The H-type Nb2O5 powders (monoclinic structure with (101) crystallographic shear plane) submicron to micrometers in size were subjected to pulsed laser ablation fragmentation in water (PLAL) with optional NaCl addition in order to study the structure change of the resultant Nb2O5 nanoparticles by x-ray diffraction and electron microscopy. The Nb2O5 nanoparticles via such a dynamic PLAL fragmentation process turned out to be H-type relic and newly formed T-type (an orthorhombic high-pressure phase), TT-type (a pseudohexagonal high-pressure phase) and a nonstoichiometric amorphous phase which coexist within a faceted nanoparticle (down to ca. 5 nm) or coalesced with each other. The composite Nb2O5 nanoparticles were protonated and imposed with a considerable internal compressive stress to modify the structure units and band structure as indicated by vibrational (Raman and FTIR) spectra and uv-visible absorption spectrum of the darkened colloidal solution indicating a stepwise minimum band gap lowering down to stepwise 3.0¡Ó0.1 eV and 2.5¡Ó0.1eV. NaCl spiking in water did not cause appreciable change on the phase behavior of Nb2O5 powders upon PLAL.