An updated modeling framework to simulate Los Angeles air quality - Part 1: Model development, evaluation, and source apportionment.

This study describes a modeling framework, model evaluation, and source apportionment to understand the causes of Los Angeles (LA) air pollution. A few major updates are applied to the Community Multiscale Air Quality (CMAQ) model with a high spatial resolution (1 km × 1 km). The updates include dynamic traffic emissions based on real-time, on-road information and recent emission factors and secondary organic aerosol (SOA) schemes to represent volatile chemical products (VCPs).

Temperature-dependent emissions dominate aerosol and ozone formation in Los Angeles.

Despite declines in transportation emissions, urban North America and Europe still face unhealthy air pollution levels. This has challenged conventional understanding of the sources of their volatile organic compound (VOC) precursors. Using airborne flux measurements to map emissions of a wide range of VOCs, we demonstrate that biogenic terpenoid emissions contribute ~60% of emitted VOC OH reactivity, ozone, and secondary organic aerosol formation potential in summertime Los Angeles and that this contribution strongly increases with temperature.

Iodine oxoacids enhance nucleation of sulfuric acid particles in the atmosphere.

The main nucleating vapor in the atmosphere is thought to be sulfuric acid (HSO), stabilized by ammonia (NH). However, in marine and polar regions, NH is generally low, and HSO is frequently found together with iodine oxoacids [HIO, i.e.

Methane Emissions from Dairy Operations in California's San Joaquin Valley Evaluated Using Airborne Flux Measurements.

State inventories indicate that dairy operations account for nearly half of California's methane budget. Recent analyses suggest, however, that these emissions may be underestimated, complicating efforts to develop emission reduction strategies. Here, we report estimates of dairy methane emissions in the southern San Joaquin Valley (SJV) of California in June 2021 using airborne flux measurements.

Synergistic HNO-HSO-NH upper tropospheric particle formation.

New particle formation in the upper free troposphere is a major global source of cloud condensation nuclei (CCN). However, the precursor vapours that drive the process are not well understood. With experiments performed under upper tropospheric conditions in the CERN CLOUD chamber, we show that nitric acid, sulfuric acid and ammonia form particles synergistically, at rates that are orders of magnitude faster than those from any two of the three components.

Traffic, transport, and vegetation drive VOC concentrations in a major urban area in Texas.

The population of Texas has increased rapidly in the past decade. The San Antonio Field Study (SAFS) was designed to investigate ozone (O) production and precursors in this rapidly changing, sprawling metropolitan area. There are still many questions regarding the sources and chemistry of volatile organic compounds (VOCs) in urban areas like San Antonio which are affected by a complex mixture of industry, traffic, biogenic sources and transported pollutants.

Rapid hydrolysis of tertiary isoprene nitrate efficiently removes NO from the atmosphere.

The formation of a suite of isoprene-derived hydroxy nitrate (IHN) isomers during the OH-initiated oxidation of isoprene affects both the concentration and distribution of nitrogen oxide free radicals (NO). Experiments performed in an atmospheric simulation chamber suggest that the lifetime of the most abundant isomer, 1,2-IHN, is shortened significantly by a water-mediated process (leading to nitric acid formation), while the lifetime of a similar isomer, 4,3-IHN, is not. Consistent with these chamber studies, NMR kinetic experiments constrain the 1,2-IHN hydrolysis lifetime to less than 10 s in deuterium oxide (DO) at 298 K, whereas the 4,3-IHN isomer has been observed to hydrolyze much less efficiently.

Chemical nature of PM and PM in Xi'an, China: Insights into primary emissions and secondary particle formation.

In Xi'an, a city that frequently experiences serious PM pollution in northern China, 1476 PM and 1464 PM valid daily filter samples were collected at six sites from December 2014 to November 2015 and analyzed for 29 species. The annual mean PM and PM concentrations were 149.4 ± 93.

Soluble Pt-Containing Polymers Based on a 2,6-Bis(1-1,2,3-triazol-4-yl)-4-ethynylpyridine Ligand.

