Here,a facile strategy is proposed for the preparation of lithiated graphdiyne quantum dots(GDY-Li QDs)with conjugated sp-and sp2-hybridized carbons by the self-assembly technique ofπ–πstacking of lithiated hexaeth...Here,a facile strategy is proposed for the preparation of lithiated graphdiyne quantum dots(GDY-Li QDs)with conjugated sp-and sp2-hybridized carbons by the self-assembly technique ofπ–πstacking of lithiated hexaethynylbezene under mild conditions.The as-prepared GDY-Li QDs,containing stacked multialkynyl aromatic backbone and abundant lithium(Li),show an average diameter of about 2.6 nm and good dispersion in the solvents.These distinctive structures endow GDY-Li QDs with superior properties that cannot be matched by traditional QDs,such as strong ion adsorption,Li-ion self-concentration,high Li-ion conductivity,the nanoconfinement effect,and ion solvation regulation.Benefiting from these features,GDY-Li QDs can stabilize Limetal anodes to effectively suppress Li-dendrite growth and significantly improve its Li plating/stripping coulombic efficiency(99.3%in the carbonate electrolyte).The full cells with GDY-Li QDs protected Li-metal anodes,and LiNi_(0.8)Co_(0.1)Mn^(0.1)O_(2)cathodes delivered high capacity and excellent cycling stability at high rates,which demonstrates the great potential of GDY-Li QDs for application in fast-charging Li-metal batteries.展开更多
Because of the advantages of excellent light stability, carbon dots（CDs） are considered to be a promising agent in the bio-marker application. Nevertheless, there are many unresolved issues with the toxicity of CDs ...Because of the advantages of excellent light stability, carbon dots（CDs） are considered to be a promising agent in the bio-marker application. Nevertheless, there are many unresolved issues with the toxicity of CDs in vitro and in vivo. In the study, CDs were synthesized by citric acid and ethylenediamine into deionized water, then the inhalation toxicity and bio-distribution of CDs in vivo were systematically assessed. The results showed that CDs caused animals death at higher dosages and induced injury in the lung and liver including inflammation and necrosis after single inhalation exposure at 5, 2 and 1 mg/kg dosages of the CDs. We also found that the injury increase with a dose-dependent and time-dependent manner. Fluorescent examination and TEM results showed that CDs mainly located at the lung and liver.And the fluorescent intensity increase with a time-dependent manner. This study provides a theoretical basis of the respiratory toxicity of CDs, and provides a basis for the use of CDs as a bio-marker.展开更多
The heat generation behaviors of fatigue crack are deeply investigated under different preload forces combing numerical simulation and experiment.Firstly,a multi-contact simulation model is applied to stimulate the cr...The heat generation behaviors of fatigue crack are deeply investigated under different preload forces combing numerical simulation and experiment.Firstly,a multi-contact simulation model is applied to stimulate the crack surfaces contact and the horn-sample contact under ultrasonic excitation for calculating the temperature fields.Then,the ultrasonic infrared thermography testing and the microscope testing are carried out for the heat generation and the plastic deformation behaviors of crack region under different preload forces.On this basis,an indirect observation method based on dots distribution is proposed to estimate the plastic deformation on crack contact surfaces.The obtained results show that the temperature rise of crack region increases with the increase of preload force when the preload force is less than 250 N,while the temperature rise rapidly declines due to the plastic deformation on crack contact surfaces and the inhibition effect when the preload force is 280 N.Moreover,the plastic deformation does not lead to the crack propagation,but reduces the detection repeatability of fatigue crack.This work provides an effective method for optimizing testing conditions in practical testing processes,which will be helpful to the establishment of testing standards for batches of test objects in ultrasonic infrared thermography testing.展开更多
High resolution and wide color gamut are two key requirements for novel display technologies. Owing to the distinguishing advantages over conventional displays, such as intrinsic wide color gamut and the possibility t...High resolution and wide color gamut are two key requirements for novel display technologies. Owing to the distinguishing advantages over conventional displays, such as intrinsic wide color gamut and the possibility to achieve high resolution, quantum dot light-emitting diodes (QLED) have drawn considerable attention in recent years. On the other hand, indium phosphide quantum dots (InP QDs) have shown a great potential as a replacement for cadmium selenide (CdSe) QDs in display applications due to the inherent toxicity of cadmium-based QDs. In this study, we investigate a top-emission InP-based green QLED with optimized angular distribution. By adjusting the electrical and optical architecture, the device exhibits improved properties with a maximum current efficiency of 30.1 cd/A and a narrowed full width at half maxima (FWHM)of 31 nm, which are the best results ever reported to our knowledge.展开更多
