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Ship emissions are a significant source of air pollution, and the primary policy to control is fuel oil quality improvement. However, the impact of this policy on particle size distribution and composition characteristics remains unclear. Measurements were conducted on nine different vessels (ocean-going vessels, coastal cargo ships, and inland cargo ships) to determine the impact of fuel upgrading (S< 0.1% m/m marine gas oil (MGO) vs S< 0.5% m/m heavy fuel oil (HFO)) on elemental carbon (EC) and polycyclic aromatic hydrocarbons (PAHs) emitted by ships. (1) Fuel improvement significantly reduced EC and PAH emission, by 31 ± 25 and 45 ± 38%, respectively. However, particle size distributions showed a trend toward finer particles, with the peak size decreasing from DP= 0.38–0.60 μm (HFO) to DP= 0.15–0.25 μm (MGO), and the emission factor of DP< 100 nm increased. (2) Changes in emission characteristics led to an increase in the toxicity of ultrafine particulate matter. (3) Ship types and engine conditions affected the EC and PAH particle size distributions. Inland ships have a more concentrated particle size distribution. Higher loads result in higher emissions. (4) The composition and engine conditions of fuel oils jointly affected pollutant formation mechanisms. MGO and HFO exhibited opposite EC emissions when emitting the same level of PAHs.

The limited characterization and detection capacity of unknown compounds hinder our understanding of the molecular composition of toxic compounds in PM2.5. The present study applied Fourier transform ion cyclotron resonance mass spectrometry coupled with negative and positive electrospray ionization sources (ESI–/ESI+FT-ICR-MS) to probe the molecular characteristics and dynamic formation processes of the effective proinflammatory components in organic aerosols (OAs) of PM2.5in Guangzhou for one year. We detected abundant proinflammatory molecules in OAs, mainly classified as CHON compounds (compounds composed of C, H, O, and N atoms) in elemental and nitroaromatic compounds (NACs) in structures. From the perspective of the formation process, we discovered that these proinflammatory molecules, especially toxic NACs, were largely driven by secondary nitrate formation and biomass burning (in emission source), as well as SO2(in atmospheric evolution). In addition, our results indicated that the secondary processes had replaced the primary emission as the main contributing source of the toxic proinflammatory compounds in OAs. This study highlights the importance of community measures to control the production of nitroaromatic compounds derived from secondary nitrate formation and biomass burning in urban areas.

Decades of research have established the toxicity of soot particles resulting from incomplete combustion. However, the unique chemical compounds responsible for adverse health effects have remained uncertain. This study utilized mass spectrometry to analyze the chemical composition of extracted soot organics at three oxidation states, aiming to establish quantitative relationships between potentially toxic chemicals and their impact on human alveolar basal epithelial cells (A549) through metabolomics-based evaluations. Targeted analysis using MS/MS indicated that particles with a medium oxidation state contained the highest total abundance of compounds, particularly oxygen-containing polycyclic aromatic hydrocarbons (OPAHs) composed of fused benzene rings and unsaturated carbonyls, which may cause oxidative stress, characterized by the upregulation of three specific metabolites. Further investigation focused on three specific OPAH standards: 1,4-naphthoquinone, 9-fluorenone, and anthranone. Pathway analysis indicated that exposure to these compounds affected transcriptional functions, the tricarboxylic acid cycle, cell proliferation, and the oxidative stress response. Biodiesel combustion emissions had higher concentrations of PAHs, OPAHs, and nitrogen-containing PAHs (NPAHs) compared with other fuels. Quinones and 9,10-anthraquinone were identified as the dominant compounds within the OPAH category. This knowledge enhances our understanding of the compounds contributing to adverse health effects observed in epidemiological studies and highlights the role of aerosol composition in toxicity.

Nitrogen-containing organic compounds (NOCs), a type of important reactive-nitrogen species, are abundant in organic aerosols in haze events observed in Northern China. However, due to the complex nature of NOCs, the sources, formation, and influencing factors are still ambiguous. Here, the molecular composition of organic matters (OMs) in hourly PM2.5samples collected during a haze event in Northern China was characterized using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). We found that CHON compounds (formulas containing C, H, O, and N atoms) dominated the OM fractions during the haze and showed high chemodiversity and transformability. Relying on the newly developed revised-workflow and oxidation-hydrolyzation knowledge for CHON compounds, 64% of the major aromatic CHON compounds (>80%) could be derived from the oxidization or hydrolyzation processes. Results from FT-ICR MS data analysis further showed that the aerosol liquid water (ALW)-involved aqueous-phase reactions are important for the molecular distribution of aromatic-CHON compounds besides the coal combustion, and the ALW-involved aromatic-CHON compound formation during daytime and nighttime was different. Our results improve the understanding of molecular composition, sources, and potential formation of CHON compounds, which can help to advance the understanding for the formation, evolution, and control of haze.

