Defect-related self-activated luminescence of unintentionally undoped biogenic carbonate-containing hydroxyapatite (HAp) was studied at 12 K under tunable vacuum-ultraviolet excitation at the P66 beamline of PETRA III. X-ray diffraction confirmed the hexagonal P6₃/m apatite framework and an apparent coherent-domain size of approximately 57.7 nm. Raman spectroscopy verified the phosphate framework, B-type carbonate near 1072 cm⁻¹, and a perturbed structural-OH environment, while not identifying defect charge states. Four empirical emission families were resolved at 2.530, 2.995, 3.305, and 3.630 eV. PLE monitored at 504, 426, 375, and 346 nm covers D1–D4 and reveals common excitation regions near 5.3–5.5, 6.1, and 7.06–7.10 eV, together with D2-selective and D4-selective features near 6.50 and 9.83 eV. The D3-centred 375 nm profile is dominated by the 7.10 eV component. Hybrid-functional and G₀W₀ calculations place the ideal-HAp edge near 7.1–7.5 eV; therefore, the common near-7.1 eV PLE feature is treated as the best-supported host-related near-edge/excitonic marker, whereas lower-energy features are assigned cautiously to localized sub-gap absorption. Because PLE is not a direct absorption measurement, the pathway scheme is presented as a conceptual hypothesis rather than a uniquely resolved kinetic model.

Post-synthetic doping provides a route to modify the excited-state dynamics of semiconductor nanoplatelets without coupling dopant incorporation to their initial nucleation and growth. Here, we investigate post-synthetic Mn incorporation into preformed CdSe nanoplatelets using manganese (II) diethyldithiocarbamate followed by thermal treatment under inert conditions. Structural and compositional analyses confirm the association of Mn with the nanoplatelets while preserving their platelet-like morphology and zinc-blende CdSe structure. Under the present reaction conditions, DPE-based treatments yield substantially higher Mn incorporation than HB-based treatments, demonstrating the strong sensitivity of the incorporation process to the reaction environment. Importantly, undoped control experiments show that broad visible-to-NIR emission can also arise from pristine CdSe nanoplatelets and can be strongly enhanced by thermal treatment, demonstrating that the spectral appearance of the broad band alone is not a unique signature of Mn-related states. The decisive difference is instead found in the emission dynamics: pristine and thermally treated undoped nanoplatelets, as well as low-Mn HB samples, exhibit broad-band decay on the few-microsecond timescale, whereas the main Mn-rich DPE samples display exceptionally long-lived broadband emission extending into the hundred-microsecond regime. PLE measurements further show that the low-energy emission is populated following excitation of the CdSe host. These results identify the emission kinetics, rather than the presence of broadband photoluminescence itself, as the clearest signature of additional Mn-associated relaxation pathways and demonstrate that post-synthetic reaction conditions provide a means of accessing long-lived excited-state dynamics in CdSe nanoplatelets. A representative sample also retained a comparable PLQY after more than two years of ambient storage, supporting the long-term stability of the optical response.