title: Prospecting nanomaterials in aqueous environments by cloud-point extraction coupled with transmission electron microscopy.
abstract: Increasing application of engineered nanomaterials (ENMs) in industry and consumer products inevitably lead to their release into and impact on aquatic environments. To characterize the NMs efficiently in surface water, a fast and simple method is needed to separate and concentrate nanomaterials from the aqueous matrix without altering their shape and size. Applying cloud-point extraction (CPE) using the surfactant Triton 114 to an array of NMs (titanium dioxide, gold, silver, and silicon dioxide) with different sizes or capping agents in nanopure water resulted in extraction efficiency of 83%-107%. Additional CPE experiments were conducted to extract NMs from surface, potable, and sewage waters, and NMs enriched in the surfactant phase were characterized using transmission electron microscopy coupled with energy dispersive x-ray spectroscopy. The most abundant nanoparticles identified in surface water were silica, titanium dioxide, and iron oxide with 4-99nm diameter. The extraction efficiencies of CPE for silicon, titanium, and iron elements from environmental water samples were 51%, 15%, and 99%, respectively. This study applied CPE with TEM to enrich and analyze popular nanoparticles such as SiO2and TiO2from natural waters, which has not been well addressed by previous researches. Overall, CPE coupled with transmission electron microscopy (TEM) can be an effective method to characterize NMs in aqueous water samples, and further optimization will increase the extraction efficiency of NMs in complicated surface water matrix.
authors.affiliation: School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287-3005, United States.
authors.forename: Yu
authors.initials: Y
authors.lastname: Yang
authors.affiliation: School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287-3005, United States.
authors.forename: Robert
authors.initials: R
authors.lastname: Reed
authors.affiliation: School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ 85287-6106, United States.
authors.forename: Jared
authors.initials: J
authors.lastname: Schoepf
authors.affiliation: The Polytechnic School, Arizona State University, Mesa, AZ 85212, United States.
authors.forename: Kiril
authors.initials: K
authors.lastname: Hristovski
authors.affiliation: School of Molecular Sciences, Arizona State University, Tempe, AZ 85287-1604, United States.
authors.forename: Pierre
authors.initials: P
authors.lastname: Herckes
authors.affiliation: School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287-3005, United States. Electronic address: p.westerhoff@asu.edu.
authors.forename: Paul
authors.initials: P
authors.lastname: Westerhoff
keywords: Cloud-point extraction; Exposure; Nanomaterial; Water