Fabrication of organic shell-covered gold nanospheres with near-infrared absorption

A simple protocol is developed for the fabrication of stable organic shell-covered gold nanospheres with near-infrared absorption characteristics. The designed strategy mainly concentrates on two steps: (i) the polymerization of gold nanoparticles (AuNPs) induced by 1,2-ethanedithiol in water/ethanol; (ii) conjugation of the polymerized AuNPs with marocyclic compound for the formation of the organic shell. In the first step, the 1,2-ethanedithiol containing two thiols towards both ends of the chain enables the successful polymerization of AuNPs due to the forceful appetency of thiols to AuNPs. In the second step, the polymerized AuNPs are covered by the marocyclic compound attributing to the hydrogel-bonding effect between NH and SH. Because of the organic shell, the stability and dispersibility of the obtained nanospheres are improved. The optical properties of the fabricated gold nanospheres (400 nm average diameter) are well investigated by the UV-vis absorption spectroscopy which exhibit intense near-infrared absorption at 972 nm in acetone. The strategy developed in this study is promising in that excellent stability and dispersibility of gold nanospheres can be achieved in a facile and economic way.