writer：Han Lin, L.P. Song, Youju Huang,* Q. Cheng, Y.P. Yang, Zhiyong Guo,* F.M. Su, and Tao Chen*
keywords：core?shell structure, 2D monolayer ?lm, superlattice, plasmonic switching, dual responsive
source：期刊
specific source：ACS Appl. Mater. Interfaces 2020, 12, 11296?11304
Issue time：2020年
The self-assembled gold nanoparticle (NP) superlattice displays unusual but distinctive features such as high mechanical and freestanding performance, electrical conductivity, and plasmonic properties, which are widely employed in various applications especially in biological diagnostics and optoelectronic devices. For a two-dimensional (2D) superlattice monolayer ?lm composed of a given metal nanostructure, it is rather challenging to tune either its plasmonic properties or its optical properties in a reversible way, and it has not been reported. It is therefore of signi?cant value to construct a free-standing 2D superlattice monolayer ?lm of gold nanoparticles with an intelligent response and desired functions. Herein, we developed an easy and e?cient approach to construct a gold nanoparticle superlattice ?lm with a dual-responsive plasmonic switch. In this system, gold nanoparticles were coated by polyaniline (PANI) and then interracially self-assembled into a monolayer ?lm at the air?liquid interface. The PANI shell plays two important roles in the superlattice monolayer ?lm. First, the PANI shell acts as a physical spacer to provide a steric hindrance to counteract the van der Waals (vdW) attraction between densely packed nanoparticles (NPs), resulting in the formation of a superlattice by adjusting the thickness of the PANI shell. Second, the PANI shells provide the superlattice ?lm with multiple stimuli such as electrical potential and pH change, leading to reversible optical and plasmonic responsiveness. The superlattice monolayer ?lm can show a vivid color change from olive green to pink, or from olive green to violet by the change of the corresponding stimuli. Also, the localized surface plasmonic resonance (LSPR) of the superlattice monolayer ?lm can be reversibly modulated by both by changing the local pH and applying an electric potential. Notably, a signi?cant plasmonic shift of 157 nm can be achieved in the superlattice monolayer ?lm when the PANI shell with a thickness of 35 nm and gold nanorods as a core were used. The superlattice monolayer ?lm with dualresponsive plasmonic switches is promising for a range of potential applications in optoelectronic devices, plasmonic and colorimetric sensors, and surface-enhanced Raman scattering (SERS).