Search Results (137)

UV-C radiation has emerged as a germicidal agent against pathogens, particularly following the COVID-19 pandemic. While UV-C effectively reduces cross-contamination in hospitals, it induces photodegradation in polymer devices, potentially damaging and posing risks to patient safety. Therefore, it is crucial to detect the effects of UV-C photodegradation on early stages, as well as the effects of prolonged UV-C exposure. In this study, we investigated the UV-C photodegradation (254 nm, 471 kJ/mol) of isotactic polypropylene homopolymer (PP), commonly used in medication packaging. The impact of UV-C on PP was evaluated through rheology and infrared spectroscopy. Surface energy was measured by the contact angles formed by drops of water and diiodomethane. The effects of photodegradation on the polymer’s morphology were examined using scanning electron microscopy, and the melting temperature and crystallinity by differential scanning calorimetry. Lastly, the effect of UV-C on molecular mobility was studied using ¹H Time Domain Nuclear Magnetic Resonance (¹H TD-NMR). These techniques proved to be valuable tools for identifying the early stages of UV-C photodegradation, and ¹H TD-NMR was a sensitive method to identify the chain branching as a photodegradation product. This study highlights the impact of UV-C on PP photodegradation and hence the importance of understanding UV-C-induced degradation. Full article

This work aims to apply polymeric PBAT/PLA fibers electrospun with TiO₂ in the photodegradation of the dye Red BF-4B in an aqueous solution and the dye’s subsequent reuse. Initially, the influence of the solution pH was evaluated, and the results showed more significant dye degradation at pH values below the pHpcz (7.42). Kinetic studies show that at 15 mg·L⁻¹, the highest percentage of degradation occurs at 600 min of reaction time; however, degradation equal to (or greater than) 65% was observed at all evaluated concentrations, with the kinetic data being well fitted by the pseudo-first-order model. Additional studies demonstrated the reuse of polymeric films for dye removal, with removal efficiencies ranging from 86.60% to 93.07% over six consecutive reuse cycles. Each cycle consisted of a 600 min removal process, simulating repeated practical applications. After the photocatalytic process, the polymeric fibers remained cylindrical, with several fractures. Diameter decreases of 31.61% and 7.95% were observed after the first and sixth cycles, respectively, with possible exposure of TiO₂. The vibrational spectra indicate changes in the bands at 1755 and 1714 cm⁻¹, attributed to C=O (PLA) and C-O (PBAT) stretches, respectively, suggesting a possible conformational change in the polymers. The thermal profiles showed only slight changes after the cycles. X-ray diffractograms indicate that degradation of the polymeric matrix leads to greater exposure of the embedded TiO₂ particles. The combined results from different characterization techniques provide evidence of the degradation of the polymeric material. Full article

Improvements to unsteady pressure-sensitive paint (uPSP) formulations have been realized by judicious selection of titanium dioxide (TiO₂) particles and dispersant. Traditionally, uPSP formulations based on polymer/ceramic coating have been used in many wind tunnel test campaigns but suffer from photodegradation and changes in pressure sensitivity during the testing window. As such, this paper details the investigation of employing different grades of TiO₂ particles and dispersants to achieve desirable characteristics such as coating properties, pressure sensitivity, frequency response and overall degradation. Employing hydrophobic TiO₂ particles along with a high-molecular-weight acrylic co-polymer generated uPSP coatings with many desirable features, including smoothness, thickness, and pressure sensitivity. In addition, the pressure sensitivity of the coatings exhibited linear behavior, having very little dependence on temperature. Finally, the frequency response was characterized qualitatively, and all uPSP formulations tested exhibited response to pressure fluctuations up to 12 kHz. Full article

Poly(methyl methacrylate) (PMMA) and its composites are widely used in industrial applications; therefore, their durability is of great concern. In this study, the photooxidative degradation behavior of nanosilica-filled PMMA composite films and the cooperative effect of mixed solvents containing tetrahydrofuran (THF) and chloroform (TCM), as well as interfacial functional groups, was investigated. The surface functional groups of nanosilica fillers, such as polar, aryl, and alkyl moieties, significantly affect the photodegradation kinetics and pathways for PMMA. The key process lies in the modulation of solvent–solvent reaction selectivity at the polymer–filler interface. Functional groups that selectively promote the chlorination reaction between THF and TCM accelerate PMMA photodepolymerization, while those that suppress this reaction hinder degradation. This interfacial effect is validated by trends in molecular weight loss, volatile product profiles, and MMA yields during aging. Our findings reveal that the photodegradation behavior of PMMA composites is not only governed by environmental conditions but also critically influenced by interfacial chemistry. In this way, this study provides novel insight into the interfacial aging process for polymer nanocomposites, as well as guidance for the rational design of PMMA-based materials with improved durability. Full article

