Mesoporous nanocrystal clusters of anatase TiO2 with large surface area and enhanced photocatalytic activity have been successfully synthesized. The synthesis involves the self-assembly of hydrophobic TiO2 nanocrystal...Mesoporous nanocrystal clusters of anatase TiO2 with large surface area and enhanced photocatalytic activity have been successfully synthesized. The synthesis involves the self-assembly of hydrophobic TiO2 nanocrystals into submicron clusters, coating of these clusters with a silica layer, thermal treatment to remove organic ligands and improve the crystallinity of the clusters, and finally removing silica to expose the mesoporous catalysts. With the help of the silica coating, the clusters not only maintain their small grain size but also keep their mesoporous structure after calcination at high temperatures （with BET surface area as high as 277 m2/g）. The etching of SiO2 also results in the clusters having high dispersity in water. We have been able to identify the optimal calcination temperature to produce TiO2 nanocrystal clusters that possess both high crystallinity and large surface area, and therefore show excellent catalytic efficiency in the decomposition of organic molecules under illumination by UV light. Convenient doping with nitrogen converts these nanocrystal clusters into active photocatalysts in both visible light and natural sunlight. The strategy of forming well-defined mesoporous clusters using nanocrystals promises a versatile and useful method for designing photocatalysts with enhanced activity and stability.展开更多
A novel way of producing superhydrophobic surfaces by applying a self-assembled monolayer(SAM)to silicon micro/nano-textured surfaces is presented in this paper.The micro/nano-textured surfaces on silicon substrates w...A novel way of producing superhydrophobic surfaces by applying a self-assembled monolayer(SAM)to silicon micro/nano-textured surfaces is presented in this paper.The micro/nano-textured surfaces on silicon substrates were generated by the aluminum-induced crystallization(AIC)of amorphous silicon(a-Si)technique.Octadecyltrichlorosilane(OTS)SAMs were then applied to the textured surfaces by dip coating.The topography and wetting properties of the resulting surfaces were characterized using scanning electron microscopy(SEM)and a video-based contact angle measurement system.The results show that by introducing OTS SAMs on the silicon micro/nano-textured surfaces,superhydrophobic surfaces with water contact angles(WCAs)of 155°were obtained,as compared to the WCAs of OTS-modified smooth silicon surfaces of about 112°.Surface topography was found to directly influence the WCA as predicted by the Cassie-Baxter model.展开更多
Lithium-sulfur batteries (LSBs) have been regarded as one of the most promising energy storage systems to break through the upper limit of lithium-ion batteries.However,the rampant diffusions of soluble lithium polysu...Lithium-sulfur batteries (LSBs) have been regarded as one of the most promising energy storage systems to break through the upper limit of lithium-ion batteries.However,the rampant diffusions of soluble lithium polysulfides (LiPSs) in the electrolyte induced the shuttle effect between anode and cathode,resulting in low sulfur utilization,low energy efficiency and short cycling life.Herein,we prove the rational design and construction of Ni nanoparticles filled in vertically grown N-doped bamboo-like carbon nanotubes (CNTs) on graphene nanosheets (Ni@NG-CNTs) as efficient polysulfide barrier for high-performance LSBs.The unique design integrates graphene nanosheets and CNTs into hierarchical architectures with one-dimensional (1D) CNTs,two-dimensional (2D) ultrethin nanosheets and abundant carbon nanocages.This design provides large surface area for lithium polysulfides (LiPSs) adsorption,accelerates electron transport and enhances electrochemical redox of LiPSs.Benefiting from the unique structural features,the LSBs with the Ni@NG-CNTs as polysulfide barrier keep high reversible specific capacities of 309.1 and 265.0 mAh·g-1 at 5 and 10 C rates after 500 cycles.This work provides a new strategy for constructing self-assembled hybrids of CNTs and graphene nanosheets with abundant carbon nanocages for high-performance LSBs.展开更多
The objective of this study was to investigate the potential of methoxy polyethylene glycol（m PEG）grafted chitosan（m PEG-g-CS） to be used as a drug carrier. m PEG-g-CS was successfully synthesized by one-step meth...The objective of this study was to investigate the potential of methoxy polyethylene glycol（m PEG）grafted chitosan（m PEG-g-CS） to be used as a drug carrier. m PEG-g-CS was successfully synthesized by one-step method with formaldehyde. The substitution degree of m PEG on chitosan was calculated by elemental analysis and was found to be（3.23 0.25）%. m PEG-g-CS self-assembled micelles were prepared by ultrasonic method with the controlled size of 178.5–195.1 nm and spherical morphology. Stable dispersion of the micelles was formed with the zeta potential of 2.3–30.2 m V. 5-Fluorouracil（5-FU）, an anticancer chemotherapy drug, was used as a model drug to evaluate the efficiency of the new drug delivery carrier. The loading efficiency of 5-FU was（4.01 0.03）%, and the drug-loaded m PEG-g-CS self-assembled micelle showed a controlled-release effect. In summary, the m PEG-g-CS self-assembled micelle is proved to be a promising carrier with controlled particle size and controlled-release effect. Therefore, it has great potential for the application as 5-FU carriers for effective anti-tumor activity.展开更多
