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1.
Environ Sci Technol ; 2020 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-32600027

RESUMO

China has large anthropogenic chlorine emissions from agricultural fires, residential biofuel, waste incineration, coal combustion, and industrial processes. Here we quantify the effects of chlorine on fine particulate matter (PM2.5) and ozone air quality across China by using the GEOS-Chem chemical transport model with comprehensive anthropogenic emissions and detailed representation of gas-phase and heterogeneous chlorine chemistry. Comparison of the model to observed ClNO2, HCl, and particulate Cl- concentrations shows that reactive chlorine in China is mainly anthropogenic, unlike in other continental regions where it is mostly of marine origin. The model is successful in reproducing observed concentrations and their distributions, lending confidence in the anthropogenic chlorine emission estimates and the resulting chemistry. We find that anthropogenic chlorine emissions increase total inorganic PM2.5 by as much as 3.2 µg m-3 on an annual mean basis through the formation of ammonium chloride, partly compensated by a decrease of nitrate because ClNO2 formation competes with N2O5 hydrolysis. Annual mean MDA8 surface ozone increases by up to 1.9 ppb, mainly from ClNO2 chemistry, while reactivities of volatile organic compounds increase (by up to 48% for ethane). We find that a sufficient representation of chlorine chemistry in air quality models can be obtained from consideration of HCl/Cl- thermodynamics and ClNO2 chemistry, because other more complicated aspects of chlorine chemistry have a relatively minor effect.

2.
Nanoscale ; 2020 Jun 23.
Artigo em Inglês | MEDLINE | ID: mdl-32573630

RESUMO

We report two novel homoleptic alkynyl-protected gold nanoclusters, which were synthesized by direct reduction of AuC[triple bond, length as m-dash]CR. Single-crystal X-ray structural analysis reveals that they have compositions of Au42(C[triple bond, length as m-dash]CC6H4-2-CF3)22 (1) and Au50(C[triple bond, length as m-dash]C6H4-3-F)26 (2), respectively. Cluster 2 is the first Au50 nanocluster, and the metal-to-ligand ratios of 1 and 2 are different from those of known Aun(SR)m or Aux(C[triple bond, length as m-dash]CR)y nanoclusters. In addition, the metal kernels of these two clusters are built up unprecedented units. This work offers further insights into the synthesis of all-alkynyl-protected gold nanoclusters via a direct reduction method.

3.
Sci Total Environ ; 735: 139317, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32473443

RESUMO

Nitrous Acid (HONO) is an important precursor of hydroxyl radical (OH) and has significant impacts on the formation of Ozone (O3) and Secondary Organic Aerosol (SOA). The atmospheric concentrations of HONO were measured during early autumn in downtown, Beijing (China). This study investigated HONO pollution characteristics and potential sources during day and night. The maximum hourly HONO levels reached 5.16 ppb, with 1.23 ppb on average. HONO concentration exhibited typical diurnal variation characteristics, with maximum at nighttime and minimum at daytime. The potential sources mainly included vehicle emission, heterogeneous reaction of NO2 on aerosol surfaces (Photo-enhanced at the daytime) and photolysis of particulate nitrate (NO3-) in Beijing. Vehicle emission was an important HONO source, particular at the morning rush period and lower HONO concentration. The simulated results highlighted that the main contribution of HONO was NO2 heterogeneous reaction on aerosol surfaces. The photolysis of particulate NO3- was also an important daytime HONO source, particularly in the pollution period. The main loss routine was the photolysis of HONO and dry deposition at day and night, respectively.

