Efficient photocatalytic inactivation of E. coli by Mn-CdS/ZnCuInSe/CuInS₂ quantum dots-sensitized TiO₂ nanowires

A novel visible light-driven photocatalyst (represented as Mn-CdS/ZCISe/CIS/TiO₂) for the passivation of E. coli was prepared with TiO₂ nanowires as support and using CuInS₂ (CIS) and ZnCuInSe (ZCISe) quantum dots (QDs), as well as Mn-doped CdS (Mn-CdS) nanoparticles (NPs) as sensitizers. The use of CIS and ZCISe QDs and Mn-CdS NPs extends the light harvest region to visible light. The photoelectric conversion efficiency was consequently improved, with a photocurrent density of 12.5 mA cm^-2, about 60 times that of pure TiO₂ nanowires. The germicidal efficiency of the photocatalyst was assessed by passivation of E. coli, 96% bacteria in 50 ml 10⁵ colony forming units (CFU) ml^-1 solution were killed within 50 min. Besides the high efficiency, the composite has good stability and satisfactory recycling performance. The antibiotic mechanism was also performed by using photoluminescence and a scavenging agent of different active matter, revealing that the photo-generated holes play a major role in the sterilization process.