A study beyond laser fluence threshold on WO3nanoparticle, employing pulsed laser ablation in liquid

We introduce the pulsed laser ablation in liquid (PLAL) approach in this study to synthesize tungsten oxide nanoparticles suspended in double die ionized water (DDIW). Several laser fluences of a Nd:YAG laser's second harmonic (532 nm) were used for the ablation at 109, 129, 149, 169, and 189 J/cm2, respectively. X-ray pattern showed polycrystalline structure with preferred orientation at (220) plane corresponding to 58.7° diffraction angle. The optical bandgap energy was found to increase as the laser fluence increases from 2.83 to 3.21 eV, with the increase in the laser fluence up to 189 J/cm2, respectively. The calculated optical bandgaps and the results from photoluminescence are in very good agreement. This work shows that there is a laser fluence threshold beyond which the Brus equation does not take place; this means at a specific laser fluence the energy gap of the prepared nanomaterial increases with laser fluence instead of decreasing as known in all published articles.