The free-volume depth profile of asymmetric polymeric membrane systems prepared by interfacial polymerization is studied using positron annihilation spectroscopy coupled with a variable monoenergy slow positron beam. Significant variations of S, W, and R parameters from the Doppler broadened energy spectra vs positron incident energy up to 30 keV and orthopositronium lifetime and intensity are observed at different doping times of triethylenetetraamine (TETA) reacting with trimesoyl chloride (TMC) in an interfacial polymerization on modified porous polyacrylonitrile (PAN) asymmetric membrane. The positron annihilation data are analyzed in terms of free-volume parameters as a function of depth from the surface to nano- and micrometer regions of asymmetric membranes. A multilayer structure is obtained in polymerized polyamide (PA) on modified PAN membranes (m-PAN):  a nanometer scale skin polyamide layer, a nanometer to micrometer scale transition layer from dense to porous m-PAN, and the porous m-PAN support. The results of free-volume parameters and obtained layer thicknesses are compared with the flux (permeability) and water concentration in permeate (selectivity) through the pervaporation separation of 70 wt % 2-propanol aqueous solution. It is found that the water concentration in permeate is mainly controlled by the free-volume properties of skin polyamide and weakly related to the transition layer from the skin to porous m-PAN. The obtained layer structures of asymmetric polymeric membranes are supported by the data obtained by AFM, SEM, and ATR−FTIR.

Understanding tissue biodistribution and clearance of zinc oxide nanoparticles (ZnO-NPs) is necessary for its risk assessment. Both fed and intraperitoneally injected ZnO-NPs (2.5 g/kg) were absorbed into circulation (within 30 min post-dosing), then biodistributed to the liver, spleen, and kidney. Intraperitoneally injected ZnO-NPs remained in serum for 72 h and could more effectively spread to the heart, lung, and testes, whereas the clearance for fed ZnO-NPs in serum began 6 h after oral administration. Compared with zinc oxide microparticles (ZnO-MPs), ZnO-NPs exhibited much higher absorptivity and tissue biodistribution in fed treatment. A greater fraction of fed ZnO-NPslocalised in the liver resulted in transient histopathological lesions. However, superoxide generation and cytotoxicity were showed in vitro treatment with ZnO-NPs (above 20 μg/mL). Considering both in vitro and in vivo data, the ZnO-NPs induced acute liver toxicity which was in compliance with its absorption, biodistribution, and clearance.

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A technique of layer-by-layer (LbL) self-assembly was used to prepare transparent multilayered gas barrier films consisting of graphene oxide (GO)/branched poly(ethylenimine) (BPEI) on a poly(ethylene terephthalate) substrate. The effect of the GO suspension pH on the nanostructure and oxygen barrier properties of the GO/BPEI film was investigated. The oxygen barrier properties of the assemblies were shown to be highly dependent on the pH. It was demonstrated that the film assemblies prepared using a GO suspension with a pH of 3.5 exhibited very dense and ordered structures and delivered very low oxygen transmission rates (the lowest was <0.05 cm(3) m(-2) day(-1)). The assemblies were characterized with ultraviolet-visible spectroscopy and ellipsometry to identify the film growth mechanism, and the result indicated a linear growth behavior. To analyze the nanostructure of the films, atomic force microscopy, transmission electronic microscopy, and grazing incidence wide-angle X-ray diffraction were used.