Infrared emissivity was studied in Zn0.99M0.01O(M is Mn,Fe or Ni) and Zn1-xCoxO(x=0.01,0.02,0.03 and 0.04) powders synthesized by solid-state reaction at various temperatures.XRD patterns confirm the wurtzite structur...Infrared emissivity was studied in Zn0.99M0.01O(M is Mn,Fe or Ni) and Zn1-xCoxO(x=0.01,0.02,0.03 and 0.04) powders synthesized by solid-state reaction at various temperatures.XRD patterns confirm the wurtzite structure of the prepared samples.No peaks of other phases arising from impurities are detected in Mn-and Co-doped ZnO,but the peaks of ZnFe2O4 and NiO are observed in Zn0.99Fe0.01O and Zn 0.99 Ni 0.01 O.The SEM observations indicate that with larger grain sizes than those of Zn0.99Fe0.01O and Zn0.99Ni0.01O,Co-doped ZnO exhibits smooth grain surfaces.The infrared absorption spectra show that infrared absorptions related to oxygen in Zn0.99M0.01O are much stronger than those in Co-doped ZnO.Co ions are dissolved into the ZnO lattice with Co2+ state from XPS spectra analysis.The infrared emissivity results imply that the emissivity of Zn0.99Ni0.01 O is the highest(0.829) and that of Zn 0.99 Co 0.01 O is the lowest(0.784) at 1 200 C.The emissivity of Zn0.99Co0.01O decreases to the minimum(0.752) at 1 150 C and then increases with growing calcination temperature.As the Co doping content grows,the emissivity of Co-doped ZnO calcined at 1 200 C falls to 0.758 in the molar fraction of 3% and then ascends.展开更多
In DMSO/water(4:1),photolysis of the dihydroxy-Sn(IV)-rnesoporphyrin dimethyl ester (SnP)/methyl viologen(MV^(2+))/ethylene diamine tetraacetic acid(EDTA)ternary system produces methyl viologen cation radical with a q...In DMSO/water(4:1),photolysis of the dihydroxy-Sn(IV)-rnesoporphyrin dimethyl ester (SnP)/methyl viologen(MV^(2+))/ethylene diamine tetraacetic acid(EDTA)ternary system produces methyl viologen cation radical with a quantum yield of 0.67,much higher than that of systems with other metal complexes of rnesoporphyrin dimethyl ester.Neither EDTA nor MV^(2+) quenches the stationary fluorescence of SnP,implying that the reaction does not take place at the singlet state.With flash photolysis we obtain the T-T absorption spectrum of SnP(λ_(max)-440 nm).By following the decay of this absorption,the triplet life time of SnP is estimated to be 41 μs.The life time is related to the concentration of either MV^(2+) or EDTA.Good linear relationships are obtained by plotting τ_0/τ vs.the concentration of MV^(2+) or EDTA(Stern-Volmer plot),from which we determine the quenching constants:k_q(MV^(2+))=5.5×10~7 mol^(-7) s^(-1);kq(EDTA)=2.7×10~7 mol^(-1),s^(-1).The data suggests that upon photolysis of the above ternary system,both oxidative quenching and reductive quenching of the triplet state of the sensitizer are occurring.From the measured phosphorescence spectrum(λ_(max) 704nm)and the ground state redox potentials (E_(1/2)^(red)～-0.84V,E_(1/2)^(ox)～ Ag/AgCl,KCl(sat.)),we obtain the redox potential of triplet SnP to be E (P^+/P)～-0.33 V, E(P/P-)～+0.92 V.Matching this data with the redox potential of MV^(2+) and EDTA,we establish the fact that during the photolysis of the SnP/MV^(2+)/EDTA ternary system,both oxidative and reductive quenching are thermodynamically favorable processes.This is also the reason why the SnP sensitized reaction is much more efficient relative to other mesoporphyrin derivatives.展开更多
基金Project(2009K06_03) supported by the Scientific and Technological Program of Shaanxi Province,China
文摘Infrared emissivity was studied in Zn0.99M0.01O(M is Mn,Fe or Ni) and Zn1-xCoxO(x=0.01,0.02,0.03 and 0.04) powders synthesized by solid-state reaction at various temperatures.XRD patterns confirm the wurtzite structure of the prepared samples.No peaks of other phases arising from impurities are detected in Mn-and Co-doped ZnO,but the peaks of ZnFe2O4 and NiO are observed in Zn0.99Fe0.01O and Zn 0.99 Ni 0.01 O.The SEM observations indicate that with larger grain sizes than those of Zn0.99Fe0.01O and Zn0.99Ni0.01O,Co-doped ZnO exhibits smooth grain surfaces.The infrared absorption spectra show that infrared absorptions related to oxygen in Zn0.99M0.01O are much stronger than those in Co-doped ZnO.Co ions are dissolved into the ZnO lattice with Co2+ state from XPS spectra analysis.The infrared emissivity results imply that the emissivity of Zn0.99Ni0.01 O is the highest(0.829) and that of Zn 0.99 Co 0.01 O is the lowest(0.784) at 1 200 C.The emissivity of Zn0.99Co0.01O decreases to the minimum(0.752) at 1 150 C and then increases with growing calcination temperature.As the Co doping content grows,the emissivity of Co-doped ZnO calcined at 1 200 C falls to 0.758 in the molar fraction of 3% and then ascends.
文摘In DMSO/water(4:1),photolysis of the dihydroxy-Sn(IV)-rnesoporphyrin dimethyl ester (SnP)/methyl viologen(MV^(2+))/ethylene diamine tetraacetic acid(EDTA)ternary system produces methyl viologen cation radical with a quantum yield of 0.67,much higher than that of systems with other metal complexes of rnesoporphyrin dimethyl ester.Neither EDTA nor MV^(2+) quenches the stationary fluorescence of SnP,implying that the reaction does not take place at the singlet state.With flash photolysis we obtain the T-T absorption spectrum of SnP(λ_(max)-440 nm).By following the decay of this absorption,the triplet life time of SnP is estimated to be 41 μs.The life time is related to the concentration of either MV^(2+) or EDTA.Good linear relationships are obtained by plotting τ_0/τ vs.the concentration of MV^(2+) or EDTA(Stern-Volmer plot),from which we determine the quenching constants:k_q(MV^(2+))=5.5×10~7 mol^(-7) s^(-1);kq(EDTA)=2.7×10~7 mol^(-1),s^(-1).The data suggests that upon photolysis of the above ternary system,both oxidative quenching and reductive quenching of the triplet state of the sensitizer are occurring.From the measured phosphorescence spectrum(λ_(max) 704nm)and the ground state redox potentials (E_(1/2)^(red)～-0.84V,E_(1/2)^(ox)～ Ag/AgCl,KCl(sat.)),we obtain the redox potential of triplet SnP to be E (P^+/P)～-0.33 V, E(P/P-)～+0.92 V.Matching this data with the redox potential of MV^(2+) and EDTA,we establish the fact that during the photolysis of the SnP/MV^(2+)/EDTA ternary system,both oxidative and reductive quenching are thermodynamically favorable processes.This is also the reason why the SnP sensitized reaction is much more efficient relative to other mesoporphyrin derivatives.