4.
Artigo em Inglês | MEDLINE | ID: mdl-32382903

RESUMO

The aerosol samples of water-soluble inorganic ions (WSIs), including SO42-, NO3-, NH4+, Cl-, K+, Na+, Ca2+, and Mg2+ in size-segregated particulate matter (PM), were collected by an Anderson sampler (with 8 nominal cut-sizes ranged from 0.43 to 9.0 µm) in urban Tianjin during 2013-2014. The results showed that particulate matters in the fine mode (PM2.1, Dp < 2.1 µm) comprised large part of mass concentrations of aerosols, and the water-soluble ionic species in the fine mode were 47.07 ± 14.29 µg m-3 (spring), 67.87 ± 28.74 µg m-3 (summer), 86.60 ± 48.53 µg m-3 (autumn), and 104.16 ± 51.76 µg m-3 (winter), respectively, which accounted for 59.5%, 63.3%, 71.9%, and 71.4% of the PM2.1 mass concentrations. Secondary pollutants of SO42-, NO3-, and NH4+ (SNA) were the dominant contributors of WSIs, which showed a bimodal size distribution in each season, with the larger peak appeared in the size fraction of 0.65-1.1 µm and the smaller one in 3.3-5.8 µm fraction. SNA concentrations in lightly polluted days (LPD) and heavily polluted days (HPD) were observably higher than non-polluted days (NPD), especially in the fine mode, with the peak diameter moving from 0.43-0.65 µm on NPD to 0.65-1.1 µm on LPD and HPD. The correlation analysis between NH4+, NO3-, and SO42- suggested that almost all SO42- and NO3- for fine particles had been completely neutralized by NH4+, and primarily existed in the forms of (NH4)2SO4 and NH4NO3. The sulfur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR) on LPD and HPD in fine mode were observably higher than those on NPD, especially in the range of 0.65-1.1 µm and 1.1-2.1 µm. Furthermore, SOR and NOR values in the size fraction of 0.43-3.3 µm increase as the RH elevated, especially in 0.43-2.1 µm, where RH was significantly positive correlated with SOR and NOR, indicating the significant contributions of heterogeneous processes to the secondary formation of SO42- and NO3-. These results suggested an enhanced formation ability of secondary pollutants under high RH in the coast city. Therefore, controlling the precursors of SNA, such as SO2 and NOx, would be more effective to reduce the fine particulate pollution in the coast megacity of Tianjin.

5.
Proc Natl Acad Sci U S A ; 117(18): 9755-9761, 2020 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-32300007

RESUMO

Aerosol-radiation interaction (ARI) plays a significant role in the accumulation of fine particulate matter (PM2.5) by stabilizing the planetary boundary layer and thus deteriorating air quality during haze events. However, modification of photolysis by aerosol scattering or absorbing solar radiation (aerosol-photolysis interaction or API) alters the atmospheric oxidizing capacity, decreases the rate of secondary aerosol formation, and ultimately alleviates the ARI effect on PM2.5 pollution. Therefore, the synergetic effect of both ARI and API can either aggravate or even mitigate PM2.5 pollution. To test the effect, a fully coupled Weather Research and Forecasting (WRF)-Chem model has been used to simulate a heavy haze episode in North China Plain. Our results show that ARI contributes to a 7.8% increase in near-surface PM2.5 However, API suppresses secondary aerosol formation, and the combination of ARI and API results in only 4.8% net increase of PM2.5 Additionally, API increases the solar radiation reaching the surface and perturbs aerosol nucleation and activation to form cloud condensation nuclei, influencing aerosol-cloud interaction. The results suggest that API reduces PM2.5 pollution during haze events, but adds uncertainties in climate prediction.

6.
J Environ Sci (China) ; 89: 136-144, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31892386

RESUMO

Qualitative and quantitative analyses of derivatized phenols in Beijing and in Xinglong were performed from 2016 to 2017 using gas chromatography-mass spectrometry. The results showed substantially more severe pollution in Beijing. Of the 14 compounds detected, the total average concentration was 100 ng/m3 in Beijing, compared with 11.6 ng/m3 in Xinglong. More specifically, concentration of nitro-aromatic compounds (NACs) (81.9 ng/m3 in Beijing and 8.49 ng/m3 in Xinglong) was the highest, followed by aromatic acids (14.6 ng/m3 in Beijing and 2.42 ng/m3 in Xinglong) and aromatic aldehydes (3.62 ng/m3 in Beijing and 0.681 ng/m3 in Xinglong). In terms of seasonal variation, the highest concentrations were found for 4-nitrocatechol in winter in Beijing (79.1 ± 63.9 ng/m3) and 4-nitrophenol in winter in Xinglong (9.72 ± 8.94 ng/m3). The analysis also revealed diurnal variations across different seasons. Most compounds presented higher concentrations at night in winter because of the decreased boundary layer height and increased heating intensity. While some presented higher levels during the day, which attributed to the photo-oxidation process for summer and more biomass burning activities for autumn. Higher concentrations appeared in winter and autumn than in spring and summer, which resulted from more coal combustions and adverse meteorological conditions. The significant correlations among NACs indicated similar sources of pollution. Higher correlations presented within each subgroup than those between the subgroups. Good correlations between levoglucosan and nitrophenols, nitrocatechols, nitrosalicylic acids, with correlation coefficients (r) of 0.66, 0.69 and 0.69, respectively, indicating an important role of biomass burning among primary sources.


