CsPb(Cl 1−x Br x ) 3 perovskite nanocrystals (NCs) doped with Yb 3+ ions have recently attracted large attention for their applications in photovoltaics in view of the high quantum yield, exceeding 100% of Yb 3+ emission at ∼1 μm. In contrast, the particularly relevant Er 3+ emission at 1.5 μm in the third telecommunication window, of high interest in silicon integrated photonics, has been so far largely neglected in view of the weak emission performance displayed by Er 3+ -doped NCs. Comprehensive steady-state and time-resolved spectroscopic measurements provide insights into the underlying mechanisms of Yb 3+ and Er 3+ sensitization to rationalize the anomalous different behavior of these two emitters in singly doped NCs. We propose that single-photon excitation of two Yb 3+ ions possibly occurs through a transient internal redox mechanism in the perovskite host, while this pathway is unviable for Er 3+ . In turn, Yb 3+ -bridged Er 3+ sensitization, boosts the Er 3+ luminescence at ∼1.5 μm by 10 4 -fold compared to Er 3+ singly doped NCs, and a relative high quantum yield of ∼6% and extremely long lifetime (∼3 ms) are obtained. The resulting high Er 3+ excited state densities, combined with the large absorption cross-sections of the semiconducting CsPbCl 3 matrix make Er 3+ -doped perovskite promising innovative materials to realize photonic devices operating at telecommunication wavelengths.

The accessible emission spectral range of lead halide perovskite (LHP) CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) has remained so far limited to wavelengths below 1 μm, corresponding to...

Multiplex imaging in the red and near-infrared (NIR) should be an enabling tool for the real-time investigation of biological systems. Currently available emitters have short luminescent lifetimes, broad absorption and emission bands, and small Stokes shifts, which limits multiplexing in this region to two colors. NIR-emitting luminescent lanthanide (Ln) complexes carrying hydroporphyrin (chlorin) sensitizing antennae are excitable in the red through the narrow, intense and tunable chlorin absorptions. Both emission- and excitation-based multiplexing are possible, the former by exciting the same antenna appended to different Lns, the latter by attaching different chlorins with nonoverlapping absorptions to the same Ln. The combination of excitation and emission spectroscopies allows for the straightforward differentiation of up to four different complexes.

Two series of novel NIR‐emissive complexes of Nd3+, Sm3+, Er3+ and Yb3+ with two different β‐diketonate ligands (L1=4,4,4‐trifluoro‐1‐phenyl‐1,3‐butadione and L2=4,4,4‐trifluoro‐1‐(4‐chlorophenyl)‐1,3‐butadione) are reported. The neutral triphenylphosphine oxide (tppo) ligand was used to replace coordinated water molecules in the first coordination sphere of the as‐obtained [Ln(L1(2))3(H2O)2] complexes to afford water‐free [Ln(L1(2))3(tppo)2] molecular species. Upon replacement of water molecules by tppo units, the NIR emission lifetimes of the Nd3+, Er3+and Sm3+complexes increase by about one order of magnitude up to values of ≈9, 8 and 113 ms while Yb3+ complexes reach intrinsic quantum yields as high as to ΦYb=6.5 %., which are remarkably high for fully hydrogenated complexes. Vibrational quenching by CH and OH oscillators has been quantitatively assessed by implementing the Förster's model of resonance energy transfer on the basis of experimental data. This study demonstrates that highly efficient NIR‐emitting lanthanide complexes can be obtained with facile, cheap and accessible syntheses through a rational design.

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2D-layered Yb/Er homo- and heterometallic MOFs with the chlorocyananilate linker display long-lived NIR emission and high total quantum yields upon ligand excitation over the whole UV-visible spectrum.

In this work, we adopt a facile rare earth ions Ln 3+ (Ln = La, Gd, Y, Lu) substitution strategy to achieve the efficient red luminescence Sr 2 Ca 1−δ Ln δ WO 6 :Mn 4+ (δ = 0.10), which extremely improves the luminescence properties of luminescence-ignorable Sr 2 CaWO 6 :Mn 4+ . It is demonstrated that the substitution of Ln 3+ for Ca 2+ can stabilize the Mn in tetravalent state, which would like to occupy W 6+ site and generate the luminescence. It is also found that the emission profile of original Sr 2 CaWO 6 :Mn 4+ changes manifestly after different Ln 3+ ions substitution, which is mainly attributed to the synergistic effect of lattice distortion, Mn 4+ transition 2 E g → 4 A 2g and lattice vibration. Most fascinatingly, the Sr 2 Ca 0.9 Ln 0.1 WO 6 :0.005Mn 4+ (SC 0.9 Ln 0.1 WO:0.005Mn 4+ , Ln = La, Gd) show extraordinary luminescence thermal stability, whose integrated emission intensity still maintains about 95% (Gd, 96.8%; La, 94.8%) at 478 K of its original value at room temperature (298 K), much better than those in most reported Mn 4+ -activated oxide phosphors so far. It is confirmed that the traps may play an important role for this phenomenon. Best of all, this work gives us a facile strategy to achieve efficient Mn 4+ -activated red-emitting materials with extraordinary luminescence thermal stabilities derived from luminescence-ignorable ones.

Upon illumination by ultraviolet light, many animal species emit light through fluorescence processes arising from fluorophores embedded within their biological tissues. Fluorescence studies in living organisms are however relatively scarce and so far limited to the linear regime. Multiphoton excitation fluorescence analyses as well as non-linear optical techniques offer unique possibilities to investigate the effects of the local environment on the excited states of fluorophores. Herein these techniques are applied for the first time to the study of insects' natural fluorescence. The case of the male Hoplia coerulea beetle is investigated because the scales covering the beetle's elytra are known to possess an internal photonic structure with embedded fluorophores, which controls both the beetle's colouration and the fluorescence emission. An intense two-photon excitation fluorescence signal is observed, the intensity of which changes upon contact with water. A Third-Harmonic Generation signal is also detected, the intensity of which depends on the light polarisation state. The analysis of these non-linear optical and fluorescent responses unveils the multi-excited states character of the fluorophore molecules embedded in the beetle's elytra. The anisotropy of the photonic structure, which causes additional tailoring of the beetle's optical responses, is confirmed by circularly polarised light and non-linear optical measurements. arXiv:1801.07639v1 [physics.optics]