Singlet oxygen photosensitizers have been proposed as tools for enhancing solar driven disinfection of water, with especially promising results for inactivation of viruses. In most systems a pseudo steady-state concentration of singlet oxygen can be determined and used to model disinfection outcomes using Chick-Watson kinetics and the contact-time concept. Some exceptional cases have been found, however, when cationic fullerene sensitizers were used; the observed inactivation kinetics for singlet oxygen produced by these materials were much more rapid than expected. The most likely explanation for the distinct rate coefficients—electrostatic attraction between sensitizers and viruses—is explored here by careful manipulation of solution parameters to promote or prevent virus-sensitizer agglomeration. MS2 bacteriophages were inactivated by aqueous aggregates of cationic-functionalized fullerenes to calculate the apparent coefficients of specific lethality for singlet oxygen against MS2 under different conditions. Rose Bengal was used as a reference photosensitizer which fully dissolved in solution. The pH and dissolved organic matter (DOM) content of experimental solutions were varied to test the electrostatic interactions hypothesis. Further, the results demonstrate the capacity for this mechanism to be leveraged to achieve targeted destruction of viruses and to overcome unwanted quenching by DOM in complex waters. The outlook for photosensitized disinfection technologies is discussed in the context of the many challenges facing photo-driven water treatment approaches.

Leveraging virus-particle interactions for achieving rapid photosensitized inactivation of viruses in complex waters

ACS Fall 2021

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