Photocatalytic activities of coke carbon/g-C3N4 and Bi metal/Bi mixed oxides/g-C3N4 nanohybrids for the degradation of pollutants in wastewater.

Different g-C3N4 composite systems (coke carbon/g-C3N4, Bi/Bi2WO6/g-C3N4 and Bi/Bi2MoO6/g-C3N4) have been assessed as photocatalysts for wastewater pollutants removal. The coke carbon/g-C3N4 hybrid, produced by thermal treatment at 550 °C of a composite made from melamine cyanurate and coke, only showed activity under UV-light irradiation. On the other hand, inorganic Bi spheres/Bi mixed oxides/g-C3N4 nanohybrids (Bi/Bi2WO6/g-C3N4 and Bi/Bi2MoO6/g-C3N4 composites), produced by thermal reduction of Bi2WO6 or Bi2MoO6 by g-C3N4, exhibited a remarkable red-shift, up to 620 nm, and allowed the visible-light driven degradation of the contaminant, albeit in combination with some adsorption.

The ephemeral fumarolic mineralization of the 2021 Tajogaite volcanic eruption (La Palma, Canary Islands, Spain).

The present work aims to characterize the ephemeral mineral assemblage related to the fumarolic fields of the Tajogaite volcano, formed in 2021 in La Palma Island (Canary Islands, Spain). A set of 73 samples was obtained after two sampling campaigns in different fumarole sectors of the studied area. Mineralization related to these fumaroles formed efflorescent patches located at variable distance from the main volcanic craters. Distal patches are predominantly whitish, while in the vicinities they typically show yellowish to orange colours. Field observations also revealed that fumaroles usually occur in elevated topographic areas as well as over fractured and porous volcanic pyroclastic materials. The mineralogical and textural characterisation of the Tajogaite fumaroles unfolds a complex mineral assemblage, comprising cryptocrystalline phases related to low (< 200 °C) and medium temperature (200-400 °C) conditions. In Tajogaite, we propose a classification of three different fumarolic mineralization types: (1) fluorides and chlorides located in proximal fumarolic areas (~ 300-180 °C); (2) native sulphur associated with gypsum, mascagnite and salammoniac (~ 120-100 °C) and (3) sulphates and alkaline carbonates typically occurred in distal fumarolic areas (< 100 °C). Finally, we present a schematic model of the formation of Tajogaite fumarolic mineralization and their compositional evolution developed during the cooling of the volcanic system.

Shifting the Sun: Solar Spectral Conversion and Extrinsic Sensitization in Natural and Artificial Photosynthesis.

Solar energy harvesting is largely limited by the spectral sensitivity of the employed energy conversion system, where usually large parts of the solar spectrum do not contribute to the harvesting scheme, and where, of the contributing fraction, the full potential of each photon is not efficiently used in the generation of electrical or chemical energy. Extrinsic sensitization through photoluminescent spectral conversion has been proposed as a route to at least partially overcome this problem. Here, we discuss this approach in the emerging context of photochemical energy harvesting and storage through natural or artificial photosynthesis. Clearly contrary to application in photovoltaic energy conversion, implementation of solar spectral conversion for extrinsic sensitization of a photosynthetic machinery is very straightforward, and-when compared to intrinsic sensitization-less-strict limitations with regard to quantum coherence are seen. We now argue the ways in which extrinsic sensitization through photoluminescent spectral converters will-and will not-play its role in the area of ultra-efficient photosynthesis, and also illustrate how such extrinsic sensitization requires dedicated selection of specific conversion schemes and design strategies on system scale.