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Thickness-dependent phase transition and optical behavior of MoS2 films under high pressure

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Nano Research 2018年第2期11卷 855-863页

作者： Xuerui Cheng Yuanyuan Li Jimin Shang Chuansheng Hu Yufen Ren Miao Liu zeming qi School of Physics and Electronic Engineering Zhengzhou University of Light Industry Zhengzhou China National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei China Energy Technologies Area Lawrence Berkeley National Laboratory Berkeley USA

We report the Raman and photoluminescence spectroscopic analysis of layered MoS2 under hydrostatic pressure up to 30 GPa. Unlike previous studies, throughout this work, a special treatment is applied to submerge monolayer, bilayer, multilayer （-200 layers）, and bulk MoS2 samples directly into silicone oil without a supporting substrate in a diamond anvil cell, thereby eliminating possible interference from substrate-film contact. A thickness-dependent trend is observed for the 2Hc-to-2Ha phase transition： The transition pressure increases from 19.0 to 25.6 GPa as the system thickness is reduced from bulk to multilayer MoS2; a further decrease in thickness to the bilayer structure increases the transition pressure to - 36 GPa, as predicted theoretically. This exceeds our measured pressure range, indicating the weakening of interlayer repulsive interactions as the MoS2 film thickness is reduced. Our experiment also reveals a monotonic trend of Raman peak shifting vs. film thickness under applied pressure, suggesting that the Raman vibration modes are more responsive to external pressure in thinner films. The photoluminescence emission peak of the monolayer MoS2 exhibits a blue shift under applied pressure at the rate of 23.8 ***-1. These results show that the structural and optical properties of MoS2 can be effectively modified by applying hydrostatic pressure.

关键词： molybdenum disulfide high pressure Raman spectroscopy photoluminescence diamond anvil cell

Ammonium Impacts on Vibrations of Hydroxyl and Lattice of Phengite at High Temperature and High Pressure

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Journal of Earth Science 2021年第5期32卷 1278-1286页

作者： Weihua Huang Yan Yang zeming qi Wendi Liu Zhongping Wang Yan Liu Qunke Xia School of Earth Sciences Zhejiang UniversityHangzhou 310027China National Synchrotron Radiation Laboratory University of Science and Technology of ChinaHefei 230026China Department of Physics University of Science and Technology of ChinaHefei 230026China

Dehydration in hydrous phases of the downgoing slab controls water release processes in subduction zones. Interplay between volatiles in hydrous minerals has complicated the previous knowledge of their dehydration. Phengite is an essential mineral carrying both hydrogen and nitrogen to the deep Earth. To further understand the link between nitrogen and dehydration process of phengite at an atomic level, we here carry out high temperature and high pressure vibrational spectroscopic investigations on hydroxyl and lattice of ammonium-bearing and ammonium-free phengites. The results show that heating to 800 oC hardly influences hydroxyl bonding strength, whereas pressure induces strengthening of hydrogen bonding until 10 GPa. Moreover, hydrogen transits between the sites with increasing temperature and pressure. The lattice modes soften with increasing temperature and stiffen under compression. Ammonium has no effect on hydroxyl bonding strength, but hinders hydrogen transition at high temperatures and high pressures. Ammonium does not influence the lattice at high pressures either, but delays softening of the lattice at high temperatures. These data unveil behavior of hydroxyl and lattice in phengite at high temperature and high pressure, and also evaluate ammonium impacts, shedding new lights on dehydration processes of phengite during subduction.

关键词： hydroxyl lattice ammonium phengite high temperature high pressure

Sulfur-vacancy-tunable interlayer magnetic coupling in centimeter-scale M0S2 bilayer

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Nano Research 2022年第2期15卷 881-888页

作者： Hengli Duan Guinan Li Hao Tan Chao Wang qian Li Chuanchuan Liu Yuewei Yin Xiaoguang Li zeming qi Wensheng Yan National Synchrotron Radiation Laboratory University of Science and Technology of ChinaHefei 230029China Hefei National Laboratory for Physical Sciences at the Microscale Department of Physicsand CAS Key Laboratory of Strongly-coupled Quantum Matter PhysicsUniversity of Science and Technology of ChinaHefei 230026China

Endowing bilayer transition-metal dichalcogenides(TMDs)with tunable magnetism is significant to investigate the coupling of multiple electron degrees of freedom(DOFs).However,effectively inducing and tuning the magnetic interaction of bilayer TMDs are still ***,we report a strategy to tune the interlayer exchange interaction of centimeter-scale MoS2 bilayer with substitutional doping of Co ion,by introducing sulfur vacancy(V_(s))to modulate the interlayer electronic *** strategy could transform the interlayer exchange interaction from antiferromagnetism(AFM)to ferromagnetism(FM),as revealed by the magnetic *** characterizations and theoretical calculations indicate that the enhanced magnetization is mainly because the hybridization of Co 3d band and Vs-induced impurity band alters the forms of interlayer orbital hybridizations between the partial Co atoms in upper and lower layers,and also enhances the intralayer *** work paves the way for tuning the interlayer exchange interaction with defects and could be extended to other two-dimensional(2D)magnetic materials.

