The nano-Ag paste consisted of Ag nanoparticles and organic solvents.These organics would be removed by evaporation or decomposition during sintering.When the sintering temperature was 300℃,the resistivity of sintere...The nano-Ag paste consisted of Ag nanoparticles and organic solvents.These organics would be removed by evaporation or decomposition during sintering.When the sintering temperature was 300℃,the resistivity of sintered bulk was 8.35×10^-6Ωcm,and its thermal conductivity was 247 W m^-1 K^-1.The Si/SiC chips and direct bonding copper(DBC)substrates could be bonded by this nano-Ag paste at low temperature.The bonding interface,sintered microstructure and shear strength of Si/SiC chip attachment were investigated by scanning electron microscopy,transmission electron microscopy and shear tests.Results showed that the sintered Ag layer was porous structure and tightly adhered to the electroless nickel immersion gold surface of DBC substrate and formed the continuous Ag–Au interdiffusion layer.The shear strength of Si and SiC chip attachments was higher than 35 MPa when the sintering pressure was 10 MPa.The fracture occurred inside the sintered Ag layer,and the fracture surface had obvious plastic deformation.展开更多
Released Ag ions or/and Ag particles are believed to contribute to the cytotoxicity of Ag nanomaterials,and thus,the cytotoxicity and mechanism of Ag nanomaterials should be dynamic in water due to unfixed Ag particle...Released Ag ions or/and Ag particles are believed to contribute to the cytotoxicity of Ag nanomaterials,and thus,the cytotoxicity and mechanism of Ag nanomaterials should be dynamic in water due to unfixed Ag particle:Ag+ ratios.Our recent research found that the cytotoxicity of PVP-Ag nanoparticles is attributable to Ag particles alone in 3 hr bioassays,and shifts to both Ag particles and released Ag^+ in 48 hr bioassays.Herein,as a continued study,the cytotoxicity and accumulation of 50 and 100 nm Ag colloids in Escherichia coli were determined dynamically.The cytotoxicity and mechanisms of nanoAg colloids are dynamic throughout exposure and are derived from both Ag ions and particles.Ag accumulation by E.coli is derived mainly from extracellular Ag particles during the initial 12 hr of exposure,and thereafter mainly from intracellular Ag ions.Fe^3+ accelerates the oxidative dissolution of nano-Ag colloids,which results In decreasing amounts of Ag particles and particle-related toxicity.Na^+ stabilizes nano-Ag colloids,thereby decreasing the bioavailability of Ag particles and particle-related toxicity.Humic acid(HA) binds Ag^+ to form Ag^+-HA,decreasing ion-related toxicity and binding to the E.coli surface,decreasing particle-related toxicity.HA in complex conditions showed a stronger relative contribution to toxicity and accumulation than Na^+ or Fe^3+.The results highlighted the cytotoxicity and mechanism of nano-Ag colloids are dynamic and affected by environmental factors,and therefore exposure duration and water chemistry should be seriously considered in environmental and health risk assessments.展开更多
Graphene oxide (GO) is a graphene derivatives that has oxygen-containing functional groups on the graphene basal plane, such as hydroxyl, carbonyl, epoxy and carboxyl groups. GO is considered as a promising material f...Graphene oxide (GO) is a graphene derivatives that has oxygen-containing functional groups on the graphene basal plane, such as hydroxyl, carbonyl, epoxy and carboxyl groups. GO is considered as a promising material for biological applications owing to its excellent surface functionalizability, high specific suface area and good biocompatibility. In this study, GO/chitosan hybrid scaffolds were prepared for tissue engineering. Nano silver was loaded into the scaffold to improve its antibacterial ability and biomimetic Ca-P coatings were deposited on the scaffold surface to enhance its osteoconductivity. First, GO was prepared by the chemical oxidization of graphite. Secondly, nano-Ag loaded GO was prepared by chemical reducing Ag ions in GO solutions. Then, nano-Ag loaded GO solution was mixed with CS solution to form GO-CS gel. Chitosan (CS) and GO were crosslinked by electrostatic interactions between oxygen-containing functional groups of GO and NH2 groups of CS. The gel were freeze dried to produce nano-Ag loaded GO/CS hybrid porous scaffolds. Finally, the as-prepared scaffolds were immersed the into a supersaturated calcium phosphate solution (SCPS) for 7 days to deposite CaP coatings on the surface of the micropores. SEM images showed that nano-Ag uniformly distributed in the scaffold and the CaP covered most of the scaffold surfaces. In vitro cell culture and antimicrobial test indicated the biomimetic mineralized Ag-CS-GO scaffolds have good osteoconductivity and bactericidal ability.展开更多
