Disinfection of water, plants, skin and wounds is critical for public health, horticulture, and medicine. Current disinfection methods are relatively expensive, large in size and complexity, and typically require toxic chemicals. Plasma-generated reactive oxygen and nitrogen species (ROS/RNS) in air or other gases at or near room temperature are known to have antimicrobial and other biological and materials processing activity through direct interactions or indirectly via liquid phase applications. However, these methods currently have serious limitations to broader applications.To address this challenge, University of California investigators have developed improved antimicrobial atmospheric pressure plasmas. These new antimicrobial atmospheric pressure plasmas significantly enhance the efficacy of currently available systems by combining these species with a separate source of photons. In particular, ultraviolet (UV) photons have been shown by the investigators to greatly increase the antimicrobial effectiveness of plasma-generated ROS/RNS. These antimicrobial atmospheric pressure plasmas can be used for water, surface, skin and wound disinfection. The improved antimicrobial atmospheric pressure plasmas create chemically active species in gases or standard atmospheric pressure plasmas with photons, such ultraviolet wavelengths. These improved antimicrobial atmospheric pressure plasmas combines the open-gas atmospheric pressure plasma to generate radicals and other reactive species with separate photon sources, such as LEDs, to generate UV and visible wavelength photons to interact synergistically with the chemical radicals. This combination results in novel power and control for important applications exploiting reactive chemical species. Additionally, these improved antimicrobial atmospheric pressure plasmas use relatively inexpensive and simple devices, relatively small amounts of electricity, air and water. The chemical species created are relatively innocuous.