Nanoenergetic gas-generator (NGG) mixtures may have various potential military applications from aircraft fuels to rocket propellants, explosives, and primers. To find reactions generating the highest pressure peak, we studied eight nanoenergetic reactions. The Al/Bi(2)O(3) reaction generated the highest pressure pulse among the eight thermite reactions. We developed a highly efficient, one step process for synthesis of Bi(2)O(3) nanostructured particles. Its use generated about a three times higher peak pressure (similar to 10 MPa) than when using commercial bismuth oxide nanoparticles (3 MPa). The pressure in the vessel rose very rapidly to a peak value for a duration of similar to 0.02 ms and Delta P/Delta t of up to 500 GPa s(-1). Increasing the crystallinity of the bismuth oxide nanoparticles increased the peak gas pressure by 25%. The maximum pressure x volume (PV) value obtained at m = 0.1 g with our synthesized Bi(2)O(3) was 707 Pa m(3) much higher than that reported in the literature (33 Pa m(3)) for the same sample mass. Addition of carbon to the reactant mixtures did not increase the peak pressure. Addition of up to 3 wt.-% of boron to the thermite systems increased the peak pressure by similar to 50%.