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Graphitic carbon nitride (CN), as a nonmetallic photocatalyst, has gained considerable attention for its cost‐effectiveness and environmentally friendly nature in catalyzing solar‐driven CO2 conversion into valuable products. However, the photocatalytic efficiency of CO2 reduction with CN remains low, accompanied by challenges in achieving desirable product selectivity. To address these limitations, a two‐step hydrothermal‐calcination tandem synthesis strategy is presented, introducing carbon quantum dots (CQDs) into CN and forming ultra‐thin CQD/CN nanosheets. The integration of CQDs induces a distinct work function with CN, creating a robust interface electric field after the combination. This electric field facilitates the accumulation of photoelectrons in the CQDs region, providing an abundant source of reduced electrons for the photocatalytic process. Remarkably, the CQD/CN nanosheets exhibit an average CO yield of 120 µmol g−1, showcasing an outstanding CO selectivity of 92.8%. The discovery in the work not only presents an innovative pathway for the development of high‐performance photocatalysts grounded in non‐metallic CN materials employing CQDs but also opens new avenues for versatile application prospects in environmental protection and sustainable cleaning energy. [ABSTRACT FROM AUTHOR]

Regulating bulk charge carrier transfer and surface catalytic reaction kinetics is thought a big challenge to photoelectrochemical (PEC) water splitting. Herein, the dual sites of CoNiP are delicately introduced into ZnIn2S4 (RZIS‐CoNiP) nanosheet arrays via a defect anchoring method. The paving [S─Ni─P] interfacial bond like a "bridge" can greatly reduce the phase resistance, improve the charge separation and migration, and promote the surface oxygen evolution reaction (OER) reaction. As expected, the optimized RZIS‐CoNiP photoanode achieved a maximum photocurrent density of 4.77 mA cm−2 at 1.23 V versus reversible hydrogen electrode (RHE) in neutral electrolyte solution without the presence of any sacrificial agents, which is ≈12 times higher than that of the pristine ZnIn2S4 under AM 1.5G illumination. And the amount of oxygen evolution for the RZIS‐CoNiP photoanode is as high as 21.9 µmol in 3 h. Transient spectroscopy measurements and density functional theory (DFT) calculations in situ discovered the mechanism of defect anchoring [S─Ni─P] bond on regulating charge transfer and surface reaction processes. This work provides a feasible anchoring interface route through defect engineering to regulate charge carrier transfer for PEC water splitting. [ABSTRACT FROM AUTHOR]

Abstract Graphitic carbon nitride (CN), as a nonmetallic photocatalyst, has gained considerable attention for its cost‐effectiveness and environmentally friendly nature in catalyzing solar‐driven CO2 conversion into valuable products. However, the photocatalytic efficiency of CO2 reduction with CN remains low, accompanied by challenges in achieving desirable product selectivity. To address these limitations, a two‐step hydrothermal‐calcination tandem synthesis strategy is presented, introducing carbon quantum dots (CQDs) into CN and forming ultra‐thin CQD/CN nanosheets. The integration of CQDs induces a distinct work function with CN, creating a robust interface electric field after the combination. This electric field facilitates the accumulation of photoelectrons in the CQDs region, providing an abundant source of reduced electrons for the photocatalytic process. Remarkably, the CQD/CN nanosheets exhibit an average CO yield of 120 µmol g−1, showcasing an outstanding CO selectivity of 92.8%. The discovery in the work not only presents an innovative pathway for the development of high‐performance photocatalysts grounded in non‐metallic CN materials employing CQDs but also opens new avenues for versatile application prospects in environmental protection and sustainable cleaning energy.

The rational design of an S‐scheme heterojunctions in hybrid semiconductors to realize separated charge carriers and sufficient redox ability is considered as an attractive way to achieve high photocatalytic activity in diluted CO2 reduction (DCR). An S‐scheme heterojunction formed in the fibrous Ta2O5/Ag2S nanostructures is proposed for improving the photocatalytic performance in DCR under simulated solar irradiation. Benchmark CH4 production rates of 132.3 µmol g−1 are obtained with 93.1% selectivity over optimal catalyst ASTO‐2. The remarkable activity in photocatalytic DCR of Ta2O5/Ag2S is attributed to the unique 0D/1D structure and effective charge separation by the photoinduced strong internal electric field and S‐scheme mechanism. The measurements of in situ X‐ray photoelectron spectroscopy, femtosecond transient absorption spectroscopy, and electron paramagnetic resonance further confirm the photoinduced carrier transfer pathways following the S‐scheme mechanism. This research can provide a new strategy for designing the S‐scheme heterojunctions to improve the photocatalytic performance of diluted CO2 conversion. [ABSTRACT FROM AUTHOR]

Polymer‐based dielectric nanocomposites with excellent high‐temperature energy storage performance are highly desirable in advanced electronic and power systems, but it remains a challenge to achieve superior breakdown strength at elevated temperatures. In this work, two‐dimensional (2D) magnesium oxide nanosheets (MgO NSs) are prepared by a hydrothermal method and used as fillers to fabricate MgO NSs/polyetherimide (PEI) dielectric nanocomposites. The effect of MgO NSs addition (1–4 wt%) on breakdown strength of MgO NSs/PEI nanocomposites is studied from 25 to 150°C. As a result, the nanocomposites containing 3 wt% MgO NSs obtain maximum breakdown strength of 538 kV mm−1 at 150°C, which is 25% higher than that of pure PEI and remains 92% of the room‐temperature value, accompany with an excellent discharged energy density of 3.66 J cm−3. The enhancement of breakdown strength could be attributed to the 2D structure and wide band gap (~7.8 eV) of MgO NSs, which act as barriers to suppress the electrical tree growth and create deep traps to capture charge, thus inhibiting the migration of charge carriers and suppressing electrical conduction. This work provides an effective approach for developing high‐temperature polymer‐based dielectric nanocomposites with high breakdown strength and discharged energy density. [ABSTRACT FROM AUTHOR]

