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Chemosphere Jun 2024Dimethylsilanediol (DMSD) is the common degradation product of ubiquitous polydimethylsiloxane (PDMS) and volatile methylsiloxanes (VMS) in water and soil. Given the...
Dimethylsilanediol (DMSD) is the common degradation product of ubiquitous polydimethylsiloxane (PDMS) and volatile methylsiloxanes (VMS) in water and soil. Given the high solubility of DMSD in water, the further degradation of DMSD in this compartment is of particular importance. While DMSD appears relatively resistant to degradation in standard hydrolysis or biodegradation studies, it may degrade by indirect photolysis in surface waters through oxidation by hydroxyl radicals. The formation of hydroxyl radicals is governed by nitrate ions or other promoters in the presence of sunlight. In this study, we investigated the impact of nitrate ions on the oxidative decomposition of DMSD in water under simulated solar light. When exposed to solar light, DMSD can degrade all the way to the natural, mineralized substances, namely carbon dioxide (in the form of carbonic acid) and silicic acid, via the intermediate methylsilanetriol (MST).
PubMed: 38909861
DOI: 10.1016/j.chemosphere.2024.142670 -
ACS Applied Polymer Materials Jun 2024Four-dimensional printing with embedded photoluminescence is emerging as an exciting area in additive manufacturing. Slim polymer films patterned with three-dimensional...
Four-dimensional printing with embedded photoluminescence is emerging as an exciting area in additive manufacturing. Slim polymer films patterned with three-dimensional lattices of multimode cylindrical waveguides (waveguide-encoded lattices, WELs) with enhanced fields of view can be fabricated by localizing light as self-trapped beams within a photopolymerizable formulation. Luminescent WELs have potential applications as solar cell coatings and smart planar optical components. However, as luminophore-photoinitiator interactions are expected to change the photopolymerization kinetics, the design of robust luminescent photopolymer sols is nontrivial. Here, we use model photopolymer systems based on methacrylate-siloxane and epoxide homopolymers and their blends to investigate the influence of the luminophore Lumogen Violet () on the photolysis kinetics of the Omnirad 784 photoinitiator through UV-vis absorbance spectroscopy. Initial rate analysis with different bulk polymers reveals differences in the pseudo-first-order rate constants in the absence and presence of , with a notable increase (∼40%) in the photolysis rate for the 1:1 blend. Fluorescence quenching studies, coupled with density functional theory calculations, establish that these differences arise due to electron transfer from the photoexcited to the ground-state photoinitiator molecules. We also demonstrate an in situ UV-vis absorbance technique that enables real-time monitoring of both waveguide formation and photoinitiator consumption during the fabrication of WELs. The in situ photolysis kinetics confirm that -photoinitiator interactions also influence the photopolymerization process during WEL formation. Our findings show that luminophores play a noninnocent role in photopolymerization and highlight the necessity for both careful consideration of the photopolymer formulation and a real-time monitoring approach to enable the fabrication of high-quality micropatterned luminescent polymeric films.
PubMed: 38903400
DOI: 10.1021/acsapm.4c00484 -
Pollutant Photodegradation Affected by Evaporative Water Concentration in a Climate Change Scenario.Molecules (Basel, Switzerland) Jun 2024Evaporative water concentration takes place in arid or semi-arid environments when stationary water bodies, such as lakes or ponds, prevalently lose water by...
Evaporative water concentration takes place in arid or semi-arid environments when stationary water bodies, such as lakes or ponds, prevalently lose water by evaporation, which prevails over outflow or seepage into aquifers. Absence or near-absence of precipitation and elevated temperatures are important prerequisites for the process, which has the potential to deeply affect the photochemical attenuation of pollutants, including contaminants of emerging concern (CECs). Here we show that water evaporation would enhance the phototransformation of many CECs, especially those undergoing degradation mainly through direct photolysis and triplet-sensitized reactions. In contrast, processes induced by hydroxyl and carbonate radicals would be inhibited. Our model results suggest that the photochemical impact of water evaporation might increase in the future in several regions of the world, with no continent likely being unaffected, due to the effects of local precipitation decrease combined with an increase in temperature that facilitates evaporation.
