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Constructing core-shell structures can effectively reduce the surface quenching effect of luminescent materials, which becomes an effective method to enhance upconversion luminescence. In this work, a series of NaLnF4@NaLnF4 (Ln = Y3+, Yb3+, Ho3+) core-shell microcrystals is successfully synthesized based on epitaxial growth technology, thereby enhancing and regulating the upconversion emission of Ho3+ ions. The results of the XRD and SEM indicate that the NaLnF4@NaLnF4 core-shell microcrystal possesses a pure hexagonal-phase crystal structure with a rod-like shape. Meanwhile, it is found that the epitaxial growth direction of the micro-shell is not affected by the crystal characteristics in the core, but determined by the crystal characteristics of the shell. Under 980 nm near-infrared laser excitation, the upconversion luminescence properties of single microrods with different core-shell structures are investigated via a confocal microscope spectroscopy. It is found that in the NaLnF4 micro-crystal, the coated NaYF4 inert shell can also effectively reduce the quenching effect on the surface of the micro-crystal for enhancing upconversion emission. When the Yb3+ ions are introduced into NaYF4 or NaYbF4 active shell that is coated, the Yb3+ ions in the shell can effectively transfer excitation energy to Yb3+ in the core through energy migration, and then establish new energy transfer channels, thereby realizing the Ho3+ ion luminescence enhancement. For NaHoF4@NaYbF4 core-shell microrods, the Yb3+ in the shell can transfer more excitation energy to Ho3+ ions at the adjacent interface for enhancing the overall luminescence intensity, and its higher red-green ratio is mainly due to the cross-relaxation process occurring between the Ho3+ ions at high doping concentration of Ho3+ in the NaHoF4 core. Meanwhile, the luminescence process of the micron core-shell system is further confirmed based on the luminescence characteristics of different structures and the dynamic luminescence process. It can be seen that constructing different micron core-shell structures and introducing sensitizing ions, can not only effectively enhance the luminous intensity of the micron materials, but also adjust the output color. Therefore, this research is an important experimental reference for enhancing the luminous intensity of the micron system and the precise adjustment of luminescence, and can effectively expand the applications of micron crystals in the fields of displays, micron lasers and anti-counterfeiting.
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Keywords:
- upconversion luminescence /
- micron core-shell structure /
- luminescence regulation /
- energy transfer /
- single particle
[1] Deng R R, Qin F, Chen R F, Huang W, Hong M H, Liu X G 2015 Nat. Nanotechnol. 10 237Google Scholar
[2] Gong G, Song Y, Tan H H, Xie S W, Zhang C F, Xu L J, Xu J X, Zheng J 2019 Compos. Part B-Eng. 179 107504Google Scholar
[3] Park Y I, Lee K T, Suh Y D, Hyeon T H 2015 Chem. Soc. Rev. 44 1302Google Scholar
[4] Zheng W, Huang P, Tu D T, Ma E, Zhu H M, Chen X Y 2015 Chem. Soc. Rev. 44 1379Google Scholar
[5] Wang J, Wei T, Li X Y, Zhang B H, Wang J X, Huang C, Yuan Q 2014 Angew. Chem. 126 1642Google Scholar
[6] Wang Y H, Ohwaki. J 1993 Appl. Phys. Lett. 63 3268Google Scholar
[7] Rakov N, Maciel G S, Sundheimer M L, Menezes L D S, Gomes A S L, Messaddeq Y, Cassanjes F C, Poirier G, Ribeiro S J L 2002 J. Appl. Phys. 92 6337Google Scholar