The correlation of single-particle imaging and absorption spectroscopy made the development of sizing curves possible and enabled rapid size determination of semiconductor nanocrystals based solely on optical properti...The correlation of single-particle imaging and absorption spectroscopy made the development of sizing curves possible and enabled rapid size determination of semiconductor nanocrystals based solely on optical properties.The increasing demand and production of such materials has resulted in a question of comparability between existing models and adequate volume-weighted size-determining measurement techniques.Small-angle X-ray scattering(SAXS)is a well-established method for obtaining nanostructural information from particle systems while operating sample quantities up to a commercial scale with a large amount of statistically based data.This work utilizes laboratory SAXS to characterize cadmium selenide nanocrystals with band edge energies between 1.97 and 3.08 eV.The evaluation of the scattering patterns is based on an indirect Fourier transformation(IFT),while dimensional parameters are derived from the model-free pair distance distribution functions(Dmode and Dg),as well as the modeled volume(Dv)and number(Dn)-weighted size-density distributions.We find that comparable data from D̅n agree well with existing X-ray diffraction(XRD)and with transmission electron microscopy(TEM)results described in literature;this qualifies SAXS as an equivalent integral characterization method.Although based on an estimate,the radius of gyration yields equivalent accurate results.Additionally,corresponding volume-weighted data are shown that can be useful when transferring information to other techniques.Dmode parametrization represents the largest estimated size of the sample and implies that particles interact and deviate from the spherical morphology,whereas Dv demonstrates results not considering such effects.A full set of the parameters discussed quantifies the quality of a sample.展开更多
In this paper, we perform systematic calculations of the stress and strain distributions in InAs/GaAs truncated pyramidal quantum dots （QDs） with different wetting layer （WL） thickness, using the finite element me...In this paper, we perform systematic calculations of the stress and strain distributions in InAs/GaAs truncated pyramidal quantum dots （QDs） with different wetting layer （WL） thickness, using the finite element method （FEM）. The stresses and strains are concentrated at the boundaries of the WL and QDs, are reduced gradually from the boundaries to the interior, and tend to a uniform state for the positions away from the boundaries. The maximal strain energy density occurs at the vicinity of the interface between the WL and the substrate. The stresses, strains and released strain energy are reduced gradually with increasing WL thickness. The above results show that a critical WL thickness may exist, and the stress and strain distributions can make the growth of QDs a growth of strained three-dimensional island when the WL thickness is above the critical value, and FEM can be applied to investigate such nanosystems, QDs, and the relevant results are supported by the experiments.展开更多
Temperature-dependent photoluminescence （PL） of phase-separated InGaN quantum wells is investigated over a broader excitation power range. With increasing excitation power from 0.5 pW to 50 mW, the In-rich quasi-qua...Temperature-dependent photoluminescence （PL） of phase-separated InGaN quantum wells is investigated over a broader excitation power range. With increasing excitation power from 0.5 pW to 50 mW, the In-rich quasi-quantum dot （QD）-related PL peak disappears at about 3 mW, while temperature behavior of the InGaN matrix-related PL peak energy （linewidth） gradually evolves from a strong ＂S-shaped＂ （＂W-shaped＂） temperature dependence into a weak ＂S-shaped＂ （an approximately ＂V-shaped＂）, until becoming an inverted ＂V-shaped＂ （a monotonically increasing） temperature dependence. This indicates that, with increasing excitation power, the carrier localization effect is gradually reduced and the QD-related transition is submerged by the significantly enhanced InGaN matrix-related transition, while the carrier thermalization effect gradually increases to become predominant at high excitation powers.展开更多
Self-assembled lnAs quantum dots （QDs） are grown on vicinal GaAs （100） substrates by using metal-organic chemical vapour deposition （MOCVD）. An abnormal temperature dependence of bimodal size distribution of InA...Self-assembled lnAs quantum dots （QDs） are grown on vicinal GaAs （100） substrates by using metal-organic chemical vapour deposition （MOCVD）. An abnormal temperature dependence of bimodal size distribution of InAs quantum dots is found. As the temperature increases, the density of the small dots grows larger while the density of the large dots turns smaller, which is contrary to the evolution of QDs on exact GaAs （100） substrates. This trend is explained by taking into account the presence of multiatoinic steps on the substrates. The optical properties of InAs QDs on vicinal GaAs（100） substrates are also studied by photoluminescence （PL） . It is found that dots on a vicinal substrate have a longer emission wavelength, a narrower PL line width and a much larger PL intensity.展开更多
基金supported by the National Natural Science Foundation of China(20873162)State Key Laboratory of Pollution Control and Resource Reuse Foundation of China(PCRRF09006)~~
基金supported by the National Key Research and Development Project of China(grant nos.2022YFA1204500 and 2022YFA1204503)the National Natural Science Foundation of China(grant nos.52072222 and 22279073)+1 种基金the Natural Science Foundation of Shandong Province(grant no.ZR2022ZD35)the Taishan Scholar Project of Shandong Province of China(grant no.62460082061017).
