Transient Species Research Articles

Direct measurement of the Criegee intermediate CH2OO in ozonolysis of ethene

Abstract The transient species produced from reactions of unsaturated hydrocarbons with ozone, carbonyl oxides, termed “Criegee intermediates”, play a key role in tropospheric oxidation mechanisms. Direct observation and characterization of Criegee intermediates in ozonolysis in situ were proven difficult in decades of efforts. Here, we report the direct measurement of the simplest Criegee intermediate, CH2OO, from ozonolysis of ethene by cavity ring-down spectroscopy in a flow cell reactor. The transient CH2OO is quantified rapidly by near-ultraviolet absorption spectra via its B̃(1A′) ← X̃(1A′) transition. Time profiles of CH2OO produced in ozonolysis under quasi-steady state conditions are observed. These CH2OO concentration profiles benchmark the modeling of the ethene ozonolysis reaction network and mechanism, allowing for determination of the yield and various kinetic data of CH2OO.

Phase Transformation Processes in Coprecipitated Cu/Zn/Zr Methanol Catalyst Precursors-Insights into Suspension Aging Form Ultrafast Nucleation.

Catalyst precursors for methanol synthesis prepared by coprecipitation, such as Cu/Zn-based hydroxycarbonates, are generally formed within two steps. The initial precipitation phase (nucleation) leads to a suspension from which, in a subsequent aging phase, the final solid precursor is formed, thus providing the structural and morphological features required for later use in catalysis. Combing ultrafast continuous nucleation with sampling from batch-wise aging opens up the possibility to follow the evolution and transitions of solid phases during suspension aging. The temporal progression of the existence of the different phases in a Cu/ZnO/ZrO2-based system is investigated by scanning electron microscopy, X-ray diffraction, and inductive coupled plasma optical emission spectroscopy . According to the findings of this study, the intermediate recrystallization reveals to be a yet unknown two-step process. The presence of an amorphous transient zinc depot of Na2Zn3(CO3)4 × 3 H2O greatly influences the formation of the relevant zincian malachite catalyst precursor [(Cu,Zn)2(OH)2CO3], which is partly in contrast to reports on Cu/ZnO/Al2O3 systems. Finally, a general mechanism including the relevant transformations during suspension aging in Cu/ZnO/ZrO2 systems is proposed, relying on a general thermodynamic approach, explaining the transient and final species.

Excited-state reaction dynamics of the radical anions revealed by time-resolved photofragment depletion spectroscopy

The excited-state reaction dynamics of radical anions are investigated using a newly developed technique: time-resolved photofragment depletion spectroscopy. This method leverages differences in photodetachment cross-sections among transient anionic species involved in the reaction pathway. It offers a distinct advantage for studying radical anions, which are typically challenging to probe using conventional spectroscopic techniques due to their low electron affinities. As a benchmark, the method is first applied to I₂⁻, whose excited-state behavior is well characterized. The technique is then extended to CH₃NO₂⁻ and (CH₃NO₂)₂⁻, enabling real-time probing of the excited-state dynamics of their nonvalence-bound states. Our findings reveal that ultrafast internal conversion from a nonvalence orbital to a valence orbital is followed either by prompt chemical bond dissociation or by comparatively slower cluster decomposition. These results highlight the dynamic role of the nonvalence orbital in driving chemical reactivity.

Enhanced Decontamination in Mn(II)/Periodate Systems with EDTA: Mechanistic Insights into Self-Accelerating Degradation of Pollutants.