PubMed: 38893529
DOI: 10.3390/molecules29112655 -
Molecules (Basel, Switzerland) Jun 2024Chamazulene (CA) is an intensely blue molecule with a wealth of biological properties. In cosmetics, chamazulene is exploited as a natural coloring and soothing agent....
Chamazulene (CA) is an intensely blue molecule with a wealth of biological properties. In cosmetics, chamazulene is exploited as a natural coloring and soothing agent. CA is unstable and tends to spontaneously degrade, accelerated by light. We studied the photodegradation of CA upon controlled exposure to UVB-UVA irradiation by multiple techniques, including GC-MS, UHPLC-PDA-ESI-MS/MS and by direct infusion in ESI-MS, which were matched to in silico mass spectral simulations to identify degradation products. Seven byproducts formed upon UVA exposure for 3 h at 70 mW/cm (blue-to-green color change) were identified, including CA dimers and CA benzenoid, which were not found on extended 6 h irradiation (green-to-yellow fading). Photostability tests with reduced irradiance conducted in various solvents in the presence/absence of air indicated highest degradation in acetonitrile in the presence of oxygen, suggesting a photo-oxidative mechanism. Testing in the presence of antioxidants (tocopherol, ascorbyl palmitate, hydroxytyrosol, bakuchiol, γ-terpinene, TEMPO and their combinations) indicated the highest protection by tocopherol and TEMPO. Sunscreens ethylhexyl methoxycinnamate and particularly Tinosorb S (but not octocrylene) showed good CA photoprotection. Thermal stability tests indicated no degradation of CA in acetonitrile at 50 °C in the dark for 50 days; however, accelerated degradation occurred in the presence of ascorbyl palmitate.
Topics: Azulenes; Oils, Volatile; Oxidation-Reduction; Photolysis; Ultraviolet Rays; Antioxidants; Achillea; Artemisia; Tandem Mass Spectrometry; Gas Chromatography-Mass Spectrometry
PubMed: 38893479
DOI: 10.3390/molecules29112604 -
International Journal of Molecular... May 2024Advanced oxidation processes, including photocatalysis, have been proven effective at organic dye degradation. Tailored porous materials with regulated pore size, shape,...
Advanced oxidation processes, including photocatalysis, have been proven effective at organic dye degradation. Tailored porous materials with regulated pore size, shape, and morphology offer a sustainable solution to the water pollution problem by acting as support materials to grafted photocatalytic nanoparticles (NPs). This research investigated the influence of pore and particle sizes of photocatalytic MICROSCAFS on the degradation of methyl orange (MO) in aqueous solution (10 mg/L). Photocatalytic MICROSCAFS are made of binder-less supported P25 TiO NPs within MICROSCAFS, which are silica-titania microspheres with a controlled size and interconnected macroporosity, synthesized by an adapted sol-gel method that involves a polymerization-induced phase separation process. Photocatalytic experiments were performed both in batch and flow reactors, with this latter one targeting a proof of concept for continuous transformation processes and real-life conditions. Photocatalytic degradation of 87% in 2 h (batch) was achieved, using a calibrated solar light simulator (1 sun) and a photocatalyst/pollutant mass ratio of 23. This study introduces a novel flow kinetic model which provides the modeling and simulation of the photocatalytic MICROSCAFS performance. A scavenger study was performed, enabling an in-depth mechanistic understanding. Finally, the transformation products resulting from the MO photocatalytic degradation were elucidated by high-resolution mass spectrometry experiments and subjected to an in silico toxicity assessment.
Topics: Catalysis; Water Purification; Titanium; Water Pollutants, Chemical; Porosity; Sunlight; Azo Compounds; Microspheres; Silicon Dioxide; Photolysis; Kinetics; Photochemical Processes
PubMed: 38892146
DOI: 10.3390/ijms25115958 -
Scientific Reports Jun 2024A composite of Zinc oxide loaded with 5-weight % silver decorated on carbon nanotubes (Ag-loaded ZnO: CNT) was synthesized using a simple refluxed chemical method. The...
