Orbital Distribution Research Articles

Molecular self-assembly of 1D linear and 2D T-shape polyiodide arrangements in two organic ammonium triiodide salts: supramolecular structures and density functional theory-based optical properties

Schematic depiction of the σ MOs in the vicinity of the HOMO of I3−. The orbital distribution of HOMO-2 and LUMO for compounds 1 and 2 computed at the TD-DFT method.

Eco-friendly synthesis and assessment of chrysin – primed zinc ferrite nanoparticles against vinyl chloride and 2-acetylaminofluorene model of hepatorenal injury in rats

Co-exposure to environmental toxicants is becoming an emerging problem globally. This study investigated the potential of chrysin-primed zinc-ferrite nanoparticles (ZnFe2O4@Chrysin) to counteract oxidative stress and inflammation in vinyl chloride (VC) and 2-acetylaminofluorene (2-AAF) induced liver and kidney toxicities in male Wistar rats. ZnFe2O4@Chrysin was identified using x-ray diffraction, thermogravimetric analysis, Fourier Transform Infrared spectroscopy, scanning and transmission electron micrographs. Molecular orbital distributions in chrysin were determined using Density Functional Theorem analyses. Forty –two rats were placed in six groups of seven animals each, and orally administered with ZnFe2O4@Chrysin (10, 20, 50 mg/kg), VC (50 mg/kg) and 2-AAF (30 mg/kg) over a period of 28 days. Liver and kidney function, lipid profile, oxidative stress, inflammation, endocrine and cancer parameters were evaluated. Treatment with ZnFe2O4@Chrysin ameliorated the VC + 2-AAF induced elevations in alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, triglyceride, urea, uric acid, and sodium and potassium levels. VC + 2-AAF also caused significant elevations in superoxide dismutase, malondialdehyde, nitric oxide, myeloperoxidase levels which were restored by ZnFe2O4@Chrysin. Elevated levels of alpha fetoprotein, C-reactive protein (CRP) and thyroid stimulating hormone in VC + 2-AAF treated rats were significantly reversed by ZnFe2O4@Chrysin. ZnFe2O4@Chrysin also restored the histoarchitecture of the kidney and liver of rats exposed to VC + 2-AAF. This study suggests that ZnFe2O4@Chrysin offered protection against VC and 2-AAF induced alterations in biochemical indices of rats via anti-inflammatory and antioxidant mechanisms.

A first principles study of the electronic structure and optical response of heterobimetallic M-dicyanoaurate-based coordination polymers (M = Mn, Co, Ni, Zn and Cd).

The electronic structure and derived optical properties of five synthesized metal-dicyanoaurate(I), (K)M[Au(CN)2], (M = Mn, Co, Ni, Zn and Cd), coordination polymers are described from a combined experimental analysis and theoretical study based on density functional theory. In this sense, the topological features that influence the electronic structure, which in turn give rise to electronic transitions associated with the band gap energy, are studied from first principles calculations (with hybrid HSE06 and GGA-PBE density functionals) and electronic spectroscopy. The impact of gold (through spin-orbit coupling) and aurophilic interactions on the electronic transitions that gives rise to optical properties is described. The calculated projected density of states and band dispersion diagrams shed light on the molecular orbital distribution and the role of a dicyanoaurate(I) molecular block as the origin of the optical properties. Infrared, Raman and ultraviolet-visible spectroscopic analyses reveal the effect that charge transfer interactions, of a metal → ligand and metal → metal nature, have on the electronic behavior within the solids through association with the polarizing power of transition metals and gold atoms.

Comparing acoustic and satellite telemetry: an analysis quantifying the space use of Chelonia mydas in Bimini, Bahamas.

Passive acoustic and Argos satellite telemetry are common methods for tracking marine species and are often used similarly to quantify space use. However, data-driven comparisons of these methods and their associated ecological inferences are limited. To address this, we compared temporal durations, spatial resolutions, financial costs and estimates of occurrence and range distributions for each tracking approach using nine juvenile green turtles (Chelonia mydas) in Bimini, Bahamas. Tracking durations were similar, although acoustic tracking provided higher spatiotemporal resolution than satellite tracking. Occurrence distributions (95%) estimated from satellite telemetry were 12 times larger than those from acoustic telemetry, while satellite range distributions (95%) were 89 times larger. While individuals generally remained within the extent of the acoustic receiver array, gaps in coverage were identified. These gaps, combined with the lower accuracy of satellite telemetry, were likely drivers for the larger satellite distributions. Costs differed between telemetry methods, with acoustic telemetry being less expensive at larger sample sizes with a previously established array. Our results suggest that acoustic and satellite telemetry may not provide similar inferences of individual space use. As such, we provide recommendations to identify telemetry methods appropriate for specific study objectives and provide discussion on the biases of each.

