[en] We report the results of fabricating micrometer and submicrometer-scale patterns of cytochrome c on gold surfaces. We used direct micro-contact printing (μCP) and indirect dip-pen nanolithography (DPN) for fabricating cytochrome c arrays. The protein dots were formed in diameters of 2 μm by μCP and of ∼200 nm by DPN, respectively. We analyzed the pattern size and height of protein arrays with atomic force microscopy (AFM). We expect that these methods will be potentially useful for developing small-scale biosensors and protein chip microarrays

[en] Graphical abstract: Sb nanoparticles wrapped with a-few-layer graphene coat (Sb@Gn) were prepared from Sb₂O₃ by a two-step ball-milling process. The e⁻ and O²⁻ were counter-transferred through graphene layer (@Gn) during zinco-mechanical reduction of Sb₂O₃ to Sb. The Sb/Zn alloying was completely avoided by the @Gn. Sb@Gn showed excellent performances as anodes for sodium ion batteries. Display Omitted -- Highlights: •Antimony nanoparticles wrapped with a-few-layer graphene coat (Sb@Gn) were prepared. •The Sb@Gn was synthesized by mechanochemical and metallomechnical ball milling process form Sb₂O₃ •The Sb@Gn anode showed outstanding capacity retention and improved rate capability. •The graphene layer not only provide conductive pathway but also limit volume expansion. -- Abstract: Antimony metal nanoparticles wrapped with a-few-layer graphene coat (Sb@Gn) were fabricated from their oxide form (Sb₂O₃) in a micrometer dimension using a novel two-step ball-milling process. The first mechanochemical process was designed to decrease the particle size of Sb₂O₃ microparticles for ensuring advantages of nano size and to subsequently coat the Sb₂O₃ nanoparticles with a-few-layer graphene (Sb₂O₃@Gn). The second metallomechanical ball-milling process reduced the oxide to its metal form (Sb@Gn) by the help of Zn as a metallic reductant. The graphene layer (@Gn) blocked the alloying reaction between Sb and Zn, limiting the size of Sb particles during the metallomechanical reduction step. During reduction, oxygen species were transferred from of Sb₂O₃ through @Gn to Zn along redox transfer pathways rather than direct mass transfer via unsaturated vacancies in the @Gn. the redox transfer involving oxidation of @Gn by O²⁻ is plausible routes for O²⁻ transfer in the metallomechanical reduction. The Sb@Gn anode exhibited outstanding capacity retention along charge/discharge cycles and improved rate capability in sodium-ion batteries. The @Gn provided conductive pathways to the Sb core and limited size expansion during sodium-lithium alloying.

[en] Highlights: • Precisely-controlled Fe₂TiO₅ layers of IOS is fabricated via a layer-by-layer self-assembly. • Hybrid microwave annealing yields highly transparent and crystalline Fe₂TiO₅ IOS photoelectrode. • IOS provides enhanced light harvesting and higher density of catalytically active crystal planes. • The modified IOS photoanode shows a high PEC water splitting activity. -- Abstract: Iron titanate (Fe₂TiO₅) is a promising photoanode material due to a narrow band gap, appropriate band edges, robustness and abundance. However, its performance is limited because of its low conductivity and short hole diffusion length. Precisely controlled, a few Fe₂TiO₅ layers of inverse opal structure (IOS) is fabricated via a layer-by-layer self-assembly and then treated by hybrid microwave annealing to produce a highly crystalline, yet IOS morphology-preserved Fe₂TiO₅ photoanode film for solar water splitting. The highly transparent Fe₂TiO₅ IOS film shows a greatly enhanced visible light harvesting, higher density of catalytically more active crystal planes, and many single crystalline nanoplates grown on the IOS architecture, relative to a reference planar film prepared under similar conditions. As a result, the optimized ‘exactly’ three Fe₂TiO₅ layers IOS electrode with a sacrificial gallium oxide underlayer and a ternary (Ni₂CoFe)OOH co-catalyst records 2.08 mA cm⁻² at 1.23 V_RHE under 1 sun (100 mW cm⁻²) irradiation, which is the highest photocurrent density produced by Fe₂TiO₅ photoanode up to date.

