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N-Heterocyclic carbene-stabilized platinum nanoparticles within a porphyrinic nanocage for selective photooxidation

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Science China Chemistry 2023年第3期66卷 778-782页

作者： Yi-Shou Wang Hao Li Sha Bai Yao-Yu Wang Ying-Feng Han Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education Xi’an Key Laboratory of Functional Supramolecular Structure and MaterialsCollege of Chemistry and Materials ScienceNorthwest UniversityXi’an 710127China

The successful construction of highly stable and active platinum nanoparticles(Pt NPs) within the confined cavity of a threedimensional porphyrinic nanocage is presented in this study. The flexible porphyrinic nanocage containing eight N-heterocyclic carbene(NHC) precursors was prepared using a metal-carbene-templated ring-closing metathesis(RCM) approach as new capping materials for the fabrication/stabilization of Pt NPs. Notably, the NHC-stabilized Pt NPs within the porphyrinic nanocage exhibited high catalytic activity for selective oxidation of 2-chloroethyl ethyl sulfide to nontoxic 2-chloroethyl ethyl sulfoxide with excellent stability and recyclability.

关键词： polycarbenes porphyrinic cage nanoparticles photocatalysis

Estimation of the radiation backgrounds in the CEPC vertex detector

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Radiation Detection Technology and Methods 2022年第2期6卷 170-178页

作者： Wei Xu Haoyu Shi Hongbo Zhu Ke Li Sha Bai Xinchou Lou Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China School of Physics Zhejiang UniversityHangzhou 310058China Department of Physics University of WashingtonSeattleWA 98195USA

Background The Circular Electron-Positron Collider(CEPC)is aimed for precision measurements of the Higgs boson properties and the electroweak parameters.The achievable precision will be largely dependent on the controlled level of radiation backgrounds,which requires an optimized design of the interaction region to assure the optimal performance of both the accelerator and the detectors.Purpose In this article,the latest results on the radiation backgrounds are reported based on the accelerator parameters and the detector design presented in the CEPC conceptual design reports.Method For the different sources of radiation backgrounds,simulation steps consisting of generation,tracking,and detector simulation were performed.Radiation backgrounds from the processes of synchrotron radiation,pair production,radiative Bhabha scattering,beam gas Bremsstrahlung scattering,and beam thermal photon scattering were considered for the accel-erator operating at the different centre-of-mass energies(HZ threshold,WW threshold,and Z pole).Possible mitigation methods of masks and/or collimators were introduced to suppress the radiation backgrounds,together with the careful opti-mization of the interaction region design.With the improved tracking methods during simulation,the accuracy and reliability of the results were improved.In addition,the radiation backgrounds on the CEPC vertex detector were estimated,and the pair-production was found to be the most important source.Result In the worst case of operation at the Z pole,the vertex detector would have to withstand a total ionization dose of 5.6 Mrad per year and a non-ionization energy loss(shown in 1 MeV neutron equivalent)of 1.06×10^(13)n_(eq)/cm^(2)per year.

关键词： CEPC Interaction region Beam-induced background Vertex detector

Supramolecular Template-Assisted Catalytic[2+2]Photocycloaddition in Homogeneous Solution

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CCS Chemistry 2023年第3期5卷 633-640页

作者： Fang Wang Sha Bai Qing-Wen Zhu Zi-Hang Wei Ying-Feng Han Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education Xi’an Key Laboratory of Functional Supramolecular Structure and MaterialsCollege of Chemistry and Materials ScienceNorthwest UniversityXi’an 710127

Supramolecular interactions can help recognize and organize substrates around an enzyme’s active sites and subsequently assemble a new molecule in a certain way.Inspired by nature’s control of reactions,in this work we designed a template catalyst equipped with ditopic Au(I)–N-heterocyclic carbene(NHC)functional sites that direct olefin substrates into reactive geometries via collaboration of coordination-driven interactions.Notably,this catalyst enables the realization of catalytic[2+2]photocycloadditions with as low as 2 mol%catalyst loading in homogeneous solution and the delivery of a series of cyclobutane derivatives with excellent conversions and stereoselectivities.The success of gram-scale reactions further demonstrates the feasibility of this strategy,which lays a solid foundation for the large-scale preparation of cyclobutane derivatives in the future.

关键词： N-heterocyclic carbene supramolecular catalysis template synthesis photocycloaddition self-assembly

Template Synthesis of Metal Nanoparticles within Organic Cages

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Chinese Journal of Chemistry 2019年第12期37卷 1289-1290页

作者： Sha Bai Yao-Yu Wang Ying-Feng Han Key Laboratory of Synthetic and Natural Functional Molecule Chemistry College of Chemistry and Materials ScienceNorthwest UniversityXi'anShaanxi 710127China

Background Metal nanoparticles(M-NPs)have attracted tremendous interest in recent years due to their unique physical and chemical properties resulting from their size reduction and shape variation.[1]In particular,the use of ultra-small M-NPs as efficient catalysts in various reactions is a rapidly growing area of research as a consequence of their synthetic accessibility and superior catalytic efficiency.[2]However,due to their high surface energy,small M-NPs are prone to aggregation during reactions and associated loss of their catalytic activities.To deal with this difficulty,various stabilizers and/or supports have been developed,for instance,small organic ligands,dendritic architectures,and polymers.Unfortunately,these materials all have limitations,such as low stability,constant leaching,irregular distribution or regrowth and combinations of these.Therefore,it is highly desirable to develop superior support materials that can overcome these issues.