The roles of organosulfur compounds (OSCs), an important component in organic matter, in brown carbon (BrC) aerosol absorption is often overlooked. Here, the molecular composition of OSCs and its associations with methanol‐soluble BrC (MS‐BrC) absorption during a haze event in North China were revealed using a Fourier transform ion cyclotron resonance mass spectrometry analysis. By combining aggregated boosted tree model and partial least squares regression estimation, our results suggested that OSCs were mainly composed of potential aromatic structures, and the MS‐BrC absorption was closely related to OSCs. Specifically, OSCs contribute a notable 26% of the total potential BrC molecular number and an upper limit of 10.4% of total MS‐BrC absorption. Furthermore, we found that OSCs were mainly influenced by coal combustion, and the potential desulfurization reactions showed associations with the variations of MS‐BrC absorption. Since the residential coal combustion (an important primary source of OSs) was the major energy in North China, our research underscores the potential of aromatic OSCs as tracers for assessing the impact of fossil fuel combustion on BrC and highlights the important atmospheric influences of OSCs (e.g., light absorption and health), which need more works to uncover the origins, fates, and environmental effects of OSCs. Organosulfur compounds (OSCs) constitute a significant component of atmospheric organic matter, with their sources, formation mechanisms, and environmental impacts having been extensively studied. Nevertheless, the relationship between OSCs and brown carbon (BrC) absorption in environmental samples remains largely unexplored to date. Notably, OSCs were found abundant in fossil fuel combustion emissions, particularly for residential coal combustions, which are a widely used energy supply in North China. Here, we collected hourly PM2.5samples during a haze event in North China and characterized the molecular composition of OSCs using high‐resolution Fourier‐transform ion cyclotron resonance mass spectrometry (FT‐ICR MS). Through statistical analyses, including the aggregated boosted tree (ABT) model and partial least squares regression (PLSR), we found that BrC absorption during the haze event was influenced by OSCs emitted from coal combustions. Furthermore, the secondary transformation of OSCs may be associated with changes in MS‐BrC light‐absorbing capacity. Our findings underscore the crucial role of OSCs to BrC during winter haze in North China particularly in haze events dominated by coal combustion. Findings from this study is of great significance for understanding the environmental effects of OSCs and provides further insights into the source and atmospheric transformations of atmospheric BrC. Sulfur contents affected the BrC absorption, and OSCs contributed ∼20% of the total identified chromophores in the haze eventCoal combustion emission and its secondary process are the main sources of OSCs with aromatic OSCs dominated the molecular compositionThe transformation of OSCs may potentially impact the changes in BrC light‐absorption capacity Sulfur contents affected the BrC absorption, and OSCs contributed ∼20% of the total identified chromophores in the haze event Coal combustion emission and its secondary process are the main sources of OSCs with aromatic OSCs dominated the molecular composition The transformation of OSCs may potentially impact the changes in BrC light‐absorption capacity

The optical properties of secondary brown carbon (BrC) aerosols are poorly understood, hampering quantitative assessments of their impact. We propose a new method for estimating secondary source of BrC using excitation‐emission matrix (EEM) fluorescence spectroscopy, combined with parallel factor analysis (PARAFAC) and partial least squares regression (PLSR). Experiments were conducted on a collection of PM2.5samples from urban areas in five Chinese cities during winter and summer. The humic‐like component with long‐emission wavelengths (L‐HULIS) was identified as a secondary source tracer of BrC. This was confirmed by correlating PARAFAC components with secondary organic aerosol tracers and molecular oxidation indices obtained from Fourier transform ion cyclotron resonance mass spectrometry analysis. Using L‐HULIS as a secondary tracer of BrC, it was determined that the contribution of secondary sources to water‐soluble BrC (WS‐BrC) in source emission samples is significantly smaller than in PM2.5from five Chinese cities, supporting our method. In the five cities, secondary source derived via L‐HULIS contributes a dominant potion (80% ± 3.5%) of WS‐BrC at 365 nm during the summer, which is approximately twice as high as during the winter (45% ± 4.9%). Radiocarbon isotope (14C) analysis provides additional constraints to the sources of L‐HULIS‐derived secondary WS‐BrC in urban PM2.5, suggesting that aged biomass burning is the dominant contributor to secondary WS‐BrC in winter, and biogenic emission is dominant during summer. This study is the first report on identification of secondary sources of BrC using the fluorescence technique. It demonstrates the potential of this method in characterizing non‐fossil source secondary BrC in the atmosphere. Brown carbon (BrC) originates from primary combustion emissions and secondary formation, with large source‐dependent uncertainties of radiative forcing. Direct measurements to separate the primary and secondary BrC are challenging due to the chemical complexity. Recent online studies have shown that excitation‐emission matrix fluorescence spectroscopy coupled with parallel factor (PARAFAC) analysis identified some fluorescent components that may be linked to secondary sources. However, there is a knowledge gap on whether PARAFAC components correlate closely with atmospheric secondary chemical components, particularly biogenic and anthropogenic secondary organic aerosol, as their precursors can also form secondary BrC chromophores. We established the correlations between PARAFAC components and secondary organic aerosol tracers and compound oxidations to identify the long‐emission‐wavelength humic‐like component as a secondary source tracer of BrC. Then, we estimated non‐fossil source secondary BrC in urban aerosols during the winter and summer. Our studies provide references for quantifying secondary sources of BrC in the atmosphere. A fluorescence‐based method was developed to investigate secondary sources of water‐soluble brown carbon in five cities in ChinaThe contribution of secondary sources to water‐soluble brown carbon in the summer is approximately twice as high as during the winterThis secondary water‐soluble brown carbon was more associated with aging biomass burning in winter and biogenic emissions in summer A fluorescence‐based method was developed to investigate secondary sources of water‐soluble brown carbon in five cities in China The contribution of secondary sources to water‐soluble brown carbon in the summer is approximately twice as high as during the winter This secondary water‐soluble brown carbon was more associated with aging biomass burning in winter and biogenic emissions in summer

