The extensive use of synthetic dyes in industrial sectors such as textile, leather, and paper manufacturing generates large volumes of colored wastewater, posing serious risks to human health and the environment. Semiconductor photocatalysis has emerged as an efficient and environmentally friendly strategy for the degradation of organic pollutants in water. Among semiconductor materials, TiO₂ nanoparticles have attracted considerable attention due to their chemical stability, low cost, and non-toxicity; however, their photocatalytic efficiency is often limited by rapid electron–hole recombination and limited light absorption. Rare-earth ion doping has been proposed to overcome these limitations.

In this study, pure TiO₂ and Sm³⁺-doped TiO₂ nanoparticles were successfully synthesized via a sol–gel method. The structural, morphological, textural, optical, and photoluminescent properties of the nanoparticles were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, UV–Vis absorption spectroscopy, and photoluminescence (PL) spectroscopy. Photocatalytic activity was evaluated by the degradation of methylene blue (MB) in aqueous solution under UV irradiation. Experiments were conducted using 50 mL of MB solution with an initial concentration of 20 mg·L⁻¹, while photolysis tests confirmed that no degradation occurred in the absence of a photocatalyst.

The results indicate that Sm³⁺ doping significantly enhances the photocatalytic activity of TiO₂ nanoparticles. After 90 min of irradiation, pure TiO₂ achieved a degradation efficiency of approximately 20%, corresponding to an apparent quantum yield (AQY) of 0.7%, whereas Sm³⁺-doped TiO₂ nanoparticles reached about 80% degradation, with an AQY of 2.8% under identical conditions. The enhanced photocatalytic performance is attributed to improved light absorption and reduced electron–hole recombination induced by Sm³⁺ incorporation. These findings demonstrate that Sm³⁺-doped TiO₂ nanoparticles are promising photocatalysts for efficient wastewater treatment applications.

Over the years, global consumption of antibiotics has increased, as has their presence in the environment, mainly due to the discharge of ineffectively treated wastewater. Until 2045, Urban Wastewater Treatment Plants (UWWTP) with a population equivalent load of 150,000 or more must implement quaternary treatments to promote the removal of micropollutants, such as antibiotics. For such a purpose, solar-driven photocatalysis is considered promising. In this study, a novel photocatalyst composed of TiO₂, Carbon Quantum Dots (CQD), and magnetic nanoparticles was produced using co-precipitation. The produced magnetic TiO₂/CQD composite was tested for the removal of 3 antibiotics (amoxicillin (AMX), sulfamethoxazole (SMX) and trimethoprim (TMP)) under simulated solar irradiation and different operation conditions: pH (6, 7, 8 and 9), dissolved organic matter (10, 20 and 40 mg/L), and water matrices with distinct complexity (phosphate-buffered ultrapure water at pH 8 and secondary UWWTP effluent (sUWWTPe)). Tests at different pH levels revealed no significant effect of pH for most antibiotics. Conversely, 10 mg/L of dissolved organic matter enhanced the photodegradation of the tested antibiotics, whereas higher concentrations slowed the removal of all antibiotics and decreased photocatalyst efficiency. In PBS, the magnetic TiO₂/CQD photocatalyst resulted in a 154-fold increase in the photodegradation kinetic rate compared to photolysis. Meanwhile, in sWWTPe, the photodegradation kinetic rate increased by 2 times for both TMP and SMX, whereas external factors hindered precise quantification of the kinetic rate enhancement for AMX. Furthermore, the magnetic TiO₂/CQD photocatalyst improved antibiotics mineralisation, reaching 80% after 15 h of irradiation for AMX and TMP and 30 h for SMX, compared with only 20% without the photocatalyst. Therefore, the applied photocatalyst is a promising option for solar-driven quaternary wastewater treatments in UWWTP, enabling the sustainable removal of antibiotics.

