Luminescent Nanofibers Fabricated from Phenanthroimidazole Derivatives by Organogelation: Fluorescence Response towards Acid with High Performance

Nanofibers based on phenanthroimidazole derivatives PCC , PDC , and PSC were fabricated by organogelation processes, and their fluorescence sensory properties towards acid were investigated. It was found that the emission of PCC in the nanofiber‐based film could be quenched significantly upon exposure to gaseous TFA due to the formation of protonated PCC , in which ICT (intramolecular charge transfer) would occur. On the other hand, TFA vapor led to the emitting colors of PDC and PSC in the nanofiber‐based films to turn to yellow and green from sky blue and blue, respectively. Additionally, we found that the decay times of PCC were 0.1 s and 1.9 s in probing the saturated vapor of TFA in nanofiber‐based film and in spin‐coated film, respectively. The results suggested that the high surface‐to‐volume ratio and large interspace in the nanofiber‐based networks favored the enhanced adsorption, accumulation, and diffusion of gaseous molecules, resulting in such a high performance.     

提升化学学科核心素养的高中化学教学——以“金属的防护”为例

针对人教版选修1《化学反应原理》第4章第3节“金属的腐蚀与防护”课时2“金属的防护”进行教学实践探索,融合STEM教育理念促进知识与社会生活结合。选用任务情境“家用电热水器碳钢内胆防腐”,通过实验探究构建起电化学防护的认知模型,再将模型应用于实际生产生活问题的解决,进行热水器内胆的防腐设计。在真实情境问题的解决中,将知识、方法、应用等3者融合,培养学生的问题意识和创新思维,逐步内化并表现出化学学科核心素养。     

高中化学“电负性”的项目式教学*——甲醛的危害与去除

电负性是高中化学选择性必修课程“物质结构与性质”模块的重要概念。本课例采用“项目式教学”的方式,在对“甲醛的危害与去除”的分析、讨论与实验过程中,加深对电负性概念的理解,同时尝试利用电负性分析与预测物质的化学性质,体会电负性概念的使用价值。     

超高效液相色谱-四极杆/静电场轨道阱高分辨质谱法非靶向筛查苹果中苯脲类农药

建立了超高效液相色谱－四极杆/静电场轨道阱高分辨质谱（UPLC-Q/Orbitrap HRMS）非靶向筛查苹果中苯脲类农药的方法。样品采用QuEChERS法提取净化,Acquity BEH C18色谱柱（100 mm × 2.1 mm,1.7 μm）分离,以甲醇和含0.1%甲酸的水溶液为流动相进行梯度洗脱,在电喷雾正离子模式下采用四极杆/静电场轨道阱高分辨质谱进行检测。将13种苯脲类除草剂和9种苯甲酰脲类杀虫剂按化学结构分为4类。首先通过对4类22种典型苯脲类农药标准品的准分子离子和二级质谱碎片进行分析,总结苯脲类农药的质谱裂解规律如下：绿麦隆等9种苯脲类除草剂的主要特征离子碎片为m/z 72.044 59,可通过特征丢失中性分子二甲胺（m/z 45.058 03）产生特征离子碎片;绿谷隆等4种苯脲类除草剂可通过特征丢失中性分子甲醇［CH3OH］或卤化氢［HR1］（R=Cl,Br,F）产生离子碎片;除虫脲等7种含氟苯甲酰脲杀虫剂的主要特征离子碎片为 m/z 158.040 47、141.015 00,也可发生特征中性丢失2,6-氟苯甲酰胺结构［C8H3F2O2NH2］（m/z 183.013 21）;杀铃脲等2种含氯苯甲酰脲类杀虫剂的主要特征离子碎片为m/z 156.020 25、138.993 76、113.015 28。利用该方法对北京12份市售苹果进行非靶向筛查,在1份样品中筛查出绿麦隆。该方法可为快速筛查农产品中相似结构特征的苯脲类化合物提供参考。     

Self-assembled Nanosheets of Perylene Monoamide Derivative as Sensitive Fluorescent Biosensor for Exonuclease III Activity

Enzymes containing 3'→5' exonuclease activities play an important role in various key cellular and physiological processes. The development of fluorescence biosensor is an efficient method to detecting enzyme activity. Herein, a fluorescence resonance energy transfer(FRET) "on" and "off" strategy for detecting exonuclease III(Exo III) activity has been developed. We report here that the double-stranded DNA(dsDNA) enables to bind tightly to self-assembled nanosheets of cationic perylene monoimide derivative(PMI-O7) through electrostatic interaction, and the 6-carboxyfluorescein(FAM)-modified dsDNA could be efficiently quenched via FRET between FAM and PMI-O7. Upon the addition of Exo III, the dsDNA will be digested and the FAM fluorophore will be released, resulting in the fluorescence recovery of FAM. This method provides a simple and sensitive biosensor platform with a low detection limit of 0.077 U/mL for Exo III. Importantly, this method exhibits similar and calibration curves for the detection of Exo III in both buffer and fetal bovine serum samples, indicating that this platform has potential to detect Exo III activity in complex samples.     

