When a laser beam writes on a metallic film,it usually coarsens and deuniformizes grains because of Ostwald ripening,similar to the case of annealing.Here we show an anomalous refinement effect of metal grains:A metal...When a laser beam writes on a metallic film,it usually coarsens and deuniformizes grains because of Ostwald ripening,similar to the case of annealing.Here we show an anomalous refinement effect of metal grains:A metallic silver film with large grains melts and breaks into uniform,close-packed,and ultrafine(~10 nm)grains by laser direct writing with a nanoscale laser spot size and nanosecond pulse that causes localized heating and adaptive shock-cooling.This method exhibits high controllability in both grain size and uniformity,which lies in a linear relationship between the film thickness(h)and grain size(D),D∝h.The linear relationship is significantly different from the classical spinodal dewetting theory obeying a nonlinear relationship(D∝h5/3)in common laser heating.We also demonstrate the application of such a silver film with a grain size of~10.9 nm as a surface-enhanced Raman scattering chip,exhibiting superhigh spatial-uniformity and low detection limit down to 10-15 M.This anomalous refinement effect is general and can be extended to many other metallic films.展开更多
Two-dimensional multiferroics,which simultaneously possess ferroelectricity and magnetism in a single phase,are well-known to possess great potential applications in nanoscale memories and spintronics.On the basis of ...Two-dimensional multiferroics,which simultaneously possess ferroelectricity and magnetism in a single phase,are well-known to possess great potential applications in nanoscale memories and spintronics.On the basis of first-principles calculations,a CrNCl_(2) monolayer is reported as an intrinsic multiferroic.The CrNCl_(2) has an antiferromagnetic ground state,with a N´eel temperature of about 88 K,and it exhibits an in-plane spontaneous polarization of 200 pC/m.The magnetic moments of CrNCl_(2) mainly come from the dxy orbital of the Cr cation,but the plane of the dxy orbital is perpendicular to the direction of the ferroelectric polarization,which hardly suppresses the occurrence of ferroelectricity.Therefore,the multiferroic exits in the CrNCl_(2).In addition,like CrNCl_(2),the CrNBr_(2) is an intrinsic multiferroic with antiferromagneticferroelectric ground state while CrNI_(2) is an intrinsic multiferroic with ferromagnetic-ferroelectric ground state.These findings enrich the multiferroics in the two-dimensional system and enable a wide range of applications in nanoscale devices.展开更多
Two-dimensional(2 D) transition metal phosphides(TMPs) are predicted with many novel properties and various applications. As a member of TMPs family, molybdenum phosphide(MoP) exhibits many exotic physicochemical prop...Two-dimensional(2 D) transition metal phosphides(TMPs) are predicted with many novel properties and various applications. As a member of TMPs family, molybdenum phosphide(MoP) exhibits many exotic physicochemical properties. However, the synthesis of high-quality2 D MoP single crystals is not reported due to the lack of reliable fabrication method, which limits the exploration of 2 D MoP. Here, we report the growth of high-quality ultrathin MoP single crystals with thickness down to 10 nm on liquid metals via chemical vapor deposition(CVD). The smooth surface of liquid Ga is regarded as a suitable growth substrate for producing 2 D MoP single crystals. The Mo source diffuses toward the Ga surface due to the high surface energy to react with phosphorus source, thus to fabricate ultrathin MoP single crystals. Then, we study the second harmonic generation(SHG) of 2 D MoP for the first time due to its intrinsic noncentrosymmetric structure. Our study provides an new approach to synthesize and explore other 2 D TMPs for future applications.展开更多
Engineering biomaterials to meet specific biomedical applications raises high requirements of mechanical performances,and simultaneous strengthening and toughening of polymer are frequently necessary but very challeng...Engineering biomaterials to meet specific biomedical applications raises high requirements of mechanical performances,and simultaneous strengthening and toughening of polymer are frequently necessary but very challenging in many cases.In this work,we propose a new concept of nanoconcrete welding polymer chains,where mesoporous CaCO3(mCaCO_(3))nanoconcretes which are composed of amorphous and nanocrystalline phases are developed to powerfully weld polymer chains through siphoning-induced occlusion,hydration-driven crystallization and dehydration-driven compression of nanoconcretes.The mCaCO_(3) nanoconcrete welding technology is verified to be able to remarkably augment strength,toughness and anti-fatigue performances of a model polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-based porous membrane.Mechanistically,we have revealed polymer-occluded nanocrystal structure and welding-derived microstress which is much stronger than interfacial Van der Waals force,thus efficiently preventing the generation of microcracks and repairing initial microcracks by microcracks-induced hydration,crystallization and polymer welding of mCaCO_(3) nanoconcretes.Constructed porous membrane is used as wound dressing,exhibiting a special nanoplates-constructed surface topography as well as a porous structure with plentiful oriented,aligned and opened pore channels,improved hydrophilicity,water vapor permeability,anti-bacterial and cell adherence,in support of wound healing and skin structural/functional repairing.The proposed nanoconcrete-welding-polymer strategy breaks a new pathway for improving the mechanical performances of polymers.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51971070,T2225017,and 10974037)the National Key Research and Development Program of China(No.2016YFA0200403)+2 种基金the Natural Science Foundation of Shandong Province(No.ZR2021QF003)the CAS Strategy Pilot Program(No.XDA 09020300)the Eu-FP7 Project(No.247644).
