BaO∙4B2O3∙5H2O纳米材料的制备及其对聚丙烯阻燃性能的热分解动力学方法评价

Borate is considered one of the most important additives for improving the fire-resistance of combustible polymers because of its smoke suppression, low toxicity, and good thermal stability. However, the size of prepared borate is usually in the micrometer range, which makes it difficult to disperse in a polymer matrix, thus hindering its use as fire-retardant material. The preparation and application of borate nanomaterial as flame retardant is considered an effective method. However, the preparation of barium borate nanomaterials as flame retardant has not been reported. In this paper, nanosheets and nanoribbons with different sizes for a new barium borate BaO·4B₂O₃·5H₂O are prepared by hydrothermal method, and characterized by X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR), thermogravimetric analysis-differential scanning calorimetry (TG-DSC), and scanning electron microscope (SEM). The flame-retardant properties of polypropylene (PP)/BaO·4B₂O₃·5H₂O composites are investigated by thermogravimetric analysis (TG), differential scanning calorimetry (DSC) thermal analysis methods and limited oxygen index (LOI) method. Considering the near TG mass losses and the near LOI values for PP with 10% prepared BaO·4B₂O₃·5H₂O nanosheet and nanoribbon, their flame-retardant properties need to be further evaluated by non-isothermal decomposition kinetic method. The apparent activation energy for this decomposition reaction was obtained from the slope by plotting ln(β/T_p²) against 1/T_p according to Kissinger's model. With the reduction of TG mass loss, increased heat absorption in DSC under N₂ atmosphere, increased apparent activation energy E_a for the thermal decomposition of PP/BaO·4B₂O₃·5H₂O composite as well as increased LOI value, the flame-retardant performance of prepared BaO·4B₂O₃·5H₂O samples with PP gradually improved from bulk to nanoribbon to nanosheet. This can be attributed to the decrease in the size of BaO·4B₂O₃·5H₂O samples because the smaller sample size leads to improved dispersion and increased contact area with the polymer. The flame-retardant mechanism is discussed by analyzing the after-flame chars of the PP/BaO·4B₂O₃·5H₂O composite in SEM images, which show that the char layer is more compact and continuous for the PP/BaO·4B₂O₃·5H₂O nanosheet composite. The influence of loading BaO·4B₂O₃·5H₂O nanomaterials on the mechanical properties of PP is also tested using a universal material testing machine, in which the PP/BaO·4B₂O₃·5H₂O nanosheet composite has higher tensile strength. The PP/BaO·4B₂O₃·5H₂O nanosheet composite has the best flame-retardant and mechanical properties, which is promising to be developed for the application as flame-retardant material.     

基于杂交链式反应的可视化免疫分析检测癌胚抗原

构建了基于杂交链反应的比色免疫分析方法,实现了对肿瘤标志物癌胚抗原的检测。在抗原-抗体的特异性结合作用下,在磁珠表面构建夹心式免疫复合物,进一步结合杂交链式反应(HCR)作为信号放大策略,将染料曙红Y嵌入至DNA长链中。在可见光的照射下,能使反应底液中的四甲基联苯胺(TMB)氧化,发生明显的颜色变化,由无色变为蓝色,且与癌胚抗原的浓度呈正相关性。在最优实验条件下,癌胚抗原的浓度在1 pg/mL^5 ng/mL范围内呈线性变化,检出限为1 pg/mL。     

有机化学实验在线开放课程设计的探索与实践

针对以往有机化学实验教学中存在的问题及学生所反映的改进期望,在有机化学实验在线开放课程的开发中,充分利用在线课程与网络教育平台,制作了针对性的教学微视频课程和相应的课件,建立了一套完整的测试模式与题库。通过考测机制,促进和强化学生的实验课前预习。而学生在充分预习的基础上,实现实验预习–现象记录–实验报告完整规范化和一体化,相应提高了学习效率。同时,建立了一套相对客观的成绩评估体系并取得了积极的成果。     