Sunlight‐driven photoreduction of the environmentally mobile uranyl (VI) to less soluble tetravalent uranium is of considerable value to environmental sustainability, yet the pursuit for high‐performance semiconductors is plagued by the current disadvantages of inferior charge separation/migration. This study reports that a nickel single atom isolated on a sulfur‐functionalized graphitic carbon nitride/reduced graphene oxide 2D heterostructure enables exceptional uranyl photoreduction. Under only 11 min of visible light irradiation, the single atom anchored semiconductor yields a high removal rate of 99.8% and a record‐high extraction capacity of 4144 mg g−1 in uranyl‐containing wastewater and seawater. Theoretical calculations confirm that the remarkable uranyl photoreduction originates from the synergetic effect of Ni single atoms and intimate heterojunction establishment that can not only promote the separation/migration of photoexcited carriers, but also greatly reduce the energy barrier of uranyl reduction. This study showcases the exciting potential of single atom semiconductors for efficient uranyl removal from uranium‐contaminated aqueous environments. [ABSTRACT FROM AUTHOR]

Experimental and numerical studies on charge transport and liquid atomization with the consideration of electrohydrodynamics (EHD) have been performed for a high-speed rotary bell atomizer with internal charging system. The VOF-to-DPM hybrid model in the commercial CFD code ANSYS Fluent is used to investigate and analyse the liquid breakup. Furthermore, the charge conservation equation is solved not only considering flow convection but also the significant ion drift convection due to the presence of the strong electric field. We introduce the so-called apparent ion mobility coefficient that depends on the permittivity and conductivity of liquid, the film thickness on the bell surface and the electric field strength. With this model we can calculate the charge migration from the electrode, in this case the bell surface, to the liquid film and the droplets. Simulation results show an inhomogeneous charge distribution perpendicular to the bell surface, namely charge accumulating mainly on the film surface. Breakup simulations are carried out using a Newtonian liquid and a real paint. The electric body forces have been included in the Navier-Stokes equations. Effects of EHD on the liquid breakup are analysed. The relationship of droplet charge to droplet diameter is obtained, from which the total current is predicted that compared well with experiments. Simulation results deliver useful information for an improved understanding of the relevant physical processes. [Display omitted] [ABSTRACT FROM AUTHOR]

The present study is devoted to isolate and study the effect of charge migration on the photoionization from the X@C60. The noble gas atoms, Ar, Kr, and Xe, are confined in the C60 to investigate the impact of charge migration from the entrapped atom to the C60 side. The present work concludes that the confinement oscillations in the photoionization features are amplified due to the charge migration. Further, the angle-resolved, spin average time delay is also investigated in the light of confinement. Features in the time delay due to the charge migration are more amplified relative to those in the cross-section or angular distribution. [ABSTRACT FROM AUTHOR]

• Study of droplet coalescence under coupled shear and electric fields. • Increasing shear rate enhances droplet coalescence, yet surpassing the critical shear rate (γ = 7.5 × 109 s−1) results in elongation, impeding full coalescence. • Optimal droplet coalescence occurs at a θ = 25° angle, balancing shear force impact and horizontal electric field influence. • Droplet coalescence is primarily driven by shear forces, electrostatic attraction among water molecules, and directed charge migration. Water droplet coalescence in coupled flow and electric fields is a phenomenon extensively observed in petrochemical, microfluidic, and chemical synthesis processes; however, the existing research in this domain lacks the necessary depth. This paper employs a molecular dynamics approach to elucidate the microscopic mechanisms governing droplet aggregation in water-in-oil emulsions. The investigation spans various shear rates and droplet angles, considering droplet morphology and molecular interactions. The study reveals an interrelation between shear rate and droplet angle effects on droplet coalescence, both seeking to understand the impact of the flow field's shear effect on the electrocoalescence of water droplets. Increasing the shear rate proves advantageous to droplet aggregation up to a certain threshold; however, complete coalescence is hindered beyond the critical shear rate, γ = 7.5 × 109 s−1. Augmenting the droplet angle amplifies the shear force exerted by the flow field on the droplets, while diminishing the radial electric field force. Consequently, an optimal droplet angle of θ = 25° facilitates comprehensive droplet merging. The analysis of the coalescence process, interaction energy, charge density and radial distribution function shows that the approximate process of droplet motion is as follows: the shear effect drives the droplets to approach, and then the directional migration of charge and electrostatic attraction between water molecules drive the coalescence. The existence of a moderate shear effect enables complete droplet coalescence. This study offers theoretical guidance for the exploration of dynamic electrocoalescence technology. [ABSTRACT FROM AUTHOR]

Single-atom catalysts offer a representative platform for heterogeneous catalysis, owing to their maximum atom utilization efficiency and enhanced catalytic performance can be achieved by tuning the local atomic configuration. However, there are rare reports on the charge transfer process and its influence on local atomic configuration during the photocatalytic process. Herein, we for the first time observe the charge migration and bond evolution of a single-atom Pt/C 3 N 5 catalysts during the water splitting process by combining synchronous-illumination X-ray photoelectron spectroscopy (SI-XPS) with synchronous-illumination diffuse reflectance Fourier transform infrared spectroscopy (SI-DRIFTS). The results clearly reveal that the dynamic evolution of N-Ptδ+ (0 <δ < 2) bond not only provides a real transport channel for the rapid transferring of photo-induced electrons but also suppresses the reverse reaction of forming water from H 2 and O 2. Based on the above unique structure characterizations, single-atom Pt/C 3 N 5 catalysts exhibit significantly enhanced hydrogen evolution activity (18.2 mmol·g-1·h-1) under visible light in comparison with metallic Pt-C 3 N 5 (3.6 mmol·g-1·h-1). [Display omitted] • The charge transfer dynamic regulated via bond evolution over single-atoms Pt/C 3 N 5 was observed. • The novel SI-XPS and SI-DRIFTS techniques for photocatalytic mechanism study were first applied. • The rate of hydrogen evolution from single-atom Pt/C 3 N 5 was about 5.06 times than metallic Pt-C 3 N 5. • A new and valuable insight into the photocatalysis for water splitting was put forward. [ABSTRACT FROM AUTHOR]

