Formation of gold nanoparticles in diblock copolymer micelles with various reducing agents Kinetic and thermodynamic studies

• Published in: Journal of thermal analysis and calorimetry Vol. 101; no. 3; pp. 865 - 872
• Main Authors: Papp, S., Kőrösi, L., Gool, B., Dederichs, T., Mela, P., Möller, M., Dékány, I.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-09-2010; Springer
• Subjects: Analytical Chemistry; Applied sciences; Calorimetry; Chemistry; Chemistry and Materials Science; Composites; Exact sciences and technology; Forms of application and semi-finished materials; Inorganic Chemistry; Measurement Science and Instrumentation; Nanoparticles; Physical Chemistry; Polymer industry, paints, wood; Polymer Sciences; Technology of polymers; Thermal properties; Thermodynamics; Diblock copolymer; Microcalorimetry; Micellar solution; Gold nanoparticles; Heat of nucleation; Atomic force microscopy; Gold; Nucleation; Nanoparticle; Micelle; Transition metal; Reducing agent; Surface structure; Transmission electron microscopy; Morphology; Thermodynamic analysis; Thermal analysis; Kinetics; Pyridine(vinyl) copolymer; Styrene copolymer
• ISSN: 1388-6150; 1588-2926; 1572-8943
• DOI: 10.1007/s10973-009-0570-x

Gold nanoparticles (Au NPs) were prepared by the reduction of HAuCl
4
acid incorporated into the polar core of poly(styrene)-
block
-poly(2-vinylpyridine) (PS-
b
-P2VP) copolymer micelles dissolved in toluene. The formation of Au NPs was controlled using three reducing agents with different strengths: hydrazine (HA), triethylsilane (TES), and potassium triethylborohydride (PTB). The formation of Au NPs was followed by transmission electron microscopy, UV–Vis spectroscopy, isothermal titration calorimetry (ITC), and dynamic light scattering (DLS). It was found that the strength of the reducing agent determined both the size and the rate of formation of the Au NPs. The average diameters of the Au NPs prepared by reduction with HA, TES, and PTB were 1.7, 2.6, and 8 nm, respectively. The reduction of Au(III) was rapid with HA and PTB. TES proved to be a mild reducing agent for the synthesis of Au NPs. DLS measurements demonstrated swelling of the PS-
b
-P2VP micelles due to the incorporation of HAuCl
4
and the reducing agents. The original micellar structure rearranged during the reduction with PTB. ITC measurements revealed that some chemical reactions besides Au NPs formation also occurred in the course of the reduction process. The enthalpy of formation of Au NPs in PS-
b
-P2VP micelles reduced by HA was determined.