Smart energy storage has revolutionized portable electronics and electrical vehicles.The current smart energy storage devices have penetrated into flexible electronic markets at an unprecedented rate.Flexible batterie...Smart energy storage has revolutionized portable electronics and electrical vehicles.The current smart energy storage devices have penetrated into flexible electronic markets at an unprecedented rate.Flexible batteries are key power sources to enable vast flexible devices,which put forward additional requirements,such as bendable,twistable,stretchable,and ultrathin,to adapt mechanical deformation under the working conditions.This review summarizes the recent advances in construction and configuration of flexible batteries and discusses the general metrics to benchmark various flexible batteries with different materials and chemistries.Moreover,we present advanced prototype flexible batteries developed by some companies to afford general envision of the technological status.Lastly,the critical points are summarized in the development of flexible batteries and remaining challenges are also presented for the future design of flexible batteries in practical perspectives.展开更多
Hexagonal ultrathin WO3 nano-ribbons （HUWNRs） of subnanometer thicknesses, 2-5 nm widths, and lengths of up to several micrometers were prepared by a solvothermal method. The as-prepared HUWNRs grow along the [001] ...Hexagonal ultrathin WO3 nano-ribbons （HUWNRs） of subnanometer thicknesses, 2-5 nm widths, and lengths of up to several micrometers were prepared by a solvothermal method. The as-prepared HUWNRs grow along the [001] direction, and the main exposed facet is the （720） crystal plane. The HUWNRs exhibit good electrochemical performance as an anode material in lithium ion batteries because of their unique structure. It is believed that these unique materials may be applied in many fields.展开更多
The assembly of thin films （TFs） having long-lasting luminescence can be expected to play an important role in the development of new-generation smart sensors, anti-counterfeiting materials, and information-encrypti...The assembly of thin films （TFs） having long-lasting luminescence can be expected to play an important role in the development of new-generation smart sensors, anti-counterfeiting materials, and information-encryption systems. However, such films are limited compared with their powder and solution counterparts. In this study, by exploiting the self-organization of phosphors in the two-dimensional （2D） galleries between clay nanosheets, we developed a method for the ordered assembly of long-afterglow TFs by utilizing a hydrogen-bonding layer-by-layer （LBL） process. Compared with the pristine powder, the TFs exhibit high polarization and up-conversion room-temperature phosphorescence （RTP）, as well as enhanced quantum yields and luminescence lifetimes, allowing them to be used as room-temperature phosphorescent sensors for humidity and oxygen. Moreover, modified clay-based hybrids with multicolor RTP can serve as anti-counterfeiting marks and triple-mode 2D barcode displays. We anticipate that the LBL assembly process can be extended to the fabrication of other inorganic--organic room-temperature phosphorescent hybrids with smart luminescent sensor and antiforgery applications.展开更多
Photocatalytic hydrogen production represents a promising strategy for clean, sustainable, and environmentfriendly energy supply. Up to now, great efforts have been devoted to designing the photocatalysts with noble m...Photocatalytic hydrogen production represents a promising strategy for clean, sustainable, and environmentfriendly energy supply. Up to now, great efforts have been devoted to designing the photocatalysts with noble metal as co-catalyst for visible-light-driven hydrogen evolution, while more efficient photocatalytic systems are still a major challenge. Herein, we report a facile strategy for synthesizing faceto-face ultrathin Pd nanosheets-amorphous carbon nitride(Pd NSs-ACN) structure with large contacting interface and short electronic transmission pathway, which can work as an efficient photocatalyst for hydrogen production. The synthesis starts with the growth of ultrathin Pd NSs, followed by assembly with the visible-light-response ACN through a simple stirring and annealing procedure. The resultant two dimensional face-to-face structures deliver an average hydrogen generation rate of 1.45 mmol h-1g-1 at a temperature of 25℃,almost 2.6 times higher than that of Pd Nps-ACN with particle-to-face structural feature. The efficient photocatalytic activity is ascribed to the formation of high-density of active sites between ultrafine face-to-face contacted Pd NSs and the ACN, which cooperate more synergistically towards photocatalytic hydrogen production. The face-to-face engineered Pd NSs-ACN hybrids also offer a good stability revealed by photocatalytic hydrogen production measurements. The extraordinary performance highlights a powerful engineering model for designing other face-to-face contacting co-catalyst/photocatalysts, which will be a great impetus to optimize new catalytic transformations.展开更多
Structure-activity relationship (SAR) is the key problem of nanoscience,thus to fabricate novel and well-defined nanostructure will provide a new insight on catalyst preparation method.Highly active and low cost elect...Structure-activity relationship (SAR) is the key problem of nanoscience,thus to fabricate novel and well-defined nanostructure will provide a new insight on catalyst preparation method.Highly active and low cost electrocatalysts for oxygen evolution reaction (OER) are of great importance for future renewable energy conversion and storage.Herein,NiFe-based layered double hydroxides with laminar structure (NFLS) were successfully fabricated via a one-step hydrothermal approach by using sodium dodecyl sulfate as surfactant.The as-fabricated NFLS showed a well-defined periodic layered-stacking geometry with a scale down to 1-nm.Benefitting from the unique structure,NFLS exhibited an excellent catalytic activity towards OER with current densities of 10 mA·cm^-2 at overpotential of 197 mV.The synergistic effect of Ni and Fe plays a key role in electrode reactions.The present work provides a new insight to improve the OER performance by rational design of electrocatalysts with unique structures.展开更多
