Experimental determination of conduction and valence bands of semiconductor nanoparticles using Kelvin probe force microscopy

The ability to determine a semiconductor's band edge positions is important for the design of new photocatalyst materials. In this paper, we introduced an experimental method based on Kelvin probe force microscopy to determine the conduction and valence band edge energies of semiconductor nanomaterials, which has rarely been demonstrated. We tested the method on six semiconductor nanoparticles (α-Fe₂O₃, CeO₂, Al ₂O₃, CuO, TiO₂, and ZnO) with known electronic structures. The experimentally determined band edge positions for α-Fe₂O₃, Al₂O₃, and CuO well matched the literature values with no statistical difference. Except CeO ₂, all other metal oxides had a consistent upward bias in the experimental measurements of band edge positions because of the shielding effect of the adsorbed surface water layer. This experimental approach may outstand as a unique alternative way of probing the band edge energy positions of semiconductor materials to complement the current computational methods, which often find limitations in new synthetic or complex materials. Ultimately, this work provides scientific foundation for developing experimental tools to probe nanoscale electronic properties of photocatalytic materials, which will drive breakthroughs in the design of novel photocatalytic systems and advance the fundamental understanding of material properties.