Assuntos
Poluentes Atmosféricos , Monitoramento Ambiental , Material Particulado , Fenóis/análise , Pequim , China , Estações do Ano
7.
Sci Total Environ ; 705: 135803, 2020 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-31972941

RESUMO

To investigate the regional transport and formation mechanisms of submicron aerosols in the North China Plan (NCP), for the first time, we conducted simultaneous combined observations of the non-refractory submicron aerosols (NR-PM1) chemical compositions using aerosol mass spectrometer at urban Beijing (BJ) and at regional background area of the NCP (XL), from November 2018 to January 2019. During the observation period, average mass concentrations of PM1 in BJ and XL were 26.6 ± 31.7 and 16.0 ± 18.7 µg m-3 respectively. The aerosol composition in XL showed a lower contribution of organic aerosol (33% vs. 43%) and higher fractions of nitrate (35% vs. 30%), ammonium (16% vs. 13%), and chlorine (2% vs. 1%) than in BJ. Additionally, a higher contribution of secondary organic aerosol (SOA) was also observed in XL, suggesting low primary emissions and highly oxidized OA in the background area. Nitrate displayed a significantly enhanced contribution with the aggravation of aerosol pollution in both BJ and XL, which was completely neutralized by excess ammonium at both sites, suggesting that the abundant ammonia emissions in the NCP favor nitrate formation on a regional scale. In addition, a higher proportion of nitrate in XL can be attributed to the more neutral and higher oxidation capacity of the background atmosphere. Heterogeneous aqueous reaction plays an important role in sulfate and SOA formation, and is more efficient in BJ which can be attributed to the higher aerosol surface areas at urban site. Regional transport from the southwestern regions of NCP showed a significant impact on the formation of haze episodes. Beside the invasion of transported pollutants, the abundant water vapor associated with the air mass to the downwind background area further enhanced local secondary transformation and expanded the regional scope of the haze pollution in the NCP.

8.
Sci Total Environ ; 710: 136304, 2020 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-31927286

RESUMO

Crop residue burning in China increased significantly in the last decade, especially it took up a majority in Northeast China, which plays an important role of severe haze pollution. Hence, two main types of crop residues (corn and rice straw) were chosen to characterize the particle number concentration, chemical components of fine particulate matter and optical properties of carbonaceous aerosols by a suite of fast-response online portable instruments, together with offline sampling and analysis, during the field-based combustion experiments in Northeast China. For the range of 250 and 2500 nm, more particles were emitted from rice straw burning than those from corn straw burning, and the time-averaged number concentration of particles during the flaming process was approximately 2 times higher than that during the smoldering process for these two straws. Organic carbon (OC), elemental carbon (EC) and water-soluble ions were the most abundant components and accounted for 42.5 ± 7.5%, 7.7 ± 1.7% and 18.0 ± 3.4% of the PM2.5, respectively. Furthermore, rice straw burning emitted higher OC and lower Cl- and K+ than those from corn straw burning. The average absorption Ångström exponent (AAE) of carbonaceous aerosols was 2.1 ± 0.3, while the AAE of brown carbon (BrC) was 4.7 ± 0.4 during the whole burning process. On average, BrC contributed to 63% and 20% of the total light absorption at 375 nm and 625 nm, respectively. Parameterization of BrC absorption revealed that the fraction of absorption from BrC has a reasonably good correlation with EC/OC (-0.84) and AAE (0.94) at 375 nm. Generally, combustion conditions can affect the optical properties of carbonaceous aerosols, and a negative correlation (-0.77) was observed between the AAE and modified combustion efficiency; in addition, the percentage of absorption due to BrC were lower at the flaming phase.

