Ambient air sampling during quantum-dot spray deposition

Ambient air sampling for nanosize particle emissions was performed during spot spray coating with a Sono-Tek ExactaCoat Benchtop system (ECB). Cadmium selenide quantum dots (QDs) and gold QDs, nominally 3.3 and 5 nm in diameter respectively, were applied during the evaluation. Median spray drop size was in the 20 to 60 micrometer size range. Industrial hygiene monitoring and evaluation of controls were revised when a scanning mobility particle sizer indicated a significant increase in the ambient air concentration upon early enclosure door-opening. A time delay sufficient to provide 10 enclosure air changes (a concentration reduction of more than 99.99%) before door-opening prevented the release of aerosol particles in any measurable size. As part of the evaluation, aerosol characterization in reference to background was made using condensation particle counters, atomic force and electron microscopy, and chemical analysis.