Search Results (75)

Asphalt binder aging under natural exposure critically determines pavement durability, though current research inadequately captured performance evolution across diverse regional climates. This study investigated climate-driven degradation mechanisms through 12-month all-weather aging (AWA) tests in Gansu, Shandong, and Beijing via rheological (G-R parameter, stiffness modulus S-value) and chemical analyses (carbonyl index I_C=O, sulfoxide index I_S=O). The results demonstrated significant region-dependent aging disparities beyond laboratory simulation. In Gansu, extreme thermal fluctuations and UV radiation accelerated hardening via thermal stress cycles and photo-oxidation, yielding 52.4% higher G-R parameter than PAV. In Shandong, humid saline environments triggered sulfur oxidation-driven electrochemical corrosion, increasing I_S=O by 4.2% compared to PAV. In Beijing, synergistic UV–thermal oxidation elevated I_C=O and S-value by 8% and 40.7%, respectively versus PAV. Critically, I_C=O exhibited strong positive correlations with rheological degradation across regions (r > 0.90, p < 0.01). Based on I_C=O, the 12-month all-weather aging rate in Beijing exceeded Gansu and Shandong by 18.5% and 68%, revealing UV–thermal coupling as the most severe degradation pattern. Novelty lies in quantifying region-specific multi-factor coupling effects (UV–thermal, hygrothermal–salt, etc.) and demonstrating their superior severity over PAV (Beijing > Gansu > Shandong). Dominant environmental factors showed distinct regional variations: UV radiation and temperature difference dominated in Gansu (I_C=O, r = 0.76) and Beijing (0.74), while precipitation—I_C=O correlation prevailed in Shandong (0.76), yet multi-factor coupling ultimately governed aging. These findings provide theoretical foundations for region-tailored and climate-resilient asphalt pavement design. Full article

With the increase in biodiesel production experienced in the last decades, biomass-derived glycerol is obtained at a high rate, so glycerol availability in the market has scaled up while this polyol price has been reduced, with the exception of high-quality glycerol. In this context, novel and sustainable products based on glycerol are actively looked for. Octyl-methoxycinnamate (OMC) is a common cosmetic ingredient and sunscreen with potential activity as an endocrine disruptor that is considered an emergent contaminant in aquatic environments. As possible substituents, glycerol-based methoxycinnamates such as monoglycerides can be obtained via lipase-driven esterification. In this work, we develop an enzymatic process under solventless conditions to obtain p-methoxycinnamate monoglyceride under mild conditions using Novozym 435—an immobilized industrial preparation of the lipase B of Candida antarctica—observing the effect of key process variables such as temperature and enzyme, water and acid concentrations. Furthermore, the obtained product was assessed for its activity as UVB-filter and for its stability under irradiation conditions, showing a similar SPF activity and a much higher stability toward photooxidation than OMC. Full article

Photooxidation imposes structural damage on proteins, and the amino acid tryptophan (Trp) is a key target for protein oxidation. The Trp radical cation (Trp^•⁺), as an oxidative product, can be reduced by plant phenols (φ-OH), a category of dietary phytochemicals essential for human health. This work is intended to investigate the efficacy of φ-OH regeneration of Trp from Trp^•⁺ as a function of φ-OH concentration and environmental pH. We have examined, by using laser flash photolysis, six different kinds of φ-OH in the aqueous system consisting of Trp and riboflavin as a photosensitizer. Taking syringic acid (Syr) as an example, upon systematically varying the pH from 2 to 10, the partition of Syr phenolate, Syr-O²⁻, increases from 0% to 70% and, accordingly, the rate of Trp regeneration increases from 4.8 × 10⁶ M⁻¹·s⁻¹ to 1.7 × 10⁸ M⁻¹·s⁻¹. It is found that the regeneration rate correlates with the driving force of the electron transfer (ET) reaction between φ-OH and Trp^•+, which can be well accounted for by Marcus’s ET theory (R² = 0.89). The λ = 0.43 ± 0.08 eV for the reorganization energy for ET from the plant phenols to the Trp^•⁺. The effects of φ-OH concentration, environmental pH, and ET driving force on the Trp regeneration reaction herein revealed are significant for enlightening further study of protein (anti)oxidation. Full article