Theoretical Study on ORR/OER Bifunctional Catalytic Activity of Axial Functionalized Iron Polyphthalocyanine.

Designing efficient ORR/OER bifunctional electrocatalysts is very significant for reducing energy consumption and environmental protection. Hence, we studied the ORR/OER bifunctional catalytic activity of iron polyphthalocyanine (FePPc) coordinated by a series of axial ligands which has different electronegative coordination atom (FePPc-L) (L = -CN, -SH, -SCH3, -SC2H5, -I, -Br, -NH2, -Cl, -OCH3, -OH, and -F) in alkaline medium by DFT calculations. Among all FePPc-L, FePPc-CN, FePPc-SH, FePPc-SCH3, and FePPc-SC2H5 exhibit excellent ORR/OER bifunctional catalytic activities. Their ORR/OER overpotential is 0.256 V/0.234 V, 0.278 V/0.256 V, 0.280 V/0.329 V, and 0.290 V/0.316 V, respectively, which are much lower than that of the FePPc (0.483 V/0.834 V). The analysis of the electronic structure of the above catalysts shows that the electronegativity of the coordination atoms in the axial ligand is small, resulting in less distribution of dz2, dyz, and dxz orbitals near Ef, weak orbital polarization, small charge and magnetic moment of the central Fe atom, and weak adsorption strength for *OH. All these prove that the introduction of axial ligands with appropriate electronegativity coordinating atoms can adjust the adsorption of catalyst to intermediates and modify the ORR/OER bifunctional catalytic activities. This is an effective strategy for designing efficient ORR/OER bifunctional electrocatalysts.

ADSORPTION OF DIBENZOXAZEPINE GAS ON TRANSITION METAL-DOPED SILICON CARBIDE NANOTUBES: A THEORETICAL INVESTIGATION

Dibenzoxazepine (CR) molecule is highly toxic gas, therefore, the development of highly sensitive materials for their adsorption and detection is desirable. Density functional theory (DFT) calculation was performed to study the adsorption behavior of CR gas on the pristine and transition metal (TM=Sc, Ti, Y, Zr, La, and Hf) –doped silicon carbide nanotubes (SiCNT) at both Si and C sites. The most stable adsorption configurations, adsorption distances, adsorption energies, charge transfers, energy gaps, orbital distributions, and density of states are obtained to understand the impacts of CR gas on the adsorption abilities and electronic properties of the pristine and TM–doped SiCNT surfaces. The results show that the pristine SiCNT exhibits low adsorption ability to CR gas. Conversely, the SiCNT doping with TM atom at Si and C sites enhances adsorption ability to CR gas. The strong adsorption of CR gas on TM–doped SiCNT surface is due to more favorable orbital interaction as well as shorter adsorption distance and larger charge transfer than pristine SiCNT. Moreover, the results reveal that the adsorption of CR gas significant changes in the electronic properties of TM–doped SiCNT. Therefore, the doping of TM atoms on SiCNT at both Si and C sites could enhance the adsorption ability and suitable for use as sensors for detecting CR gas.

Enhancing non-radical peroxydisulfate activation by single-atom Fe-N-C catalyst through boron doping

Atomically dispersed transition metal-nitrogen-carbon (M-N-C) is regarded as one of the prospective materials to eliminate organic pollutants in water. However, manipulating the coordination sphere of the center metal to achieve the highest catalytic performance remains a challenge. Herein, a Fe-BNC catalyst with Fe atom decorated B,N-codoped hierarchical porous carbon was synthesized for peroxydisulfate (PDS) activation, which exhibits superb and highly selective degradation of model aqueous pollutants within a wide pH scope (2.63–10.36). The experiments and theoretical simulation indicate that the high activity of Fe-BNC origins from novel dual-pathway activation, involving PDS oxidation at the electron-poor B atoms for the formation of singlet oxygen (1O2) and PDS reduction over electron-rich Fe atoms for the generation of hydroxyl and sulfate radicals, where 1O2 was the primary active species. Moreover, the B atoms introduces point defects and optimizes the distribution of Fe 3d orbitals, which simultaneously facilitates PDS chemical adsorption and activation. We further loaded Fe-BNC on the widely used polyvinylidene fluoride (PVDF) microfiltration membrane and proved the stable performance for removing model pollutants when they pass through the filter, advancing the applications of M-N-C materials in actual practice.

