Good dielectric performance and broadband dielectric polarization in Ag,Nb co-doped TiO2

Due to the demand of miniaturization and integration for ceramic capacitors in electronic components market, TiO₂-based ceramics with colossal permittivity has become a research hotspot in recent years. In this work, we report that Ag⁺/Nb⁵⁺ co-doped (Ag_1/4Nb_3/4)_xTi_1−xO₂ (ANTOx) ceramics with colossal permittivity over a wide frequency and temperature range were successfully prepared by a traditional solid–state method. Notably, compositions of ANTO0.005 and ANTO0.01 respectively exhibit both low dielectric loss (0.040 and 0.050 at 1 kHz), high dielectric permittivity (9.2 × 10³ and 1.6 × 10⁴ at 1 kHz), and good thermal stability, which satisfy the requirements for the temperature range of application of X9R and X8R ceramic capacitors, respectively. The origin of the dielectric behavior was attributed to five dielectric relaxation phenomena, i.e., localized carriers' hopping, electron–pinned defect–dipoles, interfacial polarization, and oxygen vacancies ionization and diffusion, as suggested by dielectric temperature spectra and valence state analysis via XPS; wherein, electron-pinned defect–dipoles and internal barrier layer capacitance are believed to be the main causes for the giant dielectric permittivity in ANTOx ceramics.     

Eco-friendly and degradable red phosphorus nanoparticles for rapid microbial sterilization under visible light

Pathogens pose a serious challenge to environmental sanitation and a threat to public health.The frequent use of chemicals for sterilization in recent years has not only caused secondary damage to the environment but also increased pathogen resistance to drugs,which further threatens public health.To address this issue,the use of non-chemical antibacterial means has become a new trend for environmental disinfection.In this study,we developed red phosphorus nanoparticles(RPNPs),a safe and degradable photosensitive material with good photocatalytic and photothermal properties.The red phosphorus nanoparticles were prepared using a template method and ultrasonication.Under the irradiation of simulated sunlight for 20 min,the RPNPs exhibited an efficiency of 99.98%in killing Staphylococcus aureus due to their excellent photocatalytic and photothermal abilities.Transmission electron microscopy and ultraviolet–visible spectroscopy revealed that the RPNPs exhibited degradability within eight weeks.Both the RPNPs and their degradation products were nontoxic to fibroblast cells.Therefore,such RPNPs are expected to be used as a new type of low-cost,efficient,degradable,biocompatible,and eco-friendly photosensitive material for environmental disinfection.     

MOF衍生的高选择性加氢芳香硝基化合物的石墨碳包覆镍催化剂

针对芳香硝基化合物的催化选择性加氢反应，开发可替代贵金属催化剂的低成本、高效非贵金属催化剂，对于芳香胺类化合物的绿色生产具有重要意义。利用简易、可规模化的制备方法，以镍—2,5-吡啶二羧酸金属有机框架为前驱体，热解制备了氮掺杂石墨碳包覆镍纳米催化材料（Ni@CN）。采用X射线衍射、扫描电镜、透射电镜、元素分析、N2吸脱附等检测手段对Ni@CN的物化性质进行了表征，并对其催化性能进行了评价。结果表明，Ni@CN可在温和条件下（85℃，1.0 MPa H2)高效加氢含取代官能团的芳香硝基化合物生成对应的芳香胺类化合物。对比试验表明，镍纳米颗粒是Ni@CN的加氢活性中心，而石墨碳壳的存在有利于优先吸附硝基官能团。此外，进一步考察了Ni@CN的循环使用性能以及抗硫化物中毒的特性。     

Noncentrosymmetric Tetrel Pnictides RuSi4P4 and IrSi3P3: Nonlinear Optical Materials with Outstanding Laser Damage Threshold

Noncentrosymmetric (NCS) tetrel pnictides have recently generated interest as nonlinear optical (NLO) materials due to their second harmonic generation (SHG) activity and large laser damage threshold (LDT). Herein nonmetal-rich silicon phosphides RuSi₄P₄ and IrSi₃P₃ are synthesized and characterized. Their crystal structures are reinvestigated using single crystal X-ray diffraction and ²⁹Si and ³¹P magic angle spinning NMR. In agreement with previous report RuSi₄P₄ crystallizes in NCS space group P1, while IrSi₃P₃ is found to crystallize in NCS space group Cm, in contrast with the previously reported space group C2. A combination of DFT calculations and diffuse reflectance measurements reveals RuSi₄P₄ and IrSi₃P₃ to be wide bandgap (E_g) semiconductors, E_g = 1.9 and 1.8 eV, respectively. RuSi₄P₄ and IrSi₃P₃ outperform the current state-of-the-art infrared SHG material, AgGaS₂, both in SHG activity and laser inducer damage threshold. Due to the combination of high thermal stabilities (up to 1373 K), wide bandgaps (≈2 eV), NCS crystal structures, strong SHG responses, and large LDT values, RuSi₄P₄ and IrSi₃P₃ are promising candidates for longer wavelength NLO materials.     

