Nano Lett 2007, 7:1081–1085.CrossRef 32. Li J, Zeng HC: Hollowing Sn-doped TiO 2 nanospheres via Ostwald ripening. J Am Chem Soc 2007, 129:15839–15847.CrossRef 33. Walter MG, Warren EL, McKone JR, Boettcher SW, Mi Q, Santori A, Lewis NS: Solar water splitting cells. Chem Rev 2010, 110:6446–6473.CrossRef 34. Lin

YJ, Zhou S, Sheehan SW, Wang DW: Nanonet-based hematite heteronanostructures for efficient solar water splitting. Etoposide nmr J Am Chem Soc 2011, 133:2398–2401.CrossRef 35. Janotti A, Varley JB, Rinke P, Umezawa N, Kresse G, Van de Walle CG: Hybrid functional studies of the oxygen vacancy in TiO 2 . Phys Rev B 2010, 81:085212.CrossRef Competing interests The authors declare that they have no competing interests. Authors’ contributions BS carried out experimental work, analyzed the data, and prepared the manuscript. TLS participated in the studies and supervised the research work. ZCP improved the manuscript. WJS Dactolisib clinical trial and TJ participated in the experimental work. GLL participated in the studies, improved the manuscript, and supervised the research work. All authors read and approved the final manuscript.”
“Background Rare earth-doped

crystals are widely used in many applications that require sources of visible and near-infrared radiation. However, when doped into conventional commercially available crystals such as YAG or YLF, rare earth ions do not radiate efficiently at wavelengths much longer than 3 μm. The mid-infrared Etomidate range (3 to 10 μm) is not directly accessible using host crystals that have tightly bound oxygen or fluorine ions. The reasons are the relatively high energies for lattice phonons in these crystals and the fact that the rates for non-radiative multi-phonon relaxation increase exponentially as the energies of the electronic transitions are reduced and fewer phonons are required to bridge the gap. The demand for mid-infrared sources

and applications in gas detection, remote sensing, IR spectroscopy, and infrared countermeasures has motivated research on alternative methods for generating mid-infrared. Quantum cascade lasers [1], thermal tungsten filaments, small bandgap III-V or II-VI optically pumped semi-conductors [2, 3], rare earth-doped chalcogenide glasses [4], oxide glasses [5], and rare earth-doped fluoride crystals [6] have all been used as sources of mid-infrared. This paper discusses an approach to generating mid-infrared that uses rare earth-doped crystals with reduced phonon energies. It focuses specifically on crystals sensitized for diode pumping with the trivalent rare earth ion thulium (Tm3+).