Joana Rodrigues

Zn₂GeO₄ (ZGeO) phosphor exhibits a wide bandgap energy, making it highly suitable for luminescence-based applications spanning the entire electromagnetic spectrum, from ultraviolet (UV) to near-infrared (NIR) wavelengths.

A defect engineering strategy is employed to produce defective calcium‐doped TiO ₂ nanomaterials (Ca:TiO ₂ ), which are subsequently incorporated into cellulose‐based membranes. Structural defects, including vacancies, stacking faults, grain boundaries and voids emerged from the interplay between calcium doping and microwave irradiation. The 10 mol.% Ca:TiO ₂ membrane achieves an 81% degradation rate and an adsorption capacity of ≈25.8 mg g ⁻¹ , showcasing excellent photocatalytic and adsorption performance. The enhanced performance is attributed to the high surface area of Ca:TiO ₂ agglomerates, the presence of oxygen vacancies, structural defects and the abundance of surface hydroxyl groups. X‐ray Photoelectron Spectroscopy (XPS) revealed that the Fermi level of the 10 mol.% Ca:TiO ₂ nanomaterial is positioned near the conduction band edge, indicating a significant modification of its electronic properties, with high electrical conductivity at room temperature (RT). Density Functional Theory (DFT) calculations provided a deeper insight into the impact of calcium doping, revealing that calcium (Ca) incorporation promotes the formation of oxygen vacancies, introducing additional electronic states near the bottom of the conduction band, thereby enhancing the material's electrical conductivity. By integrating eco‐friendly materials and defect‐engineered nanomaterials doped with earth‐abundant elements, this work aligns with sustainability principles, fostering the development of next‐generation adsorptive and photocatalytic membranes.

The study on Bi-doped LiYGeO ₄ PersL reveals a ∼6.05 eV direct bandgap, supported by hybrid DFT calculations. Li loss during synthesis was confirmed by elemental analysis. Excitation to the MMCT enables UV PersL (peaked @ 358 nm) for up to 7 hours.

Counterfeiting is a global issue with severe economic, security, and health impacts, requiring advanced anti‐counterfeiting solutions. Luminescent materials offer unique, hard‐to‐replicate identification features. To this purpose, Y ₂ GeO ₅ and LiYGeO ₄ samples doped with 0.5 mol% of bismuth (Bi) are synthesized by a solid‐state reaction. X‐ray diffraction and Raman spectroscopy revealed their polyphasic nature, with the samples mainly consisting of the desired crystalline phases. Photoluminescence measurements indicated that all samples exhibit a strong emission band in the ultraviolet A spectral region (355–365 nm), attributed to Bi ³⁺ intraionic transitions. Despite their similarities, lifetime measurements under 300 nm excitation revealed that the LiYGeO ₄ sample had a lifetime nearly 100 times longer than the Y ₂ GeO ₅ sample. Furthermore, afterglow decay profiles demonstrated that persistent luminescence (PersL) is only observed in the LiYGeO ₄ sample, detectable for over 7 h after 10 min of stimulation with 250 nm light. Longer wavelengths failed to induce PersL. This finding highlights the importance of the host material and its associated defects as trap centres that contribute to PersL. By combining these materials, multi‐level anti‐counterfeiting codes can be designed based on the differences in lifetime, PersL, and excitation energy, making them extremely difficult to replicate without specific knowledge of the materials involved.

Defective TiO₂ nanostructures on 3D polyurethane foams for the adsorption and degradation of tetracycline under sunlight irradiation.

This paper reports a comprehensive study of single-phase polycrystalline chromium-doped zinc gallogermanate (ZGGO:Cr) synthesised by a high-temperature solid-state reaction, employing photoluminescence (PL), persistent luminescence (PersL) and thermoluminescence (TL) measurements. A bandgap energy of ∼4.77 eV (260 nm) was estimated by optical reflectance. The ZGGO:Cr luminescence was dominated by a red/near-infrared emission due to Cr³⁺ optical centres, which displayed well-resolved R1, R2, N1 and N2 lines, and a broad vibronic progression. PL excitation (PLE) data revealed that those centres were preferentially populated via intraionic absorption, being also excited via band-to-band absorption and by a defect excitation band at ∼0.9 eV below the conduction band, whose origin remains unknown. PersL of more than 10 h was identified and attributed to the N2 Cr³⁺-related defect. The TL results suggest a continuous distribution of electronic states with activation energies ranging from about 0.7 eV to 1.2 eV. An effective density of states was obtained for different delay times between irradiation and heating, revealing a rapid depopulation for activation energies below ∼1 eV. In short, this research contributes to a better understanding of traps in ZGGO:Cr and highlights the potential of the Cr³⁺-related emission in this material for dosimetric purposes, paving the way for developing novel ZGGO:Cr-based devices.

Cr-doped Al₂O₃ spheres with strong red emission were produced using a simple laser processing approach with a 50 W continuous CO₂ laser. Structural characterization revealed that the produced spheres were monophasic, comprising the α-Al₂O₃ phase. Photoluminescence (PL) studies indicated that the observed red emission originates from multiple Cr³⁺ optical centers being dominated by the ²E → ⁴A₂ transition (R-lines), with a further contribution from the parity and spin forbidden ²T₁ → ⁴A₂ transition (R′-lines). The identification of additional radiative recombination from chromium ion pairs (N-lines) evidences that the produced samples are heavily doped. As such, energy transfer processes between the different chromium optical centers are seen to take place, as suggested by the lifetime decay analysis. PL excitation revealed that the room temperature luminescence is preferentially populated via the spin-allowed ⁴A₂ → ⁴T₂,⁴T₁ transitions and by the parity and spin-forbidden ⁴A₂ → ²T₂ (B-lines), ²T₁ (R′-lines)_, ²E (R-lines). Such results demonstrate that the present synthesis method is able to deliver high-optical-quality Al₂O₃:Cr crystals in a fast and simple way, with potential interest for optical, sensing, or lasing applications.

Luminescent materials are capable of transforming certain types of energy into electromagnetic radiation, which means that in response to a specific stimulus, these materials emit light typically within the ultraviolet (UV) to the infrared (IR) spectral region

A novel series of Zn(ii) and Cu(ii)-based porphyrin complexes doubly functionalised with carbazole units pave the way for efficient hole-transporting materials for perovskite solar cells.