9.
Huan Jing Ke Xue ; 41(1): 82-89, 2020 Jan 08.
Artigo em Chinês | MEDLINE | ID: mdl-31854907

RESUMO

We study the seasonal variations of δ13C ratios in aerosol fine particulate matter (PM2.5) using 91 PM2.5 samples collected from Xinxiang, China, during the summer and winter in 2017. Mass concentrations of total carbon (TC), water soluble ions, and stable carbon isotope ratios (δ13C) were determined. The mean concentrations of TC in the summer and winter were 11.78 µg·m-3 and 26.6 µg·m-3, respectively. The δ13C ratio in the summer ranged from -27.70‰ to -25.22‰. The daily δ13C ratio fluctuated in the first half of the summer months (mean -26.96‰), whereas the δ13C ratio in the second half of the summer was relatively stable (mean -25.69‰). The number of fires in the study area during the first half of the summer was quite different to the number during the second half of the summer, meanwhile, there was a positive correlation between the Knss+ concentration and the TC mass concentration (R2=0.62, P<0.01). This indicates that biomass burning most likely contributed to variations in δ13C. During the winter there was a significant negative correlation between winter RH and the TC/PM2.5 mass ratio (R2=0.68, P<0.01), which suggests that SOA growth was dominant in the early stage of haze development, whereas the pollution period was dominated by SIA components. The ratio of δ13C ranged from -26.72‰ to -23.49‰, and there was a difference between the variation of the δ13C ratio in haze episode (when it was mainly enriched in the development stage) to that in the stage dominated by depletion.

10.
Proc Natl Acad Sci U S A ; 116(49): 24463-24469, 2019 12 03.
Artigo em Inglês | MEDLINE | ID: mdl-31740599

RESUMO

From 2013 to 2017, with the implementation of the toughest-ever clean air policy in China, significant declines in fine particle (PM2.5) concentrations occurred nationwide. Here we estimate the drivers of the improved PM2.5 air quality and the associated health benefits in China from 2013 to 2017 based on a measure-specific integrated evaluation approach, which combines a bottom-up emission inventory, a chemical transport model, and epidemiological exposure-response functions. The estimated national population-weighted annual mean PM2.5 concentrations decreased from 61.8 (95%CI: 53.3-70.0) to 42.0 µg/m3 (95% CI: 35.7-48.6) in 5 y, with dominant contributions from anthropogenic emission abatements. Although interannual meteorological variations could significantly alter PM2.5 concentrations, the corresponding effects on the 5-y trends were relatively small. The measure-by-measure evaluation indicated that strengthening industrial emission standards (power plants and emission-intensive industrial sectors), upgrades on industrial boilers, phasing out outdated industrial capacities, and promoting clean fuels in the residential sector were major effective measures in reducing PM2.5 pollution and health burdens. These measures were estimated to contribute to 6.6- (95% CI: 5.9-7.1), 4.4- (95% CI: 3.8-4.9), 2.8- (95% CI: 2.5-3.0), and 2.2- (95% CI: 2.0-2.5) µg/m3 declines in the national PM2.5 concentration in 2017, respectively, and further reduced PM2.5-attributable excess deaths by 0.37 million (95% CI: 0.35-0.39), or 92% of the total avoided deaths. Our study confirms the effectiveness of China's recent clean air actions, and the measure-by-measure evaluation provides insights into future clean air policy making in China and in other developing and polluting countries.

11.
Environ Sci Technol ; 53(21): 12529-12538, 2019 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-31576752

RESUMO

Ammonia (NH3) emission inventories are an essential input in chemical transport models and are helpful for policy-makers to refine mitigation strategies. However, current estimates of Chinese NH3 emissions still have large uncertainties. In this study, an improved inversion estimation of NH3 emissions in China has been made using an ensemble Kalman filter and the Nested Air Quality Prediction Modeling System. By first assimilating the surface NH3 observations from the Ammonia Monitoring Network in China at a high resolution of 15 km, our inversion results have provided new insights into the spatial and temporal patterns of Chinese NH3 emissions. More enhanced NH3 emission hotspots, likely associated with industrial or agricultural sources, were captured in northwest China, where the a posteriori NH3 emissions were more than twice the a priori emissions. Monthly variations of NH3 emissions were optimized in different regions of China and exhibited a more distinct seasonality, with the emissions in summer being twice those in winter. The inversion results were well-validated by several independent datasets that traced gaseous NH3 and related atmospheric processes. These findings highlighted that the improved inversion estimation can be used to advance our understanding of NH3 emissions in China and their environmental impacts.