Coordination to form polymer is emerging as a new technology for modifying or enhancing the properties of the existed energetic substances in energetic materials area. In this work, guanidine cation CN3 H6+ (Gu) and 3...Coordination to form polymer is emerging as a new technology for modifying or enhancing the properties of the existed energetic substances in energetic materials area. In this work, guanidine cation CN3 H6+ (Gu) and 3-amino-1,2,4-triazole C2H4N4(ATz) were crystallized into NaN5 and two novel energetic coordination polymers(CPs),(NaN5)5[(CH6-N3)N5](N5)3–(1) and(NaN5)2(C2H4N4)(2) were prepared respectively via a self-assembly process. The crystal structure reveals the co-existence of the chelating pentazole anion and organic component in the solid state. In polymer 1, Na+and N5– were coordinated to form a cage structure in which guanidine cation [C(NH2)3]+ was trapped;for polymer 2, a mixedligand system was observed;N5 – and ATz coordinate separately with Na+and form two independent but interweaved nets. In this way, coordination polymer has been successfully utilized to modify specific properties of energetic materials through crystallization. Benefiting from the coordination and weak interactions, the decomposition temperatures of both polymers increase from 111°C(1D structure [Na(H2 O)(N5)]?2 H2 O) to 118.4 and 126.5°C respectively. Moreover, no crystallized H2 O was generated in products to afford the anhydrous compounds of pentazole salts with high heats of formation( >800 kJ mol–1). Compared to traditional energetic materials, the advantage in heats of formation is still obvious for the cyclo-N5– based CPs, which highlights cyclo-N5– as a promising energetic precursor for high energy density materials(HEDMs).展开更多
The goal of this investigation was to develop and demonstrate a polymer/paclitaxel selfassembly(PTX-SA) formulation. Polymer/PTX-SAs were screened based on smaller size of formulation using dynamic light scattering an...The goal of this investigation was to develop and demonstrate a polymer/paclitaxel selfassembly(PTX-SA) formulation. Polymer/PTX-SAs were screened based on smaller size of formulation using dynamic light scattering analysis. Additionally, fluorescence microscopy and flow cytometry studies exhibited that polyvinylpyrrolidone(PVP)-based PTX-SAs(PVP/PTX-SAs) had superior cellular internalization capability in MCF7 and MDA-MB-231 breast cancer cells. The optimized PVP/PTXSAs exhibited less toxicity to human red blood cells indicating a suitable formulation for reducing systemic toxicity. The formation of PVP and PTX self-assemblies was confirmed using fluorescence quenching and transmission electron microscopy which indicated that the PVP/PTX-SAs were spherical in shape with an average size range of 53.81 nm as detected by transmission electron microscopy(TEM).FTIR spectral analysis demonstrates incorporation of polymer and paclitaxel functional groups in PVP/PTX-SAs. Both proliferation(MTS) and clonogenic(colony formation) assays were used to validate superior anticancer activity of PVP/PTX-SAs in breast cancer cells over paclitaxel. Such superior anticancer activity was also demonstrated by downregulation of the expression of pro-survival protein(Bcl-x L), upregulation of apoptosis-associated proteins(Bid, Bax, cleaved caspase 7, and cleaved PARP)and β-tubulin stabilization. These results support the hypothesis that PVP/PTX-SAs improved paclitaxel delivery to cancer cells.展开更多
文摘Mesoporous nanocrystal clusters of anatase TiO2 with large surface area and enhanced photocatalytic activity have been successfully synthesized. The synthesis involves the self-assembly of hydrophobic TiO2 nanocrystals into submicron clusters, coating of these clusters with a silica layer, thermal treatment to remove organic ligands and improve the crystallinity of the clusters, and finally removing silica to expose the mesoporous catalysts. With the help of the silica coating, the clusters not only maintain their small grain size but also keep their mesoporous structure after calcination at high temperatures （with BET surface area as high as 277 m2/g）. The etching of SiO2 also results in the clusters having high dispersity in water. We have been able to identify the optimal calcination temperature to produce TiO2 nanocrystal clusters that possess both high crystallinity and large surface area, and therefore show excellent catalytic efficiency in the decomposition of organic molecules under illumination by UV light. Convenient doping with nitrogen converts these nanocrystal clusters into active photocatalysts in both visible light and natural sunlight. The strategy of forming well-defined mesoporous clusters using nanocrystals promises a versatile and useful method for designing photocatalysts with enhanced activity and stability.