Research promoting the use of aminocarboxylate ligands to enhance metal ion oxidation of pollutants in advanced oxidation processes (AOPs) has gained increasing interest in recent years. In this work, the most common ligand, ethylenediaminetetraacetic acid (EDTA), was used to enhance Mn(II) activation of periodate (PI, IO4-) for the degradation of the sulfisoxazole (SIZ). Chromatographic analysis of EDTA showed that EDTA, like SIZ, also exhibits self-accelerated degradation in this system. This suggests that the accelerated degradation of pollutants may be closely related to the structural changes of Mn(II)-EDTA. Oxidative pretreatment of Mn(II)-EDTA showed that the decay of Mn(II)-EDTA was accompanied by the disappearance of the self-accelerated degradation characteristic of the pollutants. Mass spectrometry analysis suggested that the decarboxymethylation of Mn(II)-EDTA to Mn(II)-ED3A is an important pathway for its structural transformation. The standard ED3A exhibited superior assistance to the Mn(II)/PI system compared to EDTA, without showing the self-accelerated degradation trend. Density functional theory (DFT) calculations indicated that Mn(II)-ED3A more readily reacts with PI, and the corresponding oxygen transfer product (O-Mn(IV)-ED3A)- possesses stronger oxidative properties. A series of mechanistic investigations confirmed the formation of transient Mn-oxo species, accompanied by the generation of hydroxyl radicals (•OH) as secondary radicals in the system. The degradation of SIZ primarily involves processes such as hydrolysis, hydroxylation, and nitration, accompanied by the attenuation of toxicity. This study provides mechanistic insights into the evolution of ligands in the Mn(II)/EDTA/PI system and highlights the need for greater attention to structural changes of organic ligands in catalytic oxidation systems.

Electrons and Their Multiple Kinetic Fates in an Ionic Liquid.

Ionic liquids (ILs) for electrochemical, nuclear, and solar energy applications operate under harsh conditions, where electrons and transient radical species can form. This communication discusses why anions such as bis(trifluoromethylsulfonyl)imide (Tf2N-) are reduced at the electron-rich electrode whereas in laser photoionization or pulse radiolysis studies, where electrons are ejected from species in the bulk, we often detect long-lived electrons in cavities that interact with IL cations instead. This work argues that bulk excess electrons generated photolytically or radiolytically follow kinetically favored pathways. As such, cavity electrons may not be the most energetically favorable states, but when they form, and they do form, they are kinetically stable. Reduction reactions of anions or electron localization in cavities and subsequent reactions are all expected outcomes. Here we focus on a pyrrolidinium-based IL of the dicyanamide (N(CN)2-) anion because of its large electrochemical window and very low viscosity, which are ideal for energy applications.

ATR-SEIRAS for Single-Atom Electrocatalysis.

ConspectusSingle-atom catalysts (SACs) represent a revolutionary paradigm in heterogeneous catalysis and display exceptional atom utilization efficiency with well-defined active sites. These distinctive characteristics position SACs as pivotal materials for advancing electrochemical energy conversion and storage technologies. The active center atoms are typically anchored by coordination with oxygen (O), nitrogen (N), and other functional groups on the surface of the supports. When precisely anchored onto tailored supports, these isolated active centers offer considerable promise for enhanced catalytic activity and selectivity. Nevertheless, the inherent complexity of the multistep proton-coupled electron transfer processes in electrochemical energy conversion and storage systems presents major challenges for the mechanistic elucidation and rational design of catalytic architectures to optimize reaction kinetics. Recent advancements in in situ/operando characterizations, most notably attenuated total reflection-surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), have greatly stimulated SACs research. ATR-SEIRAS amplifies the vibrational signal at the interface, enabling real-time tracking of transient interfacial species at submonolayer concentrations. Moreover, it simultaneously captures the dynamic structural evolution of single-atom motifs during the catalytic cycles.In this Account, we exemplify our recent endeavors in characterizing single-atom electrocatalysts using ATR-SEIRAS. Through the integration of the ATR-SEIRAS technique with precisely engineered SACs, we elucidate the critical structure-activity relationships of SACs in the CO/CO2 reduction reaction (CO/CO2RR), oxygen reduction reaction (ORR), and nitrate reduction reaction (NO3-RR). We begin with a fundamental analysis of the ATR-SEIRAS enhancement mechanisms, categorized into physical and chemical enhancement mechanisms. Building on this theoretical foundation, ATR-SEIRAS demonstrates the exceptional capability of tracing reaction pathways in single-atom electrocatalysis. This is achieved through vibrational fingerprint identification of oxygen-containing intermediates (O/O-H), carbonaceous moieties (C-H/C-O), and nitrogenous adsorbates (N-H/N-O). Furthermore, we discuss the role of ATR-SEIRAS in studying the stability of SACs in electrocatalytic CO/CO2RR, ORR, and NO3-RR. Additionally, ATR-SEIRAS can be utilized to determine the function of active sites in single-atom catalyst motifs, which is of paramount importance for gaining a deeper understanding of the reaction mechanisms and for the rational design of highly efficient catalysts. Crucially, ATR-SEIRAS plays a vital role in monitoring the dynamic structure evolution of SACs, thereby aiding in decoding the complex interactions between catalytic structure and performance. Last but not least, we demonstrate the use of ATR-SEIRAS for verifying density functional theory (DFT) calculation results in single-atom electrocatalysis. This Account provides a comprehensive perspective on the application of ATR-SEIRAS in studying single-atom electrocatalysis. The enhanced understanding of active site dynamics and reaction mechanisms obtained shall offer valuable insights for the rational design of high-performance, durable SACs for next-generation electrochemical energy conversion and storage applications.

