Coal direct liquefaction technology is a crucial contemporary coal chemical technology for efficient and clean use of coal resources. The development of direct coal liquefaction technology and the promotion of alterna...Coal direct liquefaction technology is a crucial contemporary coal chemical technology for efficient and clean use of coal resources. The development of direct coal liquefaction technology and the promotion of alternative energy sources are important measures to guarantee energy security and economic security. However, several challenges need to be addressed, including low conversion rate, inadequate oil yield, significant coking, demanding reaction conditions, and high energy consumption. Extensive research has been conducted on these issues, but further exploration is required in certain aspects such as pyrolysis of macromolecules during the liquefaction process, hydrogen activation, catalysts' performance and stability, solvent hydrogenation, as well as interactions between free radicals to understand their mechanisms better. This paper presents a comprehensive analysis of the design strategy for efficient catalysts in coal liquefaction, encompassing the mechanism of coal liquefaction, catalyst construction,and enhancement of catalytic conversion efficiency. It serves as a comprehensive guide for further research endeavors. Firstly, it systematically summarizes the conversion mechanism of direct coal liquefaction, provides detailed descriptions of various catalyst design strategies, and especially outlines the catalytic mechanism. Furthermore, it addresses the challenges and prospects associated with constructing efficient catalysts for direct coal liquefaction based on an understanding of their action mechanisms.展开更多
A CMOS compatible RRAM device with TaN/Ta/TaOx/Ta N structure was proposed for nonvolatile memory applications.Excellent resistive switching characteristics,including low operation voltages(<1 V),low operation curr...A CMOS compatible RRAM device with TaN/Ta/TaOx/Ta N structure was proposed for nonvolatile memory applications.Excellent resistive switching characteristics,including low operation voltages(<1 V),low operation current(<100μA),good programming/erasing endurance(>10^(6) cycles),satisfactory uniformity,and reliable data retention,have been demonstrated.Furthermore,all of the elements in the fabricated Ta N/Ta/Ta Ox/Ta N devices are highly compatible with modern CMOS manufacturing process,showing promising application in the next generation of nonvolatile memory.展开更多
Diminishing the size of active sites in catalysts is promis-ing to improve the kinetics of oxygen reduction reaction(ORR)and reduce the cost of metal-air batteries.However,the facile preparation of high-performance ca...Diminishing the size of active sites in catalysts is promis-ing to improve the kinetics of oxygen reduction reaction(ORR)and reduce the cost of metal-air batteries.However,the facile preparation of high-performance catalysts with nanoscale active sites still suffers from great challenge.Herein,we report a facile template-free strategy to fabri-cate Co single atoms and nanoparticles dispersed on porous N-doped carbon nanotube(Co-NCNT)by the pyrolysis of the composites of metal-organic complexes and porous carbon nanotube.Different from the conventional strategy,the precursor metal-organic complexes in this work were prepared under mild conditions and used without complex purification procedures.Compared with the pristine carbon nanotube,N-doped carbon nanotube with abundant meso-pores contribute to the formation of nanoscale Co sites.展开更多
Transition metal dichalcogenides(TMDs)have emerged as a promising electrocatalyst for hydrogen evo-lution reaction(HER)due to its excellent conductivity and abundant electrocatalytic active sites of its edges.TMDs nan...Transition metal dichalcogenides(TMDs)have emerged as a promising electrocatalyst for hydrogen evo-lution reaction(HER)due to its excellent conductivity and abundant electrocatalytic active sites of its edges.TMDs nanowall can expose abundant of edges so that they tend to show better catalytic performance for hydrogen evolution reaction.Herein,PtSe_(2) nanowall films with morphology controlled at centimeters level are synthesized by selenizing Pt film.The dynamic and thermodynamics of selenation reaction are investigated.The nanowall structure can be obtained by controlling the growth temperature,and the thickness of nanowall can be tuned by the original thickness of Pt film.The Pt atoms can be rearranged into ordered distribution at 550℃ and can be induced to well-ordered PtSe_(2) nanowalls finally.The well-ordered PtSe_(2) nanowall films show excellent HER performance,with an overpotential of 0.3 V at-10 mA·cm^(-2) and a Tafel slope of~52 mV·dec^(-1).This work demonstrates the great potential of activated 2D PtSe_(2) as an ultrathin film catalyst for the HER,which is valuable to provide instruction and afford experience for further application at industrial level.展开更多