A soluble Pt-acetylide polymer was prepared in a supramolecular polymerization of a Pt-chloro precursor complex , which represents a self-complementary AB-type monomer. This new type of polymer combines the structural features of the common polyplatinynes and cationic Pt-acetylide complexes. Though the photophysical and electrochemical properties of the material still need to be advanced, a versatile and straightforward method for the preparation of soluble, cationic Pt-acetylide polymers with phosphorescent behavior is offered.

Halogen-bond-based cooperative ion-pair recognition by a crown-ether-embedded 5-iodo-1,2,3-triazole.

A crown-ether containing the iodo-triazole moiety for simultaneous cation-anion binding through Lewis-basic nitrogen atoms and C-II halogen-bond-donating iodine atoms was prepared. The complexation of the heteroditopic receptor was illustrated by X-ray and DFT analysis. The cooperative effect boosting the anion affinity was quantified by H/C NMR titration experiments.

ZnO Nanostructures for Dye-Sensitized Solar Cells Using the TEMPO /TEMPO Redox Mediator and Ruthenium(II) Photosensitizers with 1,2,3-Triazole-Derived Ligands.

A series of thiocyanate-free bis(tridentate) ruthenium(II) complexes incorporating 1,2,3-triazole-derived NNN-, NCN-, and CNC-coordinating ligands has been employed for sensitizing ZnO photoanodes for dye-sensitized solar cells (DSSCs). Additionally, the first use of the TEMPO /TEMPO (2,2,6,6-tetramethyl-piperidine-1-oxyl) redox mediator as a surrogate for the I /I redox couple in ZnO nanostructured DSSCs is presented. Compared with I /I -based electrolytes, shorter charge lifetimes and diffusion lengths were determined for the TEMPO /TEMPO-based electrolyte.

Preorganization in a Cleft-Type Anion Receptor Featuring Iodo-1,2,3-Triazoles As Halogen Bond Donors.

Preorganization via intramolecular hydrogen bonds was applied in a cleft-type receptor by exploiting the excellent halogen bond donor ability as well as hydrogen bond acceptor function of iodo-1,2,3-triazoles. As investigated by isothermal calorimetric titrations, the restriction of conformational freedom causes an enhanced entropic contribution resulting in a strongly increased binding affinity. This efficient way to improve the binding strength of 5-halo-1,2,3-triazoles paves the way for applications of new charge-neutral halogen bond donors in solution.

Anion receptors based on halogen bonding with halo-1,2,3-triazoliums.

A systematic series of anion receptors based on bidentate halogen bonding by halo-triazoles and -triazoliums is presented. The influence of the halogen bond donor atom, the electron-withdrawing group, and the linker group that bridges the two donor moieties is investigated. Additionally, a comparison with hydrogen bond-based analogues is provided.

Estimating the shape and size of supramolecular assemblies by variable temperature diffusion ordered spectroscopy.

Reported is characterization of the self-assembly of π-conjugated oligomers, molecules studied recently in photovoltaic devices, using variable temperature diffusion ordered spectroscopy (VT-DOSY). Iterative fitting of diffusion coefficient versus temperature data to a modified Stokes-Einstein equation, molecular modelling, and comparison to non-assembling model compounds, has allowed estimation of assembly size, shape, and molecularity.

Beyond click chemistry - supramolecular interactions of 1,2,3-triazoles.

The research on 1,2,3-triazoles has been lively and ever-growing since its stimulation by the advent of click chemistry. The attractiveness of 1H-1,2,3-triazoles and their derivatives originates from their unique combination of facile accessibility via click chemistry and truly diverse supramolecular interactions, which enabled myriads of applications in supramolecular and coordination chemistry. The nitrogen-rich triazole features a highly polarized carbon atom allowing the complexation of anions by hydrogen and halogen bonding or, in the case of the triazolium salts, via charge-assisted hydrogen and halogen bonds.

Physicochemical analysis of ruthenium(II) sensitizers of 1,2,3-triazole-derived mesoionic carbene and cyclometalating ligands.

