Random patterns of lanthanide(III) ion–doped zeolites were used to create a tamper-proof optical authentication system.

In this paper we present a new near-IR emitting silver nanocluster (NIR-DNA-AgNC) with an unusually large Stokes shift between absorption and emission maximum (211 nm or 5600 cm). We studied the effect of viscosity and temperature on the steady state and time-resolved emission. The time-resolved results on NIR-DNA-AgNC show that the relaxation dynamics slow down significantly with increasing viscosity of the solvent. In high viscosity solution, the spectral relaxation stretches well into the nanosecond scale. As a result of this slow spectral relaxation in high viscosity solutions, a multi-exponential fluorescence decay time behavior is observed, in contrast to the more mono-exponential decay in low viscosity solution.

The nanosecond excited state temporal and spectral relaxation of a purified, red-emitting DNA-templated silver nanocluster (DNA-AgNC) was characterized as a function of temperature. The findings are explained by introducing a phenomenological electronic structure diagram. The reproducibility and cyclability of the average decay time opens up the possibility of using DNA-AgNCs for decay time-based nanothermometry.

DNA-templated silver nanoclusters of a few tens of atoms or less have come into prominence over the last several years due to very strong absorption and efficient emission. Applications in microscopy and sensing have already been realized, however little is known about the excited-state structure and dynamics in these clusters. Here we report on a multidimensional spectroscopy investigation of the energy-level structure and the early-time relaxation cascade, which eventually results in the population of an emitting state. We find that the ultrafast intramolecular relaxation is strongly coupled to a specific vibrational mode, resulting in the concerted transfer of population and coherence between excited states on a sub-100 fs timescale.

Measurements on biological samples are often hampered by auto-fluorescence from inherent compounds in tissue or cells, limiting the achievable contrast. Both the signal of interest and the auto-fluorescence are usually detected on the Stokes side of the excitation laser. In this communication, we present two new microscopy modalities, based on the emission of a red-emitting DNA-stabilized silver nanocluster (DNA-AgNC). Its bright fluorescence can be generated on the anti-Stokes side of the readout laser, allowing easy spectral separation of the signal of interest from the Stokes side auto-fluorescence.