The History of Condensation Nucleus Counters

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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: Introductionmentioning

confidence: 99%

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

Iida

Stolzenburg

McMurry

2009

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“…Growth by condensation is the most appropriate technique for detecting neutral gas-borne particles that are too small to be sensed optically (McMurry 2000). Therefore, condensation nucleus counters (CNCs) are the most commonly used to measure the number concentration as nanoparticle detector currently.…”

Section: Introductionmentioning

confidence: 99%

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

Kim

Okuyama

Mora

2003

Several modifications of the particle size magnifier (PSM) developed by Okuyama et al. have been introduced recently for detection of particles at diameters of 1 nm and below. However, their evaluation has been incomplete. Here we provide the first direct measurements of counting efficiencies near unity below 2 nm. We use the modified PSM described by Sgro and Fernández de la Mora, which separates thermally the PSM's original vapor generator from the water-cooled growth chamber by means of a narrow and short T where turbulent mixing with the aerosol takes place. The counting efficiency is seen to depend greatly on the aerosol flow, the amount of vapor, and temperature. With ethylene glycol vapor, under optimal conditions, the counting efficiency is 100% down to 1.6 nm (actual diameter of 1.2 nm), and negative particles are more easily activated than positive particles. The improved PSM is applied to the measurement of gold nanoparticle size distributions, and the results show it is a powerful aerosol detector for nanoparticles.

“…Operation principles and main specifications of different types of CPCs have been reviewed by McMurry (2000). Cut-size is a parameter, which describes the particle detection efficiency of a CPC.…”

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.