The development of sustainable and functional nanocomposites has attracted considerable attention in recent years due to their broad spectrum of potential applications, including wood preservation. Also, a global goal is to reuse the large volumes of waste for environmental issues. In this context, the aim of the study was to obtain soda lignin particles, to graft ZnO nanoparticles onto their surface and to apply these hybrids, embedded into a biodegradable polymer matrix, as protection/preservation coating for oak wood. The organic–inorganic hybrids were characterized in terms of compositional, structural, thermal, and morphological properties that confirm the efficacy of soda lignin extraction and ZnO grafting by physical adsorption onto the decorating support and by weak interactions and coordination bonding between the components. The developed solution based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and lignin-ZnO was applied to oak wood specimens by brushing, and the improvement in hydrophobicity (evaluated by water absorption that decreased by 48.8% more than wood, humidity tests where the treated sample had a humidity of 4.734% in comparison with 34.911% for control, and contact angle of 97.8° vs. 80.5° for untreated wood) and UV and fungal attack protection, while maintaining the color and aspect of specimens, was sustained. L.ZnO are well dispersed into the polymer matrix, ensuring a smooth and less porous wood surface. According to the results, the obtained wood coating using both a biodegradable polymeric matrix and a waste-based preservative can be applied for protection against weathering degradation factors, with limited water uptake and swelling of the wood, UV shielding, reduced wood discoloration and photo-degradation, effective protection against fungi, and esthetic quality. Full article

This study focuses on the influence of prolonged ultraviolet (UV) irradiation on the mechanical properties and surface microstructure of glass fiber-reinforced plastics (GFRPs) and basalt fiber-reinforced plastics (BFRPs), which are widely used in construction and transport infrastructure. The relevance of the research lies in the need to improve the reliability of composite materials under extended exposure to harsh climatic conditions. Experimental tests were conducted in a laboratory UV chamber over 2000 h, simulating accelerated weathering. Mechanical properties were evaluated using three-point bending, while surface conditions were assessed via profilometry and microscopy. It was shown that GFRPs exhibit a significant reduction in flexural strength—down to 59–64% of their original value—accompanied by increased surface roughness and microdefect depth. The degradation mechanism of GFRPs is attributed to the photochemical breakdown of the polymer matrix, involving free radical generation, bond scission, and oxidative processes. To verify these mechanisms, FTIR spectroscopy was employed, which enabled the identification of structural changes in the polymer phase and the detection of mass loss associated with matrix decomposition. In contrast, BFRP retained up to 95% of their initial strength, demonstrating high resistance to UV-induced aging. This is attributed to the shielding effect of basalt fibers and their ability to retain moisture in microcavities, which slows the progress of photo-destructive processes. Comparison with results from natural exposure tests under extreme climatic conditions (Yakutsk) confirmed the reliability of the accelerated aging model used in the laboratory. Full article

Due to its excellent visible light absorption characteristics, the photocurrent, photodegradation, and proton conductivity of the stable dipyridyl and thiophene-functionalized supramolecular compound [Cu₂(TAA)₄(4,4′-bpy)]_n (Cu^II₂ for short, HTAA = 2-thiopheneacetic acid, 4,4′-bpy = 4,4′-bipyridine) have been studied in detail. The current density of photocurrent of Cu^II₂ is 1.87 μA·cm⁻², and Cu^II₂ degrades methylene blue (MB) with a degradation efficiency of 68.0% under xenon lamp. In addition, Cu^II₂ shows remarkable proton conductivity of 1.79 × 10⁻³ S·cm⁻¹ (at 75 °C and 98% relative humidity), superior to most copper(II)-based coordination polymers (CPs), and is expected to become a potential proton conductor in the future. Full article