To quantify the volatility of organic aerosols (OA), a comprehensive campaign was conducted in the Chinese megacity. Volatility distributions of OA and particle‐phase organic nitrate (pON) were estimated based on five methods: (a) empirical method and (b) kinetic model based on the measurement of a thermodenuder (TD) coupled with an aerosol mass spectrometer; (c) Formula‐based SIMPOL model‐driven method; (d) Element‐based estimations using molecular formula measurements of OA; and (e) gas/particle partitioning. Our results demonstrate that the ambient OA volatility distribution shows good agreement between the two heating methods and the formula‐based method when assuming ambient OA was mainly composed of organic nitrate (pON), organic sulfate and acid groups using the SIMPOL model. However, the element‐based method tends to overestimate the volatility of OA compared to the above three methods, suggesting large uncertainties in the parameterizations or in the representativeness of the molecular measurements that need further refinement. The volatility of ambient OA is generally lower than that of the laboratory‐derived secondary OA, emphasizing the impact of aging. A large fraction at the higher and lower volatility ranges (approximately log C*≤ −9 and ≥2 μg m−3) was found for pON, implying the importance of both extremely low volatile and semi‐volatile species. Overall, this study evaluates different methods for volatility estimation and gives new insight into the volatility of OA and pON in urban areas. Volatility, which controls the gas/particle partitioning of organic compounds, is one of most the important physiochemistry properties of organic aerosols (OA). Multiple methods have been used to estimate OA volatility, whereas the accuracy of each method is still unclear. The purpose of this study is to verify the volatility of ambient OA and its key component (i.e., particulate organic nitrate, pON) in urban areas by comparing the estimated results using different methods. With the help of state‐of‐art mass spectrometers, the estimation methods, including two heating methods, one formula‐based method, one element‐based method, and one gas/particle partitioning method, were achieved. In general, we found the heating methods show good agreement with the formula‐based method with a reasonable assumption of functional groups contained in OA and pON. In general, we observed a large faction of extremely low volatile compounds exist in OA (30%–40%), and both extremely low volatile and semi‐volatile species exist in pON, suggesting the complex evolution of atmospheric particles. The results provide a better understanding of the volatility of OA and pON in urban areas and benefit accurate volatility estimation that facilitates the model simulations of OA. The volatility of ambient organic aerosols (OA) and organic nitrate (pON) estimated from five methods were systematically comparedThe OA volatility from SIMPOL‐driven model under organic sulfate, pON and acid assumption are consistent with those from heating methodThe volatility distribution of pON indicates both extremely low volatility compounds as oligomers and semi‐volatile species exist in pON The volatility of ambient organic aerosols (OA) and organic nitrate (pON) estimated from five methods were systematically compared The OA volatility from SIMPOL‐driven model under organic sulfate, pON and acid assumption are consistent with those from heating method The volatility distribution of pON indicates both extremely low volatility compounds as oligomers and semi‐volatile species exist in pON

Humic‐like substances (HULIS) are significant contributor to the light absorption of water‐soluble brown carbon (WSBrC), which contains certain strong light‐absorbing chemical components that are not well understood, impeding the assessment of WSBrC's climate impact. China as the hotspot regions with high loading of WSBrC characterized by high light‐absorbing capacity, here, we investigated the sources and atmospheric processes (δ13C–Δ14C), molecular composition (Fourier transform ion cyclotron resonance mass spectrometry), and light absorption properties (UV spectrophotometry) of HULIS in PM2.5from 10 Chinese cities. HULIS‐C was major contributor to the light absorption coefficient (70.5 ± 6.6%) of WSBrC at 365 nm, which was more enriched with fossil sources (48.0 ± 9.0% vs. 30.3 ± 13.9%) but depleted in 13C (δ13C: −25.6 ± 0.9‰ vs. −22.4 ± 1.0‰) relative to non‐HULIS‐C. This suggests that the fossil components in HULIS are more recalcitrant to oxidative aging and exhibit higher light‐absorbing capacity, while the non‐fossil organic carbon is more likely to be oxidatively bleached into small, colorless, and highly polar molecules (i.e., non‐HULIS). Aromatic components are the major strong light‐absorbing fossil components in HULIS, dominantly originating from coal combustion (>77%). Non‐negative matrix factorization model showed that aromatic molecules from coal combustion have higher molecular weight and lower oxidation levels than biomass burning, potentially making them to be photo‐recalcitrant compounds. Our finding that coal combustion‐derived BrC maybe more persistent in the atmosphere and has greater long‐term impact on climate than BrC derived from biomass burning is an important consideration in climate models and mitigation policies. Both the loading and light‐absorbing capacity of water‐soluble brown carbon (WSBrC) are high in China, but little is known about sources and atmospheric processes of strong light‐absorbing components in WSBrC. Humic‐like substances (HULIS) account for a significant fraction of light absorption by WSBrC, which may contain strong light‐absorbing components. Through dual carbon isotopic analysis, we discovered that HULIS‐C from 10 Chinese cities had relatively higher fossil sources contribution but lower δ13C values compared to non‐HULIS‐C. This indicates that the fossil components in HULIS not only possess a higher light‐absorbing capacity but are also more resistant to oxidative aging than non‐fossil components. The higher light‐absorbing capacity and resilience of fossil components can be attributed to the enrichment of aromatic compounds derived from coal combustion. Using the non‐negative matrix factorization model, we found that coal combustion tends to generate aromatic compounds with higher molecular weight and lower oxidation‐to‐carbon (O/C: 0.31 ± 0.03 vs. 0.50 ± 0.07) ratios than biomass burning. This characteristic may contribute to the recalcitrant property of coal combustion‐derived HULIS. Our findings highlight that coal combustion‐derived BrC may persists longer in the atmosphere and has a greater long‐term impact on climate than that derived from biomass burning. The aromatic components with strong light‐absorbing capacity in HULIS mainly originated from coal combustion, enhancing light‐absorbing capacity of HULIS‐C and making it more recalcitrant to oxidative aging.

