Electrospinning and Electrospun Nanofibers: Methods, Materials, and Applications

Chemical Reviews, Journal Year: 2019, Volume and Issue: 119(8), P. 5298 - 5415

Published: March 27, 2019

Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods engineering electrospun nanofibers suit or enable various applications. We aim provide comprehensive overview electrospinning, including principle, methods, materials, begin brief introduction early history followed by discussion its principle typical apparatus. then discuss renaissance over past two decades as powerful technology production diversified compositions, structures, properties. Afterward, we applications nanofibers, their use "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, photonic electronic devices, well biomedical scaffolds. highlight most relevant recent advances related focusing on representative examples. also offer perspectives challenges, opportunities, new directions future development. At end, approaches scale-up briefly types commercial products based that have found widespread in our everyday life.

Language: Английский

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Severe haze in northern China: A synergy of anthropogenic emissions and atmospheric processes

Proceedings of the National Academy of Sciences, Journal Year: 2019, Volume and Issue: 116(18), P. 8657 - 8666

Published: April 15, 2019

Significance Severe haze events with large temporal/spatial coverages have occurred frequently in wintertime northern China. These extremes result from a complex interplay between emissions and atmospheric processes provide unique scientific platform to gain insights into many aspects of the relevant chemistry physics. Here we synthesize recent progress understanding severe formation In particular, highlight that improved emission sources, physical/chemical during evolution, interactions meteorological/climatic changes are necessary unravel causes, mechanisms, trends for pollution. This viewpoint established on basis sound science is critical improving prediction/forecast, formulating effective regulatory policies by decision makers, raising public awareness environmental protection.

Language: Английский

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Atmospheric new particle formation and growth: review of field observations

Environmental Research Letters, Journal Year: 2018, Volume and Issue: 13(10), P. 103003 - 103003

Published: Sept. 6, 2018

This review focuses on the observed characteristics of atmospheric new particle formation (NPF) in different environments global troposphere. After a short introduction, we will present theoretical background that discusses methods used to analyze measurement data NPF and associated terminology. We update our current understanding regional NPF, i.e. taking simultaneously place over large spatial scales, complement with full reported growth rates during events. shortly at sub-regional scales. Since newly-formed particles into larger sizes is great interest, briefly discuss observation-based which gaseous compounds contribute particles, what implications this have cloud condensation nuclei formation. finish summary main findings future outlook outlines remaining research questions needs for additional measurements.

Language: Английский

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New Particle Formation in the Atmosphere: From Molecular Clusters to Global Climate

Journal of Geophysical Research Atmospheres, Journal Year: 2019, Volume and Issue: 124(13), P. 7098 - 7146

Published: June 25, 2019

Abstract New particle formation (NPF) represents the first step in complex processes leading to of cloud condensation nuclei. Newly formed nanoparticles affect human health, air quality, weather, and climate. This review provides a brief history, synthesizes recent significant progresses, outlines challenges future directions for research relevant NPF. developments include emergence state‐of‐the‐art instruments that measure prenucleation clusters newly nucleated down about 1 nm; systematic laboratory studies multicomponent nucleation systems, including collaborative experiments conducted Cosmics Leaving Outdoor Droplets chamber at CERN; observations NPF different types forests, extremely polluted urban locations, coastal sites, polar regions, high‐elevation sites; improved theories parameterizations account atmospheric models. The lack understanding fundamental chemical mechanisms responsible aerosol growth under diverse environments, effects SO 2 NO x on NPF, contribution anthropogenic organic compounds It is also critical develop can detect composition particles from 3 20 nm improve represent over wide range conditions precursor, temperature, humidity.

Language: Английский

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Rapid growth of new atmospheric particles by nitric acid and ammonia condensation

Nature, Journal Year: 2020, Volume and Issue: 581(7807), P. 184 - 189

Published: May 13, 2020

A list of authors and their affiliations appears at the end paper New-particle formation is a major contributor to urban smog1,2, but how it occurs in cities often puzzling3. If growth rates particles are similar those found cleaner environments (1-10 nanometres per hour), then existing understanding suggests that new should be rapidly scavenged by high concentration pre-existing particles. Here we show, through experiments performed under atmospheric conditions CLOUD chamber CERN, below about +5 degrees Celsius, nitric acid ammonia vapours can condense onto freshly nucleated as small few diameter. Moreover, when cold enough (below -15 Celsius), nucleate directly an acid-base stabilization mechanism form ammonium nitrate Given these one thousand times more abundant than sulfuric acid, resulting particle extremely high, reaching well above 100 hour. However, require gas-particle system out equilibrium order sustain gas-phase supersaturations. In view strong temperature dependence measure for supersaturations, expect such transient occur inhomogeneous settings, especially wintertime, driven vertical mixing local sources traffic. Even though rapid from condensation may last only minutes, nonetheless fast shepherd smallest size range where they most vulnerable scavenging loss, thus greatly increasing survival probability. We also nucleation important relatively clean upper free troposphere, convected continental boundary layer electrical storms4,5.

