Y2O2S:Yb/Ho-silica/aminosilane core-shell nanoparticles were prepared by a solid-gas method in combination with polyvinylpyr-rolidone assisted one-step ammoniating method. The core was a single Y2O2S:Yb/Ho with 80 nm ...Y2O2S:Yb/Ho-silica/aminosilane core-shell nanoparticles were prepared by a solid-gas method in combination with polyvinylpyr-rolidone assisted one-step ammoniating method. The core was a single Y2O2S:Yb/Ho with 80 nm in diameter and the shell was silica/aminosilane with around 5 nm in thickness. The results of sedimentation experiment indicated that the nanoparticles could be well-dispersed in ethanol and water to form stable colloids. Since the coating weakened lattice vibration energies of the Y2O2S:Yb/Ho...展开更多
The Paleoproterozoic Francevillian Group in the eastern Gabonese Republic has been recently attracting increasing attention because it includes distinctive macroscopic structures interpreted as eukaryotic fossils.Ther...The Paleoproterozoic Francevillian Group in the eastern Gabonese Republic has been recently attracting increasing attention because it includes distinctive macroscopic structures interpreted as eukaryotic fossils.Therefore,its depositional setting and associated redox conditions need to be clearly understood.To clarify these,petrological studies and rare earth element(REE)abundances of carbonate rocks of the Francevillian Group in the Lastoursville basin were determined with ICP-MS coupled with a laser ablation sampling technique.Detailed microscopic observations indicate that dolostones in this basin underwent the complicated diagenetic history,including sparitization,decomposition of organic matter,reduction of ferromanganese oxides,silicification,and later calcification.The dolostones of lower Francevillian B(FB)Formation show heterogeneous textures formed by alterations during diagenesis.By the alterations,changes of REE abundances and degrees of positive Y anomalies appear to have occurred.This indicates that REE signatures in carbonate rocks can vary during diagenesis.Characteristically high Mn contents in the dolostones of upper FB Formation were derived from the reduction of ferromanganese oxides in sediments.The signatures of REE abundance in dolostones can be explained by the mixing of seawater and ferromanganese oxide components.In that sense,the dolostones inherited the trace element characteristics of precursor ferromanganese oxides even after the diagenesis.Y/Ho values of the most primary parts of each sample exceed 33,the newly determined threshold value for marine carbonate rocks based on our compilation.The magnitude of the La anomaly values also falls within the range of that of Holocene reefal microbialites.These indicate that a precursor of the dolostone of the Francevillian Group was deposited in a marine environment.In addition,presence of Ce anomalies in the upper FB Formation suggests that the Paleoproterozoic ocean was oxidized to such an extent as for Ce to be preferentially absorbed by ferromanganese oxides。展开更多
基金Project supported by the National Natural Science Foundation of China (60979003 and 20977012)
文摘Y2O2S:Yb/Ho-silica/aminosilane core-shell nanoparticles were prepared by a solid-gas method in combination with polyvinylpyr-rolidone assisted one-step ammoniating method. The core was a single Y2O2S:Yb/Ho with 80 nm in diameter and the shell was silica/aminosilane with around 5 nm in thickness. The results of sedimentation experiment indicated that the nanoparticles could be well-dispersed in ethanol and water to form stable colloids. Since the coating weakened lattice vibration energies of the Y2O2S:Yb/Ho...
基金Shoko Science Co.Ltd.This work was partly supported by a grant from the Ministry of Education,Culture,Sports,Science and Technology,Japan(No.17H04858,19H01081,19K14828,20H01991,23K13205)the Fukada Grant-in-Aid(2021)of Fukada Geological Institute(No.135).
文摘The Paleoproterozoic Francevillian Group in the eastern Gabonese Republic has been recently attracting increasing attention because it includes distinctive macroscopic structures interpreted as eukaryotic fossils.Therefore,its depositional setting and associated redox conditions need to be clearly understood.To clarify these,petrological studies and rare earth element(REE)abundances of carbonate rocks of the Francevillian Group in the Lastoursville basin were determined with ICP-MS coupled with a laser ablation sampling technique.Detailed microscopic observations indicate that dolostones in this basin underwent the complicated diagenetic history,including sparitization,decomposition of organic matter,reduction of ferromanganese oxides,silicification,and later calcification.The dolostones of lower Francevillian B(FB)Formation show heterogeneous textures formed by alterations during diagenesis.By the alterations,changes of REE abundances and degrees of positive Y anomalies appear to have occurred.This indicates that REE signatures in carbonate rocks can vary during diagenesis.Characteristically high Mn contents in the dolostones of upper FB Formation were derived from the reduction of ferromanganese oxides in sediments.The signatures of REE abundance in dolostones can be explained by the mixing of seawater and ferromanganese oxide components.In that sense,the dolostones inherited the trace element characteristics of precursor ferromanganese oxides even after the diagenesis.Y/Ho values of the most primary parts of each sample exceed 33,the newly determined threshold value for marine carbonate rocks based on our compilation.The magnitude of the La anomaly values also falls within the range of that of Holocene reefal microbialites.These indicate that a precursor of the dolostone of the Francevillian Group was deposited in a marine environment.In addition,presence of Ce anomalies in the upper FB Formation suggests that the Paleoproterozoic ocean was oxidized to such an extent as for Ce to be preferentially absorbed by ferromanganese oxides。