Ultrathin flat optics allow control of light at the subwavelength scale that is unmatched by traditional refractive optics.To approach the atomically thin limit,the use of 2D materials is an attractive possibility due...Ultrathin flat optics allow control of light at the subwavelength scale that is unmatched by traditional refractive optics.To approach the atomically thin limit,the use of 2D materials is an attractive possibility due to their high refractive indices.However,achievement of diffraction-limited focusing and imaging is challenged by their thickness-limited spatial resolution and focusing efficiency.Here we report a universal method to transform 2D monolayers into ultrathin flat lenses.Femtosecond laser direct writing was applied to generate local scattering media inside a monolayer,which overcomes the longstanding challenge of obtaining sufficient phase or amplitude modulation in atomically thin 2D materials.We achieved highly efficient 3D focusing with subwavelength resolution and diffractionlimited imaging.The high focusing performance even allows diffraction-limited imaging at different focal positions with varying magnifications.Our work paves the way for downscaling of optical devices using 2D materials and reports an unprecedented approach for fabricating ultrathin imaging devices.展开更多
Ultrathin metalorganic framework (MOF) nanosheets are attracting great interest in catalysis due to their unique and intriguing two-dime nsional (2D) features. Although many progresses have been achieved, it is still ...Ultrathin metalorganic framework (MOF) nanosheets are attracting great interest in catalysis due to their unique and intriguing two-dime nsional (2D) features. Although many progresses have been achieved, it is still highly desirable to develop novel strategies for controllable synthesis of the well-defined ultrathin MOF nanosheets. Herein we report a polyvinylpyrrolidone (PVP)-assisted route to synthesize the ultrathin Ni-MOF nanosheets characteristic of 1.5 nm in thickness, in which PVP is reacted with 2-aminoterephthalic acid (H2BDC-NH2) via formation of C=N bon d, followed by coord inatio n with Ni2+ io ns to form the ultrathi n MOF n anosheets. Impressively, when used in the Kno eve nagel condensation reactions of propane dinitrile with different aldehydes, ultrathin Ni-MOF nanosheets display the significantly enhanced catalytic activity and good stability in respect with the bulk Ni-MOF, mainly owing to the exposed active sites as well as facile mass transfer and diffusion of substrates and products.展开更多
Considering the high safety,low-cost and high capacity,aqueous zinc ion batteries have been a potential candidate for energy storage ensuring smooth electricity supply.Herein,we have synthesized inverse opal manganese...Considering the high safety,low-cost and high capacity,aqueous zinc ion batteries have been a potential candidate for energy storage ensuring smooth electricity supply.Herein,we have synthesized inverse opal manganese dioxide constructed by few-layered ultrathin nanosheets by a solution template method at mild temperature.The ultrathin nanosheets with the thickness as small as 1 nm are well separated without obvious aggregation.Used as cathode material for aqueous zinc ion batteries,the few-layered ultrathin nanosheets combined with the inverse opal structure guarantee excellent performance.A high specific discharge capacity of 262.9 mAh·g^-1 is retained for the 100th cycle at a current density of 300 mA·g^-1 with a high capacity retention of 95.6%.A high specific discharge capacity of 121 mAh·g^-1 at a high current density of 2,000 mA·g^-1 is achieved even after 5,000 long-term cycles.The ex-situ X-ray diffraction (XRD) patterns,selected-area electron diffraction (SAED) patterns and high-resolution transmission electron microscopy (HRTEM) results demonstrate that the discharge/charge processes involve the reversible formation of zinc sulfate hydroxide hydrate on the cathode while in-plane crystal structure of the layered bimessite MnO2 could be maintained.This unique structured MnO2 is a promising candidate as cathode material for high capacity,high rate capability and long-term aqueous zinc-ion batteries.展开更多
Ultrathin graphitic carbon nitride nanoplatelets （UGCNPs） are synthesized by a facile manner via an efficient and eco-friendly ball milling approach. The obtained UGCNPs are 2-6 nm in size and 0.35-0.7 nm in thickne...Ultrathin graphitic carbon nitride nanoplatelets （UGCNPs） are synthesized by a facile manner via an efficient and eco-friendly ball milling approach. The obtained UGCNPs are 2-6 nm in size and 0.35-0.7 nm in thickness, with improved specific surface area over that of bulk graphitic carbon nitride. Photochemical experiments show that the UGCNPs are highly active in visible-light water splitting, with a hydrogen evolution rate of 1,365 μmol·h^-1·g^-1, which is 13.7-fold greater than that of their bulk counterparts. The notable improvement in the hydrogen evolution rate observed with UGCNPs under visible light is due to the synergistic effects derived from the increased specific surface area, reduced thickness, and a negative shift in the conduction band concomitant with the exfoliation of bulk graphitic carbon nitride into UGCNPs. In addition to metal- free visible-light-driven photocatalytic hydrogen production, the UGCNPs find attractive applications in biomedical imaging and optoelectronics because of their superior luminescence characteristics.展开更多