涡旋提取-石墨炉原子吸收光谱法测定土壤中有效态镉

土壤作为农业生产的重要载体,是保障农产品质量安全的关键源头。近年来,随着经济的快速发展,土壤中重金属污染问题日益凸显,已成为世界性的重大环境问题之一。目前针对土壤中重金属的调查分析大多处于总量水平,这并不能全面地评价重金属的生态风险,因为土壤-重金属-生物体之间存在复杂的动态相互作用,土壤中只有部分重金属能被生物体吸收,这部分能被生物体吸收利用的元素以特定的形态存在,这种特定的形态被称之为有效态。土壤中重金属能否被植物吸收主要取决于该元素的有效态[1],因此土壤中重金属有效态含量的测定,对评价和控制其生物毒害作用具有更实际的意义。镉是生物蓄积性强、具有"三致"作用的剧毒元素,会通过食物链富集到人体,从而对人体健康造成危害[2]。目前我国暂未制定土壤中有效态镉的限量标准,关于土壤中有效态镉含量测定方法的研究也较少[3-5],国家标准方法 GB/T 23739-2009(S)《土壤质量有效态铅和镉的测定原子吸收法》前处理采用振荡器低效提取,提取时间长,试剂用量大,提取液根据含量高低选用火焰原子吸收光谱仪或者石墨炉原子吸收光谱仪,操作较繁琐,无法满足批量样品快速分析的要求。文献[3-4]采用超声提取-电感耦合等离子体质谱法,前处理操作简单,但仪器成本较高,方法应用的推广有一定的局限性,且由于土壤样品基体复杂,容易堵塞雾化器导致仪器故障。     

Tailoring the Properties of Diels-Alder Reaction Crosslinked High-performance Thermosets by Different Bismaleimides

A series of Diels-Alder reaction cross-linked thermosets with recyclability and healability were prepared from furan-containing aromatic polyamide and bismaleimides with different chemical structures.The structures of synthesized bismaleimides were confirmed by 1 H nuclear magnetic resonance(1 H-NMR)spectroscopy;their reversible cross-linking with the furanic polyamide was further detected by 1 H-NMR technique and sol-gel transition behavior.The dynamic mechanical analysis and tensile test revealed the variable thermal and mechanical properties of thermosets cross-linked by different bismaleimides and with different molar ratios of maleimide group to furan group(Ima/fur).The tensile test also demonstrated that the better recyclability and solvent-assisted healability of thermosets cross-linked could be achieved by more flexible bismaleimides.This work is expected to provide valuable information for design of recyclable and healable high-performance thermosets with desired properties.     

活性炭/有机质复合相变材料的热-电性能

用活性炭(AC)作为支撑材料,石蜡(PW)、十六酸(PA)和硬脂酸(SA)作为相变主材,通过熔融共混法制备AC/PW、AC/PA和AC/SA复合相变材料,并考察了其热-电性能。结果表明,添加活性炭时有机质均不会泄漏;复合材料充-放热过程中温度场分布都比较均匀,热循环会使材料导热性能略有下降;此外,三种复合材料的电阻率均随压力增加而减小。     

基于钴离子介导信号转换的抗坏血酸比色分析

抗坏血酸是许多生化过程所必需的一种生物小分子。借助于羟基氧化钴纳米片的氧化性和钴离子与硫氰酸根离子之间强的螯合作用,本研究首次报道了一种基于钴离子信号转换的新方法用于抗坏血酸的比色分析。在抗坏血酸存在时,羟基氧化钴纳米片被还原降解产生二价钴离子,钴离子与硫氰酸根离子之间通过螯合作用生成蓝色的[Co(NCS)₄]^_2-阴离子络合物,在625 nm处产生可见吸收信号。实验首先对羟基氧化钴纳米片与抗坏血酸的反应时间、硫氰酸铵和吐温-80的加入量等实验参数进行了优化,当反应时间为5 min,硫氰酸铵(3 mol/L)和吐温-80(10%, w%)的加入体积分别为30 μL和80 μL时,检测体产生最强的吸收信号。在优化的条件下,随着抗坏血酸浓度的增加,检测体系在625 nm处的吸收值线性增强,在0.03～0.45 mmol/L浓度范围内,检测体系在625 nm处的吸收值与AA浓度呈良好的线性关系,线性方程为A₆₂₅=0.638C (mmol/L)+0.042,相关系数R=0.993,检测限(3S/N)为1.5 μmol/L。     

