Reflections on the pigments of life
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Balancing aesthetics and efficiency of coloured opaque photovoltaics
The integration of solar photovoltaics (PV) into buildings and infrastructure necessitates PV elements that are suitable as construction materials and aesthetically pleasing. In this Perspective, we explore how coloured opaque PV technologies blend power generation with visual appeal, providing foundational methods for better balancing aesthetics and efficiency. Our analysis covers the key features and theoretical efficiency limits of coloured opaque PV modules, noting that efficiencies of around 22% are practically achievable across most colours. We provide an overview of various optical materials for PV colourization, focusing on easily mass-producible inorganic pigments, multilayer dielectric thin films and interference pigments that facilitate higher efficiency, and other emerging materials. To boost future development and benchmarking, we propose a design framework that incorporates optical and electrical simulation, along with an inverse optimization algorithm for achieving an optimal coloured PV with targeted colour and maximum efficiency. We also suggest that future studies should include detailed reporting of metrics that involve power conversion performance, colour lightness and chromaticity, and the influence of colouring materials, to facilitate fair performance assessment. Finally, we identify the challenges that remain in enhancing the performance and practical application of coloured opaque PV and offer potential solutions.
Discovery of giant unit-cell super-structure in the infinite-layer nickelate PrNiO2+x
The discovery of unconventional superconductivity often triggers significant interest in associated electronic and structural symmetry breaking phenomena. For the infinite-layer nickelates, structural allotropes are investigated intensively. Here, using high-energy grazing-incidence x-ray diffraction, we demonstrate how in-situ temperature annealing of the infinite-layer nickelate PrNiO2+x (x ≈ 0) induces a giant superlattice structure. The annealing effect has a maximum well above room temperature. By covering a large scattering volume, we show a rare period-six in-plane (bi-axial) symmetry and a period-four symmetry in the out-of-plane direction. This giant unit-cell superstructure—likely stemming from ordering of diffusive oxygen—persists over a large temperature range and can be quenched. As such, the stability and controlled annealing process leading to the formation of this superlattice structure provides a pathway for novel nickelate chemistry.
Mixed-layer lipidomes suggest offshore transport of energy-rich and essential lipids by cyclonic eddies
Mesoscale eddies are ubiquitous features in the ocean affecting the cycles of nutrients and carbon. Cyclonic eddies formed in Eastern Boundary Upwelling Systems can substantially modulate primary production by phytoplankton and the vertical and lateral export of organic carbon. However, the impact of eddy activity on the biochemical composition of eukaryotic phytoplankton, bacteria and archaea and associated consequences for carbon and energy flows are largely unknown. Here, we investigated the microbial lipidome in the surface ocean in and around a cyclonic eddy formed in the coastal upwelling system off Mauritania. We show that the eddy contained almost three times the amount of lipids compared to the surrounding open-ocean and coastal waters. The eddy lipid signature with energy-rich triacylglycerols and essential fatty acid-containing membrane lipids of eukaryotic phytoplankton origin was further significantly different from the ambient waters. Strong variability in lipid distributions within the eddy was related to differences in microbial community composition. Estimates indicate that in the Mauritanian upwelling area, as much as 9.7 ± 2.0 gigagrams of lipid carbon per year is delivered to the open ocean by coastal cyclonic eddies potentially fueling higher trophic levels and contributing to the maintenance of secondary productivity and carbon export offshore.
Archaean green-light environments drove the evolution of cyanobacteria’s light-harvesting system
Cyanobacteria induced the great oxidation event around 2.4 billion years ago, probably triggering the rise in aerobic biodiversity. While chlorophylls are universal pigments used by all phototrophic organisms, cyanobacteria use additional pigments called phycobilins for their light-harvesting antennas—phycobilisomes—to absorb light energy at complementary wavelengths to chlorophylls. Nonetheless, an enigma persists: why did cyanobacteria need phycobilisomes? Here, we demonstrate through numerical simulations that the underwater light spectrum during the Archaean era was probably predominantly green owing to oxidized Fe(III) precipitation. The green-light environments, probably shaped by photosynthetic organisms, may have directed their own photosynthetic evolution. Genetic engineering of extant cyanobacteria, simulating past natural selection, suggests that cyanobacteria that acquired a green-specialized phycobilin called phycoerythrobilin could have flourished under green-light environments. Phylogenetic analyses indicate that the common ancestor of modern cyanobacteria embraced all key components of phycobilisomes to establish an intricate energy transfer mechanism towards chlorophylls using green light and thus gained strong selective advantage under green-light conditions. Our findings highlight the co-evolutionary relationship between oxygenic phototrophs and light environments that defined the aquatic landscape of the Archaean Earth and envision the green colour as a sign of the distinct evolutionary stage of inhabited planets.
High-pressure synthesis and crystal structure of iron sp3-carbonate (Fe2[C4O10]) featuring pyramidal [C4O10]4- anions
The behavior of iron carbonates at high pressures is relevant for geological processes occurring in Earth interiors. Here, cubic iron sp3-carbonate Fe2[C4O10] was synthesized in diamond anvil cell by reacting Fe2O3 and CO2 at 65(4) GPa and 3000(±500) K, simulating the environment of localized thermal anomalies in the mantle. The crystal structure, determined by in situ single-crystal X-ray diffraction, features pyramidal [C4O10]4- anions. The experimental crystal structure corresponds to a structural model from density functional theory calculations. Experimentally determined values for zero-pressure volume V0 and bulk modulus K0 are: V0 = 1059(17) Å3, K0 = 160(18) GPa, The DFT-calculated Raman spectrum, modeled with zinc substituting iron, matches the experimental one, supporting the structural model’s accuracy. Fe2[C4O10] remained stable upon decompression down to 25 GPa, below which it amorphized. DFT calculations also reveal a spin crossover of Fe2+ cations at 95 GPa, which is significantly higher than in other Fe2+-containing carbonates.
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