A Chinese research team has describe a simple new method of disinfection based on nanoscopic structures made of silver sulfide (Ag2S), according to a press release from Wiley by Jing Zhao.
The treatment is based on tiny biocompatible assemblies of atoms, known as quantum dots, made of silver sulfide and with caps made of a silver-binding peptide. When irradiated with near-infrared light, they kill bacteria in water with high efficiency through synergistic effects.
The research team, led by Xushen Qiu, Wei Wei, and Jing Zhao of Nanjing University, has introduced the new method in the journal Angewandte Chemie.
Quantum dots are nanoscopic structures made of about one-to-ten thousand atoms that are “confined” in space. Their quantum-mechanical properties correspond more to those of molecules than macroscopic solids, which can lead to interesting opto-electronic effects.
Silver sulfide quantum dots are already used in photodynamic and photothermic therapy, including for the treatment of certain tumors and skin diseases. They can be used as contrast agents and as fluorescence thermometers.
So far, these structures have not been used much for disinfecting water, partly because previous methods for preparing them have been complicated and expensive. The team from Nanjing University and the Nanchuang (Jiangsu) Institute of Chemistry and Health has now developed a simple, inexpensive production method, in which the quantum dots are enclosed by caps made from a specially-developed biomimetic silver-binding peptide (AgBP2).
When irradiated with near-infrared light, the new AgBP2-Ag2S quantum dots effectively kill bacteria in water. The researchers say these dots are chemically stable, photostable, and biocompatible.
Their strong activity is due to a synergistic combination of two effects. First, irradiation causes them to produce highly reactive oxygen species, and second, they cause strong local heating. Neither of the two effects alone leads to success, but their synergistic combination effectively destroys bacterial cell membranes.
The team says that these dots are able to kill over 99 % of E. coli bacteria within 25 minutes of NIR irradiation—a highly promising strategy for antibacterial disinfection of water.
