文首先通过改进的多醇法制备粒径可控的四氧化三铁纳米材料,进一步通过St?ber法制备Fe_3O_4/Si O_2复合纳米材料。采用透射电镜表征纳米材料的尺寸、结构及形貌。在制备的过程中引入柠檬酸钠获得亲水四氧化三铁,改变柠檬酸钠的量调控四氧化三铁纳米材料的粒径,包覆二氧化硅后得到一系列粒径可控的Fe_3O_4/Si O_2复合纳米材料。     

Fe_3O_4纳米粒子的制备方法及其最新应用进展

综述了近年来四氧化三铁(Fe_3O_4)纳米粒子常用的制备方法及其应用的最新进展。主要包括Fe_3O_4纳米粒子及其复合材料在废水处理、化学催化、能源储备和生物医学等领域的研究现状。同时探讨了Fe_3O_4纳米粒子在现有应用过程中存在的挑战和未来可能的发展趋势。     

还原氧化石墨烯/四氧化三铁纳米复合物的应用研究进展

还原氧化石墨烯/四氧化三铁(RGO/Fe_3O_4)纳米复合物是一种新型的磁性纳米材料,集Fe_3O_4和RGO的优点于一体,具备高比表面积、高稳定性、超顺磁性等优越的机械、电、热、光学特性,充分展现其在理论研究以及实际应用方面的价值和潜力。本文对近几年RGO/Fe_3O_4磁性纳米复合物材料在磁性固相萃取、锂电子电池、传感器材料、电磁波吸收、催化剂、酶的固定化、药物传输以及磁控开关方面的应用研究进展进行了综述,重点综述了RGO/Fe_3O_4磁性纳米复合材料在磁性固相萃取方面的应用研究,分析对象包括染料、金属离子、农兽药、增塑剂、抗生素以及生物大分子,展现出其在分离富集领域的巨大应用潜力。最后,提出RGO/Fe_3O_4纳米复合材料在研究中存在的问题,并对该材料的研究发展方向进行了展望。     

PLA/TiO_2纳米复合膜对香菇保鲜效果的研究

为研究纳米复合材料对采后香菇的保鲜效果,以未包装的香菇为对照,探讨了添加不同质量分数0%、1%、2%、3%纳米Ti O_2的PLA/Ti O_2纳米复合膜对香菇保鲜效果的影响。在(4±1)℃条件下,每4 d测定香菇贮藏期间理化指标及微生物指标。结果表明,PLA/Ti O_2纳米复合膜能更好地维持香菇贮藏期间的感官品质,抑制呼吸强度,减缓水分流失,维持较高VC及还原糖含量。纳米Ti O_2添加量与香菇的保鲜效果成正比,其中3%PLA/Ti O_2纳米复合膜对香菇的保鲜效果最佳。     

金磁纳米颗粒的制备及其在表面增强拉曼光谱快速检测黄曲霉毒素B1中的应用

本文采用纳米Fe_3O_4颗粒作为磁性核心,先用四乙氧基硅烷、再用3-巯丙基三乙氧基硅烷和3-氨丙基三乙氧基硅烷修饰Fe_3O_4颗粒,形成表面带-NH_2和-SH的Fe_3O_4/SiO_2纳米颗粒,进一步通过-NH_2的静电吸附和Au-S键的作用将金纳米颗粒组装在Fe_3O_4/SiO_2表面,形成具有核壳结构的Fe_3O_4/SiO_2/Au金磁纳米颗粒,并用透射电子显微镜镜(TEM)、能量色散X射线光谱仪(EDX)、紫外可见分光光度计(UV-vis)等技术对金磁纳米颗粒进行了形貌观测及性质表征。利用Fe_3O_4/SiO_2/Au金磁纳米颗粒作为拉曼活性基底,用表面增强拉曼光谱仪对黄曲霉毒素B1(AFB1)进行直接快速检测,发现无外磁体浓缩的情况下AFB1的检测限大于10.0μg/m L,在外磁体浓缩金磁纳米颗粒的情况下检测限降低100倍(≤0.1μg/m L),检测线性范围0.1μg/m L~10.0μg/m L,检测的样品回收率为84.35%~91.98%,相对标准偏差在4.88%~9.90%之间。     