Nano-silver/polyvinylpyrrolidone(PVP)composite materials were successfully synthesized bi-insitu from silver nitrate solution with N-vinyl pyrrolidone (NVP) monomer,containing neither initiator nor reductant, in ultra...Nano-silver/polyvinylpyrrolidone(PVP)composite materials were successfully synthesized bi-insitu from silver nitrate solution with N-vinyl pyrrolidone (NVP) monomer,containing neither initiator nor reductant, in ultraviolet irradiation conditions.The resultant Ag/PVP nanocomposites were characterized by infrared spectroscopy (FT-IR), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD).TEM show that nano silver particles are homogeneously dispersed in PVP polymer matrix, and the mean size of spherical silver particles is about 5 nm.The spectroscopy of XPS and FTIR showed that there is an interaction between nano silver not only with carbonyl oxygen but also with the nitrogen group within the NVP molecule through the p-π conjugation effect in the nano-silver/PVP composites system.展开更多
Steady TiO2 water-sol was prepared by peptization and the effects of pH value, temperature, concentration of colloid and peptizator on sol were investigated. Laser grain analyzer was used to verify nano-particles in t...Steady TiO2 water-sol was prepared by peptization and the effects of pH value, temperature, concentration of colloid and peptizator on sol were investigated. Laser grain analyzer was used to verify nano-particles in the sol. The photocatalytic degradation ratio and antibacterial property of nano-Ag/TiO2 thin-film on ceramics were used as the main index in addition to XRD analysis. The effect of film layers, embedding Ag+, annealing temperature and time on the degradation ratio and antibacterial property was studied. The temperature 30-80 ℃, pH 1.2-2.0, concentrations of 0.05-0.3 mol/L sol and 5% HNO3 would be the optimal parameters for the TiO2 water-sol preparation. The nano-Ag/TiO2 film of three layers with 3% AgNO3 embedded and treated at 350 ℃ for 2 h exhibits good performance. The elementary research on the kinetics of degradation shows that the reactions are on the first order kinetics equation.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2017YFB1104900)the China Postdoctoral Science Foundation(No.2019M650425)。
文摘The nano-Ag paste consisted of Ag nanoparticles and organic solvents.These organics would be removed by evaporation or decomposition during sintering.When the sintering temperature was 300℃,the resistivity of sintered bulk was 8.35×10^-6Ωcm,and its thermal conductivity was 247 W m^-1 K^-1.The Si/SiC chips and direct bonding copper(DBC)substrates could be bonded by this nano-Ag paste at low temperature.The bonding interface,sintered microstructure and shear strength of Si/SiC chip attachment were investigated by scanning electron microscopy,transmission electron microscopy and shear tests.Results showed that the sintered Ag layer was porous structure and tightly adhered to the electroless nickel immersion gold surface of DBC substrate and formed the continuous Ag–Au interdiffusion layer.The shear strength of Si and SiC chip attachments was higher than 35 MPa when the sintering pressure was 10 MPa.The fracture occurred inside the sintered Ag layer,and the fracture surface had obvious plastic deformation.
基金supported by the Joint Funds of the National Natural Science Foundation of China (No.U1804109)the State Key Laboratory of Motor Vehicle Biofuel Technology (No.KFKT2018006)+3 种基金the Scientific Research and Service Platform Fund of Henan Province (No.2016151)the Key Scientific and Technological Research Projects in Henan Province (No. 192102310305)the Foundation of Henan Educational Committee (No.19A330003)the Foundation of Nanyang Normal University (No.2018ZX023).