Monosaccharides are important tracers of pollution aerosol from biomass burning. Air sampling of monosaccharides is often conducted using active samplers. However, applicability of sampling monosaccharides using polyurethane foam passive air samplers (PUF–PASs) has not been investigated, since passive air samplers are often applied to monitor semivolatile organic contaminants in large scale and remote area. Our study successfully collected atmospheric monosaccharides using PUF–PASs, providing a valuable tool for monosaccharides sampling. PUF–PAS sampling rates for individual monosaccharides were calibrated using an active sampler for 92 days, and were 1.1, 1.5, and 1.1 m3/d for levoglucosan, mannosan, and galactosan, respectively. Degradation of monosaccharides in PUF–PAS was demonstrated to be negligible by spike test of 13C-labeled levoglucosan. Furthermore, passive sampling was carried out at 11 sites in the Pearl River Delta of Southern China from January to April and July to September of 2015. Monosaccharide concentrations derived from PUF–PASs were comparable with the reported data obtained by active sampling, demonstrating that the PUF–PAS approach is valid for monosaccharides monitoring. On the basis of our approach, we found that there is a clear correlation between the monosaccharide concentrations and the MODIS fire activities during January–April.

The light absorption capacity of water‐soluble humic‐like substances (HULISWS) at the molecular level is crucial for reducing the uncertainties in modeling the radiative forcing. This study proposed a machine learning approach to allocate the light absorption coefficient at 365 nm (Abs365) of HULISWSinto 8084 Fourier transform‐ion cyclotron resonance mass spectrometry (FT‐ICR‐MS) detached molecular markers and their potential functional groups. The ML model showed an acceptable uncertainty (<5%) to the whole Abs365value based on the prediction errors. The results showed that five critical light‐absorbing molecules (C4H6O4NS, C8H6O4NS, C11H15O3N2, C12H15O3N2, and C19H21O6) could explain 74% (±3%) of the variation of Abs365in the winter, whereas no crucial light‐absorbing molecules were found in the summer. Besides, the nitrogen‐containing functional groups were found to dominate (61% ± 8%) the molecular absorption near the 365 nm of the spectrum. This work illustrated how functional groups affect the absorption of HULISWS, providing critical information for future research of HULISWSon the molecular level. Water‐soluble humic‐like substances are a crucial light‐absorbing component of fine particulate matter in China. Understanding the crucial light‐absorbing chromophores of the light‐absorbing mixtures was helpful in controlling the global warming event. In this study, CHON and CHONS species were found to dominate the light absorption coefficient of water‐soluble humic‐like substances in Nanjing by combining the machine learning algorithm with the FT‐ICR‐MS technique. Then, the dominant light‐absorbing molecules were further combined with the UV‐Vis spectra from the chemical database to further estimate the light‐absorbing functional groups. Our results indicated that nitrogen‐containing functional groups dominate the light‐absorbing ability of water‐soluble humic‐like substances. Appropriate synthetic minority over‐sampling based few‐shot learning could decipher the light‐absorbing molecules from a small data setC4H6O4NS, C8H6O4NS, C11H15O3N2, C12H15O3N2, and C19H21O6dominate the Abs365of HULISWSin NanjingNitrogen‐containing functional groups dominate the light‐absorbing ability of HULISWSat a micro‐level Appropriate synthetic minority over‐sampling based few‐shot learning could decipher the light‐absorbing molecules from a small data set C4H6O4NS, C8H6O4NS, C11H15O3N2, C12H15O3N2, and C19H21O6dominate the Abs365of HULISWSin Nanjing Nitrogen‐containing functional groups dominate the light‐absorbing ability of HULISWSat a micro‐level