Preparation of chlorophyll compounds and simulation of DFT optical properties assisted screening of photosensitizers from Ginkgo biloba leaves

Chlorophyll compounds (Chls) from Ginkgo biloba leaves (GBL) are non-toxic natural pigments characterized by highly conjugated molecules and special spectra, making them ideally potential photosensitizers (PSs) in photodynamics therapy (PDT). In this study, 4 Chls were isolated from Ginkgo biloba polyprenols (GBPPs) wastes by using silica gel column separation and high performance liquid chromatography (HPLC). In addition, two new chlorophyll derivatives were successfully synthesized with chlorin e6 as the primary raw material. To evaluate and identify superior chlorophyll PSs, Density Functional Theory (DFT) and Density Functional Theory (TD-DFT)were employed to decode the microscopic and spectral properties of Ginkgo biloba Chls (GBChls). The spectral absorption, optical stability and reactive oxygen species (ROS) production of GBChls were further analyzed through comparisons of their frontier molecular orbital layout, charge distribution and excitation energy properties. Our results show that about 63 % absorption in the Q band for 14 GBChls comes from the π⇢π* transition from the highest occupied orbital (HOMO) to the lowest unoccupied orbital (LUMO), indicating the favorable delocalization effect of these GBChls. In particular, those GBChls with the long chain of the phytyl group exhibited higher total electron energy and thus could significantly increase the light stability. However, the large spatial volume and hydrophobicity of these compounds with the phytyl group chain was unfavorable for cellular uptake, leading to low ROS in cells. The electronegativity of porphin macrocycles in GBChls positively correlates with the intracellular ROS production rate, meaning that the former likely promotes the energy transfer between PSs and molecular oxygen during type II photoreaction. Among the GBChls, chlorin e6 demonstrated the highest ROS yields in DMF, while purpurin 18 compounds displayed long-wavelength absorption (698 nm), strong Q-band absorption, good optical stability, and high intracellular ROS production. Our findings highlight that chlorin e6 and purpurin 18 are most potential PSs anticancer drugs and offer new research perspectives for the processing and utilization of GBL resources.

NEOMOD 2: An updated model of Near-Earth Objects from a decade of Catalina Sky Survey observations

Catalina Sky Survey (CSS) is a major survey of Near-Earth Objects (NEOs). In a recent work, we used CSS observations from 2005–2012 to develop a new population model of NEOs (NEOMOD). CSS’s G96 telescope was upgraded in 2016 and detected over 10,000 unique NEOs since then. Here we characterize the NEO detection efficiency of G96 and use G96’s NEO detections from 2013–2022 to update NEOMOD. This resolves previous model inconsistencies related to the population of large NEOs. We estimate there are 936±29 NEOs with absolute magnitude H<17.75 (diameter D>1 km for the reference albedo pV=0.14) and semimajor axis a<4.2 au. The slope of the NEO size distribution for H=25–28 is found to be relatively shallow (cumulative index ≃2.6) and the number of H<28 NEOs (D>9 m for pV=0.14) is determined to be (1.20±0.04)×107, about 3 times lower than in Harris & Chodas (2021). Small NEOs have a different orbital distribution and higher impact probabilities than large NEOs. We estimate 0.034±0.002 impacts of H<28 NEOs on the Earth per year, which is near the low end of the impact flux range inferred from atmospheric bolide observations. Relative to a model where all NEOs are delivered directly from the main belt, the population of small NEOs detected by G96 shows an excess of low-eccentricity orbits with a≃1–1.6 au that appears to increase with H (≃30% excess for H=28). We suggest that the population of very small NEOs is boosted by tidal disruption of large NEOs during close encounters to the terrestrial planets. When the effect of tidal disruption is (approximately) accounted for in the model, we estimate 0.06±0.01 impacts of H<28 NEOs on the Earth per year, which is more in line with the bolide data. The impact probability of a H<22 (D>140 m for pV=0.14) object on the Earth in this millennium is estimated to be ≃4.5%.

