Disinfection using the short-wavelength Ultra-Violet (the UVC, 200-280 nm) has been known for over a century but is gaining increasing popularity in these years thanks to the combined effect of the COVID19 pandemic outbreak, the stronger emerging of antibiotic resistant bacteria, and the availability of new compact LED sources in replacement for the traditional mercury vapor lamps, which are being banned for their toxic mercury content. UVC irradiation can be exploited both for its direct damaging action on the bacteria RNA or DNA and for its indirect mechanism, the so-called Photo-Dynamic Therapy (PDT), in which it triggers the generation of cytotoxic Reactive Oxygen Species (ROSs) from a non-toxic photosensitizer (PS).