[en] Highlights: • The first example of heterogeneous electrocatalysis based on double activation is presented. • Introduction of a secondary organic catalyst to a primary inorganic catalyst improved ORR activity. • The secondary organic catalyst donated its electron to oxygen molecule to form O₂^δ-. • Also, the secondary organic catalyst donated its proton to the single oxygen intermediate (*O). Synergistic effects of dual homogeneous catalysts for chemical reactions have been reported. Double activation (chemical transformation process where both catalysts work in concert to activate reactants or intermediates) was often responsible for the synergistic effects of dual catalyst systems. Herein, we demonstrate the extension of the double activation from chemo-catalysis to electrocatalysis. The activity of low-cost cobalt oxide electrocatalysts for oxygen reduction reaction (ORR) was significantly improved by introducing secondary-amine-conjugated polymers (HN-CPs) as the secondary promoting electrocatalyst (shortly, promoter). It was proposed that HN-CPs activated neutral diatomic oxygen to partially charged species (O₂^δ-) in the initial oxygen adsorption step of ORR. Electron donation number of HN-CP to diatomic oxygen (δ in O₂^δ-) well described the order of activity improvement, i.e., polypyrrole (pPy) > polyaniline (pAni) > polyindole (pInd). The maximum overpotential gain at ~150 mV was achieved by using pPy with the highest δ. Also, it was confirmed that proton of HN-CP was transferred to single oxygen intermediate (*O) of ORR.

[en] Oxygen vacancies (OV) are native defects in transition metal (TM) oxides and their presence has a critical effect on the physicochemical properties of the oxide. Metal oxides are commonly used in lithium-ion battery (LIB) cathodes and there is still a lack of understanding of the role of OVs in LIB research field. Here, we report on the behavior of OVs in a single-crystal LIB cathode during the non-equilibrium states of charge and discharge. We found that microcrack evolution in a single crystal occurs due to OV condensation in specific crystallographic orientations generated by the continuous migration of OVs and TM ions. Moreover, understanding the effects of the presence and diffusion of OVs in metal oxides enables the elucidation of most of the conventional mechanisms of capacity fading in LIBs and provides new insights for new electrochemical applications. (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)

[en] Current state-of-the-art Li batteries use single-phase electrolytes; however, these electrolytes often encounter difficulty in simultaneously fulfilling the nonidentical electrochemical requirements of cathodes and anodes. Here, a class of immiscible binary liquid electrolyte (BLE) is designed by starving free solvent molecules. Based on their electrochemical stability window, 1,2-dimethoxyethane (DME) and succinonitrile (SN) are selected as model solvents for Li-metal anodes and LiNi${}_{0.8}$Co${}_{0.1}$Mn${}_{0.1}$ (NCM811) cathodes, respectively. Li bis(fluorosulfonyl)imide (LiFSI), which promotes Li${}^{+}$ solvation (i.e., reduces free solvents), enables the phase separation of the miscible solvent mixture (SN - DME), and an increase in its concentration strengthens the coordination of Li${}^{+}$-FSI${}^{-<!--\; ???\; -->}$ in the solvation sheath, thus yielding (anion-derived) fluorine-rich electrode-electrolyte interphases. The resulting BLE allows 4.4 V Li-metal full cells to exhibit a stable capacity retention under a constrained cell condition (Li (20 µm, 4.1 mAh cm${}^{-<!--\; ???\; -->2}$)||NCM811 (3.8 mAh cm${}^{-<!--\; ???\; -->2}$), N (negative)/P (positive) capacity ratio = 1.08), which exceed those of previously reported binary liquid electrolytes. (© 2023 Wiley‐VCH GmbH)

