Understanding the effect of Mn²⁺ on Yb³⁺/Er³⁺ upconversion and obtaining a maximum upconversion fluorescence enhancement in inert-core/active-shell/inert-shell structures

Abstract

NaYF4@NaYF4:Er3+/Yb3+/Mn2+@NaYF4 (C/Sd/S) nanoparticles were synthesized which show an obvious efficiency enhancement of red upconversion emission.

Post annealing induced manipulation of phase and upconversion luminescence of Cr3+ doped NaYF4:Yb,Er crystals

“…[24][25][26] On the other hand, various methods such as core-shell structure, varying the crystal phase, incorporation of RE 3+ ion or non RE 3+ ion, metal enhanced uorescence etc., have been utilized to improve the luminescence efficiency of the upconversion materials. [27][28][29] It has been proved that changing the crystal eld of the host matrix can modulate the electron transition probabilities of RE 3+ ion and thus control the emission properties of the upconversion materials. 30 The size and dipole polarizability of lanthanide dopant can be controlled by simultaneous doping with non-RE 3+ ions of lower or higher ionic radius.…”

“…39 Even though there are some reports that manifest the enhancement in the red and green emission with addition of very low concentration of co-dopant like Cr 3+ or Mn 2+ , majority of the studies reported till date utilize high concentrations of the co-dopants. 28,39,45,46 To best of our knowledge, the samples investigated here, the co-dopant Cr 3+ (for the mol%: 0%, 5%, 10%, 15% and 20%) induced changes in the crystalline size, phase, upconversion luminescence, laser power dependent emission behaviour of NaY (80Àn%) F 4 :Yb (17%) ,Er (3%) Cr (n%) (n ¼ 0, 5, 10, 15, 20 mol%) has never been reported so far for the samples prepared via co-precipitation method. Further, the role of post-annealing at different temperatures (200 C, 400 C and 600 C) on the aforementioned properties are not explored.…”

Luminescent Lifetime Regulation of Lanthanide-Doped Nanoparticles for Biosensing

“…Therefore, the increased population density of Mn 2+ caused the decreased radiative transition rate of Er 3+ ( 4 S 3/2 and 2 H 11/2 ) turning down to ground state, resulting in an enhancement of red emission due to energy transfer from Mn 2+ ( 4 T 1 ) to Er 3+ ( 4 F 9/2 ) ( Figure 4 a). Meanwhile, the increased lifetime of Er 3+ at 650 nm also verified the role of Mn 2+ in energy transfer trace according to the decay curves of various content of Mn 2+ (0%, 10%, 20%, 30%) ( Figure 4 b) [ 34 ].…”

“…Amongst them, the C/S d /S structure has two layers of NaYF 4 interface contacting the active shell, which reduced surface defects and thus enhanced the upconversion process. Therefore, the lifetime can be prolonged by reducing energy defects and increasing the energy transfer rate [ 34 ].…”

Role of Mn2+ Doping in the Preparation of Core-Shell Structured Fe3O4@upconversion Nanoparticles and Their Applications in T1/T2-Weighted Magnetic Resonance Imaging, Upconversion Luminescent Imaging and Near-Infrared Activated Photodynamic Therapy

“…So far, several different methods have been developed to prepare MUCNPs, such as using mesoporous silica as anintermediate layer to combine UCNPs with Fe 3 O 4 NPs [ 4 , 5 , 6 ], polymer encapsulation [ 7 , 8 ], ligand crosslinking [ 9 , 10 ] and direct seed-nucleation [ 11 , 12 , 13 ]. This seed-growth method can be applied to construct MUCNPs by using one part as a seed onto which a second component can nucleate and grow [ 14 , 15 ].…”