Dye-sensitized photocatalytic water reduction hydrogen evolution (DS-PWRHE) with efficient spectral absorption and stable photoelectric conversion efficiency shows considerable application prospects for the conversion and storage of solar energy. The coupling interaction and charge migration between light-absorbing dye and sensitization matrix are crucial factors for improving the activities of DS-PWRHE. Herein, nitrogen-doping microporous carbon nanosheets (N-MCNs) as new-style sensitization matrix is synthesized by direct calcination method using ethylene diamine tetraacetic acid tetrasodium as raw material. Theoretical simulations find that N-MCNs with superior thermodynamic stability can optimize the charge distribution by implanting N heteroatoms in the limited carbon framework. The structural and performance tests indicate that the conductivity and adsorption properties of N-MCNs is greatly improved since a large of N heteroatoms not only act as boosters for carrier migration, but also are used as anchors for dye molecules. These superior physicochemical properties of N-MCNs as multifunctional sensitized matrix provide the prerequisite for H 2 generation occurring in DS-PWRHE system due to shorten transmission distance of photogenerated charges. The high-activity N-MCNs@Pt nanohybrid catalyst is prepared by in-situ photo-deposition method base on advantages of N-MCNs. Typically, in the neutral triethanolamine aqueous solution with Eosin Y dye-sensitized photocatalytic system, N-MCNs@Pt displays 685.8 μmol of H 2 for testing 120 min under visible light irradiation and 34.2 % of apparent quantum efficiency at 430 nm excitation. [Display omitted] • N-MCNs is thermodynamic stability and possesses three-dimensional frame nanostructure. • N atoms on the matrix surface optimize charge distribution and enhance dye adsorption. • N-MCNs is synthesized by direct calcination method using C 6 H 8 NNa 3 O 7 as a raw material. Stable DS-PWRHE activity of N-MCNs@Pt is 1.6 times than the H 2 evolved over GO@Pt [ABSTRACT FROM AUTHOR]

Coherent superposition of electronic states induces attosecond electron motion in molecules. We theoretically investigate the strong-field ionization of this superposition state by numerically solving the time-dependent Schrödinger equation. In the obtained photoelectron momentum distribution, an intriguing bifurcation structure appears in the strong-field holographic interference pattern. We demonstrate that this bifurcation structure directly provides complete information about the status of the transient wave function of the superposition state: the horizontal location of the bifurcation in the momentum distribution reveals the relative phase of the involved components of the superposition state and the vertical position indicates the relative coefficient. Thus, this bifurcation structure takes a snapshot of the transient electron wave packet of the superposition state and provides an intuitive way to monitor electron motion in molecules. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (CN), as a nonmetallic photocatalyst, has gained considerable attention for its cost-effectiveness and environmentally friendly nature in catalyzing solar-driven CO 2 conversion into valuable products. However, the photocatalytic efficiency of CO 2 reduction with CN remains low, accompanied by challenges in achieving desirable product selectivity. To address these limitations, a two-step hydrothermal-calcination tandem synthesis strategy is presented, introducing carbon quantum dots (CQDs) into CN and forming ultra-thin CQD/CN nanosheets. The integration of CQDs induces a distinct work function with CN, creating a robust interface electric field after the combination. This electric field facilitates the accumulation of photoelectrons in the CQDs region, providing an abundant source of reduced electrons for the photocatalytic process. Remarkably, the CQD/CN nanosheets exhibit an average CO yield of 120 µmol g -1 , showcasing an outstanding CO selectivity of 92.8%. The discovery in the work not only presents an innovative pathway for the development of high-performance photocatalysts grounded in non-metallic CN materials employing CQDs but also opens new avenues for versatile application prospects in environmental protection and sustainable cleaning energy., (© 2024 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Ferroptosis is an emerging non-apoptotic death process, mainly involving lipid peroxidation (LPO) caused by iron accumulation, which is potentially lethal to the intrinsically apoptotic-resistant malignant tumor. However, it is still restricted by the inherent antioxidant systems of tumor cells and the poor efficacy of traditional iron-based ferroptosis initiators. Herein, the study develops a novel ferroptosis-inducing agent based on PEGylated Cu + /Cu 2+ -doped black phosphorus@polypyrrole heterojunction (BP@CPP), which is constructed by utilizing the phosphate on the surface of BP to chelate Cu ions and initiating subsequent in situ polymerization of pyrrole. As a novel Z-scheme heterojunction, BP@CPP possesses an excellent photocatalytic activity in which the separated electron-hole pairs under laser irradiation endow it with powerful oxidizing and reducing capacities, which synergy with Cu + /Cu 2+ self-cycling catalyzing Fenton-like reaction to further strengthen reactive oxygen species (ROS) accumulation, glutathione (GSH) depletion, and glutathione peroxidase 4 (GPX4) inactivation, ultimately leading to efficient ferroptosis. Systematic in vitro and in vivo evaluations demonstrate that BP@CPP effectively inhibit tumor growth by inducing desired ferroptosis while maintaining a favorable biosafety in the body. Therefore, the developed BP@CPP-based ferroptosis initiator provides a promising strategy for ferroptosis-like cancer therapy., (© 2023 Wiley‐VCH GmbH.)

The photoinduced interlayer electron transfer in bilayer Langmuir–Blodgett films has been studied. The samples consisted of a monolayer of partially polymerized diacetylene molecules and a monolayer of phytochlorin-fullerene dyad molecules. The change in the resulting photovoltaic response of the samples over time after the cessation of the optical excitation pulse was analyzed with allowance for the migration of charges along the conjugated polymer chains and the effect of their length on the signal shape and its decay time. [ABSTRACT FROM AUTHOR]

We present a real‐time time dependent density functional theory approach to simulate charge migration of caffeine molecule after selective photoionization. According to the fact that the time evolution of the created hole can affect the molecular reaction and subsequent dynamics difference from its original structure, we studied the dominant frequency variation of caffeine charge oscillation after ionization of outer shell orbital. In this work, we determined the main orbitals participating in the total charge migration process by comparing the dipole moment peaks to the Fourier signals of the time dependent molecular orbitals (MOs) occupation. Having used the Bader charge analysis, we showed that different valence ionization of molecule resulted in a distinct charge migration between different regions, functional groups, and atoms of cations. We represented two interesting different cases: 1‐for ionization out from 46th MO of caffeine, the MOs interfere of the cation resulted in a charge migration between oxygen atoms and upper nitrogen of five‐membered ring, 2‐ for ionization out from 39th MO of caffeine, a different behavior of hole occurred according to which the hole spread throughout the whole molecule. Therefore, a specific MO ionization could result in a dramatically different migration and active site of cation. [ABSTRACT FROM AUTHOR]