The influence of structural water in alumina (Al₂O₃) and silica (SiO₂) coated titanium dioxide (TiO₂) pigments on the photodegradation behavior of polypropylene (PP) composites was investigated. Four commercial rutile TiO₂ pigments with varying surface inorganic coatings were incorporated into PP plaques and subjected to accelerated UV weathering to simulate outdoor exposure. Photodegradation was assessed through gloss retention measurements, the carbonyl index (CI), and stress at break retention, while pigment morphology and composition were analyzed using transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Surface charge and water content were determined through the zeta potential (ζ), Karl Fischer titration, thermogravimetric analysis (TGA), and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The results showed that low-alumina coating alone led to the lowest photodegradation resistance, the highest CI, and the lowest stress at break retention. In contrast, increasing alumina content enhanced photostability, reaching its maximum for combined alumina–silica coatings, which mitigated electron–hole pair migration. PP composites with high alumina–silica-coated TiO₂ exhibited higher gloss retention (36%) compared to low-alumina samples (21%). Furthermore, statistical analysis using ANOVA revealed significant differences in coating content and ζ potential among the pigment grades. These findings provide novel insights into oxide-water interactions and the impact of structural water on the photodegradation of polymer composites. Full article

The present study reports the application of three copper(II) coordination polymers, namely ¹_∞[Cu₃L₂(N₃)] CH₃COO (CP1), ¹_∞[Cu₃L₂(NO₃)]NO₃·2CH₃OH·2H₂O (CP2), and ¹_∞[Cu₃L₂(H₂O)](ClO₄)₂ (CP3), where H₂L stands for N,N′-bis[(2-hydroxybenzilideneamino)propyl]-piperazine) as catalysts for photocatalytic degradation of Acid Orange 7 and Methyl Orange dyes from single and binary aqueous solutions. The influence of the photocatalyst nature, hydrogen peroxide presence, reaction time, dye concentration, and catalyst dose on the photodegradation efficiency was studied. Under visible light irradiation, complex CP1 demonstrated the highest photodegradation efficiency of 92.40% and 80.50% towards Acid Orange 7 and Methyl Orange, respectively. The kinetic studies indicated that the photodegradation process followed a pseudo-first-order kinetics. The highest rate of the degradation process was obtained when CP1 is used, and the necessary time for the degradation of the dyes increases with increasing concentration of the dye solutions. The degradation efficiency of more than 75% after five recycling/reuse cycles of CP1 and the yields higher than 72% obtained for the degradation of dyes from the binary system demonstrate the photocatalytic capacity of CP1. A photocatalytic oxidation mechanism was proposed and the stability of the CP1 complex before and after the photodegradation process of dyes, both from simple and binary solutions, was investigated and confirmed. Full article

Organic solar cells (OSCs) have witnessed significant advancements in recent years, largely propelled by innovations in material design and device engineering. Among the emerging materials, dimerized small-molecule acceptors (DSMAs) have garnered considerable attention due to their unique advantages. For instance, DSMAs can directly inherit the excellent optoelectronic properties of corresponding small-molecule monomers. Moreover, their relatively larger molecular weight can effectively suppress molecular diffusion in the active layer, thereby enhancing the stability of OSCs. Compared to polymer acceptors, DSMAs have a well-defined structure, which is free from batch-to-batch variability, greatly enhancing the reproducibility of devices. This review comprehensively summarizes recent progress in DSMAs for OSCs, with a focus on their two primary linkage configurations: conjugative and non-conjugative connections. Additionally, the impact of various connection positions (including core-unit, end-group, and side-chain connection sites) on molecular packing, optoelectronic properties, and device performance is systematically reviewed. The review highlights the critical role of DSMAs in addressing key challenges in OSCs, such as photodegradation and morphological instability, while balancing power conversion efficiency and long-term stability. By consolidating recent breakthroughs and identifying future research directions, this work aims to provide valuable insights into the rational design of DSMAs, paving the way for the development of high-performance and commercially viable OSCs. Full article

Reducing the ecological impact of dyes through wastewater discharge into the environment is a challenge that must be addressed in textile wastewater pollution prevention. Congo red (CR) dye is widely used in experimental studies for textile wastewater treatment due to its high organic loads used in its preparation. The degradation of organic dyes of the CR type was investigated using the photocatalytic activity of functionalized polymers. We have employed photodegradation procedures for both polymer-supported glycine groups (Code: AP2) and polymer-supported glycine-Zn(II) (Code: AP2-Zn(II)). A photocatalysis efficiency of 89.2% was achieved for glycine pendant groups grafted on styrene-6.7% divinylbenzene copolymer (AP2) and 95.4% for the AP2-Zn(II) sample by using an initial concentration of CR of 15 mg/L, a catalyst concentration of 1 g/L, and 240 min of photocatalysis. The findings provided here have shown that the two materials (AP2 and AP2-Zn(II)) may be effectively employed in the heterogeneous photocatalysis method to remove CR from water. From the perspective of the degradation mechanism of CR, the two photocatalysts act similarly. Full article