Changes in the environment have a significant impact on photosynthetic efficiency, which in turn influences plant growth and yield. Consequently, there is a greater focus on methods to enhance photosynthetic efficiency with the goal of raising plant productivity. In this study, the effects of titanium oxide nanoparticles (TiO₂ NPs) on pea plants (Pisum sativum L.) subjected to moderate salt stress by the addition of 100 mM NaCl to the nutrient solution were investigated. Two concentrations of NPs (50 mg/L and 100 mg/L) were applied through foliar spray on pea leaves. Data showed that NPs prevent salt-induced membrane damage, growth inhibition, and the increase in hydrogen peroxide and lipid peroxidation. An analysis of the chlorophyll fluorescence curves revealed that TiO₂ NPs decreased the effects of NaCl on the reduction in the open photosystem II centers (corresponding with qp) and their efficiency (Φexc), as well as the activity of the oxygen-evolving complex (Fv/Fo). The co-treatment with TiO₂ NPs and NaCl also improved the photochemical energy conversion of photosystem II (Φ_PSII), alleviated the interaction of Q_A⁻ with plastoquinone, and enhanced electron transport activity and the rate of photosynthesis, compared to the plants treated with NaCl only. Additionally, NPs application under salt stress stimulated cyclic electron transport around photosystem I, thus protecting its photochemical activity. These protective effects of NPs were more pronounced at a concentration of 100 mg/L. Full article

Solar-driven catalytic oxidation processes for the removal of toxic gaseous pollutants have attracted considerable scientific attention, and there is a strong desire to improve the mass transfer, photogenerated charge separation, and O₂ activation by regulating the structure of the photocatalyst. Initially, functionalized graphene–TiO₂ mesoporous hollow nanofibers have been controllably fabricated by a coaxial electrospinning technique, in which functionalized graphene is controllably prepared through a sequential diazonium functionalization and silane modification and ensures its uniform distribution among TiO₂ nanoparticles (NPs). Subsequently, the ultrafine Ag NPs are primarily anchored onto the surface of graphene by an in situ frozen photodeposition strategy, producing Ag/functionalized graphene–TiO₂ mesoporous hollow nanofibers (Ag/SiG-TO MPHNFs). The optimal Ag/SiG-TO MPHNFs exhibit 3.9-fold and 4.6-fold enhancements in CO photooxidation compared with TO MPHNFs and P25 TiO₂, respectively. The enhanced photoactivity can be attributed to three factors: the creation of the mesoporous hollow structure accelerates mass transfer, the incorporation of graphene facilitates the transfer of photogenerated electrons from TiO₂ to graphene, and the anchoring of Ag NPs improves O₂ activation. Full article

Previously synthesized and tested water-dispersible photoactive polymeric microparticles have been employed as heterogenous photosensitizers to evaluate their performance in generating singlet oxygen through direct solar irradiation. This study utilizes these photocatalysts for the degradation of Acetamiprid in IWWTP wastewater effluents from the Agri-food industry, exploring, in addition to direct or simulated solar irradiation, the influence of pH on the photooxidation process. Over a thousand emerging pollutants, including pesticides like Acetamiprid, have been detected in aquatic environments in recent years, posing challenges due to the limitations of current wastewater treatment technologies. The developed method is particularly effective under basic or slightly basic conditions, aligning with the natural pH of wastewater and addressing a limitation of conventional Acetamiprid degradation methods, which typically require medium acidification to be effective. Polymers P3 and P4 exhibited high photocatalytic activity, achieving over 99% degradation of Acetamiprid through oxidation via singlet oxygen generated by Rose Bengal supported on the polymer matrix, while maintaining catalytic efficiency across multiple cycles. The results confirm that Acetamiprid removal from industrial wastewater via direct solar irradiation is feasible, though constrained by the availability of sufficient effective sunlight hours. Full article

