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

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2018-12, Vol.14 (51), p.e1803589-n/a
• Main Authors: Thies, Sabrina, Simon, Paul, Zelenina, Iryna, Mertens, Luc, Pich, Andrij
• Format: Article
• Language: English
• Subjects: Acrylic acid; Chemical synthesis; Chloroauric acid; Dispersion; Gold; gold nanoparticles; Localization; Microgels; Nanoparticles; Nanotechnology; Nucleation; Reagents; Reduction; Seeds; seed‐growth
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201803589

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. The in situ synthesis of single gold nanoparticles (AuNPs) in microgels (MGs) and their controlled symmetric and asymmetric growth is reported in a novel method. The obtained biocompatible hybrid poly(N‐vinylcaprolactam) (PVCL) MGs with a diameter dTEM of 115 nm, containing single AuNPs with tunable sizes in the core, are a promising flexible system for application in optics, catalysis, and biomedicine.