云蒸霞蔚——多色双喷泉实验

本实验在氨气和氯化氢气体的单喷泉实验基础上设计了集两种气体的制备、收集、验满、尾气处理、气体反应、喷泉实验与试剂回收利用于一体的连续性实验,喷泉部分涉及到的实验原理有氨气与硫酸铜溶液的配位反应、氨气与氯化钴溶液的沉淀反应、无色酚酞溶液和酸性对硝基苯酚溶液在碱性环境下的变色反应,以及氯化铁和硫氰化钾在弱酸性条件下的反应等。本实验的主要仪器装置由团队自行设计、定制,操作简便,玻璃活塞还可控制喷发顺序,实现多色多样喷泉,伴随氯化铵生成时的袅袅白烟,云蒸霞蔚,煞是壮观。另外,我们设计了多角度的互动方案,针对不同程度知识背景的受众传授知识,让参观者真切感受到化学的魅力。     

Synthesis,Structure, and Magnetic Properties of a Series of Dinuclear Lanthanide Complexes Assembled by Acetate and a Schiff Base Ligand

Five dinuclear lanthanide complexes [Ln₂L₂(NO₃)₂(OAc)₄] · 2CH₃CN [Ln = Gd ( 1 ), Tb ( 2 ), Dy ( 3 ), Ho ( 4 ), and Er ( 5 )] [L = 2‐((2‐pyridinylmethylene)hydrazine)ethanol] were synthesized from the reactions of Ln(NO₃)₃ · 6H₂O with L and CH₃COOH in the presence of triethylamine. Their crystal structures were determined. They show similar dinuclear cores with the two lanthanide ions bridged by four acetate ligands in the μ₂‐η¹:η² and μ₂‐η¹:η¹ bridging modes. Each Ln^III ion in complexes 1 – 5 is further chelated by one L ligand and one nitrate ion, leading to the formation of a nine‐coordinated mono‐capped square antiprism arrangement. The dinuclear molecules in 1 – 5 are consolidated by hydrogen bonds and π ··· π stacking interactions to build a two‐dimensional sheet. Their magnetic properties were investigated. It revealed antiferromagnetic interactions between the Gd^III ions in 1 and ferromagnetic interactions between the Tb^III ions in 2 . The profiles of χ_mT vs. T curves of 3 – 5 reveal that the magnetic properties of 3 – 5 are probably dominated by the thermal depopulation of the Stark sublevels of Ln^III ions.     

A Mini Review on the Functional Biomaterials Based on Poly(lactic acid) Stereocomplex

Poly(lactic acid) stereocomplex (sc-PLA) prevails over homo-poly(lactic acid)s in many aspects and showed great potential as biomaterials depending on its extraordinary biological, thermal, and mechanical properties. In the past few years, sc-PLA has gained tremendous attention as a new approach to the development of new types of functional biomaterials. This paper summarizes recent progress in the application of the concept of sc-PLA in the design and fabrication of stabilized nanoparticles and in situ gelling hydrogels for biomedical applications.     

基于4-氨基-1,2,4-三唑和多金属氧酸盐为杂化配体的CuⅡ和CuⅠ配合物的水热合成及光催化性能

在水热条件下,制备了2个基于多金属氧酸盐（POM）的Cu^Ⅱ和Cu^Ⅰ新型杂化配合物材料,即[Cu₂（4-NH₂-trz）₄（Mo₈O₂₆）（H₂O）₄]·5H₂O（1）和[Cu₄（4-NH₂-trz）₄Mo₈O₂₆]（2）（4-NH₂-trz=4-氨基-1,2,4-三唑）。通过单晶X射线衍射、傅里叶变换红外光谱和粉末X射线衍射分析确定了它们的结构。在配合物1中,4-氨基-1,2,4-三唑双齿配体连接2个相邻的Cu^Ⅱ中心形成双核结构单元,这些双核结构单元进一步通过Mo₈O₂₆^4-连接形成一维（1D）的杂化配位结构。在配合物2中,4-氨基-1,2,4-三唑双齿配体连接相邻Cu^Ⅰ中心构筑了独特的[Cu₄（4-NH₂-trz）₄]_n一维螺旋链,这些左手和右手的一维螺旋链再通过（β-Mo₈O₂₆）^4-连接形成2D杂化骨架。光催化实验研究表明,样品1和样品2对于不同有机染料（亚甲基蓝（MB）、罗丹明B（RhB）和甲基橙（MO））具有很好的光催化降解能力。     

