Abstract Bond rotation is an important phenomenon governing the fate of reactions. In particular, heterogeneously substituted ethane derivatives provide distinct structural conformations around the bond, empowering them as ideal systems for studying the rotation along carbon-containing single bonds. However, structural dynamics of ultrafast single-bond rotation, especially along C–C• bonds, have remained elusive as tracking the detailed changes in structural parameters during the rotational isomerization is challenging with conventional spectroscopic tools. Here, we employ femtosecond time-resolved X-ray liquidography to visualize the rotational isomerization between anti and gauche conformers of tetrafluoroiodoethyl radical (C2F4I•) and 1,2-tetrafluorodiiodoethane (C2F4I2), simultaneously. The TRXL data captures perturbations in conformer ratios and structures of each reacting species, revealing that the rotational isomerization of C2F4I• and C2F4I2 follows anti-to-gauche and gauche-to-anti paths with time constants of 1.2 ps and 26 ps, respectively. These findings also align with the computational predictions. This work offers an atomic-level insight into the kinetics and structural dynamics of single-bond rotation.

Abstract Cubane‐type metal clusters respond uniquely to stimuli like light and electric potential, resulting in behaviors such as crystal‐to‐crystal phase transitions. While structural adaptability is known to be linked to these responses, direct experimental evidence for the associated structural changes has been missing. This study addresses this gap by examining the structural dynamics of the copper(I) iodide cubane (Cu4I4(py)4, py = pyridine) upon photoexcitation using time‐resolved X‐ray liquidography. The results reveal: 1) 100 picoseconds (ps) after excitation, two distinct excited states—the cluster‐centered triplet (3CC) state and the (metal+halide)‐to‐ligand charge transfer triplet (3(M/X)LCT) state—are present; 2) the 3(M/X)LCT state decays with an apparent time constant of 1.21 ns, primarily transitioning to the 3CC state, with a small fraction undergoing decay to the ground state (GS); and 3) the 3CC state eventually returns to the GS. The molecular structures, provided for these states serve as benchmarks for theoretical studies. Importantly, the 3CC structure exhibits significant distortion in the Cu4I4 core and reduced symmetry, findings that are unanticipated by previous models. This comprehensive investigation deepens the understanding of the structural transformations occurring upon photoexcitation, with a potential impact on future applications of these compounds as versatile components in photosensitive metal–organic frameworks.

High-performance lithium -ion batteries require high energy density, long cycle life, and fast (dis)chargeability. Despite several accomplishments in increasing capacity under normal operation, maintaining high capacity under fast charging and discharging remains a challenge. To achieve such performance, we have applied nitrogen -ion (N+ ) irradiation to an anode material comprising tin oxyhydroxide nanoparticles (Sn6O4 (OH)( 4) NPs) active material, carbon black conducting agent, and polyvinylidene fluoride (PVDF) binder. Sn6O4 (OH) (4) NPs have high capacity and fair rate capability due to their layered structure with a large interlayer spacing of 0.455 nm and a small particle size of < 5 nm. N+ irradiation induces multiple defects including implanted N+ and oxygen vacancies in the anode material. The defects provide more Li -ion active sites in the Sn6O4 (OH) (4 )NPs and lead to amorphization of carbon black as well as increasing the conductivities of Sn6O4 (OH) (4) NPs. Additionally,N+ irradiation brings about cross -linking of PVDF, enhancing the binding property. As a consequence, the N+ - irradiated anode shows significantly improved performance: a capacity maintains 2306 mA h g( -1) after 500 cycles at 0.5C and 1053 mA h g (-1) after 300 cycles at 5C. Moreover, the anode exhibits outstanding rate capability even under ultrahigh -rate operation: 65.1 % capacity retention at 50C.

Crystalline systems consisting of small-molecule building blocks have emerged as promising materials with diverse applications. It is of great importance to characterize not only their static structures but also the conversion of their structures in response to external stimuli. Femtosecond time-resolved crystallography has the potential to probe the real-time dynamics of structural transitions, but, thus far, this has not been realized for chemical reactions in non-biological crystals. In this study, we applied time-resolved serial femtosecond crystallography (TR-SFX), a powerful technique for visualizing protein structural dynamics, to a metal–organic framework, consisting of Fe porphyrins and hexazirconium nodes, and elucidated its structural dynamics. The time-resolved electron density maps derived from the TR-SFX data unveil trifurcating structural pathways: coherent oscillatory movements of Zr and Fe atoms, a transient structure with the Fe porphyrins and Zr 6 nodes undergoing doming and disordering movements, respectively, and a vibrationally hot structure with isotropic structural disorder. These findings demonstrate the feasibility of using TR-SFX to study chemical systems.