Nanocellulose-based reusable liquid metal printed electronics fabricated by evaporation-induced transfer printing

Reusable electronics have received widespread attention and are urgently needed. Here, nanocellulosebased liquid metal(NC-LM) printed circuit has been fabricated by the evaporation-induced transfer printing technology. In this way, the liquid metal pattern is embedded into the nanocellulose membrane, which is beneficial for the stability of the circuit during use. Besides, the NC-LM circuit is ultrathin with just tens of microns. In particular, the finished product is environmentally friendly because it can be completely dissolved by water, and both the liquid metal ink and the nanocellulose membrane can be easily recollected and reused, thereby reducing waste and pollution to the environment. Several examples of flexible circuits have been designed to evaluate their performance. The mechanism of evaporation-induced transfer printing technology involves the deposition, aggregation, and coverage tightly of the nanosized cellulose fibrils as the water evaporated. This study provides an economical and environmentally friendly way for the fabrication of renewable flexible electronics.     

UV-enhanced conductive and dielectric properties in KTN crystal

We observe enhancements of both conductive and dielectric properties under UV illumination by using a ferroelectric absorber, potassium tantalate niobate (KTa_1-xNb_xO₃, KTN). The UV-generated electron-hole pairs weaken the intrinsic ferroelectric polarization while enhance the conductive property. The UV-induced heat effect causes the enhancement of the dielectric property. The results are further confirmed by the maximal rectification ratio which shows an opposite trend between the direct heating process and the UV illumination. Our results are useful for better understanding of ferroelectric properties under UV illumination and the development of new optoelectronic devices.     

Oxygen vacancy-induced short-range ordering as a sole mechanism for enhanced magnetism of spinel ZnFe2O4 prepared via a one-step treatment

Despite being difficult to identify, extremely dilute oxygen vacancies have been widely reported to play an important role in enhancing magnetism in ZnFe₂O₄. The mechanisms underlying this enhanced magnetism have not been well understood for a long time and remain controversial because the formation of oxygen vacancy-rich ZnFe₂O₄ can be accompanied by changes in the chemical/physical characteristics, especially the composition, particle size, surface morphology and cation distribution, which can significantly affect the magnetization. An open and important question is whether and to what extent the enhanced magnetization can be attributed only to oxygen vacancies. In this study, the relationship between the magnetization and oxygen vacancies in ZnFe₂O₄ was definitively determined by using a carefully designed “shake-and-heat” treatment to prepare vacancy-rich samples while keeping the other crystal/surface parameters constant. Compared to the nearly vacancy-free paramagnetism samples, the vacancy-rich samples exhibited a higher magnetization of approximately 5 emu/g at both 300 K and 2 K. The Fe³⁺-O^2--Fe³⁺ superexchange paths broken by oxygen vacancies then resulting in the Fe³⁺-Fe³⁺ ferromagnetism configuration. Meanwhile, the oxygen vacancy is highly diluted then the ferromagnetism configuration is confined in a single super-cell, favoring a short-range magnetic ordering at room temperature. The concentration of oxygen vacancies was calculated to be 0.68% by magnetization measurement. Our results may shed a light on how oxygen vacancies affect magnetism.     

水厂-管网协同控制提升管网供水水质的策略与实践

充分考虑管网输配过程中水质稳定性对水厂工艺条件、出厂水水质指标的要求,从水厂-管网协同控制的水质安全保障理念,通过优化水厂布局、改善管网水力条件、构建应对多水源和季节性高藻的强适应性净水体系、强化出厂水水质化学稳定性和生物稳定性控制、持续管网及老旧小区更新改造等工程技术措施,提高南水北调水源进京后管网水质的稳定性.根据2014-2019年全市252个管网监测点的水质监测数据,发现管网水浊度整体呈季节性周期变化趋势,且逐年降低;构建的管网水质评价模型进一步证明了管网水浊度一级监测点数量显著增加,2019年一级和二级监测点数量达到总数的94％,管网监测点的浊度指标得到显著改善,水厂-管网协同控制技术的实施切实保障了北京市供水水质的稳定达标.     

New optical ceramics: High-entropy sesquioxide X2O3 multi-wavelength emission phosphor transparent ceramics

Highly transparent X₂O₃ sesquioxide ceramics were obtained from a solid solution of five different oxides (Lu₂O₃, Y₂O₃, Yb₂O₃, Gd₂O₃, and Dy₂O₃), mixed in an equal molar ratio according to the principle of high-entropy. The fabricated (Lu, Y, Yb, Gd, Dy)₂O₃ ceramics achieved 99.97 % of the relative density and exhibited a high degree of optical transparency with the in-line transmittance of almost 80 % in the visible wavelength range. Emissions of Gd³⁺ (⁶P_J → ⁸S_7/2 at 312 nm), Dy³⁺ (⁴F_9/2 → ⁶H_15/2 at 492 nm and ⁴F_9/2 → ⁶H_13/2 at 572 nm), and Yb³⁺ (²F_5/2 → ²F_7/2 at 1031 nm) suggested a potential application of the high-entropy ceramics as multi-wavelength emission phosphor transparent ceramics. High-entropy ceramics also exhibited lower specific heat and thermal conductivity compared to single-element sesquioxide ceramics. This work demonstrated that highly transparent oxide ceramics, with complex chemical compositions and good optical properties, could be obtained using the high-entropy principle.