The evolution and the impacts of meteorological conditions on brown carbon (BrC) absorption are not understood, which hinders the assessment of BrC radiative forcing. To address this issue, 1‐hr time‐resolved PM2.5samples collected during three haze events in the North China Plain prior to the COVID‐19 pandemic were used to measure the optical properties of BrC. By coupling excitation‐emission matrix spectroscopy, chemical tracer analysis with multiple model analysis including positive matrix factorization (PMF) and a deweather‐random forest model, we found that a higher proportion of highly oxidized chromophoric components was present in water‐soluble BrC than in methanol‐soluble BrC, indicating the conversion of low‐oxidized water‐insoluble BrC into highly oxidized water‐soluble BrC during the day. The results of the PMF and the deweather‐random forest model showed that aqueous secondary processes were the major contributor to the BrC absorption (68% ± 38%), and the changes in meteorological conditions such as relative humidity (RH) could significantly lead to the changes in the light‐absorbing capacity of BrC, especially the enhancement for water‐soluble BrC and bleaching for methanol‐soluble BrC during the noon and afternoon. We further found that the BrC absorption capacity increased as RH increases to a maximum of ∼65%, and then decreased when RH >65%, highlighting the important role of RH in the generation of water‐soluble BrC. Severe haze events are still common in winter in northern China due to high anthropogenic emissions and adverse meteorological conditions. Atmospheric brown carbon (BrC) is one of the major components influencing the optical properties of aerosols and is closely related to the development of haze. Investigating the source and evolution of BrC, as well as the influence of meteorological factors on BrC absorption, is helpful in understanding the formation mechanism and evolution of haze. Here, we reveal the source, evolution and meteorological influencing factors of soluble BrC in three haze events using multiple model analyses including PMF and random forest. Our results emphasized the substantial impacts of aqueous‐phase reactions of anthropogenic‐related secondary organic aerosols on particle pollution, and meteorological factors are one of the main drivers leading to the increase in BrC absorption during haze periods. Hour‐resolved water‐insoluble brown carbon (BrC) is studied and different diurnal variations are shown between water‐insoluble BrC and water‐soluble BrCThe first generation of aqueous‐phase secondary aerosol formation and fossil combustion were the major sources of soluble BrCMeteorological conditions significantly affected the light absorption capacity of BrC during haze events Hour‐resolved water‐insoluble brown carbon (BrC) is studied and different diurnal variations are shown between water‐insoluble BrC and water‐soluble BrC The first generation of aqueous‐phase secondary aerosol formation and fossil combustion were the major sources of soluble BrC Meteorological conditions significantly affected the light absorption capacity of BrC during haze events

III-nitride InGaN material is an ideal candidate for the fabrication of high performance photovoltaic (PV) solar cells, especially for high-temperature applications. Over the past decade, significant efforts have been made to improve the PV performance of InGaN-based solar cells. In this paper, we perform a comprehensive review of the recent developments in InGaN-based solar cells. The topics of discussion include theoretical modeling, material epitaxy, device engineering, and high-temperature measurement. Particularly, we highlight subjects such as substrate technology, and properties that are unique to InGaN materials such as polarization control and their positive thermal coefficient. To date, outstanding high-temperature InGaN-based solar cells with quantum efficiency approaching 80% at 450 °C have been demonstrated. Future innovations in epitaxy science, device engineering, and integration methods are required to further advance the efficiency and expand the applications of InGaN-based solar cells.

Thermal neutron detectors in a lateral scheme were fabricated from a 70 μm thick freestanding B-10 enriched hexagonal BN (h-10BN). Two sets of channel peaks corresponding to the neutron capture by 10B occurring in h-10BN comprising turbostratic domains (t-10BN) have been recognized in the nuclear reaction pulsed height spectrum, from which a bandgap of 5.5 eV was directly deduced for t-10BN. Improved device performance over the prior state-of-the-art implies that the transport properties in the lateral plane of t-BN domains are sufficiently good and their presence in h-BN is not a showstopper for the further advancement of h-BN detector technologies.

Material that can emit broad spectral wavelengths covering deep ultraviolet, visible, and near-infrared is highly desirable. It can lead to important applications such as broadband modulators, photodetectors, solar cells, bioimaging, and fiber communications. However, there is currently no material that meets such desirable requirement. Here, we report the layered structure of nitrogen-doped graphene quantum dots (N-GQDs) which possess broadband emission ranging from 300 to >1000 nm. The broadband emission is attributed to the layered structure of the N-GQDs that contains a large conjugated system and provides extensive delocalized π electrons. In addition, a broadband photodetector with responsivity as high as 325 V/W is demonstrated by coating N-GQDs onto interdigital gold electrodes. The unusual negative photocurrent is observed which is attributed to the trapping sites induced by the self-passivated surface states in the N-GQDs.

Erbium-doped GaN (GaN:Er) epilayers were synthesized by metal organic chemical vapor deposition. GaN:Er waveguides were fabricated based on four different GaN:Er layer structures: GaN:Er/GaN/Al_2O_3, GaN:Er/GaN/AlN/Al_2O_3, GaN:Er/GaN/Al_0.75Ga_0.25N/AlN/Al_2O_3, and GaN/GaN:Er/GaN/Al_2O_3. Optical loss at 1.54 μm in these waveguide structures has been measured. It was found that the optical attenuation coefficient of the GaN:Er waveguide increases almost linearly with the GaN (002) x-ray rocking curve linewidth. The lowest measured loss was ∼6  dB/cm.

Epilayers of erbium-doped GaN (GaN:Er) were synthesized by metal-organic chemical vapor deposition, and the optical excitation cross section (σ_exc) of Er ions in this host material were determined. Photoluminescence (PL) measurements were made using laser diodes at excitation wavelengths of 375 and 405 nm, and the integrated emission intensity at 1.54 μm was measured as a function of excitation photon flux. Together with time-resolved PL measurements, values of σ_exc of Er ions in GaN:Er were obtained. For excitation at 375 nm, the observed excitation cross section was found to be 4.6×10^−17  cm^−2, which is approximately three orders of magnitude larger than that using resonant excitation. Based on the present and previous works, the optical excitation cross section σ_exc of Er ions in GaN:Er as a function the excitation wavelength has been obtained. The large values of σ_exc with near-band-edge excitation makes GaN:Er attractive for realization of chip-scale photonic devices for optical communications.

