Effective colour modulation of upconversion emissions in lanthanide-doped nanomaterials becomes even more important for fundamental and applied research.Herein,on the one hand,by raising the content of doped Yb^(3+)fr...Effective colour modulation of upconversion emissions in lanthanide-doped nanomaterials becomes even more important for fundamental and applied research.Herein,on the one hand,by raising the content of doped Yb^(3+)from 10 mol%to 50 mol%,a significant increase of the red/green emission ratio from 4.0 to 68.2 is observed in K_(2)NaScF_(6):Yb/Er nanocrystals.This yellow to red colour change is attributed to the increased cross relaxation between Er^(3+)and Yb^(3+)caused by the increased Yb^(3+)amount,^(4) S_(3/2)(Er^(3+))^(+2) F7/2(Yb^(3+))→4 I13/2(Er^(3+))^(+2) F5/2(Yb^(3+)).On the other hand,the upconversion green and red emission of K_(2)NaScF_(6):Yb/Er(20/2 mol%)nanocrystals are intensified 10.6 and 8.8 folds,respectively,after an active shell(K_(2)NaScF_(6):Yb)is epitaxially grown,which are more effective than the7.4-and 6.4-fold enhancement from an inert shell(K_(2)NaScF_(6))growth.Moreover,the shell thickness from2.85 to 9.5 nm through controlling the molar ratio of shell-precursor to core from 1:2 to 3:1 can be easily realized.This study will provide more opportunities for the application of K_(2)NaScF_(6):Yb/Ln nanoparticles in varied fields such as theranostics,photovoltaics,and photocatalysis.展开更多
A novel K_(2)Nb_(2)O_(6)photocatalyst with pyrochlore structure has been synthesized via a facile one-pot hydrother-mal route with no aid of additives.The as-prepared samples were characterized by powder X-ray diffrac...A novel K_(2)Nb_(2)O_(6)photocatalyst with pyrochlore structure has been synthesized via a facile one-pot hydrother-mal route with no aid of additives.The as-prepared samples were characterized by powder X-ray diffraction,ultra-violet-visible spectroscopy and field emission scanning electron microscopy.The photocatalytic H_(2)evolution was performed in an aqueous methanol solution under UV light irradiation.The as-prepared K_(2)Nb_(2)O_(6)photocatalyst with pyrochlore structure showed higher H_(2)production activity than that of perovskite KNbO_(3)and commercial Nb2O5 powders in the absence of cocatalysts,due mainly to its unique crystal and energy band structures.The rate of H_(2)evolution can be significantly enhanced by loading of Pt nanoparticles.The highest H_(2)evolution rate of 121μmol/h was reached when 0.7 wt%Pt nanoparticles were used,which was about 20 times higher than that of pristine K_(2)Nb_(2)O_(6).展开更多
Red phosphor K_2LiAlF_6:Mn^(4+) has been synthesized by a cation-exchange method in HF solution. To optimize their optical properties, phosphors were synthesized using different reaction conditions. The K_2LiAlF_6:0.5...Red phosphor K_2LiAlF_6:Mn^(4+) has been synthesized by a cation-exchange method in HF solution. To optimize their optical properties, phosphors were synthesized using different reaction conditions. The K_2LiAlF_6:0.5%Mn^(4+) synthesized at 20℃ for4 h shows the highest luminescence intensity. The temperature-dependent emission intensity of the phosphor was investigated,and it was found to exhibit good thermal stability, making it a promising red phosphor candidate for warm WLEDs.展开更多
基金Project supported by the National Natural Science Foundation of China(21871137,21671101)the Research Fund for the Doctoral Program of Liaocheng University(318051832)the Innovation Team of Higher Educational Science and Technology Program of Shandong Province(2019KIA025)。
文摘Effective colour modulation of upconversion emissions in lanthanide-doped nanomaterials becomes even more important for fundamental and applied research.Herein,on the one hand,by raising the content of doped Yb^(3+)from 10 mol%to 50 mol%,a significant increase of the red/green emission ratio from 4.0 to 68.2 is observed in K_(2)NaScF_(6):Yb/Er nanocrystals.This yellow to red colour change is attributed to the increased cross relaxation between Er^(3+)and Yb^(3+)caused by the increased Yb^(3+)amount,^(4) S_(3/2)(Er^(3+))^(+2) F7/2(Yb^(3+))→4 I13/2(Er^(3+))^(+2) F5/2(Yb^(3+)).On the other hand,the upconversion green and red emission of K_(2)NaScF_(6):Yb/Er(20/2 mol%)nanocrystals are intensified 10.6 and 8.8 folds,respectively,after an active shell(K_(2)NaScF_(6):Yb)is epitaxially grown,which are more effective than the7.4-and 6.4-fold enhancement from an inert shell(K_(2)NaScF_(6))growth.Moreover,the shell thickness from2.85 to 9.5 nm through controlling the molar ratio of shell-precursor to core from 1:2 to 3:1 can be easily realized.This study will provide more opportunities for the application of K_(2)NaScF_(6):Yb/Ln nanoparticles in varied fields such as theranostics,photovoltaics,and photocatalysis.
基金Financial support from the Ministry of Science and Technology of China(Nos.2014CB239402 and 2013CB834505)the National Natural Science Founda-tion of China(Nos.51322213,21301183,20901081,51172245,and 91127005)+2 种基金Knowledge Innovation Pro-ject of the Chinese Academy of Sciences(KGCX2-EW-311-3)the Beijing Natural Science Foundation(Nos.2112042 and 2122054)the 100 Talents Program of the Chinese Academy of Sciences,and Scientific Research Foundation for Returned Scholars of Ministry of Educa-tion of China is gratefully acknowledged.
文摘A novel K_(2)Nb_(2)O_(6)photocatalyst with pyrochlore structure has been synthesized via a facile one-pot hydrother-mal route with no aid of additives.The as-prepared samples were characterized by powder X-ray diffraction,ultra-violet-visible spectroscopy and field emission scanning electron microscopy.The photocatalytic H_(2)evolution was performed in an aqueous methanol solution under UV light irradiation.The as-prepared K_(2)Nb_(2)O_(6)photocatalyst with pyrochlore structure showed higher H_(2)production activity than that of perovskite KNbO_(3)and commercial Nb2O5 powders in the absence of cocatalysts,due mainly to its unique crystal and energy band structures.The rate of H_(2)evolution can be significantly enhanced by loading of Pt nanoparticles.The highest H_(2)evolution rate of 121μmol/h was reached when 0.7 wt%Pt nanoparticles were used,which was about 20 times higher than that of pristine K_(2)Nb_(2)O_(6).
基金the National Basic Research Program of China(Grant No.2014CB643801)the National Natural Science Foundation of China(Grant Nos.51572302 and 21271191)+4 种基金the Joint Funds of the National Natural Science Foundation of China and Guangdong Province(Grant No.U1301242)Teamwork Projects of Guangdong Natural Science Foundation(Grant No.S2013030012842)Guangdong Science&Technology Project(Grant No.2015B090926011)the Natural Science Foundation of Guangdong Province(Grant No.2014A030313114)China Postdoctoral Science Foundation(Grant No.2014M562237)
文摘Red phosphor K_2LiAlF_6:Mn^(4+) has been synthesized by a cation-exchange method in HF solution. To optimize their optical properties, phosphors were synthesized using different reaction conditions. The K_2LiAlF_6:0.5%Mn^(4+) synthesized at 20℃ for4 h shows the highest luminescence intensity. The temperature-dependent emission intensity of the phosphor was investigated,and it was found to exhibit good thermal stability, making it a promising red phosphor candidate for warm WLEDs.