The oxygen evolution reaction （OER） is a pivotal process for water-splitting and many other energy technologies involving oxygen electrodes. Herein, a new synthesis strategy is proposed to prepare OER catalysts base...The oxygen evolution reaction （OER） is a pivotal process for water-splitting and many other energy technologies involving oxygen electrodes. Herein, a new synthesis strategy is proposed to prepare OER catalysts based on a simple yet flexible in situ decomposition of Co-based acetate hydroxide metal-organic frameworks （MOFs）. This process allows straightforward fabrication of various 2D hydroxide ultrathin nanosheets （UNSs） with excellent component controllability. The as-obtained Co-based hydroxide UNSs demonstrate superior catalytic activity for the OER due to the exposure of numerous active sites. In particular, the CoNi hydroxide UNSs exhibit low overpotentials （r/） of 324 and 372 mV at current densities of 10 and 100 mA-cm-2, respectively; a large turnover frequency （TOF） of 0.16 s-~ at T/= 380 mV; and a small Tafel slope of 33 mV.dec-~ in an alkaline environment. Importantly, these values are superior to those of the state-of-the- art IrO2 commercial electrocatalyst. This facile strategy enables the exploration of more efficient and economic OER electrocatalysts with various constituents and opens a promising avenue for large-scale fabrication of functional nanocatalysts for use in clean ener~：v technologies.展开更多
Two-dimensional mesoporous ultrathin Cd0.5Zn0.5S nanosheets with a thickness of~1.5 nm were fabricated using a multistep chemical transformation strategy involving inorganic–organic hybrid ZnS-ethylenediamine(denoted...Two-dimensional mesoporous ultrathin Cd0.5Zn0.5S nanosheets with a thickness of~1.5 nm were fabricated using a multistep chemical transformation strategy involving inorganic–organic hybrid ZnS-ethylenediamine(denoted as ZnS(en)0.5)as a hard template.Inorganic–organic hybrid ZnS(en)0.5,Cd0.5Zn0.5S(en)x,and Cd0.5Zn0.5S nanosheets were sequentially fabricated,and their transformation processes were analyzed in detail.The fabricated Cd0.5Zn0.5S nanosheets exhibited high photocatalytic hydrogen evolution reaction activity in the presence of a sacrificial agent.The Cd0.5Zn0.5S nanosheets exhibited remarkably high H2 production activity of~1395μmol∙h^−1∙g^−1 in pure water with no co-catalyst,which is the highest value reported thus far for bare photocatalysts,to the best of our knowledge.The high activity of these nanosheets is attributed to their distinct nanostructure(e.g.,short transfer distance of photoinduced charge carriers,large number of unsaturated surface atoms,and large surface area).Moreover,ternary NiCo2S4 nanoparticles were employed to facilitate the charge separation and enhance the surface kinetics of H2 evolution.The H2 production rate reached~62.2 and~2436μmol∙h^−1∙g^−1 in triethanolamine and pure water,respectively,over the NiCo2S4/Cd0.5Zn0.5S heterojunctions.The result indicated that the Schottky junction was critical to the enhanced activity.The proposed method can be used for fabricating other highly efficient CdZnS-based photocatalysts for solar-energy conversion or other applications.展开更多
Graphene oxide （GO） ultrathin flat lenses have provided a new and viable solution to achieve high resolution, high efficiency, ultra-light weight, integratable and flexible optical systems. Current GO lenses are des...Graphene oxide （GO） ultrathin flat lenses have provided a new and viable solution to achieve high resolution, high efficiency, ultra-light weight, integratable and flexible optical systems. Current GO lenses are designed based on the Fresnel diffraction model, which uses a paraxial approximation for low numerical aperture （NA） focusing process. Herein we develop a lens design method based on the Rayleigh-Sommerfeld （RS） diffraction theory that is able to unambiguously determine the radii of each ring without the optimization process for the first time. More importantly, the RS design method is able to accurately design GO lenses with arbitrary NA and focal length. Our design is experimentally confirmed by fabricating high NA GO lenses with both short and long focal lengths. Compared with the conventional Fresnel design methods, the differences in ring positions and the resulted focal length are up to 13.9% and 9.1%, respectively. Our method can be further applied to design high performance flat lenses of arbitrary materials given the NA and focal length requirements, including metasurfaces or other two-dimensional materials.展开更多
The dimensional confinement endows ultrathin nanosheets with unique physical and chemical properties, which have been widely studied for the purpose of developing active electrocatalysts for water splitting. Ultrathin...The dimensional confinement endows ultrathin nanosheets with unique physical and chemical properties, which have been widely studied for the purpose of developing active electrocatalysts for water splitting. Ultrathin nanosheets are generally synthesized by chemical vapor deposition, exfoliation, or surfactant- assisted synthesis, which either require special equipment and reaction conditions, or is limited by the low yields and the difficulty in controlling the lateral size and structure of the nanosheets. In addition, achieving a high loading of ultrathin nanosheets on the electrodes without compromising their catalytic activity still remains a challenge. Herein, we report a simple electrodeposition method for preparing C0304 and Co（OH）2 ultrathin nanosheet arrays （UNA） without using templates or surfactants. The obtained arrays exhibit high activity for oxygen and hydrogen evolution reactions, in both alkaline and neutral media. The electrolyzer based on Co304 and Co（OH）2 UNA shows superior activity and stability than that based on IrO2 and Pt/C, which demonstrates the potential of the present electrodeposition method for developing active and stable electrocatalysts for water splitting.展开更多