单一基质白光荧光粉Na3Sc2(PO4)3∶Tm3+,Dy3+的合成及发光性质

采用高温固相法成功制备了Na₃Sc_2-x-y(PO₄)₃∶xTm³⁺,yDy³⁺荧光粉,利用X射线衍射仪、扫描电子显微镜和荧光光谱仪对荧光粉进行了物相、形貌和发光性能进行了表征。 在Na₃Sc₂(PO₄)₃∶0.06Tm³⁺,yDy³⁺荧光粉中,物质的量分数6%的Tm³⁺和6%的Dy³⁺在360 nm激发下呈现出白光发射,其发射光谱在460~685 nm范围内存在Tm³⁺位于457 nm的特征发射峰,对应于Tm³⁺的³H₆→¹D₂跃迁,以及Dy³⁺位于483、577和672 nm处的3个特征发射峰,分别对应于Dy³⁺的⁴F_9/2→⁶H_15/2、⁴F_9/2→⁶H_13/2和⁴F_9/2→⁶H_11/2的跃迁。 观测到Na₃Sc₂(PO₄)₃∶Tm³⁺荧光粉的发射光谱与Na₃Sc₂(PO₄)₃∶Dy³⁺的激发光谱有较好的重叠,且Tm³⁺的荧光寿命随Dy³⁺浓度的增加逐渐降低,因此在Na₃Sc₂(PO₄)₃∶Tm³⁺,Dy³⁺荧光粉中存在Tm³⁺向Dy³⁺的能量传递。 利用Dexter和Reisfeld近似分析了能量转移机制,发现从Tm³⁺到Dy³⁺的能量传递临界距离为1.6 nm,能量传递过程是通过偶极-偶极相互作用进行的。 Na₃Sc₂(PO₄)₃∶0.06Tm³⁺,0.06Dy³⁺荧光粉具有较好的耐受热猝灭性能,在423、473和523 K时的发射强度分别为298 K时发射强度的97.6%、89.2%和78.6%。 随着Dy³⁺浓度的增加,Na₃Sc₂(PO₄)₃∶0.06Tm³⁺,yDy³⁺荧光粉的发光颜色由蓝色转变为白色,再由白色变黄色。 Na₃Sc₂(PO₄)₃∶Tm³⁺,Dy³⁺荧光粉作为一种可调色或单相白光荧光粉在发光二极管上具有潜在的应用前景。     

Effect of poly(methylhydrogen)siloxane modification on adjusting mechanical properties of bamboo flour‐reinforced HDPE composites

Cellulose - Poly(methylhydrogen)siloxane (PMHS) was applied for hydrophobic modification of bamboo flour (BF) at room temperature based on the dehydrogenation between hydroxyl groups of BF and...     

含有1,4,7-三苄基-1,4,7-三氮杂环壬烷的两个双核铜配合物的合成、表征及其与DNA的相互作用

合成了2个含有1,4,7-三苄基-1,4,7-三氮杂环壬烷（Bn₃tacn）的双核铜配合物：[Cu₂（Bn₃tacn）₂（m-bdc）（CH₃CN）₃（H₂O）₂]ClO₄（1）和[Cu₂（Bn₃tacn）₂（OH）₂]（ClO₄）₂（2）。配合物1由间苯二甲酸采取单双齿方式桥连Cu（Ⅱ）离子,配合物2由OH桥连。配合物1和2晶体均属于单斜晶系,分别为P2₁/c空间群和C2/c空间群。分别对2个配合物进行了红外光谱、紫外-可见光谱和元素分析表征。研究了配合物1与DNA的相互作用,对配合物2进行了循环伏安测试。     

LF-NMR结合化学模式识别鉴别油脂种类及餐饮废弃油脂

应用主成分分析(Principal component analysis,PCA)和聚类分析法(Cluster analysis,CA)对9种(27个)常见食用植物油及100个餐饮废油的低场核磁共振(Low-field nuclear magnetic resonance,LF-NMR)(T2)弛豫特性数据进行分析。结果表明:在正常食用油种类区分方面,主成分分析的效果较优,9种食用油在主成分分布图上按种类正确分组,边界清晰。而在正常食用油与餐饮废油的区分方面,聚类分析效果较优,引入30个待测样本后,聚类分析(127个样品,欧式距离=5)的正确率为94.49%,分析误判率为5.51%,分组效果良好。LF-NMR结合化学模式识别可实现对油脂种类及餐饮废弃油脂的鉴别。     

固相萃取/高效液相色谱-串联质谱法测定黄瓜及土壤中的春雷霉素残留

建立了测定黄瓜和土壤中春雷霉素残留的固相萃取/高效液相色谱-串联质谱(SPE/HPLC-MS/MS)方法。黄瓜和土壤样品分别经1%甲酸的甲醇、0.5%甲酸水提取后,采用MCX固相萃取柱净化,以Waters Xbridge BEH Amide色谱柱分离,0.2%甲酸水-乙腈溶液进行梯度洗脱,电喷雾正离子(ESI+)模式电离,多反应监测(MRM)模式检测,基质匹配标准曲线外标法定量。该方法灵敏、准确、简单快速、重复性好,在2~250μg/L浓度范围内,不同基质中春雷霉素的线性相关系数均大于0.999,检出限为0.002 mg/kg,定量下限为0.008 mg/kg;在0.008、0.040、0.200、0.400 mg/kg 4个加标水平下,春雷霉素在黄瓜和土壤样品中的平均回收率为77.5%~97.0%,相对标准偏差为2.6%~10.7%,能够满足黄瓜及土壤中春雷霉素残留的检测需求。应用该法对田间样品进行检测,结果表明,春雷霉素在黄瓜中的残留量不超过0.053 mg/kg,小于我国规定的黄瓜中最大残留限量(0.2 mg/kg);土壤中春雷霉素的残留量不超过0.013 mg/kg。