Interactions between diet and the intestinal microbiome play an important role in human health and disease development.It is well known that such interactions,whether direct or indirect,trigger a series of metabolic r...Interactions between diet and the intestinal microbiome play an important role in human health and disease development.It is well known that such interactions,whether direct or indirect,trigger a series of metabolic reactions in the body.Evidence suggests that intestinal stem cells(ISCs),which are phenotypic precursors of various intestinal epithelial cells,play a significant role in the regulation of intestinal barrier function and homeostasis.The advent and evolution of intestinal organoid culture techniques have presented a key opportunity to study the association between the intestinal microenvironment and ISCs.As a result,the effects exerted by dietary factors,intestinal microbiomes,and their metabolites on the metabolic regulation of ISCs and the potential mechanisms underlying such effects are being gradually revealed.This review summarises the effects of different dietary patterns on the behaviour and functioning of ISCs and focuses on the crosstalk between intestinal microbiota,related metabolites,and ISCs,with the aim of fully understanding the relationship between these three factors and providing further insights into the complex mechanisms associated with ISCs in the human body.Gaining an understanding of these mechanisms may lead to the development of novel dietary interventions or drugs conducive to intestinal health.展开更多
AlGaN-based ultraviolet light-emitting diodes(UV-LEDs) have attracted considerable interest due to their wide range of application fields. However, they are still suffering from low light out power and unsatisfactory ...AlGaN-based ultraviolet light-emitting diodes(UV-LEDs) have attracted considerable interest due to their wide range of application fields. However, they are still suffering from low light out power and unsatisfactory quantum efficiency.The utilization of polarization-doped technique by grading the Al content in p-type layer has demonstrated its effectiveness in improving LED performances by providing sufficiently high hole concentration. However, too large degree of grading through monotonously increasing the Al content causes strains in active regions, which constrains application of this technique, especially for short wavelength UV-LEDs. To further improve 340-nm UV-LED performances, segmentally graded Al content p-Al_xGa_(1-x)N has been proposed and investigated in this work. Numerical results show that the internal quantum efficiency and output power of proposed structures are improved due to the enhanced carrier concentrations and radiative recombination rate in multiple quantum wells, compared to those of the conventional UV-LED with a stationary Al content AlGaN electron blocking layer. Moreover, by adopting the segmentally graded p-Al_xGa_(1-x)N, band bending within the last quantum barrier/p-type layer interface is effectively eliminated.展开更多
Organic active units often transform into radical intermediates during the redox processes but exhibit poor cycling stability due to the uncontrollable redox of the radicals. Herein, we report a facile and efficient s...Organic active units often transform into radical intermediates during the redox processes but exhibit poor cycling stability due to the uncontrollable redox of the radicals. Herein, we report a facile and efficient strategy to modulate the molecular orbital energies, charge transport capacities, and spin electron densities of the active units in covalent organic frameworks(COFs) via regulating the conjugated unit size to optimize the redox activity and stability of the organic radicals. COFs based on different imide conjugated units exhibit tunable discharge voltages, rate performance and cycling stabilities. Detailed characterizations and theoretical calculation reveal that imide radicals are the important active intermediates during the redox processes of these COFs. Specifically, increasing the size of the imide conjugated units could effectively delocalize the radical electrons and improve the stability of the COFs electrodes. This study offers a very effective strategy to modulate the redox chemistry of organic materials for electrochemical energy storage.展开更多
