The deficit of organ donors has fueled the need for advances in tissue engineering and regenerative medicine. Microencapsulation in alginate immuno-isolation membranes has been used to treat many disabling metabolic d...The deficit of organ donors has fueled the need for advances in tissue engineering and regenerative medicine. Microencapsulation in alginate immuno-isolation membranes has been used to treat many disabling metabolic disorders, namely, phenylketonuria, kidney failure and diabetes mellitus. Systematic nutrient flux determinations are hindered by the lack of experimental data on alginate-based membrane topography and the pore size thus preventing the full therapeutic potential of the bio-membranes to be reached. In this study, samples of cross-linked alginate membranes were subjected to the following analytical characterization: 1) pore size characterization using atomic force microscopy operated in contact mode to detect and measure pore size;2) differential scanning calorimetry to confirm biopolymer cross-linking;and 3) diffusivity measurements using spectrophotometry and fluorescence microscopy to confirm the presence of through pores and to calculate reflection coefficients. The pore sizes for the pre-clinical standard formulation of 1.5% (w/v) medium viscosity alginate cross-linked with 1.5% CaCl2 and 0.5% (w/v) alginate and chitosan cross-linked with 20% CaCl2 are 5.2 nm ± 0.9 nm and 7.0 nm ± 3.1 nm, respectively. An increase in the glass transition temperatures as a function of cross-linker concentration was observed. Diffusivity values obtained from the inward diffusivity of creatinine into macrocapsules (d = 1000 μm ± 75 μm) and the outward diffusivity of FITC dextrans from macrocapsules (d = 1000 μm ± 75 μm) and microcapsules (d = 40 μm ± 5 μm) were shown to correlate strongly (R2 = 0.9835) with the ratio of solute to pore sizes, confirming the presence of through pores. Reflection coefficients approaching and exceeding unity correlate with the lack of permeability of the membranes to MW markers that are 70 kDa and greater.展开更多
A highly distorted chiral nanographene structure composed of triple corannulene-fused[5]helicenes is prepared with the help of the Heck reaction and oxidative photocyclization with an overall isolated yield of 28%.The...A highly distorted chiral nanographene structure composed of triple corannulene-fused[5]helicenes is prepared with the help of the Heck reaction and oxidative photocyclization with an overall isolated yield of 28%.The complex three-dimensional(3D)structure of the bowl-helix hybrid nanostructure is studied by a combination of noncontact atomic force microscopy(AFM)and scanning tunneling microscopy(STM)on the Cu(111)surface,density functional theory calculations,AFM/STM simulations,and high-performance liquid chromatography-electronic circular dichroism analysis.This examination reveals a molecular structure in which the three bowl-shaped corannulene bladesd position themselves in a C3-symmetric fashion around a highly twisted triphenylene core.The molecule appears to be shaped like a propeller in which the concave side of the bowls face away from the connected[5]helicene motif.The chirality of the nanostructure is confirmed by the direct visualization of both MMM and PPP enantiomers at the single-molecule level by scanning probe microscopies.These results underline that submolecular resolution imaging by AFM/STM is a powerful real-space tool for the stereochemical characterization of 3D curved chiral nanographene structures.展开更多
The Langmuir-Blodgett (LB) technique is now widely used in construction of monolayeror multilayer of organic molecular thin film, of which the structures are controlled on themolecular level. Ths ultrathin organic mol...The Langmuir-Blodgett (LB) technique is now widely used in construction of monolayeror multilayer of organic molecular thin film, of which the structures are controlled on themolecular level. Ths ultrathin organic molecular film has been extensively studied andapplied due to its special physical and chemical properties. The detailed investigation of展开更多
To improve the scanning speed of an atomic force microscopy(AFM),a smooth scanning pattern is elaborately devised via trajectory shaping in this paper,so as to achieve fast imaging without hardware modification.Specif...To improve the scanning speed of an atomic force microscopy(AFM),a smooth scanning pattern is elaborately devised via trajectory shaping in this paper,so as to achieve fast imaging without hardware modification.Specifically,in the proposed scanning method,the piezoelectric actuator tracks a well-designed smooth periodic signal in x-direction,and simultaneously tracks a step signal in y-direction.The advantage of the proposed method is that it does not require additional data reprocessing to construct the morphology of the sample surface,while significantly increasing the scanning