Glucose-derived water-soluble crystalline graphene quantum dots (GQDs) with an average diameter as small as 1.65 nm (∼5 layers) were prepared by a facile microwave-assisted hydrothermal method. The GQDs exhibits deep ultraviolet (DUV) emission of 4.1 eV, which is the shortest emission wavelength among all the solution-based QDs. The GQDs exhibit typical excitation wavelength-dependent properties as expected in carbon-based quantum dots. However, the emission wavelength is independent of the size of the GQDs. The unique optical properties of the GQDs are attributed to the self-passivated layer on the surface of the GQDs as revealed by electron energy loss spectroscopy. The photoluminescence quantum yields of the GQDs were determined to be 7–11%. The GQDs are capable of converting blue light into white light when the GQDs are coated onto a blue light emitting diode.

Water‐soluble organic carbon (WSOC) is a substantial component of carbonaceous aerosols in South/East Asia. However, the poorly constrained sources, molecular compositions, and light absorption properties of WSOC over South/East Asian marine regions lead to large uncertainty in climate effects. Herein, we collected marine aerosol samples from South China Sea to the eastern Indian Ocean to investigate the sources, molecular compositions, and light absorption properties of WSOC. The δ13C of Marine‐influenced WSOC (−20.6 ± 1.4‰) was higher than those in Continent‐influenced (South Asia‐influenced: −24.4 ± 1.1‰ and Southeast Asia‐influenced: −22.7 ± 1.0‰, p< 0.01) regions. Additionally, combining with 5‐day back trajectories and the relationships of δ13C‐WSOC with chemical tracers (Cl−/Na+and nonsea salt K+/K+), we found that the Marine‐influenced WSOC was mostly related to oceanic emissions, which was more enriched in saturated primary marine biological compounds with lower oxidation level. In contrast, the Continent‐influenced WSOC was significantly affected by C3 biomass burning and secondary organic aerosols formation, and it has a higher fraction of aromatic and highly oxidized compounds. Moreover, the high aromatic level of Continental‐influenced WSOC may result in high mass absorption efficiency at 365 nm (MAE365) but low absorption Ångström exponent (AAE) values. Taken together with previous WSOC light absorption properties studies, we found that the MAE365of WSOC in urban, rural and background, and marine regions correlated well with AAE. However, the response and correlation coefficients of MAE365to AAE were highest in urban regions, followed by rural and background and marine regions, which is likely associated with different aromatic compound contents. Therefore, in the future, more attention should be paid to the sources and atmospheric processes of condensed aromatic compounds. The Continent‐influenced and Marine‐influenced WSOC were significantly affected by anthropogenic and oceanic emissions, respectivelyThe Continental‐influenced WSOC was more enriched in aromatic compounds, with stronger light absorption capacity than Marine‐influenced WSOCDifference in response and correlation coefficients of MAE365to AAE in different regions may be related to varied aromatic compound contents The Continent‐influenced and Marine‐influenced WSOC were significantly affected by anthropogenic and oceanic emissions, respectively The Continental‐influenced WSOC was more enriched in aromatic compounds, with stronger light absorption capacity than Marine‐influenced WSOC Difference in response and correlation coefficients of MAE365to AAE in different regions may be related to varied aromatic compound contents

By employing a photocurrent excitation spectroscopy measurement, a direct bandgap of ∼6.46 eV has been resolved for the first time in thick B-10 enriched h-BN films. Together with previous band calculations, an unconventional energy diagram has been constructed to capture the unique features of h-BN: h-BN has a minimum direct bandgap of ∼6.5 eV and a bandgap of ∼6.1 eV which is indirect with the conduction band minimum (CBM) at M-point and valence band maximum (VBM) at K-point in the Brillouin zone, and the energy levels of the donor and acceptor impurities are measured relative to CBM and VBM, respectively.

