The UV-B component of sunlight damages the DNA in skin cells, which can lead to skin cancer and premature aging. Therefore, it is necessary to use creams that also contain UV-active substances. Many sunscreens contain titanium dioxide due to its capacity to absorb UV-B wavelengths. In the present study, titan dioxide was introduced in alginate and chitosan–alginate hydrogel composites that are often involved as scaffold compositions in tissue engineering applications. Alginate and chitosan were chosen due to their important role in skin regeneration and skin protection. The composites were cross-linked with calcium ions and investigated using FT-IR, Raman, and UV–Vis spectroscopy. The stability of the obtained samples under solar irradiation for skin protection and regeneration was analyzed. Then, the hydrogel composites were assayed in vitro by immersing them in simulated body fluid and exposing them to solar simulator radiation for 10 min. The samples were found to be stable under solar light, and a thin apatite layer covered the surface of the sample with the two biopolymers and titanium dioxide. The in vitro cell viability assay suggested that the anatase phase in alginate and chitosan–alginate hydrogel composites have a positive impact.

Magnetically separable TiO₂-based composite photocatalysts have gained significant interest in the past two decades; however, the optimization of their synthesis and the stabilization of the magnetic iron oxide within the composite is still an open challenge. The present study investigates the photocatalytic behavior and recyclability of TiO₂-Fe₃O₄ composites, with emphasis on a possible correlation between pollutant degradation efficiency, recyclability, iron oxide stability, and the phase composition of the chosen TiO₂ base. Magnetite nanoparticles were synthesized under varied temperature and alkaline conditions to identify optimal parameters for achieving the desirable magnetic properties. The magnetic nanoparticles were integrated into composite systems with either commercial TiO₂ (Evonik Aeroxide P25 with anatase–rutile mixed phase) or a hydrothermally synthesized anatase TiO₂. The P25-based composite removed 99% paracetamol from aqueous solutions under UV-A irradiation and demonstrated successful recyclability, maintaining 96% paracetamol degradation efficiency after four uses. In contrast, the anatase TiO₂-based magnetic composite exhibited a lower performance (70%) and a significantly hindered recyclability (45% after four cycles). The difference in performance was attributed to variations in the phase composition of the employed TiO₂ in the composites and, consequently, in their charge separation mechanisms.

Titanium dioxide nanostructures are extensively produced and utilized in various industries. Concerns have been raised about this material’s less researched environmental impact. This study investigates the indirect toxicity of TiO₂ nanoparticles (NPs) on ant communication via the photocatalytic degradation of ant trail pheromones. Foraging experiments with Lasius niger demonstrated that TiO₂-treated pathways were avoided by ants, suggesting trail pheromone degradation. Photocatalytic tests confirmed the degradation of the pheromone component (R)-(-)-mellein under UV-A irradiation in the presence of Evonik Aeroxide P25 TiO₂. The nanosized titania was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and diffuse reflectance spectroscopy (DRS). These findings indicate that TiO₂ NPs can disrupt ant communication, potentially leading to significant ecological consequences.

Natural rutile is a widely available titanium mineral which shows great potential as a photocatalyst for environmental remediation when processed correctly. Industries invest large sums in the transformation of the rutile mineral into pure, synthetic nano titania. Still, the present study proves that bare natural rutile with trace element content can also be applied as a photocatalyst, without harsh chemical interventions, simply by processing via nano grinding. Samples with different mean primary particle size values were obtained by wet stirred media milling, their compositional and structural properties were investigated, and their photocatalytic properties were evaluated under both visible- and UV-light illumination for the degradation of phenol and ibuprofen. By changing the grain size and the particle size distribution, and due to the doping effect of impurities present in the mineral, the band gap values of the samples and their photocatalytic activities changed as well. The nano milled rutile exhibited visible light photocatalytic activity, with a 33% degradation efficiency in the case of both phenol and ibuprofen, after 22 h of irradiation. The present study not only highlights the photocatalytic degradation of a pharmaceutical by natural rutile mineral, but its findings also suggest that ground nano rutile can function as an environmentally friendly photocatalyst, as it not only avoids the use of harmful chemicals typically employed in TiO₂ synthesis but also offers a simpler, more cost-effective alternative for producing photocatalytic materials.