新型BiOI/g-C3N4纳米片复合光催化剂的制备及其可见光催化活性增强

近年来, 石墨型氮化碳(g-C3N4)作为一种n型半导体光催化剂材料, 由于具有较好的热稳定性和化学稳定性, 同时具有可调的带隙结构和优异的表面性质而备受人们关注. 然而, 传统的g-C3N4块体材料存在比表面积小、光响应范围窄和光生载流子易复合等缺陷, 制约着其光催化活性的进一步提高. 因此, 人们开发了多种技术对块体状g-C3N4材料进行改性,其中构建基于g-C3N4纳米薄片的异质结复合光催化材料被认为是强化g-C3N4载流子分离效率, 进而提高其可见光催化活性的重要手段. BiOI作为一种窄带隙的p型半导体光催化剂, 具有强的可见光吸收能力和较高的光催化活性, 同时它与g-C3N4纳米薄片具有能级匹配的带隙结构. 因此, 基于以上两种半导体材料的特性, 构建新型的BiOI/g-C3N4纳米片复合光催化剂材料不仅能够有效提高g-C3N4的可见光利用率, 而且还可以在n型g-C3N4和p型BiOI界面间形成内建电场, 极大促进光生电子-空穴对的分离与迁移效率.为此, 本文通过简单的一步溶剂热法在g-C3N4纳米薄片表面原位生长BiOI纳米片材料, 成功制备了新型的BiOI/g-C3N4纳米片复合光催化剂. 利用X射线衍射仪(XRD), 场发射扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见漫反射光谱和瞬态光电流响应谱对所合成复合光催化剂的晶体结构、微观形貌、光吸收性能和电荷分离性能进行了表征测试. XRD, SEM和TEM结果显示, 结晶完好的BiOI呈小片状均匀分散在g-C3N4纳米薄片表面; 紫外漫反射光谱表明, 纳米片复合材料的吸光性能较g-C3N4薄片有显著提升; 瞬态光电流测试证明, 复合材料较单一材料有更好的电荷分离与迁移性能.在可见光催化降解RhB的测试中, BiOI/g-C3N4纳米片复合光催化剂显示出了优异的催化活性和稳定性, 其光降解活性分别为纯BiOI和g-C3N4的34.89和1.72倍; 自由基捕获实验发现, 反应过程中的主要活性物种为超氧自由基(·O2-), 即光生电子主导整个降解反应的发生. 由此可见, 强的可见光吸收能力和g-C3N4与BiOI界面处形成的内建电场协同促进了g-C3N4纳米薄片的电荷分离, 进而显著提高了该复合材料的可见光催化降解活性. 此外, 本文初步验证了在BiOI/g-C3N4纳米片复合光催化体系内光生电荷是依据"双向转移"机制进行分离和迁移的, 而非"Z型转移"机制.     

Gd0.2Ce0.8O1.9纳米颗粒对固体氧化物电解池La0.6Sr0.4Co0.2Fe0.8O3-δ阳极 析氧反应的影响

化石燃料的使用排放了大量CO2,对气候和环境造成了日益严重的危害.固体氧化物电解池(SOEC)能够利用可再生能源产生的电能将CO2高效转化成CO,降低CO2排放的同时,又能减少化石燃料的使用,近年来受到研究者的广泛关注.相比于低温液相CO2电还原,SOEC高的运行温度保证了其较高的反应速率,即较高的电流密度.典型的SOEC单电池由多孔阴极、致密电解质和多孔阳极以三明治的方式组装而成.CO2分子在阴极得到两个电子解离成CO和一个O2–;生成的O2–通过致密电解质传导至阳极,在阳极失去四个电子发生析氧反应(OER)生成一个O2.相比于两电子的阴极反应,阳极四电子的析氧反应更难进行,可能是整个电极过程的速控步,因此开发高性能的阳极材料有望显著提高SOEC的CO2电还原性能.La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF)因具有较高的混合离子-电子导电性而被用作SOEC阳极材料,但受LSCF-气体两相界面的限制,其OER性能较低.研究表明,LSCF-掺杂的CeO2-气体所构成的三相界面相比于LSCF-气体两相界面具有更高的电化学反应活性,即OER反应更易在三相界面进行.因此,本文将Gd0.2Ce0.8O1.9(GDC)纳米颗粒浸渍到SOEC LSCF阳极来提高其OER活性,考察了纳米颗粒浸渍量(3,5,10和20 wt%)对SOEC电化学性能的影响.结果表明,SOEC的电化学性能随浸渍量的增加而逐渐升高,当GDC纳米颗粒浸渍量为10 wt%时(10GDC/LSCF),SOEC的电化学性能达到最高,在800 oC和1.6 V的电流密度为0.555 A cm–2,是LSCF阳极SOEC性能的1.32倍.继续增加浸渍量到20 wt%,电化学性能反而开始下降.电化学阻抗谱测试结果表明,GDC纳米颗粒的加入减小了SOEC的极化电阻.对应的弛豫时间分布函数解析结果表明10GDC/LSCF阳极上的OER由四个基元反应构成.电镜和O2-程序升温脱附结果表明,GDC纳米颗粒的加入显著增加了10GDC/LSCF阳极三相界面和表面氧空位的数量以及体相氧的流动性,从而促进了OER四个基元反应的反应速率,降低了这几个过程的极化电阻,因而降低了OER反应的极化电阻,提高了SOEC电还原CO2的电化学性能.     

