Broad spectrum antimicrobial coatings comprising combinations of organosilanes

A method of forming an antimicrobial coating on a surface, the method comprising:

• (a) applying an aqueous antimicrobial coating composition to the surface, the aqueous antimicrobial coating composition comprising:
• (i) a mixture from about 0.1 wt. % to about 1.0 wt. % of dimethyloctadecyl[3-(trihydroxysilyl)propyl]ammonium chloride (DMOD), 3-chloropropyltrimethoxysilane (CPTMS), and from about 2.5 wt. % to about 12.5 wt. % 3-aminopropyltriethoxysilane (APTES) in water;
• and
• (ii) optionally, at least one organic amine having a structure R9R10R11N, wherein R9, R10, and R11 are independently H, alkyl, substituted alkyl, aryl, substituted aryl or cyclic, having a molecular weight of less than about 200 g/mole and a pKa of from about 7 to about 12;
• and
• (b) allowing the aqueous antimicrobial coating composition to dry on the surface under ambient conditions, or drying the aqueous antimicrobial coating composition on the surface under heated conditions, to form the antimicrobial coating on the surface;
• wherein the aqueous antimicrobial coating composition, prior to applying to the surface, exhibits an absorbance at 600 nm of less than about 0.2 after 4-weeks of ambient storage.