Assuntos
Poluentes Atmosféricos , Poluição do Ar , Amônia , China , Monitoramento Ambiental
12.
Small ; 15(39): e1902890, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31390149

RESUMO

Thanks to their unique optical and electric properties, 2D materials have attracted a lot of interest for optoelectronic applications. Here, the emerging 2D materials, organic-inorganic hybrid perovskites with van der Waals interlayer interaction (Ruddlesden-Popper perovskites), are synthesized and characterized. Photodetectors based on the few-layer Ruddlesden-Popper perovskite show good photoresponsivity as well as good detectivity. In order to further improve the photoresponse performance, 2D MoS2 is chosen to construct the perovskite-MoS2 heterojunction. The performance of the hybrid photodetector is largely improved with 6 and 2 orders of magnitude enhancement for photoresponsivity (104 A W-1 ) and detectivity (4 × 1010 Jones), respectively, which demonstrates the facile charge separation at the interface between perovskite and MoS2 . Furthermore, the contribution of back gate tuning is proved with a greatly reduced dark current. The results demonstrated here will open up a new field for the investigation of 2D perovskites for optoelectronic applications.

13.
Sci Total Environ ; 687: 1073-1086, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31412445

RESUMO

Fine particle explosive growth (FPEG) events are frequently observed in heavy haze episodes in Beijing, the characteristics and formation mechanism of which remain not fully understood. In this study, a five year (2013-2017) online observation was conducted in Beijing and the chemical evolution pattern of FPEG events was analyzed to understand its formation mechanism. A total of 132 FPEG events were identified, and steadily decreased from 39 events in 2013 to 19 events in 2017. More than 70% of the FPEG events occurred in winter and autumn, which coincides with adverse weather conditions and enhanced primary emissions. Organic matter (OM) was the dominated components (~30%) in PM2.5, but it only accounted for 10% of total FPEG events as a driven factor, because its contribution usually decreased when the FPEG events developed. In contrast, the secondary inorganic species were the dominated driven factors, and sulfate-driven events accounted >50%. During the period of 2013-2017, the contribution from regional sources decreased significantly mainly due to the reduction of emissions from regional sources, while the contribution from local sources remained largely unchanged, indicating that the local secondary transformation played a leading role in promoting the FPEG events. The low nitrogen oxidation rates (NOR, 0.12 ±â€¯0.07) and the weak increase trend of NOR with elevated RH were observed, indicating the formation of which might be promoted by the homogenous reaction between HNO3 and NH3. In contrast, a significant increase in sulfur oxidation rate (SOR, 0.50 ±â€¯0.19) was observed when RH > 50%, suggesting enhanced heterogeneous oxidation of SO2 in FPEG events. In addition, our analysis suggest the S (IV) heterogeneous oxidation rates in FPEG events depend mainly on the aerosol liquid water content (ALWC) in addition to the aerosol acidity. This study provides observational evidence for understanding the formation mechanism of FPEG events in Beijing.

14.
Sci Total Environ ; 677: 215-229, 2019 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-31055101

RESUMO

North China registers frequent air pollution episodes from high PM2.5 concentrations. Shijiazhuang is located at the intensive industrial zone of this region, but there is insufficient data on the chemical composition of PM2.5 and its sources in this city. In this study, the chemical and seasonal characteristics of PM2.5 in Shijiazhuang were investigated based on 12-h integrated PM2.5 measurements made over eight 1-month periods in each season between June 2014 and April 2016 (486 samples). The eight-season average concentration of PM2.5 was 138.8 µg m-3, and the major chemical components were secondary inorganic aerosol (SIA) species of sulfate, nitrate, and ammonium (41.5%), followed by organic matter (25.9%). The mass concentration and most of the chemical components of PM2.5 showed clear seasonal variation, with a winter-high and summer-low pattern. SO42- and NO3- were the dominant components at each pollution level in summer and autumn (18.1%-30.6% and 14.2%-27.0%, respectively). Sufficient gaseous oxidants (O3) concentrations and suitable meteorology conditions were observed in these two seasons. Highest SOR (0.61), SO42-/EC(10.8) and NOR (0.58), NO3-/EC (5.9) were found in summer and autumn, which indicated intense secondary transformation in these two seasons. Organic matter was the dominant species in winter, which increased from 17.1 µg m-3 for clean days (28.7% of PM2.5) to 169.1 µg m-3 (38.4% of PM2.5). The accumulation of primary emissions (coal combustion and biomass burning) was responsible for the increasing OM trend (especially for POC). The highest and leading proportion of mineral dust occurred in spring (20.3%-46.5%) as a result of higher wind speeds (up to 3 m/s). Potential source contribution function (PSCF) analyses implied that the border areas of Hebei, Henan and Shandong Provinces, together with the central area of Shanxi Province, contributed significantly to the PM2.5 pollution in Shijiazhuang, especially in autumn and winter.

