These are cobalt ferrite nanoparticles, and in the literature, their band gap is reported to be around 2 eV, meaning they are semiconductors.Also when I calculate the band gap of the composite with PP (polypropylene), I obtain values typical of dielectrics (3 eV or more).What could be the reason for this?
Hi, i train AI, please check its answer, it can be useful sometimes: Yes, the apparent increase in band gap in your nanocomposite with higher cobalt ferrite (CoFe₂O₄) content can occur — but not because the intrinsic band gap of the nanoparticles increases. Rather, this is likely due to optical domination by the polymer matrix (PP) and changes in dispersion state.
Some key factors:
Matrix effect: Polypropylene is a wide-band-gap dielectric. At low or even moderate filler loadings, the absorption edge of the composite reflects mostly the PP, especially if nanoparticles are not well percolated or homogeneously dispersed.
Nanoparticle aggregation at high loading: Higher concentration often leads to aggregation, reducing the effective surface area and altering the interaction with light. This can shift the absorption onset, giving the illusion of a higher band gap.
Measurement artifacts: If you’re using UV-Vis and Tauc plots, the results strongly depend on how the baseline and linear region are chosen. Aggregates can cause light scattering, skewing the spectrum and leading to an overestimated band gap.
Quantum confinement: If the nanoparticles are very small (
Ordinarily, pristine polypropylene polymer has a larger band gap than the nanocomposite formed with cobalt ferrite nanoparticles. This difference may be due to interfacial interactions, surface bonding, and dipole interference within the composite structure. Optimizing the amount of cobalt ferrite (CoFe₂O₄) nanoparticles added is crucial, excessive nanoparticle content relative to the polymer can lead to a dilution effect. Additionally, the synthesis method must be optimized. Exploring alternative dispersion and characterization techniques may help control the growth and distribution of the CoFe₂O₄ nanoparticles as well as give better resolution as well as check dispersion quality and (CoFe₂O₄) nanoparticle size using other techniques if available. They include (TEM, DLS,SEM, XPS)
Nushaba Gadirova
Band gap: The study showed that at low concentrations (up to 5%), the band gap increased, which is due to the increase in quantum size and the increase in the density of states. At high concentrations: At levels of 10% and above, a decrease in the band gap was observed. This is due to the agglomeration of nanoparticles, which led to the formation of larger structures, as well as increased electron interactions between particles, which reduced the overall gap.
Article Optical properties and radiation stability of polypropylene ...
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