Design and Evaluation of a High-Flowrate Nanoparticle Respiratory Deposition (NRD) Sampler.

A high-flow (10 L/min) nanoparticle respiratory deposition (NRD) sampler was designed and evaluated to achieve reduced limits of quantification (LOQs) for metal nanoparticles. The high-flow NRD consists of an inlet, impactor stage, diffusion stage, and a final filter. An impactor stage with 12 nozzles was designed from theory to achieve a cut-off diameter of 300 nm at 50% particle collection efficiency (d50). Various depths of 37-mm-diameter polyurethane foam cylinders were tested for the diffusion stage to obtain a collection efficiency curve similar to the deposition of nanoparticles in the human respiratory tract, known as the nanoparticulate matter (NPM) criterion. The objective for the final filter was a collection efficiency of near 100% with minimal pressure drop. The collection efficiencies by size and pressure drops were measured for all NRD sampler components. The final design of the impactor stage nozzle achieved a d50 of 305 nm. The collection efficiency for the diffusion stage with a depth of 7 cm when adjusted for presence of the impactor was the closest to the NPM curve with a R2 value of 0.96 and d50 of 43 nm. Chemical analysis of the metal content for foam affirmed that the high-flow NRD sampler required less sampling time to meet metal LOQs than the 2.5 L/min NRD sampler. The final filter with a modified support pad had a collection efficiency near 100%. The overall pressure drop of the sampler of 8.5 kPa (34 in. H2O) could not be handled by commercial personal sampling pumps. Hence the high-flow NRD sampler can be used as an area sampler or without the final filter for collection of nanoparticles.

Size, composition, morphology, and health implications of airborne incidental metal-containing nanoparticles.

There is great concern regarding the adverse health implications of engineered nanoparticles. However, there are many circumstances where the production of incidental nanoparticles, i.e., nanoparticles unintentionally generated as a side product of some anthropogenic process, is of even greater concern. In this study, metal-based incidental nanoparticles were measured in two occupational settings: a machining center and a foundry. On-site characterization of substrate-deposited incidental nanoparticles using a field-portable X-ray fluorescence provided some insights into the chemical characteristics of these metal-containing particles. The same substrates were then used to carry out further off-site analysis including single-particle analysis using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Between the two sites, there were similarities in the size and composition of the incidental nanoparticles as well as in the agglomeration and coagulation behavior of nanoparticles. In particular, incidental nanoparticles were identified in two forms: submicrometer fractal-like agglomerates from activities such as welding and supermicrometer particles with incidental nanoparticles coagulated to their surface, herein referenced as nanoparticle collectors. These agglomerates will affect deposition and transport inside the respiratory system of the respirable incidental nanoparticles and the corresponding health implications. The studies of incidental nanoparticles generated in occupational settings lay the groundwork on which occupational health and safety protocols should be built.

The Effect of Agglomeration on Arsenic Adsorption Using Iron Oxide Nanoparticles.

The presence of arsenic in groundwater and other drinking water sources presents a notable public health concern. Although the utilization of iron oxide nanomaterials as arsenic adsorbents has shown promising results in batch experiments, few have succeeded in using nanomaterials in filter setups. In this study, the performance of nanomaterials, supported on sand, was first compared for arsenic adsorption by conducting continuous flow experiments. Iron oxide nanoparticles (IONPs) were prepared with different synthetic methodologies to control the degree of agglomeration. IONPs were prepared by thermal decomposition or coprecipitation and compared with commercially available IONPs. Electron microscopy was used to characterize the degree of agglomeration of the pristine materials after deposition onto the sand. The column experiments showed that IONPs that presented less agglomeration and were well dispersed over the sand had a tendency to be released during water treatment. To overcome this implementation challenge, we proposed the use of clusters of iron oxide nanoparticles (cIONPs), synthesized by a solvothermal methodology, which was explored. An isotherm experiment was also conducted to determine the arsenic adsorption capacities of the iron oxide nanomaterials. cIONPs showed higher adsorption capacities (121.4 mg/g) than the other IONPs (11.1, 6.6, and 0.6 mg/g for thermal decomposition, coprecipitation, and commercially available IONPs, respectively), without the implementation issues presented by IONPs. Our results show that the use of clusters of nanoparticles of other compositions opens up the possibilities for multiple water remediation applications.

The Primarily Undergraduate Nanomaterials Cooperative: A New Model for Supporting Collaborative Research at Small Institutions on a National Scale.

The Primarily Undergraduate Nanomaterials Cooperative (PUNC) is an organization for research-active faculty studying nanomaterials at Primarily Undergraduate Institutions (PUIs), where undergraduate teaching and research go hand-in-hand. In this perspective, we outline the differences in maintaining an active research group at a PUI compared to an R1 institution. We also discuss the work of PUNC, which focuses on community building, instrument sharing, and facilitating new collaborations. Currently consisting of 37 members from across the United States, PUNC has created an online community consisting of its Web site (nanocooperative.org), a weekly online summer group meeting program for faculty and students, and a Discord server for informal conversations. Additionally, in-person symposia at ACS conferences and PUNC-specific conferences are planned for the future. It is our hope that in the years to come PUNC will be seen as a model organization for community building and research support at primarily undergraduate institutions.

pH-dependent adsorption of α-amino acids, lysine, glutamic acid, serine and glycine, on TiO2 nanoparticle surfaces.

