Bandgap tuning of pseudoboehmite nanoparticles induced by quantum confinement

In this work we report the bandgap tuning of pseudoboehmite achieved by high energy ball milling. The milling process of pseudoboehmite was performed using a SPEX 8000 mill for of up to 10 h. Pseudooehmite powders were characterized before and after milling by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS). XRD results confirmed that the pseudoboehmite structure is preserved for 10 h of milling. The crystallite size of pseudoboehmite was estimated by Scherer equation, observing a constant increase with milling time from 2.72 nm to 3.18 nm. The pseudobohemite has a reduction in d-spacing with milling in the “c-axis”, but an enlargement in the “a-b directions”. The “c-axis” modification is due to water release, while the “a-b-plane” enlargement is attributed to cold welding during milling. The XPS and EELS analyses demonstrated a bandgap tuning effect from 7.11 eV to 6.20 eV in the raw and milled pseudoboehmite for 10 h. The results were demonstrated analytically.