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This work demonstrates the rapid coating of gold nanoparticles (AuNPs) onto electrospun composite polyacrylonitrile (PAN) nanofibers containing a large amount of graphene oxide (GO) and reduced graphene oxide (rGO) for photothermally-driven applications. A modification of GO with a cationic surfactant greatly improves its loading efficiency into the PAN nanofibers, and the subsequent hydrazine treatment readily converts the integrated GO into rGO. Rapid loading of AuNPs onto these membranes results in measurably higher photothermal heating characteristics than the pristine PAN, GO-PAN, and rGO-PAN membranes under a solar-simulated light source. The light-induced heating properties are then utilized in the removal of organic dyes in an aqueous solution. While the GO-PAN and rGO-PAN membranes remove the dyes via physical adsorption, the AuNP-loaded membranes show an additional catalytic decomposition process, resulting in detectably faster removal rates. The degradation of the organic dyes is accelerated under a solar simulated light source due to the light-enhanced heating and photocatalytic properties of the integrated AuNPs. The ability to maximize the dual properties of these membranes can greatly reduce toxic organic pollutants, which can lead to the development of practical water purification systems under sunlight irradiation. [ABSTRACT FROM AUTHOR]

This report describes the formation of gold-coated silver bimetallic nanoparticles prepared by the one-pot synthetic approach which involves the subsequent reduction of silver and gold ions at ambient conditions. The reduction of silver ions by excess L-ascorbic acid initially led to the formation of silver cores. This step was followed by the addition of gold ions into the preformed cores, resulting in the formation of silver-core gold-shell type bimetallic nanoparticles at room temperature. This process systematically allowed for the formation of various bimetallic nanoparticles which exhibited tunable absorption properties corresponding to the visible and near-IR regions. The thickness of the gold shells and the diameter of the silver-core nanoparticles were readily controlled; the morphological and structural properties of the resulting bimetallic nanoparticles were thoroughly analyzed by SEM/TEM, DLS, and UV--Vis spectrophotometry. The overall results demonstrated not only that these gold-coated silver nanoparticles were reliably prepared by our one-pot synthetic approach, but also that their optical properties were tunable in the visible and near-IR areas as a function of the core size and shell thickness. Keywords Bimetallic nanoparticles. Gold. Silver. Near infrared. Core--shell, Introduction The preparation of metal nanoparticles in small sizes that absorb in the visible and near-IR spectral regions remains an ongoing challenge to colloidal science (1), (2). Access to these [...]

Multiple gold nanoparticles (AuNPs) are physically encapsulated within a poly(N‐isopropylacrylamide) particle at room temperature by an in situ reduction method using trisodium citrate (Cit) and sodium oxalate (Oxa) to serve as quasi‐homogeneous catalysts for carbon−carbon bond‐forming reactions under base‐free aerobic conditions. The use of Oxa results in a more rapid formation and higher loading of AuNPs within the polymer particles compared to those prepared with conventional Cit. Upon dispersing both composite particles in EtOH‐rich aqueous solvents, the polymer matrices maintain a fully swollen structure while still providing great stability to the AuNPs whose surfaces are analyzed to be nearly free from the reducing/stabilizing agents. As a catalyst in homocoupling reactions, the composite particles prepared with Oxa exhibit higher activity, selectivity, and recyclability with a much lower activation energy than those prepared with Cit. The preparation of the composite particles and their catalytic properties are optimized under environmentally‐friendly reaction conditions, and the relationship between structural features and catalytic functions are examined to potentially develop robust, versatile, and green catalytic systems. [ABSTRACT FROM AUTHOR]

ABSTRACT Varying amounts of exfoliated graphene oxide (GO) are systematically incorporated into nanoscale polyacrylonitrile (PAN) fibers via an electrospinning method. Subsequent treatment of the PAN-GO composite nanofibers under a moderate temperature and high pressure leads to the formation of membrane sheets with enhanced mechanical properties. scanning electron microscope, Fourier transform infrared spectroscopy, and contact angle measurements confirm the successful incorporation of the GO into the PAN nanofiber membranes whose diameter, porosity, and pore size are notably influenced by the amount of the GO content. These composite membranes also exhibit a gradual reduction in the water contact angle as a function of the hydrophilic GO content, resulting in a beneficial property for water purification. In addition, the proper integration of GO into the PAN nanofibers improves the protein rejection rate and water flux during the filtration process, which indicates the possibility of utilizing these types of composite membranes in water treatment systems. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45858. [ABSTRACT FROM AUTHOR]