Colloidal quasi-two-dimensional cadmium chalcogenide nanoplatelets have attracted considerable interest due to their narrow excitonic emission and absorption bands, making them promising candidates for advanced optical applications. In this study, the synthesis of quasi-two-dimensional CdSe NPLs with a thickness of 3.5 monolayers was investigated to understand the effects of synthesis temperature on their stoichiometry, morphology, and optical properties. The NPLs were synthesized using a colloidal method with temperatures ranging from 170 °C to 210 °C and optimized precursor ratios. Total reflection X-ray fluorescence (TXRF) analysis was employed to determine stoichiometry, while high-resolution transmission electron microscopy (HRTEM) and UV-Vis spectroscopy and photoluminescence spectroscopy were used to analyze the structural and optical characteristics. The results showed a strong correlation between increasing synthesis temperature and the enlargement of nanoscroll diameters, indicating dynamic growth. The best results in terms of uniformity, stoichiometry, and optical properties were achieved at a growth temperature of 200 °C. At this temperature, no additional optical bands associated with secondary populations or hetero-confinement were observed, indicating the high purity of the sample. Samples synthesized at lower temperatures exhibited deviations in stoichiometry and optical performance, suggesting the presence of residual organic compounds.

Radiation transfer in layers of densely packed aggregates of hydroxyapatite nanoparticles was studied for a spectral range from 300 to 1100 nm using diffuse reflectance measurements and the modeling of the light transfer properties of the layers. The studied samples of dispersed biogenic hydroxyapatite were obtained from animal bone material (bovine bones) using fast pyrolysis followed by grinding and pressing into tablets. A distinctive feature is the high reflectivity (high albedo) of the obtained samples, which is practically independent of the wavelength in the studied spectral range and comparable to the reflectivity of the diffuse reflectance standard based on Spectralon. The modeling of the light transfer properties of the studied samples within the framework of the effective medium theory (using coherent potential approximation) made it possible to establish the weak dependence of the mean scattering-free path and the mean transport-free path of light propagation in the medium on the wavelength, which is consistent with the features observed in the experiment. Possible prospects for the use of nanostructured hydroxyapatite as photonic material are discussed.

CdTe colloidal nanoplatelets (NPLs) are promising two-dimensional quantum emitters, but their surface chemistry has been less studied compared to CdSe NPLs. Understanding and controlling surface properties are critical for their application. In this work, we investigate the conditions under which CdTe NPLs remain stable during post-synthetic ligand exchange in mild organic environments, which is a key step for their further use. During the initial stage of the work, the effect of the stoichiometric ratio of precursors on the optical characteristics and chemical composition of CdTe NPLs obtained at a temperature of 170 °C was analysed. The concentrations of Cd and Te varied within ±50% with respect to our standard version. The results obtained by TXRF demonstrated the formation of compositions with a moderate excess of cadmium (the Cd/Te ratio varied from 1.03 to 1.19). These conclusions are consistent with the concept of Cd-terminated surfaces stabilized by carboxylate ligands. Three standard ligand exchange strategies successfully applied to CdSe nanocrystals (carboxylate → CdCl₂, → Zn(DDTC)₂ and → hexadecanethiol) were tested on CdTe nanocrystals. Contrary to expectations, treatment of CdTe with CdCl₂ or Zn(DDTC)₂ solutions did not result in a measurable shift in exciton transitions and, moreover, caused degradation of the colloidal dispersion. Our studies have identified a range of conditions under which CdTe NPLs retain their integrity during ligand exchange. While some elements of the CdSe-developed protocols can be transferred to CdTe, their applicability is limited by a narrow processing window: beyond a certain treatment time, CdTe nanoplatelets progressively lose optical stability

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.

Разработка подходов к управлению толщиной, структурной однородностью и химическим состоянием поверхности CdSe-нанопластин актуальна для получения материалов с заданными и воспроизводимыми спектроскопическими характеристиками. В работе проведено сравнительное исследование CdSe НПЛ, полученных методом постепенного нагревания с использованием предварительно синтезированного миристата кадмия и методом горячей инжекции селеноорганического прекурсора в реакционную среду, содержащую ацетат кадмия и олеиновую кислоту. Показано, что выбранный синтетический маршрут существенно влияет на процесс формирования, толщину и однородность нанопластин. При постепенном нагревании образованию НПЛ предшествует появление промежуточных CdSe-содержащих наночастиц, а конечный продукт представлен преимущественно НПЛ толщиной 4 ML с небольшой долей 3 ML. Метод горячей инжекции приводит к формированию более однородной популяции НПЛ толщиной 3 ML. Для обоих образцов подтверждено образование структуры, производной от кубической фазы CdSe типа цинковой обманки, при этом образец, полученный методом постепенного нагревания, характеризуется более выраженной структурной неоднородностью. Различия в толщине и однородности НПЛ проявляются в их оптических свойствах и состоянии поверхности. Анализ карбоксилатных групп и элементного состава указывает на различное локальное окружение поверхностных лигандов и вероятное присутствие остаточного кадмий-миристатного компонента в образце, синтезированном с использованием миристата кадмия. Полученные результаты показывают, что природа кадмиевого прекурсора, способ образования его карбоксилатной формы и условия введения селена совместно определяют структурные, поверхностные и спектроскопические характеристики CdSe НПЛ.