The research of TiO2 nanotubes(TNTs)in the field of biomedicine has been increasingly active.However,given the diversity of the nanoscale dimension and controversial reports,our understanding of the structure-property...The research of TiO2 nanotubes(TNTs)in the field of biomedicine has been increasingly active.However,given the diversity of the nanoscale dimension and controversial reports,our understanding of the structure-property relationships of TNTs is not yet complete.In this paper,gradient TNTs with a wide diameter range of 20-350 nm were achieved by bipolar electrochemistry and utilized for a thorough high-throughput study of the effect of nanotube dimension and crystalline phase on protein adsorption and cell behaviors.Results indicated that protein adsorption escalated with nanotube dimension whereas cell proliferation and differentiation are preferred on small diameter(<70 nm)nanotubes.Large diameter anatase nanotubes had higher adsorption of serum proteins than as-prepared ones.But only as-prepared small diameter nanotubes presented slightly higher cell proliferation than corresponding annealed nanotubes whereas there was no discernible difference between as-prepared and annealed nanotubes on cell differentiation for the entire gradient.Those findings replenish previous research about how cell responses to TNTs with a wide diameter range and provide scientific guidance for the optimal design of biomedical materials.展开更多
Local domain structures of ferroelectrics have been studied extensively using various modes of scanning probes at the nanoscale,including piezoresponse force microscopy(PFM)and Kelvin probe force microscopy(KPFM),thou...Local domain structures of ferroelectrics have been studied extensively using various modes of scanning probes at the nanoscale,including piezoresponse force microscopy(PFM)and Kelvin probe force microscopy(KPFM),though none of these techniques measure the polarization directly,and the fast formation kinetics of domains and screening charges cannot be captured by these quasi-static measurements.In this study,we used charge gradient microscopy(CGM)to image ferroelectric domains of lithium niobate based on current measured during fast scanning,and applied principal component analysis(PCA)to enhance the signal-to-noise ratio of noisy raw data.We found that the CGM signal increases linearly with the scan speed while decreases with the temperature under power-law,consistent with proposed imaging mechanisms of scraping and refilling of surface charges within domains,and polarization change across domain wall.We then,based on CGM mappings,estimated the spontaneous polarization and the density of surface charges with order of magnitude agreement with literature data.The study demonstrates that PCA is a powerful method in imaging analysis of scanning probe microscopy(SPM),with which quantitative analysis of noisy raw data becomes possible.展开更多
The carrier screening effect occurs commonly in dielectric materials. It reduces the electric potential gradient, thus negatively affecting the functionality of resistive random access memory （RRAM） devices. An Au/Z...The carrier screening effect occurs commonly in dielectric materials. It reduces the electric potential gradient, thus negatively affecting the functionality of resistive random access memory （RRAM） devices. An Au/ZnO film/Al-doped ZnO device fabricated in this work exhibited no resistive switching （RS）, which was attributed to the carrier screening effect. Therefore, annealing was used for alleviating the screening effect, significantly enhancing the RS property. In addition, different on/off ratios were obtained for various bias values, and the screening effect was accounted for by investigating electron transport mechanisms. Furthermore, different annealing temperatures were employed to modulate the free carrier concentration in ZnO films to alleviate the screening effect. The maximal on/off ratio reached 10s at an annealing temperature of 600 ℃, yielding the lowest number of free carriers and the weakest screening effect in ZnO films. This work investigates the screening effect in RS devices. The screening effect not only modulates the characteristics of memory devices but also provides insight into the mechanism of RS in these devices.展开更多
基金the State Key Project of Research and Development(2016YFC1100300)National Natural Science Foundation of China(11904301,21773199)+1 种基金Natural Science Foundation of Guangdong Province,China(2016A030310370)111 Project(B16029)。
文摘The research of TiO2 nanotubes(TNTs)in the field of biomedicine has been increasingly active.However,given the diversity of the nanoscale dimension and controversial reports,our understanding of the structure-property relationships of TNTs is not yet complete.In this paper,gradient TNTs with a wide diameter range of 20-350 nm were achieved by bipolar electrochemistry and utilized for a thorough high-throughput study of the effect of nanotube dimension and crystalline phase on protein adsorption and cell behaviors.Results indicated that protein adsorption escalated with nanotube dimension whereas cell proliferation and differentiation are preferred on small diameter(<70 nm)nanotubes.Large diameter anatase nanotubes had higher adsorption of serum proteins than as-prepared ones.But only as-prepared small diameter nanotubes presented slightly higher cell proliferation than corresponding annealed nanotubes whereas there was no discernible difference between as-prepared and annealed nanotubes on cell differentiation for the entire gradient.Those findings replenish previous research about how cell responses to TNTs with a wide diameter range and provide scientific guidance for the optimal design of biomedical materials.
基金National Key Research and Development Program of China(2016YFA0201001)US National Science Foundation(CBET-1435968)+1 种基金National Natural Science Foundation of China(11627801,11472236 and 51472037)This material is based in part upon work supported by the State of Washington through the University of Washington Clean Energy Institute.
文摘Local domain structures of ferroelectrics have been studied extensively using various modes of scanning probes at the nanoscale,including piezoresponse force microscopy(PFM)and Kelvin probe force microscopy(KPFM),though none of these techniques measure the polarization directly,and the fast formation kinetics of domains and screening charges cannot be captured by these quasi-static measurements.In this study,we used charge gradient microscopy(CGM)to image ferroelectric domains of lithium niobate based on current measured during fast scanning,and applied principal component analysis(PCA)to enhance the signal-to-noise ratio of noisy raw data.We found that the CGM signal increases linearly with the scan speed while decreases with the temperature under power-law,consistent with proposed imaging mechanisms of scraping and refilling of surface charges within domains,and polarization change across domain wall.We then,based on CGM mappings,estimated the spontaneous polarization and the density of surface charges with order of magnitude agreement with literature data.The study demonstrates that PCA is a powerful method in imaging analysis of scanning probe microscopy(SPM),with which quantitative analysis of noisy raw data becomes possible.
基金Acknowledgements This work was supported by the National Basic Research Program of China （No. 2013CB932602）, the Program of Introducing Talents of Discipline to Universities （No. B14003）, National Natural Science Foundation of China （Nos. 51527802, 51372023, and 51232001）, Beijing Municipal Science ＆ Technology Commission, the Fundamental Research Funds for Central Universities.
文摘The carrier screening effect occurs commonly in dielectric materials. It reduces the electric potential gradient, thus negatively affecting the functionality of resistive random access memory （RRAM） devices. An Au/ZnO film/Al-doped ZnO device fabricated in this work exhibited no resistive switching （RS）, which was attributed to the carrier screening effect. Therefore, annealing was used for alleviating the screening effect, significantly enhancing the RS property. In addition, different on/off ratios were obtained for various bias values, and the screening effect was accounted for by investigating electron transport mechanisms. Furthermore, different annealing temperatures were employed to modulate the free carrier concentration in ZnO films to alleviate the screening effect. The maximal on/off ratio reached 10s at an annealing temperature of 600 ℃, yielding the lowest number of free carriers and the weakest screening effect in ZnO films. This work investigates the screening effect in RS devices. The screening effect not only modulates the characteristics of memory devices but also provides insight into the mechanism of RS in these devices.