BACKGROUND Conventionally, the low luminous intensity, low image resolution, and difficulty in operation have been reported with the ultrathin endoscope. However, it has markedly advanced recently. The improvement of ...BACKGROUND Conventionally, the low luminous intensity, low image resolution, and difficulty in operation have been reported with the ultrathin endoscope. However, it has markedly advanced recently. The improvement of the diagnostic ability is expected.AIM To compare the early gastric cancer diagnostic ability of an ultrathin endoscope loaded with a laser light source and that of the conventional endoscope.METHODS The target subjects were 375 consecutive patients who underwent endoscopy at our hospital for post-endoscopic submucosal dissection follow-up of gastric cancer from January to August 2018. During endoscopy, the ultrathin endoscope was used in 140 patients(37.3%), and the conventional endoscope was used in235 patients(62.7%). Patient background was adjusted using the propensity score matching method, and gastric cancer detection ability was evaluated in the two groups.RESULTS The gastric cancer detection rate was 7.8% in the ultrathin endoscope group and7.0% in the conventional endoscope group, and the mean intragastric observation time was 4.1 ± 1.7 min in the ultrathin endoscope group and 4.1 ± 1.9 min in the conventional endoscope group, showing no significant differences between the groups. Moreover, the biopsy implementation rate was 31.8% in the ultrathin endoscope group and 41.1% in the conventional endoscope group, and the biopsy prediction rate was 17.9% and 13.2%, respectively, showing no significant differences between the groups.CONCLUSION The gastric cancer diagnostic ability of the ultrathin endoscope loaded with a laser light source was comparable to that of the conventional endoscope. The observation time was also comparable. Thus, endoscopy using the ultrathin endoscope loaded with the laser light source would be the first option in screening examinations of gastric cancer due to its low invasion.展开更多
The photocatalytic reduction of CO2 to energy-rich hydrocarbon fuels is a promising and sustainable method of addressing global warming and the imminent energy crisis concomitantly. However, a vast majority of the exi...The photocatalytic reduction of CO2 to energy-rich hydrocarbon fuels is a promising and sustainable method of addressing global warming and the imminent energy crisis concomitantly. However, a vast majority of the existing photocatalysts are only capable of harnessing ultraviolet （UV） or/and visible light （Vis）, whereas the near-infrared （NIR） region still remains unexplored. In this study, carbon quantum dots （CQDs）-decorated ultrathin BizWO6 nanosheets （UBW） were demonstrated to be an efficient photocatalyst for CO2 photoreduction over the Vis-NIR broad spectrum. It is noteworthy that the synthesis procedure of the CQDs/UBW hybrid nanocomposites was highly facile, involving a one-pot hexadecyltrimethylammonium bromide （CTAB）-assisted hydrothermal process. Under visible light irradiation, the optimized 1CQDsAJBW （1 wt.% CQD content） exhibited a remarkable 9.5-fold and 3.1-fold enhancement of CH4 production over pristine Bi2WO6 nanoplatelets （PBW） and bare UBW, respectively. More importantly, the photocatalytic responsiveness of CQDs/UBW was successfully extended to the NIR region, which was achieved without involving any rare earth or noble metals. The realization of NIR-driven CO2 reduction could be attributed to the synergistic effects of （i） the ultrathin nanostructures and highly exposed {001} active facets of UBW, （ii） the excellent spectral coupling of UBW and CQDs, where UBW could be excited by the up-converted photoluminescence of CQDs, and （iii） the electron-withdrawing nature of the CQDs to trap the photogenerated electrons and retard the recombination of charge carriers.展开更多
The controllable construction of two-dimensional(2D)metal–organic framework(MOF)nanosheets with favorable electrochemical performances is greatly challenging for energy storage.Here,we design an in situ induced growt...The controllable construction of two-dimensional(2D)metal–organic framework(MOF)nanosheets with favorable electrochemical performances is greatly challenging for energy storage.Here,we design an in situ induced growth strategy to construct the ultrathin carboxylated carbon nanotubes(C-CNTs)interpenetrated nickel MOF(Ni-MOF/C-CNTs)nanosheets.The deliberate thickness and specific surface area of novel 2D hybrid nanosheets can be effectively tuned via finely controlling C-CNTs involvement.Due to the unique microstructure,the integrated 2D hybrid nanosheets are endowed with plentiful electroactive sites to promote the electrochemical performances greatly.The prepared Ni-MOF/C-CNTs nanosheets exhibit superior specific capacity of 680 C g^−1 at 1 A g^−1 and good capacity retention.The assembled hybrid device demonstrated the maximum energy density of 44.4 Wh kg^−1 at a power density of 440 W kg^−1.Our novel strategy to construct ultrathin 2D MOF with unique properties can be extended to synthesize various MOF-based functional materials for diverse applications.展开更多
基金National Natural Science Foundation of China,Grant/Award Numbers:21805162,21825501,and U1801257。
文摘Smart energy storage has revolutionized portable electronics and electrical vehicles.The current smart energy storage devices have penetrated into flexible electronic markets at an unprecedented rate.Flexible batteries are key power sources to enable vast flexible devices,which put forward additional requirements,such as bendable,twistable,stretchable,and ultrathin,to adapt mechanical deformation under the working conditions.This review summarizes the recent advances in construction and configuration of flexible batteries and discusses the general metrics to benchmark various flexible batteries with different materials and chemistries.Moreover,we present advanced prototype flexible batteries developed by some companies to afford general envision of the technological status.Lastly,the critical points are summarized in the development of flexible batteries and remaining challenges are also presented for the future design of flexible batteries in practical perspectives.
