Simultaneous Insight into Dissolution and Aggregation of Metal Sulfide Nanoparticles through Single-Particle Inductively Coupled Plasma Mass Spectrometry

Abstract

Nanoparticles (NPs) and their colloidal aggregates are ubiquitous and play important roles in the transport and release of metals. Knowledge of their dissolution rates and aggregation behavior in solution are crucial for better prediction of their fate in biogeochemical cycling, ecotoxicity, and environmental remediation. There are however significant technical challenges to accurately obtain such information as a result of the heterogeneity and highly dynamic transformation exhibited by NPs, particularly at relatively low particle concentrations in aqueous systems. Here, we quantitatively examine the simultaneous dissolution and aggregation behavior of metal sulfide NPs using single-particle inductively coupled plasma mass spectrometry (spICP–MS). We focus on nickel sulfide (NiS), with additional data presented for copper sulfide (CuS) and cobalt sulfide (CoS). The kinetics of metal release (dissolution and disaggregation) of NiS was fastest under strongly oxidizing conditions (from 0.04 to >3 min–1 with H2O2 ) and were slower under near-neutral (HEPES buffer/H2O) and acidic (1 mM HNO3) conditions (≤0.006 min–1). Metal release kinetics in HNO3 was not faster than in H2O or HEPES, suggesting that the solution pH has an influence over both the dissolution kinetics of individual particles and the NP aggregation states, which in combination affect metal release rates over time. Between different metal sulfides, the measured metal release rates were largely consistent with predictions based on the crystallinity, solubility products, and specific surface areas of the NPs, following an order of CoS > NiS > CuS. The spICP–MS approach described here can be easily applied to the characterization of metal release and aggregation of other NPs at low concentrations (∼105 particles/mL) typically found in natural environments.

Application of Isotopically Labeled Engineered Nanomaterials for Detection and Quantification in Soils via Single-Particle Inductively Coupled Plasma Time-of-Flight Mass Spectrometry

“…This is a known limitation of the spICP-TOF-MS method. 44 DLS measurement further confirms that some aggregation of particles is occurring as the particles detected have a hydrodynamic size (number average) of 114 ± 55 nm for TiO 2 NPs. The polydispersity index was too high to report a reliable value for the CuO NPs.…”

“…The larger sizes measured by spICP-TOF-MS are most likely due to aggregation of ENMs in suspension and the detection limit preventing measurement of the smallest particles present in the suspension. This is a known limitation of the spICP-TOF-MS method . DLS measurement further confirms that some aggregation of particles is occurring as the particles detected have a hydrodynamic size (number average) of 114 ± 55 nm for TiO 2 NPs.…”

Characterization of nano-scale mineral dust aerosols in snow by single particle inductively coupled plasma mass spectrometry

“…Differences between such PSDs have been used to examine particle transformation processes. 21,40 However, in a natural sample where particle characteristics are unknown, differences in PSDs between samples are possibly artifactual, necessitating a more rigorous treatment of the data.…”

“…With appropriate data processing, widely available quadrupole mass spectrometry (QMS) can provide PSDs for individual elements. 21 Recent developments in ICP-time-offlight mass spectrometry (TOFMS) have made it possible to quantify more than one element in individual particles. 22,23 Both spICP-QMS and spICP-TOFMS have been used to characterize NPs in precipitation, but studies have been limited to proof of concept, concluding that spICP-MS is suitable for this analysis.…”

Virtual Special Issue of ACS Earth and Space Chemistry in Honor of Prof. Michael F. Hochella, Jr.

“…In addition, the three Hochella Symposium organizers were invited by Prof. Joel Blum, Editor-in-Chief of ACS Earth and Space Chemistry , to organize and serve as Guest Editors of a virtual special issue of this journal in honor of Mike Hochella. A total of 20 peer-reviewed manuscripts were accepted for publication in this virtual special issue (), with topics ranging from mineral/water interface chemistry and mineral/organic matter nanoparticles to organic matter/soil chemistry and microbial geochemistry studies. − These papers highlight the importance of nanogeoscience, mineral/aqueous solution interface chemistry, biogeochemistry, and organic matter/soil chemistry in understanding the Earth system.…”