This study investigates anti-corrosion properties of anodized and hydrophobically modified anodized SUS 304 stainless steel (SS 304). Utilizing electrochemical anodization and subsequent annealing, a well-ordered hexagonally closed-packed nanoporous oxide layer on the SS 304 surface, designated as AAS, was successfully developed. Then, a self-assembled monolayer of silane molecules, namely, octadecyltrimethoxysilane (ODTS) and 1 H,1 H,2 H,2 H-perfluorooctyltriethoxysilane (PFTS), was formed on the nanoporous oxide layer of annealed-anodized SS 304. The FTIR study confirmed the formation of the self-assembly of silane molecules on nanoporous oxide surface. The self-assembled monolayers exhibited hydrophobic surface where hydrophobicity increases with increase of silane molecule concentration and gives a water contact angles measure of 127.60 degrees and similar to 128.83 degrees for 0.50 wt% ODTS and 0.50 wt% PFTS, respectively. The potentiodynamic polarization study revealed a corrosion rate of 1.485 x 10(-3) mm year(-1) for AAS, 0.614 x 10(-3) mm year(-1) for 0.50 wt% ODTS-AAS, and 0.348 x 10(-3) mm year(-1) for 0.50 wt% PFTS-AAS. This represents a significant reduction in corrosion rate compared to bare stainless steel (4.385 x 10(-3) mm year(-1)) when exposed to a simulated sea water environment. The AAS, 0.50 wt% ODTS-AAS and 0.50 wt% PFTS-AAS exhibited corrosion inhibition efficiency of 66.13 %, 85.97 % and 92.06 %, respectively. Electrochemical impedance analysis revealed that PFTS exhibits roughly double the effective charge transfer resistance of ODTS and 7.4 times higher than that of annealed anodized stainless steel, confirming superior corrosion inhibition capability. Overall, this research illuminates the mechanism behind self-assembled monolayer formation, resulting in the development of hydrophobic surfaces and the inhibition of corrosion on nanoporous oxide layers on stainless steel surfaces.

The performance of hybrid Li-ion capacitors (LICs), which aim for high energy density while maintaining high power density, declines owing to the slow kinetics of battery-type anodes. In this study, the performance of LICs was improved by directly forming a nanoporous Nb2O5 anode on a niobium (Nb) current collector through the etching of Nb via electrochemical anodization. This binder-free structure provides a large active surface and fast electron transport. In addition, the formed Nb2O5 anode had an amorphous structure with many defects, which increased the number of active sites and the conductivities of Li ions and electrons. Consequently, the amorphous nanoporous Nb2O5 (a-n-Nb2O5) anode exhibited a high specific capacity of 233 mA h g(-1) at 1 A g(-1) and an excellent capacity retention rate of 92% after 1000 cycles. The charge storage of the a-n-Nb2O5 anode exhibited pseudocapacitive intercalation behavior, demonstrating the rapid kinetics of the electrode. Moreover, the a-n-Nb2O5 anode exhibited an excellent energy density, maintaining a high energy density of 123.8 W kg(-1) at 831 W h kg(-1).

Metal-semiconductor interfaces are crucial components of optoelectronic and electrical devices, the performance of which hinges on intricate dynamics involving charge transport and mechanical interaction at the interface. Nevertheless, structural changes upon photoexcitation and subsequent carrier transportation at the interface, which crucially impact hot carrier stability and lifetime, remain elusive. To address this long-standing problem, they investigated the electron dynamics and resulting structural changes at the Au/TiO2 interface using ultrafast electron diffraction (UED). The analysis of the UED data reveals that interlayer electron transfer from metal to semiconductor generates a strong coupling between the two layers, offering a new way for ultrafast heat transfer through the interface and leading to a coherent structural vibration that plays a critical role in propagating mechanical stress. These findings provide insights into the relationship between electron transfer and interfacial mechanical and thermal properties.

