A tunable high-pass filter for simple and inexpensive size-segregation of sub-10-nm nanoparticles.

Recent advanced in the fields of nanotechnology and atmospheric sciences underline the increasing need for sizing sub-10-nm aerosol particles in a simple yet efficient way. In this article, we develop, experimentally test and model the performance of a High-Pass Electrical Mobility Filter (HP-EMF) that can be used for sizing nanoparticles suspended in gaseous media. Experimental measurements of the penetration of nanoparticles having diameters down to ca 1nm through the HP-EMF are compared with predictions by an analytic, a semi-empirical and a numerical model. The results show that the HP-EMF effectively filters nanoparticles below a threshold diameter with an extremely high level of sizing performance, while it is easier to use compared to existing nanoparticle sizing techniques through design simplifications. What is more, the HP-EMF is an inexpensive and compact tool, making it an enabling technology for a variety of applications ranging from nanomaterial synthesis to distributed monitoring of atmospheric nanoparticles.

Airborne engineered nanoparticles: potential risks and monitoring challenges for assessing their impacts on children.

Engineered nanoparticles (ENPs) are the building blocks of novel materials and consumer products that hold great promise for our societies. When ENPs are released to the environment, however, they can induce irreversible processes that can affect human health. To ensure safety for all nanoparticle-based products throughout their life cycle we urgently need to develop techniques for determining their toxic effects and the exposure levels of humans to ENPs. In an attempt to estimate whether nanotechnology can threaten more sensitive parts of the population such as children, we provide a brief overview of the potential pathways of introducing ENPs into the environment and the state-of-the-art techniques for assessing human exposure, as well as our current knowledge on their toxic effects.

Charge dependent catalytic activity of gasborne nanoparticles.

It is shown experimentally that the electric charge of unsupported catalyst particles has a major influence on the methanation of CO with nano-sized Ni particles as catalyst at temperatures between 680 K and 720 K. Neutral particles showed an apparent activation energy of 148 kJ/mol, significantly higher than the apparent activation energies of 43 kJ/mol and 60 kJ/mol for negatively and positively charged particles, respectively. The obtained activation energies are comparable to energies obtained for different sites on alumina supported nickel catalysts. The change in activation energy can be qualitatively explained by different electron interchange between the chemisorbed species and the catalyst. We suggest that the observed effect of electron enhancement or depletion on catalysis is also a governing effect in strong metal support interaction (SMSI), where the displacement of electrons is related to the contact potential between catalyst and substrate.

Monitoring the soot emissions of passing cars.

We report on the first application of a novel fast on-road sensing method for measurement of particulate emissions of individual passing passenger cars. The studywas motivated by the shift of interest from gases to particles in connection with strong adverse health effects. The results correspond very much to findings by Beaton et al. (Science, May 19,1995) for gaseous hydrocarbon and CO emissions: A small percentage of "superpolluters" (here 5%) account for a high percentage (here 43%) of the pollution (here elemental carbon). We estimate that up to 50% of the particulate emissions of vehicles could be avoided on the basis of the present legislation, if on-road monitoring would be applied to enforce maintenance. Our fast sensing method for particles is based on photoelectron emission from the emitted airborne soot particles in combination with a CO2 sensor delivering a reference.

BIOMarkers for occupational diesel exhaust exposure monitoring (BIOMODEM)--a study in underground mining.

Methods for the assessment of exposures to diesel exhaust were evaluated, including various biomarkers of internal exposure and early biological effects. The impact of possible biomarkers of susceptibility was also explored. Underground workers (drivers of diesel-powered excavators) at an oil shale mine in Estonia were compared with surface workers. Personal exposures to particle-associated 1-nitropyrene (NP) were some eight times higher underground than on the surface. Underground miners were also occupationally exposed to benzene and polycyclic aromatic hydrocarbons, as indicated by excretion of urinary metabolites of benzene and pyrene. In addition, increased O(6)-alkylguanine DNA adducts were detected in the white blood cells of underground workers, suggesting higher exposure to nitroso-compounds. However, no differences between underground and surface workers were observed in the levels of other bulky DNA adducts determined by 32P-postlabelling, or in DNA damage. The study indicated that smoking, diet and residential indoor air pollution are important non-occupational factors to consider when interpreting biomonitoring results.