GdPO4∶Sm3+荧光粉的焙烧温度和掺杂浓度的优化及发光和磁性能

以GdPO₄为基质,Sm³⁺为激活剂,采用水热法合成了纳米荧光粉前驱体,分别在800、900、1 000、1 100和1 200℃下焙烧,得到一系列GdPO₄∶Sm³⁺荧光粉。首先探究了GdPO₄∶Sm³⁺的最佳焙烧温度;其次研究了Sm³⁺掺杂浓度对GdPO₄∶Sm³⁺荧光性能的影响;最后研究了GdPO₄∶2% Sm³⁺的高温荧光性能和磁性能。使用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、磁强计和荧光分光光度计(FL)对荧光粉的晶体结构、形貌、发光和磁性能进行了表征。结果表明：荧光粉的晶体结构由前驱体六方晶系GdPO₄·H₂O∶Sm³⁺变为单斜晶系的GdPO₄∶Sm³⁺,形貌由纳米棒变为无规则块体。当焙烧温度为1 000℃,Sm³⁺掺杂浓度为2%时,荧光粉的发光强度和荧光寿命达到最大值。GdPO₄∶2% Sm³⁺中Sm³⁺之间能量传递类型为电偶极-电偶极相互作用,能量传递的临界距离为1.646~1.884 nm。最佳样品GdPO₄∶2% Sm³⁺有优异的热稳定性,热猝灭活化能为-0.157 eV,且具有良好的顺磁性,质量磁化率值为1.22×10^-4 emu·g^-1·Oe^-1。     

Evaluation of the stability of shortcut nitrification-denitrification process based on online specific oxygen uptake rate monitoring

Shortcut nitrification-denitrification (SCND) is widely concerned because of its low energy consumption and high nitrogen removal efficiency. However, the current difficulty lies in the stable maintenance of SCND performance, which leads to the challenge of large-scale application of this new denitrification technology. In this study, the nitrogen removal pathway from complete nitrification-denitrification (CND) to SCND was rapidly realized under high free ammonia (FA), high pH and low dissolved oxygen (DO) conditions. The variations of specific oxygen uptake rate (SOUR) of activated sludge in both processes were investigated by an online SOUR monitoring device. Different curves of SOUR from CND to SCND process were observed, and the ammonia peak obtained based on SOUR monitoring could be used to control aeration time accurately in SCND process. Accordingly, the SOUR ratio of ammonia oxidizing bacteria (AOB) to nitrite oxidizing bacteria (NOB) (SOUR_AOB/SOUR_NOB) was increased from 1.40 to 2.93. 16S rRNA Miseq high throughput sequencing revealed the dynamics of AOB and NOB, and the ratio of relative abundance (AOB/NOB) was increased from 1.03 to 3.12. Besides, SOUR_AOB/SOUR_NOB displayed significant correlations to ammonia removal rate (P<0.05), ammonia oxidation rate / nitrite oxidation rate (P < 0.05), nitrite accumulation rate (P < 0.05) and the relative abundance of AOB/NOB (P < 0.05). Thus, a strategy for evaluation the SCND process stability based on online SOUR monitoring is proposed, which provides a theoretical basis for optimizing the SCND performance.     

《茶经》中的中学化学课程资源

唐代陆羽撰写的《茶经》被誉为“茶叶百科全书”,是中国乃至世界上最早关于茶文化的史料,也是保留最完整、最全面的茶学专著。通过探析《茶经》中蕴含的育人价值,挖掘《茶经》中的化学课程资源。在化学教学中,将《茶经》中与化学知识契合的传统文化内容作为情境载体建立学习桥梁,从化学角度对传统文化内容进行再认识,从文化视角感受化学中蕴含的人文底蕴,帮助学习和理解化学知识,增强文化认同感和民族自豪感。依据新课标中的情境素材建议与要求,梳理了《茶经》中可与高中化学教科书相联系的内容,为创设真实的情境提供素材,利用古代茶器具与中学化学实验仪器之间的相似性创设情境。并且提出了关于中学化学教学中有效融入传统文化的几点建议。     

Ambient Preparation of Benzoxazine-based Phenolic Resins Enables Long-term Sustainable Photosynthesis of Hydrogen Peroxide

Rational design of polymer structures at the molecular level promotes the iteration of high-performance photocatalyst for sustainable photocatalytic hydrogen peroxide (H₂O₂) production from oxygen and water, which also lays the basis for revealing the reaction mechanism. Here we report a benzoxazine-based m-aminophenol-formaldehyde resin (APFac) polymerized at ambient conditions, exhibiting superior H₂O₂ yield and long-term stability to most polymeric photocatalysts. Benzoxazine structure was identified as the crucial photocatalytic active segment in APFac. Favorable adsorption of oxygen/intermediates on benzoxazine structure and commendable product selectivity accelerated the reaction kinetically in stepwise single-electron oxygen reduction reaction. The proposed benzoxazine-based phenolic resin provides the possibility of production in batches and industrial application, and sheds light on the de novo design and analysis of metal-free polymeric photocatalysts.     

