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 tagsPUF-tagson 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 × 10 120 , and a low cost of manufacture, the scattering-based authentication system was found to have the potential to solve the problem of counterfeit products.
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-d
6 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 m
J
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.
Lanthanide(III) ions bind to the glycocalyx of Chinese Hamster Ovary (CHO) cells and give rise to a unique luminescent fingerprint. Following direct excitation of terbium(III) and europium(III) ions in the visible part of the spectrum, we are able to collect emission spectra pixel-by-pixel in images of CHO cells. Following data analysis that removes the background signal, the fine structure of the europium(III) luminescence indicate that the lanthanide(III) ions are bound to a single structure of the CHO cell glycocalyx. This was deduced from the fact that the structure-sensitive emission spectrum of europium is unchanged throughout the investigated samples.
Upon direct excitation with green light (522 nm), Er 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 Er 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 Er 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.
The imaging of subcellular structures is essential in all areas of life science and research progress with the development of new imaging and analysis methods. New analytic methods have fueled the rise of glycobiology, showing that sugars are as important for biological function as proteins. Lanthanide luminescence‐based contrast agents are highly relevant as they allow for extreme sensitivity in assays with background free images. We show that the unique coordination chemistry of lanthanide ions can be used to selectively label and image specific sugars. For more information, see the Communication by T. Vosch, T. J. Sørensen et al. on page 11885 ff.
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