基金This work was supported by the State Key Project of Fundamental Research for Nanoscience and Nanotechnology （Nos. 2011CB932401, 2011CBA00500, and 2012CB224802）, and the National Natural Science Foundation of China （Nos. 21221062, 21131004, and 21390393）. The authors thank Electron Microscopy Laboratory of Peking University for the help with HRTEM analysis.
文摘Hexagonal ultrathin WO3 nano-ribbons （HUWNRs） of subnanometer thicknesses, 2-5 nm widths, and lengths of up to several micrometers were prepared by a solvothermal method. The as-prepared HUWNRs grow along the [001] direction, and the main exposed facet is the （720） crystal plane. The HUWNRs exhibit good electrochemical performance as an anode material in lithium ion batteries because of their unique structure. It is believed that these unique materials may be applied in many fields.
基金Acknowledgements This work was supported by the National Basic Research Program of China （973 Program） （No. 2014CB932103）, the National Natural Science Foundation of China （Nos. 21301016 and 21473013）, the Beijing Municipal Natural Science Foundation （No. 2152016）, and the Fundamental Research Funds for the Central Universities.
文摘The assembly of thin films （TFs） having long-lasting luminescence can be expected to play an important role in the development of new-generation smart sensors, anti-counterfeiting materials, and information-encryption systems. However, such films are limited compared with their powder and solution counterparts. In this study, by exploiting the self-organization of phosphors in the two-dimensional （2D） galleries between clay nanosheets, we developed a method for the ordered assembly of long-afterglow TFs by utilizing a hydrogen-bonding layer-by-layer （LBL） process. Compared with the pristine powder, the TFs exhibit high polarization and up-conversion room-temperature phosphorescence （RTP）, as well as enhanced quantum yields and luminescence lifetimes, allowing them to be used as room-temperature phosphorescent sensors for humidity and oxygen. Moreover, modified clay-based hybrids with multicolor RTP can serve as anti-counterfeiting marks and triple-mode 2D barcode displays. We anticipate that the LBL assembly process can be extended to the fabrication of other inorganic--organic room-temperature phosphorescent hybrids with smart luminescent sensor and antiforgery applications.
基金financially supported by the National Natural Science Foundation of China (51772255)Hunan Natural Science Foundation (2016JJ3123)+2 种基金the National Key Research and Development Program of China (2016YFB0100201)the start-up supports from Peking UniversityYoung Thousand Talented Program
文摘Photocatalytic hydrogen production represents a promising strategy for clean, sustainable, and environmentfriendly energy supply. Up to now, great efforts have been devoted to designing the photocatalysts with noble metal as co-catalyst for visible-light-driven hydrogen evolution, while more efficient photocatalytic systems are still a major challenge. Herein, we report a facile strategy for synthesizing faceto-face ultrathin Pd nanosheets-amorphous carbon nitride(Pd NSs-ACN) structure with large contacting interface and short electronic transmission pathway, which can work as an efficient photocatalyst for hydrogen production. The synthesis starts with the growth of ultrathin Pd NSs, followed by assembly with the visible-light-response ACN through a simple stirring and annealing procedure. The resultant two dimensional face-to-face structures deliver an average hydrogen generation rate of 1.45 mmol h-1g-1 at a temperature of 25℃,almost 2.6 times higher than that of Pd Nps-ACN with particle-to-face structural feature. The efficient photocatalytic activity is ascribed to the formation of high-density of active sites between ultrafine face-to-face contacted Pd NSs and the ACN, which cooperate more synergistically towards photocatalytic hydrogen production. The face-to-face engineered Pd NSs-ACN hybrids also offer a good stability revealed by photocatalytic hydrogen production measurements. The extraordinary performance highlights a powerful engineering model for designing other face-to-face contacting co-catalyst/photocatalysts, which will be a great impetus to optimize new catalytic transformations.
基金the National Natural Science Foundation of China (Nos.21431003 and 21521091)the National Key Technology R&D Program of China (No.2016YFA0202801).