A composite of Zinc oxide loaded with 5-weight % silver decorated on carbon nanotubes (Ag-loaded ZnO: CNT) was synthesized using a simple refluxed chemical method. The influence of deviation in the weight % of carbon nanotube loading on photocatalytic dye degradation (methylene blue and rose bengal) and antibiotic (antimicrobial and antifungal) performance was investigated in this study. The light capture ability of Ag-loaded ZnO:CNT in the visible region was higher in photocatalytic activity than that of Ag-loaded ZnO and ZnO:CNT. The bandgap of the Ag-loaded ZnO: CNT was tuned owing to the surface plasmon resonance effect. The photocatalytic degradation investigations were optimized by varying the wt% in CNTs, pH of dye solution, concentration of the dye solution, and amount of catalytic dose. Around 100% photocatalytic efficiency in 2 min against MB dye was observed for Ag doped ZnO with 10 wt% CNT composite at pH 9, at a rate constant 1.48 min. Bipolaris sorokiniana fungus was first time tested against a composite material, which demonstrated optimum fungal inhibition efficiency of 48%. They were also tested against the bacterial strains Staphylococcus aureus, Bacillus cerius, Proteus vulgaris, and Salmonella typhimurium, which showed promising antibacterial activity compared to commercially available drugs. The composite of Ag doped ZnO with 5 wt% CNT has shown competitive zone inhibition efficacy of 21.66 ± 0.57, 15.66 ± 0.57, 13.66 ± 0.57 against bacterial strains Bacillus cerius, Proteus vulgaris, and Salmonella typhimurium which were tested for the first time against Ag-loaded ZnO:CNT.
Topics: Zinc Oxide; Silver; Nanotubes, Carbon; Anti-Bacterial Agents; Catalysis; Antifungal Agents; Staphylococcus aureus; Methylene Blue; Coloring Agents; Rose Bengal; Microbial Sensitivity Tests; Salmonella typhimurium; Hydrogen-Ion Concentration; Photolysis; Photochemical Processes
PubMed: 38890495
DOI: 10.1038/s41598-024-64746-6 -
Beilstein Journal of Organic Chemistry 2024Organic photocatalysts frequently possess dual singlet and triplet photoreactivity and a thorough photochemical characterization is essential for efficient light-driven...
Organic photocatalysts frequently possess dual singlet and triplet photoreactivity and a thorough photochemical characterization is essential for efficient light-driven applications. In this article, the mode of action of a polyazahelicene catalyst (Aza-H) was investigated using laser flash photolysis (LFP). The study revealed that the chromophore can function as a singlet-state photoredox catalyst in the sulfonylation/arylation of styrenes and as a triplet sensitizer in energy transfer catalysis. The singlet lifetime is sufficiently long to exploit the exceptional excited state reduction potential for the activation of 4-cyanopyridine. Photoinduced electron transfer generating the radical cation was directly observed confirming the previously proposed mechanism of a three-component reaction. Several steps of the photoredox cycle were investigated separately, providing deep insights into the complex mechanism. The triplet-excited Aza-H, which was studied with quantitative LFP, is formed with a quantum yield of 0.34. The pronounced triplet formation was exploited for the isomerization reaction of ()-stilbene to the -isomer and the cyclization of cinnamyl chloride. Catalyst degradation mainly occurs through the long-lived Aza-H triplet (28 µs), but the photostability is greatly increased when the triplet efficiently reacts in a catalytic cycle such that turnover numbers exceeding 4400 are achievable with this organocatalyst.
PubMed: 38887585
DOI: 10.3762/bjoc.20.106 -
Journal of Molecular Biology Jun 2024Heliorhodopsin (HeR) is a new rhodopsin family discovered in 2018 through functional metagenomic analysis. Similar to microbial rhodopsins, HeR has an all-trans retinal...
