Hybrid composites of gold nanoparticles (Au NPs) with polymer hydrogels are promising platforms for the development of new materials that can respond to external stimuli (chemical, physical, mechanical), reversibly absorb/release water and reagents, act as plasmonic sensors, and also as catalysts for photochemical processes and photothermal actuators of micromechanical processes. We proposed a one-step synthesis of a hybrid composite of Au NPs doped into polyacrylamide (PAAm) hydrogel by reducing HAuCl4 with acrylamide (AAm) and simultaneous radical polymerization of AAm, initiated by (NH4)2S2O8, in the aqueous solution. The influence of initial concentrations of 0.26–10 mM Au and 0.1–1 M AAm on the morphology and structure of Au NPs, as well as on the phase stability of the products, was studied. At concentrations of 3 mM Au, 1 M AAm and 1.2 mM (NH4)2S2O8, а temperature of 60 °C and a heating time of 6 h, a stable product with a clearly defined SPR band with a maximum at 552 nm was obtained. It contained polycrystalline Au NPs in the form of spheroids, cuboctahedra, and rods up to ~100 nm size. The product was used to obtain plasmonic films of Au NPs-PAAm composite after drying at 100 °C and gold after thermal removal of the polymer matrix at 550 °C.The work used UV-visible and photon correlation spectroscopy, X-ray diffraction, synchronous thermal analysis, transmission and scanning electron microscopy.Graphical Abstract:
Highlights: A hybrid composite of gold nanoparticles with polyacrylamide hydrogel was synthesized by a one-pot, one-step method from H[AuCl4] and acrylamide.Optimal conditions for the synthesis of a stable product are initial concentrations of 3 mM for gold and 1 M for acrylamide, temperature 60 °C.Using a composite hydrogel on glass, films of a dry composite of gold nanoparticles with polyacrylamide were obtained by dehydration at 100 °C and thin gold after heating at 550 °C.Surface plasmon resonance bands in the spectra of the synthesized hybrid composite hydrogel and of films have favorable for use in optical sensing well-defined maxima in the wavelength range 570–600 nm.