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- Baker, Yare, et al.
(författare)
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Impact of HO2/RO2 ratio on highly oxygenated α-pinene photooxidation products and secondary organic aerosol formation potential
- 2024
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Ingår i: ATMOSPHERIC CHEMISTRY AND PHYSICS. - 1680-7316 .- 1680-7324. ; 24:8, s. 4789-4807
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Tidskriftsartikel (refereegranskat)abstract
- Highly oxygenated molecules (HOMs) from the atmospheric oxidation of biogenic volatile organic compounds are important contributors to secondary organic aerosol (SOA). Organic peroxy radicals (RO2) and hydroperoxy radicals (HO2) are key species influencing the HOM product distribution. In laboratory studies, experimental requirements often result in overemphasis on RO2 cross-reactions compared to reactions of RO2 with HO2. We analyzed the photochemical formation of HOMs from alpha-pinene and their potential to contribute to SOA formation under high (approximate to 1/1) and low (approximate to 1/100) conditions. As > 1 is prevalent in the daytime atmosphere, sufficiently high is crucial to mimic atmospheric conditions and to prevent biases by low on the HOM product distribution and thus SOA yield. Experiments were performed under steady-state conditions in the new, continuously stirred tank reactor SAPHIR-STAR at Forschungszentrum J & uuml;lich. The ratio was increased by adding CO while keeping the OH concentration constant. We determined the HOM's SOA formation potential, considering its fraction remaining in the gas phase after seeding with (NH4)(2)SO4 aerosol. An increase in led to a reduction in SOA formation potential, with the main driver being a similar to 60 % reduction in HOM-accretion products. We also observed a shift in HOM-monomer functionalization from carbonyl to hydroperoxide groups. We determined a reduction of the HOM's SOA formation potential by similar to 30 % at approximate to 1/1 compared to approximate to 1/100. Particle-phase observations measured a similar decrease in SOA mass and yield. Our study shows that too low ratios compared to the atmosphere can lead to an overestimation of SOA yields.
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| 2. |
- Yin, Mingjie, et al.
(författare)
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Highly sensitive and fast responsive fiber-optic modal interferometric pH sensor based on polyelectrolyte complex and polyelectrolyte self-assembled nanocoating
- 2011
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 399:10, s. 3623-3631
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Tidskriftsartikel (refereegranskat)abstract
- A new fiber-optic pH sensor is demonstrated by coating negatively charged polyelectrolyte complex (PEC-) nanoparticles, made of sodium carboxymethyl cellulose and poly(diallyldimethylammonium chloride) (PDDA), and positively charged PDDA on the surface of a thin-core fiber modal interferometer (TCFMI) with a layer-by-layer (LbL) electrostatic self-assembly method. The fabricated TCFMI pH sensor has different transmission dip wavelengths under different pH values and shows high sensitivities of 0.6 nm/pH unit and -0.85 nm/pH unit for acidic and alkaline solutions, respectively, and short response time of 30-50 s. The LbL electrostatic self-assembly process of a PEC-/PDDA multilayer is traced by quartz crystal microbalance and shows a fast thickness growth. Atomic force microscopy shows the root mean square (RMS) surface roughness of electrostatic self-assembly nanocoating of polyelectrolyte complex/polyelectrolyte is much higher than that of polyelectrolyte/polyelectrolyte due to the larger size of PEC- colloidal nanoparticles. The enhanced RMS surface roughness and thickness of the nanocoating can shorten the response time and raise the sensitivity of the TCFMI pH sensor, respectively. In addition, the TCFMI pH sensor has highly reversible performance and good durability.
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