Impact of Temperature on the Fusion Growth of Bimetallic Au–Pt Nanoparticles from Each Nanocluster Conjugated with a Thermoresponsive Polymer

Abstract

Fusion growth from each nanocluster applying the random coil–globule transition of a thermoresponsive polymer was explored for alloy nanoparticle (NP) formation for the first time. The fusion growth of bimetallic Au–Pt alloy NPs was examined at 100, 150, and 200 °C via the structural collapse caused by the transition of a thermoresponsive polymer, poly(N-isopropylacrylamide). A significant temperature dependence was revealed in the formation path, even in the narrow range of reaction temperatures studied here. Structural investigations for the products were performed using transmission electron microscopy, energy-dispersive X-ray spectrometry, elemental mapping, X-ray absorption fine structure, and X-ray diffraction. At 100 °C, Au NPs slightly alloyed with Pt atoms rather than form neat Au NPs. The element ratio was determined to be Au:Pt = 12:1 or less of Pt atoms. Small Pt particles coated the surface of the central NPs. A nonmetallic component of Pt atoms was mainly detected in the product solution on ...