Real-time visualization of plasmonic nanoparticle growth dynamics by high-speed atomic force microscopy

TL;DR

This paper demonstrates real-time, in-situ visualization of silver nanoparticle growth at the single-particle level using high-speed atomic force microscopy combined with photoreduction, revealing growth dynamics and effects of laser intensity.

Contribution

It introduces a novel HS-AFM based method for real-time visualization of nanoparticle growth, enabling detailed analysis of growth mechanisms and dynamics.

Findings

Captured real-time movies of nanoparticle nucleation and growth

Revealed particle-to-particle variation in growth dynamics

Showed laser intensity influences growth rates

Abstract

Plasmonic nanoparticles generate strongly localized and enhanced light field through localized surface plasmon resonance, thereby playing a central role in plasmonics and nanophotonics. Because the optical properties of plasmonic nanoparticles are highly sensitive to their size and shape, nanoscale visualization of nanoparticle growth is crucial for detailed understanding of growth mechanisms and precise control of particle geometry. However, it is not possible to visualize the rapid growth dynamics using conventional imaging techniques. In this study, we demonstrate in-situ real-time observation of silver nanoparticle (AgNP) growth dynamics at the single-particle level using high-speed atomic force microscopy (HS-AFM). We employed a photoreduction method, which enables reliable control of AgNP formation by laser irradiation. By integrating a stand-alone tip-scan HS-AFM with an optical setup for photoreduction, we successfully captured real-time movies showing the nucleation and subsequent growth of AgNPs at the single-particle level. Furthermore, quantitative single-particle analysis revealed particle-to-particle variations in growth dynamics. The growth dynamics were further studied at different laser intensities, revealing intensity-dependent growth rates and the balance between nucleation and growth. This study establishes HS-AFM as a novel microscopic platform for in-situ visualization of plasmonic nanoparticle growth and will contribute to advances in plasmonics and materials science.