Silicon carbide nanotubes(SiCNTs) have broad application prospects in the field of micro-nanodevices due to their excellent physical properties. Based on first-principles, the difference between optical properties of ...Silicon carbide nanotubes(SiCNTs) have broad application prospects in the field of micro-nanodevices due to their excellent physical properties. Based on first-principles, the difference between optical properties of SiCNTs where C atom or Si atom is replaced by group-V element is studied. The results show that the optical absorptions of SiCNTs doped by different elements are significantly different in the band of 600 nm–1500 nm. The differences in photoconductivity, caused by different doping elements, are reflected mainly in the band above 620 nm, the difference in dielectric function and refractive index of SiCNTs are reflected mainly in the band above 500 nm. Further analysis shows that SiCNTs doped with different elements change their band structures, resulting in the differences among their optical properties. The calculation of formation energy shows that SiCNTs are more stable when group-V element replaces Si atom, except N atom. These research results will be beneficial to the applications of SiC nanomaterials in optoelectronic devices and provide a theoretical basis for selecting the SiCNTs' dopants.展开更多
The flower-like silver nanoparticles have been synthesized by reducing silver nitrate （AgNO3） with ascorbic acid （AA） as the reductant and polyvinyl pyrrolidone （PVP） as the capping agent under vigorous stirring...The flower-like silver nanoparticles have been synthesized by reducing silver nitrate （AgNO3） with ascorbic acid （AA） as the reductant and polyvinyl pyrrolidone （PVP） as the capping agent under vigorous stirring. Such flower-like nanoparticles are aggregates of small nanoplates and nanorods. They were tested as substrates for the surface-enhanced Raman scattering （SERS）, showing high sensitivity for detecting Rhodamine 6G （RBG） at a concentration as low as 10 7 mol/L. It has been found that replacing mechanical stirring with ultrasound sonication would drastically change the particle morphology, from flower-like nanoparticles to well-dispersed smaller nanoparticles. Furthermore, when trace amounts of NaC1 were added into the reagents, well-dispersed Ag nanoparticles formed even in vigorous stirring. These phenomena can be explained with the diffusion and reactant supply during nucleation and growth of Ag nanoparticles.展开更多
基金National Natural Science Foundation of China (No. 22208273)Tianchi Talent Plan of Xinjiang Uygur Autonomous RegionPostdoctoral Fellowship Program of CPSF under Grant Number GZC20240428。
文摘Coal direct liquefaction technology is a crucial contemporary coal chemical technology for efficient and clean use of coal resources. The development of direct coal liquefaction technology and the promotion of alternative energy sources are important measures to guarantee energy security and economic security. However, several challenges need to be addressed, including low conversion rate, inadequate oil yield, significant coking, demanding reaction conditions, and high energy consumption. Extensive research has been conducted on these issues, but further exploration is required in certain aspects such as pyrolysis of macromolecules during the liquefaction process, hydrogen activation, catalysts' performance and stability, solvent hydrogenation, as well as interactions between free radicals to understand their mechanisms better. This paper presents a comprehensive analysis of the design strategy for efficient catalysts in coal liquefaction, encompassing the mechanism of coal liquefaction, catalyst construction,and enhancement of catalytic conversion efficiency. It serves as a comprehensive guide for further research endeavors. Firstly, it systematically summarizes the conversion mechanism of direct coal liquefaction, provides detailed descriptions of various catalyst design strategies, and especially outlines the catalytic mechanism. Furthermore, it addresses the challenges and prospects associated with constructing efficient catalysts for direct coal liquefaction based on an understanding of their action mechanisms.
基金Project supported by the Key Research and Development Program of Gansu Province-Industrial Project(Grant No.25YFGA005)。
文摘A CMOS compatible RRAM device with TaN/Ta/TaOx/Ta N structure was proposed for nonvolatile memory applications.Excellent resistive switching characteristics,including low operation voltages(<1 V),low operation current(<100μA),good programming/erasing endurance(>10^(6) cycles),satisfactory uniformity,and reliable data retention,have been demonstrated.Furthermore,all of the elements in the fabricated Ta N/Ta/Ta Ox/Ta N devices are highly compatible with modern CMOS manufacturing process,showing promising application in the next generation of nonvolatile memory.
