In this work, we successfully synthesized different sizes of copper iron sulfide (CuFeS2) nanoparticles (NPs) using
a pulsed laser ablation technique in liquid (PLAL) with different ablation times. We evaluated the structure of
CuFeS2 NPs using experimental results obtained from high resolution transmission electron microscope (HR-
TEM), scanning electron microscope (SEM), energy dispersive x-ray (EDX), Fourier transform infrared (FTIR),
Raman spectroscopy, and UV–Vis spectroscopy. TEM images revealed that the CuFeS2 nanoparticles are shaped
like spheres and have an average size of 17.9 to 44.2 nm with ablation time ranging from 10 to 50 min. We used
EDX and mapping to examine the surface morphology and the percentage distribution of each element in the
prepared samples. FTIR measurements confirm the bonds between elements. Raman spectroscopy evaluates the
molecular structure, the molecule’s geometry, and even its symmetry. According to the samples’ UV–vis spectra,
the optical parameters were looked at. These included the optical absorption coefficient (α), band gap energy
(Eg), Urbach energy (Eu), refractive index (n), extinction coefficient (k), skin depth (δ), optical conductivity
(σopt), and dielectric constants (ε′, ε″). We found that as the particle size of CuFeS2 NPs increases, the direct
optical band gap decreases from 2.54 to 1.915 eV, while the Urbach energy increases from 1.64 to 3.11 eV. While
the Urbach energy increases, the electron–phonon interaction (Ee p) increases from 42.46 to 80.22, and the
steepness parameter (σ) decreases from 0.0157 to 0.00831. Furthermore, we observed an increase in the
refractive index, extinction coefficient, optical dielectric, and optical conductivity of CuFeS2 NPs. The prepared
CuFeS2 NPs have the potential to be crucial in optoelectronic and energy storage applications.