Substrate-free copper nanoclusters exhibit super diamagnetism and surface based soft ferromagnetism

Area of Science:

• Materials Science
• Nanotechnology
• Condensed Matter Physics

Background:

• Metallic copper nanoparticles (Cu NPs) are of interest due to their unique properties.
• Synthesizing substrate-free Cu NPs is challenging but crucial for fundamental studies.
• Understanding the magnetic behavior of nanoclusters is key to unlocking new applications.

Purpose of the Study:

• To synthesize pure, substrate-free metallic copper nanoparticles.
• To characterize the structure and physical properties of the synthesized Cu NPs.
• To investigate the magnetic properties, including diamagnetism and ferromagnetism, of copper nanoclusters.

Main Methods:

• Thermo-chemical reduction of copper acetate using triethanolamine (TEOA).
• Physicochemical analysis including Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), MALDI, Electron Paramagnetic Resonance (EPR), and magnetization studies.
• Density Functional Theory (DFT) calculations for structural prediction.

Main Results:

• Successfully synthesized substrate-free metallic Cu NPs (3-5 nm) with significant agglomeration.
• Identified a Cu9 structure for the nanoclusters, supported by experimental data and DFT.
• Observed giant diamagnetism (29-39 times larger than atomic values) and two ferromagnetic transitions at ~40 K and ~100 K.
• Surface properties, potentially CuO or TEOA residues, contribute to soft room-temperature ferromagnetism.

Conclusions:

• This study reports the first experimental observation of giant diamagnetism in substrate-free metallic copper nanoclusters.
• The findings suggest that surface effects play a significant role in the magnetic properties of copper nanoclusters.
• The unique magnetic properties of these Cu NPs open avenues for novel applications in nanotechnology and materials science.