Photocatalytic Hydrogen Evolution Driven by a Heteroleptic Ruthenium(II) Bis(terpyridine) Complex.

Since the initial report by Lehn et al. in 1979, ruthenium tris(bipyridine) ([Ru(bpy)3]2+) and its numerous derivatives were applied as photosensitizers (PSs) in a large panel of photocatalytic conditions while the bis(terpyridine) analogues were disregarded because of their low quantum yields and short excited-state lifetimes. In this study, we prepared a new terpyridine ligand, 4'-(4-bromophenyl)-4,4‴:4″,4‴'-dipyridinyl- 2,2':6',2″-terpyridine (Bipytpy) and used it to prepare the heteroleptic complex [Ru(Tolyltpy)(Bipytpy)](PF6)2 (1; Tolyltpy = 4'-tolyl-2,2':6',2'-terpyridine). Complex 1 exhibits enhanced photophysical properties with a higher quantum yield (7.4 × 10-4) and a longer excited-state lifetime (3.8 ns) compared to those of [Ru(Tolyltpy)2](PF6)2 (3 × 10-5 and 0.74 ns, respectively). These enhanced photophysical characteristics and the potential for PS-catalyst interaction through the peripheral pyridines led us to apply the complex for visible-light-driven hydrogen evolution. The photocatalytic system based on 1 as the PS, triethanolamine as a sacrificial donor, and cobaloxime as a catalyst exhibits sustained activity over more than 10 days under blue-light irradiation (light-emitting diode centered at 450 nm). A maximum turnover number of 764 was obtained after 12 days.

Release of silver and titanium from face masks traded for the general population.

Previous assessments of a selection of face masks intended for the general population in Belgium found that silver (Ag)-based biocides were present in masks advertised for antimicrobial properties; whereas titanium dioxide (TiO2) particles were detected in all the face masks in at least one layer corroborating its widespread use in the textile industry. The presence of Ag-based biocides and TiO2 particles in face masks raised questions on the possibility of release under normal wearing conditions, which could potentially cause a health risk to the consumers. Direct measurement of release of Ag and TiO2 particles during normal wearing is problematic by the lack of methodology to test release and to quantify inhaled particles. Therefore in this study, we investigated leaching experiments using artificial acid sweat as a method to evaluate the release of Ag-based biocides and TiO2 particles present in face masks. Leaching experiments were proposed as an alternative method to evaluate the quality of face masks, and as a higher tier method to assess face masks that are not safe-by-design. Results from leaching experiments showed that Ag was released in amounts varying from 0.03 up to 36 % of total Ag content, in four out of the eight face masks that claimed antimicrobial properties and that contained Ag. The leaching data of titanium (Ti) showed that despite TiO2 being detected in all face masks, only in one mask Ti was measured in detectable concentrations in artificial sweat (0.35 % of total Ti content). Comparison of leachable Ag and Ti with respective acceptable exposure limit values derived from inhalation exposure limits indicate that three face masks would need further risk assessment and could not be considered as intrinsically safe.