Transition metal-lanthanide upconversion

Table 2. Transition metal ions in doped halide lattices for which upconversion luminescence has been demonstrated, including relevant mechanistic and electronic-structural information. The lightest and heaviest lanthanides showing single-ion upconversion are also listed. Adapted from [17] ...

SuyvCT JF, Aebischer A, Biner D, Gemer P, Grimm J, Heer S, Kramer J, Reinhard C, Giidel HU (2005) Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion. Opt Mater 27 1111-1130... 

Giidel and coworkers have exploited an alternative upconversion approach by employing lanthanide-transition metal (TM) donor-acceptor systems. The selection of the host lattice can optimize the luminescence properties of the... 

Pollnau M, Gamelin DR, Liithi SR, Giidel HU (2000) Power dependence of upconversion luminescence in lanthanide and transition metal systems. Phys Rev B 61 3337-3346... 

The term upconversion describes an effect [1] related to the emission of anti-Stokes fluorescence in the visible spectral range following excitation of certain (doped) luminophores in the near infrared (NIR). It mainly occurs with rare-earth doped solids, but also with doped transition-metal systems and combinations of both [2, 3], and relies on the sequential absorption of two or more NIR photons by the dopants. Following its discovery [1] it has been extensively studied for bulk materials both theoretically and in context with uses in solid-state lasers, infrared quantum counters, lighting or displays, and physical sensors, for example [4, 5]. Substantial efforts also have been made to prepare nanoscale materials that show more efficient upconversion emission. Meanwhile, numerous protocols are available for making nanoparticles, nanorods, nanoplates, and nanotubes. These include thermal decomposition, co-precipitation, solvothermal synthesis, combustion, and sol-gel processes [6], synthesis in liquid-solid-solutions [7, 8], and ionothermal synthesis [9]. Nanocrystal materials include oxides of zirconium and titanium, the fluorides, oxides, phosphates, oxysulfates, and oxyfluoiides of the trivalent lanthanides (Ln ), and similar compounds that may additionally contain alkaline earth ions. Wang and Liu [6] have recently reviewed the theory of upconversion and the common materials and methods used. 

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