Relatively low-cost Titanium Carbide (TiC) materials and Metal Matrix Composites (MMC) are proposed for waste-to-hydrogen conversion. Two type of steels are used as bases prepared from EN 10088 flat products, namely X2CrTi12 (1.4512, AISI 409) and X5CrNi18-10 (1.4301, AISI 304). TiC is mixed with TRIBALOY® T-800 alloy in powder form and applied via Laser Directed Energy Deposition (DED-LB) over the substrates. For the powder mixture, Fourier transform infrared spectroscopy (FT-IR) and Differential Scanning Calorimety (DSC) are performed. The raw materials are investigated for the processes that occur in them under heating. After the solidification of the molten mixture, grinding and polishing are performed to achieve a thin layer. The studies of the obtained MMC include interface zones assessment, hardness and Young's modulus distribution, microstructural analysis, and visual defect evaluation. Advanced sensors for Acoustic Emission (AE) and Electrical Contact Resistance (ECR) gave characterization together with micro-scratch testing. The use of Photoluminescence Spectroscopy is proposed for the new composite materials. The electron transfer pathway can be studied with time-resolved spectroscopy. Renewable energy production by breaking down waste into hydrogen-rich syngas can be achieved through pyrolysus, followed by steam reforming and purification. The obtained novel materials show promising application solutions with increased durability, corrosion, and wear resistance.

Nowadays, environmental pollution represents a global-scale problem. During the environmental degradation of plastic waste, micro- and nanosized plastic particles are formed, which pose potential health risks; at the same time, their detection and characterization constitute a significant analytical challenge.

Currently, the detection of microplastics is carried out primarily using microscopic techniques. The most commonly applied fluorescent dye, Nile Red [1], does not bind, or binds only under more intensive staining conditions, to several frequently occurring plastic types (such as PVC, PA, and PET), which makes the development of new, more efficient fluorescent labeling agents necessary.

In the present study, various solvatochromic dyes have been tested as tools for the quantification and visualization of microscopic plastic fragments. Since different plastic types possess distinct dielectric constants, these dyes may be suitable for the qualitative characterization of microplastics by exhibiting plastic-type-dependent changes in their fluorescence emission. The applicability of DANS (4-dimethylamino-4′-nitrostilbene) has already been demonstrated in the literature [2]; in our own research, we developed this approach further. Due to the apolar nature of many plastics, their dielectric constant values are relatively close to one another, resulting in significant overlap in the fluorescence emission spectra for certain plastic types (such as PE and PP). However, even in such cases, the fluorescence decay times may be significantly different, which can be exploited as a secondary selectivity parameter for qualitative discrimination. The measurement method was also extended to additional solvatochromic fluorescent probes.

[1] Shim, W. J.; Song, Y. K.; Hong, S. H.; Jang, M. Identification and Quantification of Microplastics Using Nile Red Staining. Marine Pollution Bulletin 2016, 113 (1), 469–476. https://doi.org/10.1016/j.marpolbul.2016.10.049.

[2] Sancataldo, G.; Ferrara, V.; Bonomo, F. P.; Chillura Martino, D. F.; Licciardi, M.; Pignataro, B. G.; Vetri, V. Identification of Microplastics Using 4-Dimethylamino-4′-Nitrostilbene Solvatochromic Fluorescence. Microscopy Research and Technique 2021, 84 (12), 2820–2831. https://doi.org/10.1002/jemt.23841.

The presence of antibiotics in aquatic environments has become a growing concern due to their incomplete removal in conventional wastewater treatment plants, leading to the dissemination of antimicrobial resistance. Solar-driven advanced oxidation processes have emerged as sustainable strategies for degrading persistent pharmaceuticals. In this context, immobilizing photocatalysts onto polymeric supports may facilitate their recovery and reuse, thereby enhancing the practicality of water treatment applications. Carbon Quantum Dots (CQDs) were synthesized hydrothermally and incorporated onto commercial TiO₂ (P25) to form TiO₂/CQDs nanocomposites. These photocatalysts were embedded into electrospun polycaprolactone (PCL) nanofibers at a 1:2 photocatalyst-to-polymer ratio, and the resulting fibers were characterized by scanning electron microscopy. Photolysis and photocatalysis experiments were carried out under simulated solar irradiation using amoxicillin (AMX, 10 mg L^-1) in phosphate buffer (0.001 mol L^-1, pH 8), with a photocatalyst concentration of 1.5 g L^-1. AMX degradation was monitored by HPLC-UV. The kinetic parameters were determined by assuming pseudo-first-order behavior. AMX removal under irradiation was significantly enhanced in the presence of the photocatalyst, resulting in an approximately 18-fold increase in degradation efficiency compared with photolysis. The pseudo-first-order rate constant increased from 0.0112 h^-1 to 0.201 h^-1 with TiO₂/CQDs@PLC, reducing the AMX half-life from 62 to 3.45 h. These results highlight the potential of this sustainable method for treating water contaminated with antibiotics.