基金This material is based on work supported by the US National Science Foundation under Grant Nos.CMMI-0600642 and CMMI-0645040.
文摘A novel way of producing superhydrophobic surfaces by applying a self-assembled monolayer(SAM)to silicon micro/nano-textured surfaces is presented in this paper.The micro/nano-textured surfaces on silicon substrates were generated by the aluminum-induced crystallization(AIC)of amorphous silicon(a-Si)technique.Octadecyltrichlorosilane(OTS)SAMs were then applied to the textured surfaces by dip coating.The topography and wetting properties of the resulting surfaces were characterized using scanning electron microscopy(SEM)and a video-based contact angle measurement system.The results show that by introducing OTS SAMs on the silicon micro/nano-textured surfaces,superhydrophobic surfaces with water contact angles(WCAs)of 155°were obtained,as compared to the WCAs of OTS-modified smooth silicon surfaces of about 112°.Surface topography was found to directly influence the WCA as predicted by the Cassie-Baxter model.
基金Postdoctoral Science Foundation of China (No. 2017M611171)National Natural Science Foundation of China (NSFC)(Nos. 21571170, 2150116& and 51702236)Tianjin Municipal Science and Technology Commission (No. 17JCZDJC38000).
文摘Lithium-sulfur batteries (LSBs) have been regarded as one of the most promising energy storage systems to break through the upper limit of lithium-ion batteries.However,the rampant diffusions of soluble lithium polysulfides (LiPSs) in the electrolyte induced the shuttle effect between anode and cathode,resulting in low sulfur utilization,low energy efficiency and short cycling life.Herein,we prove the rational design and construction of Ni nanoparticles filled in vertically grown N-doped bamboo-like carbon nanotubes (CNTs) on graphene nanosheets (Ni@NG-CNTs) as efficient polysulfide barrier for high-performance LSBs.The unique design integrates graphene nanosheets and CNTs into hierarchical architectures with one-dimensional (1D) CNTs,two-dimensional (2D) ultrethin nanosheets and abundant carbon nanocages.This design provides large surface area for lithium polysulfides (LiPSs) adsorption,accelerates electron transport and enhances electrochemical redox of LiPSs.Benefiting from the unique structural features,the LSBs with the Ni@NG-CNTs as polysulfide barrier keep high reversible specific capacities of 309.1 and 265.0 mAh·g-1 at 5 and 10 C rates after 500 cycles.This work provides a new strategy for constructing self-assembled hybrids of CNTs and graphene nanosheets with abundant carbon nanocages for high-performance LSBs.