纳米纤维锂电池负极材料的制备及性能分析

探讨一种用于高性能锂离子电池负极材料的制备及性能。通过配制乙酰丙酮铁的聚丙烯腈/聚甲基丙烯酸甲酯(PAN/PMMA)混合溶液用作前驱液,利用静电纺丝技术制备多孔碳/四氧化三铁纳米纤维。结果表明:多孔碳/四氧化三铁纳米纤维呈现多孔的结构和凹凸不平的形貌,Fe_3O_4纳米粒子均匀地镶嵌在碳基质中;在电流密度为100 mA/g时,多孔碳/四氧化三铁材料电极首次放电比容量高达1 380 mAh/g,经过100次循环后,稳定比容量为641 mAh/g;这种电极材料表现出优良的倍率性能,在电流密度为5 000 mA/g时,其可逆比容量仍维持在330 mAh/g。认为:这种多孔碳/四氧化三铁复合物作为高性能锂电池负极材料具有广泛的应用前景。     

Comprehensive Evaluation and Prediction of the Effectiveness of H2O2-assisted Na2CO3 Pretreatment of Corn Stover Using Multivariate Analysis

In this study, multivariate analysis methods, including a principal component analysis (PCA) and partial least square (PLS) analysis, were applied to reveal the inner relationship of the key variables in the process of H₂O₂-assisted Na₂CO₃ (HSC) pretreatment of corn stover. A total of 120 pretreatment experiments were implemented at the lab scale under different conditions by varying the particle size of the corn stover and process variables. The results showed that the Na₂CO₃ dosage and pretreatment temperature had a strong influence on lignin removal, whereas pulp refining instrument (PFI) refining and Na₂CO₃ dosage played positive roles in the final total sugar yield. Furthermore, it was found that pretreatment conditions had a more significant impact on the amelioration of pretreatment effectiveness compared with the properties of raw corn stover. In addition, a prediction of the effectiveness of the corn stover HSC pretreatment based on a PLS analysis was conducted for the first time, and the test results of the predictability based on additional pretreatment experiments proved that the developed PLS model achieved a good predictive performance (particularly for the final total sugar yield), indicating that the developed PLS model can be used to predict the effectiveness of HSC pretreatment. Therefore, multivariate analysis can be potentially used to monitor and control the pretreatment process in future large-scale biorefinery applications.     

Preparation and Characterization of Co3O4/Graphene/Cellulose Nanofiber Composite Films

Nanocellulose has served as an eye-catching nanomaterial for constructing advanced functional devices with renewability, light weight, flexibility, and environmental friendliness. In this study, Co₃O₄/graphene/cellulose nanofiber (CNF) flexible composite films, in which the CNF acted as a spacer for the graphene, were prepared via a facile and scalable vacuum filtration method. The effects of the CNF on the microstructure, hydrophilicity, thermal stability, tensile strength, surface resistance, and electrochemical performance of the Co₃O₄/graphene/CNF composite films were systematically investigated. The results showed that the synergistic interaction of the CNF and graphene substantially improved the overall properties of the Co₃O₄/graphene/CNF composite films, particularly their hydrophilicity and tensile strength. Meanwhile, Co₃O₄/graphene/CNF composite films with a CNF content of 4% appeared to have the optimal electrochemical performance, with an area specific capacitance of 56 mF/cm² and prominent capacitance retention of 95.6% at a current density of 1 A/g after 1000 cycles. This work demonstrated that the prepared Co₃O₄/graphene/CNF flexible composite films have great application potential in the field of flexible energy storage devices.     

Dependence of sheet resistance of nickel-plated PANi/PTT composite fabric on electroless plating conditions

Flexible and stretchable conductive composite fabrics have wide applications, including wearable sensors, antenna, electrodes, solar batteries, signal, or power transmission. For most of applications, the electrical conductive fabrics need a low sheet resistance and antioxidation. To improve the stability and the electrical conductivity of PANi/PTT composite conductive fabric, some conductive composite fabrics were prepared by electroless nickel plating on PANi/PTT composite fabrics in the aqueous nickel sulfate solutions. The sheet electrical properties of the composite fabric were evaluated by the van der Pauw method, and the effect of the chemical plating conditions such as reducing agent, complexing agent, and buffer agent concentrations were investigated on the sheet resistance as well as the mechanical properties of fabric substance. The results show that the lower sheet resistance of composite fabrics was observed at the concentrations of NiSO₄, 25 g/L, NaH₂PO_2, 20 g/L, Na₃C₆H₅O₇, 15 g/L, CH₃COONa, 20 g/L, respectively. Additionally, the mechanical properties of the Ni/PANi/PTT composite fabrics were improved in comparison with those of PANi/PTT composite fabrics.     

