A range of Bi-impregnated TUD-1-type mesoporous silicas have been prepared using the structure directing agent triethanolamine (TEA), with bismuth loadings ranging from 25 wt% to o0.001 mol%.These silicas have been characterized by surface area, pore size, pore volume, Raman spectroscopy, IR spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and ICP-AES. During the gelation phase the bismuth chemistry varies with its concentration and it is possible to prepare atomically dispersed as well as highly uniform nanoparticulate bismuth oxide that can be well characterised.Diffuse reflectance UV-Vis spectrophotometry was used to determine the band gap of the bismuth oxide nanoparticles and unprecedented blue shifts (due to quantum confinement) as compared to bulk a-Bi 2 O 3 , were observed with the maximum band gap observed being 5.17 eV.