In order to obtain Gd_2.97Pr_0.03Ga₃Al₂O₁₂ powders with different crystallite sizes, a modified Pechini (sol–gel) method was used. Powders were then used for the preparation of ceramics by a high-pressure low-temperature sintering method. The impact of crystallite size and pressure applied during the sintering procedure on conventional and persistent luminescence was investigated and analyzed. It was found that the emission color is strictly dependent on the crystallite size, as such phenomenon may be used in the field of advanced anti-counterfeiting. The spectroscopic properties of Gd_2.97Pr_0.03Ga₃Al₂O₁₂ were characterized by means of photoluminescence measurements. The kinetics of luminescence were measured in order to analyze the energy transfer between ³P₀ and ¹D₂ excited states that also take an active role in the persistent luminescence process. It was found that an increase in the crystallite size led to a higher energy transfer from the ³P₀ to ¹D₂ level and a change in the emission color. As such, it was studied for potential application in ratiometric optical thermometry. The effect was also investigated in terms of persistent luminescence. It was also found that the sintering pressure causes changes in the crystallographic parameters of the powders and, in consequence, has a great impact on the optical properties of ceramics. The conducted research gives insights into the mechanism of persistent luminescence and expands the application field of optical storage materials.

We present an optical spectroscopy analysis of the molecular beam epitaxy-grown InAs/GaSb quantum systems to study the higher-order optical transitions in InAs/GaSb superlattices (SLs). We have investigated two type-II SL structures with different layer widths: $\mathrm{In}{\mathrm{As}}_{8\mathrm{ML}}/\mathrm{Ga}{\mathrm{Sb}}_{8\mathrm{ML}}$ and $\mathrm{In}{\mathrm{As}}_{10\mathrm{ML}}/\mathrm{Ga}{\mathrm{Sb}}_{10\mathrm{ML}}$. To experimentally determine the spectral distribution of the higher-order transitions, the Fourier-transformed photoluminescence and Fourier-transformed photomodulated reflectance measurements were used. These measurements were undertaken vs temperature and incident polarization of the probing beam. Complementary theoretical calculations based on the eight $\mathbf{k}·\mathbf{p}$ formalism were also performed to identify the electron and heavy and light hole energy band ladder. Polarization-dependent measurements indicated the interchanging nature of the light and heavy hole states for the second and third valence band vs the SL wave vector $\left(k_z\right)$ along the growth direction. The results were compared with other calculations based on different models and existing experimental results, then summarized and reviewed for possible numerical parameters application ranges in the interface modeling.

This study focuses on harnessing the synergistic effects between titanium oxide (TiO₂) and carbon dots (CDs) to enhance the photocatalytic performance of TiO₂. The work describes the synthesis of carbon dots exhibiting fluorescence (CDs) or phosphorescence (PhCDs), as well as the preparation of the TiO₂ hybrid. Structural and textural measurements (X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ sorption isotherms) were conducted to elucidate the compositional and morphological changes induced by the incorporation of CDs into a matrix. Spectroscopic analyses revealed a shift of the absorption edge and range into the visible region of the CDs@TiO₂ hybrid compared with pure TiO₂. Infrared (IR) and Raman spectroscopy revealed the presence of diverse bonds associated with functional groups on the surface of the dots, enabling control over the spectroscopic properties of the resulting hybrids. Photocatalytic assessments demonstrated an enhancement in the PhCDs@TiO₂ hybrid activity compared with pure TiO₂. The proposed mechanism for the increase in photocatalytic activity in PhCDs@TiO₂ is based on the slowdown of carrier recombination, which is linked to the confinement of electrons within traps located below the conduction band. The demonstrated enhancement in photocatalytic activity holds promise for the more effective decomposition of organic compounds in water, while the utilization of carbon dots unveils new avenues for modifying existing photocatalysts.

A rapid, green, and cost-effective method for synthesizing carbon dots (CDs) was developed using non-toxic, low-cost precursors via a simple combustion process.

The gadolinium, gallium, aluminum garnet doped with cerium and co-doped with dysprosium ions were prepared using sol gel method. The SEM images show that after synthesis, the grains are below 100 nm. The powders were ultrasonically mixed with graphene nanoflakes and ceramics were prepared using the high pressure low temperature sintering technique. A series of the ceramics was prepared using different graphene content. The structure of the samples was examined using X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman techniques. The spectroscopic properties were checked using conventional and persistent luminescence spectra measurements. The thermoluminescence glow curves and fading time of persistent luminescence measurements were performed to check how the graphene presence affects the electron traps number and depth. It was found that the addition of graphene improved the thermal conductivity of co-doped samples. This resulted in faster release of deeper traps and an increase in fading of persistent luminescence. The possibility of releasing energy from deep traps without additional stimulation may allow the use in different applications, the matrices and luminescent ions, which so far did not show persistent luminescence at room temperature.