石墨相氮化碳材料在样品前处理中的研究进展

作为一种新型非金属材料,石墨相氮化碳以其独特的优点,如简单的制备方法、优良的化学及热稳定性、良好的生物兼容性和无毒性等,受到越来越多的关注。石墨相氮化碳及其复合材料目前已被广泛应用于电催化、光催化、生物成像等领域。由于具有大的比表面积,同时又是富电子的疏水材料,石墨相氮化碳相关材料被认为是一种理想的样品前处理吸附剂。该文探讨了近年来石墨相氮化碳及其复合材料作为固相萃取、分散固相萃取、磁性固相萃取、固相微萃取吸附剂在样品前处理中的应用,并对未来的发展趋势和应用前景进行了展望,以期为相关领域的研究提供帮助。     

悬浮固化-分散液液微萃取-液相色谱-串联质谱测定纺织废水中磷系阻燃剂

建立了悬浮固化-分散液液微萃取结合液相色谱-串联质谱测定纺织废水中5种痕量磷系阻燃剂的方法。通过对萃取过程中萃取剂、分散剂的种类与体积、盐浓度、溶液pH值等对萃取效率的影响因素优化,确立了最佳萃取条件。采用了密度小于水的十一烷醇（400 μL）为萃取剂,甲醇（300 μL）为分散剂,控制溶液pH值在6~9之间,NaCl添加量为2 g,萃取时间为涡旋2 min。在优化的萃取条件下,该方法在2~100 μg/L均有良好的线性关系,相关系数大于0.995,除二（2,3-二溴丙基）磷酸酯（BIS）的检出限为5 μg/L外,三（2-氯乙基）磷酸酯（TCEP）、三（1,3-二氯-异丙基）磷酸酯（TDCP）、三（1-氮丙啶基）氧化膦（TEPA）和三（2,3-二溴丙基）磷酸酯（TRIS）的检出限均为2 μg/L。后整理、染色和印花等实际废水样品加标试验表明,方法的平均回收率为71.6%~114.5%,RSD为2.7%~11.2%（n=6）。对11个样品进行检测,其中3个废水样品检出TCEP与TDCP化合物,含量为2.6~3.4 μg/L。本方法简单,快速,灵敏度好且环保绿色,能够对纺织废水中的5种痕量磷系阻燃剂进行准确的定性与定量检测。     

金属串配合物[MoMoCo(npo)4(NCS)2]的配位结构及其与电场的关系

应用密度泛函理论B3LYP方法研究了具有分子导线潜在应用的金属串配合物[MoMoCo(npo)4(NCS)2](npo=1,8-萘基-2-酮)的配位结构及其受电场作用的影响。配位方式记为(n,m),其中n、m分别表示4个赤道配体npo^-的O与Co和Mo配位的个数:n=0,1,2,3,4;m=4,3,2,1,0。结果表明:(1)零电场下,基态能量高低为(0,4)>(4,0)>(3,1)≈(1,3)>(2,2),5种配位方式均可稳定存在且互为竞争态。Z方向偶极矩μ(Z)值大小为(0,4)(+)>(1,3)(+)>(2,2)(-)>(3,1)(-)>(4,0)(-)(+、-表示μ(Z)值的正负,与Z方向相同即为正,相反即为负),4个npo^-趋向越一致能量越高极性越大。(2)Mo-Mo具有四重键,键长随μ(Z)值减小而减小,而Mo-Co键长则相反。随μ(Z)值减小前线轨道中πNCS(1)轨道能降低,π'NCS(2)轨道能升高。(3)Z方向电场作用下,除(0,4)外所有配位方式的Mo1-N8键显著增长,结构不稳定。(4)电场作用下前线轨道能级交错,μ(Z)为正值的(0,4)、(1,3)的能隙E_LUMO-HOMO在-Z方向电场中降低更显著,μ(Z)为负值的(2,2)、(3,1)和(4,0)的能隙在Z方向电场中降低更显著。分子极性越大,随电场强度增强能隙降低越显著,分子导电性可能越好。(0,4)、(3,1)和(4,0)可能具有整流效应,但(3,1)和(4,0)的稳定性较低。