The present invention relates in one aspect to the discovery of novel mesoporous silica nanoparticles (MSNs) templated around and comprising benzalkonium chloride (BAC). In certain embodiments, the BAC-SiO2 mesoporous nanoparticles are capable of sustained release of BAC under acidic conditions, thereby acting as a long release antimicrobial agent. In other embodiments, the BAC-SiO2 mesoporous nanoparticles can be incorporated into a variety of consumer products as an antimicrobial agent additive, including for example, but not limited to, surgical dressings, bandages, deodorants, soaps, facial cleansers and industrial cleaners.