The California Legacy Survey. IV. Lonely, Poor, and Eccentric: A Comparison between Solitary and Neighborly Gas Giants

We compare systems with single giant planets to systems with multiple giant planets using a catalog of planets from a high-precision radial velocity survey of FGKM stars. Our comparison focuses on orbital properties, planet masses, and host-star properties. We use hierarchical methods to model the orbital eccentricity distributions of giant singles and giant multiples, and find that the distributions are distinct. The multiple giant planets typically have moderate eccentricities and their eccentricity distribution extends to e = 0.47 (90th percentile), while the single giant planets have a pileup of nearly circular orbits and a long tail that extends to e = 0.77. We determine that the stellar hosts of multiple giants are distinctly more metal rich than the hosts of solitary giants, with respective mean metallicities of 0.228 ± 0.027 versus 0.129 ± 0.019 dex. We measure the distinct occurrence distributions of single and multiple giants with respect to orbital separation, and find that single gas giants have a ∼2.3σ significant hot Jupiter (a < 0.06) pileup not seen among multigiant systems. We find that the median mass () of giants in multiples is nearly double that of single giants (1.71 M J versus 0.92 M J). We find that giant planets in the same system have correlated masses, analogous to the “peas in a pod” effect seen among less-massive planets.

TOI-4641b: an aligned warm Jupiter orbiting a bright (V=7.5) rapidly rotating F-star

ABSTRACT We report the discovery of TOI-4641b, a warm Jupiter transiting a rapidly rotating F-type star with a stellar effective temperature of 6560 K. The planet has a radius of 0.73 RJup, a mass smaller than 3.87 MJup(3σ), and a period of 22.09 d. It is orbiting a bright star (V=7.5 mag) on a circular orbit with a radius and mass of 1.73 R⊙ and 1.41 M⊙. Follow-up ground-based photometry was obtained using the Tierras Observatory. Two transits were also observed with the Tillinghast Reflector Echelle Spectrograph, revealing the star to have a low projected spin-orbit angle (λ=$1.41^{+0.76}_{-0.76}$°). Such obliquity measurements for stars with warm Jupiters are relatively few, and may shed light on the formation of warm Jupiters. Among the known planets orbiting hot and rapidly rotating stars, TOI-4641b is one of the longest period planets to be thoroughly characterized. Unlike hot Jupiters around hot stars which are more often misaligned, the warm Jupiter TOI-4641b is found in a well-aligned orbit. Future exploration of this parameter space can add one more dimension to the star–planet orbital obliquity distribution that has been well sampled for hot Jupiters.

Enhanced Hydrogen Storage Capacity in Two-Dimensional Fullerene Networks.

In contrast to isolated C60 molecular dispersion in solvents, the monolayer C60 networks synthesized by Hou et al. (Nature 2022, 606, 507-510) feature compact nanocages, serving as natural containers for hydrogen storage. The anisotropic lattice and intrinsic local strains induce delocalization of conjugated π orbitals within C60, enabling hydrogen chemisorption without an additional chemical modification. Through first-principles calculations and molecular dynamics simulations, we reveal the correspondence between chemisorption sites and orbital distributions, determining the orientation of polyhedrons formed by physiosorbed hydrogen molecules. The combination of chemisorption and physisorption processes significantly enhances hydrogen storage capacity in monolayer C60 networks while maintaining the thermodynamic stability of the nanocage structures. Numerical results indicate a maximum internal hydrogen pressure exceeding 116 GPa at room temperature and atmospheric pressure. These findings suggest that monolayer C60 networks are promising solid-state candidates for highly efficient hydrogen storage.

