部分还原二氧化钛的NMR和EPR研究

Partially reduced TiO₂ nanomaterials have attracted significant interest because of their visible-light activity for catalysis and photodegradation. Herein, we prepared a partially reduced anatase TiO₂ (Re-A-TiO₂) nanoparticle material using a fast combustion method, demonstrating good activity toward decomposing methyl orange under visible light irradiation. The surface structure of the prepared material, after being surface-selectively ¹⁷O-labeled with H₂¹⁷O (¹⁷O-enriched water), was studied via ¹⁷O and ¹H solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and electron paramagnetic resonance (EPR) spectroscopy, and the obtained results were compared to those of non-reduced anatase TiO₂ (A-TiO₂). The EPR results showed that the concentrations of paramagnetic species (i.e., oxygen vacancies (OV) and Ti³⁺) in Re-A-TiO₂ were much higher than that in A-TiO₂, while the former was associated with a higher OV/Ti³⁺ ratio. The intensities of the EPR signals were significantly affected by the adsorbed water, and this phenomenon was explored in combination with ¹H NMR spectroscopy. The ¹H species on Re-A-TiO₂ appeared at larger chemical shifts, denoting the increased acidity of the sample, and these ¹H species on Re-A-TiO₂ were more difficult to remove than those on A-TiO₂. On the other hand, different features were observed for the signals arising from the two-coordinated oxygen atoms (μ₂-O) in ¹⁷O NMR, suggesting a typical anatase TiO₂(101) surface on A-TiO₂, but a more complex surface environment for Re-A-TiO₂. Furthermore, a larger amount of hydroxyl groups (OH) were observed on Re-A-TiO₂ compared to that on A-TiO₂, indicating a larger proportion of exposed (001) facets on Re-A-TiO₂. However, the μ₂-O signals broadened and became similar when the drying temperature was increased to 100 ℃, indicating a non-faceted anatase TiO₂ surface in such conditions. Based on the EPR and NMR results, a significant fraction of the OH species is believed to be formed from the reaction of the paramagnetic centers and adsorbed water molecules. The ¹H→¹⁷O cross polarization (CP) MAS and two-dimensional heteronuclear correlation (2D HETCOR) NMR spectra were used to verify the spatial proximity of the hydrogen and oxygen species, confirming the spectral assignments of a strongly adsorbed water and one type of surface OH species. In particular, the ¹H NMR signals at approximately 11 ppm were ascribed to the hydrogen species in the intramolecular hydrogen bond. In summary, this study investigated the paramagnetic species and surface structure of anatase TiO₂ materials by combining EPR along with ¹H and ¹⁷O solid-state NMR spectroscopy. The differences in the surface structures of Re-A-TiO₂ and A-TiO₂ should be closely related to their different properties toward the photodegradation of methyl orange.     

不可燃氟代碳酸酯基钠离子电池电解液

Lithium-ion batteries (LIBs) are widely used in cellphones, laptops, and electric cars owing to their high energy density and long operational lifetime. However, their further deployment in large-scale energy storage systems is restricted by the uneven distribution of lithium resources (~0.0017% (mass fraction, w) in the Earth's crust). Therefore, alternative energy storage systems composed of abundant elements are of urgent need. Recently, sodium-ion batteries (SIBs) have attracted significant attention and are considered to be a potential alternative for next-generation batteries owing to abundant sodium resources (~2.64% (w) of the Earth's crust), suitable potential (−2.71 V), and low cost. SIBs are similar to LIBs in terms of their physical and electrochemical properties. Previous studies have mainly focused on SIB storage materials, including hard carbon, alloys, and hexacyanoferrate, while the safety of SIBs remains largely unexplored. Similar to LIBs, the current electrolytes used in SIBs are mainly composed of flammable organic carbonate solvents (or ether solvents), sodium salts, and functional additives, which pose possible safety issues. Moreover, the chemical activity of sodium is much higher than that of lithium, leading to a higher risk of fire, thermal runaway, and explosion. To overcome this problem, herein we propose a fluorinated non-flammable electrolyte composed of 0.9 mol∙L⁻¹ NaPF₆ (sodium hexafluorophosphate) in an intermixture of di-(2, 2, 2 trifluoroethyl) carbonate (TFEC) and fluoroethylene carbonate (FEC) in a 7 : 3 ratio by volume. Its physical and electrochemical properties were studied by ionic conductivity, direct ignition, cyclic voltammetry, and charge/discharge measurements, demonstrating excellent flame-retarding ability and outstanding compatibility with sodium electrodes. The electrochemical tests showed that the Prussian blue cathode retained a capacity of 84 mAh∙g⁻¹ over 50 cycles in the prepared electrolyte, in contrast to the rapid capacity degradation in a flammable conventional carbonate electrolyte (74 mAh∙g⁻¹ with 57% capacity retention after 50 cycles). To test the practical application of the proposed electrolyte, a hard carbon anode was used and exhibited exceptional performance in this system. The enhancement mechanism was further verified by Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning emission microscopy (SEM) investigations. Polycarbonate on the surface of the cathode played an important role for the studied electrolyte system. The polycarbonate may originate from FEC decomposition, which can enhance the ionic conductivity of the solid electrolyte interface (SEI) layer and reduce impedance. Hence, we believe that this proposed electrolyte may provide new opportunities for the design of robust and safe SIBs for next-generation applications.     