bandwidth restricted by the raster scanning method.Particularly,to directly utilize the height data collected by scanning to produce the sample morphology,the forward process in the common raster scanning mode is retained in the proposed method,the tracking signal in the forward process is thus set to a ramp function in x-direction.In addition,to ensure the continuity and smoothness of the entire tracking signal in x-direction,a segment of a sine curve is uniquely determined as the backward tracking signal by position and acceleration constraints,so as to ensure that the forward and backward curves are continuous and acceleration-continuous at the intersection point.Moreover,the frequency spectrum analysis of the designed smooth signal is carried out to exhibit the depressed amplitudes of high-frequency components,which demonstrates that the proposed method is able to reduce the resonance in AFM high-speed scanning,so as to improve the capacity of rapidly generating high-quality images.Finally,convincing comparison experiments are implemented to verify the imaging performance of the designed scanning algorithm.展开更多
Comprehensive Summary Kagome lattices have garnered significant attention due to their promising applications in catalysis,electronics,and magnetics.Although many efforts have been paid to the design and synthesis of ...Comprehensive Summary Kagome lattices have garnered significant attention due to their promising applications in catalysis,electronics,and magnetics.Although many efforts have been paid to the design and synthesis of Kagome lattices,there is a limited focus on constructing this lattice by multiple interaction forces.In this work,we employ 2,7-dibromo-carbazole as precursors to successfully fabricate the two-dimensional self-assembly Kagome lattices stabled by multiple interaction forces on Au(111)substrate.Using low-temperature scanning tunneling microscopy,non-contact atomic force microscopy and density functional theory calculation,we visualize and identify the four interaction forces within Kagome lattices:Au—N coordination bonds,Au—H hydrogen bonds,Br—Br halogen bonds,and Br—H hydrogen bonds,respectively.This study provides a basic understanding for designing and constructing more complex Kagome lattices.展开更多
The localized micro-galvanic corrosion process and the kinetic information of Mg-(7,9)Al-1Fe-x Nd alloys were investigated by in situ observation under electrochemical control and in situ atomic force microscopy(AFM)i...The localized micro-galvanic corrosion process and the kinetic information of Mg-(7,9)Al-1Fe-x Nd alloys were investigated by in situ observation under electrochemical control and in situ atomic force microscopy(AFM)in an electrolyte environment.The results revealed that the formation of the Nd-rich phase in alloys resulted in a decrease in the Volta potential difference from~400 m V(AlFe3/α-Mg)to~220 mV(Nd-rich/α-Mg),reducing the corrosion products around the cathodic phase and corrosion current density of the microscale area.The addition of Nd significantly improved the corrosion resistance,mainly due to the suppression of the micro-galvanic corrosion between the second phases and substrate.Finally,the corrosion mechanism of Mg-(7,9)Al-1Fe-x Nd alloys was discussed based on in situ observations and electrochemical results.展开更多
Atomic force microscopy (AFM) was used to locate CD20 molecules on the surface of lymphoma Raji cells. Rituximab (a monoclonal antibody against CD20) molecules were linked onto the AFM tip via a polyethylene glycol (P...Atomic force microscopy (AFM) was used to locate CD20 molecules on the surface of lymphoma Raji cells. Rituximab (a monoclonal antibody against CD20) molecules were linked onto the AFM tip via a polyethylene glycol (PEG) linker. Raji cells were adsorbed onto glass slides coated with poly-L-lysine. First, the CD20 distribution in a local area of the cell surface was visualized using the AFM lift scan mode. Second, 16 × 16 force curves were obtained from the same cell area to construct the CD20-rituximab binding force map. Finally, free rituximab was added to block the CD20 molecules on the cell surface and the lift phase image and CD20-rituximab force map were obtained again. The experimental results indicated that when the lift height was greater than the length of the PEG linker, no recognition sites were observed in the lift phase image. However, as the lift height decreased to the length of the PEG linker, some recognition sites were observed in the lift phase image and these sites were generally consistent with the pixels in the force map. After blocking, both the recognition sites in the lift phase image and the gray pixels in the binding force map decreased markedly. These results can improve our understanding of the distribution of protein molecules on the cell surface and facilitate further investigations into cellular functions.展开更多