文摘Structure-activity relationship (SAR) is the key problem of nanoscience,thus to fabricate novel and well-defined nanostructure will provide a new insight on catalyst preparation method.Highly active and low cost electrocatalysts for oxygen evolution reaction (OER) are of great importance for future renewable energy conversion and storage.Herein,NiFe-based layered double hydroxides with laminar structure (NFLS) were successfully fabricated via a one-step hydrothermal approach by using sodium dodecyl sulfate as surfactant.The as-fabricated NFLS showed a well-defined periodic layered-stacking geometry with a scale down to 1-nm.Benefitting from the unique structure,NFLS exhibited an excellent catalytic activity towards OER with current densities of 10 mA·cm^-2 at overpotential of 197 mV.The synergistic effect of Ni and Fe plays a key role in electrode reactions.The present work provides a new insight to improve the OER performance by rational design of electrocatalysts with unique structures.
基金support from the Australian Research Council through the Discovery Project scheme(DP190103186)the Industrial Transformation Training Centres scheme(Grant No.IC180100005)+6 种基金support from the Australian Postgraduate Award(APA)and international postgraduate research scholarship(IPRS)support from the National Key Research&Development Program(No.2016YFA0201902)aShenzhen Nanshan District Pilotage Team Program(LHTD20170006)support from the Australian Research Council(FT150100450 and CE170100039)financial support from the A*STAR Pharos Program(grant number 1527000014,with project number R-263-000-B91-305)the National Research Foundation,Prime Minister’s Office,Singapore under its Competitive Research Program(CRP award NRF CRP22-2019-0006)the support of the National Research Foundation-Competitive Research Program(NRF-CRP21–2018–007).
文摘Ultrathin flat optics allow control of light at the subwavelength scale that is unmatched by traditional refractive optics.To approach the atomically thin limit,the use of 2D materials is an attractive possibility due to their high refractive indices.However,achievement of diffraction-limited focusing and imaging is challenged by their thickness-limited spatial resolution and focusing efficiency.Here we report a universal method to transform 2D monolayers into ultrathin flat lenses.Femtosecond laser direct writing was applied to generate local scattering media inside a monolayer,which overcomes the longstanding challenge of obtaining sufficient phase or amplitude modulation in atomically thin 2D materials.We achieved highly efficient 3D focusing with subwavelength resolution and diffractionlimited imaging.The high focusing performance even allows diffraction-limited imaging at different focal positions with varying magnifications.Our work paves the way for downscaling of optical devices using 2D materials and reports an unprecedented approach for fabricating ultrathin imaging devices.
基金the National Key Basic Research Program of China (Nos. 2014CB931801 and 2016YFA0200700, Z. Y. T.)National Natural Science Foundation of China (Nos. 21890381, 21721002 and 21475029, Z. Y. T.+4 种基金21722102, 51672053 and 21303029, G. D. L.)Beijing Natural Science Foundation (No. 2182087, G. D. L.)Frontier Science Key Project of Chinese Academy of Sciences (No. QYZDJ-SSW-SLH038,Z. Y. T.)K. C. Wong Education Foundation (Z. Y T.)Youth Innovation Promotion Association CAS (No. 2016036, G. D. L.).
文摘Ultrathin metalorganic framework (MOF) nanosheets are attracting great interest in catalysis due to their unique and intriguing two-dime nsional (2D) features. Although many progresses have been achieved, it is still highly desirable to develop novel strategies for controllable synthesis of the well-defined ultrathin MOF nanosheets. Herein we report a polyvinylpyrrolidone (PVP)-assisted route to synthesize the ultrathin Ni-MOF nanosheets characteristic of 1.5 nm in thickness, in which PVP is reacted with 2-aminoterephthalic acid (H2BDC-NH2) via formation of C=N bon d, followed by coord inatio n with Ni2+ io ns to form the ultrathi n MOF n anosheets. Impressively, when used in the Kno eve nagel condensation reactions of propane dinitrile with different aldehydes, ultrathin Ni-MOF nanosheets display the significantly enhanced catalytic activity and good stability in respect with the bulk Ni-MOF, mainly owing to the exposed active sites as well as facile mass transfer and diffusion of substrates and products.
文摘Considering the high safety,low-cost and high capacity,aqueous zinc ion batteries have been a potential candidate for energy storage ensuring smooth electricity supply.Herein,we have synthesized inverse opal manganese dioxide constructed by few-layered ultrathin nanosheets by a solution template method at mild temperature.The ultrathin nanosheets with the thickness as small as 1 nm are well separated without obvious aggregation.Used as cathode material for aqueous zinc ion batteries,the few-layered ultrathin nanosheets combined with the inverse opal structure guarantee excellent performance.A high specific discharge capacity of 262.9 mAh·g^-1 is retained for the 100th cycle at a current density of 300 mA·g^-1 with a high capacity retention of 95.6%.A high specific discharge capacity of 121 mAh·g^-1 at a high current density of 2,000 mA·g^-1 is achieved even after 5,000 long-term cycles.The ex-situ X-ray diffraction (XRD) patterns,selected-area electron diffraction (SAED) patterns and high-resolution transmission electron microscopy (HRTEM) results demonstrate that the discharge/charge processes involve the reversible formation of zinc sulfate hydroxide hydrate on the cathode while in-plane crystal structure of the layered bimessite MnO2 could be maintained.This unique structured MnO2 is a promising candidate as cathode material for high capacity,high rate capability and long-term aqueous zinc-ion batteries.