Watching Vibrations Steer Electrons: Ultrafast Vibration-Induced Absorption Switching through Real-Time Orbital Modulation in a Confined Quantum System.

Excess electrons (EEs), transient anionic species pivotal in radiation chemistry, catalysis, and optoelectronics, have long been stabilized via solvent interactions such as hydrogen bonding in water or polar solvent traps. While these systems enable electron localization, their environmental sensitivity, limited spectral tunability, and static confinement mechanisms restrict applications requiring dynamic control. Here, we introduce a solvent-free paradigm using a supramolecular electropositive cage (C60F60) to confine and strongly couple an electron with a triatomic CO2 molecule, bypassing traditional solvation limitations. Through ab initio molecular dynamics, we uncover CO2's dual role as a nonlinear quantum actuator: Its bending vibration (∠OCO = 122-156°) steers sub-50 fs electron oscillation via synchronized s/p-orbital hybridization and polarity switching. Crucially, this vibration-EE coupling modulates the EE-orbital's symmetry, switching Laporte-forbidden (∠OCO < 133°/UV-dark) to allowed (∠OCO ≈ 133-140°/invisible-light and ∠OCO > 140°/visible-light) transitions, thereby enabling vibration-induced absorption switching spanning 380-760 nm. The C60F60 cage enhances CO2's electron affinity by 6.1 eV through noncovalent electrostatic stabilization, creating a vibrationally active yet chemically inert environment, a stark contrast to solvent-dependent systems. This platform reveals ultrafast coherence between molecular vibrations and electron redistribution, establishing a dynamic quantum confinement model in which mechanical motion directly dictates optical responses. By bridging triatomic molecular dynamics to macroscopic tunable luminescence, this work advances the design of stimuli-responsive optoelectronic materials, offering applications in wavelength-adaptive scintillators and ultrafast optical switches while redefining the role of vibrations in quantum state manipulation.

Photochemical Ligand-Based CO2 Reduction Mediated by Ruthenium Formyl Species.

A new, ligand-based strategy for CO2 reduction to formate has been demonstrated. This approach relies on the photochemical generation of a coordinatively saturated transient ruthenium metalloformyl species, Ru-CHO, capable of reducing CO2 to free formate directly. Under this paradigm, a highly reactive radical cation which is capable of facile formal hydrogen atom transfer (HAT) is generated via reductive quenching of an excited-state photosensitizer. Sequential electron transfer (ET) and HAT steps to a ruthenium carbonyl complex subsequently yield the Ru-CHO species, which upon further reduction undergoes fast hydride transfer to CO2, producing free formate. High formate selectivity (up to 98%) and impressive catalytic performance (TON ∼ 5300; TOF ∼ 0.1 s-1) were observed. Detailed mechanistic studies revealed that the overall process is highly sensitive to the identity of the radical cation, with divergent reactivity observed when HAT thermodynamics are altered. These findings provide new insights into ligand-based hydride transfer mechanisms and establish a foundation for the rational design of selective CO2 reduction catalysts.