Simulation of In-Space Fragmentation Events

In the next years, the space debris population is expected to progressively grow due to in-space collisions and break-up events; in addition, anti-satellite tests can further affect the debris environment by generating large clouds of fragments. The simulation of these events allows identifying the main parameters affecting fragmentation and obtaining statistically accurate populations of generated debris, both above and below detection thresholds for ground-based observatories. Such information can be employed to improve current fragmentation models and to reproduce historical events to better understand their influence on the non-detectable space debris population. In addition, numerical simulation can also be used as input to identify the most critical objects to be removed to reduce the risk of irreversible orbit pollution. In this paper, the simulation of historical in-orbit fragmentation events is discussed and the generated debris populations are presented. The presented case-studies include the COSMOS-IRIDIUM collision, the COSMOS 1408 anti-satellite test, the 2022-151B CZ-6A in-orbit break-up, and a potential collision of ENVISAT with a spent rocket stage; for these events, results are presented in terms of cumulative fragments distributions and debris orbital distributions.

Main belt asteroids taxonomical information from dark energy survey data

ABSTRACT While proper orbital elements are currently available for more than 1 million asteroids, taxonomical information is still lagging behind. Surveys like SDSS-MOC4 provided preliminary information for more than 100 000 objects, but many asteroids still lack even a basic taxonomy. In this study, we use Dark Energy Survey (DES) data to provide new information on asteroid physical properties. By cross-correlating the new DES data base with other data bases, we investigate how asteroid taxonomy is reflected in DES data. While the resolution of DES data is not sufficient to distinguish between different asteroid taxonomies within the complexes, except for V-type objects, it can provide information on whether an asteroid belongs to the C- or S-complex. Here, machine learning methods optimized through the use of genetic algorithms were used to predict the labels of more than 68 000 asteroids with no prior taxonomic information. Using a high-quality, limited set of asteroids with data on gri slopes and i − z colours, we detected 409 new possible V-type asteroids. Their orbital distribution is highly consistent with that of other known V-type objects.

Crystal growth, HOMO-LUMO engineering and charge-transfer emission of TCNB-based donor-acceptor cocrystals

Using carbazole (CARB), dibenzothiophene (DBZP) and dibenzofuran (DBZF) as electron donors, 1,2,4,5-tetracyanobenzene (TCNB) as electron acceptor, three typical types of luminescent organic cocrystals were synthesized by a simple supramolecular assembly strategy. The cocrystals exhibit interesting optical properties for its charge transfer (CT) interactions. Meanwhile, a series of three-component (CARB)x (DBZP)1-x (TCNB) crystalline microtubes comprising organic CT interactions have been prepared by the self-assembly with poor solvent co-precipitating method. DFT calculations were used to predict the CT interactions and the binding patterns of donor and acceptor, which suggest that the CT interactions can largely influence the energy level and orbital distributions. Moreover, the SXRD analyses verified the cocrystals are constructed by π-π stacking with a face-to-face model. The solid-state cocrystals and microtubes were well characterized by PXRD, UV absorption spectra, emission spectra, fluorescence lifetime and quantum yield analyses. The obvious red-shift in UV–vis absorption spectra and emission spectra with respect to the free monomer indicate the formation of CT interactions. The emission colors of the mixed microtubes can be tailored from green to orange as well as associated photophysical properties with the increasing of dopant concentrations. Therefore, by the combination of experimental and theoretical studies on the cocrystals and microtubes, this work not only reports the new types of crystalline micro-nano materials, but also provides an in-depth understanding of the relationship between structure and fluorescence effect.

Impact of tidal environment on galaxy clustering in GAMA

ABSTRACT We constrain models of the galaxy distribution in the cosmic web using data from the Galaxy and Mass Assembly (GAMA) survey. We model the redshift-space behaviour of the 2-point correlation function (2pcf) and the recently proposed Voronoi volume function (VVF) – which includes information beyond two-point statistics. We extend the standard halo model using extra satellite degrees of freedom and two assembly bias parameters: αcen and αsat, which correlate the occupation numbers of central and satellite galaxies with their host halo’s tidal environment, respectively. We measure $\alpha _{\rm sat}=1.44^{+0.25}_{-0.43}$ and $\alpha _{\rm cen}=-0.79^{+0.29}_{-0.11}$ using a combination of 2pcf and VVF measurements, representing a detection of assembly bias at the 3.3σ (2.4σ) significance level for satellite (central) galaxies. This result remains robust to possible anisotropies in the halocentric distribution of satellites as well as technicalities of estimating the data covariance. We show that the growth rate (fσ8) deduced using models with assembly bias is about 7 per cent (i.e. 1.5σ) lower than if assembly bias is ignored. When projected on to the Ωm–σ8 plane, the model constraints without assembly bias overlap with Planck expectations, while allowing assembly bias introduces significant tension with Planck, preferring either a lower Ωm or a lower σ8. Finally, we find that the all-galaxy weak-lensing signal is unaffected by assembly bias, but the central and satellite sub-populations individually show significantly different signals in the presence of assembly bias. Our results illustrate the importance of accurately modelling galaxy formation for cosmological inference from future surveys.