A series of heteroleptic bis(tridentate) ruthenium(II) complexes bearing ligands featuring 1,2,3-triazolide and 1,2,3-triazolylidene units are presented. The synthesis of the C^N^N-coordinated ruthenium(II) triazolide complex is achieved by direct C-H activation, which is enabled by the use of a 1,5-disubstituted triazole. By postcomplexation alkylation, the ruthenium(II) 1,2,3-triazolide complex can be converted to the corresponding 1,2,3-triazolylidene complex.

Designing cyclometalated ruthenium(II) complexes for anodic electropolymerization.

The anodic electropolymerization of thiophene-functionalized cyclometalated ruthenium(II) complexes is shown for the first time. Oxidative decomposition reactions can be overcome by modification of the involved redox potentials through the introduction of electron-withdrawing substituents, namely nitro groups, at the cyclometalating phenyl ring. The generated functionalized ruthenium(II) complexes allow the electrochemical preparation of thin polymer films, which show a broad UV/Vis absorption as well as reversible redox switchability.

A heteroleptic bis(tridentate) ruthenium(II) platform featuring an anionic 1,2,3-triazolate-based ligand for application in the dye-sensitized solar cell.

A series of bis(tridentate) ruthenium(II) complexes featuring new anionic 1,2,3-triazolate-based tridentate ligands and 2,2':6',2''-terpyridine is presented. For a complex equipped with carboxy anchoring groups, the performance in a dye-sensitized solar cell is evaluated. The title complexes are readily synthesized and can be decorated with alkyl chains utilizing azide-alkyne cycloaddition methods, in order to improve the device stability and allow the use of alternative electrolytes.

Cyclometalated ruthenium(II) complexes featuring tridentate click-derived ligands for dye-sensitized solar cell applications.

A series of heteroleptic bis(tridentate) Ru(II) complexes featuring N^C^N-cyclometalating ligands is presented. The 1,2,3-triazole-containing tridentate ligands are readily functionalized with hydrophobic side chains by means of click chemistry and the corresponding cyclometalated Ru(II) complexes are easily synthesized. The performance of these thiocyanate-free complexes in a dye-sensitized solar cell was tested and a power conversion efficiency (PCE) of up to 4.

Cognitive impairment during 5 m water immersion.

Experimental data document that human cognition remains intact down to 6 m water immersion. This, however, is difficult to reconcile with introspective observations from experienced divers, who report cognitive impairments. We hypothesized that the discrepancy might be related to the fact that previous experiments assessed abstract cognitive skills, such as mental arithmetic, which might be less sensitive to immersion than performance-related cognitive skills, such as planning of behavior that is adequate for a given situation.

Bis(tridentate) ruthenium-terpyridine complexes featuring microsecond excited-state lifetimes.

A series of heteroleptic bis(tridentate) ruthenium(II) complexes, each bearing a substituted 2,2':6',2″-terpyridine (terpy) ligand, is characterized by room temperature microsecond excited-state lifetimes. This observation is a consequence of the strongly σ-donating and weakly π-accepting tridentate carbene ligand, 2',6'-bis(1-mesityl-3-methyl-1,2,3-triazol-4-yl-5-idene)pyridine (C^N^C), adjacent to the terpy maintaining a large separation between the ligand field and metal-to-ligand charge transfer (MLCT) states while also preserving a large (3)MLCT energy. The observed lifetimes are the highest documented lifetimes for unimolecular ruthenium(II) complexes and are four orders in magnitude higher than that associated with [Ru(terpy)(2)](2+).

Ruthenium(II) metallo-supramolecular polymers of click-derived tridentate ditopic ligands.

New ditopic 2,6-bis(1,2,3-triazol-4-yl)pyridine ligands featuring a π-conjugated spacer and clicked-on solubilizing groups were employed in the synthesis of Ru(II) metallo-supramolecular polymers that exhibit an intense metal-to-ligand charge transfer absorption in the visible light region. The coordination polymers obtained were studied in solution by means of size exclusion chromatography and analytical ultracentrifugation, revealing a comparably high molar mass and moderate rigidity. Investigations in the solid state by atomic force and transmission electron microscopy confirmed the formation of rod-like polymers.