金纳米粒子的制备及在汞离子检测中的应用——推荐一个分析化学综合实验

Gold nanoparticles (Au NPs) were synthesized by reducing HAuCl₄ with sodium citrate. The sensitivity and selectivity of gold amalgam catalytic degradation of rhodamine B (RhB) system for mercury detection were investigated by fluorescence spectroscopy and ultraviolet-visible absorption spectroscopy. In the experiment, students' interest in scientific research and exploratory spirit will be stimulated, students' comprehensive experimental operation skills and subjective initiative will be improved, the understanding and application of nanoparticles preparation, characterization, catalytic reaction knowledge and metal ion analysis methods will be enhanced. Furthermore, the innovative thinking and scientific spirit of the students will be cultivated.     

钴催化双齿导向基辅助的1-萘胺衍生物与醇的区域选择性碳氢键烷氧基化反应

研究了吡啶酰胺双齿导向的钴催化1-萘胺衍生物的区域选择性碳氢键烷氧基化反应.研究发现不仅一元醇可以作为烷氧化剂在标准条件下较好地实现1-萘胺C(8)位的烷氧化反应,而且具有多重用途的脂肪二元醇以及低聚乙二醇,也可以以中等的收率得到相应的目标化合物,这可能是钴催化碳氢键活化构筑碳氧键的首次发现.此外,利用这个实验方法,以氘代甲醇为烷氧化试剂实现了同位素标记的8-烷氧基取代的1-萘胺衍生物的合成.通过控制实验,发现该反应中吡啶酰基是最佳的双导向基团,而且反应过程可能经历了单电子转移机理.     

Three Zinc(Ⅱ) Complexes Based on 2-Carboxylic Acid-4-nitropyridine-1-oxide: Synthesis,Crystal Structure,and Fluorescence Properties

Three new metal-organic complexes, namely [Zn(POA)2(H2O)2](1), [Zn(POA)2(H2O)2]·2H2O(2) and [Zn(POA)2]n(3), have been synthesized by organic ligand 2-carboxylic acid-4-nitropyridine-1-oxide(POA) and zinc(Ⅱ) ions. The structures of complexes 1~3 are characterized by single-crystal X-ray analysis, XRD powder diffraction analysis, infrared spectroscopy and thermal stability analysis method. Complex 1 belongs to monoclinic system, space group C2/c with a = 22.8215(15), b = 7.5613(16), c = 10.048(3) ?, β = 109.47°, V = 1634.7(6) ?~3, Z = 4, F(000) = 944, Dc = 1.900 g/cm^3, C(12)H(10)N4O(12)Zn, Mr = 467.61 and μ = 1.584 mm^-1. The whole molecule presents "V" shape. Complex 2 is a centrosymmetric structure in triclinic system with space group P1: a = 7.4728(5), b = 7.6825(6), c = 8.5184(6) ?, α = 65.975(2), β = 79.87(2), γ = 89.855(2)°, V = 4384.1(5) ?~3, Z = 1, F(000) = 256, Dc = 1.908 g/cm^3, C(12)H(14)N4O(14)Zn, Mr = 503.64 and μ = 1.492 mm^-1. Complex 3 is a one-dimensional chain structure belonging to monoclinic system and space group P21/c with a = 4.9456(6), b = 12.5322(14), c = 11.2514(13) ?, β = 97.313(11)°, V = 6916.8(14) ?~3, Z = 2, F(000) = 432, Dc = 2.072 g/cm^3, C(12)H6N4O(10)Zn, Mr = 431.58, and μ = 1.852 mm^-1. In three complexes, six oxygen atoms from the surrounding coordination atoms form a ZnO6 distorted octahedral coordination geometry around the zinc ions. Meanwhile, fluorescent properties of the three complexes were investigated at room temperature. The fluorescence spectroscopic analysis demonstrated that the ligand POA shows red-shift after coordinating with the zinc(Ⅱ) ions.     

