Photoluminescent lanthanide-organic frameworks (Ln-MOFs) were printed onto plastic and paper foils with a conventional inkjet printer. Ln-MOF inks were used to reproduce color images that can only be observed under UV light irradiation. This approach opens a new window for exploring Ln-MOF materials in technological applications, such as optical devices (e.g., lab-on-a-chip), as proof of authenticity for official documents.

In this work, we report a theoretical and experimental investigation of the energy transfer mechanism in two isotypical 2D coordination polymers, ∞ [(Tb 1−x Eu x )(DPA)(HDPA)], where H 2 DPA is pyridine 2,6-dicarboxylic acid and x = 0.05 or 0.50. Emission spectra of ∞ [(Tb 0.95 Eu 0.05 )(DPA)(HDPA)] and ∞ [(Tb 0.5 Eu 0.5 )(DPA)-(HDPA)], (1) and (2), show that the high quenching effect on Tb 3+ emission caused by Eu 3+ ion indicates an efficient Tb 3+ →Eu 3+ energy transfer (ET). The k ET of Tb 3+ → Eu 3+ ET and rise rates (k r ) of Eu 3+ as a function of temperature for (1) are on the same order of magnitude, indicating that the sensitization of the Eu 3+ 5 D 0 level is highly fed by ET from the 5 D 4 level of Tb 3+ ion. The η ET and R 0 values vary in the 67− 79% and 7.15 to 7.93 Å ranges. Hence, Tb 3+ is enabled to transfer efficiently to Eu 3+ that can occupy the possible sites at 6.32 and 6.75 Å. For (2), the ET processes occur on average with η ET and R 0 of 97% and 31 Å, respectively. Consequently, Tb 3+ ion is enabled to transfer energy to Eu 3+ localized at different layers. The theoretical model developed by Malta was implemented aiming to insert more insights about the dominant mechanisms involved in the ET between lanthanides ions. Calculated single Tb 3+ → Eu 3+ ETs are three orders of magnitude inferior to those experimentally; however, it can be explained by the theoretical model that does not consider the role of phonon assistance in the Ln 3+ → Ln 3+ ET processes. In addition, the Tb 3+ → Eu 3+ ET processes are predominantly governed by dipole−dipole (d−d) and dipole−quadrupole (d−q) mechanisms.

Temperature measurements ranging from a few degrees to a few hundreds of Kelvin are of great interest in the fields of nanomedicine and nanotechnology. Here, we report a new ratiometric luminescent thermometer using thermally excited state absorption of the Eu(3+) ion. The thermometer is based on the simple Eu(3+) energy level structure and can operate between 180 and 323 K with a relative sensitivity ranging from 0.7 to 1.7% K(-1). The thermometric parameter is defined as the ratio between the emission intensities of the (5)D0 → (7)F4 transition when the (5)D0 emitting level is excited through the (7)F2 (physiological range) or (7)F1 (down to 180 K) level. Nano and microcrystals of Y2O3:Eu(3+) were chosen as a proof of concept of the operational principles in which both excitation and detection are within the first biological transparent window. A novel and of paramount importance aspect is that the calibration factor can be calculated from the Eu(3+) emission spectrum avoiding the need for new calibration procedures whenever the thermometer operates in different media.

Lanthanide luminescence has many important applications in anion sensing, protein recognition, nanosized phosphorescent devices, optoelectronic devices, immunoassays, etc. Luminescent europium complexes, in particular, act as light conversion molecular devices by absorbing ultraviolet (UV) light and by emitting light in the red visible spectral region. The quantum yield of luminescence is defined as the ratio of the number of photons emitted over the number of UV photons absorbed. The higher the quantum yield of luminescence, the higher the sensitivity of the application. Here we advance a conjecture that allows the design of europium complexes with higher values of quantum yields by simply increasing the diversity of good ligands coordinated to the lanthanide ion. Indeed, for the studied cases, the percent boost obtained on the quantum yield proved to be strong: of up to 81%, accompanied by faster radiative rate constants, since the emission becomes less forbidden.

White-light emitting Ln-MOFs ([Ln2(Mell)(H2O)8]) were obtained via LBL epitaxial growth.