基金financially supported by the National Natural Science Foundation of China (No.21875097)the Basic Research Project of the Science and Technology Innovation Commission of Shenzhen (Nos.JCYJ20200109141640095 and No.JCYJ20190809115413414)+3 种基金Shenzhen Key Laboratory of Interfacial Science and Engineering of Materials (No. ZDSYS20200421111401738)the Leading Talents of Guangdong Province Program (No.2016LJ06C536)Guangdong-Hong Kong-Macao Joint Laboratory (No.2019B121205001)partially supported by Hong Kong Research Grants Council (No. CityU 11218420)
文摘Diminishing the size of active sites in catalysts is promis-ing to improve the kinetics of oxygen reduction reaction(ORR)and reduce the cost of metal-air batteries.However,the facile preparation of high-performance catalysts with nanoscale active sites still suffers from great challenge.Herein,we report a facile template-free strategy to fabri-cate Co single atoms and nanoparticles dispersed on porous N-doped carbon nanotube(Co-NCNT)by the pyrolysis of the composites of metal-organic complexes and porous carbon nanotube.Different from the conventional strategy,the precursor metal-organic complexes in this work were prepared under mild conditions and used without complex purification procedures.Compared with the pristine carbon nanotube,N-doped carbon nanotube with abundant meso-pores contribute to the formation of nanoscale Co sites.
基金the National Natural Science Foundation of China(No.51802266)Shaanxi’s Key Project of Research and Development Plan(No.2021GY-217)+1 种基金the Research Funds for Interdisciplinary Subject of NWPU(No.19SH0304)the Fundamental Research Funds for the Central Universities(No.3102017jc01001)。
文摘Transition metal dichalcogenides(TMDs)have emerged as a promising electrocatalyst for hydrogen evo-lution reaction(HER)due to its excellent conductivity and abundant electrocatalytic active sites of its edges.TMDs nanowall can expose abundant of edges so that they tend to show better catalytic performance for hydrogen evolution reaction.Herein,PtSe_(2) nanowall films with morphology controlled at centimeters level are synthesized by selenizing Pt film.The dynamic and thermodynamics of selenation reaction are investigated.The nanowall structure can be obtained by controlling the growth temperature,and the thickness of nanowall can be tuned by the original thickness of Pt film.The Pt atoms can be rearranged into ordered distribution at 550℃ and can be induced to well-ordered PtSe_(2) nanowalls finally.The well-ordered PtSe_(2) nanowall films show excellent HER performance,with an overpotential of 0.3 V at-10 mA·cm^(-2) and a Tafel slope of~52 mV·dec^(-1).This work demonstrates the great potential of activated 2D PtSe_(2) as an ultrathin film catalyst for the HER,which is valuable to provide instruction and afford experience for further application at industrial level.
基金supported by the National Natural Science Foundation of China(81973837)Scientific and technological innovation project of China Academy of Chinese Medical Sciences(CI2021A016)National Key projects for international cooperation on science,technology and innovation(2021YFE0201100).
文摘Interactions between diet and the intestinal microbiome play an important role in human health and disease development.It is well known that such interactions,whether direct or indirect,trigger a series of metabolic reactions in the body.Evidence suggests that intestinal stem cells(ISCs),which are phenotypic precursors of various intestinal epithelial cells,play a significant role in the regulation of intestinal barrier function and homeostasis.The advent and evolution of intestinal organoid culture techniques have presented a key opportunity to study the association between the intestinal microenvironment and ISCs.As a result,the effects exerted by dietary factors,intestinal microbiomes,and their metabolites on the metabolic regulation of ISCs and the potential mechanisms underlying such effects are being gradually revealed.This review summarises the effects of different dietary patterns on the behaviour and functioning of ISCs and focuses on the crosstalk between intestinal microbiota,related metabolites,and ISCs,with the aim of fully understanding the relationship between these three factors and providing further insights into the complex mechanisms associated with ISCs in the human body.Gaining an understanding of these mechanisms may lead to the development of novel dietary interventions or drugs conducive to intestinal health.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61874161 and 11474105)the Science and Technology Program of Guangdong Province,China(Grant Nos.2017B010127001 and 2015B010105011)+4 种基金the Education Department Project of Guangdong Province,China(Grant No.2017KZDXM022)the Science and Technology Project of Guangzhou City,China(Grant No.201607010246)the Program for Changjiang Scholars and Innovative Research Team in Universities of China(Grant No.IRT13064)the Science and Technology Project of Shenzhen City,China(Grant No.GJHZ20180416164721073)the Science and Technology Planning of Guangdong Province,China(Grant No.2015B010112002)
文摘AlGaN-based ultraviolet light-emitting diodes(UV-LEDs) have attracted considerable interest due to their wide range of application fields. However, they are still suffering from low light out power and unsatisfactory quantum efficiency.The utilization of polarization-doped technique by grading the Al content in p-type layer has demonstrated its effectiveness in improving LED performances by providing sufficiently high hole concentration. However, too large degree of grading through monotonously increasing the Al content causes strains in active regions, which constrains application of this technique, especially for short wavelength UV-LEDs. To further improve 340-nm UV-LED performances, segmentally graded Al content p-Al_xGa_(1-x)N has been proposed and investigated in this work. Numerical results show that the internal quantum efficiency and output power of proposed structures are improved due to the enhanced carrier concentrations and radiative recombination rate in multiple quantum wells, compared to those of the conventional UV-LED with a stationary Al content AlGaN electron blocking layer. Moreover, by adopting the segmentally graded p-Al_xGa_(1-x)N, band bending within the last quantum barrier/p-type layer interface is effectively eliminated.
