Inorganic antimicrobial coatings usually possess a longer duration to most chemicals and mechanical abrasion (e.g., scrubbing and regular cleaning) than their organic counterparts. Yet many of the well-recognized inorganic antimicrobial coatings are either too thick to be transparent or too intense in color (e.g. Cu, Ag, or stainless steel surfaces). In this regard, metal oxide-based ultra-thin coatings are a reasonable choice to afford high stability and transparency toward antimicrobial coatings.