In this article, we investigate the mechanisms of DNA ionization upon irradiation by 0.5 meV alpha particles. We focus on the sugar-phosphate group and its hydration shell. In radiation chemistry, the term quasi-direct effect refers the physical and chemical responses taking place after irradiation of solvent molecules pertaining to the solvation shells of solutes. The molecular mechanisms accounting for the quasi-direct effect are actually largely elusive, especially for those prevailing in the early timescales (< 10–12 s). We report Real-Time Time-Dependent Auxiliary Density Functional Theory simulations carried out within the framework of hybrid QM/MM scheme (Quantum Mechanics/Molecular Mechanics) with polarizable and non-polarizable embedding. Ten water molecules from the solvation shell of DNA backbone are independently irradiated. We find that during the first femtoseconds after irradiation, the holes formed on the irradiated water remain at their sites of formation. Electrostatic induction within the environment does not significantly impact charge migrations. We address the hypothesis that charge migration driven by electron correlation is responsible for an ultrafast H2O+ to DNA charge transfers, which would account for a quasi-direct effect. We find that pure charge migration at fixed nuclear positions is not responsible for the quasi-direct effect when considering sugar-phosphate solvation shells. [ABSTRACT FROM AUTHOR]

The overall water splitting efficiency is mainly restricted by the slow kinetics of oxygen evolution. Therefore, it is essential to develop active oxygen evolution catalysts. In this context, we designed and synthesized a tungsten oxide catalyst with oxygen vacancies for photocatalytic oxygen evolution, which exhibited a higher oxygen evolution rate of 683 μmol h−1 g−1 than that of pure WO3 (159 μmol h−1 g−1). Subsequent studies through transient absorption spectroscopy found that the oxygen vacancies can produce electron trapping states to inhibit the direct recombination of photogenerated carriers. Additionally, a Pt cocatalyst can promote electron trap states to participate in the reaction to improve the photocatalytic performance further. This work uses femtosecond transient absorption spectroscopy to explain the photocatalytic oxygen evolution mechanism of inorganic materials and provides new insights into the design of high‐efficiency water‐splitting catalysts. [ABSTRACT FROM AUTHOR]

The present study is devoted to isolate and study the effect of charge migration on the photoionization from the X@C60. The noble gas atoms, Ar, Kr, and Xe, are confined in the C60 to investigate the impact of charge migration from the entrapped atom to the C60 side. The present work concludes that the confinement oscillations in the photoionization features are amplified due to the charge migration. Further, the angle-resolved, spin average time delay is also investigated in the light of confinement. Features in the time delay due to the charge migration are more amplified relative to those in the cross-section or angular distribution.

Ionizing rays cause damage to genomes, proteins, and signaling pathways that normally regulate cell activity, with harmful consequences such as accelerated aging, tumors, and cancers but also with beneficial effects in the context of radiotherapies. While the great pace of research in the twentieth century led to the identification of the molecular mechanisms for chemical lesions on the building blocks of biomacromolecules, the last two decades have brought renewed questions, for example, regarding the formation of clustered damage or the rich chemistry involving the secondary electrons produced by radiolysis. Radiation chemistry is now meeting attosecond science, providing extraordinary opportunities to unravel the very first stages of biological matter radiolysis. This review provides an overview of the recent progress made in this direction, focusing mainly on the atto- to femto- to picosecond timescales. We review promising applications of time-dependent density functional theory in this context. [ABSTRACT FROM AUTHOR]

Vacuum ultraviolet photoionization of a gas‐phase oligonucleotide anion leads to the formation of a valence hole. This hole migrates towards an energetically favorable site where it can weaken bonds and ultimately lead to bond cleavage. We have studied Vacuum UV photoionization of deprotonated oligonucleotides containing the human telomere sequence dTTAGGG and G‐quadruplex structures consisting of four dTGGGGT single strands, stabilized by NH4+ counter ions. The oligonucleotide and G‐quadruplex anions were confined in a radiofrequency ion trap, interfaced with a synchrotron beamline and the photofragmentation was studied using time‐of‐flight mass spectrometry. Oligonucleotide 12‐mers containing the 5'‐TTAGGG sequence were found to predominantly break in the GGG region, whereas no selective bond cleavage region was observed for the reversed 5'‐GGGATT sequence. For G‐quadruplex structures, fragmentation was quenched and mostly non‐dissociative single and double electron removal was observed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The changes in the valence states of Fe and Co within the cocatalyst FeCo 2 O 4 facilitate the water oxidation reaction. • The MgO interlayer effectively inhibits the recombination of photogenerated carriers. • The reaction kinetics are enhanced by the super-hydrophilic nature of the photoanode surface. To address the issue of inefficient charge transfer efficiency at the semiconductor/cocatalyst interface, we engineered a BiVO 4 /MgO/FeCo 2 O 4 array, incorporating a MgO interlayer. This design aimed to enhance the performance of photoelectrochemical (PEC) water splitting on BiVO 4 and FeCo 2 O 4. The introduced interlayer efficiently hinders hole backflow, promoting unimpeded charge migration within the multi-hybrid structure. This, in turn, significantly reduces the recombination of electron-hole pairs. In addition, the BiVO 4 /MgO/FeCo 2 O 4 undergoes a low-temperature plasma treatment, resulting in super-hydrophilicity. This treatment enhances charge migration efficiency and fosters extensive contact between the electrolyte and electrode interfaces. Photoelectrochemical analysis demonstrates that H-BiVO 4 /MgO/FeCo 2 O 4 exhibits exceptional performance for the oxygen evolution reaction (OER), showcasing a photocurrent density of 4.3 mA·cm−2 at 1.23 V vs. RHE in 0.5 M Na 2 SO 4 under AM 1.5 G (100 mW·cm−2) illumination. Remarkably, this value is 5.2 times higher than that observed for BiVO 4. Furthermore, the maximum incident photon to current conversion efficiency (IPCE) reaches an impressive 61.7 %, surpassing that of BiVO 4 and BiVO 4 /FeCo 2 O 4 by approximately 5.1 and 1.7 times, respectively. Additionally, the charge separation efficiency of H-BiVO 4 /MgO/FeCo 2 O 4 achieves a notable 83.4 %, and the charge injection efficiency is substantially improved. This study advocates for a straightforward yet highly effective approach to mitigate interfacial electron-hole recombination. [ABSTRACT FROM AUTHOR]

