Counting on Chemistry: Laboratory Evaluation of Seed Material-Dependent Detection Efficiencies of Ultrafine Condensation Particle Counters

Wlasits, Peter Josef; Stolzenburg, Dominik; Tauber, Christian; Brilke, Sophia; Schmitt, Sebastian; Winkler, Paul M.; Wimmer, Daniela

doi:10.5194/amt-2019-486

Cited by 5 publications

(9 citation statements)

References 29 publications

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“…As a sanity check of our approach, we first tested that butanol does not homogeneously nucleate under typical CPC conditions: a temperature of 10–25 °C and a butanol saturation ratio of 1–5. 10 , 69 In agreement with experiments, and with classical thermodynamic predictions, our modeling indicates negligible rates for homogeneous nucleation in these conditions.…”

Section: Discussionsupporting

confidence: 87%

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Heterogeneous Nucleation of Butanol on NaCl: A Computational Study of Temperature, Humidity, Seed Charge, and Seed Size Effects

et al. 2021

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Using a combination of quantum chemistry and cluster size distribution dynamics, we study the heterogeneous nucleation of n -butanol and water onto sodium chloride (NaCl) 10 seeds at different butanol saturation ratios and relative humidities. We also investigate how the heterogeneous nucleation of butanol is affected by the seed size through comparing (NaCl) 5 , (NaCl) 10 , and (NaCl) 25 seeds and by seed electrical charge through comparing (Na 10 Cl 9 ) + , (NaCl) 10 , and (Na 9 Cl 10 ) − seeds. Butanol is a common working fluid for condensation particle counters used in atmospheric aerosol studies, and NaCl seeds are frequently used for calibration purposes and as model systems, for example, sea spray aerosol. In general, our simulations reproduce the experimentally observed trends for the NaCl–BuOH–H 2 O system, such as the increase of nucleation rate with relative humidity and with temperature (at constant supersaturation of butanol). Our results also provide molecular-level insights into the vapor–seed interactions driving the first steps of the heterogeneous nucleation process. The main purpose of this work is to show that theoretical studies can provide molecular understanding of initial steps of heterogeneous nucleation and that it is possible to find cost-effective yet accurate-enough combinations of methods for configurational sampling and energy evaluation to successfully model heterogeneous nucleation of multicomponent systems. In the future, we anticipate that such simulations can also be extended to chemically more complex seeds.

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Section: Discussionsupporting

confidence: 87%

“…The typical experimental nucleation temperature in CPCs ranges between 10 and 25 °C, and the butanol saturation ratio ranges from 1 to 5 (the butanol saturation vapor pressure at 25 °C is 919.2 Pa). 10 , 69 …”

Section: Resultsmentioning

confidence: 99%

Heterogeneous Nucleation of Butanol on NaCl: A Computational Study of Temperature, Humidity, Seed Charge, and Seed Size Effects

et al. 2021

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“…This observation is consistent with a previous study (Hering et al, 2017). One possible explanation is that the chemical similarity between the seed particle material and the working fluid also affects the detection efficiency of the vWCPC 3789 (Wlasits et al, 2020).…”

Section: Effect Of Particle Chemical Composition On the Vwcpc 3789 Counting Efficiencysupporting

confidence: 93%

“…Thus, both settings are suitable for airborne operations up to 5.5 km with a 7 nm cut-off size. Note that the counting efficiency curve from TSI at 30 • was derived and fitted using an AS particle classified by a custommade different mobility analyzer (using an aerosol-to-sheath flow rate ratio of 1 : 100) under a near-sea-level pressure (Wlasits et al, 2020). As a result of operation over a much wider pressure range, the cut-off curve derived by this study is less sharp than for the TSI standard settings.…”