基金This project is sponsored by NSFC （Nos. 21325415, 21174019, 21301018, 51161120361）, National Basic Research Program of China （2011CB013000）, Basic Research Foundation of Beijing Institute of Technology （20121942008）, Fok Ying Tong Education Foundation （No. 131043）, the 111 Project B07012, Beijing Natural Science Foundation （2152028） and the Beijing Key Laboratory for Chemical Power Source and Green Catalysis under the contract no. 2013CX02031.
文摘Ultrathin graphitic carbon nitride nanoplatelets （UGCNPs） are synthesized by a facile manner via an efficient and eco-friendly ball milling approach. The obtained UGCNPs are 2-6 nm in size and 0.35-0.7 nm in thickness, with improved specific surface area over that of bulk graphitic carbon nitride. Photochemical experiments show that the UGCNPs are highly active in visible-light water splitting, with a hydrogen evolution rate of 1,365 μmol·h^-1·g^-1, which is 13.7-fold greater than that of their bulk counterparts. The notable improvement in the hydrogen evolution rate observed with UGCNPs under visible light is due to the synergistic effects derived from the increased specific surface area, reduced thickness, and a negative shift in the conduction band concomitant with the exfoliation of bulk graphitic carbon nitride into UGCNPs. In addition to metal- free visible-light-driven photocatalytic hydrogen production, the UGCNPs find attractive applications in biomedical imaging and optoelectronics because of their superior luminescence characteristics.
文摘The oxygen evolution reaction （OER） is a pivotal process for water-splitting and many other energy technologies involving oxygen electrodes. Herein, a new synthesis strategy is proposed to prepare OER catalysts based on a simple yet flexible in situ decomposition of Co-based acetate hydroxide metal-organic frameworks （MOFs）. This process allows straightforward fabrication of various 2D hydroxide ultrathin nanosheets （UNSs） with excellent component controllability. The as-obtained Co-based hydroxide UNSs demonstrate superior catalytic activity for the OER due to the exposure of numerous active sites. In particular, the CoNi hydroxide UNSs exhibit low overpotentials （r/） of 324 and 372 mV at current densities of 10 and 100 mA-cm-2, respectively; a large turnover frequency （TOF） of 0.16 s-~ at T/= 380 mV; and a small Tafel slope of 33 mV.dec-~ in an alkaline environment. Importantly, these values are superior to those of the state-of-the- art IrO2 commercial electrocatalyst. This facile strategy enables the exploration of more efficient and economic OER electrocatalysts with various constituents and opens a promising avenue for large-scale fabrication of functional nanocatalysts for use in clean ener~：v technologies.
文摘Two-dimensional mesoporous ultrathin Cd0.5Zn0.5S nanosheets with a thickness of~1.5 nm were fabricated using a multistep chemical transformation strategy involving inorganic–organic hybrid ZnS-ethylenediamine(denoted as ZnS(en)0.5)as a hard template.Inorganic–organic hybrid ZnS(en)0.5,Cd0.5Zn0.5S(en)x,and Cd0.5Zn0.5S nanosheets were sequentially fabricated,and their transformation processes were analyzed in detail.The fabricated Cd0.5Zn0.5S nanosheets exhibited high photocatalytic hydrogen evolution reaction activity in the presence of a sacrificial agent.The Cd0.5Zn0.5S nanosheets exhibited remarkably high H2 production activity of~1395μmol∙h^−1∙g^−1 in pure water with no co-catalyst,which is the highest value reported thus far for bare photocatalysts,to the best of our knowledge.The high activity of these nanosheets is attributed to their distinct nanostructure(e.g.,short transfer distance of photoinduced charge carriers,large number of unsaturated surface atoms,and large surface area).Moreover,ternary NiCo2S4 nanoparticles were employed to facilitate the charge separation and enhance the surface kinetics of H2 evolution.The H2 production rate reached~62.2 and~2436μmol∙h^−1∙g^−1 in triethanolamine and pure water,respectively,over the NiCo2S4/Cd0.5Zn0.5S heterojunctions.The result indicated that the Schottky junction was critical to the enhanced activity.The proposed method can be used for fabricating other highly efficient CdZnS-based photocatalysts for solar-energy conversion or other applications.
文摘Graphene oxide （GO） ultrathin flat lenses have provided a new and viable solution to achieve high resolution, high efficiency, ultra-light weight, integratable and flexible optical systems. Current GO lenses are designed based on the Fresnel diffraction model, which uses a paraxial approximation for low numerical aperture （NA） focusing process. Herein we develop a lens design method based on the Rayleigh-Sommerfeld （RS） diffraction theory that is able to unambiguously determine the radii of each ring without the optimization process for the first time. More importantly, the RS design method is able to accurately design GO lenses with arbitrary NA and focal length. Our design is experimentally confirmed by fabricating high NA GO lenses with both short and long focal lengths. Compared with the conventional Fresnel design methods, the differences in ring positions and the resulted focal length are up to 13.9% and 9.1%, respectively. Our method can be further applied to design high performance flat lenses of arbitrary materials given the NA and focal length requirements, including metasurfaces or other two-dimensional materials.