关键词： interlayer exchange interaction 2D magnetic materials S-vacancy interlayer coupling large-area growth

A Unique Ru-N_(4)-P Coordinated Structure Synergistically Waking Up the Nonmetal P Active Site for Hydrogen Production

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Research 2020年第1期2020卷 944-955页

作者： Chuanqiang Wu Shiqing Ding Daobin Liu Dongdong Li Shuangming Chen Huijuan Wang zeming qi Binghui Ge Li Song National Synchrotron Radiation Laboratory CAS Center for Excellence in NanoscienceUniversity of Science and Technology of ChinaHefeiAnhui 230029China Institutes of Physical Science and Information Technology Anhui UniversityHefei 230601China Institute of Amorphous Matter Science School of Materials Science and EngineeringHefei University of TechnologyHefeiAnhui 230009China Experimental Center of Engineering and Material Science University of Science and Technology of ChinaHefei 230026China

Numerous experiments have demonstrated that the metal atom is the active center of monoatomic catalysts for hydrogen evolution reaction(HER),while the active sites of nonmetal doped atoms are often *** combining theoretical prediction and experimental verification,we designed a unique ternary Ru-N_(4)-P coordination structure constructed by monodispersed Ru atoms supported on N,P dual-doped graphene for highly efficient hydrogen evolution in acid *** density functional theory calculations indicate that the charge polarization will lead to the most charge accumulation at P atoms,which results in a distinct nonmetallic P active sites with the moderate H∗adsorption ***,these P atoms mainly supply highly efficient catalytic sites with ultrasmall absorption energy of 0.007 ***,the Ru-N_(4)-P demonstrated outstanding HER performance not only in an acidic condition but also in alkaline ***,the performance of Ru-NPC catalyst at high current is even superior to the commercial Pt/C catalysts,whether in acidic or alkaline *** in situ synchrotron radiation infrared spectra demonstrate that a P-H_(ads) intermediate is continually emerging on the Ru-NPC catalyst,actively proving the nonmetallic P catalytically active site in HER that is very different with previously reported metallic sites.

关键词： solution alkaline catalyst

Single atom accelerates ammonia photosynthesis

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Science China Chemistry 2018年第9期61卷 1187-1196页

作者： Pengcheng Huang Wei Liu Zhihai He Chong Xiao Tao Yao Youming Zou Chengming Wang zeming qi Wei Tong Bicai Pan Shiqiang Wei Yi Xie Hefet National Laboratory for Physical Sciences at the Microscale CAS Center for Excellence in Nanoscience iCHEM University of Science and Technology of China Hefei 230026 China National Synchrotron Radiation Laboratory University of Science and Technology of China. Hefei 230029 China High Magnetic Field Laboratory Chinese Academy of Sciences Hefei 230031 China

Atomically dispersed metal has gained much attention because of the new opportunities they offer in catalysis. However, it is still crucial to understand the mechanism of single-atom catalysis at molecular level for expanding them to other more difficult catalytic reactions, such as ammonia synthesis from nitrogen. In fact, developing ammonia synthesis under ambient conditions to overcome the high energy consumption in well-established Haber-Bosch process has fascinated scientists for many ***, we demonstrate that single Cu atom yields facile valence-electron isolation from the conjugated π electron cloud of p-CN. Electron spin resonance measurements reveal that these isolated valence electrons can be easily excited to generate free electrons under photo-illumination, thus inducing high efficient photo-induced ammonia synthesis under ambient *** NH_3 producing rate of copper modified carbon nitride(Cu-CN) reached 186 μmol g^(-1) h^(-1) under visible light irradiation with the quantum efficiency achieved 1.01% at 420 nm monochromatic light. This finding surely offers a model to open up a new vista for the ammonia synthesis at gentle conditions. The introduction of single atom to isolate the valence electron also represents a new paradigm for many other photocatalytic reactions, since the most photoinduced processes have been successfully exploited sharing the same origin.

关键词： single atom photocatalytic ammonia synthesis

Quantitative research on higher order harmonics in metrology beamline

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Frontiers of Electrical and Electronic Engineering in China 2008年第1期3卷 105-109页

作者： Hongjun ZHOU Jinjin ZHENG Tonglin HUO Guobin ZHANG zeming qi Pengfei ZHONG National Synchrotron Radiation Laboratory University of Science and Technology of ChinaHefei 230029China Department of Precision Machinery and Precision Instrumentation University of Science and Technology of ChinaHefei 230026China

The synchrotron radiation spectra of the spherical grating monochromator(SGM)working in the soft X-ray and VUV region are often contaminated by significant amounts of higher order *** cannot be suppressed completely by suitable *** order contributions in the spectral radiation standard and metrology beamline were researched using transmission grating(made in-house)and IRD AXUV100G(USA)photodiode *** exit beam was dispersed with the transmission grating behind the exit slit of the monochromator,and the contributions of the different orders were *** higher order distributions were quantitatively determined for three gratings with line densities of 1800,600 and 200 l/*** results show that in wavelengths between 5 nm and 15 nm the contributions of the higher orders to the detector signal are restricted to less than 7%even without the use of *** wavelength regions between 5 nm and 34 nm,the contributions of the higher orders to the detector signal are less than 14%with proper Al,Si_(3)N_(4) and Zr filters,and after being modified by quantum efficiency of the detector,the higher order contributions are restricted to less than 6.5%.The study also shows that higher orders are almost totally suppressed by MgF_(2) filter when the wavelength ranges between 115–140 nm.

