The Earth surface is a multiple open system. Semiconducting minerals, including most metal oxides and sulfides, absorb visible light of the solar spectrum. Microorganisms evolve varied pathways to get carbon and energ...The Earth surface is a multiple open system. Semiconducting minerals, including most metal oxides and sulfides, absorb visible light of the solar spectrum. Microorganisms evolve varied pathways to get carbon and energy sources. It is obvious that the interaction among solar light, semiconducting minerals, photoelectron/photohole, organics, inorganics, valence electrons and microorganisms occurs continuously on our planet. In a recent study, Lu et al. (2012) presented evidence demonstrating solar energy mediated by semiconducting mineral photocatalysis, acting as energy source, promoted the growth of some non-photosynthetic bacteria and revealed that the ternary system of microorganisms, minerals and solar light has played a critical role in the history of life on our planet. In simulated system, under simulated solar light semiconducting minerals, such as metal oxides and metal sulfides, generates photoelectrons which could be used by non-phototrophic microorganisms to support their metabolisms. The growth of microorganism was closely related to photon quantity and energy, and the microorganism growth and mineral light absorption spectra were fitted well under different light wavelengths. The overall energy efficiency from photon to biomass was 0.13‰ to 1.9‰. Further studies revealed that in natural soil systems, semiconducting mineral photocatalysis could influence the microbial population. Solar energy utilization pathway by nonphototrophic microorganisms mediated by semiconducting mineral photocatalysis provides a new concept to evaluate the origin and evolution of life. Semiconducting minerals are ubiquitous on Earth’s surface and widely participate in redox reactions following photoelectron-photohole pairs excited by solar light. As photoholes can be easily scavenged by environmental reductive substances and microorganisms possess multiple strategies to utilize extracellular electrons, the highly reductive photoelectrons serve as potential energy source for microbial life. The discovery of this pathway extends our knowledge on the use of solar energy by nonphototrophic microorganisms, and provides important clues to evaluate life on the early Earth. Microorganisms, minerals and solar light constitute a complex but important ternary system through Earth history. The discovery of the novel energy conversion pathway in this system demonstrates how nonphototrophic microorganisms directly or indirectly utilized photoelectrons as the solar energy source. The fully comprehending of nonphototrophic bacteria solar energy utilization conducted by semiconducting minerals in present environment will greatly help us to better understand the energy transform mechanism among interfaces of lithosphere, pedosphere, hydrosphere and biosphere.展开更多
Magnesium alloys as medical implant materials necessitate a lower and adjustable corrosion rate for clinical applications.The microstructure and corrosion behavior of AZ31Mn-xEr(x=0.1,0.5,1.2)alloys were systematicall...Magnesium alloys as medical implant materials necessitate a lower and adjustable corrosion rate for clinical applications.The microstructure and corrosion behavior of AZ31Mn-xEr(x=0.1,0.5,1.2)alloys were systematically investigated using optical microscopy(OM),scanning electron microscopy(SEM),and X-ray photoelectron spectroscopy(XPS),combined with Tafel polarization and electrochemical impedance spectroscopy(EIS)analyses.The findings showed that the alloying element Er refined the grain structure during solidification by increasing the nucleation rate and forming a secondary phase of Al_(3)Er with Al.The Er and Mg in the matrix co-oxidize to form a dense MgO/Er_(2)O_(3)composite oxide,preventing the formation of loose magnesium hydroxide/basic magnesium carbonate.The trace alloying element Mn interacts with impurities Fe in the magnesium matrix to form an AlFeMn second phase,reducing micro-galvanic corrosion driving force.Electrochemical testing in a 3.5%NaCl solution demonstrated a marked reduction in corrosion rate from 10.46 mm/a(AZ 31 Mn alloy)to 0.44 mm/a(AZ31Mn-1.2Er alloy).This research offers a reference for searching for corrosion-resistant magnesium alloy and degradable medical magnesium alloy materials.展开更多