15.
Nanoscale Res Lett ; 14(1): 95, 2019 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-30874915

RESUMO

The rapid recombination of electron-hole pairs in BiVO4 has limited its performance as a photocatalysis. In this paper, BiVO4 is combined with Cu2-xSe semiconductor to slow down the recombination process, and thus improve its photocatalytic activity. This is enabled by careful band structure design. The work function of Cu2-xSe is larger than that of BiVO4. Therefore, electrons flow to Cu2-xSe from BiVO4 after the composition. Accordingly, an inner field could be built, which facilitates the separation of electrons and holes. The experimental result shows that the photocatalytic efficiency of the 3 wt% Cu2-xSe/BiVO4 composite is 15.8 times than that of pure BiVO4.

16.
J Colloid Interface Sci ; 546: 276-284, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30925434

RESUMO

Colloidal quantum dots (QDs) have attracted a great amount of attention for their appealing optoelectronic properties. In this work, the CuInS2 (CIS)/ZnS core/shell QDs based on 4.3 nm cores with various layers of ZnS shell (0 to 10) were synthesized. With the sequential growth of a ZnS shell over a CIS core, the band alignment of core/shell QDs converts from a type I to quasi-type II structure. This conversion prolongs the carrier lifetime and affects the electron transfer rate (Ket) and electron transfer efficiency (ηET). A comparative study indicates that the photovoltaic performance of CIS based QDSCs can be markedly improved by optimizing the layers of ZnS shell. The highest photo conversion efficiency (PCE) of 2.07% is obtained at optimum ZnS thickness of about 1.55 nm. These results show tuning the thickness of shell to change the band alignment is an effective strategy to manipulate the carriers transportation behaviors and thus affect the PCE of CIS-based optoelectronic devices.

17.
ACS Sens ; 4(2): 488-497, 2019 02 22.
Artigo em Inglês | MEDLINE | ID: mdl-30644736

RESUMO

Exosomes contain cell- and cell-state-specific cargos of proteins, lipids, and nucleic acids and play significant roles in cell signaling and cell-cell communication. Current research into exosome-based biomarkers has relied largely on analyzing candidate biomarkers, i.e., specific proteins or nucleic acids. However, this approach may miss important biomarkers that are yet to be identified. Alternative approaches are to analyze the entire exosome system, either by "omics" methods or by techniques that provide "fingerprints" of the system without identifying each individual biomolecule component. Here, we describe a platform of the latter type, which is based on surface-enhanced Raman spectroscopy (SERS) in combination with multivariate analysis, and demonstrate the utility of this platform for analyzing exosomes derived from different biological sources. First, we examined whether this analysis could use exosomes isolated from fetal bovine serum using a simple, commercially available isolation kit or necessitates the higher purity achieved by the "gold standard" ultracentrifugation/filtration procedure. Our data demonstrate that the latter method is required for this type of analysis. Having established this requirement, we rigorously analyzed the Raman spectral signature of individual exosomes using a unique, hybrid SERS substrate made of a graphene-covered Au surface containing a quasi-periodic array of pyramids. To examine the source of the Raman signal, we used Raman mapping of low and high spatial resolution combined with morphological identification of exosomes by scanning electron microscopy. Both approaches suggested that the spectra were collected from single exosomes. Finally, we demonstrate for the first time that our platform can distinguish among exosomes from different biological sources based on their Raman signature, a promising approach for developing exosome-based fingerprinting. Our study serves as a solid technological foundation for future exploration of the roles of exosomes in various biological processes and their use as biomarkers for disease diagnosis and treatment monitoring.


Assuntos
Exossomos/metabolismo , Análise Espectral Raman/métodos , Animais , Análise Multivariada , Ultracentrifugação
18.
Sci Total Environ ; 655: 581-590, 2019 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-30476838