Barium titanate photocatalysts were synthesized via a sol–gel method involving a unique, cost-effective calcination technique that includes rapid heating and short exposure. The samples were characterized by X-ray diffractometry, scanning electron microscopy, diffuse reflectance spectroscopy, photoluminescence spectroscopy, infrared spectroscopy, and nitrogen adsorption–desorption measurements. The photooxidation activity and stability of the samples were evaluated by the degradation of phenol, oxalic acid, and chlorophenol. Their photoreduction activity was also investigated by the photocatalytic conversion of CO₂ to CO. In both cases, UV irradiation was applied to activate the catalysts. As references, commercially available cubic and tetragonal barium titanates were used, with the addition of benchmark P25 TiO₂ in some cases. Increasing the calcination temperature resulted in increased primary crystallite sizes, decreased specific surface areas, and slightly redshifted band gaps. On the one hand, the overall photooxidation activity of the samples for pollutant degradation was rather low, possibly due to their unfavorable valence band maximum position. On the other hand, our samples displayed significantly superior photoreduction activity, surpassing that of all the references, including P25 TiO₂. The high photoactivity was mainly attributed to the specific surface areas that changed per the efficiency of the samples. Last, the cost comparison calculations showed that applying our calcination technique is 29.5% more cost-efficient than conventional calcination, and the same amount of energy is sufficient for preparing even a 1.4 times higher amount of barium titanite. Full article

The effect of a natural polysaccharide (hyaluronic acid (HA)) on the photocatalytic activity of methylene blue (MB) was studied both under model conditions (a tryptophan photooxidation reaction in water) and with in vitro experiments on P. aeruginosa and S. aureus bacterial cultures. It was shown spectrophotometrically that, in the presence of HA, an increase in the optical density of the absorption bands λ = 665 nm and 620 nm—which correspond to the monomeric and dimeric forms of the dye, respectively—was observed in the EAS of the dye, while the ratio of the optical density of these bands remained practically unchanged. When adding HA to MB, the intensity of singlet oxygen ¹O₂ photoluminescence and the degree of fluorescence polarization of MB increase. The observed effects are associated with the disaggregation of molecular associates of the dye in the presence of HA. The maximum increase in the photocatalytic activity of MB (by 1.6 times) was observed in the presence of HA, with concentrations in a range between 0.0015 wt.% and 0.005 wt.%. Full article

Photosynthesis is initiated when the sun’s light induces electron transfer from chlorophyll to plastoquinone, a para-quinone. While photosynthesis occurs in the intact chloroplasts of living plants, similar photochemical reactions between dietary chlorophyll metabolites and quinones are likely and may affect health outcomes. Herein, we continue our studies of the direct photoreduction of para-quinones and ortho-quinones that were generated by the photo-oxidation of catechols. Chlorophyll metabolites, including pheophorbide A, chlorin e6, and pyropheophorbide A, as well as methylene blue were employed as photosensitizers. We detected hydrogen peroxide using horseradish peroxidase following the photo-oxidation of the catechol dopamine, even in the presence of EDTA, a tertiary amine electron donor. Under ambient oxygen, hydrogen peroxide was also detected after the photoreduction of several para-quinones, including 2,3-dimethoxy-5-methyl-p-benzoquinone (CoQ₀), methoxy-benzoquinone, and methyl-benzoquinone. The combinations of methylene blue and EDTA or pheophorbide A and triethanolamine as the electron donor in 20% dimethylformamide were optimized for photoreduction of the para-quinones. Chlorin e6 and pyropheophorbide A were less effective for the photoreduction of CoQ₀ but were equivalent to pheophorbide A for generating hydrogen peroxide in photo-oxidation reactions with photosensitizers, oxygen, and triethanolamine. We employed dinitrophenylhydrazine to generate intensely colored adducts of methoxy-benzoquinone, methyl-benzoquinone, and 1,4-benzoquinone. Full article

In the quest to combat global warming, traditional thermal chemistry processes are giving way to selective photocatalysis, an eco-friendly approach that operates under milder conditions, using benign solvents like water. Benzaldehyde, a versatile compound with applications spanning agroindustry, pharmaceuticals, and cosmetics, serves as a fundamental building block for various fine chemicals. This study aims at enhancing benzaldehyde production sustainability by utilizing photooxidation of benzyl alcohol. Gold nanoparticle-based catalysts are renowned for their exceptional efficiency in oxidizing bio-based molecules. In this research, Au nanoparticles were anchored onto three distinct supports: $\mathrm{T}\mathrm{i}{\mathrm{O}}_2$, $\mathrm{Z}\mathrm{r}{\mathrm{O}}_2$, and graphitic carbon nitride (g-${\mathrm{C}}_3{\mathrm{N}}_4$). The objective was to investigate the influence of the support material on the selective photocatalysis of benzyl alcohol. In the preparation of g-${\mathrm{C}}_3{\mathrm{N}}_4$, three different precursors—melamine, urea, and a 50:50 mixture of both—were chosen to analyze their impact on catalyst performance. After 4 h of irradiation at 365 nm, operating under acidic conditions (pH = 2), the Au photocatalyst on graphitic carbon nitride support synthesized using urea precursor (Au@g-${\mathrm{C}}_3{\mathrm{N}}_{4\left(urea\right)}$) displayed the optimal balance between conversion (75%) and selectivity (85%). This formulation outperformed the benchmark Au@TiO₂, which achieved a similar conversion rate (80%) but exhibited lower selectivity (55%). Full article