Detection of Transient Decomposition Products of CF3SO2F and C4F7N via OES Under Spark and Glow Discharges

ABSTRACTThe optical emission spectra (OES) reflect the presence of excited states in the gaseous discharge, which are directly linked to the decomposition characteristics of insulating gases. In this study, a pin/rod–plate discharge reactor driven by either a high‐voltage direct current (DC) generator or a pulsed generator was developed to establish an effective platform for generating decomposition products of and . The experimental setup involved separate mixtures of F and N with different buffer gases (, ) under optimised operating conditions (maximum current) with varying mixture ratios. Through systematic investigation of emission spectrum characteristics under different gas mixing ratios, energy transitions of transient species induced by electrical excitation were captured using a high‐resolution optical emission spectrometer. Under spark discharge conditions, transient decomposition products such as F‐atoms, C‐atoms and CN radicals were detected from and mixed with or , indicating that discharges induced the cleavage of C–S, C–F and C–C bonds, and revealing the decomposition characteristics of the two eco‐friendly insulating gases in different buffer atmospheres. This work advances the understanding of decomposition mechanisms, providing valuable insights for fault diagnosis in gas‐insulated electrical equipment.

Radiolysis of Sub- and Supercritical Water Induced by 10B(n,α)7Li Recoil Nuclei at 300–500 °C and 25 MPa

(1) Background: Generation IV supercritical water-cooled reactors (SCWRs), including small modular reactor (SCW-SMR) variants, are pivotal in nuclear technology. Operating at 300–500 °C and 25 MPa, these reactors require detailed understanding of radiation chemistry and transient species to optimize water chemistry, reduce corrosion, and enhance safety. Boron, widely used as a neutron absorber, plays a significant role in reactor performance and safety. This study focuses on the yields of radiolytic species in subcritical and supercritical water exposed to 4He and 7Li recoil ions from the 10B(n,α)7Li fission reaction in SCWR/SCW-SMR environments. (2) Methods: We use Monte Carlo track chemistry simulations to calculate yields (G values) of primary radicals (e−aq, H•, and •OH) and molecular species (H2 and H2O2) from water radiolysis by α-particles and Li3⁺ recoils across 1 picosecond to 0.1 millisecond timescales. (3) Results: Simulations show substantially lower radical yields, notably e−aq and •OH, alongside higher molecular product yields compared to low linear energy transfer (LET) radiation, underscoring the high-LET nature of 10B(n,α)7Li recoil nuclei. Key changes include elevated G(•OH) and G(H2), and a decrease in G(H•), primarily driven during the homogeneous chemical stage of radiolysis by the reaction H• + H2O → •OH + H2. This reaction significantly contributes to H2 production, potentially reducing the need for added hydrogen in coolant water to mitigate oxidizing species. In supercritical conditions, low G(H₂O₂) suggests that H2O2 is unlikely to be a major contributor to material oxidation. (4) Conclusions: The 10B(n,α)7Li reaction’s yield estimates could significantly impact coolant chemistry strategies in SCWRs and SCW-SMRs. Understanding radiolytic behavior in these conditions aids in refining reactor models and coolant chemistry to minimize corrosion and radiolytic damage. Future experiments are needed to validate these predictions.

When can we expect negative effects of plant diversity on community biomass?