Light-assisted electrochemical conversion of carbon dioxide is widely investigated as a potential pathway toward sustainable energy and carbon utilization technologies. Cu₂O-based materials remain central to these studies due to their ability to facilitate complex CO₂ reduction processes. In this contribution, we focus on the relationship between electrodeposition conditions and the photoelectrocatalytic performance of copper-based composite layers during light-assisted CO₂ conversion. The composite layers were prepared by electrodeposition from alkaline electrolytes based on copper(II) lactate complexes, containing dispersed reduced graphene oxide (rGO). The layers were electrodeposited at different potentials in order to optimize their selectivity and efficiency toward ethylene formation. The electrodeposited layers were examined under dark and under illumination in CO₂-saturated aqueous electrolytes to assess the influence of synthesis parameters on their photoelectrochemical performance in the conversion of CO₂ to hydrocarbons. The analysis highlights qualitative trends linking electrodeposition conditions with changes in the photoelectrochemical performance of the obtained layers. Differences observed between materials obtained at varied deposition potentials point to the role of material composition in the modification of charge-transfer processes during light-assisted CO₂ reduction. The presence of rGO further contributes to modulation of the photoelectrochemical response, indicating its influence on interfacial charge transport under illuminated conditions. The results emphasize electrodeposition as a versatile method of synthesis of composite layers for PEC CO₂ conversion. Obtained results provide insight into how controlled adjustment of electrodeposition parameters can guide the design of materials for light-assisted electrochemical CO₂ conversion.

Organoboronate esters have attracted significant attention due to their broad utility in organic synthesis as versatile intermediates, as well as their relevance in medicinal chemistry and materials science. These environmentally benign building blocks can be readily transformed into a wide range of functional groups, enabling their application in the synthesis of advanced materials. In particular, heteroaryl boronates such as thiophene-derived esters are of special interest owing to their diverse applications, ranging from conjugated materials for organic electronics and LED devices to antimicrobial agents in medicinal chemistry.^[1]
Accordingly, the development of innovative and efficient synthetic strategies for their preparation remains highly desirable. Over the past decade, numerous methodologies based on transition-metal catalysis or metal-free approaches have been reported for the synthesis of organoboron derivatives and their subsequent functionalization.^[2] Among the available precursors, aryl halides stand out as ideal starting materials due to their low cost and widespread commercial availability. In this context, visible-light photoredox catalysis has emerged as a powerful strategy for the activation of aryl halides, enabling the generation of radical intermediates that can be efficiently trapped by boron-based nucleophiles to afford aryl boronate esters.^[3]
Herein, we report our latest results on the borylation of (hetero)aryl halides under anaerobic and aerobic mild conditions using an easy-to-handle gel nanoreactor. This photocatalyst-free protocol proceeds under visible-light irradiation at room temperature and in the presence of air, highlighting its operational simplicity and sustainability. Notably, the gel network provides a stabilizing microenvironment that enables a broad substrate scope.
References
[1] Neeve, E. C.; Geier, S. J.; Mkhalid, I. A. I.; Westcott, S. A.; Marder, T. B. Chem. Rev. 2016, 116, 9091.
[2] Hemming, D.; Fritzemeier, R.; Westcott, S. A.; Santos, W. L.; Steel, P. G. Chem. Soc. Rev. 2018, 47, 7477.
[3] Twilton, J.; Le, C.; Zhang, P.; Shaw, M. H.; Evans, R. W.; MacMillan, D. W. C. Nat. Rev. Chem. 2017, 1, 0052.

Solar radiation contains ultraviolet (UV) radiation (100–400 nm) and is classified into UVC, UVB, and UVA regions. While UVC radiation is blocked by the ozone layer, UVA and UVB reach the Earth’s surface. Although this radiation is essential for life, it is also responsible for acute and chronic skin damage, including erythema, permanent pigmentation, and skin cancer. Skin cancer is currently one of the most prevalent cancers worldwide, with its incidence steadily increasing over recent decades as a consequence of excessive and prolonged exposure to solar radiation. According to the American Cancer Society, more than three million new cases are diagnosed each year.

