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The Journal of Physical Chemistry. A Nov 2023Enhanced photolysis of particulate nitrate (pNO) to form photolabile species, such as gas-phase nitrous acid (HONO), has been proposed as a potential mechanism to...
Enhanced photolysis of particulate nitrate (pNO) to form photolabile species, such as gas-phase nitrous acid (HONO), has been proposed as a potential mechanism to recycle nitrogen oxides (NO) in the remote boundary layer ("renoxification"). This article presents a series of laboratory experiments aimed at investigating the parameters that control the photolysis of pNO and the efficiency of HONO production. Filters on which artificial or ambient particles had been sampled were exposed to the light of a solar simulator, and the formation of HONO was monitored under controlled laboratory conditions. The results indicate that the photolysis of pNO is enhanced, compared to the photolysis of gas-phase HNO, at low pNO levels, with the enhancement factor reducing at higher pNO levels. The presence of cations (Na) and halides (Cl) and photosensitive organic compounds (imidazole) also enhance pNO photolysis, but other organic compounds such as oxalate and succinic acid have the opposite effect. The precise role of humidity in pNO photolysis remains unclear. While the efficiency of photolysis is enhanced in deliquescent particles compared to dry particles, some of the experimental results suggest that this may not be the case for supersaturated particles. These experiments suggest that both the composition and the humidity of particles control the enhancement of particulate nitrate photolysis, potentially explaining the variability in results among previous laboratory and field studies. HONO observations in the remote marine boundary layer can be explained by a simple box-model that includes the photolysis of pNO, in line with the results presented here, although more experimental work is needed in order to derive a comprehensive parametrization of this process.
PubMed: 37879076
DOI: 10.1021/acs.jpca.3c03853 -
The Journal of Organic Chemistry Oct 2023Photolysis of 1-(2-adamantylidene)-1a,9b-dihydro-1-cyclopropa[]phenanthrene in benzene (or benzene-) at ambient temperature produces adamantylidenecarbene. The carbene...
Photolysis of 1-(2-adamantylidene)-1a,9b-dihydro-1-cyclopropa[]phenanthrene in benzene (or benzene-) at ambient temperature produces adamantylidenecarbene. The carbene undergoes dimerization to a cumulene and may also be trapped in a stereospecific fashion by - and -4-methyl-2-pentene. No products attributable to 4-homoadamantyne, resulting from ring expansion of the carbene, could be detected. Coupled cluster/density functional theory calculations place the singlet carbene ∼49 kcal/mol below the triplet and show that the former must overcome a barrier of ∼13.5 kcal/mol to rearrange into 4-homoadamantyne.
PubMed: 37768172
DOI: 10.1021/acs.joc.3c01399 -
Proceedings of the National Academy of... Jul 2023Monochloramine, dichloramine and trichloramine (NHCl, NHCl, NCl) are measured in the ambient atmosphere, in downtown Toronto in summer (median 39, 15 and 2.8 ppt) and...
Monochloramine, dichloramine and trichloramine (NHCl, NHCl, NCl) are measured in the ambient atmosphere, in downtown Toronto in summer (median 39, 15 and 2.8 ppt) and winter (median 11, 7.3 and 0.7 ppt). NCl and NHCl were also measured in summer (median 1.3 and 14 ppt) from a suburban Toronto location. Measurements at two locations demonstrate prevalence of chloramines in an urban atmosphere. At both sites, NCl exhibits a strong diel pattern with maximum values during the night, and photolytic loss with sunrise. At the downtown site, a strong positive correlation between NHCl and NHCl in the summer night indicates a common source, with daily average peak mixing ratios approaching 500 and 250 ppt, respectively. As a previously unidentified source of chlorine (Cl) atoms, we demonstrate that NCl photolysis contributes 49 to 82% of the total local summertime Cl production rate at different times during the day with an average noontime peak of 3.8 × 10 atoms/cm/s, with smaller contributions from ClNO and Cl. Photolysis of NHCl and NHCl may augment this Cl production rate. Our measurements also demonstrate a daytime enhancement of chloroacetone in both the summer and winter, demonstrating the importance of Cl photochemistry. The results suggest that chloramines are an important source of Cl atoms in urban areas, with potential impacts on the abundance of organic compounds, ozone, nitrogen oxides, and particulate matter. Future studies should explore the vertical gradients of chloramines and their contribution to Cl production throughout the boundary layer.
PubMed: 37459517
DOI: 10.1073/pnas.2220889120 -
Nature Communications Nov 2023Atomic oxygen is a key species in the mesosphere and thermosphere of Venus. It peaks in the transition region between the two dominant atmospheric circulation patterns,...