Abstract Although experiments overwhelmingly show biodiversity increases ecosystem functioning, relationships in natural communities are more variable. This raises the question of under which conditions negative diversity effects might occur. We argue that plant communities containing more core species that stably coexist should have higher biomass production. However, variation in numbers of transient species, whose abundances fluctuate strongly and which cannot stably coexist, may not consistently affect biomass. Distinguishing changes in core and transient species richness is critical. For instance, recent attempts to use novel causal modelling approaches have implied negative effects of biodiversity on community biomass. However, we find these approaches also result in negative relationships when applied to experiments, where we know there is a positive causal effect of biodiversity. We suggest that transient species contribute disproportionately to the variation in biodiversity isolated in these models. We highlight the need for improved approaches to analysing data from ‘real‐world’ communities and call for increased attempts to compare results with experimental systems. Synthesis. Understanding the functional consequences of biodiversity loss is critical but we need to be clear about what type of biodiversity change we are measuring and to focus on the loss of stably coexisting core species.

Rapid Scan Cyclic Voltammetry (RSCV) investigation of oxygen reduction reaction (ORR) on gold ultramicroelectrode (UME): a novel methodology to study kinetics of formation of transient intermediates

This study employs Rapid Scan Cyclic Voltammetry (RSCV) with a gold ultramicroelectrode (Au UME) to investigate transient species in the oxygen reduction reaction (ORR) under alkaline conditions. Gold was purposefully chosen as the electrode material due to its ability to generate peroxide radicals via a two-electron transfer mechanism. RSCV on Au UME shows cathodic peaks, C1 and C2, linked to the sequential reduction of oxygen to peroxide anion and then to hydroxyl anion, and along with an anodic peak, A1, corresponding to peroxide anion oxidation back to oxygen. Quantitative analysis of these peaks, performed by integrating the peak areas, enabled rate determination for the formation of transient species. Thermodynamic and kinetic analyses further show a preference for decomposition over reduction, attributed to lower activation energy requirements. These findings demonstrate RSCV-UME’s effectiveness for real-time ORR intermediate detection and highlight how scan rate adjustments can alter reaction pathways, offering a powerful approach for exploring electrochemical mechanisms relevant to electrocatalysis and energy conversion technologies.

Electrocatalytic 1,6-Difunctionalization of Bicyclopropanes.

Ring-opening remote difunctionalization of bicyclopropanes, which allows the incorporation of functional groups at the 1,6-positions, remains a significant challenge in synthetic organic chemistry. Herein, we report an electrochemically driven strategy that enables an unprecedented 1,6-ring-opening dioxygenation of bicyclopropanes. Central to this advancement is a π-conjugation-mediated electron transit process, which facilitates a concerted nucleophilic attack on transient aryl radical cation species at the remote site. This protocol operates under mild conditions and demonstrates broad substrate compatibility, exceptional stereoselectivity, and precise regiocontrol.

Predicting the Fate of Bisphenol A During Electrochemical Oxidation: A Simple Semiempirical Method Based on the Concentration Profile of Hydroxyl Radicals.

The efficiency of electrochemical advanced oxidation processes (EAOPs) is fundamentally governed by hydroxyl-radical (•OH) generation. While direct experimental measurements of these transient species remain complex and impractical, robust computational methods for predicting their temporal profiles are notably scarce. This work presents a semi-empirical methodology based on H2O2 measuring experiments that enables indirect •OH quantification. We employed a recently developed carbon-based electrode and the priority pollutant bisphenol A (BPA) as the model system. The system achieved 92.3% BPA degradation with 84% mineralization efficiency during 5-h electrooxidation at 15 mA/cm2. Gas chromatography/mass spectrometry (GC/MS) was used for tracking BPA and detection of intermediates. On this basis, we developed a computational model that successfully predicts temporal concentration profiles of all reactive species interacting with •OH, along with degradation kinetics across current densities (10-20 mA/cm2). By incorporating predictions from the Toxicity Estimation Software Tool (T.E.S.T.), the developed model accurately simulates time-dependent evolution of relative toxicity throughout the treatment process. The presented approach has a general character and requires rather simple experimental input to predict and optimize degradation outcome in terms of input concentration, degradation time, current density, and final toxicity. Further modifications of the model would enable widening to other EAOPs systems.

A Chiral CdS Magic-Size Cluster with Enantiomerically-Biased Crystallization.