[8] Su Q Q, Han S Y, Xie X J, Zhu H M, Chen H Y, Chen C K, Liu R S, Chen X Y, Wang F, Liu X G 2012 J. Am. Chem. Soc. 134 20849Google Scholar
[9] Wang Y D, Yang Z W, Ma Y J, Chai Z Z, Qiu J B, Song Z G 2017 J. Mater. Chem. C 5 8535Google Scholar
[10] Dong J, Gao W, Han Q Y, Wang Y K, Qi J X, Yan X W, Sun M T 2019 Rev. Phys. 4 100026Google Scholar
[11] Tian Q, Tao K, Sun K 2013 Micro Nano Lett. 8 731Google Scholar
[12] Homann C, Krukewitt L, Frenzel F, Grauel B, Würth C, Resch-Genger U, Haase M 2018 Angew. Chem. Int. Ed. 57 8765Google Scholar
[13] Choi J E, Kim D, Jang H S 2019 Chem. Commun. 55 2261Google Scholar
[14] Ju D D, Song F, Han Y D, Zhang J, Song F F, Zhou A H, Huang W, Zadkov V 2019 J. Alloy. Compd. 787 1120Google Scholar
[15] Jiao X F, Ye W H, Huang Q Y, Luo J, Yu L L, Liu X T 2020 J. Rare Earth 38 697Google Scholar
[16] Gao W, Sun Z Y, Han Q Y, Han S S, Cheng X T, Wang Y K, Yan X W, Dong J 2021 J. Alloy. Compd. 857 157578Google Scholar
[17] Gai S L, Li C X, Yang P P, Lin J 2014 Chem. Rev. 114 2343Google Scholar
[18] Gao W, Zheng H R, Han Q Y, He E J, Wang R B 2014 CrystEngComm. 16 6697Google Scholar
[19] 高伟, 王博扬, 孙泽煜, 高露, 张晨雪, 韩庆艳, 董军 2020 69 034207Google Scholar
Gao W, Wang B Y, Sun Z Y, Gao L, Zhang C X, Han Q Y, Dong J 2020 Acta Phys Sin 69 034207Google Scholar
[20] Gao D L, Zhang X Y, Gao W, 2013 ACS Appl. Mat. Inter. 5 9732Google Scholar
[21] Zhang Y H, Huang L, Liu X G 2016 Angew. Chem. Int. Ed. 55 5718Google Scholar
[22] Chen B, Sun T Y, Qiao X S, Fan X P, Wang F 2015 Adv. Opt. Mater. 3 1577Google Scholar
[23] Tong L M, Lu E, Pichaandi J, Zhao G Y, Winnik M A 2016 J. Phys. Chem. C 120 6269
[24] Zhang Y H, Huang L, Liu X G, 2016 Angew. Chem. 128 5812Google Scholar
[25] 董军, 张晨雪, 程小同, 邢宇, 韩庆艳, 严学文, 祁建霞, 刘继红, 杨祎, 高伟 2021 70 154208Google Scholar
Dong J, Zhang C X, Cheng X T, Xing Y, Han Q Y, Yan X W, Qi J X, Liu J H, Yang Y, Gao W 2021 Acta Phys. Sin. 70 154208Google Scholar
[26] Gao W, Zheng H R, Han Q Y, He E J, Gao F Q, Wang R B 2014 J. Mater. Chem. C 2 5327Google Scholar
[27] Sangeetha N M, van Veggel F C J M 2009 J. Phys. Chem. C 113 14702Google Scholar
[28] Pilch A, Würth C, Kaiser M, Wawrzyńczyk D, Kurnatowska M, Arabasz S, Prorok K, Samoć M, Strek W, Resch-Genger U, Bednarkiewicz A 2017 Small 13 1701635Google Scholar
[29] Gao W, Kong X Q, HanQ Y, ChenY, ZhangJ, Zhao X, Yan X W, Liu J H, Shi J, Dong J 2018 J. Lumin. 202 381Google Scholar
[30] Gao D L, Zhang X Y, Zheng H R, Gao W, He E J, 2013 J. Alloy. Compd. 554 395Google Scholar
[31] Shi F, Wang J S, Zhai X S, Zhao D, Qin W P, 2011 CrystEngComm 13 3782Google Scholar
[32] Jiang Y F, Shen R S, Li X P, Zhang J S, Zhong H, Tian Y, Sun J S, Cheng L H, Zhong H Y, Chen B J 2012 Ceram. Int. 38 5045Google Scholar
[33] Auzel F 2004 Chem. Rev 104 139Google Scholar
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图 4 在980 nm激发下, 单个NaYF4:20%Yb3+/2%Ho3+及其核壳微米棒的(a)上转换发射光谱, (b)蓝光、绿光和红光的发射峰面积, (c)红绿比和(d) CIE 色度坐标图
Figure 4. (a) The UC emission spectra, (b) the peak area of the bule, green and red emission intensity, (c) R/G ratio and (d) CIE chromaticity diagram of the single NaYF4:20%Yb3+/2%Ho3+ microrod with corresponding CS microrod under the excitation of a 980 nm near-infrared (NIR) laser.
图 5 在980 nm激光激发下, (a) 单颗粒NaYbF4:2%Ho3+ 和(b) NaHoF4微米棒及其相应核壳微米棒的上转换(UC)发射光谱(插图为其相应的红绿比及发光照片)
Figure 5. The UC emission spectra of the single (a) NaYbF4:2%Ho3+ and (b) NaHoF4 microrod with corresponding CS microrod under the excitation of a 980 nm NIR laser (The insert is corresponding optical micrographs and R/G ratio).