Heliorhodopsin (HeR) is a new rhodopsin family discovered in 2018 through functional metagenomic analysis. Similar to microbial rhodopsins, HeR has an all-trans retinal chromophore, and its photoisomerization to the 13-cis form triggers a relatively slow photocycle with sequential intermediate states (K, M, and O intermediates). The O intermediate has a relatively long lifetime and is a putative active state for transferring signals or regulating enzymatic reactions. Although the first discovered HeR, 48C12, was found in bacteria and the second HeR (TaHeR) was found in archaea, their key amino acid residues and molecular architectures have been recognized to be well conserved. Nevertheless, the rise and decay kinetics of the O intermediate are faster in 48C12 than in TaHeR. Here, using a new infrared spectroscopic technique with quantum cascade lasers, we clarified that the hydrogen bond between transmembrane helices (TM) 3 and 4 is essential for the altered O kinetics (Ser112 and Asn138 in 48C12). Interconverting mutants of 48C12 and TaHeR clearly revealed that the hydrogen bond is important for regulating the dynamics of the O intermediate. Overall, our study sheds light on the importance of the hydrogen bond between TM3 and TM4 in heliorhodopsins, similar to the DC gate in channelrhodopsins.
PubMed: 38880378
DOI: 10.1016/j.jmb.2024.168666 -
Chemosphere Aug 2024This study aims the characterization of several tianeptine transformation products in ultrapure water by simulated sunlight irradiation. Tianeptine was completely...
This study aims the characterization of several tianeptine transformation products in ultrapure water by simulated sunlight irradiation. Tianeptine was completely degraded after 106 h of exposition following pseudo-first-order kinetics (half-life time = 12.0 ± 2.4 h). Furthermore, an ultra-high-performance liquid chromatography coupled with a high-resolution quadrupole time-of-flight-mass spectrometry method was developed and fully validated taking into account different method performance parameters for the quantification of tianeptine in river water up to a concentration of 400 pg L. Following a non-targeted approach based on mass data-independent acquisition, eight different transformation products not previously reported in the literature were identified and accordingly elucidated, proposing a photodegradation mechanism based on the accurate tandem mass spectrometry information acquired. Irradiation experiments were replicated for a tianeptine solution prepared in a blank river water sample, resulting in the formation of the same transformation products and similar degradation kinetics. In addition, a toxicity assessment of the photoproducts was performed by in silico method, being generally all TPs of comparable toxicity to the precursor except for TP1, and showing a similar persistence in the environment except for TP2 and TP6, while TP4 was the only TP predicted as mutagenic. The developed method was applied for the analysis of four river water samples.
Topics: Water Pollutants, Chemical; Tandem Mass Spectrometry; Chromatography, High Pressure Liquid; Photolysis; Thiazepines; Rivers; Kinetics; Sunlight
PubMed: 38849097
DOI: 10.1016/j.chemosphere.2024.142534 -
Analytical Chemistry Jun 2024Biopharmaceuticals, such as monoclonal antibodies (mAbs), need to maintain their chemical and physical stability in formulations throughout their lifecycle. It is known...
Biopharmaceuticals, such as monoclonal antibodies (mAbs), need to maintain their chemical and physical stability in formulations throughout their lifecycle. It is known that exposure of mAbs to light, particularly UV, triggers chemical and physical degradation, which can be exacerbated by trace amounts of photosensitizers in the formulation. Although routine assessments of degradation following defined UV dosages are performed, there is a fundamental lack of understanding regarding the intermediates, transient reactive species, and radicals formed during illumination, as well as their lifetimes and immediate impact post-illumination. In this study, we used light-coupled NMR spectroscopy to monitor in situ live spectral changes in sealed samples during and after UV-A illumination of different formulations of four mAbs without added photosensitizers. We observed a complex evolution of spectra, reflecting the appearance within minutes of transient radicals during illumination and persisting for minutes to tens of minutes after the light was switched off. Both mAb and excipient signals were strongly affected by illumination, with some exhibiting fast irreversible photodegradation and others exhibiting partial recovery in the dark. These effects varied depending on the mAb and the presence of excipients, such as polysorbate 80 (PS80) and methionine. Complementary ex situ high-performance size-exclusion chromatography analysis of the same formulations post-UV exposure in the chamber revealed significant loss of purity, confirming formulation-dependent degradation. Both approaches suggested the presence of degradation processes initiated by light but continuing in the dark. Further studies on photoreaction intermediates and transient reactive species may help mitigate the impact of light on biopharmaceutical degradation.
Topics: Antibodies, Monoclonal; Ultraviolet Rays; Magnetic Resonance Spectroscopy; Photolysis; Drug Compounding; Drug Stability; Light
PubMed: 38847283
DOI: 10.1021/acs.analchem.4c01164