Researchers have described protection mechanisms against the photoinhibition of photosystems under strong-light stress. Cyclic Electron Flow (CEF) mitigates electron acceptor-side limitation, and thus contributes to Photosystem I (PSI) protection. Chloroplast protease removes damaged protein to assist with protein turn over, which contributes to the quality control of Photosystem II (PSII). The PGR5 protein is involved in PGR5-dependent CEF. The FTSH protein is a chloroplast protease which effectively degrades the damaged PSII reaction center subunit, D1 protein. To investigate how the PSI photoinhibition phenotype in pgr5 would be affected by adding the ftsh mutation, we generated double-mutant pgr5ftsh via crossing, and its phenotype was characterized in the green algae Chlamydomonas reinhardtii. The cells underwent high-light incubation as well as low-light incubation after high-light incubation. The time course of Fv/Fm values in pgr5ftsh showed the same phenotype with ftsh1-1. The amplitude of light-induced P700 photo-oxidation absorbance change was measured. The amplitude was maintained at a low value in the control and pgr5ftsh during high-light incubation, but was continuously decreased in pgr5. During the low-light incubation after high-light incubation, amplitude was more rapidly recovered in pgr5ftsh than pgr5. We concluded that the PSI photoinhibition by the pgr5 mutation is mitigated by an additional ftsh1-1 mutation, in which plastoquinone pool would be less reduced due to damaged PSII accumulation. Full article

This research presents a comprehensive study on the application of hydroxypropyl cellulose/zinc oxide nanocomposite (HPC/ZnO NC) as an effective consolidant in leather conservation. The critical focus is to prevent photooxidative degradation, a significant challenge in preserving historical leather artifacts. The nanocomposite was evaluated for its protective capabilities against environmental stressors like UV radiation and moisture, mechanical robustness, and potential to stabilize acid-damaged leather. The uniform dispersion of ZnO NPs in the HPC matrix was revealed as crucial for improving leather properties, which was confirmed through SEM imaging. The HPC/ZnO NC coating effectively prevented UV-induced microcracks, surface degradation and collagen denaturation. It also demonstrated enhanced mechanical resistance, inhibiting the reduction in leather’s maximum tolerable force and increasing the elongation index, even after aging. Additionally, it exhibited improved water-repellent properties and increased the pH of the leather, offering potential benefits for the treatment of acid-degraded leathers. Overall, the findings affirm that the application of HPC/ZnO NC significantly augments the physical and mechanical properties of leather, providing enhanced resistance to environmental degradation. Full article

Photosensitization of proteins mediated by chromophores is a mechanism commonly employed by nature and mimicked in a broad array of laboratory research and applications. Nature has evolved specialized complexes of proteins and photosensitizers (PS) that assemble to form photoreceptor proteins (PRP). These are used by many organisms in diverse processes, such as energy conversion, protection against photodamage, etc. The same concept has been used in laboratory settings for many applications, such as the stimulation of neurons or the selective depletion of proteins in a signaling pathway. A key issue in laboratory settings has been the relationship between the photooxidation of proteins and conformational changes in host proteins. For several years, we have been interested in creating non-native PRP using porphyrin PS. In this study, we investigated the self-assembled complex between zinc protoporphyrin IX (ZnPPIX) and bovine β-lactoglobulin (BLG) as a model of non-native PRP. Since BLG undergoes a significant conformational transition near physiological pH, the study was carried out at acidic (pH 5) and alkaline (pH 9) conditions where the two conformations are respectively prevalent. We employed a series of steady-state and time-resolved optical spectroscopies as well as gel electrophoresis to experimentally characterize the photosensitization mechanisms and their effect on the host protein. Our results show that ZnPPIX prompts light-dependent modifications of BLG, which appear to be much more significant at alkaline pH. The modifications seem to be driven by photooxidation of amino acid residues that do not lead to the formation of cross-links or protein fragmentation. Full article