图 7 单颗粒微米棒与泵浦功率的依赖关系 (a), (b) NaYF4:20%Yb3+/2%Ho3+微米棒; (c), (d) NaYF4:20%Yb3+/2%Ho3+@NaYF4:40%Yb3+核壳微米棒; (e), (f) NaYbF4:2%Ho3+@NaYF4核壳微米棒
Figure 7. Pump power dependences of the single-particle microrod: (a), (b) NaYF4:20%Yb3+/2%Ho3+ microrod; (c), (d) NaYF4:20%Yb3+/2%Ho3+@NaYF4 CS microrod; (e), (f) NaYbF4:2%Ho3+@NaYF4 CS microrod.
图 8 在 980 nm脉冲激光激发下, 不同的(a), (b) NaYF4及(c), (d) NaHoF4核壳微米棒中Ho3+离子5F5能级(b), (d)及其5S2能级(a), (c)的辐射衰减寿命曲线图
Figure 8. Decay curves of the (b), (d) 5F5 and (a), (c) 5S2 levels in (a), (b) NaYF4 and (c), (d) NaHoF4 microrod with corresponding CS microrods under the excitation of a 980 nm NIR pulse laser.
表 1 水热法制备微米晶体所需药品的详细参数
Table 1. Detailed parameters of the chemical reagents required for the preparation of microcrystals by hydrothermal method.
样品 EDTA
/gRE(NO3)3/
mmolNaF/
mmolNH4HF2/mmol NaYF4:20%Yb3+/
2%Ho3+0.282 0.75 2.5 3 NaYbF4:2%Ho3+ 0.282 0.75 2.5 3 NaHoF4 0.282 0.75 2.5 3 表 2 水热法制备微米核壳晶体的所需药品的详细参数
Table 2. Detailed parameters of the chemical reagents required for the preparation of the core-shell microcrystal by hydrothermal method.
样品 Seed crystals quality/g EDTA/mmol RE(NO3)3/mmol NaF/mmol NH4HF2/mmol NaYF4:20%Yb3+/2%Ho3+@NaYF4 0.1494 0.75 0.75 2.5 3 NaYF4:20%Yb3+/2%Ho3+@NaYbF4 0.1494 0.75 0.75 2.5 3 NaYbF4:2%Ho3+@NaYF4 0.1228 0.75 0.50 2.5 3 NaHoF4@NaYF4 0.1995 0.75 0.75 2.5 3 NaHoF4@NaYF4:20%Yb3+ 0.1995 0.75 0.75 2.5 3 NaHoF4@NaYbF4 0.1995 0.75 0.75 2.5 3 表 3 在980 nm 脉冲激发光下, NaYF4与NaHoF4核壳微米棒核壳纳米晶体中的Ho3+离子5F5能级及5S2能级的辐射寿命值
Table 3. Luminescence lifetimes of the 5F5 and 5S2 levels in NaYF4 and NaHoF4 microrod with corresponding CS microrods under the excitation of a 980 nm NIR pulse laser.
Samples Lifetime/μs 5S2: 541 nm 5F5: 645 nm NaYF4:20%Yb3+/2%Ho3+ 201.3 367.7 NaYF4:20%Yb3+/2%Ho3+@
NaYF4298.6 445.1 NaYF4:20%Yb3+/2%Ho3+@
NaYF4:20%Yb3+380.4 529.3 NaYF4:20%Yb3+/2%Ho3+@
NaYF4:40%Yb3+472.3 682.1 NaYF4:20%Yb3+/2%Ho3+@
NaYF4:80%Yb3+416.5 573.4 NaHoF4@NaYF4:20%Yb3+ 167.4 247.3 NaHoF4@NaYbF4 236.6 318.6 -
[1] Deng R R, Qin F, Chen R F, Huang W, Hong M H, Liu X G 2015 Nat. Nanotechnol. 10 237Google Scholar
[2] Gong G, Song Y, Tan H H, Xie S W, Zhang C F, Xu L J, Xu J X, Zheng J 2019 Compos. Part B-Eng. 179 107504Google Scholar
[3] Park Y I, Lee K T, Suh Y D, Hyeon T H 2015 Chem. Soc. Rev. 44 1302Google Scholar
[4] Zheng W, Huang P, Tu D T, Ma E, Zhu H M, Chen X Y 2015 Chem. Soc. Rev. 44 1379Google Scholar
[5] Wang J, Wei T, Li X Y, Zhang B H, Wang J X, Huang C, Yuan Q 2014 Angew. Chem. 126 1642Google Scholar
[6] Wang Y H, Ohwaki. J 1993 Appl. Phys. Lett. 63 3268Google Scholar
[7] Rakov N, Maciel G S, Sundheimer M L, Menezes L D S, Gomes A S L, Messaddeq Y, Cassanjes F C, Poirier G, Ribeiro S J L 2002 J. Appl. Phys. 92 6337Google Scholar