文摘Released Ag ions or/and Ag particles are believed to contribute to the cytotoxicity of Ag nanomaterials,and thus,the cytotoxicity and mechanism of Ag nanomaterials should be dynamic in water due to unfixed Ag particle:Ag+ ratios.Our recent research found that the cytotoxicity of PVP-Ag nanoparticles is attributable to Ag particles alone in 3 hr bioassays,and shifts to both Ag particles and released Ag^+ in 48 hr bioassays.Herein,as a continued study,the cytotoxicity and accumulation of 50 and 100 nm Ag colloids in Escherichia coli were determined dynamically.The cytotoxicity and mechanisms of nanoAg colloids are dynamic throughout exposure and are derived from both Ag ions and particles.Ag accumulation by E.coli is derived mainly from extracellular Ag particles during the initial 12 hr of exposure,and thereafter mainly from intracellular Ag ions.Fe^3+ accelerates the oxidative dissolution of nano-Ag colloids,which results In decreasing amounts of Ag particles and particle-related toxicity.Na^+ stabilizes nano-Ag colloids,thereby decreasing the bioavailability of Ag particles and particle-related toxicity.Humic acid(HA) binds Ag^+ to form Ag^+-HA,decreasing ion-related toxicity and binding to the E.coli surface,decreasing particle-related toxicity.HA in complex conditions showed a stronger relative contribution to toxicity and accumulation than Na^+ or Fe^3+.The results highlighted the cytotoxicity and mechanism of nano-Ag colloids are dynamic and affected by environmental factors,and therefore exposure duration and water chemistry should be seriously considered in environmental and health risk assessments.
文摘Graphene oxide (GO) is a graphene derivatives that has oxygen-containing functional groups on the graphene basal plane, such as hydroxyl, carbonyl, epoxy and carboxyl groups. GO is considered as a promising material for biological applications owing to its excellent surface functionalizability, high specific suface area and good biocompatibility. In this study, GO/chitosan hybrid scaffolds were prepared for tissue engineering. Nano silver was loaded into the scaffold to improve its antibacterial ability and biomimetic Ca-P coatings were deposited on the scaffold surface to enhance its osteoconductivity. First, GO was prepared by the chemical oxidization of graphite. Secondly, nano-Ag loaded GO was prepared by chemical reducing Ag ions in GO solutions. Then, nano-Ag loaded GO solution was mixed with CS solution to form GO-CS gel. Chitosan (CS) and GO were crosslinked by electrostatic interactions between oxygen-containing functional groups of GO and NH2 groups of CS. The gel were freeze dried to produce nano-Ag loaded GO/CS hybrid porous scaffolds. Finally, the as-prepared scaffolds were immersed the into a supersaturated calcium phosphate solution (SCPS) for 7 days to deposite CaP coatings on the surface of the micropores. SEM images showed that nano-Ag uniformly distributed in the scaffold and the CaP covered most of the scaffold surfaces. In vitro cell culture and antimicrobial test indicated the biomimetic mineralized Ag-CS-GO scaffolds have good osteoconductivity and bactericidal ability.
文摘Nano-silver/polyvinylpyrrolidone(PVP)composite materials were successfully synthesized bi-insitu from silver nitrate solution with N-vinyl pyrrolidone (NVP) monomer,containing neither initiator nor reductant, in ultraviolet irradiation conditions.The resultant Ag/PVP nanocomposites were characterized by infrared spectroscopy (FT-IR), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD).TEM show that nano silver particles are homogeneously dispersed in PVP polymer matrix, and the mean size of spherical silver particles is about 5 nm.The spectroscopy of XPS and FTIR showed that there is an interaction between nano silver not only with carbonyl oxygen but also with the nitrogen group within the NVP molecule through the p-π conjugation effect in the nano-silver/PVP composites system.
基金Projects(04GK2007,2007CK3075 ) supported by Industrial Key Project of Science and Technology of Hunan Province, China
文摘Steady TiO2 water-sol was prepared by peptization and the effects of pH value, temperature, concentration of colloid and peptizator on sol were investigated. Laser grain analyzer was used to verify nano-particles in the sol. The photocatalytic degradation ratio and antibacterial property of nano-Ag/TiO2 thin-film on ceramics were used as the main index in addition to XRD analysis. The effect of film layers, embedding Ag+, annealing temperature and time on the degradation ratio and antibacterial property was studied. The temperature 30-80 ℃, pH 1.2-2.0, concentrations of 0.05-0.3 mol/L sol and 5% HNO3 would be the optimal parameters for the TiO2 water-sol preparation. The nano-Ag/TiO2 film of three layers with 3% AgNO3 embedded and treated at 350 ℃ for 2 h exhibits good performance. The elementary research on the kinetics of degradation shows that the reactions are on the first order kinetics equation.
