Light-activated titanium dioxide crystals completely degrade DNA-related molecules in water tests

The test behind that result used molecules related to DNA, added to water along with the catalyst ^[5]. The phys.org account of the Chem Catalysis study ^[1] does not report the light source, the concentrations, the reaction time or how a sample without catalyst fared.

The choice of stand-in matters because of the hazard the authors describe. UV light and similar treatments kill bacteria but leave their DNA behind in the water ^[6]. "The persistence of this genetic material is an environmental concern because extracellular DNA can be taken up by other microorganisms, potentially leading to the spread of antibiotic resistance," said co-author Boxia Liu of North Minzu University in China ^[7][14]. To get from degraded DNA-like molecules to resistance genes that can no longer spread, the team would need tests on intact genes, with a microbe present that could take them up.

The chemistry is on firmer ground. The paper's title describes direct non-radical oxygen activation on facet-engineered oxide surfaces for selective photocatalytic oxidation ^[12], and the defects in the crystals were designed in ^[3]. "Catalyst defects should not simply be considered as imperfections in a material structure," said co-author Zhi Song, also of North Minzu University ^[9][14]. "When properly engineered, defects can actively regulate how molecules interact with catalyst surfaces and determine the pathways through which chemical reactions proceed," Song said ^[9].

Singlet oxygen, a much more reactive form of the triplet oxygen in ordinary air ^[2], is drawn to electron-rich molecules in general, and DNA base pairs are one kind ^[4]. In a test where DNA-related molecules are the main thing in the water, that preference helps. The researchers envision the approach one day helping cities treat their water supplies ^[13]. In that water, any other electron-rich molecule is also a target. The share of singlet oxygen that actually reaches DNA there is the figure a utility would need measured before sizing a reactor.

For operators, the authors' argument is about inputs. "Unlike conventional disinfection approaches that may require continuous addition of chemical oxidants, this system uses oxygen naturally available in the environment to disinfect water," said co-author Xinjian Shi of Henan University ^[8][14]. The team argues that because the crystals activate oxygen in a controlled way, the system may be safer than technologies that keep adding oxidants to water ^[11].