Tetrahedrite (Cu12Sb4S13) and
famatinite (Cu3SbS4) are good candidates for
green energy applications because they possess promising thermoelectric
and photovoltaic properties as well as contain earth-abundant and
nontoxic constituents. Herein, X-ray photoelectron spectroscopy (XPS),
ultraviolet photoelectron spectroscopy (UPS), and electron paramagnetic
resonance spectroscopy (EPR) methods examined inherent electronic
properties and interatomic magnetic interactions of Cu-site doped
tetrahedrite and famatinite nanomaterials. An energy-efficient modified
polyol method was utilized for the synthesis of tetrahedrite and famatinite
nanoparticles doped on the Cu-site with Zn, Fe, Ni, Mn, and Co. This
is the first parallel study of tetrahedrite and famatinite nanomaterials
with XPS, UPS, and EPR methods alongside a systematic analysis of
dopant-dependent effects on the electronic structure and magnetic
interactions for each material. XPS showed that the Cu and Sb species
in tetrahedrite and famatinite possess different oxidation states,
while UPS characterization reveals larger dopant-dependent shifts
in the work function for tetrahedrite nanoparticles (4.21 to 4.79
eV) than for famatinite nanoparticles (4.57 to 4.77 eV). Finally,
all famatinite nanoparticles display an EPR signal, indicating trace
amounts of paramagnetic Cu(II) present below the detection limit of
XPS. For tetrahedrite, EPR signatures were observed only for the Zn-doped
and Mn-doped nanoparticles, suggesting signal broadening from Cu–Cu
spin exchange or spin–lattice relaxation. This study demonstrates
the complementary nature of XPS and EPR techniques for studying the
oxidation states of metals in solid-state nanomaterials. Comparing
the electronic and magnetic properties of tetrahedrite and famatinite
while studying the impact of dopant incorporation will guide future
endeavors in designing sustainable, high-performance materials for
renewable energy applications.