基金supports from the Basic Research Project of the Science and Technology Innovation Commission of Shenzhen (No. JCYJ20200109141640095)the Shenzhen Key Laboratory of Interfacial Science and Engineering of Materials (No. ZDSYS20200421111401738)+3 种基金the Leading Talents of Guangdong Province Program (No. 2016LJ06C536)the GuangdongHong Kong-Macao Joint Laboratory (No. 2019B121205001)the National Natural Science Foundation of China (No. 21875097)the support from the Hong Kong Research Grants Council (Project number CityU 11218420)。
文摘Organic active units often transform into radical intermediates during the redox processes but exhibit poor cycling stability due to the uncontrollable redox of the radicals. Herein, we report a facile and efficient strategy to modulate the molecular orbital energies, charge transport capacities, and spin electron densities of the active units in covalent organic frameworks(COFs) via regulating the conjugated unit size to optimize the redox activity and stability of the organic radicals. COFs based on different imide conjugated units exhibit tunable discharge voltages, rate performance and cycling stabilities. Detailed characterizations and theoretical calculation reveal that imide radicals are the important active intermediates during the redox processes of these COFs. Specifically, increasing the size of the imide conjugated units could effectively delocalize the radical electrons and improve the stability of the COFs electrodes. This study offers a very effective strategy to modulate the redox chemistry of organic materials for electrochemical energy storage.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11574261 and 51132002)the Natural Science Foundation of Hebei Province,China (Grant No. A2015203261)。
文摘Silicon carbide nanotubes(SiCNTs) have broad application prospects in the field of micro-nanodevices due to their excellent physical properties. Based on first-principles, the difference between optical properties of SiCNTs where C atom or Si atom is replaced by group-V element is studied. The results show that the optical absorptions of SiCNTs doped by different elements are significantly different in the band of 600 nm–1500 nm. The differences in photoconductivity, caused by different doping elements, are reflected mainly in the band above 620 nm, the difference in dielectric function and refractive index of SiCNTs are reflected mainly in the band above 500 nm. Further analysis shows that SiCNTs doped with different elements change their band structures, resulting in the differences among their optical properties. The calculation of formation energy shows that SiCNTs are more stable when group-V element replaces Si atom, except N atom. These research results will be beneficial to the applications of SiC nanomaterials in optoelectronic devices and provide a theoretical basis for selecting the SiCNTs' dopants.
基金financial support for this work from the Natural Science Foundation for Young Scientists of Shanxi Province of China (No. 2015021078)International Cooperation of Science and Technology Project in Shanxi Province of China (No. 2014081006-2)
文摘The flower-like silver nanoparticles have been synthesized by reducing silver nitrate （AgNO3） with ascorbic acid （AA） as the reductant and polyvinyl pyrrolidone （PVP） as the capping agent under vigorous stirring. Such flower-like nanoparticles are aggregates of small nanoplates and nanorods. They were tested as substrates for the surface-enhanced Raman scattering （SERS）, showing high sensitivity for detecting Rhodamine 6G （RBG） at a concentration as low as 10 7 mol/L. It has been found that replacing mechanical stirring with ultrasound sonication would drastically change the particle morphology, from flower-like nanoparticles to well-dispersed smaller nanoparticles. Furthermore, when trace amounts of NaC1 were added into the reagents, well-dispersed Ag nanoparticles formed even in vigorous stirring. These phenomena can be explained with the diffusion and reactant supply during nucleation and growth of Ag nanoparticles.