Stimulus-responsive hydrogels have emerged as versatile materials for environmental and wastewater treatment applications due to their ability to adapt to changing environmental conditions. This review highlights recent advances in the design, synthesis, and functionalization of such hydrogels, focusing on their environmental applications. Various synthesis techniques, including radical polymerization, grafting, and copolymerization, enable the development of hydrogels with tailored properties such as enhanced adsorption capacity, selectivity, and reusability. The incorporation of nanoparticles and bio-based polymers further improves their structural integrity and pollutant removal efficiency. Key mechanisms such as adsorption, ion exchange, and photodegradation are discussed, emphasizing their roles in removing heavy metals, dyes, and organic pollutants from wastewater. Additionally, this review presents the potential of hydrogels for oil–water separation, pathogen control, and future sustainability through integration into circular economy frameworks. The adaptability, cost-effectiveness, and eco-friendliness of these hydrogels make them promising candidates for large-scale environmental remediation. Full article

The present article focuses on the characterization of the new biocomposites of poly(butylene succinate) (PBS) with fillers of plant origin such as onion peels (OP) and durum wheat bran WB (Triricum durum) subjected to composting and artificial aging. The susceptibility to fungal growth, cytotoxicity and antibacterial properties were also examined. The biodegradation of the samples was investigated under normalized conditions simulating an intensive aerobic composting process. It was shown that the tested natural fillers significantly accelerate the biodegradation process of the composition (after 90 days mass loss of PBS 7%) and that the samples with WB degrade much faster (corresponding mass loss 86%) than those containing OP (corresponding mass loss 21%). The remains of the samples after composting were subjected to chemical structure analysis (FTIR), and their thermal properties were determined using differential scanning calorimetry (DSC). It was shown that the degree of crystallinity of PBS and composites increased with the increasing time of composting. In the case of pure PBS, this increase was a maximum of 31.5%, for biocomposite with OP 31.1% and for those containing WB 21.2%. FTIR results showed that cleavage of polymer chains by hydrolysis took place during composting. The tested samples were also subjected to artificial aging under conditions simulating solar radiation and were sprayed with water. After artificial aging, the significant changes in the color of the samples as well as the porosity of their surface was noted, which was mainly due to the effect of photodegradation of both the used OP and WB fillers. Additionally, FTIR analysis indicated that samples were degraded by photooxidation processes. The ability of fungi to grow on the surface of the samples was also tested. The results demonstrate the possibility of using the developed biocomposite materials as a carbon source for the growth of fungi. The antibacterial tests showed that samples containing OP exhibited strong antibacterial properties regardless of their wt.% content. Additionally, a cytotoxicity test was performed on a BJ cell line, demonstrating that none of the tested biocomposites were cytotoxic. Moreover, those with the addition of WB statistically significantly supported the viability of both fibroblast and bacteria cells, showing their biological safety but lack of antibacterial activity. Full article

The concept of using polyaniline/titanium dioxide heterostructures as efficient photocatalysts is based on the synergistic effect of conducting polymer and metal oxide semiconductors. Due to inconclusive literature reports, the effect of different polyaniline/TiO₂ ratios on photocatalytic activity under UV and visible light was investigated. In most papers, non-recommended dyes are used as model compounds to evaluate visible light activity. Therefore, colorless phenol was used instead of dyes in this study to clarify the real visible light-induced photocatalytic activity of polyaniline/TiO₂ composites. This publication also includes a discussion of whether materials derived from bulk (non-nanostructured) polyaniline and TiO₂ by the standard in situ oxidative polymerization method are suitable candidates for promising photocatalytic materials. The evaluation of photocatalytic activity was performed in both UV and visible light systems. X-ray diffraction and UV-Vis diffuse reflectance spectroscopy methods were applied to characterize the obtained samples. Obtained polyaniline (pure and in composites) was identified as emeraldine salt. In the UV system, none of the prepared samples with different polyaniline–titania ratios had activity better than reference P25 titania. It has been observed that the presence of polyaniline adversely affects the photocatalytic properties, as the polyaniline layer covering the titania surface can shield the UV light transmission by blocking the contact between the TiO₂ surface and organic molecules. In the case of using visible light, no synergies have been observed between polyaniline and titania either. The photodegradation efficiencies of the most active samples were similar to those of pure polyaniline. In conclusion, in order to obtain efficient polyaniline/titania photocatalysts active in UV and/or visible light, it is necessary to take into account the morphological and surface properties of both components. Full article