Atmospheric nitrogen‐containing organic compounds (NOCs) are critical components of global nitrogen deposition and light‐absorption species. The sources and compositions of NOCs are complex and remain largely unknown. Here, NOCs in 55 ambient aerosol samples collected in Guangzhou, South China, were analyzed via ultrahigh‐resolution Fourier transform ion cyclotron resonance mass spectrometry in negative‐ion and positive‐ion electrospray ionization (ESI) modes. The molecular compositions of NOCs measured via ESI– and ESI+ exhibited considerable differences. NOCs detected in the negative mode were mainly composed of highly oxygenated organic nitrates (O/N = 6), whereas NOCs detected in the positive mode were mainly composed of reduced nitrogen‐containing compounds (e.g., amides and amino acids). CHN compounds potentially corresponding to amines and alkaloids showed low abundance in the detection modes. Non‐metric multidimensional scaling and individual compound correlation analyses showed that the molecular compositions of NOCs were mainly affected by anthropogenic activities and meteorological parameters. For example, anthropogenic activities such as biomass burning and secondary nitrogen‐chemistry processes led to the accumulation of aromatic and highly oxygenated NOCs during winter. During summer, higher OH radical concentrations and temperatures will result in more prevalent or persistent reduced aliphatic NOCs, particularly lipid‐like amines. Some variables (e.g., relative humidity) have distinct effects on the variation of different types of NOCs. More research is needed to reveal the influencing mechanisms. This study clarifies the molecular compositions of NOCs and the mechanisms by which various factors influence the molecular variations. The findings can guide the assessment of NOCs evolution and deposition. Negative and positive electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI‐FT‐ICR‐MS) was used to characterize the molecular composition of nitrogen‐containing organic compounds (NOCs) from aerosol samples in Guangzhou. It was determined that a large amount of various NOCs are present in the samples, with NOCs in highly oxidative and reduced states can be roughly identified by distinct ionization modes. By combining the ESI‐FT‐ICR‐MS results and statistical analysis, the factors that associated with the distribution of NOCs and how these factors worked were identified. Anthropogenic activities and meteorological parameters (e.g., temperature and oxidation levels) are the two important drivers that led to the variations of NOCs, resulting to inverse molecular patterns with different response to aromatic/highly unsaturated and saturated structures, respectively. This study provides a useful clue for studying NOCs in complex system, bridges the links between the filed observation and knowledge about sources and formation pathways of NOCs that derived from controlled laboratory studies. Most of identified CHON− species had O/N ≥ 3 and showed higher O/C ratios than CHON+ species; CHN only constituted small fraction of nitrogen‐containing organic compounds (NOCs)Biomass burning and secondary inorganic‐nitrogen processes lead to the accumulation of aromatic and phenolic NOCs during winterHigher OH radical concentrations and temperatures result in more prevalent or persistent reduced aliphatic NOCs in summer Most of identified CHON− species had O/N ≥ 3 and showed higher O/C ratios than CHON+ species; CHN only constituted small fraction of nitrogen‐containing organic compounds (NOCs) Biomass burning and secondary inorganic‐nitrogen processes lead to the accumulation of aromatic and phenolic NOCs during winter Higher OH radical concentrations and temperatures result in more prevalent or persistent reduced aliphatic NOCs in summer

A hybrid TiO 2−carbon nanofiber hierarchical nanostructure has been fabricated by the metal−organic chemical vapor deposition of a TiO 2layer onto the vertically aligned carbon nanofiber array. As the deposition time increases from 10 to 60 min, the TiO 2coating changes from the particulated conformal ultrathin film to a nanoneedle-like texture along the sidewall of the carbon nanofibers. X-ray diffraction indicates that the TiO 2form anatase crystals with the coherent length over 50 nm, in good agreement with transmission electron microscopy images. Photoluminescence spectra are taken at both room temperature and 10 K. The absence of photoluminescence emission indicates that the electron−hole recombination in TiO 2is completely quenched in such core−shell hybrid structure. The charge separation may be much more effective at the TiO 2−carbon nanofiber heterojunction. The nanoneedle-like texture drastically increases the effective surface area of the TiO 2while maintaining a much more effective electrical wiring through the highly conductive carbon nanofiber core. Such hierarchical architecture may be used as a novel anode material for dye-sensitized solar cells.

Normal, sham, and groups of chickens subjected to pinealectomy from which serum melatonin levels were measured and correlated with scoliosis development in a period of 5 weeks.

This study traced the location, extent, and pathway of sensory feedback after the mechanical stretching of a lateral spinal ligament in young chickens. The pathway was traced by locating the sites of Fos protein production in neuronal cell bodies at various sites in the nervous system.

The characteristics of the scoliosis that develops after pinealectomy in young chickens were determined from weekly posteroanterior radiographs. These data were compared with similar data collected from human patients with adolescent idiopathic scoliosis.

To use fresh, human supraspinal and interspinal ligments and document their innervation.

This study used human cadaveric material to examine the three-dimensional morphology and biomechanics of the superior and lateral costo-transverse ligaments and the intertransverse ligament of the spine.

Matched pairs of adolescent girls were used to compare serum melatonin levels in adolescent patients and control subjects with idiopathic scoliosis during the day and in the middle of the night.

The isotope tracer technique plays a key role in identifying the sources and atmospheric processes affecting pollution. The sources of brown carbon (BrC) at Guangzhou during 2017–2018 were characterized by positive matrix factorization with radiocarbon isotope constraints and multiple linear regression analysis. The primary emission factors of fossil fuel combustion (FF) and biomass burning (BB) accounted for 34% and 27% of dissolved BrC absorption at λ= 365 nm (Abs365), respectively. The total mean light absorption contributed by secondary sources was 39%. The FF‐origin Abs365changed insignificantly throughout the year and was dominant in the summer monsoon period, whereas the Abs365from BB and secondary nitrate formation increased and contributed larger fractions during the winter monsoon period. Transported BrC was estimated using an index of 7Be/(7Be + n210Pb). Higher values were generally accompanied by lower Abs365, whereas lower values were associated with higher Abs365, indicating that BrC absorption of aerosols transported from the upper‐atmosphere is lower than that of aerosols transported near the surface. Based on the positive correlations between 210Pb and Abs365and non‐fossil dissolved organic carbon in the winter monsoon period, we estimated that the contribution of invasive BrC (include ground and upper‐atmosphere level) to total absorption during the period of elevated BrC was ∼50%. The transported BrC was likely related to BB organic aerosols and secondary nitrate formation processes. This study supports radionuclides as a novel method for characterizing the sources and transport of BrC that can be applied in future atmospheric research. 14C‐constrained PMF model showed that fossil combustion, biomass burning and secondary sources contributed 34%, 27%, and 39% of total BrC absorption, respectivelyBrC absorption increased during winter with the transport of BBOA and secondary nitrates formation processes210Pb‐based estimation reveal that the transport BrC accounted for ∼50% of total BrC absorption during winter monsoon 14C‐constrained PMF model showed that fossil combustion, biomass burning and secondary sources contributed 34%, 27%, and 39% of total BrC absorption, respectively BrC absorption increased during winter with the transport of BBOA and secondary nitrates formation processes 210Pb‐based estimation reveal that the transport BrC accounted for ∼50% of total BrC absorption during winter monsoon