绿色单体二氧化碳参与的新型聚合反应

二氧化碳（CO₂）是一种丰富、廉价、无毒以及可再生的一碳资源,也是一种可用于聚合的绿色单体.基于CO₂的聚合是近年来的研究热点之一.目前广泛报道的是CO₂和环氧单体的聚合反应,经过几十年的发展已经成功实现工业化生产.最近几年,一些CO₂参与的新型聚合反应被陆续报道,这些工作大都通过两种途径实现从CO₂到高分子材料的转变.第一个途径是先将CO₂转化为可以聚合的单体,例如：内酯、环状碳酸酯和2,5-二呋喃甲酸等,再利用开环或者逐步聚合将单体转化为聚合物;另一个途径是直接以CO₂为单体和其他类型单体共聚得到聚合物.这两种途径对于发展CO₂参与的新型聚合反应,拓展CO₂基聚合物种类都具有重要意义.本综述按照CO₂直接还是间接参与聚合反应分类总结了近年来在CO₂制备高分子材料方面的进展,并对未来发展方向进行了简单阐述.     

双席夫碱铜配合物修饰玻碳电极用于碳酸饮料中苯甲酸的测定

利用溶液法制备双席夫碱铜配合物(M),采用电沉积法将制备的M沉积在玻碳电极(GCE)上制备了双席夫碱铜配合物修饰电极(M/GCE),用于测定碳酸饮料中的苯甲酸的含量。元素分析和红外光谱结果显示,试验成功制备了M;电沉积过程循环伏安曲线变化结果显示M已成功沉积在了GCE表面;扫描电镜(SEM)结果显示M/GCE表面已形成了一层聚合物膜。三电极体系选用M/GCE(工作电极)、饱和甘汞电极(参比电极)、铂丝电极(辅助电极);支持电解质采用0.1mol·L~(-1) KCl溶液;电化学方法选用循环伏安法(CV),扫描速率为50mV·s~(-1)。结果表明,苯甲酸在M/GCE上的氧化峰电位和还原峰电位分别位于-0.007,-0.359V附近,电极反应可逆性良好,受扩散控制。苯甲酸浓度与其对应的氧化峰电流在0.001 0～2.000 0mmol·L~(-1)内呈线性关系,检出限(3S/N)为0.27μmol·L~(-1)。将电极在4℃下放置7d后,苯甲酸氧化峰电流下降了4.8%。以雪碧样品为基质进行了加标回收试验,回收率为97.6%～102%,测定值的相对标准偏差(n=5)为1.2%。     

CdS@g-C3N4复合核壳纳米微粒的制备与光催化性能

采用水热法,在乙二胺和EDTA-2Na作用下,成功制备了CdS@g-C3N4复合核壳纳米微粒,并探讨了其生长机理。结果显示:CdS@g-C3N4复合核壳纳米微粒的比表面积是纯CdS纳米颗粒的14.0倍,具有良好的光催化活性和光稳定性。当反应条件为180℃、4 h、CdS/g-C3N4质量比1.9∶1时,CdS@g-C3N4的可见光催化性能最好,300 W氙灯光照2 h,RhB的降解率达95.2%,明显高于纯CdS。重复使用3次后,CdS@g-C3N4形貌、结构及光催化性能无明显变化。     

一种蒽醌类荧光探针的合成及对氟离子的检测性能

以1,4-二羟基蒽醌为荧光团,叔丁基二甲基氯硅烷为识别基团,设计合成了新型氟离子探针分子1,4-二-(叔丁基-二甲基-硅氧基) 蒽醌(AQTB1),其结构经¹H NMR, ¹³C NMR和MS(ESI)表征。采用FL和UV-Vis详细研究了响应时间、溶液pH值、干扰离子、氟离子浓度对探针AQTB1检测性能的影响。结果表明：探针AQTB1在pH=3~12的缓冲溶液中,实现了对氟离子的高效检测,并不受干扰离子影响。通过FL, IR和MS(ESI)对探针AQTB1检测机理进行研究,结果表明：加入氟离子后,探针分子中的Si-O键断裂,荧光较弱的AQTB1转化为荧光较强的1,4-二羟基蒽醌,实现氟离子的精确定量。实际样品分析实验中,3种不同水样中氟离子的加标回收率为88.0%～109.5%,相对标准偏差(RSD)低于8.5%。