Experimental and theoretical confirmation of CeFeCu trimetal oxide/Bi2O3 S-scheme heterojunction for boosted photocatalytic degradation of sulfamethoxazole and toxicity evaluation

Photocatalytic degradation of pharmaceutical pollutants in water or wastewater is becoming a hot topic for environmental clean-up. Herein, a novel CeFeCu trimetal oxide (CFC TMO)/Bi2O3 (CFCB) photocatalysts were prepared through precursor mixing, ultrasonication, and calcination methods and used for photocatalytic degradation of sulfamethoxazole (SMZ). The pseudo-first order kinetic rate of CFCB-2 catalyst on degradation of SMZ reached 0.0577 min−1 which is 4.93 and 10.02 times higher than of α-Bi2O3 and CFC TMO under visible light illumination. This was proved by the strong interaction between the pristine materials as confirmed by XPS and density functional theory (DFT) calculations. DFT calculations indicated that having more orbital distribution could make it easier to capture more electrons and produce more radicals through electron transfer. Meanwhile SMZ by-products showed no sign of cytotoxicity towards human embryonic kidney cell line (HEK 293) and human intestinal epithelial cell line (CACO-2). The findings of the scavenger experiments and ESR measurements proved that •OH and •O2− radicals played superior role in decomposition of SMZ. Furthermore, the S-scheme charge carrier transfer and degradation pathway of SMZ are proposed and analysed. This study paves ways into promising strategy for the construction of α-Bi2O3 based novel S-scheme heterojunction for environmental decontamination and can be extended to other applications such as Fenton-like reactions and persulfate activation.

Ibuprofen adsorption and detection of pristine, Fe–, Ni–, and Pt–doped boron nitride nanotubes: A DFT investigation

The main challenge has been focused on ibuprofen drug detection and adsorption of boron nitride nanotube (BNNT) doping with transition metal (TM = Fe, Ni, and Pt) atoms using the density functional theory calculation in gas and water phases. The geometrical structures, adsorption energies, solvation energies, and electronic properties were examined. The optimized geometries show that the ibuprofen molecule oriented itself at different bond distances and angles with respect to BNNT surface. The calculated results display exothermic adsorption processes for all ibuprofen/BNNT and ibuprofen/TM–doped BNNT complexes. Ibuprofen molecule can absorb on the Fe–, Ni–, and Pt–doped BNNTs via a stronger interaction than those of pristine BNNT in both gas and water phases in which the Fe doping on N site of BNNT shows the strongest interaction with ibuprofen molecule. The H (head) site of ibuprofen molecule to BNNT surface shows stronger interaction than M (middle) and T (tail) sites. The short of adsorption distance and the large of charge transfer correspond to the high adsorption strength of TM–doped BNNTs toward ibuprofen molecule. Charge analysis confirms the partial charge transfer occurring from the ibuprofen molecule to the BNNTs. The solvation energies in water solution reveal that the ibuprofen molecule adsorbed on TM–doped BNNTs is more soluble than pristine BNNT. The work functions of BNNTs are reduced by ibuprofen adsorption. A short recovery times and suitable desorption temperatures are observed for the ibuprofen desorption on pristine BNNT and TM–doped BNNT surfaces. After ibuprofen adsorption, the energy levels and energy gaps of Fe–, Ni–, and Pt–doped BNNTs are changed in which Ni doping on B atom of BNNT displays the largest change. The quantum molecular characteristics of BNNT will be changed after ibuprofen adsorption. The orbital distributions are occurred around the ibuprofen molecule and doping site. The alteration in the density of states for TM–doped BNNT is considerably more pronounced compared to the pristine BNNT. Drawing from the achieved outcomes, it can be inferred that when employed for the delivery of ibuprofen in biological media, Fe–, Ni–, and Pt–doped BNNTs exhibits the greater suitability for the adsorption and detection of the ibuprofen molecule compared to pristine BNNT.