Effect of controlled atmosphere storage on aflatoxin production in high moisture peanuts (groundnuts)

Shelled peanuts (groundnuts) remoistened to 16.7% were stored for 4 weeks at about 27°C in air (0.03% CO₂, 21% O₂, 78% N₂) and in three modified atmospheres: (1) 13.6% CO₂, 0.3% CO, 0·6% O₂, 84.7% N₂; (2) 12.2% CO₂, 3.1% CO, 0.3% O₂, 83.5% N₂; and (3) 13.6% CO₂, 0.1% CO, 1.5% O₂, 83.9% N₂. Aflatoxins, per cent free fatty acids, and per cent kernel infection by the Aspergillus flavus group were determined weekly. Peanuts in air and in the atmosphere containing 1.5% O₂ accumulated high levels of aflatoxin in 1 and 2 weeks, respectively. In the other two controlled atmospheres aflatoxin B₁ did not exceed 21 μg/kg and the per cent of free fatty acids increased only slightly. None of the treatments eliminated infection by the A. flavus group. After 4 weeks peanuts in all treatments had visible fungal growth on surfaces.     

Na+ Binding as Measured by 23Na Nuclear Magnetic Resonance Spectroscopy Influences the Perception of Saltiness in Gum Solutions

Binding of Na⁺ in aqueous gum systems as determined by ²³Na nuclear magnetic resonance (NMR) spectroscopy and its relations to perceived saltiness were examined. Two levels of NaCl (0.1% and 0.2%) were added to two concentrations (0.1% and 0.3%) of two ionic (xanthan and kappa carrageenan) and two non-ionic (locust bean and guar) gum solutions. Saltiness perception was affected by the ionic properties of the gums. NMR transverse relaxation rates (R₂, see^?l) indicated Na⁺ was less mobile in ionic than nonionic systems. Ionic gums correspondingly suppressed saltiness perception- compared to nonionic gums. As Na⁺ increased in both ionic and nonionic systems, R₂ values converged and perceived saltiness equalized. Food components that bind Na⁺ may suppress saltiness perception, which may be important in low-sodium foods.     

The effect of selected phosphate emulsifying salts on viscoelastic properties of processed cheese

The aim of this study was to investigate the effect of selected phosphate emulsifying salts (Na₃PO₄, Na₂HPO₄, Na₄P₂O₇, Na₂H₂P₂O₇, Na₅P₃O₁₀, sodium polyphosphate) and their selected mixtures (sodium polyphosphate + Na₂HPO₄; sodium polyphosphate + Na₄P₂O₇) on the viscoelastic properties of model processed cheese (dry matter - 40 g/100 g; fat in dry matter - 50 g/100 g). Viscoelastic properties of model samples stored at 6 ± 2 °C were investigated by dynamic oscillation rheometry (plate-plate geometry; frequency range 0.1-50.0 Hz; temperature 20 °C). Processed cheese manufactured with different phosphates showed various pH values and different viscoelastic properties. The firmness of samples increased due to use of particular types of tested phosphates. Their influence on cheese firmness increased in the following order: orthophosphate < polyphosphate < diphosphate < triphosphate. The increasing content of polyphosphate (up to 50%) in the binary mixture of polyphosphate and orthophosphate or polyphosphate and diphosphate caused the increase of firmness of model samples. The content of polyphosphates above 50% in the binary mixture led to decrease of firmness of model processed cheese.     

Effects of high O2 levels on post-harvest quality and shelf life of table grapes during long-term storage

Freshly harvested Kyoho table grapes (Vitis vinifera × V. labrusca) were stored in controlled atmospheric chambers, either in air, 80% O₂, or 40% O₂ + 30% CO_2, for up to 60 days at 0 °C in 95% relative humidity followed by 5 days in air at 20 °C. Physical and chemical properties were recorded initially and at 15-day intervals during storage. Storage in 80% O₂ or 40% O₂ + 30% CO₂ improved berry hardness, springiness, chewiness, flavors and membrane integrity over control stored in air. In addition, these high O₂ storage conditions significantly reduced fruit decay, berry drop, rachis browning and weight loss, delayed the decrease of soluble solids, titratable acidity and ascorbic acid of table grapes, compared with storage in air. Treatment in 80% O₂ resulted in a significantly firmer berry, better texture, berry adherence strength, and sensory scores than those treated with 40% O₂ + 30% CO₂, but did not significantly affect cohesiveness, springiness, aroma and membrane integrity. Data obtained in this study suggest that high oxygen treatment improve the quality of table grapes and extend its shelf life.     