• Visible-light-responsive CdS@V-ZnIn 2 S 4 photocatalyst was prepared for the first time. • Vacancy-engineered composite endowed supreme photocatalytic activity compared with bare counterparts. • High TC degradation and H 2 O 2 production efficiencies are verified upon irradiation. • Both ESR and reactive radicals scavenging analysis demonstrate the photocatalysis mechanism. The efficient type-II heterostructures hold great interest in the development of photocatalysts that respond to ultraviolet- (UV) to visible light (Vis) and possess numerous advantageous physicochemical properties that can enhance their ability toward robust environmental decontamination upon exposure to solar light. Herein, we designed a range of type-II n-n photocatalysts comprising immobilized CdS on sulfur-vacancy-rich ZnIn 2 S 4 (CdS@V-ZIS) through the two-step synthesis approach. The catalytic activities of CdS@V-ZIS heterostructures were evaluated for the photocatalytic degradation of tetracycline (TC) and in-situ production of H 2 O 2 under simulated solar-light irradiation. Benefiting from the extended light-absorption edge, well-aligned band structure, and built-in electric field, the optimum heterostructure sample (CdS@V-ZIS-0.5) achieved an impressive removal activity of 98.6 % and mineralization efficiency of 65.1 %. Through the electron spin resonance and reactive radical-scavenging techniques, it was determined that the primary active species responsible for the removal of TC were hydroxyl and superoxide radicals. The transport path of charge carriers and possible photocatalytic mechanism were thoroughly investigated by the analyses of ultraviolet photoelectron spectroscopy, valence-band X-ray photoelectron spectroscopy, and diffusion reflectance spectroscopy. Regarding the photocatalytic experiments, the in-situ hydrogen peroxide generation rate over CdS@V-ZIS-0.5 attained 4.012 mmol L−1, which was 1.62 and 2.99 times higher than that of V-ZIS and CdS, respectively. We expect that our research will open up new avenues toward the development of novel heterojunctions along with interfacial engineering, which can significantly enhance the effectiveness of water purification systems. [Display omitted] [ABSTRACT FROM AUTHOR]

The dynamic evolutions of atomic and electronic structure on Cu 2 MoS 4 catalysts were firstly explored by combining synchronous-illumination X-ray photoelectron spectroscopy with X-ray diffraction. Benefitting from the above structure characteristics, Cu 2 MoS 4 nanosheets exhibit excellent activity enhancement (8.7 μmol g−1 h−1) for CO 2 reduction to C 2 H 4 under the visible light irradiation in comparison with the trace amount of Cu-doped MoS 2 and pure MoS 2. [Display omitted] • The dynamic evolutions of surface structures in Cu 2 MoS 4 nanosheets were observed. • The novel SI-XPS and SI-XRD technologies were first applied. • The Cu 2 MoS 4 nanosheets exhibited excellent photocatalytic CO 2 to C 2 H 4 activity. • A new and valuable insight into the photocatalysis for CO 2 reduction was put forward. Understanding the charge dynamic behavior of the catalyst is crucial to unravel the underlying mechanism for photocatalytic CO 2 reduction to C 2+ products. However, the structure–activity relationships are not intuitive because of the dynamic evolution of electronic and atomic structures for catalysts under the excitation state. Herein, modeling on layered Cu 2 MoS 4 nanosheets, we for the first time observe charge migration-induced evolution of electronic and atomic structure on Cu 2 MoS 4 catalyst during the CO 2 reduction process by combining synchronous-illumination X-ray photoelectron spectroscopy (SI-XPS) with X-ray diffraction (SI-XRD). During the dissociation of CO 2 molecules as well as the charge migration process under the visible light irradiation condition, the surface S atoms return back to the lattice phase, leading to the valence-state normalization of Cu, Mo and S atoms and the increases of the interlayer lattice spacing. By virtue of the above unique characteristic changes, Cu 2 MoS 4 nanosheets exhibit excellent activity enhancement (8.7 μmol g−1 h−1) for CO 2 reduction to C 2 H 4 under the visible light irradiation in comparison with the trace amount of Cu-doped MoS 2 and pure MoS 2. [ABSTRACT FROM AUTHOR]

• The hollow-sphere g-C 3 N 4 was used as a substrate material for uniformly dispersing Pd nanoparticles to expose more active sites. • The synergistic effect of the 3D g-C 3 N 4 and Pd nanoparticles promoted efficient separation of photogenerated carriers. • According to TAS, it was estimated that the charge separated state lifetime of Pd/g-CN (10 h) was shortened to 1.4 ns ± 338.0 ps. Herein, 3D hollow-sphere structure graphitic carbon nitride (g-C 3 N 4) with large specific surface area and high porosity is synthesized through a mild, heat polymerization, template-free route. The as-prepared hollow-sphere structure can be used as a substrate material for uniformly dispersing Pd nanoparticles to enhance the absorption of visible light and expose more active sites. Pd nanoparticles as electron acceptor are implanted into g-C 3 N 4 , which increases the trapping capability of capturing transition electrons to gain more photogenerated carriers participating in surface reactions. Therefore, the estimated charge separation lifetime of Pd/SCN (10 h) investigated by transient absorption spectroscopy was 1.4 ns ± 338.0 ps, which is only half of SCN. Benefiting from the unique structure and the excellent optical performance, the obtained Pd/SCN composites exhibited prominent photocatalytic hydrogen evolution performance under visible light irradiation. Especially, the photocatalytic hydrogen rate of Pd/SCN (10 h) reached 267.9 µmol/h, almost 10 times higher than the Pd/2D g-C 3 N 4. Simultaneously, a possible mechanism for photocatalytic H 2 reaction was proposed based on the characterization results. [ABSTRACT FROM AUTHOR]

A highly efficient Z‐scheme photocatalytic system constructed with 1D CdS and 2D CoS2 exhibited high photocatalytic hydrogen‐evolution activity of 5.54 mmol h−1 g−1 with an apparent quantum efficiency of 10.2 % at 420 nm. More importantly, its interfacial charge migration pathway was unraveled: The electrons are efficiently transferred from CdS to CoS2 through a transition atomic layer connected by Co–S5.8 coordination, thus resulting in more photogenerated carriers participating in surface reactions. Furthermore, the charge‐trapping and charge‐transfer processes were investigated by transient absorption spectroscopy, which gave an estimated charge‐separation yield of approximately 91.5 % and a charge‐separated‐state lifetime of approximately (5.2±0.5) ns in CdS/CoS2. This study elucidates the key role of interfacial atomic layers in heterojunctions and will facilitate the development of more efficient Z‐scheme photocatalytic systems. [ABSTRACT FROM AUTHOR]

