Silver nanoparticles stabilized by thermoresponsive microgel particles: Synthesis and evidence of an electron donor-acceptor effect

Well-dispersed silver nanoparticles were successfully fabricated within poly[(N-isopropylacrylamide)-co-(acrylic acid)] [P(NIPAM-co-AA)] microgel particles which were synthesized with different cross-linking densities. Their structures were studied by field-emission scanning electron microscopy, transmission electron microscopy, UV-vis spectroscopy, X-ray diffraction and FT-IR spectroscopy. The interactions between the microgel particles and the incorporated silver nanoparticles were investigated by X-ray photoelectron spectroscopy. The results revealed that there was charge transfer from the carbonyl groups of the microgel particles to the silver nanoparticles Moreover., as the diameter of the AgNPs decreases the charge-transfer efficiency increases accordingly. The P(NIPAM-co-AA)/AgNPs hybrid microgel particles were thermoresponsive and their behavior completely reversible with several heating/cooling cycles.