Fe3O4/木质素基纳米碳纤维复合材料的制备及其微波吸收性能探究

本研究以蔗渣乙酸木质素为原料制备了木质素基实心和中空纳米碳纤维(CNFs和HCNFs),然后采用溶剂热法,将经浓硝酸表面氧化处理后的碳纤维和乙酰丙酮铁共混反应合成了Fe_3O_4/实心和中空纳米碳纤维复合材料(Fe_3O_4/CNFs和Fe_3O_4/HCNFs)。通过傅里叶变换红外光谱仪和拉曼光谱仪分析了碳纤维在浓硝酸氧化处理前后的结构变化,通过扫描电子显微镜能谱仪、X射线衍射仪、比表面积孔径分析仪、振动样品磁强计和矢量网络仪分析并对比了Fe_3O_4/CNFs和Fe_3O_4/HCNFs的形貌结构、磁性能和微波吸收性能。结果表明,Fe_3O_4/CNFs和Fe_3O_4/HCNFs的饱和磁化强度分别为12. 7emu/g和16. 5 emu/g,均表现出了典型的超顺磁性。相较于Fe_3O_4/CNFs,Fe_3O_4/HCNFs在厚度仅为1. 5mm下其最小反射损耗达-11. 8 dB,另外随着吸波体厚度在1. 0～2. 5 mm范围变化,小于-10 dB的吸收频带范围为5. 28～14. 75 GHz,表现出了更优异的微波吸收性能。     

Reduction of trimethylamine oxide byShewanellaspp. under modified atmospheresin vitro

Two strains ofShewanellaspp. were isolated from cod fillets packed in modified atmosphere (60% CO₂, 30% O₂, 10% N₂). One of the strains was identified asShewanella putrefaciens. The other strain could not be fully identified but was determined as aShewanellaspp. different fromS. putrefaciens. The effect of modified atmosphere (CO₂, O₂) on the growth of the two strains and on the reduction of TMAO to TMA was studied using solid medium from fish extract packed under variable mixtures of CO₂, O₂and N₂. All the samples were incubated at 7°C for 7 days. TheShewanella-like strain was shown to be a stronger TMAO reducer and was more resistant to CO₂thanS. putrefaciens per se. Modified atmosphere packaging of marine fish can inhibit the growth and TMAO-reducing activity ofS. putrefacienswhen 50% of CO₂together with 10% of O₂are introduced into the packaging atmosphere. The growth and TMAO-reducing activity of theShewanella-like strain can be inhibited when higher proportions of CO₂together with as high as possible proportions of O₂are introduced into the packaging atmosphere. It is suggested that a combination of 60–70% CO₂and 30–40% O₂is introduced into the packaging atmosphere in order to prevent TMA production byShewanellaspp.     

Changes in enzyme activities in abscission zone and berry drop of ‘Kyoho’ grapes under high O2 or CO2 atmospheric storage

To investigate the effects of high atmospheric O₂ on berry drop in ‘Kyoho’ grapes (Vitis vinifera X V. labrusca), changes in fruit detachment force (FDF), berry abscission and enzyme activities in the abscission zone (AZ) were examined during 60 days of storage in air (control), 40% O₂+30% CO₂ or 80% O₂ at 0 °C and 95% relative humidity. There was a high negative correlation between FDF and berry drop. Cellulase activity increased over time and correlated strongly with berry abscission. Polygalacturonase (PG) activity increased markedly for the first 30 days and then decreased slightly. Pectinesterase (PE) maintained a basal level of activity at low temperatures. Cellulase, PG and PE activities were the lowest in fruits in 80% O₂, followed by 40% O₂+30% CO₂ and air storage. Peroxidase (POD) activity dropped firstly and subsequently rose sharply, which promoted by 80% O₂ and inhibited by 40% O₂+30% CO₂ compared with control. High O₂ suppressed the activities of cellulase, PG and PE, maintained higher FDF, and reduced berry abscission during storage.