[8] Su Q Q, Han S Y, Xie X J, Zhu H M, Chen H Y, Chen C K, Liu R S, Chen X Y, Wang F, Liu X G 2012 J. Am. Chem. Soc. 134 20849Google Scholar
[9] Wang Y D, Yang Z W, Ma Y J, Chai Z Z, Qiu J B, Song Z G 2017 J. Mater. Chem. C 5 8535Google Scholar
[10] Dong J, Gao W, Han Q Y, Wang Y K, Qi J X, Yan X W, Sun M T 2019 Rev. Phys. 4 100026Google Scholar
[11] Tian Q, Tao K, Sun K 2013 Micro Nano Lett. 8 731Google Scholar
[12] Homann C, Krukewitt L, Frenzel F, Grauel B, Würth C, Resch-Genger U, Haase M 2018 Angew. Chem. Int. Ed. 57 8765Google Scholar
[13] Choi J E, Kim D, Jang H S 2019 Chem. Commun. 55 2261Google Scholar
[14] Ju D D, Song F, Han Y D, Zhang J, Song F F, Zhou A H, Huang W, Zadkov V 2019 J. Alloy. Compd. 787 1120Google Scholar
[15] Jiao X F, Ye W H, Huang Q Y, Luo J, Yu L L, Liu X T 2020 J. Rare Earth 38 697Google Scholar
[16] Gao W, Sun Z Y, Han Q Y, Han S S, Cheng X T, Wang Y K, Yan X W, Dong J 2021 J. Alloy. Compd. 857 157578Google Scholar
[17] Gai S L, Li C X, Yang P P, Lin J 2014 Chem. Rev. 114 2343Google Scholar
[18] Gao W, Zheng H R, Han Q Y, He E J, Wang R B 2014 CrystEngComm. 16 6697Google Scholar
[19] 高伟, 王博扬, 孙泽煜, 高露, 张晨雪, 韩庆艳, 董军 2020 69 034207Google Scholar
Gao W, Wang B Y, Sun Z Y, Gao L, Zhang C X, Han Q Y, Dong J 2020 Acta Phys Sin 69 034207Google Scholar
[20] Gao D L, Zhang X Y, Gao W, 2013 ACS Appl. Mat. Inter. 5 9732Google Scholar
[21] Zhang Y H, Huang L, Liu X G 2016 Angew. Chem. Int. Ed. 55 5718Google Scholar
[22] Chen B, Sun T Y, Qiao X S, Fan X P, Wang F 2015 Adv. Opt. Mater. 3 1577Google Scholar
[23] Tong L M, Lu E, Pichaandi J, Zhao G Y, Winnik M A 2016 J. Phys. Chem. C 120 6269
[24] Zhang Y H, Huang L, Liu X G, 2016 Angew. Chem. 128 5812Google Scholar
[25] 董军, 张晨雪, 程小同, 邢宇, 韩庆艳, 严学文, 祁建霞, 刘继红, 杨祎, 高伟 2021 70 154208Google Scholar
Dong J, Zhang C X, Cheng X T, Xing Y, Han Q Y, Yan X W, Qi J X, Liu J H, Yang Y, Gao W 2021 Acta Phys. Sin. 70 154208Google Scholar
[26] Gao W, Zheng H R, Han Q Y, He E J, Gao F Q, Wang R B 2014 J. Mater. Chem. C 2 5327Google Scholar
[27] Sangeetha N M, van Veggel F C J M 2009 J. Phys. Chem. C 113 14702Google Scholar
[28] Pilch A, Würth C, Kaiser M, Wawrzyńczyk D, Kurnatowska M, Arabasz S, Prorok K, Samoć M, Strek W, Resch-Genger U, Bednarkiewicz A 2017 Small 13 1701635Google Scholar
[29] Gao W, Kong X Q, HanQ Y, ChenY, ZhangJ, Zhao X, Yan X W, Liu J H, Shi J, Dong J 2018 J. Lumin. 202 381Google Scholar
[30] Gao D L, Zhang X Y, Zheng H R, Gao W, He E J, 2013 J. Alloy. Compd. 554 395Google Scholar
[31] Shi F, Wang J S, Zhai X S, Zhao D, Qin W P, 2011 CrystEngComm 13 3782Google Scholar
[32] Jiang Y F, Shen R S, Li X P, Zhang J S, Zhong H, Tian Y, Sun J S, Cheng L H, Zhong H Y, Chen B J 2012 Ceram. Int. 38 5045Google Scholar
[33] Auzel F 2004 Chem. Rev 104 139Google Scholar
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