Glioblastoma is one of the most common and aggressive forms of brain tumor, a rare disease for which there is a great need for innovative therapies. ONC201, a new drug substance, has been used in a compassionate treatment program where the choice of dosage form and regimen have yet to be justified. The prior knowledge needed to anticipate ONC201 stability problems has recently been partially addressed, by (i) showing that ONC201 is sensitive to light and oxidation and (ii) identifying the molecular structures of the main degradation products formed. The aim of the work presented here was to improve our understanding of the degradation pathways of ONC201 using data from ab initio calculations and experimental work to supplement the structural information we already published. The C–H bonds located αto the amine of the tetrahydropyridine group and those located alpha to the imine function of the dihydroimidazole group exhibit the lowest bond dissociation energies (BDEs) within the ONC201 molecule. Moreover, these values drop well below 90 kcal.mol⁻¹ when ONC201 is in an excited state (S1; T1). The structures of the photoproducts we had previously identified are consistent with these data, showing that they would have resulted from radical processes following the abstraction of alpha hydrogens. Concerning ONC201’s sensitivity to oxidation, the structures of the oxidation products matched the critical points revealed through mapped electrostatic potential (MEP) and average local ionization energy (ALIE). The data obtained from ab initio calculations and experimental work showed that the reactivity of ONC201 to light and oxidation conditions is highly dependent on pH. While an acidic environment (pH < 6) contributes to making ONC201 quantitatively more stable in solution in the face of oxidation and photo-oxidation, it nevertheless seems that certain chemical groups in the molecule are more exposed to nucleophilic attacks, which explains the variation observed in the profile of degradation products formed in the presence of certain antioxidants tested. This information is crucial to better understand the stability results in the presence of antioxidant agents and to determine the right conditions for them to act. Full article

The molecular characteristics and formation mechanism of biogenic secondary organic aerosols (BSOAs) in the forested atmosphere are poorly known. Here, we report the temporal variations in and formation processes of BSOA tracers derived from isoprene, monoterpenes, and β caryophyllene in PM_2.5 samples collected at the foot of Mt. Huang (483 m a. s. l) in East China during the summer of 2019 with a 3 h time resolution. The concentrations of nearly all of the detected species, including organic carbon (OC), elemental carbon (EC), levoglucosan, and SIA (sum of SO₄²⁻, NO₃⁻, and NH₄⁺), were higher at night (19:00–7:00 of the next day) than in the daytime (7:00–19:00). In addition, air pollutants that accumulated by the dynamic transport of the mountain breeze at night were also a crucial reason for the higher BSOA tracers. Most of the BSOA tracers exhibited higher concentrations at night than in the daytime and peaked at 1:00 to 4:00 or 4:00 to 7:00. Those BSOA tracers presented strong correlations with O₃ in the daytime rather than at night, indicating that BSOAs in the daytime were primarily derived from the photo-oxidation of BVOCs with O₃. The close correlations of BSOA tracers with SO₄²⁻ and particle acidity (pH_is) suggest that BSOAs were primarily derived from the acid-catalyzed aqueous-phase oxidation. Considering the higher relative humidity and LWC concentration at night, the promoted aqueous oxidation was the essential reason for the higher concentrations of BSOA tracers at night. Moreover, levoglucosan exhibited a robust correlation with BSOA tracers, especially β-caryophyllinic acid, suggesting that biomass burning from long-distance transport exerted a significant impact on BSOA formation. Based on a tracer-based method, the estimated concentrations of secondary organic carbon (SOC) derived from isoprene, monoterpenes, and β caryophyllene at night (0.90 ± 0.57 µgC m⁻³) were higher than those (0.53 ± 0.34 µgC m⁻³) in the daytime, accounting for 14.5 ± 8.5% and 12.2 ± 5.0% of OC, respectively. Our results reveal that the BSOA formation at the foot of Mt. Huang was promoted by the mountain-valley breezes and anthropogenic pollutants from long-range transport. Full article