Both DEQ series and GC series are prepared by a green and environmentally friendly process, avoiding the use of highly toxic quaternization agents - methyl chloride and dimethyl sulfate. DEQ and GC have such excellent performance as bactericidal/antibacterial properties, good compatibility with other bactericides, good solubility in water, light and thermal stability. Studies showed that these quaternary ammonium salts have excellent killing ability against novel coronavirus (covid-19), thus can be used to formulate detergent products with bactericidal/antibacterial properties, or disinfection products in the daily life/healthcare, or various industrial fields. Due to no corrosion to metals, free-chlorine quaternary ammonium salts can also be applied in sterilization of metal objects.