Analytical method for the determination of the absorption coefficient of DNA-stabilized silver nanoclusters.

DNA-stabilized silver nanoclusters (DNA-AgNCs) are biocompatible emitters formed by silver atoms and cations encapsulated in DNA oligomers. Here, we present an analytical approach to calculate the molar absorption coefficient (ε) of these systems, which consists of combining UV-Vis spectroscopy, electrospray ionization-mass spectrometry (ESI-MS), and inductively coupled plasma-optical emission spectrometry (ICP-OES). ESI-MS enables the determination of the number of silvers bound to the DNA strands, whereas ICP-OES allows measurement of the total amount of silver in solution. The data is used to calculate the concentration of DNA-AgNCs and together with UV-Vis absorbance, allows for the calculation of ε. We compare the obtained ε with the experimental values previously determined through fluorescence correlation spectroscopy (FCS) and theoretical estimates based on the ε of the DNA itself. Finally, the experimental radiative decay rates (kf) and ε values are evaluated and compared to those typically found for organic fluorophores, highlighting the molecular-like nature of the DNA-AgNC emission.

Phase-engineering compact and flexible CsPbBr3 microcrystal films for robust X-ray detection.

All-inorganic CsPbBr3 perovskites have gained significant attention due to their potential in direct X-ray detection. The fabrication of stable, pinhole-free thick films remains challenging, hindering their integration in durable, large-area high-resolution devices. In this study, we propose a facile strategy using a non-conductive polymer to create a flexible, compact thick film under ambient conditions. Furthermore, we investigate the effect of introducing the 2D CsPb2Br5 phase into CsPbBr3 perovskite crystals on their photophysical properties and charge transport. Upon X-ray exposure, the devices consisting of the dual phase exhibit improved stability and more effective operation at higher voltages. Rietveld refinement shows that, due to the presence of the second phase, local distortions and Pb-vacancies are introduced within the CsPbBr3 lattice. This in turn presumably increases the ion migration energy barrier, resulting in a very low dark current and hence, enhanced stability. This feature might benefit local charge extraction and, ultimately, the X-ray image resolution. These findings also suggest that introducing a second phase in the perovskite structure can be advantageous for efficient photon-to-charge carrier conversion, as applied in medical imaging.