In Situ Growth and Size Regulation of Single Gold Nanoparticles in Composite Microgels

Abstract

Herein, a novel method for the in situ growth of single gold nanoparticles (AuNPs) in microgel (MG) networks is presented. The key feature in this approach is the localization of β‐diketone groups capable of both complexation and reduction of aurate ions in the MGs’ core, which allows localization of the nucleation and growth of single AuNPs. The MG synthesis is carried out via precipitation polymerization in water with N‐vinylcaprolactam as the main monomer and with the two comonomers acetoacetoxyethyl methacrylate (AAEM) and acrylic acid (AAc), where AAEM is mainly located in the MGs’ core and AAc in their shell. For the synthesis of AuNPs, a certain amount of chloroauric acid (HAuCl4) is added to the dispersion, followed by fast reduction with sodium borohydride (NaBH4). In situ synthesized AuNPs in MGs possess a spherical shape, with a diameter of 8.1 ± 0.8 nm, being localized in the center of every MG. In addition, these AuNPs embedded into MG networks can be used as seeds that grow in their size after the addition of HAuCl4 up to 46.0 ± 9.5 nm under mild reaction conditions (room temperature, aqueous dispersion) and without the use of any additional reducing and stabilizing agents.

Recent advances in stimuli-responsive core-shell microgel particles: synthesis, characterisation, and applications

“…By localising beta-diketone groups capable of complexing and reducing aureate ions in the core of core-shell microgel particles, Thies et al managed to grow individual gold NPs in each core [71]. Moreover, they used these particles as a seed for further growth, with anisotropic rod-like shapes at high ionic concentrations, and avoiding the formation of secondary gold nuclei.…”

AuNPs as an important inorganic nanoparticle applied in drug carrier systems

“…Gold nanospheres (AuNSs), which have received the most attention due to the ease of their synthesis, are AuNPs in the form of spheres [53]. The most common method for synthesizing spherical AuNPs is based on the nucleation and growth process of citrate reduction of HAuCl 4 in aqueous solution [54]. However, this approach has certain limitations such as cytotoxicity and long duration.…”

Anisotropic mesoporous silica/microgel core–shell responsive particles

“…4,7,10,11 By polymerising PNIPAM around an organic or inorganic core, core-shell structures can be obtained. As a few examples, PNIPAM microgel shells have been polymerised around another microgel, 12 a polystyrene latex core, 13,14 gold 15,16 and silica 15 particles. Core-shell microgels are versatile systems that combine the properties of the different constituents offering for instance appealing catalytic 14,17 or optical properties 18 related to the conformational control of the surrounding microgel shell with the temperature.…”