RESUMO

PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) during winter 2015 at three urban sites, including Beijing, Tianjin and Shijiazhuang, and one background site (Xinglong) over the North China Plain (NCP) were investigated. The spatial variations of PAHs showed the same trends with PM2.5 mass concentrations, i.e. the highest PAHs concentrations was in Shijiazhuang, followed by Tianjin, Beijing and the lowest PAHs concentrations was in Xinglong. The diurnal variations of PAHs exhibited PAHs concentrations during nighttime were higher than those during daytime. The dominant species in PAHs were fluranthene and benzo[b + k]fluoranthene, indicating that diesel vehicle emission, coal combustion and biomass burning could be important and potential sources for PAHs over the NCP. There results were supported by diagnostic ratios analysis. But coefficient of divergence analysis showed that a high extent of spatial contrast among four sampling sites, except between Beijing and Tianjin. Analysis of toxicity equivalent quantities (TEQ) and the lifetime excess cancer risk (ECR) from inhalation exposure to PAHs showed that 818, 1517, 5129 and 182 cases per 100,000 people exposed in Beijing, Tianjin, Shijiazhuang and Xinglong, respectively, which were much higher than the threshold value suggested by US-EPA, i.e. 1 case per 100,000 people, and indicating that the NCP suffered from very serious health risk from PAHs, especially in Shijiazhuang.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Exposição por Inalação/análise , Material Particulado/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Estações do Ano , Poluentes Atmosféricos/química , China , Humanos , Tamanho da Partícula , Material Particulado/química , Hidrocarbonetos Policíclicos Aromáticos/química , Risco
19.
Environ Pollut ; 243(Pt B): 1740-1749, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30408861

RESUMO

Hourly concentrations of water-soluble inorganic ions (Na+, NH4+, K+, Mg2+, Ca2+, Cl-, NO3- and SO42-) in PM2.5 and related reactive gases were measured with a Gas and Aerosol Collector combined with Ion Chromatography (GAC-IC) in urban Chengdu from April 17 to May 27, 2017, during which both haze and dust episodes occurred frequently. Nitrate was the most abundant ion in PM2.5 and substantially increased during haze pollution with the NO3-/SO42- mass ratio increasing from 0.78 during clean period to 1.1 during haze period. Aerosols in Chengdu were generally ammonium-rich, wherein ammonium nitrate was primarily formed through homogeneous gas-phase reactions and limited by the availability of HNO3, indicating that preferentially reducing the emissions of NOx could make for mitigating spring haze pollution in Chengdu. Backward trajectory clustering coupled with measured species and a potential source contribution function (PSCF) for PM2.5, PM10/PM2.5, sulfate, nitrate, ammonium, and Ca2+ indicated that regionally transported pollutants from the southern and southeastern Sichuan Basin strongly contributed to springtime PM2.5 pollution in Chengdu, but long-distance transport from northwestern China also contributed to dust pollution. Moreover, the treatment of urban fugitive dust in southern Sichuan is also important for reducing coarse particles in Chengdu. Therefore, the improvement of air quality in Chengdu, even in the Sichuan Basin, requires the regional joint emission reduction of particles and gaseous precursors across the entire Sichuan Basin, especially for cities located in southeastern Sichuan Basin.


Assuntos
Aerossóis/análise , Poluentes Atmosféricos/análise , Poluição do Ar/análise , Poeira/análise , Monitoramento Ambiental/métodos , Nitratos/análise , China , Cidades , Gases/análise , Nitratos/química , Óxidos de Nitrogênio/análise , Estações do Ano , Sulfatos/análise , Água/química
20.
ACS Appl Mater Interfaces ; 10(46): 39679-39687, 2018 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-30365889

RESUMO

Development of a high-efficiency heterojunction with an improved photocatalytic property is regarded as a promising way to decontaminate wastewater. Herein, the direct novel Z-scheme heterojunction formed between CeO2 nanoparticles and hierarchical ZnO was synthesized through the wet chemistry method and then the heat-treatment technique. The as-synthesized ZnO/CeO2 composites display highly enhanced photocatalytic rhodamine B (RhB) degradation compared with pristine ZnO and CeO2. Specifically, ZnO/CeO2-3 (mass fraction of CeO2, 30%) shows good photostability and the best removal efficiency for photodegradated RhB, which are almost 2.5 and 1.7 times than pristine ZnO and CeO2, respectively. On the basis of the detailed characterizations and the degradation behavior of as-prepared samples over RhB, the formed heterojunction between the hierarchical ZnO and CeO2 nanoparticles is confirmed as the direct Z-scheme heterojunction. The heterojunction system shows fast transfer, high-efficiency separation, and long lifetime of photoinduced charge carriers, as well as enhanced redox capacity. This study affords a novel approach to construct ZnO-based Z-scheme heterojunctions for the photocatalytic applications.

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