Molecular ions are ubiquitous and play pivotal roles 1–3 in many reactions, particularly in the context of atmospheric and interstellar chemistry 4–6 . However, their structures and conformational transitions 7,8 , particularly in the gas phase, are less explored than those of neutral molecules owing to experimental difficulties. A case in point is the halonium ions 9–11 , whose highly reactive nature and ring strain make them short-lived intermediates that are readily attacked even by weak nucleophiles and thus challenging to isolate or capture before they undergo further reaction. Here we show that mega-electronvolt ultrafast electron diffraction (MeV-UED) 12–14 , used in conjunction with resonance-enhanced multiphoton ionization, can monitor the formation of 1,3-dibromopropane (DBP) cations and their subsequent structural dynamics forming a halonium ion. We find that the DBP + cation remains for a substantial duration of 3.6 ps in aptly named ‘dark states’ that are structurally indistinguishable from the DBP electronic ground state. The structural data, supported by surface-hopping simulations 15 and ab initio calculations 16 , reveal that the cation subsequently decays to iso -DBP + , an unusual intermediate with a four-membered ring containing a loosely bound 17,18 bromine atom, and eventually loses the bromine atom and forms a bromonium ion with a three-membered-ring structure 19 . We anticipate that the approach used here can also be applied to examine the structural dynamics of other molecular ions and thereby deepen our understanding of ion chemistry.

Substantial improvement of corrosion resistance of austenitic stainless steel (SS) has been demonstrated with a protective oxide layer formed by the cathodic plasma electrolytic oxidation (CPEO) process. Two distinct layers, a porous-structured outer layer comprising Fe oxides and a compact inner layer comprising Cr oxides, were created on the SS surface after the CPEO process. The thicknesses of the outer and inner layers were approximately 7 mu m and 12 mu m, respectively, and the oxide layers were fabricated in an exceptionally short time of <30 s. A potentiodynamic polarization analysis exhibited a 65 % decrease in the corrosion current after the formation of the protective oxide layer, verifying the effectiveness of the CPEO treatment on the corrosion resistance of SS. An electrochemical impedance spectroscopy study revealed that the outer layer captured corrosive species due to its porous structure, while the inner layer had high resistance to reactions with corrosive species due to the compact structure of Cr oxides. Additionally, a Rockwell C indentation test demonstrated the robust mechanical property of the protective oxide layer with a strong bonding strength to the substrate.

X-ray free-electron lasers (XFELs) provide femtosecond X-ray pulses suitable for pump-probe time-resolved studies with a femtosecond time resolution. Since the advent of the first XFEL in 2009, recent years have witnessed a great number of applications with various pump-probe techniques at XFELs. Among these, time-resolved X-ray liquidography (TRXL) is a powerful method for visualizing structural dynamics in the liquid solution phase. Here, we classify various chemical and biological molecular systems studied via femtosecond TRXL (fs-TRXL) at XFELs, depending on the focus of the studied process, into (i) bond cleavage and formation, (ii) charge distribution and electron transfer, (iii) orientational dynamics, (iv) solvation dynamics, (v) coherent nuclear wavepacket dynamics, and (vi) protein structural dynamics, and provide a brief review on each category. We also lay out a plausible roadmap for future fs-TRXL studies for areas that have not been explored yet.

In this study, Plasma Electrolytic Oxidation (PEO) technology was adapted to stainless steel for improving its corrosion resistance. Stainless steel is widely used in various fields due to its remarkable properties including high corrosion resistance, excellent weldability, good performance at all temperatures, etc. Although, in the case of nuclear power plants secondary cooling water components, which mainly utilize stainless steel, aggressive environments are situated created. Plenty of corrosive and abrasive species from the coolants attack the component materials to initiate a wide range of corrosion problems such as general corrosion, pitting corrosion, crevice corrosion, and Stress Corrosion Cracking (SCC), etc. In order to protect the substrate from those corrosive environments, a pre-oxidized layer was deposited through an electrochemical process. The technology used in this study, namely PEO, is an advanced surface engineering method that can produce a protective film having an excellent hardness, heat resistance, and adhesiveness with a compact layer. PEO, which is a developed version of the anodization method, utilizes relatively high voltage with a pulse to enhance the properties of the ceramic layer on the surface by heating and quenching repetitive processes. PEO on stainless steel was conducted by cathodic process and plasma discharges were generated through vapor gas envelope insulating film. After the experiment, a variety of characterizations were conducted. Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) were firstly utilized to check the surface morphologies and compositions. Then using hot mounting and polishing, the cross-section of the sample was examined to check the oxide layer thickness and chemical composition by depth. By using an X-ray Diffractometer (XRD), the exact crystalline structure of the fabricated film was characterized. The following characterizations were mainly focused on electrochemical corrosion resistance tests. A typical three-electrode cell system was used to conduct the Potentiodynamic Polarization (PDP) technique for evaluating the improvement of general corrosion resistance. With corrosion potential and corrosion current density parameters from the PDP technique, pitting potential was also evaluated to check the pitting corrosion resistance. Lastly, Electrochemical Impedance Spectroscopy (EIS) method was conducted to figure out the corrosion resistance mechanism of the fabricated protective film and support the numerical data from the perspective of corrosion resistance improvement. PEO is a simple, fast, and relatively safe surface engineering method that can be applicated to various metal substrates. It is expected to improve diverse properties of the metal materials including corrosion resistance. It can be said that this technology can open a new era in material engineering in a wide range of industrial fields.

