Interaction of gold nanoparticles with thermoresponsive microgels: influence of the cross-linker density on optical properties

Abstract

The interaction of spherical gold nanoparticles (Au-NPs) with microgels composed of chemically crosslinked poly-(N-isopropylacrylamide) is reported. Simple mixing of the two components leads to adsorption of the gold particles onto the microgels. Different loading densities can be achieved by varying the ratio of gold particles to microgel particles. The adsorption of gold nanoparticles is analysed by TEM, UV-Vis absorption spectroscopy and SAXS. The influence of the microgel mesh size on the adsorption of gold nanoparticles is investigated by using microgels with three different cross-linker densities. The results suggest a strong relationship between the nanoparticle penetration depth and the cross-linker density. This, in turn, directly influences the optical properties of the colloids due to plasmon resonance coupling. In addition, information about the mesh size distribution of the microgels is obtained. For the first time the change in optical properties by varying cross-linker density and temperature is directly related to the formation of dimers of gold particles, proven by SAXS.

Responsive Microgels at Surfaces and Interfaces

“…Beside this, there exists a large number of nanoparticle-microgel hybrids. Inorganic materials, like silica [51], titanium dioxide or metal nanoparticles [50], are incorporated into the gel network, either as core-shell particles or randomly distributed [25]. Thus, the hybrid material is an ideal combination of the responsive properties of the microgel and the catalytic or optical properties of the nanoparticle.…”

Review on synthesis, properties, characterization, and applications of responsive microgels fabricated with gold nanostructures

“…They observed that the loading of nanoparticles at pH 3 is greater than loading at pH 6, because p(2VP) microgels are cationic microgels and the size of microgel particles decreases with the increase in the pH of the medium. Gawlitza et al (2013) have reported the loading of Au nanoparticles within preformed p(NIPAM) microgels. They modulated the loading of Au nanoparticles by changing the cross-linking of p(NIPAM) microgels.…”

“…In this way, the attraction between acidic monomers and cationic surfactant ensure the loading of Au nanostructures within microgels. Many scientists have prepared hybrid microgels using this method (Pong et al 2006, Davies and Vincent 2010, Gawlitza et al 2013). Khan and Alhoshan (2013) have loaded cationic surfactant-stabilized Au nanoparticles into p(NIPAM-co-AAc) microgels.…”

“…The VPTT of hybrid microgels is greater than that of pure microgels. Gawlitza et al (2013) studied that the VPTT of [Au-p(NIPAM)] hybrid microgels is greater than that of p(NIPAM) microgels. Gorelikov et al (2004), Lee (2004, 2006), and many other scientists have reported the same results for Au-microgels.…”

Hydrophobic superparamagnetic FePt nanoparticles in hydrophilic poly(N-vinylcaprolactam) microgels: a new multifunctional hybrid system

“…8,18 In recent studies, microgels served as a template for in situ preparation of hybrid systems, in which the NPs were introduced into the microgel by diffusion of presynthesized NPs in homogeneous solution due to hydrophobic or electrostatic interactions. 22,26 In the majority of cases, the hybrid materials retain the stimuli responsiveness and their colloidal stability of the microgel. Nevertheless, the synthetic access to a microgel/NPs hybrid system is therefore dictated by the features of its constituents, in particular the polarity of the microgels and the NPs after synthesis, respectively.…”