Effects of UV illumination on organic dye decomposition activity and antibacterial and antiviral activities of rare earth iodates

Abstract For this study, we investigated the effects of UV illumination on dye decomposition and antibacterial and antiviral activities of three rare earth iodates (Ce(IO 3 ) 4 , Ce(IO 3 ) 3 , and δ -La(IO 3 ) 3 ) that reportedly have antibacterial and antiviral activities in the dark. The objective of this study was to clarify whether bulk materials and eluted ions are involved in these activities under UV illumination. Findings indicate that Ce(IO 3 ) 3 and δ -La(IO 3 ) 3 exhibit dye degradation activity under UV illumination by a Hg-Xe lamp (7 mW/cm 2 ), suggesting that the dye decomposition activity was caused mainly by photochemical reactions under UV with wavelengths less than 300 nm by Ce 3+ and by IO 3 − ions eluted from the samples. The dye decomposition activity under UV illumination is expressed not only from the eluted ions but also from the bulk materials. UV illumination using a weak (0.1 mW/cm 2 ) UV light from a black light bulb with wavelengths longer than 320 nm increased the antibacterial and antiviral activities of these materials. These results suggest that the increase in antibacterial and antiviral activities is attributable to the photocatalytic reaction of bulk materials. This study revealed that both the bulk and eluted ions are involved in these activities under UV illumination. The extent to which photochemical reactions caused by eluted ions and bulk material contribute to the decomposition activity of organic dyes and antibacterial and antiviral activities depends on the UV illumination wavelength and intensity. This study provides new insights into the use of rare earth iodates as inorganic antibacterial and antiviral materials. Graphical abstract