In this work, we explore the nonenzymatic detection of H2O2 using anodic SnO2 nanoporous channels (NPC) decorated with CuO quantum dots (QDs). The open-top and crack-free morphology of SnO2 NPC was obtained by modified anodization. The samples were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray analysis (EDAX), high-resolution transmission electron microscopy (HRTEM), Raman and X-ray photoelectron (XPS) spectroscopy. FESEM and HRTEM results show that SnO2 has a uniform channel width and pore size with an average diameter of around 40 nm. XRD, EDAX, XPS, Raman, and HRTEM measurements confirm the high purity of anodic SnO2 NPC with successful deposition of CuO QDs. Pristine (SnO2) and hybrid (SnO2-CuO) electrodes were used directly as the nonenzymatic H(2)O(2 )biosensor. The hybrid electrode demonstrated an ultrahigh sensitivity of similar to 85,250 mu A mM-1 cm-2 with an extremely low limit of detection (0.001 mu M), broad linear detection ranges of 5-95 and 25-450 mu M, and a quick response time (less than 1.9 s) toward H(2)O(2 )detection. This can be attributed to the advanced SnO2 nanoporous structure, the reduced band gap, and the formation of additional surface sites as a result of CuO QD decoration. H(2)O(2 )measurement in human blood serum demonstrates high sensitivity, good accuracy, and excellent selectivity of the fabricated hybrid electrode compared to the commercially available biosensor. Density functional theory results indicate that the formation of SnO2-CuO is energetically favorable. H(2)O(2)is strongly and selectively adsorbed over the SnO2-CuO nanostructure possessing a large negative adsorption energy (-1.89 eV) and evinces a significant decrease in the band gap (up to 1.59 eV) of the hybrid structure. The fabricated biosensor showed the highest sensitivity, excellent selectivity, good reproducibility, repeatability, and stability, thus confirming it as a favorable candidate for nonenzymatic H(2)O(2 )sensing and quantification.

X-ray free-electron lasers (XFELs) provide femtosecond X-ray pulses suitable for pump–probe time-resolved studies with a femtosecond time resolution. Since the advent of the first XFEL in 2009, recent years have witnessed a great number of applications with various pump–probe techniques at XFELs. Among these, time-resolved X-ray liquidography (TRXL) is a powerful method for visualizing structural dynamics in the liquid solution phase. Here, we classify various chemical and biological molecular systems studied via femtosecond TRXL (fs-TRXL) at XFELs, depending on the focus of the studied process, into (i) bond cleavage and formation, (ii) charge distribution and electron transfer, (iii) orientational dynamics, (iv) solvation dynamics, (v) coherent nuclear wavepacket dynamics, and (vi) protein structural dynamics, and provide a brief review on each category. We also lay out a plausible roadmap for future fs-TRXL studies for areas that have not been explored yet.

Energy, structure, and charge are fundamental quantities characterizing a molecule. Whereas the energy flow and structure change in chemical reactions are experimentally characterized, determining the atomic charges of a molecule in solution has been elusive, even for a triatomic molecule such as triiodide ion, I 3 − . Moreover, it remains to be answered how the charge distribution is coupled to the molecular geometry; which I-I bond, if two I-I bonds are unequal, dissociates depending on the electronic state. Here, femtosecond anisotropic x-ray solution scattering allows us to provide the following answers in addition to the overall rich structural dynamics. The analysis unravels that the negative charge of I 3 − is highly localized on the terminal iodine atom forming the longer bond with the central iodine atom, and the shorter I-I bond dissociates in the excited state, whereas the longer one in the ground state. We anticipate that this work may open a new avenue for studying the atomic charge distribution of molecules in solution and taking advantage of orientational information in anisotropic scattering data for solution-phase structural dynamics.

The photoactivation mechanism of Os3(CO)12 at 400 nm is examined with time-resolved X-ray liquidography. The data reveal two pathways: the vibrational relaxation following an internal conversion to the electronic ground state and the ligand dissociation to form Os3(CO)11 with a ligand vacancy at the axial position.

