Concomitant with the development of polymer nanocomposite (PNC) technologies across numerous industries is an expanding awareness of the uncertainty with which engineered nanoparticles embedded within these materials may be released into the external environment, particularly liquid media. Recently there has been an interest to evaluate potential exposure to nanoscale fillers from PNCs, but existing studies often rely upon uncharacterized, poor quality, or proprietary materials, creating a barrier to making general conclusions about the impact of factors, such as particle size, on release phenomena. In this study we employed semiconductor nanoparticles (quantum dots, QDs) as model nanofillers to quantify potential release into liquid media under specific environmental conditions. QDs of two sizes were incorporated into low-density polyethylene by melt compounding and the mixtures were extruded as free-standing fluorescent films. These films were subjected to tests under conditions intended to simulate a worst case scenario for environmental release. Using inductively-coupled plasma mass spectrometry and laser scanning confocal microscopy, it was found that the acidity of the external medium, exposure time, and particle size all play pivotal roles in release kinetics, and the primary mechanism for release is diffusion of ions dissolved from the surfaces of embedded particles. This is one of the first studies that demonstrate an explicit relationship between release rate and particle size. Additionally, this study provides an experimentally-derived upper limit on the diffusion rate of nanoparticles throughout a polymer matrix, thus refining our understanding of the potential exposure to nanoparticles from PNCs in consumer products.
Citation: Environmental Science Nano
Pub Type: Journals
consumer products, environmental health and safety, exposure, nanocomposites, release, quantum dots