Novel method for Ag colloidal cluster formation by laser ablation at the air–liquid interface

Abstract

We report a novel method for formation of sub-nanoclusters by laser ablation at the air-liquid interface. The density of plasma induced by laser ablation at the air-liquid interface should be lower than that produced by laser ablation in liquid. In the lower density plasma, the produced clusters rarely grow or aggregate into larger clusters because the collision probability is low, resulting in the formation of small clusters. Ag sub-nanoclusters were observed by electrospray ionization mass spectrometry (ESI-MS) and X-ray photoelectron spectroscopy (XPS). These results show that lowdensity plasma can be applied to small-cluster formation and that laser ablation at the air-liquid interface produces a good reactive field for the formation of sub-nanoclusters. Our results highlight the importance of low-density plasma induced at the air-liquid interface for sub-nanocluster formation.

Electrochemical Water Oxidation Catalysed by CoO‐Co2O3‐Co(OH)2 Multiphase‐Nanoparticles Prepared by Femtosecond Laser Ablation in Water

“…The size distributions of nanoparticles prepared by laser ablation in liquid are generally broad although fabrication of very small or monodispersed nanoparticles have been recently reported ,,. The STEM images obtained in the present work demonstrate that the ablation produced CoO nanoparticles with nearly uniform sizes (Figure and S2).…”

“…Therefore, surfactant‐free clusters and nanoparticles are also desired for deposition on substrates, as this would remove the need for calcination to remove the surfactants and avoid particle size increases. Colloidal nanoparticles without surfactants have been generated by laser ablation in liquid, and various materials in the size range from sub‐nanometer to sub‐micrometer have been fabricated in this manner. Surfactant‐free nanoparticles obtained by laser ablation in liquid are known to exhibit high catalytic activity and modified functions that differ from those of chemically‐synthesized nanoparticles.…”

Low-Overpotential Electrochemical Water Oxidation Catalyzed by CuO Derived from 2 nm-Sized Cu2(NO3)(OH)3 Nanoparticles Generated by Laser Ablation at the Air–Liquid Interface

“…Cu-based nanoparticles have been synthesized by various methods; ,− however, although monodispersed nanoparticles have been fabricated, Cu-based nanoparticles with sizes as small as those in the present study have not been reported. The mechanism to produce these very small nanoparticles has been discussed as below. , In the case of LAL, a high density plasma is produced because the expansion of the plasma induced by LAL is confined by the liquid (confinement effect) unlike the free expansion in a vacuum, − which results in a high collision possibility. As a result, the small excited species such as ions, clusters, and nanoparticles can easily grow into larger particles.…”

“…Immediately after LAL, LAAL using the colloidal target was conducted to form monodispersed small nanoparticles (LAAL-Cu). The detailed experimental setup for LAAL is described elsewhere. , A draft chamber is required during LAAL experiment, because aerosol is possibly produced by LAAL. The colloidal target was introduced to a measuring flask and was then irradiated with second harmonic light from a Nd:YAG laser system (800 mJ/pulse, 10 Hz) through a quartz lens with a focal length of 200 nm.…”

“…LAAL reduced the nanoparticle size and stabilized the colloid as previously reported. 35,36 Figure 2a−c shows the SEM images of raw Cu target powder and LAL-Cu nanoparticles and an STEM image of the LAAL-Cu nanoparticles. SEM observations revealed a size reduction from ∼100 μm to less than 1 μm induced by LAL.…”