Nuclear spent fuel storage is one of the most significant problem spotlighted nowadays in nuclear industry due to its safety issues resulting from radioactivity [1]. Spent fuel storage system is largely classified into two methods; wet and dry process. Usually wet storage system is adopted due to its advantages of easier access to the fuel for detection of issues and being flexible approach. However, it has been reported that, in Republic of Korea (ROK), wet storage of nuclear spent fuel is over-saturated. Alternatively, nuclear spent fuel dry storage adoptions are under consideration, focusing on advanced cases of overseas. Dry storage system utilizes convection of air to cool the heat released from spent nuclear fuels. Dry storage systems are generally situated near the nuclear power plants which are located at the coastal region. High salinity and high humidity provided by the sea environment offer high corrosive environment to the materials used for dry storage system. Austenitic stainless steel (ASS), which is a material used for spent nuclear fuel containing canister, suffers various corrosion under the harsh environment of the seacoast. With welding process assisted, even more corrosion attacks will be served. In order to enhance the durability of the metals, various coating technologies are developed [2-4]. Among them, electrochemical anodization and cathodic plasma electrolytic oxidation (CPEO) are in the limelight for stainless steel (SS) corrosion protection [5,6]. Anodization and CPEO stand for similar concept of applying voltage to the metal in a certain electrolyte. As a result, metal oxide layer is fabricated in both ways. However, their reactions on the surface and morphologies differ with each method. In this study, comparison of the fabricated oxide layer on the metal surface through two different methods will be discussed. Surface morphologies, fabricated oxide layer depth, and finally their corrosion resistance properties are the main points of this research. By measuring their variety of characteristics, more effective coating method to improve the corrosion resistance of the SS will be identified.

In this study, we fabricated a nanoporous oxide layer by anodization to improve corrosion resistance of type 304 stainless steel (SS) gas tungsten arc weld (GTAW). Subsequent heat treatment was performed to eliminate any existing fluorine in the nanoporous oxide layer. Uniform structures and compositions were analyzed with field emission scanning electron microscope (FESEM) and X-ray diffractometer (XRD) measurements. The corrosion resistance of the treated SS was evaluated by applying a potentiodynamic polarization (PDP) technique and electrochemical impedance spectroscopy (EIS). Surface morphologies of welded SS with and without treatment were examined to compare their corrosion behaviors. All results indicate that corrosion resistance was enhanced, making the treatment process highly promising.

Fundamental studies of chemical reactions often consider the molecular dynamics along a reaction coordinate using a calculated or suggested potential energy surface1–5. But fully mapping such dynamics experimentally, by following all nuclear motions in a time-resolved manner—that is, the motions of wavepackets—is challenging and has not yet been realized even for the simple stereotypical bimolecular reaction6–8: A–B + C → A + B–C. Here we track the trajectories of these vibrational wavepackets during photoinduced bond formation of the gold trimer complex [Au(CN)2−]3 in an aqueous monomer solution, using femtosecond X-ray liquidography9–12 with X-ray free-electron lasers13,14. In the complex, which forms when three monomers A, B and C cluster together through non-covalent interactions15,16, the distance between A and B is shorter than that between B and C. Tracking the wavepacket in three-dimensional nuclear coordinates reveals that within the first 60 femtoseconds after photoexcitation, a covalent bond forms between A and B to give A–B + C. The second covalent bond, between B and C, subsequently forms within 360 femtoseconds to give a linear and covalently bonded trimer complex A–B–C. The trimer exhibits harmonic vibrations that we map and unambiguously assign to specific normal modes using only the experimental data. In principle, more intense X-rays could visualize the motion not only of highly scattering atoms such as gold but also of lighter atoms such as carbon and nitrogen, which will open the door to the direct tracking of the atomic motions involved in many chemical reactions. Femtosecond X-ray liquidography is used to track the vibrational wavepacket trajectories of gold atoms in solution, enabling time-resolved observations of the emergence of vibrations and the evolution of the formation of covalent bonds.

The effect of scintillator particle size on high-resolution X-ray imaging was studied using zinc tungstate (ZnWO4) particles. The ZnWO4 particles were fabricated through a solid-state reaction between zinc oxide and tungsten oxide at various temperatures, producing particles with average sizes of 176.4 nm, 626.7 nm, and 2.127 μm; the zinc oxide and tungsten oxide were created using anodization. The spatial resolutions of high-resolution X-ray images, obtained from utilizing the fabricated particles, were determined: particles with the average size of 176.4 nm produced the highest spatial resolution. The results demonstrate that high spatial resolution can be obtained from ZnWO4 nanoparticle scintillators that minimize optical diffusion by having a particle size that is smaller than the emission wavelength.