The ability to produce ultrashort, high-brightness X-ray pulses is revolutionizing the field of ultrafast X-ray spectroscopy. Free-electron laser (FEL) facilities are driving this revolution, but unique aspects of the FEL process make the required characterization and use of the pulses challenging. In this paper, we describe a number of developments in the generation of ultrashort X-ray FEL pulses, and the concomitant progress in the experimental capabilities necessary for their characterization and use at the Linac Coherent Light Source. This includes the development of sub-femtosecond hard and soft X-ray pulses, along with ultrafast characterization techniques for these pulses. We also describe improved techniques for optical cross-correlation as needed to address the persistent challenge of external optical laser synchronization with these ultrashort X-ray pulses. [ABSTRACT FROM AUTHOR]

Electron coherence is a fundamental quantum phenomenon in today's ultrafast physics and chemistry research. Based on attosecond pump–probe schemes, ultrafast X-ray photoelectron imaging of molecules was used to monitor the coherent electron dynamics which is created by an XUV pulse. We performed simulations on the molecular ion H 2 + by numerically solving time-dependent Schrödinger equations. It was found that the X-ray photoelectron angular and momentum distributions depend on the time delay between the XUV pump and soft X-ray probe pulses. Varying the polarization and helicity of the soft X-ray probe pulse gave rise to a modulation of the time-resolved photoelectron distributions. The present results provide a new approach for exploring ultrafast coherent electron dynamics and charge migration in reactions of molecules on the attosecond time scale. [ABSTRACT FROM AUTHOR]

Graphene has attracted much attention due to its advanced properties. In previous work, the relationship between temperature and the conductivity of epoxy‐based nanocomposite filled with graphene oxide has been experimentally studied. To understand the charge transport behaviour, the space charge characteristics at different temperatures and field strengths are measured with an improved pulsed electroacoustic measurement system, which is designed for high‐temperature space charge measurement. From the measurement results, epoxy resin (ER) filled with multi‐layer graphene oxide (MGO/ER) shows suppressed charge migration while ER filled with single‐layer graphene oxide (SGO/ER) shows a hetero charge accumulation, which is assumed to be caused by the partial reduction of graphene oxide to graphene. Compared to pure ER, the apparent mobility of the nanocomposites is smaller while the trap depth and number of trapped charges are larger, which is probably caused by the introduction of traps. In the simulation, the relationship between mobility, trap depth, trap density and charge distribution are firstly studied. Then the calculated values of mobility and trap depth are given to the parameters to compare the simulated charge profiles with experiment results. The simulation results agree well qualitatively with the experimental results, giving some support for the proposed explanations. [ABSTRACT FROM AUTHOR]

Graphical abstract Br-doped Bi 2 O 2 CO 3 (BOC) nanosheets were facilely prepared by a one-step hydrothermal reaction. The interstitial Br-doping generates delocalized impurity states at the Fermi level, which results in accelerated charge migration and broadened light-harvesting. Due to the combinative merit of improved electronic structure and more exposed {0 0 1} active facets, the Br-BOC exhibits obviously enhanced photoactivity. Highlights • Br-doped Bi 2 O 2 CO 3 nanosheets with exposed {0 0 1} facets were facilely prepared. • DFT calculation confirms that Br- dopes into the interstitial sites of Bi 2 O 2 CO 3. • The Br-doping improves the electronic structure and accelerates charge migration. • The Br-doping results in an enhanced photoactivity of 3.6 folds than pure Bi 2 O 2 CO 3. • The migration mechanism of photoinduced carriers on Br-Bi 2 O 2 CO 3 surface is proposed. Abstract The work presents a combinative merit of non-metal ion doping and active facet effect of Bi 2 O 2 CO 3 photocatalyst. Br-doped Bi 2 O 2 CO 3 nanosheets with exposed {0 0 1} facets were facilely prepared via a one-step hydrothermal reaction with the assistance of cetyltrimethylammonium bromide (CTAB) at a mild temperature of 60 °C for 4 h. The presence of CTAB not only influences the growth of Bi 2 O 2 CO 3 crystalline but also leads to a Br-doping. Based on the crystal structure and DFT calculation, bromine from CTAB as dopant interstitially incorporates into Bi 2 O 2 CO 3 lattice, which alters the band gap positions of Bi 2 O 2 CO 3 and generates delocalized impurity states at the Fermi level. The improved electronic structure endows Br-doped Bi 2 O 2 CO 3 with a broadened light-harvesting and accelarated charge migration. In addition, the thin nanosheet means more exposure of {0 0 1} active facets and larger internal electric field, which would also benefit for the charge separation. The sample with a trace Br content of 1.17 wt% shows the best degradation efficiency for RhB with a rate constant k enhanced by 3.6 folds compared with that of pure Bi 2 O 2 CO 3 under simulated solar irradiation. Combining the effective catalytic sites and the detected active species, a possible migration mechanism of photogenerated e−/h+ pairs on the surface of Br-doped Bi 2 O 2 CO 3 nanosheet is proposed. The work provides some new insights into the rational design and synthesis of non-metal doped semiconductor photocatalyst with facet dependency. [ABSTRACT FROM AUTHOR]

This article starts with an introductory survey of previous work on breaking and restoring the electronic structure symmetry of atoms and molecules by means of two laser pulses. Accordingly, the first pulse breaks the symmetry of the system in its ground state with irreducible representation I R R E P g by exciting it to a superposition of the ground state and an excited state with different I R R E P e . The superposition state is non-stationary, representing charge migration with period T in the sub- to few femtosecond time domains. The second pulse stops charge migration and restores symmetry by de-exciting the superposition state back to the ground state. Here, we present a new strategy for symmetry restoration: The second laser pulse excites the superposition state to the excited state, which has the same symmetry as the ground state, but different I R R E P e . The success depends on perfect time delay between the laser pulses, with precision of few attoseconds. The new strategy is demonstrated by quantum dynamics simulation for an oriented model system, benzene. [ABSTRACT FROM AUTHOR]

Quantum simulations of the electron dynamics of oriented benzene and Mg-porphyrin driven by short (6h and D4h of the nuclear scaffolds are conserved. At the same time, the symmetries of the one-electron densities are broken, however, to specific subgroups of G for the excited superposition states. These subgroups depend on the polarization and on the electric fields of the laser pulses. They can be determined either by inspection of the symmetry elements of the one-electron density which represents charge migration after the laser pulse, or by a new and more efficient group-theoretical approach. The results agree perfectly with each other. They suggest laser control of symmetry breaking. The choice of the target subgroup is restricted, however, by a new theorem, i.e., it must contain the symmetry group of the time-dependent electronic Hamiltonian of the oriented molecule interacting with the laser pulse(s). This theorem can also be applied to confirm or to falsify complementary suggestions of electron symmetry breaking by laser pulses.

