On-Tip Polymerization Method for Multimodal Characterization of Nanoparticles with Electron/Ion Imaging and Atom Probe Tomography.

Abstract

This work presents a novel method for exploring the structures and chemistry of nanoparticles (NPs), addressing challenges in multimodal and correlative microscopy analysis. The proposed method utilizes a "needle-eye" design, featuring a through-microchannel fabricated at the needle tip. The microchannel and its surface are tuned via focused ion beam (FIB) milling and plasma treatment, enabling NPs dispersed in a resin precursor to be confined in the microchannel due to a pressure gradient upon immersion. The retained suspension is promptly polymerized in situ on the tip and shaped by FIB milling into specific geometries, including but not limited to a micropillar, lamella, and nanoneedle. Here, to demonstrate its applicability, a mixed metal oxide catalyst prepared by the needle-eye approach is characterized with energy-dispersive X-ray spectroscopy (EDX), FIB secondary ion mass spectrometry (FIB-SIMS), (scanning) transmission electron microscopy ((S)TEM), and atom probe tomography (APT). The results validate the ability of the method to achieve multimodal, combining correlative and complementary high-resolution structural and chemical imaging of individuals and clustered NPs. The proposed method confines picoliter-scale samples (6-60 pL) at a tip, eliminating lift-out and microtomy while enabling comprehensive analysis via combined microscopy techniques.