Two-dimensional altermagnetic semiconductors are promising for low-stray-field spintronic and valleytronic applications, yet Mn-based systems with strain-tunable local valley splitting and piezomagnetism are rarely studied. Using first-principles calculations, we predict a dynamically stable Mn2Se2S monolayer with an altermagnetic ground state and out-of-plane spin orientation, which remains semiconducting over the Hubbard U = 3.0–4.0 eV range. Uniaxial in-plane strain breaks the diagonal mirror symmetry, yielding a sign-reversible local piezovalley response with a local valence-band splitting varying over a range of 246.13 meV. Carrier doping induces a strain-dependent imbalance between spin-channel occupations, enabling a net magnetization and a doping-tunable piezomagnetic effect. Strain defines −1, 0, and +1 local valley-ordering states, for which the valley-contrasting Berry curvature suggests a possible electrical readout through a transverse response. This work expands Mn-based altermagnetic semiconductors and identifies Mn2Se2S as a candidate for strain-driven valleytronic and piezomagnetic devices.
Regulating the electronic states of catalysts for enhancing the oxygen evolution reaction (OER) catalytic activity is crucial yet challenging in lithium–oxygen (Li–O2) batteries. In this study, we synthesized Co3O4 as a model system to explore the correlation between the density of states (DOSs) of Co3O4 and OER catalytic activities in Li–O2 batteries. Compared to the original Co3O4, as well as the single-element doped P–Co3O4 and Pt–Co3O4, the Pt and P codoped Co3O4 (Pt/P–Co3O4) demonstrate enhanced DOSs across the entire range near the Fermi level due to the misaligned distribution of electronic states between Pt and P. The significant increase in the DOSs of Pt/P–Co3O4 results in a high donor energy level, which enhances the adsorption strength with intermediate states, thereby significantly reducing the charge activation energy and overpotentials. Establishing the relationship between the DOSs of the catalyst and the charging overpotential provides important guidance for designing high-performance cathode catalysts for Li–O2 batteries.
Direct formic acid fuel cells represent a cornerstone of the clean energy transition, yet their efficiency remains tethered to the rigid scaling relations of the formic acid oxidation reaction. Here, we demonstrate that a heteronuclear Rh–Cr dual-atom catalyst can bypass these traditional limits by operating as a potential-gated molecular circuit. Using grand-canonical ab initio molecular dynamics at the explicit aqueous interface, we observe the reaction in real time under constant-potential conditions. Our simulations reveal a remarkable division of responsibility between the two metal centers. The Cr site acts as a static anchor, spontaneously deprotonating formic acid and pinning the formate anion in a geometry that prevents the formation of carbon monoxide (CO). Meanwhile, the Rh center acts as a potential-controlled relay. It remains a spectator during initial absorption but switches on at a critical potential threshold, facilitating a near-frictionless hydride transfer with a negligible barrier of just 0.04 eV. This synergistic handshake effectively decouples intermediate stability from reaction kinetics─a feat impossible for single-site catalysts. We observe a synergetic migratory oxidation pathway, in which the Rh center, once activated, facilitates near-frictionless C–H activation and a hydride transfer. Crucially, we show that traditional constant-charge models fail to capture this circuit-like behavior, leading to artificially high barriers and a misidentification of the rate-determining step. By framing the Rh–Cr pair as a stereoselective electronic filter, this work provides a new blueprint for designing catalysts that do not just speed up reactions but also electronically steer them toward high-flux and poison-resistant pathways.
Cu–Sn–S (copper–tin–sulfide; CTS) ternary semiconducting chalcogenides are composed of nontoxic and earth-abundant elements, so there has been a great deal of interest in future photovoltaic devices. In this article, we investigate optical and magneto-optical (MO) properties of CTS nanodots with different phases, Cu3SnS4 and Cu2SnS3, to better understand the influence of elemental deficiencies on their composition-dependent performance. Both Cu3SnS4 and Cu2SnS3 nanodots are successfully obtained via direct synthesis using multiple cation precursors in the presence of thiourea and found to possess isostructural orthorhombic phases. The nanodots of Cu3SnS4 exhibit optical absorption attributed to localized surface plasmon resonance (LSPR) with a broad peak at 1500–2000 nm, while those of Cu2SnS3 at > ∼3000 nm, depending on their substoichiometry. The p-type LSPR mode of the Cu3SnS4 nanodots is rationalized by magnetic circular dichroism (MCD), and the surface Cu-deficiency rather than the donor defects (S-deficiency and/or Sn-excess) significantly contributes to the free carrier (hole) generation. The value of effective hole mass is estimated by the MCD spectral simulation. As for the Cu2SnS3 nanodots, in addition to the LSPR band in the IR region, two distinct optical transitions near the bandgap region (∼500–800 nm) are unveiled by strong MCD responses with the same signs, stemming from two noninteracting Faraday B-terms, and then the origin of these transitions is discussed.
Metal alkanoates represent the most challenging impurities in quantum dot (QD) purification. These species readily form clusters through extended metal–carboxylate coordination in common QD solvents. When present in QD dispersions, such clusters coassemble with QDs to generate insoluble and gel-like aggregates. Herein, we demonstrate that these clusters and related assemblies can be effectively disassembled via the introduction of tetramethylammonium alkanoate (NMe4Al). This strategy enables facile purification of diverse QDs through selective precipitation of the QDs within a single toluene–acetonitrile dissolution–precipitation cycle. The generalized complex-based purification protocol fully preserves the native surface ligands of QDs, thereby retaining their photoluminescence quantum yields and colloidal stability. This generalized purification protocol is expected to play a key role in fundamental research and technical applications of colloidal QDs.
