Gold core-labeled TiO2 nanoparticles for tracking behavior in complex matrices: synthesis, characterization, and demonstration

Abstract

Titanium dioxide nanoparticles (TiO₂ NPs) are increasingly entering natural systems due to their widespread production and use. It is critical that TiO₂ NP behavior is studied in real-world systems, but experimental work is complicated by the high levels of background titanium present in every environmental compartment. To assist in distinguishing between engineered NPs and background titanium, labeled particles with gold nanoparticle cores and TiO₂ shells (Au@TiO₂ NPs) were developed and the properties and behavior compared to unlabeled TiO₂ NPs. Both particle types had primary particle diameters of approximately 200 nm and were stable in solutions at ionic strengths up to 500 mM due to a polyvinylpyrrolidone surface coating. To demonstrate utility, the Au@TiO₂ NPs were used in several spike-and-recovery experiments in complex matrices such as activated sludge and a river water–sunscreen mixture. Au@TiO₂ NPs were accurately quantified at using instrumental neutron activation analysis and inductively coupled plasma optical emission spectrometry.