Bridging the spatial gaps of the Ammonia Monitoring Network using satellite ammonia measurements

Abstract. Ammonia (NH3) is a key precursor to fine particulate matter (PM2.5) and a primary form of reactive nitrogen. The limited number of NH3 observations hinders the further understanding of its impacts on air quality, climate, and biodiversity. Currently, NH3 ground monitoring networks are few and sparse across most of the globe, and even in the most established networks, large spatial gaps exist between sites and only a few sites have records that span longer than a decade. Satellite NH3 observations can be used to discern trends and fill spatial gaps in networks, but many factors influence the syntheses of the vastly different spatiotemporal scales between surface network and satellite measurements. To this end, we intercompared surface NH3 data from the Ammonia Monitoring Network (AMoN) and satellite NH3 total columns from the Infrared Atmospheric Sounding Interferometer (IASI) in the contiguous United States (CONUS) and then performed trend analyses using both datasets. We explored the sensitivity of correlations between the two datasets to factors such as satellite data availability and distribution over the surface measurement period, as well as agreement within selected spatial and temporal windows. Given the short lifetime of atmospheric ammonia and consequently sharp gradients, smaller spatial windows show better agreement than larger ones except in areas of relatively uniform, low concentrations where large windows and more satellite measurements improve the signal-to-noise ratio. A critical factor in the comparison is having satellite measurements across most of the measurement period of the monitoring site. When IASI data are available for at least 80 % of the days of AMoN's 2-week sampling period within a 25 km spatial window of a given site, IASI NH3 column concentrations and the AMoN NH3 surface concentrations have a correlation of 0.74, demonstrating the feasibility of using satellite NH3 columns to bridge the spatial gaps existing in the surface network NH3 concentrations. Both IASI and AMoN show increasing NH3 concentrations across the CONUS (median: 6.8 % yr−1 versus 6.7 % yr−1) in the last decade (2008–2018), suggesting the NH3 will become a greater contributor to nitrogen deposition. NH3 trends at AMoN sites are correlated with IASI NH3 trends (r = 0.66) and show similar spatial patterns, with the highest increases in the Midwest and eastern US. In spring and summer, increases in NH3 were larger than 10 % yr−1 in the eastern US and Midwest (cropland dominated) and the western US (pastureland dominated), respectively. NH3 hotspots are defined as regions where the IASI NH3 column is larger than the 95th percentile of the 11-year CONUS map (6.7 × 1015 molec.cm-2), they also experience increasing concentrations over time, with a median of NH3 trend of 4.7 % yr−1. IASI data show large NH3 increases in urban areas (8.1 % yr−1), including 8 of the top 10 most populous regions in the CONUS, where AMoN sites are sparse. A comparison between IASI NH3 concentration trends and state-level NH3 emission trends is then performed to reveal that positive correlations exist in states with strong agricultural NH3 emissions, while there are negative correlations in states with low NH3 emissions and large NOx emissions, suggesting the different roles of emission and partitioning in NH3 increases. The increases in NH3 could have detrimental effects on nearby eco-sensitive regions through nitrogen deposition and on aerosol chemistry in the densely populated urban areas, and therefore they should be carefully monitored and studied.

Improved aggregation-induced emission behavior in D-π-A architectures by modifying the donor units

With the development of aggregation-induced emission (AIE) in optoelectronic devices, stimulus-responsive sensors, optical storage and bioimaging, the design and synthesis of efficient AIE luminogens remains a challenge. Herein, a series of asymmetric pyrene derivatives were prepared by stepwise functionalization at the 1-, 3-positions using traditional reactions. The experimental results show that a promising white-light emitting material (Commission Internationale de L'Eclairage (CIE): x = 0.32, y = 0.31), namely TPxzPy, which has completely separated the highest occupied molecular orbital (HOMOs) and lowest unoccupied molecular orbital (LUMOs) distribution, was produced. Moreover, a new strategy was established to construct pyrene-based AIE luminogens along the short axis. All compounds exhibited higher emission efficiency in the solid or aggregated state versus in solution, especially for TTPaPy with a competitive photoluminescence quantum yield as high as 76.2 %. The present work provides a feasible strategy to construct pyrene-based AIE materials for optoelectronic devices.