Study on Enhancement Mechanism of Conductivity Induced by Graphene Oxide for Polypyrrole Nanocomposites

Polypyrrole (PPy)/graphene oxide (GO) nanosheet composites with different GO content have been successfully prepared. The morphology, microstructure, defect property and conducting mechanism were examined by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscope (FE-SEM), X-ray photoelectron spectra (XPS), positron annihilation technology (PAT), and electrical conductivity measurements for PPy/GO conducting nanocomposites, respectively. Experimental results indicated that PPy was deposited onto the GO surface homogeneously. Four orders of magnitude increase in electrical conductivity was successfully achieved with small quantities of GO compared to pristine PPy. In order to elucidate the conducting mechanism, an electron transfer model was used to describe bipolaronic formation, which can be confirmed by XPS and positron annihilation parameters measured including positron annihilation lifetimes, positron annihilation Doppler broadening spectroscopy (DBS) and continuous distribution of positron lifetime. Electronic conductivity enhancement can be attributed to (a) the interfacial interaction between the GO layers and PPy results in the electron transfer, which leads to the increase of bipolaronic concentration, and (b) the π–π stacking between the GO layers and PPy can improve the conjugation degree of the PPy chains and the longer conjugation length makes the conducting particle delocalization more easily, leading to the increase in electron mobility. On the other hand, the continuous conducting network structure of graphene nanosheets homogeneously dispersed in the PPy matrix and carriers between localized states formed at the graphene–PPy interfaces where hopping occurred, also result in increase of conductivity

Robust and Low-Cost Flame-Treated Wood for High-Performance Solar Steam Generation

Solar-enabled steam generation has attracted increasing interest in recent years because of its potential applications in power generation, desalination, and wastewater treatment, among others. Recent studies have reported many strategies for promoting the efficiency of steam generation by employing absorbers based on carbon materials or plasmonic metal nanoparticles with well-defined pores. In this work, we report that natural wood can be utilized as an ideal solar absorber after a simple flame treatment. With ultrahigh solar absorbance (∼99%), low thermal conductivity (0.33 W m^–1 K^–1), and good hydrophilicity, the flame-treated wood can localize the solar heating at the evaporation surface and enable a solar-thermal efficiency of ∼72% under a solar intensity of 1 kW m^–2, and it thus represents a renewable, scalable, low-cost, and robust material for solar steam applications

Interaction between Surfactants and SiO₂ Nanoparticles in Multiphase Foam and Its Plugging Ability

To improve the stability of foam fluids, SiO₂ nanoparticles and trace amount of Gemini cationic surfactant were combined with the main foaming agent, nonionic surfactant, to form a tricomponent multiphase foam. The stability of the multiphase foam was assessed through two parameters of half-life time and dilational modulus. The interaction between surfactants and nanoparticles were studied though surface tension, adsorption amount, and ζ potential measurement. The effects of saline ions and temperature on foam stability were also investigated. The plugging ability of the tricomponent multiphase foam was assessed using a sandpack model. The optimized tricomponent multiphase foam was 10 times more stable than corresponding foam without nanoparticles in terms of half-life time and also resisted to saline and temperature to a certain degree because the adsorption of nanoparticles at the interface improved the mechanic strength of foam film. The tricomponent multiphase foam showed more excellent plugging ability in porous media than foam without nanoparticles during flooding. The adsorption of cationic surfactant not only changed the surface hydrophobicity of the SiO₂ nanoparticles, but also promoted the adsorption of APG molecules. Combined the results of Gemini C₁₂C₃C₁₂Br₂ replaced by CTAB or SDS, and C₁₂C₃C₁₂Br₂/SiO₂ replaced by pretreated partially hydrophobic SiO₂ nanoparticle (H15), it is deduced that the in situ surface modification by cationic adsorption to a suitable hydrophobicity was a key step in multiphase stability. Compared with the pretreated partially hydrophobic SiO₂ nanoparticle, more SiO₂ nanoparticles were distributed at the air/liquid interface and utilized effectively in the tricomponent multiphase foam