Synthetic hackmanites, Na8Al6Si6O24(Cl,S)2, showing efficient purple tenebrescence and blue/white persistent luminescence were studied using different spectroscopic techniques to obtain a quantified view on the storage and release of optical energy in these materials. The persistent luminescence emitter was identified as impurity Ti(3+) originating from the precursor materials used in the synthesis, and the energy storage for persistent luminescence was postulated to take place in oxygen vacancies within the aluminosilicate framework. Tenebrescence, on the other hand, was observed to function within the Na4(Cl,S) entities located in the cavities of the aluminosilicate framework. The mechanism of persistent luminescence and tenebrescence in hackmanite is presented for the first time.

We report blue, green, and red upconversion emissions with strongly angular-dependent intensities for a new type of hybrid (Y,Yb,Er)–pyrazine thin films realized using the atomic/molecular layer deposition thin-film fabrication technology. The luminescence emissions in our amorphous (Y,Yb,Er)–pyrazine thin films of a controllable nanothickness originate from three- and two-photon NIR-to-vis excitation processes. In addition to shielding the lanthanide ions from nonradiative de-excitation, the network of interconnected organic molecules serves as an excellent matrix for the Yb3+-to-Er3+ excitation energy transfer. This suggests a new approach to achieve efficient upconverting molecular materials with the potential to be used for next-generation medical diagnostics, waveguides, and surface-sensitive detectors.

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Here we show that the backbone of the organic ligand has a profound impact on the luminescence characteristics of lanthanide-organic materials. We employ the emerging atomic/molecular layer deposition (ALD/MLD) technique to deposit europium-based thin films where the organic ligands vary in terms of the number of aromatic rings in their backbone (benzene, naphthalene and anthracene). Enlarging the backbone shifts the excitation towards visible wavelengths, but it simultaneously decreases the emission intensity. Moreover, for the Eu-terephthalate films with the single benzene ring as the organic backbone, we investigate the effects of diluting the Eu3+ concentration with Y3+ to reveal that the emission intensity is optimized around 12% Eu3+ concentration. Interestingly, such a dependence of luminescence intensity on the concentration of emitting species suggests that our (Eu,Y)-organic thin films behave more like ionic phosphors than discrete metal–ligand molecules. Graphical abstract

Near-infrared to green and red up-conversion is reported for a new type of hybrid (Yb,Er)-IR-806 films prepared using the atomic/molecular layer deposition (ALD/MLD) thin-film fabrication technology. These amorphous films can be realized in controllable nanothicknesses and they show an exceptionally wide absorption band in the near-infrared region. The films exhibit a highly local upconversion excitation process, which suggests strong potential for use as e.g. temperature sensors with Ångström scale surface resolution.