**4. Conclusions**

When DI water contaminated with *E. coli* and *S. aureus* was subjected to Ag@ZnO core-shell nanoparticles mediated photocatalytic disinfection under sun-light radiation, complete disinfection of *E. coli* and *S. aureus* was achieved within 60 and 90 min respectively at 35 ◦C and in 45 and 60 min at 55 ◦C. Quantitative analyses of K<sup>+</sup> ion release and MDA assay proposed the damage of bacterial cell wall by ROS generated during solar photocatalysis. The disinfection profile for both the bacteria was validated using the Crick-Watson disinfection model. Disinfection achieved using the Ag@ZnO system was also validated for real world samples of municipal tap, pond and river water. When the nanocatalyst was recycled and reused for subsequent photocatalytic disinfection experiments, its efficiency did not change remarkably, even after three cycles. The reportted photocatalytic system may find applications in designing a portable water decontamination system for pathogen infested geographical locations.

**Acknowledgments:** This work was supported by Department of Science & Technology, Government of India (IFA12-ENG-37) and Swedish Research Council, Government of Sweden (Grant Number K2013-70X-20514-07-5).

**Author Contributions:** Suraj K. Tripathy created the original study plan. Sourav Das, Neha Ranjana and Ananyo Jyoti Misra designed and executed the disinfection experiments under the guidance of Suraj K. Tripathy. Amrita Mishra and Mrutyunjay Suar helped in the molecular biology experiments. Cecilia Stålsby Lundborg and Ashok J. Tamhankar reviewed and edited the manuscript. All authors read and approved the manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.