Language: Английский

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Puzzling Haze Events in China During the Coronavirus (COVID‐19) Shutdown

Geophysical Research Letters, Journal Year: 2020, Volume and Issue: 47(12)

Published: June 10, 2020

It is a puzzle as to why more severe haze formed during the New Year Holiday in 2020 (NYH-20), when China was an unprecedented state of shutdown contain coronavirus (COVID-19) outbreak, than 2019 (NYH-19). We performed comprehensive measurement and modeling analysis aerosol chemistry physics at multiple sites (mainly Shanghai) before, during, after NYH-19 NYH-20. Much higher secondary fraction PM2.5 were observed NYH-20 (73%) (59%). During NYH-20, levels correlated significantly with oxidation ratio nitrogen (r2 = 0.77, p < 0.01), aged particles from northern found impede atmospheric new particle formation growth Shanghai. A markedly enhanced efficiency nitrate along transport pathways despite overall low NO2 levels.

Language: Английский

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Remarkable nucleation and growth of ultrafine particles from vehicular exhaust

Proceedings of the National Academy of Sciences, Journal Year: 2020, Volume and Issue: 117(7), P. 3427 - 3432

Published: Feb. 3, 2020

High levels of ultrafine particles (UFPs; diameter less than 50 nm) are frequently produced from new particle formation under urban conditions, with profound implications on human health, weather, and climate. However, the fundamental mechanisms remain elusive, few experimental studies have realistically replicated relevant atmospheric conditions. Previous simulated oxidation one compound or a mixture compounds, extrapolation laboratory results to chemically complex air was uncertain. Here, we show striking UFPs in combining ambient chamber measurements. By capturing conditions (i.e., temperature, relative humidity, sunlight, types abundances chemical species), elucidate roles existing particles, photochemistry, synergy multipollutants formation. Aerosol nucleation is limited by but negligibly nitrogen oxides. Photooxidation vehicular exhaust yields abundant precursors, organics, rather sulfuric acid base species, dominate Recognition this source essential assessing their impacts developing mitigation policies. Our imply that reduction primary removal without simultaneously limiting organics automobile emissions ineffective can even exacerbate problem.

Language: Английский

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Seasonal Characteristics of New Particle Formation and Growth in Urban Beijing

Environmental Science & Technology, Journal Year: 2020, Volume and Issue: 54(14), P. 8547 - 8557

Published: July 1, 2020

Understanding the atmospheric new particle formation (NPF) process within global range is important for revealing budget of aerosols and their impacts. We investigated seasonal characteristics NPF in urban environment Beijing. Aerosol size distributions down to ∼1 nm H2SO4 concentration were measured during 2018–2019. The observed rate 1.5 particles (J1.5) significantly higher than those clean environment, e.g., Hyytiälä, whereas growth not different. Both J1.5 frequency Beijing show a clear variation with maxima winter minima summer, while rates are generally same around year. that ambient temperature governing factor driving J1.5. In contrast, condensation sink daily maximum no significant periods. all four seasons, (H2SO4)n(amine)n clusters contributes sub-3 range, it less above 3 nm. Therefore, other species always needed larger particles.

Language: Английский

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Is reducing new particle formation a plausible solution to mitigate particulate air pollution in Beijing and other Chinese megacities?

Faraday Discussions, Journal Year: 2020, Volume and Issue: 226, P. 334 - 347

Published: Aug. 26, 2020

Atmospheric gas-to-particle conversion is a crucial or even dominant contributor to haze formation in Chinese megacities terms of aerosol number, surface area and mass. Based on our comprehensive observations Beijing during 15 January 2018-31 March 2019, we are able show that 80-90% the mass (PM2.5) was formed via atmospheric reactions days over 65% number concentration particles resulted from new particle (NPF). Furthermore, faster when subsequent growth newly enhanced. Our findings suggest practice almost all present-day episodes originate NPF, mainly since direct emission primary has considerably decreased recent years. We also reducing rate freshly by factor 3-5 would delay buildup 1-3 days. Actually, this decrease length each episode, so annual could be approximately halved. Such improvement air quality can achieved with targeted reduction gas-phase precursors for dimethyl amine ammonia, further reductions SO2 emissions. anthropogenic organic inorganic precursor emissions slow down newly-formed consequently reduce formation.

Language: Английский

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PM2.5 and O3 pollution during 2015–2019 over 367 Chinese cities: Spatiotemporal variations, meteorological and topographical impacts

Environmental Pollution, Journal Year: 2020, Volume and Issue: 264, P. 114694 - 114694

Published: May 5, 2020

Language: Английский

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