Greigite (Fe3S4) is thermodynamically stable: Implications for its terrestrial and planetary occurrence

Unveiling the role of inorganic nanoparticles in Earth's biochemical evolution through electron transfer dynamics

This article explores the intricate interplay between inorganic nanoparticles and Earth's biochemical history, with a focus on their electron transfer properties. It reveals how iron oxide and sulfide nanoparticles, as examples of inorganic nanoparticles, exhibit oxidoreductase activity similar to proteins. Termed "life fossil oxidoreductases," these inorganic enzymes influence redox reactions, detoxification processes, and nutrient cycling in early Earth environments. By emphasizing the structural configuration of nanoparticles and their electron conformation, including oxygen defects and metal vacancies, especially electron hopping, the article provides a foundation for understanding inorganic enzyme mechanisms. This approach, rooted in physics, underscores that life's origin and evolution are governed by electron transfer principles within the framework of chemical equilibrium. Today, these nanoparticles serve as vital biocatalysts in natural ecosystems, participating in critical reactions for ecosystem health. The research highlights their enduring impact on Earth's history, shaping ecosystems and interacting with protein metal centers through shared electron transfer dynamics, offering insights into early life processes and adaptations.

Inorganic Fe-O and Fe-S oxidoreductases: paradigms for prebiotic chemistry and the evolution of enzymatic activity in biology

Oxidoreductases play crucial roles in electron transfer during biological redox reactions. These reactions are not exclusive to protein-based biocatalysts; nano-size (<100 nm), fine-grained inorganic colloids, such as iron oxides and sulfides, also participate. These nanocolloids exhibit intrinsic redox activity and possess direct electron transfer capacities comparable to their biological counterparts. The unique metal ion architecture of these nanocolloids, including electron configurations, coordination environment, electron conductivity, and the ability to promote spontaneous electron hopping, contributes to their transfer capabilities. Nano-size inorganic colloids are believed to be among the earliest 'oxidoreductases' to have 'evolved' on early Earth, playing critical roles in biological systems. Representing a distinct type of biocatalysts alongside metalloproteins, these nanoparticles offer an early alternative to protein-based oxidoreductase activity. While the roles of inorganic nano-sized catalysts in current Earth ecosystems are intuitively significant, they remain poorly understood and underestimated. Their contribution to chemical reactions and biogeochemical cycles likely helped shape and maintain the balance of our planet's ecosystems. However, their potential applications in biomedical, agricultural, and environmental protection sectors have not been fully explored or exploited. This review examines the structure, properties, and mechanisms of such catalysts from a material's evolutionary standpoint, aiming to raise awareness of their potential to provide innovative solutions to some of Earth's sustainability challenges.

Structural, electronic and magnetic properties of greigite Fe3S4by GGA and GGA+Uversus SCAN meta-GGA density functionals

The performance of exchange-correlation functional of density functional theory represented in generalized gradient approximation (GGA) and in the strongly constrained and appropriately normed (SCAN) meta-GGA scheme to study structural, electronic, and magnetic properties of greigite (Fe3S4) was investigated. The effects of inclusion of strong electron correlations represented by on-site Hubbard correctionU, and nonlocality of the long-range van der Waals (vdW) interactions were also considered. Geometry optimization yielded the inverse spinel structure and lattice parameter of greigite in good agreement with experimental data. Calculated electronic structure revealed a half-metallic nature of the greigite bands for the applied functionals except for GGA, which predicts metallic behavior. Antiferromagnetic coupling of iron ions in tetrahedral and octahedral coordinations makes the overall crystal structure ferrimagnetic. In general the GGA+Uand SCAN show comparable performance in prediction physical properties of greigite. Inclusion of the vdW correction does not change the character of the bands.

Phase Control in the Synthesis of Iron Sulfides

The identity and repeating arrangement of atoms determine the properties of all solids. Even combinations of two atoms can have multiple crystal structures of varying stoichiometries and symmetries with vastly different electronic and chemical behaviors. The conditions of existing bottom-up routes for achieving one phase over another are serendipitous, and the links among precursor reactivity, decomposition mechanism, temperature, and time are elusive. Our studies take a systematic approach to understanding the role that the precursor kinetic decomposition has in the synthesis of iron sulfides, isolating it from other mechanistic factors. The data suggest that phase determination in binary solids can be logically predicted through the consideration of the anion stacking and thermodynamic relationships between phases. Mapping these relationships allows for the rational synthetic targeting of metastable crystalline phases.