Section: Temperature Dependence Of the Vwcpc 3789 Cut-off Sizementioning

confidence: 88%

Simulation-aided characterization of a versatile water-based condensation particle counter for atmospheric airborne research

et al. 2021

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Abstract. Capturing the vertical profiles and horizontal variations of atmospheric aerosols often requires accurate airborne measurements. With the advantage of avoiding health and safety concerns related to the use of butanol or other chemicals, water-based condensation particle counters have emerged to provide measurements under various environments. However, airborne deployments are relatively rare due to the lack of instrument characterization under reduced pressure at flight altitudes. This study investigates the performance of a commercial “versatile” water-based condensation particle counter (vWCPC, model 3789, TSI, Shoreview, MN, USA) under various ambient pressure conditions (500–920 hPa) with a wide range of particle total number concentrations (1500–70 000 cm−3). The effect of conditioner temperature on vWCPC 3789 performance at low pressure is examined through numerical simulation and laboratory experiments. We show that the default instrument temperature setting of 30 ∘C for the conditioner is not suitable for airborne measurement and that the optimal conditioner temperature for low-pressure operation is 27∘. Under the optimal conditioner temperature (27∘), the 7 nm cut-off size is also maintained. Additionally, we show that insufficient droplet growth becomes more significant under the low-pressure operation. The counting efficiency of the vWCPC 3789 can vary up to 20 % for particles of different chemical compositions (e.g., ammonium sulfate and sucrose particles). However, such variation is independent of pressure.

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“…The general characteristic of a CPC is its detection efficiency curve: heterogeneous nucleation probability of the sample particles as a function of particle size. Typically, the most important parameter considered to determine heterogeneous nucleation probability is particle size (lower nucleation probability for smaller particles), while several studies have demonstrated that chemical interactions between the particles and the condensing vapor affect strongly the nucleation probability at constant particle size [12][13][14][15][16] . Uncertainty in the detection efficiency curve results in uncertainty in the measured nanoparticle concentrations, especially in systems where secondary particle formation takes place and this deteriorates the accuracy of the inferred aerosol dynamics.…”

Section: Introductionmentioning

confidence: 99%

Seed–Adsorbate Interactions as the Key of Heterogeneous Butanol and Diethylene Glycol Nucleation on Ammonium Bisulfate and Tetramethylammonium Bromide

et al. 2020

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Condensation particle counter (CPC) instruments are commonly used to detect atmospheric nanoparticles. They operate on the basis of condensing an organic working fluid on the nanoparticle seeds to grow the particles to a detectable size, and at the size of few nanometers, their efficiency depends on how well the working fluid interacts with the seeds under the measurement conditions. This study models the first steps of heterogeneous nucleation of two working fluids commonly used in CPCs (diethylene glycol (DEG) and n-butanol) onto two positively charged seeds, ammonium bisulfate and tetramethylammonium bromide. The nucleation process is modeled on a molecular level using a combination of systematic configurational sampling and density functional theory (DFT). We take into account the conformational flexibility of DEG and n-butanol and determine the key factors that can improve the efficiency of nanoparticle measurements by CPCs. The results show that hydrogen bonding between the seed and the working fluid molecules is central to the adsorption of the first DEG/n-butanol molecules onto the seeds. However, intermolecular hydrogen bonding between the adsorbed molecules can also enhance the nucleation process for the weakly adsorbing vapor molecules. Accordingly, the heterogeneous nucleation probability is higher for working fluid−nanoparticle combinations with a higher potential for hydrogen bonding; in this case, DEG and ammonium bisulfate. Moreover, conformational analysis and methodology evaluations indicate that the consideration of adsorbate conformers and step-wise addition of the vapor molecules to the seeds is not essential for qualitative modeling of heterogeneous nucleation systems, at least for systems where the adsorbate and seed chemical properties are clearly different. This is the first molecular-level modeling study reporting detailed chemical reasons for experimentally observed seed and working fluid preferences in CPCs and reproducing the experimental observations. Our presented approach can be likely used for predicting preferences in similar nucleating systems.

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Counting on Chemistry: Laboratory Evaluation of Seed Material-Dependent Detection Efficiencies of Ultrafine Condensation Particle Counters

Cited by 5 publications

References 29 publications

Heterogeneous Nucleation of Butanol on NaCl: A Computational Study of Temperature, Humidity, Seed Charge, and Seed Size Effects

Heterogeneous Nucleation of Butanol on NaCl: A Computational Study of Temperature, Humidity, Seed Charge, and Seed Size Effects

Simulation-aided characterization of a versatile water-based condensation particle counter for atmospheric airborne research

Seed–Adsorbate Interactions as the Key of Heterogeneous Butanol and Diethylene Glycol Nucleation on Ammonium Bisulfate and Tetramethylammonium Bromide

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