Atomic oxygen is a key species in the mesosphere and thermosphere of Venus. It peaks in the transition region between the two dominant atmospheric circulation patterns, the retrograde super-rotating zonal flow below 70 km and the subsolar to antisolar flow above 120 km altitude. However, past and current detection methods are indirect and based on measurements of other molecules in combination with photochemical models. Here, we show direct detection of atomic oxygen on the dayside as well as on the nightside of Venus by measuring its ground-state transition at 4.74 THz (63.2 µm). The atomic oxygen is concentrated at altitudes around 100 km with a maximum column density on the dayside where it is generated by photolysis of carbon dioxide and carbon monoxide. This method enables detailed investigations of the Venusian atmosphere in the region between the two atmospheric circulation patterns in support of future space missions to Venus.
PubMed: 37935682
DOI: 10.1038/s41467-023-42389-x -
ACS Omega Jul 2023N-doped carbon quantum dots (N-CQDs) derived from the L. plant were incorporated into TiO via a facile hydrothermal method. As-prepared materials were characterized and...
N-doped carbon quantum dots (N-CQDs) derived from the L. plant were incorporated into TiO via a facile hydrothermal method. As-prepared materials were characterized and used in the photocatalytic tetracycline (TC) degradation under UVA light irradiation by examining several operational parameters involving the N-CQDs amount, initial TC concentration, pH, and photocatalytic reaction time. XRD analysis revealed the conversion of the rutile phase to the anatase phase after the incorporation of N-CQDs into the TiO structure. The results revealed that the N-CQDs/TiO photocatalysts demonstrated the highest efficiency in TC degradation compared to other processes of adsorption, photolysis (UVA), and photocatalysis with TiO (TiO/UVA). Under optimized conditions, 10 mg/L TC at pH 5.15 with 0.2 g/L N-CQDs/TiO catalyst showed 97.7% photocatalytic degradation for 120 min under UVA irradiation. The formation of an S-scheme heterojunction between N-CQDs and TiO provided enhanced charge separation and strong redox capability, causing significant improvement in the photocatalytic performance of N-CQDs/TiO. Trapping experiments showed that O and h are the predominant reactive species for the TC elimination in an aqueous solution.
PubMed: 37521662
DOI: 10.1021/acsomega.3c03532 -
Scientific Reports Jul 2023In this research, we synthesized BiOI/NH-MIL125(Ti) via solvo-thermal method to investigation of oxytetracycline (OTC) degradation in photocatalytic-ozonation process....
In this research, we synthesized BiOI/NH-MIL125(Ti) via solvo-thermal method to investigation of oxytetracycline (OTC) degradation in photocatalytic-ozonation process. The results of the XRD, FESEM, EDAX, FTIR, UV-Vis, TEM, XPS, and BET analyzes indicated that the catalyst BiOI/MOF was synthesized with excellent quality. Design of experiment (DOE), ANOVA statistical analysis, interaction of parameters and predicated optimum condition was done based on CCD. The effect of catalyst dose (0.25-0.5 mg/l), pH (4-8), reaction time (30-60 min) and O concentration (20-40 mN) at 10 mg/l of OTC on PCO/O process was optimized. Based on P-value and F-value coefficients (0.0001, 450.3 respectively) the model of OTC (F-value = 2451.04) and (P-value = 0.0001) coefficients, the model of COD removal was quadratic model. Under optimum condition pH 8.0, CD = 0.34 mg/l, RT = 56 min and O concentration = 28.7 mN, 96.2 and 77.2% of OTC and COD removed, respectively. The reduction of TOC was 64.2% in optimal conditions, which is less than the reduction of COD and OTC. The kinetics of reaction followed pseudo-first-order kinetic (R = 0.99). Synergistic effect coefficient was 1.31 that indicated ozonation, presence of catalyst and photolysis had a synergistic effect on OTC removal. The stability and reusability of the catalyst in six consecutive operating steps was acceptable and 7% efficiency decreased only. Cations (Mg, and Ca), SO had no influence on performing the process, but other anions, organic scavengers, and nitrogen gas, had an inhibitory effect. Finally, the OTC degradation probably pathway includes direct and indirect oxidation that decarboxylation, hydroxylation, demethylation and were the main mechanism in OTC degradation.
PubMed: 37429926
DOI: 10.1038/s41598-023-38309-0 -
Molecules (Basel, Switzerland) Oct 2023Photochemical properties of symmetrical pyromellitic diimide containing two cymantrenyl fragments at two nitrogen atoms were studied with IR, NMR, UV-vis, ESI-MS, and...