Design of Hollow Nanoreactors for Size- and Shape-Selective Catalytic Semihydrogenation Driven by Molecular Recognition

Mimicking the structures and functions of cells to create artificial organelles has spurred the development of efficient strategies for production of hollow nanoreactors with biomimetic catalytic functions. However, such structure are challenging to fabricate and are thus rarely reported. We report the design of hollow nanoreactors with hollow multishelled structure (HoMS) and spatially loaded metal nanoparticles. Starting from a molecular-level design strategy, well-defined hollow multishelled structure phenolic resins (HoMS-PR) and carbon (HoMS-C) submicron particles were accurately constructed. HoMS-C serves as an excellent, versatile platform, owing to its tunable properties with tailored functional sites for achieving precise spatial location of metal nanoparticles, internally encapsulated (Pd@HoMS-C) or externally supported (Pd/HoMS-C). Impressively, the combination of the delicate nanoarchitecture and spatially loaded metal nanoparticles endow the pair of nanoreactors with size–shape-selective molecular recognition properties in catalytic semihydrogenation, including high activity and selectivity of Pd@HoMS-C for small aliphatic substrates and Pd/HoMS-C for large aromatic substrates. Theoretical calculations provide insight into the pair of nanoreactors with distinct behaviors due to the differences in energy barrier of substrate adsorption. This work provides guidance on the rational design and accurate construction of hollow nanoreactors with precisely located active sites and a finely modulated microenvironment by mimicking the functions of cells.     

An Unlocked Two-Dimensional Conductive Zn-MOF on Polymeric Carbon Nitride for Photocatalytic H2O2 Production

Developing highly efficient catalytic sites for O₂ reduction to H₂O₂, while ensuring the fast injection of energetic electrons into these sites, is crucial for artificial H₂O₂ photosynthesis but remains challenging. Herein, we report a strongly coupled hybrid photocatalyst comprising polymeric carbon nitride (CN) and a two-dimensional conductive Zn-containing metal–organic framework (Zn-MOF) (denoted as CN/Zn-MOF(lc)/400; lc, low crystallinity; 400, annealing temperature in °C), in which the catalytic capability of Zn-MOF(lc) for H₂O₂ production is unlocked by the annealing-induced effects. As revealed by experimental and theoretical calculation results, the Zn sites coordinated to four O (Zn-O₄) in Zn-MOF(lc) are thermally activated to a relatively electron-rich state due to the annealing-induced local structure shrinkage, which favors the formation of a key *OOH intermediate of 2e⁻ O₂ reduction on these sites. Moreover, the annealing treatment facilitates the photoelectron migration from the CN photocatalyst to the Zn-MOF(lc) catalytic unit. As a result, the optimized catalyst exhibits dramatically enhanced H₂O₂ production activity and excellent stability under visible light irradiation.     

Dual-Atom Catalysts Derived from a Preorganized Covalent Organic Framework for Enhanced Electrochemical Oxygen Reduction

Dual-atom catalysts (DAC) are deemed as promising electrocatalysts due to the abundant active sites and adjustable electronic structure, but the fabrication of well-defined DAC is still full of challenges. Herein, bonded Fe dual-atom catalysts (Fe₂DAC) with Fe₂N₆C₈O₂ configuration were developed through one-step carbonization of a preorganized covalent organic framework with bimetallic Fe chelation sites (Fe₂COF). The transition from Fe₂COF to Fe₂DAC involved the dissociation of the nanoparticles and the capture of atoms by carbon defects. Benefitting from the optimized d-band center and enhanced adsorption of OOH* intermediates, Fe₂DAC exhibited outstanding oxygen reduction activity with a half-wave potential of 0.898 V vs. RHE. This work will guide more fabrication of dual-atom and even cluster catalysts from preorganized COF in the future.     

Frenkel Defect-modulated Anti-thermal Quenching Luminescence in Lanthanide-doped Sc2(WO4)3

Although large amount of effort has been invested in combating thermal quenching that severely degrades the performance of luminescent materials particularly at high temperatures, not much affirmative progress has been realized. Herein, we demonstrate that the Frenkel defect formed via controlled annealing of Sc₂(WO₄)₃:Ln (Ln=Yb, Er, Eu, Tb, Sm), can work as energy reservoir and back-transfer the stored excitation energy to Ln³⁺ upon heating. Therefore, except routine anti-thermal quenching, thermally enhanced 415-fold downshifting and 405-fold upconversion luminescence are even obtained in Sc₂(WO₄)₃:Yb/Er, which has set a record of both the Yb³⁺-Er³⁺ energy transfer efficiency (>85 %) and the working temperature at 500 and 1073 K, respectively. Moreover, this design strategy is extendable to other hosts possessing Frenkel defect, and modulation of which directly determines whether enhanced or decreased luminescence can be obtained. This discovery has paved new avenues to reliable generation of high-temperature luminescence.     

Zincophilic Interfacial Manipulation against Dendrite Growth and Side Reactions for Stable Zn Metal Anodes

Constructing multifunctional interphases to suppress the rampant Zn dendrite growth and detrimental side reactions is crucial for Zn anodes. Herein, a phytic acid (PA)-ZnAl coordination compound is demonstrated as a versatile interphase layer to stabilize Zn anodes. The zincophilic PA-ZnAl layer can manipulate Zn²⁺ flux and promote rapid desolvation kinetics, ensuring the uniform Zn deposition with dendrite-free morphology. Moreover, the robust PA-ZnAl protective layer can effectively inhibit the hydrogen evolution reaction and formation of byproducts, further contributing to the reversible Zn plating/stripping with high Coulombic efficiency. As a result, the Zn@PA-ZnAl electrode shows a lower Zn nucleation overpotential and higher Zn²⁺ transference number compared with bare Zn. The Zn@PA-ZnAl symmetric cell exhibits a prolonged lifespan of 650 h tested at 5 mA cm⁻² and 5 mAh cm⁻². Furthermore, the assembled Zn battery full cell based on this Zn@PA-ZnAl anode also delivers decent cycling stability even under harsh conditions.     

Thermal behaviors and kinetic analysis of two natural kaolinite samples selected from Qingshuihe region in Inner Mongolia in China

Journal of Thermal Analysis and Calorimetry - The thermal characteristic behaviors of two kaolinite samples selected from Qingshuihe region in Inner Mongolia in China were studied through...