The surface characteristics and catalytic activity of Sb<sub>x</sub>O<sub>Y</sub>/ SiO<sub>2</sub> catalysts forvapor-phasc synthesis of isoprene from isobutylene and formaldehyde h...The surface characteristics and catalytic activity of Sb<sub>x</sub>O<sub>Y</sub>/ SiO<sub>2</sub> catalysts forvapor-phasc synthesis of isoprene from isobutylene and formaldehyde have been investi-gated by TPR, XRD, XPS, IR and catalytic activity evaluation. The results show that whenthe Sb loadings are less than about 5 wt%,Sb<sub>x</sub>O<sub>Y</sub> is compIctely dispersed on the surface ofsilica to form a surface compound with Sb（V）=O group and the catalysts have relativelyhigh catalytic activity; when the Sb loadings are more than 5 wt%, in addition to this surfacccompound, the crystalline α-Sb<sub>2</sub>O<sub>4</sub> is formed on the support surface and causes rapid de-crease of catalytic activity. It is suggcsted that the catalytic activity of Sb<sub>x</sub>O<sub>Y</sub> /siO<sub>2</sub> catalystsresults from synetgistic catalysis of the surface compound Sb（V）=O as the basic sites andthe surface silanol Si-OH as the acidie sites. The mechanism of this synergistic catalysis forisoprene production is discussed.展开更多
Chemical Composition,surface distribution of the elements and crystal structure offresh and deactivated Ag<sub>x</sub>Sb<sub>y</sub>O<sub>z</sub>/SiO<sub>2</sub> catalys...Chemical Composition,surface distribution of the elements and crystal structure offresh and deactivated Ag<sub>x</sub>Sb<sub>y</sub>O<sub>z</sub>/SiO<sub>2</sub> catalysts were investigated investigated by X-ray photoelectronspectroscopy（XPS）,scanning Auger microprobc（SAM）,electron microdiffraction（EMD）and atomic absorption spectroscopy（AAS）.From the experimental results that in-clude the activity evaluation of model catalyst Sb<sub>2</sub>O<sub>4</sub>/SiO<sub>2</sub> Which Shows the inertness ofSb<sub>2</sub>O<sub>4</sub> in Prins reaction,it is reasonable to infer that the active phase ofAg<sub>x</sub>Sb<sub>y</sub>O<sub>z</sub>/SiO<sub>2</sub> catalyst for Prins condensation reaction seems to be cubic AgSbO<sub>3</sub>.Thereason of the deactivation of the catalyst was discussed.It is suggested that silver componentseems to be unstable in this catalyst.展开更多
文摘The Earth surface is a multiple open system. Semiconducting minerals, including most metal oxides and sulfides, absorb visible light of the solar spectrum. Microorganisms evolve varied pathways to get carbon and energy sources. It is obvious that the interaction among solar light, semiconducting minerals, photoelectron/photohole, organics, inorganics, valence electrons and microorganisms occurs continuously on our planet. In a recent study, Lu et al. (2012) presented evidence demonstrating solar energy mediated by semiconducting mineral photocatalysis, acting as energy source, promoted the growth of some non-photosynthetic bacteria and revealed that the ternary system of microorganisms, minerals and solar light has played a critical role in the history of life on our planet. In simulated system, under simulated solar light semiconducting minerals, such as metal oxides and metal sulfides, generates photoelectrons which could be used by non-phototrophic microorganisms to support their metabolisms. The growth of microorganism was closely related to photon quantity and energy, and the microorganism growth and mineral light absorption spectra were fitted well under different light wavelengths. The overall energy efficiency from photon to biomass was 0.13‰ to 1.9‰. Further studies revealed that in natural soil systems, semiconducting mineral photocatalysis could influence the microbial population. Solar energy utilization pathway by nonphototrophic microorganisms mediated by semiconducting mineral photocatalysis provides a new concept to evaluate the origin and evolution of life. Semiconducting minerals are ubiquitous on Earth’s surface and widely participate in redox reactions following photoelectron-photohole pairs excited by solar light. As photoholes can be easily scavenged by environmental reductive substances and microorganisms possess multiple strategies to utilize extracellular electrons, the highly reductive photoelectrons serve as potential energy source for microbial life. The discovery of this pathway extends our knowledge on the use of solar energy by nonphototrophic microorganisms, and provides important clues to evaluate life on the early Earth. Microorganisms, minerals and solar light constitute a complex but important ternary system through Earth history. The discovery of the novel energy conversion pathway in this system demonstrates how nonphototrophic microorganisms directly or indirectly utilized photoelectrons as the solar energy source. The fully comprehending of nonphototrophic bacteria solar energy utilization conducted by semiconducting minerals in present environment will greatly help us to better understand the energy transform mechanism among interfaces of lithosphere, pedosphere, hydrosphere and biosphere.
