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CO2‐triggered in situ hydrogels is developed from waterborne poly(ε‐caprolactone)‐based polyurethane (PU) dispersion and aqueous polyethyleneimine (PEI) solution without any other chemicals and apparatus (e.g., UV light). In the approach, nontoxic CO2 in air is used as a selective trigger for the hydrogel formation. CO2 adsorption onto PEI results in the formation of ammonium cations in PEI and the subsequent multiple ionic crosslinking between PU and PEI chains. Besides the amount of CO2 in air, the rate of hydrogel formation can be controlled by NaHCO3 in the PU–PEI mixture, which serves as a CO2 supplier. The PU hydrogels exhibit tough and stretchable properties with high tensile strength (2.05 MPa) and elongation at break (438.24%), as well as biocompatibility and biodegradability. In addition, the PU hydrogels exhibit high adhesion strength on skin and injectability due to the in situ formation. It is believed that these PU hydrogels have the ideal features for various future applications, such as tissue adhesion barriers, wound dressing, artificial skin, and injectable fillers. [ABSTRACT FROM AUTHOR]

Abstract: Dependence of the stored charges and the tunneling voltages on the tunneling SiO2 thickness for Si nanoparticles embedded in a SiO2 layer formed by the sonochemical method was investigated by using electrostatic force microscopy (EFM) measurements. Bright-field transmission electron microscopy images showed that Si nanoparticles were embedded in a SiO2 layer. EFM images for the Si nanoparticles embedded in a SiO2 layer under applied bias voltages showed that the localized charges remained in the Si nanoparticles embedded in a SiO2 layer. The stored charge in the Si nanoparticles embedded in a SiO2 layer increased with a decrease in the tunneling SiO2 thickness. While the threshold tunneling voltage increased with an increase in the tunneling oxide thickness, the mean amplitude of the tunneling voltage increased with a decrease in the thickness of the tunneling SiO2 layer. [Copyright &y& Elsevier]

Abstract: Capacitance–voltage (C–V) and electrostatic force microscopy (EFM) measurements on Si nanocrystals (Si-NCs) formed by using the sonochemical method were carried out to investigate the charging effects of the Si-NCs. Transmission electron microscopy images and atomic force microscopy images showed that the Si-NCs were created inside the SiO2 layer. The C–V curve and the EFM image showed that the Si-NCs embedded in the SiO2 layer experienced charging effects. The macroscopic surface charge density determined from the C–V curve was in reasonable agreement with the microscopic local value obtained from the EFM image. The present results indicate that the EFM technique might provide a promising method for investigating charging effects in various kinds of nanocrystals embedded in the insulating layer. [Copyright &y& Elsevier]

20 nm SiO2 elliptical membrane nanopores with various thicknesses were directly formed in situ by using a focused electron beam with transmission electron microscopy (TEM). The shrinkage and the expansion behaviors of the SiO2 ellipse nanopores with different thicknesses were attributed to variations in their geometries, in particular their curvatures. The geometric mechanisms of elliptical nanopores with various thicknesses fabricated utilizing a SiO2 membrane with a thickness gradient by using an electron beam irradiation are described on the basis of TEM images, which depend on the electron beam irradiation time. [ABSTRACT FROM AUTHOR]

CO2‐triggered in situ hydrogels is developed from waterborne poly(ε‐caprolactone)‐based polyurethane (PU) dispersion and aqueous polyethyleneimine (PEI) solution without any other chemicals and apparatus (e.g., UV light). In the approach, nontoxic CO2 in air is used as a selective trigger for the hydrogel formation. CO2 adsorption onto PEI results in the formation of ammonium cations in PEI and the subsequent multiple ionic crosslinking between PU and PEI chains. Besides the amount of CO2 in air, the rate of hydrogel formation can be controlled by NaHCO3 in the PU–PEI mixture, which serves as a CO2 supplier. The PU hydrogels exhibit tough and stretchable properties with high tensile strength (2.05 MPa) and elongation at break (438.24%), as well as biocompatibility and biodegradability. In addition, the PU hydrogels exhibit high adhesion strength on skin and injectability due to the in situ formation. It is believed that these PU hydrogels have the ideal features for various future applications, such as tissue adhesion barriers, wound dressing, artificial skin, and injectable fillers. [ABSTRACT FROM AUTHOR]