It has been shown that in addition to formation of pyrimidine dimers, UV irradiation of DNA in the absence of photosensitizer also induces formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine, but the mechanism of formation of that oxidized base has not been clearly established. In the present study, we provide an unambiguous demonstration that absorption of UVC and UVB radiation by the nucleobases induces DNA oxidation via a direct process (one-electron oxidation) and not singlet oxygen. Evidence arose from the fact that polyamine-guanine adducts that are specifically produced through the transient formation of guanine radical cation are generated following UV irradiation of DNA in the presence of a polyamine even in the absence of any photosensitizer.

Herein, the photocatalytic activity of four conjugated porous polymers (CPPs) based on BOPHY moiety (named IEP-x , x = 7, 8, 9, and 10) and TiO2 hybrids thereof to produce hydrogen from water under UV–vis irradiation is described. All the polymers show better performance than TiO2, and the hybrid materials (only 10 wt % of polymer loading) show a higher hydrogen evolution rate than the sum of their components. The best value is recorded for the IEP-7@T-10 sample which shows 12-fold higher HER than the sum of its individual bare materials. Also, this sample with 1 wt % photodeposited platinum as cocatalyst shows a photonic efficiency ( , %) of 14.54, 4.4-fold higher than the photonic efficiency of Pt/TiO2, in the same conditions. The combination of time-resolved fluorescence with transient absorption spectroscopy (TAS) measurements with the use of electron and hole scavengers allows us to determine an effective charge transfer mechanism Type II as mainly responsible for the improved photocatalytic activity.