文摘Here,a facile strategy is proposed for the preparation of lithiated graphdiyne quantum dots(GDY-Li QDs)with conjugated sp-and sp2-hybridized carbons by the self-assembly technique ofπ–πstacking of lithiated hexaethynylbezene under mild conditions.The as-prepared GDY-Li QDs,containing stacked multialkynyl aromatic backbone and abundant lithium(Li),show an average diameter of about 2.6 nm and good dispersion in the solvents.These distinctive structures endow GDY-Li QDs with superior properties that cannot be matched by traditional QDs,such as strong ion adsorption,Li-ion self-concentration,high Li-ion conductivity,the nanoconfinement effect,and ion solvation regulation.Benefiting from these features,GDY-Li QDs can stabilize Limetal anodes to effectively suppress Li-dendrite growth and significantly improve its Li plating/stripping coulombic efficiency(99.3%in the carbonate electrolyte).The full cells with GDY-Li QDs protected Li-metal anodes,and LiNi_(0.8)Co_(0.1)Mn^(0.1)O_(2)cathodes delivered high capacity and excellent cycling stability at high rates,which demonstrates the great potential of GDY-Li QDs for application in fast-charging Li-metal batteries.
基金financial support from the National Natural Science Foundation of China (Nos. 61571426, 61671435, 31400854)National Hi-Tech. Research and Development Program of China (No. 2013AA032201)Beijing Natural Science Foundation (No. 4161003)
文摘Because of the advantages of excellent light stability, carbon dots（CDs） are considered to be a promising agent in the bio-marker application. Nevertheless, there are many unresolved issues with the toxicity of CDs in vitro and in vivo. In the study, CDs were synthesized by citric acid and ethylenediamine into deionized water, then the inhalation toxicity and bio-distribution of CDs in vivo were systematically assessed. The results showed that CDs caused animals death at higher dosages and induced injury in the lung and liver including inflammation and necrosis after single inhalation exposure at 5, 2 and 1 mg/kg dosages of the CDs. We also found that the injury increase with a dose-dependent and time-dependent manner. Fluorescent examination and TEM results showed that CDs mainly located at the lung and liver.And the fluorescent intensity increase with a time-dependent manner. This study provides a theoretical basis of the respiratory toxicity of CDs, and provides a basis for the use of CDs as a bio-marker.
基金Project(2019M650262)supported by the China Postdoctoral Science FoundationProject(92060106)supported by the Major Research Plan of National Natural Science Foundation of ChinaProject(201803U8003)supported by the China Aeronautical Science Foundation。
文摘The heat generation behaviors of fatigue crack are deeply investigated under different preload forces combing numerical simulation and experiment.Firstly,a multi-contact simulation model is applied to stimulate the crack surfaces contact and the horn-sample contact under ultrasonic excitation for calculating the temperature fields.Then,the ultrasonic infrared thermography testing and the microscope testing are carried out for the heat generation and the plastic deformation behaviors of crack region under different preload forces.On this basis,an indirect observation method based on dots distribution is proposed to estimate the plastic deformation on crack contact surfaces.The obtained results show that the temperature rise of crack region increases with the increase of preload force when the preload force is less than 250 N,while the temperature rise rapidly declines due to the plastic deformation on crack contact surfaces and the inhibition effect when the preload force is 280 N.Moreover,the plastic deformation does not lead to the crack propagation,but reduces the detection repeatability of fatigue crack.This work provides an effective method for optimizing testing conditions in practical testing processes,which will be helpful to the establishment of testing standards for batches of test objects in ultrasonic infrared thermography testing.
基金This work was supported by the National Key R&D Program of China under Grant No.2016YFB0401700.
文摘High resolution and wide color gamut are two key requirements for novel display technologies. Owing to the distinguishing advantages over conventional displays, such as intrinsic wide color gamut and the possibility to achieve high resolution, quantum dot light-emitting diodes (QLED) have drawn considerable attention in recent years. On the other hand, indium phosphide quantum dots (InP QDs) have shown a great potential as a replacement for cadmium selenide (CdSe) QDs in display applications due to the inherent toxicity of cadmium-based QDs. In this study, we investigate a top-emission InP-based green QLED with optimized angular distribution. By adjusting the electrical and optical architecture, the device exhibits improved properties with a maximum current efficiency of 30.1 cd/A and a narrowed full width at half maxima (FWHM)of 31 nm, which are the best results ever reported to our knowledge.
