Environmental pollutants such as microplastics have become a major concern over the last few decades. We investigated the presence, characteristics, and potential health risks of microplastic dust ingestion. The plastic load of 88 to 605 microplastics per 30 g dry dust with a dominance of black and yellow granule microplastics ranging in size from 250 to 500 μm was determined in 10 street dust samples using a binocular microscope. Fluorescence microscopy was found to be ineffective for detecting and counting plastic debris. Scanning electron microscopy, however, was useful for accurate detection of microplastic particles of different sizes, colors, and shapes (e.g., fiber, spherule, hexagonal, irregular polyhedron). Trace amounts of Al, Na, Ca, Mg, and Si, detected using energy dispersive X-ray spectroscopy, revealed additives of plastic polymers or adsorbed debris on microplastic surfaces. As a first step to estimate the adverse health effects of microplastics in street dust, the frequency of microplastic ingestion per day/year via ingestion of street dust was calculated. Considering exposure during outdoor activities and workspaces with high abundant microplastics as acute exposure, a mean of 3223 and 1063 microplastic particles per year is ingested by children and adults, respectively. Consequently, street dust is a potentially important source of microplastic contamination in the urban environment and control measures are required.

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Conductive polymers with their medium level of conductivity are synthetic materials that can be used as electromagnetic wave absorber. In this work, the effect of aging and washing on the surface resistivity and also the influence of efficient doping and redoping procedure on the dielectric properties and electromagnetic radiation shielding of uniformly polyaniline coated polyester fabric are investigated in the X-band frequency range. They can affect the shielding effectiveness by changing the surface resistivity and dielectric permittivity. It is found that lightweight, flexible, and thin polyaniline-coated polyester fabric sample prepared in 1:1:7 monomer:oxidant:dopant molar ratio and redoped with concentrated HCl vapor shows the highest transmission loss (53–43%) in 8.2–12.4 GHz. Compared to single layer, double and triple layer samples attenuated 71–61% and 83–77% of incident wave, respectively. Absorption was the dominant shielding mechanism. It is also demonstrated that the increment of surface resistivity due to washing of samples is compensated by the redoping process.

We present a model to understand the effect of temperature on the electrical resistance of individual semiconducting single wall carbon nanotubes (s-SWCNTs) of various diameters under various electric fields. The temperature dependence of the resistance of s-SWCNTs and metallic SWCNTs (m-SWCNTs) are compared. These results help us to understand the temperature dependence of the resistance of SWCNTs network. We experimentally examine the temperature dependence of the resistance of random networks of SWCNTs, prepared by dispersing CNTs in ethanol and drop-casting the solution on prefabricated metallic electrodes. Examining various samples with different electrode materials and spacings, we find that the dominant resistance in determination of the temperature dependence of resistance of the network is the resistance of individual tubes, rather than the tube–tube resistance or tube–metal contact resistance. It is also found that the tube–tube resistance depends on the electrode spacing and it is more important for larger electrode spacings. By applying high electric field to burn the all-metallic paths of the SWCNTs network, the temperature dependence of the resistance of s-SWCNTs is also examined. We also investigate the effect of acid treatment of CNTs on the temperature dependence of the resistance of SWCNTs and also multi-wall CNTs (MWCNTs) networks.

Conducting polyaniline-coated polyester textiles have attracted much attention due to their wide range of surface resistivity. The surface resistivity depends strongly on the polymerization condition. In this work, polyaniline coated on textile by in situ chemical polymerization method. The influence of substrate modification, synthesis condition, and especially redoping procedure on the surface resistivity of polyaniline-coated textile was investigated and an optimum condition specified. The obtained results indicate that polymerization in an ice-water bath and in a monomer:oxidant:HCl molar ratio equal to 1:1:7 for about 4-6 h decreases the surface resistivity significantly. Furthermore, the experimental results show that etching the surface of textile and redoping procedure with concentrated HCl vapor can decrease the surface resistivity, in a short time.