Sunscreens remain the most effective strategy to mitigate the risks associated with solar exposure; however, many commercially available UV filters have not evolved sufficiently to meet current safety, efficacy, and environmental standards. Moreover, several widely used UV filters raise concerns regarding photostability, photoreactivity, potential toxicity, and environmental persistence. To address these limitations, there is an urgent need for the development of next-generation UV filters that combine strong UV absorption with robust photoprotection mechanisms and improved safety profiles. Ideal UV filters should exhibit high chemical and thermal stability, efficient and non-reactive energy dissipation pathways, low phototoxicity, and biodegradability.

Inspired by naturally occurring molecules, our research group has rationally designed a new family of photoprotective compounds featuring enhanced photoprotective performance. Their efficacy has been evaluated through detailed studies of UV absorption, photostability, antioxidant capacity, and toxicity. The results demonstrate improved stability, enhanced photoprotection, and increased safety, highlighting the potential of these compounds as a new generation of UV filters.

The sustainable photocatalytic upcycling of plastic waste under mild conditions represents an emerging pathway toward a circular materials economy. In this study, we present the development of innovative nanostructured titania-based photocatalysts, designed to efficiently drive polymer conversion under low-intensity UVA or visible light. The catalysts consist of mixed titanium hydroxide/titanium dioxide phases, synthesized by energy-efficient sono-chemical methods. These routes yield zero- and one-dimensional nanostructure, such as doped anatase core, shell systems embedded in amorphous carbon-rich matrices or titanate nanotubes, featuring superior light-harvesting capacity, improved charge carrier separation, and enhanced surface reactivity.

The catalytic performance of these tailored materials is demonstrated in the selective photo-depolymerization of bio-based polymers, including polylactic acid (PLA), polyethylene furanoate (PEF), and polybutylene succinate (PBS), under ambient conditions. Remarkably, the process proceeds in the absence of organic solvents, additives, or sacrificial agents, affording value-added monomers and lactic acid-derived products through a fully green transformation route. Systematic optimization of process parameters ensures both activity and selectivity, emphasizing scalability and environmental compatibility.

This work establishes heterogeneous photocatalysis as a viable and sustainable strategy for ambient-condition plastic upcycling. Using PLA as a model substrate, it provides a foundation for implementing low-energy photocatalytic technologies in real-world waste valorization applications, bridging materials design with circular economy principles.

Acknowledgements

This project is carried out within the framework of the National Recovery and Resilience Plan Greece 2.0, funded by the European Union – NextGenerationEU (Implementation body: HFRI, Project “Green and Sustainable Photochemical Upcycling of Plastic Waste and Biobased Polymers to High-Added Value Chemicals" No.: 015949).

Rising global demand for chemicals, materials, fuels, and energy demands the adoption of innovative and sustainable technologies. To this end, significant research efforts are focused on the production of value-added chemicals through the catalytic valorization of renewable feedstocks, particularly biomass waste. Moreover, harnessing solar energy to drive selective chemical conversions is regarded as a promising green technology. In this context, the development of novel nanomaterials with improved photocatalytic performance is crucial for efficient biomass valorization. Titanium oxide-based materials have been extensively reported as effective photocatalysts, although they are primarily associated with the non-selective mineralization of organic pollutants. Therefore, novel nanocatalysts are essential to achieve selective photocatalytic activity.

In this study, novel one-dimensional titanium oxides were synthesized from commercially available TiO₂ anatase particles and studied for the selective oxidative cleavage of lignin-inspired β-Ο-4 linkages towards value-added aromatics. The resulting material was composed of nanotubes with external diameters 6-10 nm, inner channels between 3-7 nm, and length ranging from 90-200 nm. Furthermore, nanotubes possess a large specific surface area (S_BET = 154 m²/g) and pore volume (V_total = 0.80 cm³/g), significantly higher compared to the commercial precursor TiO₂ Anatase nanoparticles (S_BET = 10 m²/g, V_total = 0.03 cm³/g). The band gap was estimated at 3.12 eV, comparable to that of anatase (3.2 eV).

The photocatalytic performance of both materials was evaluated either under low-intensity UV-A irradiation (370 nm), or monochromatic wavelengths within the range of visible light (427, 440, 525 nm), and combinations thereof. The novel nanomaterial showed the greatest aromatic yield of benzaldehyde (Ph-CHO), enhanced by 2.4 times compared to commercial TiO₂ anatase nanoparticles under combined irradiation of the three monochromatic wavelengths. Mechanistic studies indicated the involvement of multiple reactive species in the photoreaction, with dissolved O₂ playing a pivotal role.