The development of advanced energy systems is essential for replacing fossil fuel-based societies, and progress in the fundamental understanding of solid-state energy materials has revolutionized this field. In particular, investigating the inhomogeneity of reactions in energy systems requires analysis at the level of individual particles, which are the smallest units in the system. Synchrotron-based scanning transmission X-ray microscopy (STXM) is a valuable tool for exploring reaction and degradation mechanisms, and providing nanoscale site-specific information on chemical and structural changes within single particles. In-situ/operando STXM is particularly useful for observing reactions under well-controlled conditions in real time, thus providing insights into local phenomena obscured by the ensemble effect. This review highlights the research achievements of in-situ/operando STXM in the field of energy materials and provides perspectives for advanced X-ray imaging techniques that can further enhance STXM capabilities.

Ribosomally synthesized and post-translationally modified peptides (RiPPs) are a structurally diverse class of natural products with a distinct biosynthetic logic, the enzymatic modification of genetically encoded precursor peptides. Although their structural and biosynthetic diversity remains largely underexplored, the identification of novel subclasses with unique structural motifs and biosynthetic pathways is challenging. Here, it is reported that peptide/protein L-aspartyl O-methyltransferases (PAMTs) present in several RiPP subclasses are highly homologous. Importantly, it is discovered that the apparent evolutionary transmission of the PAMT gene to unrelated RiPP subclasses can serve as a basis to identify a novel RiPP subclass. Biochemical and structural analyses suggest that homologous PAMTs convert aspartate to isoaspartate via aspartyl-O-methyl ester and aspartimide intermediates, and often require cyclic or hairpin-like structures for modification. By conducting homology-based bioinformatic analysis of PAMTs, over 2,800 biosynthetic gene clusters (BGCs) are identified for known RiPP subclasses in which PAMTs install a secondary modification, and over 1,500 BGCs where PAMTs function as a primary modification enzyme, thereby defining a new RiPP subclass, named pamtides. The results suggest that the genome mining of proteins with secondary biosynthetic roles can be an effective strategy for discovering novel biosynthetic pathways of RiPPs through the principle of “guilt by association”.

Emitters having a negative energy difference between their lowest singlet and triplet excited states are promising candidates for developing next-generation organic light-emitting diodes (OLEDs) because their inverted singlet and triplet (IST) excited states enable exothermic reverse intersystem crossing, which results in a fast rate constant for reverse intersystem crossing and facilitates the efficient harvesting of triplet excitons. This study reports the development of organic emitters comprising 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene as an electron acceptor and 10H-spiro[acridine-9,9′-fluorene] as an electron donor that exhibit IST-excited states. We confirmed the presence of IST excited states in our emitters using photoluminescence spectroscopy, time-correlated single-photon counting, and excited-state density functional theory calculations. In addition, by varying the number of electron donors and the dihedral angles between the electron donor and acceptor, we identified the underlying reasons for the inversion of the singlet and triplet states. Furthermore, we achieved high external quantum efficiencies of up to 30 % by utilizing the IST emitters as emitting layers in OLEDs.

Herein, the self-reinforced inductive effect derived from coexistence of both p- and n-type redox-active motifs in a single organic molecule is presented. Molecular orbital energy levels of each motif are dramatically tuned, which leads to the higher oxidation and the lower reduction potentials. The self-reinforced inductive effect of the symmetric bipolar organic molecule, N,N’-dimethylquinacridone (DMQA), is corroborated, by both experimental and theoretical methods. Furthermore, its redox mechanism and reaction pathway in the Li+-battery system are scrutinized. DMQA shows excellent capacity retention at the operating voltage of 3.85 and 2.09 V (vs Li+/Li) when used as the cathode and anode, respectively. Successful operation of DMQA electrodes in a symmetric all-organic battery is also demonstrated. The comprehensive insight into the energy storage capability of the symmetric bipolar organic molecule and its self-reinforced inductive effect is provided. Thus, a new class of organic electrode materials for symmetric all-organic batteries as well as conventional rechargeable batteries can be conceived.

Drawing inspiration from allosteric proteins, a zigzag-shaped π-conjugation was structurally engineered into a tweezer-like ionophore having multiple disparate binding sites. When a soft metal ion binds to the central tridentate ligand motif, the rigid backbone folds, bringing two macrocyclic arms into close proximity. Stabilized by a coordinating anion, the tweezer-like conformation of the resulting metalloligand recruits a hard cation to form a sandwich-like complex with a remarkably enhanced binding affinity and selectivity.

Targeting proximity-labeling enzymes to specific cellular locations is a viable strategy for profiling subcellular proteomes. Here, we generated transgenic mice (MAX-Tg) expressing a mitochondrial matrix-targeted ascorbate peroxidase. Comparative analysis of matrix proteomes from the muscle tissues showed differential enrichment of mitochondrial proteins. We found that reticulon 4-interacting protein 1 (RTN4IP1), also known as optic atrophy-10, is enriched in the mitochondrial matrix of muscle tissues and is an NADPH oxidoreductase. Interactome analysis and in vitro enzymatic assays revealed an essential role for RTN4IP1 in coenzyme Q (CoQ) biosynthesis by regulating the O-methylation activity of COQ3. Rtn4ip1-knockout myoblasts had markedly decreased CoQ9 levels and impaired cellular respiration. Furthermore, muscle-specific knockdown of dRtn4ip1 in flies resulted in impaired muscle function, which was reversed by dietary supplementation with soluble CoQ. Collectively, these results demonstrate that RTN4IP1 is a mitochondrial NAD(P)H oxidoreductase essential for supporting mitochondrial respiration activity in the muscle tissue.