关键词： overcome instance consequence

Developing a process-based and remote sensing driven crop yield model for maize(PRYM–Maize) and its validation over the Northeast China Plain

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Journal of Integrative Agriculture 2021年第2期20卷 408-423页

作者： ZHANG sha bai Yun ZHANG Jia-hua shahzad ALI School of Automation Qingdao UniversityQingdao 266071P.R.China College of Computer Science and Technology Qingdao UniversityQingdao 266071P.R.China Aerospace Information Research Institute Chinese Academy of SciencesBeijing 100094P.R.China University of Chinese Academy of Sciences Beijing 100049P.R.China

Spatial dynamics of crop yield provide useful information for improving the production. High sensitivity of crop growth models to uncertainties in input factors and parameters and relatively coarse parameterizations in conventional remote sensing(RS) approaches limited their applications over broad regions. In this study, a process-based and remote sensing driven crop yield model for maize(PRYM–Maize) was developed to estimate regional maize yield, and it was implemented using eight data-model coupling strategies(DMCSs) over the Northeast China Plain(NECP). Simulations under eight DMCSs were validated against the prefecture-level statistics(2010–2012) reported by National Bureau of Statistics of China, and inter-compared. The 3-year averaged result could give more robust estimate than the yearly simulation for maize yield over space. A 3-year averaged validation showed that prefecture-level estimates by PRYM–Maize under DMCS8, which coupled with the development stage(DVS)-based grain-filling algorithm and RS phenology information and leaf area index(LAI), had higher correlation(R, 0.61) and smaller root mean standard error(RMSE, 1.33 t ha^(–1)) with the statistics than did PRYM–Maize under other DMCSs. The result also demonstrated that DVS-based grain-filling algorithm worked better for maize yield than did the harvest index(HI)-based method, and both RS phenology information and LAI worked for improving regional maize yield estimate. These results demonstrate that the developed PRYM–Maize under DMCS8 gives reasonable estimates for maize yield and provides scientific basis facilitating the understanding the spatial variations of maize yield over the NECP.

关键词： process-based and remote sensing model maize yield simulation development stage grain filling harvest index

Scaled-up synthesis of defect-rich layered double hydroxide monolayers without organic species for efficient oxygen evolution reaction

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Green Energy & Environment 2022年第5期7卷 975-982页

作者： Haoyuan Chi Jingwen Dong Tian Li Sha Bai Ling Tan Jikang Wang Tianyang Shen Guihao Liu Lihong Liu Luyi Sun Yufei Zhao Yu-Fei Song State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical TechnologyBeijing100029China College of Chemistry Key Laboratory of Theoretical&Computational Photochemistry of Ministry of EducationBeijing Normal UniversityBeijing100875China Polymer Program Institute of Materials Science and Department of Chemical&Biomolecular EngineeringUniversity of ConnecticutStorrsConnecticut06269USA Beijing Advanced Innovation Center for Soft Matter Science and Engineering Beijing University of Chemical TechnologyBeijing100029China

The scaled-up synthesis of organic-free monolayer nanomaterials is highly desirable,especially in obtaining green energy by electrocatalysis.In this study,a method for the scaled-up synthesis of the series of monolayer layered double hydroxides(LDHs)without the addition of organic solvents is reported via the separate nucleation and aging steps process.The resulting monolayer LDHs with the thicknesses of less than 1 nm showed a narrow thickness distribution.X-ray absorption fine-structure revealed that monolayer NiFe-LDH nanosheets have a number of oxygen and metal vacancies defects.As a practical application,monolayer NiFe-LDH nanosheets containing defects showed an enhanced electrocatalytic water oxidation activity compared with that of bulk NiFe-LDH.Density functional theory calculations uncovered that excellent catalytic activity is attributed to vacancies defects.The proposed method is an economical and universally applicable strategy for the scaled-up production of monolayer LDHs.

关键词： process synthesis monolayer

Using a skillful statistical model to predict September sea ice covering Arctic shipping routes

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Acta Oceanologica Sinica 2020年第5期39卷 11-25页

作者： sha Li Muyin Wang Wenyu Huang Shiming Xu Bin Wang Yuqi bai Ministry of Education Key Laboratory for Earth System Modeling Department of Earth System ScienceTsinghua UniversityBeijing 100084China Joint Institute for the Study of the Atmosphere and Ocean University of WashingtonSeattle WA98195USA Pacific Marine Environmental Laboratory National Oceanic and Atmospheric AdministrationSeattle WA98115USA State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China

