Gold nanoparticles (Au NPs) were prepared by the reduction of HAuCl4 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 HAuCl4 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.