Transition Metal‐Involved Photon Upconversion

Abstract

Upconversion (UC) luminescence of lanthanide ions (Ln3+) has been extensively investigated for several decades and is a constant research hotspot owing to its fundamental significance and widespread applications. In contrast to the multiple and fixed UC emissions of Ln3+, transition metal (TM) ions, e.g., Mn2+, usually possess a single broadband emission due to its 3d 5 electronic configuration. Wavelength‐tuneable single UC emission can be achieved in some TM ion‐activated systems ascribed to the susceptibility of d electrons to the chemical environment, which is appealing in molecular sensing and lighting. Moreover, the UC emissions of Ln3+ can be modulated by TM ions (specifically d‐block element ions with unfilled d orbitals), which benefits from the specific metastable energy levels of Ln3+ owing to the well‐shielded 4f electrons and tuneable energy levels of the TM ions. The electric versatility of d 0 ion‐containing hosts (d 0 normally viewed as charged anion groups, such as MoO6 6‐ and TiO4 4‐) may also have a strong influence on the electric dipole transition of Ln3+, resulting in multifunctional properties of modulated UC emission and electrical behaviour, such as ferroelectricity and oxide‐ion conductivity. This review focuses on recent advances in the room temperature (RT) UC of TM ions, the UC of Ln3+ tuned by TM or d 0 ions, and the UC of d 0 ion‐centred groups, as well as their potential applications in bioimaging, solar cells and multifunctional devices.

Vanadium‐Sensitized Photon Upconversion of Lanthanide Ions (Er, Tm, Ho, Eu, Nd) in Yb3Al5O12 for In Vivo Imaging

“…It is known that upconversion process of lanthanide ions originates from 4f electron transitions, which is less sensitive to their surrounding chemical environment because of the shielding of outer 5s and 5p electronic shells. In contrast, the outermost d electrons of transition mental ions (with unfulfilled d orbitals) and d 0 ion‐centered anion groups are very sensitive to surrounding environment, which can be manipulated for sensitizing luminescence, showing great potential for enhancing upconversion emission . For instance, more than 15 times enhancement of red emission has been achieved in Er ions through transferring energy from Yb–Mn 2+ dimer to the high energy states of activators, when Mn 2+ was used as a sensitizer.…”

“…It is known that the doped V 5+ (d 0 ) ions in oxide host matrix could be viewed as charged anion groups (VO 4 3− ) with a d electron for the excited state owing to its high valence states . According to recent reports, VO 4 3− has the ground state 1 A 1 and the excited states 1 T 1 , 1 T 2 , 3 T 1 , and 3 T 2 .…”

Recent Progress and Emerging Applications of Rare Earth Doped Phosphor Materials for Dye‐Sensitized and Perovskite Solar Cells: A Review

“…DC/UC materials increases the surface‐area, light‐scattering, durability of a device and reduce recombination at electrolyte/photoanode interface . Mostly, Trivalent RE ions are extensively used for the above‐mentioned purpose due to their rich energy level structure and sharp emissions arising from their intra 4f–4f transitions and outermost filled 4f orbitals are shielded effectively by the 5s and 5p orbitals from the influence of host matrix . These ions have rich energy levels that allows them to absorb and emit photons from UV to IR region in solid host materials.…”

“…[28] Mostly, Trivalent RE ions are extensively used for the above-mentioned purpose due to their rich energy level structure and sharp emissions arising from their intra 4f-4f transitions and outermost filled 4f orbitals are shielded effectively by the 5s and 5p orbitals from the influence of host matrix. [29][30][31] These ions have rich energy levels that allows them to absorb and emit photons from UV to IR region in solid host materials. As a result, RE based DC/UC materials acts as a luminescent conversion materials (i,e conversion of UV to visible/NIR to visible light) which found their potential applications in photovoltaic technology.…”

Syntheses, Crystal Structures and Luminescent Properties of a Series of Ag-Ln Coordination Polymers

“…[6][7][8][9] However most of f-f transitions of Ln(III) ions are forbidden, their absorption coefficient is low and their luminescent intensity is weak. [10][11][12][13][14] Therefore, organic ligands absorbing UV light [15][16][17][18] and transition metal ions are introduced into the system to sensitize the luminescence of Ln(III) ions. [19][20][21][22][23][24] So far, there are many researches on the luminescent properties of 4d-4f complexes, and AgÀLn polymers have gained much attention due to two aspects.…”