Performance Evaluation of an Improved Particle Size Magnifier (PSM) for Single Nanoparticle Detection

183

186

The effect of working fluid on size-dependent activation efficiencies with the laminar flow ultrafine condensation particle counter described by Stolzenburg and McMurry (1991) was studied theoretically and experimentally. Criteria considered include tendency to avoid homogeneous nucleation within the condenser and toxicity. The working fluids that were identified have vapor pressures below that of butanol, so particles grow to smaller sizes and are more difficult to detect optically. Therefore we use a second, conventional CPC as a "booster" to grow particles to a detectable size. Experiments were performed to obtain the size-and material-dependent activation efficiencies for ethylene glycol, diethylene glycol, propylene glycol, oleic acid, and DOS. Using diethylene glycol and oleic acid, values of the 50% activation efficiency diameter, D p50 , for negatively charged particles generated by evaporating sodium chloride, ammonium sulfate, and silver were <1.2 (<0.8) nm , 1.4-1.5 (1.0-1.2) nm, and 1.9-2.0 (1.5) nm as mobility (mass) diameter, respectively. The stability of the UCPC for long-term operation using ethylene glycol and propylene glycol as working fluids was tested by monitoring the instrument's response to silver particles having size near D p50 in an air stream at 40-45% relative humidity. The performance was steady (±3%) for several days indicating the instrument performs stably during unattended operation for realistic atmospheric sampling conditions.

Section: Resultssupporting

confidence: 82%

Section: Activation Efficiencymentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

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Effect of Working Fluid on Sub-2 nm Particle Detection with a Laminar Flow Ultrafine Condensation Particle Counter

Iida

Stolzenburg

McMurry

2009

183

186

“…He used diethylene glygol or oleic acid vapor to activate the particles and magnify their size so that they were detectable with an ordinary butanol CPC. Very low cut-sizes are reported also for mixing type CPCs (Okuyama et al 1984;Seto et al 1997; Gamero-Gastaño and Fernández de la Mora 2002; Kim et al 2003;Sgro and Fernández de la Mora 2004). For example the mixing type CPC-or "particle size magnifier"-of Seto et al (1997) was able to activate and grow singly charged ions down to approximately 1 nm in diameter.…”

Section: Introductionmentioning

confidence: 99%

Laboratory Verification of PH-CPC's Ability to Monitor Atmospheric Sub-3 nm Clusters

Sipilä

Lehtipalo

Attoui

et al. 2009

Gas-to-particle conversion takes readily place in the atmosphere. Detecting the initial clusters, which act as embryos for the newly formed particles, is beyond traditional aerosol instrumentation. Charged atmospheric clusters can be measured with air ion spectrometers, but typical state-of-the-art condensation particle counters, which detect both neutral and charged clusters, only see particles larger than 2.5 nm in diameter. In this study we present a modified pulse-height condensation particle counter (PH-CPC) and confirm by laboratory verification that it is capable of detecting charged clusters with electrical mobility equivalent diameter down to ∼1 nm. We show how the detection efficiency and the pulse heights depend on the calibration particle size, polarity and composition. The effect of butanol supersaturation on the PH-CPC counting efficiency is also discussed. Furthermore, we developed an inversion method for the data to obtain true particle size distribution from the measurement signal.

“…A recent progress in the field of atmospheric aerosol science, especially in understanding of the new particle formation (Kulmala et al 2004), as well as the bloom of nanoscience and -technology have created a need to develop CPCs for detection of smaller and smaller particles. Mixing type particle size magnifiers (PSM) developed by Gamero-Castaño and Fernandez de la Mora (2000), Kim et al (2000), and Sgro and Fernández de la Mora (2004) has shown a superior performance in the sub-3nm size range. However, no reports on their applicability in, e.g., atmospheric studies exist.…”

Section: Introductionmentioning

confidence: 99%

Particle Size Magnifier for Nano-CN Detection

Vanhanen

Mikkilä

Lehtipalo

et al. 2011

323

291

A new particle size magnifier (PSM) for detection of nano-CN as small as ∼1 nm in mobility diameter was developed, calibrated and tested in atmospheric measurements. The working principle of a PSM is to mix turbulently cooled sample flow with heated clean air flow saturated by the working fluid. This provides a high saturation ratio for the working fluid and activates the seed particles and grows them by condensation of the working fluid. In order to reach high saturation ratios, and thus to activate nano-CN without homogeneous nucleation, diethylene glycol was chosen as the working fluid. The PSM was able to grow nano-CN to mean diameter of 90 nm, after which an ordinary condensation particle counter was used to count the grown particles (TSI 3010). The stability of the PSM was found to be good making it suitable for stand-alone field measurements. Calibration results show that the detection efficiency of the prototype PSM + TSI 3010 for charged tetra-alkyl ammonium salt molecules having mobility equivalent diameters of 1.05, 1.47, 1.78, and 2.57 nm are 25, 32, 46, and 70%, respectively. The commercial version of the PSM (Airmodus A09) performed even better in the smallest sizes the detection efficiency being 51% for 1.47 nm and 67% for 1.78 nm.