Abstract
Assemblies of nanoparticles are studied in many research fields from physics to medicine. However, as it is often difficult to produce mono-dispersed particles, investigating the key parameters enhancing their efficiency is blurred by wide size distributions. Indeed, near-field methods analyse a part of the sample that might not be representative of the full size distribution and macroscopic methods give average information including all particle sizes. Here, we introduce temperature differential ferromagnetic nuclear resonance spectra that allow sampling the crystallographic structure, the chemical composition and the chemical order of non-interacting ferromagnetic nanoparticles for specific size ranges within their size distribution. The method is applied to cobalt nanoparticles for catalysis and allows extracting the size effect from the crystallographic structure effect on their catalytic activity. It also allows sampling of the chemical composition and chemical order within the size distribution of alloyed nanoparticles and can thus be useful in many research fields.
Highlights
Assemblies of nanoparticles are studied in many research fields from physics to medicine
We propose the concept of temperature differential ferromagnetic nuclear resonance (FNR) (TDFNR) spectra, which allows evaluation of the number of atoms involved in specific size ranges within the size distribution of non-interacting ferromagnetic nanoparticles and, at the same time, allows the sampling of the crystallographic structure and chemical composition as a function of the size of the nanoparticles
This is not usually performed in FNR because the signal scales with the inverse of the measurement temperature (1/T; nuclear spins are paramagnets), and because measuring at high temperature might lead to a loss of information
Summary
Assemblies of nanoparticles are studied in many research fields from physics to medicine. The method is applied to cobalt nanoparticles for catalysis and allows extracting the size effect from the crystallographic structure effect on their catalytic activity It allows sampling of the chemical composition and chemical order within the size distribution of alloyed nanoparticles and can be useful in many research fields. We propose the concept of temperature differential FNR (TDFNR) spectra, which allows evaluation of the number of atoms involved in specific size ranges (and the resulting number of particles) within the size distribution of non-interacting ferromagnetic nanoparticles and, at the same time, allows the sampling of the crystallographic structure and chemical composition as a function of the size of the nanoparticles. This shows that the method can have a wide field of applications spreading far beyond the fields investigated in the present work
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