Surface functionalization of silica or maghemite (gamma-Fe2O3) nanoparticles with a quaternary ammonium organosilane leads to ionically modified nanoparticles that, depending on the nature of the counterion, exhibit liquid-like behavior in the absence of solvents. Solvent-free nanosalts composed of modified silica nanoparticles (Figure, left) can be used to dissolve and polymerize pyrrole, while nanosalts composed of maghemite nanoparticles (right) can form solvent-free ferrofluids.