Polymer-Shell Coating of Mie-Resonant Silicon Nanospheres for Controlled Fabrication of Self-Assembled Monolayer

TL;DR

This paper presents a method to coat silicon nanospheres with a thermoresponsive polymer shell, enabling control over their optical properties and self-assembly into monolayers with tunable interparticle distances.

Contribution

Developed a process to coat silicon nanospheres with a thermoresponsive hydrogel shell, controlling optical resonance and enabling self-assembly into ordered monolayers.

Findings

PNIPAM shell thickness can be controlled by hydrodynamic diameter.

Shell thermoresponsive behavior affects Mie resonance.

Self-assembled monolayers with tunable interparticle spacing.

Abstract

A polymer shell offers a unique opportunity to tailor structural and optical properties of optically functional nanoparticles and their ensembles. Here, we develop a process to coat Mie-resonant silicon nanospheres (Si NSs) with a thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) hydrogel shell. We show formation of a PNIPAM shell of controlled thickness from the change of the hydrodynamic diameter and study the effect of thermoresponsive shrinkage and expansion of the shell on the Mie resonance of a Si NS. We then demonstrate that Si NSs with PNIPAM shells enable fabrication of cluster-free, self-assembled monolayers of Si NSs, in which distances between NSs are controlled by the PNIPAM shell thickness.