文摘The dimensional confinement endows ultrathin nanosheets with unique physical and chemical properties, which have been widely studied for the purpose of developing active electrocatalysts for water splitting. Ultrathin nanosheets are generally synthesized by chemical vapor deposition, exfoliation, or surfactant- assisted synthesis, which either require special equipment and reaction conditions, or is limited by the low yields and the difficulty in controlling the lateral size and structure of the nanosheets. In addition, achieving a high loading of ultrathin nanosheets on the electrodes without compromising their catalytic activity still remains a challenge. Herein, we report a simple electrodeposition method for preparing C0304 and Co（OH）2 ultrathin nanosheet arrays （UNA） without using templates or surfactants. The obtained arrays exhibit high activity for oxygen and hydrogen evolution reactions, in both alkaline and neutral media. The electrolyzer based on Co304 and Co（OH）2 UNA shows superior activity and stability than that based on IrO2 and Pt/C, which demonstrates the potential of the present electrodeposition method for developing active and stable electrocatalysts for water splitting.
文摘BACKGROUND Conventionally, the low luminous intensity, low image resolution, and difficulty in operation have been reported with the ultrathin endoscope. However, it has markedly advanced recently. The improvement of the diagnostic ability is expected.AIM To compare the early gastric cancer diagnostic ability of an ultrathin endoscope loaded with a laser light source and that of the conventional endoscope.METHODS The target subjects were 375 consecutive patients who underwent endoscopy at our hospital for post-endoscopic submucosal dissection follow-up of gastric cancer from January to August 2018. During endoscopy, the ultrathin endoscope was used in 140 patients(37.3%), and the conventional endoscope was used in235 patients(62.7%). Patient background was adjusted using the propensity score matching method, and gastric cancer detection ability was evaluated in the two groups.RESULTS The gastric cancer detection rate was 7.8% in the ultrathin endoscope group and7.0% in the conventional endoscope group, and the mean intragastric observation time was 4.1 ± 1.7 min in the ultrathin endoscope group and 4.1 ± 1.9 min in the conventional endoscope group, showing no significant differences between the groups. Moreover, the biopsy implementation rate was 31.8% in the ultrathin endoscope group and 41.1% in the conventional endoscope group, and the biopsy prediction rate was 17.9% and 13.2%, respectively, showing no significant differences between the groups.CONCLUSION The gastric cancer diagnostic ability of the ultrathin endoscope loaded with a laser light source was comparable to that of the conventional endoscope. The observation time was also comparable. Thus, endoscopy using the ultrathin endoscope loaded with the laser light source would be the first option in screening examinations of gastric cancer due to its low invasion.
文摘The photocatalytic reduction of CO2 to energy-rich hydrocarbon fuels is a promising and sustainable method of addressing global warming and the imminent energy crisis concomitantly. However, a vast majority of the existing photocatalysts are only capable of harnessing ultraviolet （UV） or/and visible light （Vis）, whereas the near-infrared （NIR） region still remains unexplored. In this study, carbon quantum dots （CQDs）-decorated ultrathin BizWO6 nanosheets （UBW） were demonstrated to be an efficient photocatalyst for CO2 photoreduction over the Vis-NIR broad spectrum. It is noteworthy that the synthesis procedure of the CQDs/UBW hybrid nanocomposites was highly facile, involving a one-pot hexadecyltrimethylammonium bromide （CTAB）-assisted hydrothermal process. Under visible light irradiation, the optimized 1CQDsAJBW （1 wt.% CQD content） exhibited a remarkable 9.5-fold and 3.1-fold enhancement of CH4 production over pristine Bi2WO6 nanoplatelets （PBW） and bare UBW, respectively. More importantly, the photocatalytic responsiveness of CQDs/UBW was successfully extended to the NIR region, which was achieved without involving any rare earth or noble metals. The realization of NIR-driven CO2 reduction could be attributed to the synergistic effects of （i） the ultrathin nanostructures and highly exposed {001} active facets of UBW, （ii） the excellent spectral coupling of UBW and CQDs, where UBW could be excited by the up-converted photoluminescence of CQDs, and （iii） the electron-withdrawing nature of the CQDs to trap the photogenerated electrons and retard the recombination of charge carriers.
基金supported by National Natural Science Foundation of China(21878062)
文摘The controllable construction of two-dimensional(2D)metal–organic framework(MOF)nanosheets with favorable electrochemical performances is greatly challenging for energy storage.Here,we design an in situ induced growth strategy to construct the ultrathin carboxylated carbon nanotubes(C-CNTs)interpenetrated nickel MOF(Ni-MOF/C-CNTs)nanosheets.The deliberate thickness and specific surface area of novel 2D hybrid nanosheets can be effectively tuned via finely controlling C-CNTs involvement.Due to the unique microstructure,the integrated 2D hybrid nanosheets are endowed with plentiful electroactive sites to promote the electrochemical performances greatly.The prepared Ni-MOF/C-CNTs nanosheets exhibit superior specific capacity of 680 C g^−1 at 1 A g^−1 and good capacity retention.The assembled hybrid device demonstrated the maximum energy density of 44.4 Wh kg^−1 at a power density of 440 W kg^−1.Our novel strategy to construct ultrathin 2D MOF with unique properties can be extended to synthesize various MOF-based functional materials for diverse applications.
