Nanoparticles are a class of materials with properties distinctively different from their bulk and molecular counterparts. A critical review of the very broad topic of environmental nanoparticles is presented. Because of the vast nature of the topic, the review is focused primarily on gas-borne nanoparticles. The "life history of nanoparticles" is presented, tracking it from its formation to its potential use and eventual fate in the environment. Nanoparticle sources, anthropogenic emissions from industrial and occupational settings, and conversion and formation in the atmosphere are discussed. The ability to characterize and capture these nanoparticles (as would be necessary in a nanoparticle production system), as well as their control (of emissions from an industrial source) is discussed. A description on the use of nanoparticles in environmental technologies and the potential impact on the energy sector is provided. The potential effects on human health and the environment, both adverse and beneficial, are important aspects that need to be considered. As will be evident, the study of "environmental nanoparticles" is a new and fast-growing field. Much work remains to be done before we can fully harness the advantages of nanoparticles and ensure that there are no potential adverse consequences. A set of recommendations for additional work in each area is provided.

https://www.tandfonline.com/doi/pdf/10.1080/10473289.2005.10464656

Nanoparticles and the Environment

A method to investigate the dependence of the physicochemical properties of nanoparticles (e.g. size, surface area and crystal phase) on their oxidant generating capacity is proposed and demonstrated for TiO(2) nanoparticles. Gas phase synthesis methods that allow for strict control of size and crystal phase were used to prepare TiO(2) nanoparticles. The reactive oxygen species (ROS) generating capacity of these particles was then measured. The size dependent ROS activity was established using TiO(2) nanoparticles of 9 different sizes (4 - 195 nm) but the same crystal phase. For a fixed total surface area, an S-shaped curve for ROS generation per unit surface area was observed as a function of particle size. The highest ROS activity per unit area was observed for 30 nm particles, and observed to be constant above 30 nm. There was a decrease in activity per unit area as size decreased from 30 nm to 10 nm; and again constant for particles smaller than 10 nm. The correlation between crystal phase and oxidant capacity was established using TiO(2) nanoparticles of 11 different crystal phase combinations but similar size. The ability of different crystal phases of TiO(2) nanoparticles to generate ROS was highest for amorphous, followed by anatase, and then anatase/rutile mixtures, and lowest for rutile samples. Based on evaluation of the entire dataset, important dose metrics for ROS generation are established. Their implications of these ROS studies on biological and toxicological studies using nanomaterials are discussed.

/pdf/does-nanoparticle-activity-depend-upon-size-and-crystal-52dgjrh6ip.pdf

Does Nanoparticle Activity Depend upon Size and Crystal Phase

https://digital.library.unt.edu/ark:/67531/metadc902577/m2/1/high_res_d/924853.pdf

Indoor pollutants emitted by office equipment: A review of reported data and information needs

Source profiles of volatile organic compounds associated with solvent use in Beijing, China

Nanoparticle filtration by electrospun polymer fibers

Indoor air quality for chemical and ultrafine particle contaminants from printers

In order to develop an effective dry surface cleaning method, removal of fine particles by pulse air jets was experimentally investigated. A dimensionless resuspension parameter, F*, which is the ratio of drag force on particles to van der Waals adhesion force, was introduced to correlate the removal efficiency. Resuspension experiments were carried out with monodisperse PSL particles and wax particles with diameter between 0.25 and 1.1 μm on silicon wafer and glass plate. As a result, it was found that deposition process of particles on the surface (gravitational settling and impaction at a relatively low impaction velocity) has little effect on the removal efficiency and that consecutive pulse air jet is effective in the removal of fine particles. Further, F* is the key parameter in determining the removal efficiency. The prediction method for the removal efficiency by pulse air jets with F* is proposed.

Removal of Fine Particles from Smooth Flat Surfaces by Consecutive Pulse Air Jets

Charging of particles in unipolar coronas irradiated by in-situ soft X-rays: enhancement of capture efficiency of ultrafine particles

Electret filters are frequently used in air cleaners because they have a lower pressure drop than the mechanical filters at the same collection efficiency. Manufacturers of electret filters have tried to increase the electrical charge density of electret fibers in order to improve the collection performance. Through these efforts, high-performance electret filter (HPEF) is developed and a question is raised on whether the previous prediction equations for collection efficiency are applicable to these HPEF because the prediction equations were never tested for such high charge density electret filters. In the present work, we measured the collection efficiencies of recently-developed HPEF and studied the applicability of previous prediction equations for collection efficiencies. As a result, HPEF had the electrical charge density twenty times as high as that of the previously-studied electret filter and the single fiber efficiency was close to the maximum limit determined by the packing density of fibers. Furthermore, it is found that the electrical charge of HPEF is fairly stable against organic solvent, leaving one-third of initial charge after soaking it with ethanol. In predicting the collection efficiency of HPEF, the conventional equation can be applied to the collection by induced force, however that by Coulombic force is not applicable because the single fiber efficiency due to induced force and Brownian diffusion is high and close to the upper limit without the collection by Coulombic force.

Prediction of collection efficiency of high-performance electret filters

The dynamic mechanical properties of hybrids of chlorinated polyethylene (CPE) and 3,9-bis[1,1-dimethyl-2{β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5,5]-undecane (AO-80) were investigated. The CPE/AO-80 hybrids showed a novel relaxation in addition to the glass transition of CPE. The novel relaxation is attributed to the dissociation of intermolecular hydrogen bonds within the AO-80–rich domain. The Payne effect, that is, the decrease of the storage modulus E′ with increasing strain amplitude and the appearance of a loss modulus E″ maximum at a strain of 0.6%, was observed for the CPE/AO-80 hybrids. This result demonstrates that the AO-80–rich domains within matrix polymer CPE form a network. The Payne effect is considered to be attributed to the mechanical disruption of segment–segment contacts at a sufficiently great strain. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1788–1793, 2001

Norikazu Namiki

Papers

Indoor air quality for chemical and ultrafine particle contaminants from printers

Removal of Fine Particles from Smooth Flat Surfaces by Consecutive Pulse Air Jets

Charging of particles in unipolar coronas irradiated by in-situ soft X-rays: enhancement of capture efficiency of ultrafine particles

Prediction of collection efficiency of high-performance electret filters

Dynamic properties of an organic hybrid of chlorinated polyethylene and hindered phenol compound