Despite the symmetric, achiral atomic lattices typically found in binary semiconductor nanocrystals, we show that during their early formation stages, especially in the magic-size cluster (MSC) regime, chirality can be present in these metastable, transient species, which are capable of further self-assembling into high-level chiral superstructures. Through a cation exchange process operating at room temperature, a structurally symmetrical copper sulfide cluster has been successfully converted into a pair of enantiomeric cadmium sulfide MSCs, formulated as Cd28S17I22(PEt3)12 (abbreviated as (+)/(-)-[Cd28S17]). The atomic structures of these two MSCs were established by single-crystal X-ray crystallography. It is revealed that the [Cd28S17] MSCs feature an antisupertetrahedron configuration which has never been observed in reported CdS structures. Remarkably, rather than crystallizing into a racemic mixture, (+)/(-)-[Cd28S17] MSCs naturally crystallize out in an enantiomerically biased manner, sufficiently rendering distinctly opposite chiroptical responses. This behavior reflects genuine circular dichroism activity, which can be directly attributed to the chiral atomic structure of this well-known quantum photonic nanomaterial.

Debate of Nucleophilic versus Electrophilic Oxidative Aldehyde Deformylation by Mononuclear Nonheme Iron(III)-Peroxo and Iron(IV)-Oxo Complexes.

High-valent iron(IV)-oxo species are fleeting intermediates that perform vital reactions in enzymatic catalysis. In contrast, heme and nonheme iron(III)-peroxo intermediates usually act as nucleophiles and are converted to high-valent iron-oxo intermediates for electrophilic oxidation reactions. Herein, we report a study on aldehyde deformylation reactions of 2-phenylpropionaldehyde (2-PPA) and its derivatives by iron(III)-peroxo complexes bearing tetramethylated cyclam (TMC) analogues, including [FeIII(O2)(12-TMC)]+ (1), [FeIII(O2)(13-TMC)]+ (2), and [FeIII(O2)(14-TMC)]+ (3). Reactivity studies by employing deuterated substrates, such as α-[D1]-2-phenylpropionaldehyde and aldehyde-[D]-2-phenylpropionaldehyde, demonstrate that deformylation of 2-PPA by the nonheme iron(III)-peroxo complexes occurs via abstraction of the stronger aldehyde C-H atom, rather than the expected nucleophilic attack or weaker α-C-H atom abstraction reactions. Interestingly, the preference for aldehyde C-H atom abstraction is retained during the deformylation of 2-PPA by iron(IV)-oxo complexes, i.e., [FeIV(O)(13-TMC)]2+ (4) and [FeIV(O)(N4Py)]2+ (5). DFT calculations reproduce the experimental trends in reactivity and reveal that the peroxide O-O bond is cleaved to form an iron(III)-dioxyl species that conducts aldehyde C-H bond abstraction; this chemoselectivity is achieved through stabilizing noncovalent interactions between the oxidants and the aromatic ring of the substrate that positions the aldehyde in close proximity to the FeIII-O2/FeIV═O cores. These new experimental and theoretical findings together with the previous demonstrations of the ability of 1-3 in hydrogen atom transfer, oxygen atom transfer, and cis-dihydroxylation reactions highlight that iron(III)-peroxo cores are not inherently nucleophiles and can have more important functions in chemical and biological oxidation reactions, rather than acting as transient species en route to high-valent metal-oxo intermediates.

Southernmost record of Liparis montagui (Donovan, 1804) (Perciformes, Liparidae) in European waters (central Portugal), with&amp;nbsp;genetic validation

In January 2022, the presence of adult Liparis montagui (Donovan, 1804) was documented at its southernmost point along the west coast of Portugal. The species was identified through both morphological and genetic barcoding analyses. This observation, part of an ongoing long-term coastal survey, suggests that L. montagui may be a transient species, influenced by complex climate and oceanic interactions along the western Iberian coast. This finding stresses the importance of long-term ecological studies and regular field surveys in understanding species distribution and the effects of climate change on marine biodiversity.