We investigated the orientations of interface dipole moments of individual non-planar titanyl phthalocyanine(TiOPc)molecules on Cu(111)and Cu(100)substrates using scanning tunneling microscope(STM)and noncontact atomi...We investigated the orientations of interface dipole moments of individual non-planar titanyl phthalocyanine(TiOPc)molecules on Cu(111)and Cu(100)substrates using scanning tunneling microscope(STM)and noncontact atomic force microscope(NC-AFM).The dipole moment orientations corresponding to two different configurations of individual TiOPc molecules were determined unambiguously.The correlation between the actual molecular structures and the corresponding STM topographies is proposed based on the sub-molecular resolution imaging and local contact potential difference(LCPD)measurements.Comparing with the pristine substrate,the LCPD shift due to the adsorption of non-planar molecule is dependent on the permanent molecular dipole,the charge transfer between the surface and the molecule,and the molecular configurations.This work would shed light on tailoring interfacial electronic properties and controlling local physical properties via polar molecule adsorption.展开更多
The rational design of efficient artificial photosynthetic components requires thorough understandings towards(photo)electrochemical properties and kinetic processes at the solid/liquid interface.Electrochemical scann...The rational design of efficient artificial photosynthetic components requires thorough understandings towards(photo)electrochemical properties and kinetic processes at the solid/liquid interface.Electrochemical scanning probe microscopy(EC-SPM),which enables the high-spatial resolution imaging in an electrolyte environment,becomes an indispensable experimental technique for operando studies of(photo)electrochemistry.This review summarizes the latest results of relevant ECSPM techniques to study the interfacial properties of electrocatalysts and photoelectrodes.Covered methods include atomic force microscopy,Kelvin probe force microscopy,conductive atomic force microscopy,scanning tunneling microscopy,scanning electrochemical microscopy,and other advanced SPM-based operando techniques.Finally,we offer some perspectives on the future outlook in this fascinating research area.展开更多
文摘The deficit of organ donors has fueled the need for advances in tissue engineering and regenerative medicine. Microencapsulation in alginate immuno-isolation membranes has been used to treat many disabling metabolic disorders, namely, phenylketonuria, kidney failure and diabetes mellitus. Systematic nutrient flux determinations are hindered by the lack of experimental data on alginate-based membrane topography and the pore size thus preventing the full therapeutic potential of the bio-membranes to be reached. In this study, samples of cross-linked alginate membranes were subjected to the following analytical characterization: 1) pore size characterization using atomic force microscopy operated in contact mode to detect and measure pore size;2) differential scanning calorimetry to confirm biopolymer cross-linking;and 3) diffusivity measurements using spectrophotometry and fluorescence microscopy to confirm the presence of through pores and to calculate reflection coefficients. The pore sizes for the pre-clinical standard formulation of 1.5% (w/v) medium viscosity alginate cross-linked with 1.5% CaCl2 and 0.5% (w/v) alginate and chitosan cross-linked with 20% CaCl2 are 5.2 nm ± 0.9 nm and 7.0 nm ± 3.1 nm, respectively. An increase in the glass transition temperatures as a function of cross-linker concentration was observed. Diffusivity values obtained from the inward diffusivity of creatinine into macrocapsules (d = 1000 μm ± 75 μm) and the outward diffusivity of FITC dextrans from macrocapsules (d = 1000 μm ± 75 μm) and microcapsules (d = 40 μm ± 5 μm) were shown to correlate strongly (R2 = 0.9835) with the ratio of solute to pore sizes, confirming the presence of through pores. Reflection coefficients approaching and exceeding unity correlate with the lack of permeability of the membranes to MW markers that are 70 kDa and greater.
基金Financial support from the Ministry of Education Singapore under the AcRF Tier 1(MOE T1 RG11/21)and AcRF Tier 2(MOE-T2EP10221-0002)The Deutsche Forschungsgemeinschaft via grants(nos.SCHI 619/13 and EB535/1-1)+5 种基金the GRK(Research Training Group)2204“Substitute Materials for Sustainable Energy Technologies”the LOEWE Program of Excellence of the Federal State of Hesse(LOEWE Focus Group PriOSS“Principles of On-Surface Synthesis”)the National Natural Science Foundation of China(grant nos.21790053,51821002,and 22072103)the National Major State Basic Research Development Program of China(grant nos.2017YFA0205000 and 2017YFA0205002)the Collaborative Innovation Center of Suzhou Nano Science&Technologythe 111 Project are also acknowledged for their financial support.
