NIR induced modulation of the red emission from erbium ions for selective lanthanide imaging

Upon direct excitation with green light (522 nm), Er3+ ion doped nanoparticles feature a number of radiative and non-radiative decay pathways, leading to distinct and sharp emission lines in the visible and near-infrared (NIR) range. Here we apply, in addition to continuous 522 nm irradiation, a modulated NIR irradiation (1143 nm) to actively control and modulate the red emission intensity (around 650 nm). The modulation of red Er3+ ion emission at a chosen frequency allows us to reconstruct fluorescence images from the Fourier transform amplitude at this particular frequency. Since only the emission from the Er3+ ion is modulated, it allows to selectively recover the lanthanide specific signal, removing any non-modulated auto-fluorescence or background emission resulting from the continuous 522 nm excitation. The modulated emission of specific lanthanides can open up new detection opportunities for selective signal recovery

Versatile and Validated Optical Authentication System Based on Physical Unclonable Functions

Counterfeit consumer products, electronic components, and medicines generate heavy economic losses, pose a massive security risk, and endanger human lives on a daily basis. Combatting counterfeits requires incorporation of uncopiable or unclonable features in each and every product. By exploiting the inherent randomness of stochastic processes, an optical authentication system based on physical unclonable functions (PUFs) was developed. The system relies on placing unique tagsPUF-tagson the individual products. The tags can be created using commercial printing and coating technologies using several combinations of carrier materials and taggant materials. The authentication system was found to be independent of how contrast was generated, and examples of PUF-tags based on scattering, absorption, and luminescence were made. A version of the authentication using the combination of scattering-based PUF-tags and a smartphone-based reader was validated on a sample size of 9720 unique codes. With zero false positives in 29 154 matches, an encoding capacity of 2.5 × 10120, and a low cost of manufacture, the scattering-based authentication system was found to have the potential to solve the problem of counterfeit products

Electronic Energy Levels of Dysprosium(III) ions in Solution. Assigning the Emitting State and the Intraconfigurational 4f-4f Transitions in the Vis-NIR Region and Photophysical Characterization of Dy(III) in Water, Methanol, and Dimethyl Sulfoxide

Dysprosium­(III) ions are the third most luminescent lanthanide­(III) ions. Dy­(III) is used as dopant in optical fibers and as shift reagent in NMR imaging and is the element at the forefront of research in single-molecule magnets. Nonetheless, the excited state manifold of the dysprosium­(III) ion is not fully mapped and the nature of the emitting state has not been unequivocally assigned. In the work reported here, the photophysical properties of dysprosium­(III) triflate dissolved in H2O, MeOH, and DMSO have been studied in great detail. The solvates are symmetric, all oxygen donor atom complexes where the coordination number is 8 or 9. By comparing protonated and deuterated solvents, performing variable temperature spectroscopy, and determining the excited state lifetimes and luminescence quantum yields, the solution structure can be inferred. For the three complexes, the observed electronic energy levels were determined using absorption and emission spectroscopy. The Dy­(III) excited state manifolds of the three solvates differ from that reported by Carnall, in particular for the low lying 6F-states. It is shown that dysprosium­(III) complexes primarily luminesce from the 4F9/2 state, although thermal population of, and subsequent luminescence from the 4I15/2 state is observed. The intrinsic luminescence quantum yield is moderate (∼10%) in DMSO-d6 and is significantly reduced in protonated solvent as both C–H and O–H oscillators act as efficient quenchers of the 4F9/2 state. We are able to conclude that the emitting state in dysprosium­(III) is 4F9/2, that the mJ levels must be considered when determining electronic energy levels of dysprosium­(III), and that scrutiny of the transition probabilities may reveal the structure of dysprosium­(III) ions in solution