Generation of ZnO nanoparticles for long-term exposure experiments

Abstract

A method of continual ZnO nanoparticle (NP) generation was tested for use in follow-up long-term inhalation exposure experiments with small laboratory animals. NPs were synthesized in an externally heated tube reactor by the evaporation of metallic zinc into a stream of nitrogen carrier gas, followed by the oxidation of zinc vapor in a stream of air and the formation of NPs by a chemical vapor condensation method. The NP production was studied at various evaporation temperatures, reactor flow rates and flow rates of mixing air. Particle generation for more than 100 h in two experimental runs with one batch of the zinc precursor was performed without a considerable decrease in the particle production rate. As a result, particle production with a number concentration much greater than 1.0 × 10 7 #/cm 3 , a mean particle/agglomerate size well below 50 nm and an emission rate greater than 5 μg/min was obtained under most of the investigated experimental conditions. A maximum emission rate of 16.3 μg/min was obtained at an evaporation temperature of 530 °C, a reactor flow rate of 800 cm 3 /min and a mixing flow rate of 2000 cm 3 /min and could be further increased by an increase in the evaporation temperature. The particle characteristics were studied, and estimates of the lung surface deposition area were calculated on the basis of the model developed by the International Commission of Radiological Protection. Copyright © 2019 American Association for Aerosol Research.