The rapid decrease in Arctic sea ice cover and thickness not only has a linkage with extreme weather in the midlatitudes but also brings more opportunities for Arctic shipping routes and polar resource exploration,both of which motivate us to further understand causes of sea-ice variations and to obtain more accurate estimates of seaice cover in the future.Here,a novel data-driven method,the causal effect networks algorithm,is applied to identify the direct precursors of September sea-ice extent covering the Northern Sea Route and Transpolar Sea Route at different lead times so that statistical models can be constructed for sea-ice prediction.The whole study area was also divided into two parts:the northern region covered by multiyear ice and the southern region covered by seasonal ice.The forecast models of September sea-ice extent in the whole study area(TSIE)and southern region(SSIE)at lead times of 1–4 months can explain over 65%and 79%of the variances,respectively,but the forecast skill of sea-ice extent in the northern region(NSIE)is limited at a lead time of 1 month.At lead times of 1–4 months,local sea-ice concentration and sea-ice thickness have a larger influence on September TSIE and SSIE than other teleconnection factors.When the lead time is more than 4 months,the surface meridional wind anomaly from northern Europe in the preceding autumn or early winter is dominant for September TSIE variations but is comparable to thermodynamic factors for NSIE and SSIE.We suggest that this study provides a complementary approach for predicting regional sea ice and is helpful in evaluating and improving climate models.

关键词： regional sea ice Arctic shipping routes machine learning statistical model predictions

Multistimuli-Responsive Fluorescent Organometallic Assemblies Based on Mesoionic Carbene-Decorated Tetraphenylethene Ligands and Their Applications in Cell Imaging

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CCS Chemistry 2022年第2期4卷 732-743页

作者： Yang Li Tianfeng Yang Nan Li Sha Bai Xin Li Li-Li Ma Kai Wang Yanmin Zhang Ying-Feng Han Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education College of Chemistry and Materials ScienceNorthwest UniversityXi’an 710127 School of Pharmacy Health Science CenterXi’an Jiaotong UniversityXi’an 710061 State Key Laboratory of Superhard Materials College of PhysicsJilin UniversityChangchun 130012

The controllable construction of light-emitting organometallic supramolecular materials integrating stimulus responses and biological applications is still a major challenge today.In this work,emissive organometallic assemblies based on AgI/AuI and mesoionic carbene-decorated tetraphenylethene(MIC-TPE)ligands have been synthesized and characterized.Photophysical studies showed that these organometallic assemblies[M_(4)(2)_(2)](OTf)_(4) not only fluoresce in various dilute solutions,resulting from the rigidification of MIC-TPE ligands upon complexation,but also show tunable fluorescence wavelengths and intensity behaviors in mixed solvent systems and at varying temperatures while in solution,and mechanical pressure stimulus-responsive fluorescent features in the solid state.Furthermore,the organometallic cages[M_(4)(2)_(2)](OTf)_(4)(M=Ag and Au)were successfully employed for cell imaging and showed the potential of anticancer activity,making them promising candidates for cancer theranostics.This work provides a simple and efficient method to prepare highly emissive and stimulus-responsive organometallic materials and paves the way for related biological applications such as cancer cell imaging and targeted therapy.

关键词： light-emitting materials mesoionic carbene organometallic chemistry mechanochromic properties cell imaging

Spatio-temporal patterns of satellite-derived grassland vegetation phenology from 1998 to 2012 in Inner Mongolia, China

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Journal of Arid Land 2016年第3期8卷 462-477页

作者： sha Zongyao ZHONG Jialin bai Yongfei TAN Xicheng Jonathan LI International Software School Wuhan University Department of Geography & Environmental Management University of Waterloo Institute of Botany Chinese Academy of Sciences

Spatio-temporal variations of vegetation phenology, e.g. start of green-up season（SOS） and end of vegetation season（EOS）, serve as important indicators of ecosystems. Routinely processed products from remotely sensed imagery, such as the normalized difference vegetation index（NDVI）, can be used to map such variations. A remote sensing approach to tracing vegetation phenology was demonstrated here in application to the Inner Mongolia grassland, China. SOS and EOS mapping at regional and vegetation type（meadow steppe, typical steppe, desert steppe and steppe desert） levels using SPOT-VGT NDVI series allows new insights into the grassland ecosystem. The spatial and temporal variability of SOS and EOS during 1998–2012 was highlighted and presented, as were SOS and EOS responses to the monthly climatic fluctuations. Results indicated that SOS and EOS did not exhibit consistent shifts at either regional or vegetation type level; the one exception was the steppe desert, the least productive vegetation cover, which exhibited a progressive earlier SOS and later EOS. Monthly average temperature and precipitation in preseason（February, March and April） imposed most remarkable and negative effects on SOS（except for the non-significant impact of precipitation on that of the meadow steppe）, while the climate impact on EOS was found to vary considerably between the vegetation types. Results showed that the spatio-temporal variability of the vegetation phenology of the meadow steppe, typical steppe and desert steppe could be reflected by the monthly thermal and hydrological factors but the progressive earlier SOS and later EOS of the highly degraded steppe desert might be accounted for by non-climate factors only, suggesting that the vegetation growing period in the highly degraded areas of the grassland could be extended possibly by human interventions.

关键词： phenological timing degradation harmonic analysis human activity climate restoration