Photochemical properties of symmetrical pyromellitic diimide containing two cymantrenyl fragments at two nitrogen atoms were studied with IR, NMR, UV-vis, ESI-MS, and cyclic voltammetry. It was found that new unstable chelates are formed during photolysis. At the same time, the CO ligand dissociates from two Mn(CO) fragments during photoexcitation, which dramatically changes the electronic and redox properties of the molecule compared to the cymantrene derivative containing one imide fragment. Photolysis leads to a color change from light yellow to green. DFT calculations confirmed the possibility of the formation of complexes due to the loss of one or two CO ligands from manganese atoms. The results obtained with variation of photolysis conditions demonstrated the hemilabile character of the Mn-O=C(imide) bond. On addition of external ligands, the color and electrochemical properties changed, which is promising for the use of this complex as a sensor for small molecules.
PubMed: 37894576
DOI: 10.3390/molecules28207098 -
Molecules (Basel, Switzerland) Feb 2024A new chloroquine-derived photoaffinity probe has been prepared by a convergent synthesis from derivative of 4,7-dichloroquinoline and N1,N1-diethyl-N4-methylpentane....
A new chloroquine-derived photoaffinity probe has been prepared by a convergent synthesis from derivative of 4,7-dichloroquinoline and N1,N1-diethyl-N4-methylpentane. The features of this probe are a unique 3-azido photolabel, the pyridine ring of the quinoline, and the presence of a secondary amine at the 4-position of the quinoline. These features, particularly the 4-amino methylation, prevent triazole formation through combination of the 3-azide and the 4-amine. This undergoes facile cleavage with exposure to a medium-pressure mercury lamp with a 254 nm excitation wavelength. Trapping of the nitrene byproduct is accomplished with its reaction with N-phenylmaleimide as its cycloazidation product. The structure of a ring-opened DBU amine has been structurally characterized.
PubMed: 38474595
DOI: 10.3390/molecules29051084 -
Molecules (Basel, Switzerland) Jan 2024In this investigation, a multifunctional visible-light TX-based photosensitizer containing a siloxane moiety (TXS) was designed with a good overall yield of 54%. The...
In this investigation, a multifunctional visible-light TX-based photosensitizer containing a siloxane moiety (TXS) was designed with a good overall yield of 54%. The addition of a siloxane moiety enabled the incorporation of a TX photosensitizer into a siloxane network by photoinduced sol-gel chemistry, thus avoiding its release. Both liquid H and solid-state Si NMR measurements undeniably confirmed the formation of photoacids resulting from the photolysis of the TXS/electron acceptor molecule (Iodonium salt), which promoted the photoinduced hydrolysis/condensation of the trimethoxysilane groups of TXS, with a high degree of condensation of its inorganic network. Notably, the laser flash photolysis, fluorescence, and electron paramagnetic resonance spin-trapping (EPR ST) experiments demonstrated that TXS could react with Iod through an electron transfer reaction through its excited states, leading to the formation of radical initiating species. Interestingly, the TXS/Iod was demonstrated to be an efficient photoinitiating system for free-radical (FRP) and cationic (CP) polymerization under LEDs@385, 405, and 455 nm. In particular, whatever the epoxy monomer mixtures used, remarkable final epoxy conversions were achieved up to 100% under air. In this latter case, we demonstrated that both the photoinduced sol-gel process (hydrolysis of trimethoxysilane groups) and the cationic photopolymerization occurred simultaneously.
PubMed: 38202842
DOI: 10.3390/molecules29010255 -
Chemistry (Weinheim An Der Bergstrasse,... Nov 2023The achievement of light-responsive behaviours is an important target for protocell engineering to allow control of fundamental protocellular processes such as...
The achievement of light-responsive behaviours is an important target for protocell engineering to allow control of fundamental protocellular processes such as communication via diffusible chemical signals, shape changes or even motility at the flick of a switch. As a step towards this ambitious goal, here we describe the synthesis of a novel poly(ethylene glycol)-based crosslinker, reactive towards nucleophiles, that effectively degrades with UV light (405 nm). We demonstrate its utility for the fabrication of the first protocell membranes capable of light-induced disassembly, for the photo-generation of patterns of protocells, and for the modulation of protocell membrane permeability. Overall, our results not only open up new avenues towards the engineering of spatially organised, communicating networks of protocells, and of micro-compartmentalised systems for information storage and release, but also have important implications for other research fields such as drug delivery and soft materials chemistry.
Topics: Artificial Cells; Polyethylene Glycols
PubMed: 37497813
DOI: 10.1002/chem.202302058