文摘When a laser beam writes on a metallic film,it usually coarsens and deuniformizes grains because of Ostwald ripening,similar to the case of annealing.Here we show an anomalous refinement effect of metal grains:A metallic silver film with large grains melts and breaks into uniform,close-packed,and ultrafine(~10 nm)grains by laser direct writing with a nanoscale laser spot size and nanosecond pulse that causes localized heating and adaptive shock-cooling.This method exhibits high controllability in both grain size and uniformity,which lies in a linear relationship between the film thickness(h)and grain size(D),D∝h.The linear relationship is significantly different from the classical spinodal dewetting theory obeying a nonlinear relationship(D∝h5/3)in common laser heating.We also demonstrate the application of such a silver film with a grain size of~10.9 nm as a surface-enhanced Raman scattering chip,exhibiting superhigh spatial-uniformity and low detection limit down to 10-15 M.This anomalous refinement effect is general and can be extended to many other metallic films.
基金Project supported by the National Key R&D Program of China(Grant No.2019YFB1704600)the International Cooperation Research Project of Shenzhen(Grant No.GJHZ20180413182004161)+2 种基金the Hubei Provincial Natural Science Foundation of China(Grant No.2020CFA032)the National Natural Science Foundation of China(Grant No.51805395)the China Scholarship Council(Grant No.201906270142).
文摘Two-dimensional multiferroics,which simultaneously possess ferroelectricity and magnetism in a single phase,are well-known to possess great potential applications in nanoscale memories and spintronics.On the basis of first-principles calculations,a CrNCl_(2) monolayer is reported as an intrinsic multiferroic.The CrNCl_(2) has an antiferromagnetic ground state,with a N´eel temperature of about 88 K,and it exhibits an in-plane spontaneous polarization of 200 pC/m.The magnetic moments of CrNCl_(2) mainly come from the dxy orbital of the Cr cation,but the plane of the dxy orbital is perpendicular to the direction of the ferroelectric polarization,which hardly suppresses the occurrence of ferroelectricity.Therefore,the multiferroic exits in the CrNCl_(2).In addition,like CrNCl_(2),the CrNBr_(2) is an intrinsic multiferroic with antiferromagneticferroelectric ground state while CrNI_(2) is an intrinsic multiferroic with ferromagnetic-ferroelectric ground state.These findings enrich the multiferroics in the two-dimensional system and enable a wide range of applications in nanoscale devices.
基金supported by the National Natural Science Foundation of China (21673161 and 21905210)the Sino-German Center for Research Promotion (GZ 1400)。
文摘Two-dimensional(2 D) transition metal phosphides(TMPs) are predicted with many novel properties and various applications. As a member of TMPs family, molybdenum phosphide(MoP) exhibits many exotic physicochemical properties. However, the synthesis of high-quality2 D MoP single crystals is not reported due to the lack of reliable fabrication method, which limits the exploration of 2 D MoP. Here, we report the growth of high-quality ultrathin MoP single crystals with thickness down to 10 nm on liquid metals via chemical vapor deposition(CVD). The smooth surface of liquid Ga is regarded as a suitable growth substrate for producing 2 D MoP single crystals. The Mo source diffuses toward the Ga surface due to the high surface energy to react with phosphorus source, thus to fabricate ultrathin MoP single crystals. Then, we study the second harmonic generation(SHG) of 2 D MoP for the first time due to its intrinsic noncentrosymmetric structure. Our study provides an new approach to synthesize and explore other 2 D TMPs for future applications.
基金supported by the National Natural Science Foundation of China(51872188)Shenzhen Basic Research Program(SGDX20201103093600004)+4 种基金Special Funds for the Development of Strategic Emerging Industries in Shenzhen(20180309154519685)SZU Top Ranking Project(860-00000210)the PhD Start-up Fund of Natural Science Foundation of Guangdong Province(2018A030310573,2021A1515011155)China Postdoctoral Science Foundation(2018M643171)Center of Hydrogen Science,Shanghai Jiao Tong University,China.
文摘Engineering biomaterials to meet specific biomedical applications raises high requirements of mechanical performances,and simultaneous strengthening and toughening of polymer are frequently necessary but very challenging in many cases.In this work,we propose a new concept of nanoconcrete welding polymer chains,where mesoporous CaCO3(mCaCO_(3))nanoconcretes which are composed of amorphous and nanocrystalline phases are developed to powerfully weld polymer chains through siphoning-induced occlusion,hydration-driven crystallization and dehydration-driven compression of nanoconcretes.The mCaCO_(3) nanoconcrete welding technology is verified to be able to remarkably augment strength,toughness and anti-fatigue performances of a model polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-based porous membrane.Mechanistically,we have revealed polymer-occluded nanocrystal structure and welding-derived microstress which is much stronger than interfacial Van der Waals force,thus efficiently preventing the generation of microcracks and repairing initial microcracks by microcracks-induced hydration,crystallization and polymer welding of mCaCO_(3) nanoconcretes.Constructed porous membrane is used as wound dressing,exhibiting a special nanoplates-constructed surface topography as well as a porous structure with plentiful oriented,aligned and opened pore channels,improved hydrophilicity,water vapor permeability,anti-bacterial and cell adherence,in support of wound healing and skin structural/functional repairing.The proposed nanoconcrete-welding-polymer strategy breaks a new pathway for improving the mechanical performances of polymers.