TiO2 nanoparticles (NPs) are widely used in different applications, and potential exposure to these NPs raises concerns about their impact on human health. In contact with biological fluids, proteins adsorb onto NPs to create a protein corona. Protein adsorption is highly dependent on the affinity between exterior amino acid residues and the NP surface. Thus, studying amino acids adsorption onto NPs can provide insight into protein corona formation. Herein, the pH-dependent adsorption of α-amino acids onto TiO2 NPs in buffered solutions is described. Methods include attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy to analyze molecular interactions and dynamic light scattering (DLS) to measure changes in size and zeta-potential upon adsorption. Depending on the predominant speciation and TiO2 NP surface charge, adsorption involves a combination of carboxylate and amine group interactions. Gly and Lys reveal a similar trend of higher adsorption with increasing pH. In contrast, Glu adsorption decreases with increasing pH. Ser adsorption onto TiO2 NPs surfaces is the highest around pHIEP. These differences are attributed to the different speciation of the functional groups within the amino acids and the TiO2 surface charge at each pH. Under our experimental conditions, multiple surface species coexist at different pH values. Protonated surface species are present for all amino acids at pH 2. At pH 9, Lys and Glu adsorbate spectra have new peaks at 1740 cm-1 and 1744 cm-1, respectively. This is a possible result of surface-induced deprotonation of the amine group and proton transfer to the carboxylate. Analyzing the pH-dependent adsorption of amino acids can provide a better understanding of biomolecule-surface interactions in in vivo and different biological milieu.

Physicochemical properties of air discharge-generated manganese oxide nanoparticles: Comparison to welding fumes.

Exposures to high doses of manganese (Mn) via inhalation, dermal contact or direct consumption can cause adverse health effects. Welding fumes are a major source of manganese containing nanoparticles in occupational settings. Understanding the physicochemical properties of manganese-containing nanoparticles can be a first step in understanding their toxic potential following exposure. In particular, here we compare the size, morphology and Mn oxidation states of Mn oxide nanoparticles generated in the laboratory by arc discharge to those from welding collected in heavy vehicle manufacturing. Fresh nanoparticles collected at the exit of the spark discharge generation chamber consisted of individual or small aggregates of primary particles. These nanoparticles were allowed to age in a chamber to form chain-like aggregates of primary particles with morphologies very similar to welding fumes. The primary particles were a mixture of hausmannite (Mn3O4), bixbyite (Mn2O3) and manganosite (MnO) phases, whereas aged samples revealed a more amorphous structure. Both Mn2+ and Mn3+, as in double valence stoichiometry present in Mn3O4, and Mn3+, as in Mn2O3 and MnOOH, were detected by X-ray photoelectron spectroscopy on the surface of the nanoparticles in the laboratory nanoparticles and welding fumes. Dissolution studies conducted for these two Mn samples (aged and fresh fume) reveal different release kinetics of Mn ions in artificial lysosomal fluid (pH 4.5) and very limited dissolution in Gamble's solution (pH 7.4). Taken together, these data suggest several important considerations for understanding the health effects of welding fumes. First, the method of particle generation affects the crystallinity and phase of the oxide. Second, welding fumes consist of multiple oxidation states whether they are amorphous or crystalline or occur as isolated nanoparticles or agglomerates. Third, although the dissolution behavior depends on conditions used for nanoparticle generation, the dissolution of Mn oxide nanoparticles in the lysosome may promote Mn ions translocation into various organs causing toxic effects.

Particle Concentrations in Occupational Settings Measured with a Nanoparticle Respiratory Deposition (NRD) Sampler.

There is an increasing need to evaluate concentrations of nanoparticles in occupational settings due to their potential negative health effects. The Nanoparticle Respiratory Deposition (NRD) personal sampler was developed to collect nanoparticles separately from larger particles in the breathing zone of workers, while simultaneously providing a measure of respirable mass concentration. This study compared concentrations measured with the NRD sampler to those measured with a nano Micro Orifice Uniform-Deposit Impactor (nanoMOUDI) and respirable samplers in three workplaces. The NRD sampler performed well at two out of three locations, where over 90% of metal particles by mass were submicrometer particle size (a heavy vehicle machining and assembly facility and a shooting range). At the heavy vehicle facility, the mean metal mass concentration of particles collected on the diffusion stage of the NRD was 42.5 ± 10.0 µg/m3, within 5% of the nanoMOUDI concentration of 44.4 ± 7.4 µg/m3. At the shooting range, the mass concentration for the diffusion stage of the NRD was 5.9 µg/m3, 28% above the nanoMOUDI concentration of 4.6 µg/m3. In contrast, less favorable results were obtained at an iron foundry, where 95% of metal particles by mass were larger than 1 µm. The accuracy of nanoparticle collection by NRD diffusion stage may have been compromised by high concentrations of coarse particles at the iron foundry, where the NRD collected almost 5-fold more nanoparticle mass compared to the nanoMOUDI on one sampling day and was more than 40% different on other sampling days. The respirable concentrations measured by NRD samplers agreed well with concentrations measured by respirable samplers at all sampling locations. Overall, the NRD sampler accurately measured concentrations of nanoparticles in industrial environments when concentrations of large, coarse mode, particles were low.