文摘A highly distorted chiral nanographene structure composed of triple corannulene-fused[5]helicenes is prepared with the help of the Heck reaction and oxidative photocyclization with an overall isolated yield of 28%.The complex three-dimensional(3D)structure of the bowl-helix hybrid nanostructure is studied by a combination of noncontact atomic force microscopy(AFM)and scanning tunneling microscopy(STM)on the Cu(111)surface,density functional theory calculations,AFM/STM simulations,and high-performance liquid chromatography-electronic circular dichroism analysis.This examination reveals a molecular structure in which the three bowl-shaped corannulene bladesd position themselves in a C3-symmetric fashion around a highly twisted triphenylene core.The molecule appears to be shaped like a propeller in which the concave side of the bowls face away from the connected[5]helicene motif.The chirality of the nanostructure is confirmed by the direct visualization of both MMM and PPP enantiomers at the single-molecule level by scanning probe microscopies.These results underline that submolecular resolution imaging by AFM/STM is a powerful real-space tool for the stereochemical characterization of 3D curved chiral nanographene structures.
基金Project supported by the National Natural Science Foundation of China.
文摘The Langmuir-Blodgett (LB) technique is now widely used in construction of monolayeror multilayer of organic molecular thin film, of which the structures are controlled on themolecular level. Ths ultrathin organic molecular film has been extensively studied andapplied due to its special physical and chemical properties. The detailed investigation of
基金supported by the National Natural Science Foundation of China(Nos.62003172,61633012,and 21933006).
文摘To improve the scanning speed of an atomic force microscopy(AFM),a smooth scanning pattern is elaborately devised via trajectory shaping in this paper,so as to achieve fast imaging without hardware modification.Specifically,in the proposed scanning method,the piezoelectric actuator tracks a well-designed smooth periodic signal in x-direction,and simultaneously tracks a step signal in y-direction.The advantage of the proposed method is that it does not require additional data reprocessing to construct the morphology of the sample surface,while significantly increasing the scanning bandwidth restricted by the raster scanning method.Particularly,to directly utilize the height data collected by scanning to produce the sample morphology,the forward process in the common raster scanning mode is retained in the proposed method,the tracking signal in the forward process is thus set to a ramp function in x-direction.In addition,to ensure the continuity and smoothness of the entire tracking signal in x-direction,a segment of a sine curve is uniquely determined as the backward tracking signal by position and acceleration constraints,so as to ensure that the forward and backward curves are continuous and acceleration-continuous at the intersection point.Moreover,the frequency spectrum analysis of the designed smooth signal is carried out to exhibit the depressed amplitudes of high-frequency components,which demonstrates that the proposed method is able to reduce the resonance in AFM high-speed scanning,so as to improve the capacity of rapidly generating high-quality images.Finally,convincing comparison experiments are implemented to verify the imaging performance of the designed scanning algorithm.
基金supported by the National Natural Science Foundation of China(Nos.62271238,22372074,62301240)Yunnan Fundamental Research Projects(Nos.202201AT070078,202201BE070001-009 and 202301AW070017)+2 种基金the Major Basic Research Project of Science and Technology of Yunnan(202302AG050007)Yunnan Innovation Team of Graphene Mechanism Research and Application Industrialization(202305AS350017)Graphene Application and Engineering Research Centre of Education Department of Yunnan Providence(KKPP202351001).
文摘Comprehensive Summary Kagome lattices have garnered significant attention due to their promising applications in catalysis,electronics,and magnetics.Although many efforts have been paid to the design and synthesis of Kagome lattices,there is a limited focus on constructing this lattice by multiple interaction forces.In this work,we employ 2,7-dibromo-carbazole as precursors to successfully fabricate the two-dimensional self-assembly Kagome lattices stabled by multiple interaction forces on Au(111)substrate.Using low-temperature scanning tunneling microscopy,non-contact atomic force microscopy and density functional theory calculation,we visualize and identify the four interaction forces within Kagome lattices:Au—N coordination bonds,Au—H hydrogen bonds,Br—Br halogen bonds,and Br—H hydrogen bonds,respectively.This study provides a basic understanding for designing and constructing more complex Kagome lattices.