• Full solar-light-spectrum active V-Bi 2 S 3-x Se x photocatalyst was prepared for the first time. • Doped and defected endowed the superb photocatalytic activity over bare counterparts. • High Cr(VI) reduction and H 2 O 2 generation efficiencies are achieved under illumination. • Both ESR and species trapping analysis reveal the photocatalysis mechanism. Heterogeneous photocatalysis has been demonstrated as a highly effective approach in addressing the difficulties encountered by conventional technologies in environmental remediation. Herein, for the first time, a novel hierarchical photocatalyst of selenium-doped Bi 2 S 3 (Bi 2 S 3-x Se x) was successfully synthesized through a one-spot hydrothermal route followed by a vacancy engineering process (V-Bi 2 S 3-x Se x). The photocatalytic reduction of Cr(VI) and in-situ generation of hydrogen peroxide (H 2 O 2) under simulated solar-light irradiation were performed to evaluate the catalytic activity of the as-prepared samples. The catalytic activity of as-prepared samples was evaluated toward the photocatalytic reduction of Cr(VI) and in-situ generation of H 2 O 2 under simulated solar-light irradiation. Notably, V-Bi 2 S 3-x Se x (V-BSSe-5, as optimum sample) exhibited a photo-reduction of Cr(VI) at a rate of 97.04% during 150 min, which was 1.53- and 1.39-fold higher than those of pure Bi 2 S 3 and Bi 2 Se 3 , respectively. Interestingly, the V-Bi 2 S 3-x Se x photocatalyst not only harvested more incident light in the UV–vis and near-infrared (NIR) regions but also supplied many active sites, improving the promotion of photo-generated charge-carriers, inhibiting charge recombination, and thus enhancing the photocatalytic activity. In addition, V-BSSe-5 showed greater photocatalytic efficiency for H 2 O 2 generation, which was 15.69, 10.07, and 1.79 times higher than those of Bi 2 S 3 , Bi 2 Se 3 , and BSSe-5, respectively. The charge-carrier migration pathway and possible photocatalytic mechanisms were systematically discussed by assisting the electron spin resonance and ultraviolet photoelectron spectroscopy analyses. The findings of this study demonstrate that doping and defect engineering strategies have the potential to be a significant advancement in the development of visible- and NIR-light responsiveness photocatalysts, thereby providing a solution to current environmental and energy challenges. [Display omitted] [ABSTRACT FROM AUTHOR]

We demonstrate that charge migration can be ‘engineered’ in arbitrary molecular systems if a single localised orbital - that diabatically follows nuclear displacements - is ionised. Specifically, we describe the use of natural bonding orbitals in Complete Active Space Configuration Interaction (CASCI) calculations to form cationic states with localised charge, providing consistently well-defined initial conditions across a zero point energy vibrational ensemble of molecular geometries. In Ehrenfest dynamics simulations following localised ionisation of -electrons in model polyenes (hexatriene and decapentaene) and -electrons in glycine, oscillatory charge migration can be observed for several femtoseconds before dephasing. Including nuclear motion leads to slower dephasing compared to fixed-geometry electron-only dynamics results. For future work, we discuss the possibility of designing laser pulses that would lead to charge migration that is experimentally observable, based on the proposed diabatic orbital approach. [ABSTRACT FROM AUTHOR]

Featured Application: We present a new computational method that can be used to investigate the quantum dynamics of one- or two-electron systems during interaction with an ultrashort laser pulse, including nuclear dynamics. The inclusion of both electronic and nuclear degrees of freedom allows for a description of a wide range of processes, including charge migration during the nuclear dissociation process. In this report, we introduce the static coherent states (SCS) method for investigating quantum electron dynamics in a one- or two-electron laser-induced system. The SCS method solves the time-dependent Schrödinger equation (TDSE) both in imaginary and real times on the basis of a static grid of coherent states (CSs). Moreover, we consider classical dynamics for the nuclei by solving their Newtonian equations of motion. By implementing classical nuclear dynamics, we compute the electronic-state potential energy curves of H 2 + in the absence and presence of an ultra-short intense laser field. We used this method to investigate charge migration in H 2 + . In particular, we found that the charge migration time increased exponentially with inter-nuclear distance. We also observed substantial charge localization for sufficiently long molecular bonds. [ABSTRACT FROM AUTHOR]

Abstract: The description of the electronic structure of molecules in terms of molecular orbitals is a highly successful concept in chemistry. However, it commonly fails if the electrons in a molecule are strongly correlated and cannot be treated as independent particles. Electron correlation is essential to understand inner‐valence X‐ray spectroscopies, it can drive ultrafast charge migration in molecules, and it is responsible for many exotic properties of strongly correlated materials. Time‐resolved spectroscopy with attosecond resolution is generally capable of following electronic motion in real time and can thus provide experimental access to electron‐correlation‐driven phenomena. High‐harmonic spectroscopy in particular uses the precisely timed laser‐driven recollision of electrons to interrogate the electronic structure and dynamics of the investigated system on a sub‐femtosecond timescale. In this Review, the capabilities of high‐harmonic spectroscopy to follow electronic motion in molecules are discussed. Both qualitative and quantitative approaches to unraveling the detailed dynamical responses of molecular systems following ionization are presented. A new theoretical formalism for the reconstruction of correlation‐driven charge migration is introduced. The importance of electron–ion entanglement and electronic coherence in the reconstruction of attosecond hole dynamics are discussed. These advances make high‐harmonic spectroscopy a promising technique to decode fundamental electron correlations and to provide experimental data on the complex manifestations of multi‐electron dynamics. [ABSTRACT FROM AUTHOR]