Hybridizing single-walled carbon nanotubes (SWCNTs) with π-conjugated organic small molecules (π-OSMs) offers a promising approach for producing high-performance thermoelectric (TE) materials through the facile optimization of the molecular geometry and energy levels of π-OSMs. Designing a twisted molecular structure for the π-OSM with the highest occupied molecular orbital energy level comparable to the valence band of SWCNTs enables effective energy filtering between the two materials. The SWCNTs/twisted π-OSM hybrid exhibits a high Seebeck coefficient of 110.4 ± 2.6 µV K−1, leading to a significantly improved power factor of 2,136 µW m−1 K−2, which is 2.6 times higher than that of SWCNTs. Moreover, a maximum figure of merit over 0.13 at room temperature is achieved via the efficient TE transport of the SWCNTs/twisted π-OSM hybrid. The study highlights the promising potential of optimizing molecular engineering of π-OSMs for hybridization with SWCNTs to create next-generation, efficient TE materials.

The alkaline hydrogen evolution reaction (HER) plays a pivotal role in realizing a H2-based circular economy. However, it is a topic of ongoing debate because of its complexity. Here, we unveil a unique volcano-type size-dependent activity trend of archetypical Ru-based alkaline HER catalysts and demonstrate that this trend is dictated by the interplay of geometric and electronic effects. Size-controlled Ru nanoparticles (NPs) from 0.78 to 3.31 nm were synthesized, and they exhibited volcanic size-dependence of specific activity and reaction kinetics, with 1.38 nm Ru NPs showing the highest activity and lowest Tafel slope. The large variation in the Tafel slope of Ru NP catalysts from 29 to 109 mV dec–1 suggests that tuning of Ru NP size can vary the rate-determining step in the order of the Heyrovský (0.79 nm), Tafel (1.38 nm), and Volmer (3.31 nm) steps. The specific activity of 1.38 nm Ru NPs is 5.0, 2.6, and 1.2 times higher than those of 3.31 nm Ru NPs and commercial Pt/C and Ru/C catalysts, respectively. Atomic-level geometric structure analysis and density functional theory calculations revealed that excellent activity of 1.38 nm Ru NPs correlates with their abundance in edge sites, which show optimum H* binding energy and elementary step energetics. A significant decline in the intrinsic activity of the alkaline HER was observed in the subnanometer Ru NPs, which could be associated with suppressed H* chemisorption due to enhanced surface oxidation and amorphous surface nature in this size regime. Overall, the intrinsic activity trend of Ru NPs is governed by both the geometric fraction of active edge sites and suppression of H* intermediate chemisorption in the subnanometer regime.

The formation of supracolloidal chains from the patchy micelles of diblock copolymers bears a close resemblance to traditional step-growth polymerization of difunctional monomers in many aspects, including chain-length evolution, size distribution, and initial-concentration dependence. Thus, understanding the colloidal polymerization based on the step-growth mechanism can offer potential control over the formation of supracolloidal chains in terms of chain structure and reaction rate. We analyzed the size evolution of supracolloidal chains of patchy micelles of PS-b-P4VP by investigating a large number of colloidal chains visualized in SEM images. We varied the initial concentration of patchy micelles to achieve a high degree of polymerization and a cyclic chain. To manipulate the polymerization rate, we also changed the ratio of water to DMF and adjusted the patch size by employing PS(25)-b-P4VP(7) and PS(145)-b-P4VP(40). We confirmed the step-growth mechanism for the formation supracolloidal chains from patchy micelles of PS-b-P4VP. Based on this mechanism, we were able to achieve a high degree of polymerization early in the reaction by increasing the initial concentration and form cyclic chains by diluting the solution. We also accelerated colloidal polymerization by increasing the ratio of water to DMF in the solution and patch size by using PS-b-P4VP with a larger molecular weight.

The stability of n-type organic and hybrid thermoelectric materials is limited in terms of their practical application to p–n parallel thermoelectric devices. We demonstrate the ambient stability of an n-type single-walled carbon nanotube/organic small-molecule (SWNT/OSM) hybrid by deepening the lowest occupied molecular orbital energy level. This hybrid exhibited the best figure of merit (0.032) among n-type SWNT/OSM hybrid thermoelectrics and an enhanced power factor of 291.0 μW m–1 K–2. Furthermore, we observed that the n-type thermoelectric stability of a hybrid of SWNT and pip containing two N-ethylpiperidinyl groups on both sides of a naphthalenediimide core was retained at 87% over 7 months (220 days) under ambient conditions without encapsulation.