[en] Despite their advantageous attributes, such as a narrow bandgap and reduced toxicity, tin-lead halide perovskites (TLHPs) have received limited attention due to their lower power conversion efficiency (PCE) relative to lead-only variants. In this study, a transformative approach is introduced that leverages perovskite quantum dots (PQDs) to optimize TLHP solar cells. While conventional oleyl-capped PQDs enhance the open circuit voltage (V${}_{OC}$), the long-chain ligands hinder charge transport. To overcome this limitation, a post-treatment with isopropyl alcohol effectively dissociates these ligands and PQD crystals, resulting in reduced defect density, improved charge transfer, and elevated quasi-Fermi level splitting in the TLHP device. Consequently, the PCE of the device is notably increased from 19.0% to 23.74% and elevated the V${}_{OC}$ from 0.78 to 0.87 V, without compromising the photocurrent or fill factor. The findings highlight PQD modification as a compelling avenue for TLHP solar cell enhancement, particularly in boosting V${}_{OC}$. (© 2024 Wiley‐VCH GmbH)

[en] Controlling defects is one of the basic strategies for tailoring electronic structure of materials, which has not been explored that much yet for organic-inorganic hybrid systems. In this study, we investigated the control of work function of oxide electrode by defect-associated adsorption of molecules at the single-molecule level by means of scanning tunneling microscopy and first principle calculations. The equilibrium adsorption configuration of monoethanolamine (MEA, HO(CH₂)₂NH₂), an effective coating for lowering the work function of an oxide electrode, varies as a function of surface coverage at TiO₂(1 1 0) surfaces. Our results showed that defects at the oxide surface and intermolecular interactions dominate the stable configuration of adsorbates as well as work function of the system. The dissociative adsorption at ${\text{O}}_{\text{v}}$ was found to be more efficient at lowering the work function of TiO₂(1 1 0) surface, suggesting that defect control can be used to improve the performance of organic-inorganic hybrid systems.

[en] Highlights: • A facile aqueous synthesis of Cu₇S₄ nanofibers and spherical nanoparticles. • Experiments and calculations reveal the importance of Cl⁻ and Br⁻ in the formation of nanofibers. • Slow reaction rate also leads to the formation of nanofibers. Copper sulfide (Cu₇S₄) nanoparticles were synthesized by adding ethanolic elemental sulfur solution to an aqueous solution containing Cu(II) precursor, branched polyethyleneimine (BPEI), and ascorbic acid. By varying the Cu(II) precursor used, we could control the morphology of the nanoparticles produced to be either quasi spherical (CuF₂, Cu(NO₃)₂, and CuSO₄) or vine like nanofibers (CuCl₂ and CuBr₂). By comparing experimental results and conducting calculations we found that selective adsorption of Br⁻ and Cl⁻ onto specific crystal facets and slowing of the reaction rate owing to formation of Cu(I)–anion–BPEI complexes explain the observed change in morphology from spherical particles to vine like nanofibers. We also found that the differences in morphology of Cu₇S₄ nanoparticles affects the electrochemical performance of Li batteries including the nanoparticles as electrode materials.

[en] Highlights: • Porous carbons were prepared from cellulose via hydrothermal carbonization and ZnCl₂ activation. • A facile and effective CuCl loading method resulted in high CO adsorption performance. • Copper-loaded porous carbon exhibited good cyclic stability using vacuum regeneration. • Density functional theory calculations correlated the experimental results. CO is used as a raw material to produce valuable chemicals. Adsorption using solid materials can be employed to separate and recover CO from gas mixtures. In this study, cellulose-based, porous carbons were prepared via hydrothermal carbonization and ZnCl₂ activation. The prepared porous carbons were used for CO separation after CuCl loading by a facile solid-state dispersion method to induce π-complexation and eventually enhance the affinity toward CO. The sample with the highest CO uptake of 3.62 mmol g⁻¹ at 298 K and 101 kPa had a carbon:CuCl loading ratio of 1:1. This is the highest reported CO adsorption on porous carbons using CuCl as a π-complexation-inducing material. In addition, several factors, including the selectivity of CO against CO₂ and the cyclic stability using vacuum regeneration, demonstrated the potential for industrial applications. Density functional theory (DFT) calculations theoretically elucidated that the presence of small and well-dispersed CuCl clusters induce excellent CO-selective adsorption performance, which is in accordance with the experimental results.