关键词： spectral radiation standard higher order harmonics spectral radiation metrology

Working-in-tandem mechanism of multi-dopants in enhancing electrocatalytic nitrogen reduction reaction performance of carbon- based materials

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Nano Research 2021年第9期14卷 3234-3239页

作者： Wenqing Zhang Keke Mao Jingxiang Low Hengjie Liu Yanan Bo Jun Ma qiaoxi Liu Yawen Jiang Jiuzhong Yang Yang Pan zeming qi Ran Long Li Song Yujie Xiong Hefei National Laboratory for Physical Sciences at the Microscale Collaborative Innovation Center of Chemistry for Energy Materials(iChEM)School of Chemistry and Materials Scienceand National Synchrotron Radiation LaboratoryUniversity of Science and Technology of ChinaHefei 230041China School of Energy and Environment Science Anhui University of TechnologyMaanshan 243032China Institute of Energy Hefei Comprehensive National Science CenterHefei 230031China

Developing carbon-based electrocatalysts with excellent N2 adsorption and activation capability holds the key to achieve highly efficient nitrogen reduction reaction(NRR)for reaching its practical ***,we report a highly active electrocatalyst--metal-free pyrrolic-N dominated N,S co-doped carbon(pyrr-NSC)for *** on theoretical and experimental results,it is confirmed that the N and S-dopants practice a working-in-tandem mechanism on pyrr-NSC,where the N-dopants are utilized to create electropositive C sites for enhancing N2 adsorption and the S-dopants are employed to induce electron backdonation for facilitating N2 *** synergistic effect of the pyrrolic-N and S-dopants can also suppress the irritating hydrogen evolution reaction,further boosting the NRR *** work gives an indication that the combination of two different dopants on electrocatalyst can enhance NRR performance by working in the two tandem steps-the adsorption and activation of N2 molecules,providing a new strategy for NRR electrocatalyst design.

关键词： N2 reduction reaction metal-free catalyst heteroatoms doping asymmetric charge distribution electrocatalysis

(CaO)_(20.68)(MgO)_(1.32)(SiO_2)_4S_2∶Eu^(2+),Dy^(3+)红光材料的制备与发光特性

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中国稀土学报 2007年第1期25卷 51-54页

作者：刘淼施朝淑戚泽明刘波中国科学技术大学物理系安徽合肥230026 中国科学技术大学国家同步辐射实验室安徽合肥230029

研究了峰值波长651nm的红色发光材料(CaO)20.68(MgO)1.32(SiO2)4S2∶Eu2+,Dy3+的制备及发光特性。通过XRD分析表明硫气氛中合成的材料为具有硫成分的硅酸盐相。红光发射带为硫元素进入晶格后在发光中心周围形成了类似长余辉材料CaS∶Eu2... 详细信息

研究了峰值波长651nm的红色发光材料(CaO)20.68(MgO)1.32(SiO2)4S2∶Eu2+,Dy3+的制备及发光特性。通过XRD分析表明硫气氛中合成的材料为具有硫成分的硅酸盐相。红光发射带为硫元素进入晶格后在发光中心周围形成了类似长余辉材料CaS∶Eu2+,Cl-的局域结构。这也使材料具有了硫化物长余辉材料的发射光谱特征和硅酸盐材料高化学稳定性和高亮度的优点。热释光测量揭示它可能是一种潜在的红色长余辉材料。

关键词：红光发射硅酸盐硫化物长余辉稀土

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孤立性心肌致密化不全的研究现状

临床心血管病杂志 2011年第8期27卷 563-565页

作者：祁泽明张晓燕彭宇竹金昌市第一人民医院心内科甘肃金昌737209 金昌市林业局林业技术推广服务中心南京市妇幼保健院

孤立性心肌致密化不全（isolated non-compaction cardiomyopathy,NCCM）是胚胎发育过程中心内膜以及心肌发育停止而引起的以心室内壁异常粗大交错的肌小梁和深隐窝为特征的基因异常相关性遗传性心肌病。1984年Engberding等〔1〕首次描... 详细信息

孤立性心肌致密化不全（isolated non-compaction cardiomyopathy,NCCM）是胚胎发育过程中心内膜以及心肌发育停止而引起的以心室内壁异常粗大交错的肌小梁和深隐窝为特征的基因异常相关性遗传性心肌病。1984年Engberding等〔1〕首次描述了该病的典型超声心动图表现,1995年WHO将其定义为未分类心肌病，最近美国心脏病协会（AHA）建议将其归为原发性遗传性心肌病。目前为止，临床医师对本病了解甚少，本文通过对NCCM流行病学、临床表现、病理生理学、诊断等方面研究现状作一综述，以提高临床医生对NCCM的认识及诊治水平。

关键词：心肌致密化不全心肌疾病