Tracking the Chemical Evolution of Hydrocarbons Through Carbon Grain Supply in Protoplanetary Disks

Abstract The gas present in planet-forming disks typically exhibits strong emission features of abundant carbon and oxygen molecular carriers. In some instances, protoplanetary disks show an elevated C/O ratio above interstellar values, which leads to a rich hydrocarbon chemistry evidenced in the mid-infrared spectra. The origin of this strengthened C/O ratio may stem from the release of less complex hydrocarbons from the chemical processing of carbonaceous grains. We have explored a set of 42 single-cell models in which we match the physical conditions to the inner regions of planet-forming disks, while varying the C/O ratio by exploring different levels of CH4, C, H2O, and CO to the gas-phase chemistry, which we evaluate in both the cosmic/X-ray- and UV-driven limit. We find that the carbon-bearing species in our models exhibit high dependencies on the driver of the chemistry, where both CO and long chain hydrocarbons act as carbon sinks in the cosmic/X-ray-driven chemistry limit, while the vast majority ends up in atomic carbon and CO in the UV-driven limit. We also find moderate dependencies upon the C/O ratio, where this and the ionization rate/UV field determines the point of peak production of a species, as well as its equilibrium abundance. We also find that the production of several hydrocarbons, specifically C2H2, is strongly dependent up to an order of magnitude on the initial water abundance. We finally find that in the X-ray-driven limit, both CH4 and C serve as highly transient donor species to the carbon chemistry.

Isolated iridium oxide sites on modified carbon nitride for photoreforming of plastic derivatives

The rising concentration of plastics due to extensive disposal and inefficient recycling of plastic waste poses an imminent and critical threat to the environment and ecological systems. Photocatalytic reforming of plastic derivatives to value-added chemicals under ambient conditions proceeds at lower oxidation potential which galvanizes the hydrogen evolution. We report the synthesis of a narrow band gap NCN-functionalized O-bridged carbon nitride (MC) through condensation polymerization of hydrogen-bonded melem (M)-cyameluric acid (C) macromolecular aggregate. The MC scaffold hosts well-dispersed Ir single atom (MCIrSA) sites which catalyze oxidative photoreforming of alkali-treated polylactic acid (PLA) and polyethylene terephthalate (PET) derivatives to produce H2 at a rate of 147.5 and 29.58 μmol g−1cat h−1 under AM1.5G irradiation. Solid-state electron paramagnetic resonance (EPR) and time-resolved photoluminescence (TRPL) reveals efficient charge carrier generation and separation in MCIrSA. X-ray absorption spectroscopy (XAS) and Bader charge analysis reveal undercoordinated IrN2O2 SA sites pinned in C6N7 moieties leading to efficient hole quenching. The liquid phase EPR, in situ FTIR and density functional theory (DFT) studies validate the facile generation of •OH radicals due to the evolution of O-Ir-OH transient species with weak Ir--OH desorption energy barrier.

Intracellular assembly of supramolecular peptide nanostructures controlled by visible light

The complex dynamics of synthetic supramolecular systems in living cellular environments impede the correlation between the transient hierarchical species and their biological functions. Achieving this correlation demands a breakthrough that combines the precise control of supramolecular events at discrete time points via synthetic chemistry with their real-time visualization in native cells. In the present study, we reported two peptide sequences that undergo visible light-induced molecular and supramolecular transformations to form various assembly species in cells. In contrast to endogenous stimulus-responsive assembly, the proposed photochemistry enables full control over the photolysis reaction where the monomer generation and local concentration regulate the subsequent assembly kinetics. Phasor-fluorescence lifetime imaging traced the formation of various assembly states in cells associated with monomer activation and consumption, whereas correlative light-electron microscopy revealed the intracellular nanofibres formed. The temporally resolved assembly process shows that the emergence of cytotoxicity correlates with the accumulation of oligomers beyond the cellular efflux threshold.