基金Projects(82171030,81870678)supported by the National Natural Science Foundation of China。
文摘Magnesium alloys as medical implant materials necessitate a lower and adjustable corrosion rate for clinical applications.The microstructure and corrosion behavior of AZ31Mn-xEr(x=0.1,0.5,1.2)alloys were systematically investigated using optical microscopy(OM),scanning electron microscopy(SEM),and X-ray photoelectron spectroscopy(XPS),combined with Tafel polarization and electrochemical impedance spectroscopy(EIS)analyses.The findings showed that the alloying element Er refined the grain structure during solidification by increasing the nucleation rate and forming a secondary phase of Al_(3)Er with Al.The Er and Mg in the matrix co-oxidize to form a dense MgO/Er_(2)O_(3)composite oxide,preventing the formation of loose magnesium hydroxide/basic magnesium carbonate.The trace alloying element Mn interacts with impurities Fe in the magnesium matrix to form an AlFeMn second phase,reducing micro-galvanic corrosion driving force.Electrochemical testing in a 3.5%NaCl solution demonstrated a marked reduction in corrosion rate from 10.46 mm/a(AZ 31 Mn alloy)to 0.44 mm/a(AZ31Mn-1.2Er alloy).This research offers a reference for searching for corrosion-resistant magnesium alloy and degradable medical magnesium alloy materials.
文摘The surface characteristics and catalytic activity of Sb<sub>x</sub>O<sub>Y</sub>/ SiO<sub>2</sub> catalysts forvapor-phasc synthesis of isoprene from isobutylene and formaldehyde have been investi-gated by TPR, XRD, XPS, IR and catalytic activity evaluation. The results show that whenthe Sb loadings are less than about 5 wt%,Sb<sub>x</sub>O<sub>Y</sub> is compIctely dispersed on the surface ofsilica to form a surface compound with Sb（V）=O group and the catalysts have relativelyhigh catalytic activity; when the Sb loadings are more than 5 wt%, in addition to this surfacccompound, the crystalline α-Sb<sub>2</sub>O<sub>4</sub> is formed on the support surface and causes rapid de-crease of catalytic activity. It is suggcsted that the catalytic activity of Sb<sub>x</sub>O<sub>Y</sub> /siO<sub>2</sub> catalystsresults from synetgistic catalysis of the surface compound Sb（V）=O as the basic sites andthe surface silanol Si-OH as the acidie sites. The mechanism of this synergistic catalysis forisoprene production is discussed.
文摘Chemical Composition,surface distribution of the elements and crystal structure offresh and deactivated Ag<sub>x</sub>Sb<sub>y</sub>O<sub>z</sub>/SiO<sub>2</sub> catalysts were investigated investigated by X-ray photoelectronspectroscopy（XPS）,scanning Auger microprobc（SAM）,electron microdiffraction（EMD）and atomic absorption spectroscopy（AAS）.From the experimental results that in-clude the activity evaluation of model catalyst Sb<sub>2</sub>O<sub>4</sub>/SiO<sub>2</sub> Which Shows the inertness ofSb<sub>2</sub>O<sub>4</sub> in Prins reaction,it is reasonable to infer that the active phase ofAg<sub>x</sub>Sb<sub>y</sub>O<sub>z</sub>/SiO<sub>2</sub> catalyst for Prins condensation reaction seems to be cubic AgSbO<sub>3</sub>.Thereason of the deactivation of the catalyst was discussed.It is suggested that silver componentseems to be unstable in this catalyst.
