Electron Reservoir Research Articles

Irradiation of Plutonium Tributyl Phosphate Complexes by Ionizing Alpha Particles: A Computational Study.

The PUREX solvent extraction process, widely used for recovering uranium and plutonium from spent nuclear fuel, utilizes an organic solvent composed of tributyl phosphate (TBP). The emission of ionizing particles such as alpha particles, resulting from the decay of plutonium, makes the organic solvent vulnerable to degradation. Here, we study the ultrashort time alpha irradiation of tributylphosphate (TBP) and Pu(NO3)4(TBP)2 complex formed in the PUREX process. Electron dynamics is propagated by Real-Time-Dependent Auxiliary Density Functional Theory (RT-TD-ADFT). We investigate the use of previously proposed absorption boundary conditions (ABC) in the molecular orbital space to treat secondary electron emission. Basis set and exchange correlation functional effects with ABC are reported as well as a detailed analysis of the ABC parametrization. Preliminary results on the water molecule and then on TBP show that the phenomenological nature of the ABC parameters necessitates selecting appropriate values for each system under study. Irradiation of free and complexed TBP shows an influence of the ligands on the variation of atomic charges on the femtosecond time scale. An accumulation of atomic charges in the alkyl chains of TBP is observed in the case where the nitrate groups are predominantly irradiated. In addition, we find that the Pu atom regains its electric charge very rapidly after being hit by the projectile, with the coordination sphere serving as an electron reservoir to preserve its formal redox state. This study paves the road toward a full understanding of the degradation of organic extracants employed in the nuclear industry.

The Old Polyoxometalates in New Application as Molecular Resistive Switching Memristors

AbstractThe coming big‐data era has created a huge demand for next‐generation memory technologies with characters of higher data‐storage densities, faster access speeds, lower power consumption and better environmental compatibility. In this field, the design of resistive switching active materials is pivotal but challengeable. Polyoxometalates (POMs) are promising candidates for next‐generation molecular memristors due to their versatile redox characters, excellent electron reservoirs and good compatibility/convenience in microelectronics processing. In this review, five kinds of POM‐based active materials in nonvolatile memories (inorganic POMs, crystalline organic‐inorganic hybrid POMOFs, polymer modified POMs, POM/transition metal oxides composites and the deposition of POM on metal surfaces) were described. The components of POMs active materials, device fabrications, device parameters, and resistive switching mechanisms relative to their structures were summarized. Finally, challenges and future perspectives of POMs‐based memristors were also presented.

Primary amines as ligands and linkers in complexes of tripyrrindione radicals

Biopyrrin pigments, which result from the degradation of heme in biological settings, feature three or two pyrrole rings and characteristic pyrrolin-2-one termini. These scaffolds serve as redox-active ligands and electron reservoirs in coordination compounds. Tripyrrin-1,14-dione coordinates divalent transition metals as a dianionic ligand hosting a delocalized radical. Herein, we report the synthesis and characterization of palladium(II) and platinum(II) tripyrrindione complexes featuring a primary amine (i.e., aniline, tert-butylamine, 1,2-ethylenediamine) at the fourth coordination site within square planar geometries. Interligand hydrogen-bonding interactions are observed between the coordinated amine and the carbonyl groups on the tripyrrindione scaffold. Notably, 1,2-ethylenediamine is employed to link two Pt(II) tripyrrindione complexes. As revealed by optical absorption and electron paramagnetic resonance (EPR) spectroscopy, all resulting complexes present ligand-based radicals that are stable at room temperature and when exposed to air. Spin pairing through multicenter interactions leads to [Formula: see text]-dimerization of the tripyrrindione radicals and a decrease in the EPR signal at low temperatures. Electrochemical measurements indicate that the ligand system undergoes quasi-reversible one-electron oxidation and reduction, thus confirming the ability of tripyrrindione to form square planar complexes in three different redox states.

