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One-step synthesis of poly(ethylene oxide)/gold nanocomposite hydrogels and suspensions using gamma-irradiation

Gold nanoparticles (AuNPs) possess unique electrical and optical properties, depending on their size and shape. AuNPs have found applications in analytical chemistry, catalysis and in biomedicine. They are used as contrast agents, for photothermal therapy, drug delivery, tissue engineering and as radiosensitisation agents. gamma-irradiation is highly suitable method for synthesis of nanoparticles (NPs) of controlled size and shape in solution as well as for synthesis of NPs within the three-dimensional polymer network, thus producing nanocomposite gels. The specials interest is on synthesis of nanocomposite gels in a single step, that is simultaneous crosslinking of polymers chains and reduction of metal salts. The aim of this work is to obtain the PEO/AuNPs stable suspensions and PEO/Au nanocomposite hydrogels using one-step γ-irradiation synthesis. The PEO/Au3+ aqueous solutions were γ-irradiated under inert atmosphere at different doses. The influences of dose, pH, Au3+ concentration and PEO/Au3+ ratio were investigated. The Au3+ ions were reduced without addition of 2-propanol. Depending on the experimental conditions the irradiation of PEO/Au3+ aq. solutions resulted in formation of red gels or red to purple suspensions. The pH of the initial solutions had the major influence on the formation of PEO/Au nanocomposite hydrogels vs. suspensions. The pH, Au3+ initial concentration and PEO/Au3+ ratio determined the AuNPs size and suspension stability. The neutral pH favoured the formation of stable red AuNPs suspensions, whereas the alkaline pH conditions produced firm red PEO/Au hydrogels. SEM revealed the AuNPs embedded in PEO matrix. DSC measurements revealed that PEO/Au nanocomposite gels had smaller melting and crystallization enthalpies than pure PEO gels irradiated at the same dose and that melting temperatures increases with the amount of NPs. The viscoelastic properties and structural strength of PEO/Au gels depended on the concentration of embedded AuNPs.

PEO ; gold ; nanocomposite ; gamma-irradiation ; synthesis ; DSC ; rheology

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