基金financial support from the National Natural Science Foundation of China(No.51961026)。
文摘The localized micro-galvanic corrosion process and the kinetic information of Mg-(7,9)Al-1Fe-x Nd alloys were investigated by in situ observation under electrochemical control and in situ atomic force microscopy(AFM)in an electrolyte environment.The results revealed that the formation of the Nd-rich phase in alloys resulted in a decrease in the Volta potential difference from~400 m V(AlFe3/α-Mg)to~220 mV(Nd-rich/α-Mg),reducing the corrosion products around the cathodic phase and corrosion current density of the microscale area.The addition of Nd significantly improved the corrosion resistance,mainly due to the suppression of the micro-galvanic corrosion between the second phases and substrate.Finally,the corrosion mechanism of Mg-(7,9)Al-1Fe-x Nd alloys was discussed based on in situ observations and electrochemical results.
基金supported by the National Natural Science Foundation of China (60904095, 61175103)the CAS FEA International Partnership Program for Creative Research Teams
文摘Atomic force microscopy (AFM) was used to locate CD20 molecules on the surface of lymphoma Raji cells. Rituximab (a monoclonal antibody against CD20) molecules were linked onto the AFM tip via a polyethylene glycol (PEG) linker. Raji cells were adsorbed onto glass slides coated with poly-L-lysine. First, the CD20 distribution in a local area of the cell surface was visualized using the AFM lift scan mode. Second, 16 × 16 force curves were obtained from the same cell area to construct the CD20-rituximab binding force map. Finally, free rituximab was added to block the CD20 molecules on the cell surface and the lift phase image and CD20-rituximab force map were obtained again. The experimental results indicated that when the lift height was greater than the length of the PEG linker, no recognition sites were observed in the lift phase image. However, as the lift height decreased to the length of the PEG linker, some recognition sites were observed in the lift phase image and these sites were generally consistent with the pixels in the force map. After blocking, both the recognition sites in the lift phase image and the gray pixels in the binding force map decreased markedly. These results can improve our understanding of the distribution of protein molecules on the cell surface and facilitate further investigations into cellular functions.
基金supported by the National Basic Research Program of China(2012CB933001)the National Natural Science Foundation of China(21173058,21203038)
文摘We investigated the orientations of interface dipole moments of individual non-planar titanyl phthalocyanine(TiOPc)molecules on Cu(111)and Cu(100)substrates using scanning tunneling microscope(STM)and noncontact atomic force microscope(NC-AFM).The dipole moment orientations corresponding to two different configurations of individual TiOPc molecules were determined unambiguously.The correlation between the actual molecular structures and the corresponding STM topographies is proposed based on the sub-molecular resolution imaging and local contact potential difference(LCPD)measurements.Comparing with the pristine substrate,the LCPD shift due to the adsorption of non-planar molecule is dependent on the permanent molecular dipole,the charge transfer between the surface and the molecule,and the molecular configurations.This work would shed light on tailoring interfacial electronic properties and controlling local physical properties via polar molecule adsorption.
基金funded by the National Natural Science Foundation of China(Nos.21872039 and 22072030)the Fundamental Research Funds for the Central Universities(No.20720220008)the Science and Technology Commission of Shanghai Municipality(No.22520711100).
文摘The rational design of efficient artificial photosynthetic components requires thorough understandings towards(photo)electrochemical properties and kinetic processes at the solid/liquid interface.Electrochemical scanning probe microscopy(EC-SPM),which enables the high-spatial resolution imaging in an electrolyte environment,becomes an indispensable experimental technique for operando studies of(photo)electrochemistry.This review summarizes the latest results of relevant ECSPM techniques to study the interfacial properties of electrocatalysts and photoelectrodes.Covered methods include atomic force microscopy,Kelvin probe force microscopy,conductive atomic force microscopy,scanning tunneling microscopy,scanning electrochemical microscopy,and other advanced SPM-based operando techniques.Finally,we offer some perspectives on the future outlook in this fascinating research area.
