The predominant synergic effect of GQDs and SrRuO3CEs drives faster ion diffusions and electron transfer, thereby contributing to excellent catalytic activity of the SRO–GQD CE towards I3−reduction.

Anoxygenic phototrophic Fe(II)-oxidizing bacteria (photoferrotrophs) are suggested to have contributed to the deposition of banded iron formations (BIFs) from oxygen-poor seawater. However, most studies evaluating the contribution of photoferrotrophs to Precambrian Fe(II) oxidation have used freshwater and not marine strains. Therefore, we investigated the physiology and mineral products of Fe(II) oxidation by the marine photoferrotroph Rhodovulum iodosum. Poorly crystalline Fe(III) minerals formed initially and transformed to more crystalline goethite over time. During Fe(II) oxidation, cell surfaces were largely free of minerals. Instead, the minerals were co-localized with EPS suggesting that EPS plays a critical role in preventing cell encrustation, likely by binding Fe(III) and directing precipitation away from cell surfaces. Fe(II) oxidation rates increased with increasing initial Fe(II) concentration (0.43-4.07 mM) under a light intensity of 12 μmol quanta m(-2) s(-1). Rates also increased as light intensity increased (from 3 to 20 μmol quanta m(-2) s(-1)), while the addition of Si did not significantly change Fe(II) oxidation rates. These results elaborate on how the physical and chemical conditions present in the Precambrian ocean controlled the activity of marine photoferrotrophs and confirm the possibility that such microorganisms could have oxidized Fe(II), generating the primary Fe(III) minerals that were then deposited to some Precambrian BIFs.

In this study, carbon nanodots (C-dots)/WO photocatalysts were prepared via a two-step hydrothermal method. The morphologies and optical properties of the as-prepared materials were investigated. Compared with the prepared WO and C-dots, the C-dots/WO possessed stronger photocatalytic capability and excellent recyclability for photocatalytic elimination of Rhodamine B. For example, the achieved first order reaction rate constant of 0.01942 min for C-dots/WO was ∼7.7 times higher than that of the prepared WO. The enhanced photocatalytic activity of C-dots/WO was attributed to the enhanced light harvesting ability and efficient spatial separation of photo-excited electron-hole pairs resulting from the synergistic effect of WO and C-dots. The high photocatalytic activity of C-dots/WO remained unchanged even after 3 cycles of use. Meanwhile, a possible mechanism of C-dots/WO for the enhanced photocatalytic activity was proposed.