Environmental Engineering Reference
In-Depth Information
Chapter 12
Electron Magnetic Resonance (EMR)
Technique and Nanoparticle
Characterization
Ashutosh Kumar Shukla
Abstract This chapter summarizes the applications of Electron Magnetic Reso-
nance (EMR) spectroscopy for characterization of nanoparticle systems. It covers
review of reported recent research on EMR characterization of metallic
nanoparticles and metal oxyhydroxide/metal oxide nanoparticles which are impor-
tant for technological as well as biomedical applications. Photo generated charge
carriers in nanocrystalline materials as studied by EMR are also included in this
review. Efforts have been made to highlight open problems that need further
investigations.
12.1 Basic Features of EMR
Spectroscopy may be subdivided in different branches depending on the energy
involved [ 1 ]. Electron Magnetic Resonance (EMR) spectroscopy basically deals
with microwave region of electromagnetic radiation and it is based on the interac-
tion between electronic magnetic moments and magnetic field. Resonance absorp-
tion of microwave radiation by unpaired electron spins in a magnetic field is
observed in EMR. One studies the direct transitions between electronic Zeeman
levels in EMR spectroscopy. Zavoisky discovered EMR in 1945 for study of
transition metal ions in salts [ 2 ]. EMR spectra are usually characterized by the
spin Hamiltonian parameters and therefore rigorous EMR analysis requires quan-
tum mechanical concepts. Theory of EMR and its applications in various disci-
plines have been discussed in many monographs and review articles. EMR can be
used to study the samples with paramagnetic centers which are the sites with
unpaired electrons. The various parameters of EMR spectrum, viz. intensity, line
width, g value, and hyperfine splitting constant, provide variety of information
about the paramagnetic specimen. EMR can provide spectroscopic data on unpaired
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