Plasmon Tuning of Liquid Gallium Nanoparticles through Surface Anodization.

Chih-Yao Chen,I-Chen Chen,Ching-Yun Chien,Chih-Ming Wang,Rong-Sheng Lin

doi:10.3390/ma15062145

Abstract

In this work, tunable plasmonic liquid gallium nanoparticles (Ga NPs) were prepared through surface anodizing of the particles. Shape deformation of the Ga NPs accompanied with dimpled surface topographies could be induced during electrochemical anodization, and the formation of the anodic oxide shell helps maintain the resulting change in the particle shape. The nanoscale dimple-like textures led to changes in the localized surface plasmon resonance (LSPR) wavelength. A maximal LSPR red-shift of ~77 nm was preliminarily achieved using an anodization voltage of 0.7 V. The experimental results showed that an increase in the oxide shell thickness yielded a negligible difference in the observed LSPR, and finite-difference time-domain (FDTD) simulations also suggested that the LSPR tunability was primarily determined by the shape of the deformed particles. The extent of particle deformation could be adjusted in a very short period of anodization time (~7 s), which offers an efficient way to tune the LSPR response of Ga NPs.

Highlights

Plasmonics has emerged and drawn much attention over the past decade due to its capabilities for the manipulation of electromagnetic radiation and enhancement of light–matter interactions [1–5]
Since diffusion-limited ripening dominates in the ensemble formation at room temperature, an ensemble consisting of larger gallium nanoparticles (Ga NPs) surrounded by smaller ones was observed
61.4 nm and the other corresponded to a significant number of small Ga NPs formed during the coarsening process

Summary

Introduction

Plasmonics has emerged and drawn much attention over the past decade due to its capabilities for the manipulation of electromagnetic radiation and enhancement of light–matter interactions [1–5]. The noble metals gold (Au) and silver (Ag) have been the most popular materials used in plasmonics. Localized surface plasmon resonances (LSPRs) arising in these NPs are basically restricted to the visible or near infrared spectral region because of the inherent limitations associated with their electronic structures [11]. Liquid gallium (Ga) has emerged as an alternative plasmonic material since it exhibits nearly free electron-like Drude behavior over a broad bandwidth from the ultraviolet to the infrared region [12]. Liquid Ga NPs possess attractive properties including excellent chemical stability by the self-terminating native oxide shell and ease of processing by various approaches [13], making them promising candidates for different applications such as surface-enhanced Raman scattering (SERS) [14,15], solid– liquid phase change memories [16], waveguiding [17], ellipsometric biosensing [18,19], and plasmon-based catalysis [20]

Methods

Results

Conclusion