The disturbance mechanism of dummy cell during memory cell cycling has been investigated in 3D NAND flash. Edge dummy cell (DMY) threshold voltage increasing was observed during cell program and erase cycling, which leads to a reduced string current and read failure. According to experiment and TCAD analysis, two mechanisms were identified to contribute to the dummy disturbance: one is the tunneling of electrons from the adjacent gate to the trapping layer during cell erase condition, which was also observed in 2D NAND; the other one is the lateral charge spreading from the trapping layer of edge cell to DMY, which is a new observation for the junction-less 3D NAND with continuous nitride trapping layer. Furthermore, an optimal DMY bias scheme under erase operation is demonstrated to suppress the disturbance. [ABSTRACT FROM PUBLISHER]

Electron coherence is a fundamental quantum phenomenon in today’s ultrafast physics and chemistry research. Based on attosecond pump–probe schemes, ultrafast X-ray photoelectron imaging of molecules was used to monitor the coherent electron dynamics which is created by an XUV pulse. We performed simulations on the molecular ion H 2 + by numerically solving time-dependent Schrödinger equations. It was found that the X-ray photoelectron angular and momentum distributions depend on the time delay between the XUV pump and soft X-ray probe pulses. Varying the polarization and helicity of the soft X-ray probe pulse gave rise to a modulation of the time-resolved photoelectron distributions. The present results provide a new approach for exploring ultrafast coherent electron dynamics and charge migration in reactions of molecules on the attosecond time scale.

This article starts with an introductory survey of previous work on breaking and restoringthe electronic structure symmetry of atoms and molecules by means of two laser pulses. Accordingly,the first pulse breaks the symmetry of the system in its ground state with irreducible representationIRREPg by exciting it to a superposition of the ground state and an excited state with differentIRREPe. The superposition state is non-stationary, representing charge migration with period T inthe sub- to few femtosecond time domains. The second pulse stops charge migration and restoressymmetry by de-exciting the superposition state back to the ground state. Here, we present a newstrategy for symmetry restoration: The second laser pulse excites the superposition state to the excitedstate, which has the same symmetry as the ground state, but different IRREPe. The success dependson perfect time delay between the laser pulses, with precision of few attoseconds. The new strategyis demonstrated by quantum dynamics simulation for an oriented model system, benzene.

Because the development of attopulses, charge migration induced by short optical pulses has been extensively investigated. We report a computational purely electronic dynamical study of ultrafast few femtoseconds (fs) charge transfer and charge migration in realistic passivated stoichiometric Au11 and Au20 gold nanoclusters functionalized by a bipyridine ligand. We show that a net significant amount of electronic charge (0.1 to 0.4 ∣e∣ where ∣e∣ is the electron charge) is permanently transferred from the bipyridine chromophore to the gold cluster during the short 5-6 fs UV-vis strong pulse. This electron transfer to the metallic core is induced by the optical excitation of electronic states with a partial charge transfer character involving the chromophore before the onset of nuclei motion. In addition, the photoexcitation by the strong fs pulse builds a nonequilibrium electronic density that beats between the chromophore and the metallic core around the average of the transferred value. Modular systems made of a donor chromophore that can be photoexcited in the UV-vis range coupled to an efficient acceptor that could trap the charge are of interest for applications to nanodevices. Our study provides understanding on the very early, purely electronic dynamics built by the fs optical excitation and the initial charge separation step. [ABSTRACT FROM AUTHOR]

Recently, it was discovered that excitation of the oriented model benzene from its aromatic electronic ground state S 0 ( 1 A 1 g ) to the non-aromatic S 0 + S 2 ( 1 B 1 u ) superposition state generates negative and positive partial charges on alternating carbon atoms. Subsequently, they vary periodically, due to adiabatic attosecond charge migration AACM. Here, we determine the angular electronic flux that mediates this new type of AACM, by means of quantum dynamics simulations. It is found to be periodic, with period τ ¯ = 590 as , and with a pincer motion type pattern such that a total of 1.2 valence electrons flow concertedly between alternating sources and sinks at the carbon nuclei. [ABSTRACT FROM AUTHOR]

Recently, it was shown that a well-designed laser pulse may prepare an oriented linear molecular ion in a specific superposition state of the electronic ground (g) and first excited (e) states, with different amplitudes and non-zero phases. The reconstruction of the initial state, with time resolution of 100 attoseconds (as), yields the subsequent charge migration that proceeds adiabatically, on the attosecond time scale (AACM). We develop the theory for the time evolutions of the axial density and the flux of the electrons, during AACM. The flux is obtained by simple scaling and time-shifting the results for the ‘reference’ scenario with equal amplitudes and zero phases. Application to the system HCCI+confirms periodic AACM of a rather small number (0.663) of valence electrons, from the acetylenic moiety to the domain of the iodine, and back, with period= 1.85 fs. The underlying axial electronic flux is always unidirectional, with maximum absolute value at the border between the acetylenic moiety and the domain of the iodine, close to the local minimum of the axial density of the valence electrons and to its zero time derivative. The theoretical results imply new challenges for experiment, e.g. one should apply optimal control to steer AACM with maximum electronic flux, and one should investigate its initiation with time resolution below 100 as. [ABSTRACT FROM AUTHOR]

Using direct search algorithms for solving the quantum optimization problem, we demonstrate on model systems that with specifically tailored Gaussian-form laser pulses one can achieve a very good control over the dynamics in complicated quantum systems. We show that by manipulating a very limited number of laser-pulse parameters, one is able to control the charge migration process in molecules. In particular, by combining two identical Gaussian laser pulses with an appropriate delay between them, one can stop the pure electronic, few-femtosecond oscillation of the charge, redistributing it along the molecule of propiolic acid. [ABSTRACT FROM AUTHOR]

Adiabatic attosecond charge migration (AACM) in a linear molecule or cation such as HCCI+ means that the system has been prepared in a superposition state e.g. of the electronic ground and first excited states, corresponding to a surplus of density of valence electrons on one side which is compensated by a deficit of electron density on the other side. Subsequently, the surplus and deficit interchange such that the surplus of electron density migrates from its initial site to the opposite site, and back, periodically. The migration proceeds adiabatically on the attosecond time domain, i.e. without diabatic transitions between eigenstates. It is associated with electronic flux that mediates the charge migration. Here, we tailor a femtosecond p/2 laser pulse such that it induces AACM in the oriented model HCCI+, with maximum electronic flux. The case study shows that the flux is generated already during the laser pulse, suggesting equivalent processes during laser initiations of AACM in many or all other systems. The results are obtained by means of quantum dynamics simulation. [ABSTRACT FROM AUTHOR]