基金support from the Fundamental Research Funds for the Central Universities(No.WY1213013ECUST)supported by Science and Technology Commission of Shanghai Municipality(STCSM,contract Nos.11DZ2260600 and 10DZ2220500)
文摘The objective of this study was to investigate the potential of methoxy polyethylene glycol（m PEG）grafted chitosan（m PEG-g-CS） to be used as a drug carrier. m PEG-g-CS was successfully synthesized by one-step method with formaldehyde. The substitution degree of m PEG on chitosan was calculated by elemental analysis and was found to be（3.23 0.25）%. m PEG-g-CS self-assembled micelles were prepared by ultrasonic method with the controlled size of 178.5–195.1 nm and spherical morphology. Stable dispersion of the micelles was formed with the zeta potential of 2.3–30.2 m V. 5-Fluorouracil（5-FU）, an anticancer chemotherapy drug, was used as a model drug to evaluate the efficiency of the new drug delivery carrier. The loading efficiency of 5-FU was（4.01 0.03）%, and the drug-loaded m PEG-g-CS self-assembled micelle showed a controlled-release effect. In summary, the m PEG-g-CS self-assembled micelle is proved to be a promising carrier with controlled particle size and controlled-release effect. Therefore, it has great potential for the application as 5-FU carriers for effective anti-tumor activity.
基金financially supported by the National Natural Science Foundation of China (11702141, 21771108, and U1530101)
文摘Coordination to form polymer is emerging as a new technology for modifying or enhancing the properties of the existed energetic substances in energetic materials area. In this work, guanidine cation CN3 H6+ (Gu) and 3-amino-1,2,4-triazole C2H4N4(ATz) were crystallized into NaN5 and two novel energetic coordination polymers(CPs),(NaN5)5[(CH6-N3)N5](N5)3–(1) and(NaN5)2(C2H4N4)(2) were prepared respectively via a self-assembly process. The crystal structure reveals the co-existence of the chelating pentazole anion and organic component in the solid state. In polymer 1, Na+and N5– were coordinated to form a cage structure in which guanidine cation [C(NH2)3]+ was trapped;for polymer 2, a mixedligand system was observed;N5 – and ATz coordinate separately with Na+and form two independent but interweaved nets. In this way, coordination polymer has been successfully utilized to modify specific properties of energetic materials through crystallization. Benefiting from the coordination and weak interactions, the decomposition temperatures of both polymers increase from 111°C(1D structure [Na(H2 O)(N5)]?2 H2 O) to 118.4 and 126.5°C respectively. Moreover, no crystallized H2 O was generated in products to afford the anhydrous compounds of pentazole salts with high heats of formation( >800 kJ mol–1). Compared to traditional energetic materials, the advantage in heats of formation is still obvious for the cyclo-N5– based CPs, which highlights cyclo-N5– as a promising energetic precursor for high energy density materials(HEDMs).
基金performed under National Institute of Health/National Cancer Center's Career Development Award K22 CA174841,R15 CA 213232CORNET-UTHSC,Start-up by the College of Pharmacy,UTHSC to Murali M.Yallapu+1 种基金gratefully acknowledge the National Institutes of Health Research Project Grant Program (R01 CA210192,R01 CA206069,and CA204552) to Subhash C.ChauhanUTHSC-College of Pharmacy-Dean's Seed Grant support to Murali M.Yallapu,Meena Jaggi and Subhash C.Chauhan
文摘The goal of this investigation was to develop and demonstrate a polymer/paclitaxel selfassembly(PTX-SA) formulation. Polymer/PTX-SAs were screened based on smaller size of formulation using dynamic light scattering analysis. Additionally, fluorescence microscopy and flow cytometry studies exhibited that polyvinylpyrrolidone(PVP)-based PTX-SAs(PVP/PTX-SAs) had superior cellular internalization capability in MCF7 and MDA-MB-231 breast cancer cells. The optimized PVP/PTXSAs exhibited less toxicity to human red blood cells indicating a suitable formulation for reducing systemic toxicity. The formation of PVP and PTX self-assemblies was confirmed using fluorescence quenching and transmission electron microscopy which indicated that the PVP/PTX-SAs were spherical in shape with an average size range of 53.81 nm as detected by transmission electron microscopy(TEM).FTIR spectral analysis demonstrates incorporation of polymer and paclitaxel functional groups in PVP/PTX-SAs. Both proliferation(MTS) and clonogenic(colony formation) assays were used to validate superior anticancer activity of PVP/PTX-SAs in breast cancer cells over paclitaxel. Such superior anticancer activity was also demonstrated by downregulation of the expression of pro-survival protein(Bcl-x L), upregulation of apoptosis-associated proteins(Bid, Bax, cleaved caspase 7, and cleaved PARP)and β-tubulin stabilization. These results support the hypothesis that PVP/PTX-SAs improved paclitaxel delivery to cancer cells.