基金The authors thank the Laboratory for Nano and Quantum Engineering(LNQE),Leibniz University Hannover,for the access to the TEM instrument and Dr.Brian Pauw from the Bundesanstalt für Materialforschung und-prüfung(BAM)in Berlin for the scientific discussion about SAXS and the provision of the Ag-reference.We also acknowledge the work of David Niedbalka and Marcel Pastuschek who contributed to this research during their time as students.This research was partially funded by Niedersächsisches Ministerium für Wissenschaft und Kultur through the“Quantumand Nano-Metrology(QUANOMET)”initiative(ZN3245)within the scope of the NP-1 project.Furthermore,we acknowledge financial travel support by the DFG Research Training Group GrK1952“Metrology for Complex Nanosystems(NanoMet)”.
文摘The correlation of single-particle imaging and absorption spectroscopy made the development of sizing curves possible and enabled rapid size determination of semiconductor nanocrystals based solely on optical properties.The increasing demand and production of such materials has resulted in a question of comparability between existing models and adequate volume-weighted size-determining measurement techniques.Small-angle X-ray scattering(SAXS)is a well-established method for obtaining nanostructural information from particle systems while operating sample quantities up to a commercial scale with a large amount of statistically based data.This work utilizes laboratory SAXS to characterize cadmium selenide nanocrystals with band edge energies between 1.97 and 3.08 eV.The evaluation of the scattering patterns is based on an indirect Fourier transformation(IFT),while dimensional parameters are derived from the model-free pair distance distribution functions(Dmode and Dg),as well as the modeled volume(Dv)and number(Dn)-weighted size-density distributions.We find that comparable data from D̅n agree well with existing X-ray diffraction(XRD)and with transmission electron microscopy(TEM)results described in literature;this qualifies SAXS as an equivalent integral characterization method.Although based on an estimate,the radius of gyration yields equivalent accurate results.Additionally,corresponding volume-weighted data are shown that can be useful when transferring information to other techniques.Dmode parametrization represents the largest estimated size of the sample and implies that particles interact and deviate from the spherical morphology,whereas Dv demonstrates results not considering such effects.A full set of the parameters discussed quantifies the quality of a sample.
基金Project supported by the National Natural Science Foundation of China （Grant No 90101004） and by the National Basic Research Program of China （Grant No G2000067102）.
文摘In this paper, we perform systematic calculations of the stress and strain distributions in InAs/GaAs truncated pyramidal quantum dots （QDs） with different wetting layer （WL） thickness, using the finite element method （FEM）. The stresses and strains are concentrated at the boundaries of the WL and QDs, are reduced gradually from the boundaries to the interior, and tend to a uniform state for the positions away from the boundaries. The maximal strain energy density occurs at the vicinity of the interface between the WL and the substrate. The stresses, strains and released strain energy are reduced gradually with increasing WL thickness. The above results show that a critical WL thickness may exist, and the stress and strain distributions can make the growth of QDs a growth of strained three-dimensional island when the WL thickness is above the critical value, and FEM can be applied to investigate such nanosystems, QDs, and the relevant results are supported by the experiments.
文摘Temperature-dependent photoluminescence （PL） of phase-separated InGaN quantum wells is investigated over a broader excitation power range. With increasing excitation power from 0.5 pW to 50 mW, the In-rich quasi-quantum dot （QD）-related PL peak disappears at about 3 mW, while temperature behavior of the InGaN matrix-related PL peak energy （linewidth） gradually evolves from a strong ＂S-shaped＂ （＂W-shaped＂） temperature dependence into a weak ＂S-shaped＂ （an approximately ＂V-shaped＂）, until becoming an inverted ＂V-shaped＂ （a monotonically increasing） temperature dependence. This indicates that, with increasing excitation power, the carrier localization effect is gradually reduced and the QD-related transition is submerged by the significantly enhanced InGaN matrix-related transition, while the carrier thermalization effect gradually increases to become predominant at high excitation powers.
基金Project supported by the National Natural Science Foundation of China （Grant No 60476009）.
文摘Self-assembled lnAs quantum dots （QDs） are grown on vicinal GaAs （100） substrates by using metal-organic chemical vapour deposition （MOCVD）. An abnormal temperature dependence of bimodal size distribution of InAs quantum dots is found. As the temperature increases, the density of the small dots grows larger while the density of the large dots turns smaller, which is contrary to the evolution of QDs on exact GaAs （100） substrates. This trend is explained by taking into account the presence of multiatoinic steps on the substrates. The optical properties of InAs QDs on vicinal GaAs（100） substrates are also studied by photoluminescence （PL） . It is found that dots on a vicinal substrate have a longer emission wavelength, a narrower PL line width and a much larger PL intensity.
