SEM analysis of particle size during conventional treatment of CMP process wastewater.

Engineered nanomaterials (ENMs) are currently employed by many industries and have different physical and chemical properties from their bulk counterparts that may confer different toxicity. Nanoparticles used or generated in semiconductor manufacturing have the potential to enter the municipal waste stream via wastewater and their ultimate fate in the ecosystem is currently unknown. This study investigates the fate of ENMs used in chemical mechanical planarization (CMP), a polishing process repeatedly utilized in semiconductor manufacturing. Wastewater sampling was conducted throughout the wastewater treatment (WWT) process at the fabrication plant's on-site wastewater treatment facility. The goal of this study was to assess whether the WWT processes resulted in size-dependent filtration of particles in the nanoscale regime by analyzing samples using scanning electron microscopy (SEM). Statistical analysis demonstrated no significant differences in particle size between sampling points, indicating low or no selectivity of WWT methods for nanoparticles based on size. All nanoparticles appeared to be of similar morphology (near-spherical), with a high variability in particle size. EDX verified nanoparticles composition of silicon- and/or aluminum-oxide. Nanoparticle sizing data compared between sampling points, including the final sampling point before discharge from the facility, suggested that nanoparticles could be released to the municipal waste stream from industrial sources.

Hyperspectral microscopy as an analytical tool for nanomaterials.

Hyperspectral microscopy is an advanced visualization technique that combines hyperspectral imaging with state-of-the-art optics and computer software to enable the rapid identification of materials at the micro- and nanoscales. Achieving this level of resolution has traditionally required time-consuming and costly electron microscopy techniques. While hyperspectral microscopy has already been applied to the analysis of bulk materials and biologicals, it shows extraordinary promise as an analytical tool to locate individual nanoparticles and aggregates in complex samples through rapid optical and spectroscopic identification. This technique can be used to not only screen for the presence of nanomaterials, but also to locate, identify, and characterize them. It could also be used to identify a subset of samples that would then move on for further analysis via other advanced metrology. This review will describe the science and origins of hyperspectral microscopy, examine current and emerging applications in life science, and examine potential applications of this technology that could improve research efficiency or lead to novel discoveries.

Identification of Metal Oxide Nanoparticles in Histological Samples by Enhanced Darkfield Microscopy and Hyperspectral Mapping.

Nanomaterials are increasingly prevalent throughout industry, manufacturing, and biomedical research. The need for tools and techniques that aid in the identification, localization, and characterization of nanoscale materials in biological samples is on the rise. Currently available methods, such as electron microscopy, tend to be resource-intensive, making their use prohibitive for much of the research community. Enhanced darkfield microscopy complemented with a hyperspectral imaging system may provide a solution to this bottleneck by enabling rapid and less expensive characterization of nanoparticles in histological samples. This method allows for high-contrast nanoscale imaging as well as nanomaterial identification. For this technique, histological tissue samples are prepared as they would be for light-based microscopy. First, positive control samples are analyzed to generate the reference spectra that will enable the detection of a material of interest in the sample. Negative controls without the material of interest are also analyzed in order to improve specificity (reduce false positives). Samples can then be imaged and analyzed using methods and software for hyperspectral microscopy or matched against these reference spectra in order to provide maps of the location of materials of interest in a sample. The technique is particularly well-suited for materials with highly unique reflectance spectra, such as noble metals, but is also applicable to other materials, such as semi-metallic oxides. This technique provides information that is difficult to acquire from histological samples without the use of electron microscopy techniques, which may provide higher sensitivity and resolution, but are vastly more resource-intensive and time-consuming than light microscopy.

Comparative analysis of redox and inflammatory properties of pristine nanomaterials and commonly used semiconductor manufacturing nano-abrasives.

Continued expansion of the nanotechnology industry has necessitated the self-assessment of manufacturing processes, specifically in regards to understanding the health related aspects following exposure to nanomaterials. There exists a growing concern over potential occupational exposure in the semiconductor industry where Al2O3, CeO2 and SiO2 nanoparticles are commonly featured as part of the chemical mechanical planarization (CMP) process. Chronic exposure to toxicants can result not only in acute cytotoxicity but also initiation of a chronic inflammatory state associated with diverse pathologies. In the current investigation, pristine nanoparticles and CMP slurry formulations of Al2O3, SiO2 and CeO2 were employed to assess their ability to induce cytotoxicity, inflammatory responses and reactive oxygen species in a mouse alveolar macrophage cell model. The pristine nanoparticles and slurries were not intrinsically cytotoxic and did not generate free radicals but were found to act as scavengers in the presence of an oxidant stimulant. Al2O3 and SiO2 nanoparticles increased levels of pro-inflammatory cytokines while pristine SiO2 nanoparticles induced generation of F2-Isoprostanes. In co-treatment studies, the pristine nanomaterials modulated the response to the inflammatory stimulant lipopolysaccharide. The studies have established that pristine nanoparticles and slurries do not impact the cells in a similar way indicating that they should not be used as slurry substitutes in toxicity evaluations. Further, we have defined how an alveolar cell line, which would likely be the first challenged upon nanomaterial aerosolization, responds to diverse mixtures of nanomaterials. Moreover, our findings reinforce the importance of using multiple analytic methods to define the redox state of the cell following exposure to commonly used industrial nanomaterials and toxicants.

The bioconcentration and metabolism of chlorpyrifos by the eastern oyster, Crassostrea virginica.

Eastern oysters (Crassostrea virginica) were exposed to [14C]chlorpyrifos (O,O-diethyl-O-[3,5,6-trichloro-2-pyridyl] phosphorothioate) at an average measured seawater concentration of 0.6 microg/L under flow-through conditions for 28 d. The compound O,O-diethyl-O-(3,5-dichloro-6-methylthio-2-pyridyl)phosphorothioate (DMP) was extracted and identified as the single metabolite observed, and this metabolite constituted the majority of the total [14C] activity in the oyster at all sampling times. Once oysters were exposed to clean water, both chlorpyrifos and DMP residues cleared rapidly from whole oysters, with elimination half-lives of <3 d. A simple two-compartment uptake/elimination model was adequate to describe total [14C] activity in whole oysters, edible tissue, and oyster liquor. The average bioconcentration factors (BCFs) for total [14C] activity in whole oysters, edible tissue, and oyster liquor were 565, 1,400, and 35 ml/g, respectively. The parent [14C]chlorpyrifos accumulated to a peak residue concentration of 135 microg/kg in whole oyster tissue, representing an empirical [14C]chlorpyrifos BCF value in the oyster of approximately 225 ml/ g; the BCF value for [14C]chlorpyrifos was lower than the BCF for total [14C] activity in whole oysters and edible tissue because of extensive metabolism to DMP and oyster elimination processes.