密度泛函理论计算研究表面应力对钯催化乙炔选择性加氢活性与选择性的影响（英文）

在石油催化裂解过程中,除了生成乙烯、丙烯及丁烯等烯烃,还会产生部分炔烃.目前工业上通常采用炔烃选择性加氢转化为对应的单烯烃,以除去其中炔烃.由于产品烯烃中的炔烃等杂质含量需极低,这就对用于加氢催化剂的活性和选择性提出了很高的要求,即催化剂需要选择性吸附炔烃并加氢,而不损失其中的烯烃.经过前期大量的基础研究工作,目前工业中炔烃选择性加氢应用最广泛的催化剂是负载型钯基催化剂.然而,单独的钯金属选择性并不理想,因而对其选择性以及活性进行调控成为了当前关注的研究课题.本文采用密度泛函理论计算结合微观反应动力学模拟手段,研究了钯金属表面应力存在条件下的活性与选择性,以及形成次表层物种的可能性和形成后的活性与选择性.研究发现,改变钯金属的晶格参数与表面应力,反应物、表面反应中间体和产物的吸附能都会产生相应的变化,且吸附能与晶格参数的变化存在线性关系,晶格参数越大,吸附越强.利用表面反应过渡态能量与初始态能量之间的线性关系,相应的乙炔加氢生成乙烯的反应速率可以通过微观反应动力学模拟得到.结果显示,不同晶格参数的钯催化剂催化乙炔加氢生成乙烯的反应活性位于相应火山型曲线的强吸附侧,即减弱乙炔和氢的吸附强度可提高乙烯的生成速率.在此基础上,本文研究了不同表面应力的钯催化剂在次表面吸附不同覆盖度碳原子和氢原子的情况,发现晶格参数越大越有利于碳原子和氢原子在次表面的吸附.同时,研究发现在次表面碳掺杂的条件下,不同表面应力条件下的钯催化剂的活性均有所增强.此外,由于乙烯在所有研究的钯催化剂表面脱附比进一步加氢容易,因而乙烯都可以选择性生成.     

Microwave-hydrothermal synthesis and photocatalytic properties of biomass charcoal/TiO2 nanocomposites

Biomass charcoal-doped titanium dioxide (C/TiO₂) composites were proposed by microwave-hydrothermal and calcination method using tetrabutyl titanate as the titanium source and lignin as the carbon source. TiO₂ crystals with different morphologies could be successfully adsorbed onto the surface of biomass charcoal. These products were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG), derivative thermogravimetric (DTG), UV–vis diffuser flection spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FT-IR), and Brunauer–Emmett–Teller (BET). The photocatalytic activities of the as-obtained composites were checked under visible light irradiation. The results showed that both the microwave-hydrothermal temperature and time played an important role in the microstructure and photocatalytic activity of the samples. The rapid microwave-hydrothermal with the thermal post-treatment provides a promising route for the fabrication of biomass charcoal-doped nanocomposites materials.     

Enhanced Photodynamic Therapy by Reduced Levels of Intracellular Glutathione Obtained By Employing a Nano‐MOF with CuII as the Active Center

In photodynamic therapy (PDT), the level of reactive oxygen species (ROS) produced in the cell directly determines the therapeutic effect. Improvement in ROS concentration can be realized by reducing the glutathione (GSH) level or increasing the amount of photosensitizer. However, excessive amounts photosensitizer may cause side effects. Therefore, the development of photosensitizers that reduce GSH levels through synergistically improving ROS concentration in order to strengthen the efficacy of PDT for tumor is important. We report a nano‐metal–organic framework (Cu^II‐metalated nano‐MOF {CuL‐[AlOH]₂}_n (MOF‐2, H₆L=mesotetrakis(4‐carboxylphenyl)porphyrin)) based on Cu^II as the active center for PDT. This MOF‐2 is readily taken up by breast cancer cells, and high levels of ROS are generated under light irradiation. Meanwhile, intracellular GSH is considerably decreased owing to absorption on MOF‐2; this synergistically increases ROS concentration and accelerates apoptosis, thereby enhancing the effect of PDT. Notably, based on the direct adsorption of GSH, MOF‐2 showed a comparable effect with the commercial antitumor drug camptothecin in a mouse breast cancer model. This work provides strong evidence for MOF‐2 as a promising new PDT candidate and anticancer drug.     

Mechanofluorochromic Carbon Nanodots: Controllable Pressure‐Triggered Blue‐ and Red‐Shifted Photoluminescence

Mechanofluorochromic materials, which change their photoluminescence (PL) colors in responding to mechanical stimuli, can be used as mechanosensors, security papers, and photoelectronic devices. However, traditional mechanofluorochromic materials can only be adjusted to a monotone direction upon the external stimuli. Controllable pressure‐triggered blue‐ and red‐shifted PL is reported for C‐dots. The origin of mechanofluorochromism (MFC) in C‐dots is interpreted based on structure–property relationships. The carbonyl group and the π‐conjugated system play key roles in the PL change of C‐dots under high pressure. As the pressure increases, the enhanced π–π stacking of the π‐conjugated system causes the red‐shift of PL, while the conversion of carbonyl groups eventually induces a blue‐shift. Together with their low toxicity, good hydrophilicity, and small size, the tunable MFC property would boost various potential applications of C‐dots.