The light-absorbing organic aerosol referred to as brown carbon (BrC) affects the global radiative balance. The linkages between its molecular composition and light absorption properties and how environmental factors influence BrC composition are not well understood. In this study, atmospheric dissolved organic matter (ADOM) in 55 aerosol samples from Guangzhou was characterized using Fourier transform ion cyclotron resonance mass spectrometry and light absorption measurements. The abundant components in ADOM were aliphatics and peptide-likes (in structure), or nitrogen- and sulfur-containing compounds (in elemental composition). The light absorption properties of ADOM were positively correlated with the levels of unsaturated and aromatic structures. Particularly, 17 nitrogen-containing species, which are identified by a random forest, characterized the variation of BrC absorption well. Aggregated boosted tree model and nonmetric multidimensional scaling analysis show that the BrC composition was largely driven by meteorological conditions and anthropogenic activities, among which biomass burning (BB) and OH radical were the two important factors. BrC compounds often accumulate with elevated BB emissions and related secondary processes, whereas the photolysis/photooxidation of BrC usually occurs under high solar radiance/•OH concentration. This study first illuminated how environmental factors influence BrC at the molecular level and provided clues for the molecular-level research of BrC in the future.

Erbium-doped GaN (Er:GaN) possesses superior optical, mechanical and thermal properties and is a very promising material as a gain medium for solid-state high-energy lasers. We report here the optical properties of GaN/Er:GaN/GaN core-cladding planar waveguides (PWGs). Optical confinement in the core layer has been investigated. The measured optical loss coefficients of Er:GaN PWGs at 1.54 ?m are 1.0 cm?1for the TE polarization mode and 1.2 cm?1for the TM polarization mode. Approaches to further reduce optical loss and the optimal configuration for resonantly pumped GaN/Er:GaN/GaN PWGs for achieving amplification near 1.5 ?m have been identified.

Hexagonal boron nitride (h-BN) has emerged as an important extreme bandgap semiconductor as well as a two-dimensional material. Achieving the ability for tuning the optoelectronic properties through alloying and heterojunction will further expand the applications of h-BN. By utilizing h-BN epilayer as a template, the synthesis of BN-rich B1?xGaxN alloys and quantum wells crystalized in the hexagonal phase has been demonstrated for the first time by metal organic chemical vapor deposition. The incorporation of Ga tends to enhance the conductivity. A blue shift in the band-edge emission upon the formation of h-BN/BGaN/BN QW has been observed, indicating the feasibility for heterojunction formation.

InGaN alloys are promising for solar cells and solar water splitting because they have direct bandgaps that cover almost the whole solar spectrum. This paper provides a brief overview on recent advances made by our group in the area of III-nitrides for energy and hydrogen generation. Solar cells based on InxGa1-xN/GaN (x∼0.35) multiple quantum well (MQW) structures have been fabricated and were shown exhibit an open circuit voltage (Voc) of 1.80 V, short circuit current density (Jsc) of 2.5 mA/cm2and a solar-energy-to-electricity conversion efficiency (η) of 2.95% under the irradiation by a simulated sunlight (AM 1.5 G, 1-sun,100 mW/cm2). Under the irradiation of concentrated sunlight, Voc, Jscand η were found to increase with solar concentration. Furthermore, InGaN/GaN MQW solar cells were effectively monolithic solar-photoelectrochemical cells which are capable to directly generate hydrogen gas under zero bias via solar watersplitting. Under the irradiation of 1 sun (AM 1.5 G), a 1.5% solar to-fuel conversion efficiency has been achieved under zero bias with an excellent chemical stability.

A multi-scale approach is essential to assess the factors that limit avian habitat use. Numerous studies have examined habitat use by the red-crowned crane, but integrated multi-scale habitat use information is lacking. We evaluated the effects of several habitat variables quantified across many spatial scales on crane use and abundance in two periods (2000 and 2009) at Yancheng National Nature Reserve, China. The natural wetlands decreased in area by 30,601 ha (-6.9%) from 2000 to 2009, predominantly as a result of conversion to aquaculture ponds and farmland, and the remaining was under degradation due to expansion of the exotic smooth cordgrass. The cranes are focusing in on either larger patches or those that are in close proximity to each other in both years, but occupied patches had smaller size, less proximity and more regular boundaries in 2009. At landscape scales, the area percentage of common seepweed, reed ponds and paddy fields had a greater positive impact on crane presence than the area percentage of aquaculture ponds. The cranes were more abundant in patches that had a greater percent area of common seepweed and reed ponds, while the percent area of paddy fields was inversely related to crane abundance in 2009 due to changing agricultural practices. In 2009, cranes tended to use less fragmented plots in natural wetlands and more fragmented plots in anthropogenic paddy fields, which were largely associated with the huge loss and degradation of natural habitats between the two years. Management should focus on restoration of large patches of natural wetlands, and formation of a relatively stable area of large paddy field and reed pond to mitigate the loss of natural wetlands.