Activation of Dinitrogen Promoted by Adsorption of C6H6 on Fe2VC- Cluster Anions.

The introduction of organic ligands is one of the effective strategies to improve the stability and reactivity of metal clusters. Herein, the enhanced reactivity of benzene-ligated cluster anions Fe2VC(C6H6)- with respect to naked Fe2VC- is identified. Structural characterization suggests that C6H6 is molecularly bound to the dual metal site in Fe2VC(C6H6)-. Mechanistic details reveal that the cleavage of N≡N is feasible in Fe2VC(C6H6)-/N2 but hindered by an overall positive barrier in the Fe2VC-/N2 system. Further analysis discloses that the ligated C6H6 regulates the compositions and energy levels of the active orbitals of the metal clusters. More importantly, C6H6 serves as an electron reservoir for the reduction of N2 to lower the crucial energy barrier of N≡N splitting. This work demonstrates that the flexibility of C6H6 in terms of withdrawing and donating electrons is crucial to regulating the electronic structures of the metal cluster and enhancing the reactivity.

Hydrothermal preparation of C3N4 on carbonized wood for photothermal-photocatalytic water splitting to efficiently evolve hydrogen

Hydrogen generation by photocatalysis is one of the most effective approaches to rationally utilize solar energy. In this work, we designed a biphasic photothermal-photocatalytic system. Spherical g-C3N4 (HCN) was grown on the carbonized wood (CW) by a one-step hydrothermal method. The carbonization layer in carbonized wood/spherical g-C3N4 (CW-HCN) system was able to further enhance the photothermal conversion of water steam production by improving the absorption of solar radiation. In addition, the temperature was increased due to photothermal effect, which was beneficial for H2 evolution reaction. Moreover, the carbonized layer could act as a reservoir for photogenerated electrons on g-C3N4, which could accelerate the charge separation. Benefiting from all above-mentioned merits, the H2 evolution rate of CW-HCN system under simulated sunlight reached 2700.18 μmol/m2/h, which was 42.23 times higher than that of pristine g-C3N4 powder directly dispersed in water. In addition, the CW-HCN system exhibited broad applicability, maintaining the H2 evolution activity of 2013.29 μmol/m2/h with seawater as water resource. This work provided a new strategy for highly efficient H2 evolution.

Novel Semiconductive Ternary Hybrid Heterostructures for Artificial Optoelectronic Synapses.

Synaptic devices that mimic biological synapses are considered as promising candidates for brain-inspired devices, offering the functionalities in neuromorphic computing. However, modulation of emerging optoelectronic synaptic devices has rarely been reported. Herein, a semiconductive ternary hybrid heterostructure is prepared with a D-D'-A configuration by introducing polyoxometalate (POM) as an additional electroactive donor (D') into a metalloviologen-based D-A framework. The obtained material features an unprecedented porous 8-connected bcu-net that accommodates nanoscale [α-SiW12 O40 ]4- counterions, displaying uncommon optoelectronic responses. Besides, the fabricated synaptic device based on this material can achieve dual-modulation of synaptic plasticity due to the synergetic effect of electron reservoir POM and photoinduced electron transfer. And it can successfully simulate learning and memory processes similar to those in biological systems. The result provides a facile and effective strategy to customize multi-modality artificial synapses in the field of crystal engineering, which opens a new direction for developing high-performance neuromorphic devices.

Experimental demonstration of a skyrmion-enhanced strain-mediated physical reservoir computing system

Physical reservoirs holding intrinsic nonlinearity, high dimensionality, and memory effects have attracted considerable interest regarding solving complex tasks efficiently. Particularly, spintronic and strain-mediated electronic physical reservoirs are appealing due to their high speed, multi-parameter fusion and low power consumption. Here, we experimentally realize a skyrmion-enhanced strain-mediated physical reservoir in a multiferroic heterostructure of Pt/Co/Gd multilayers on (001)-oriented 0.7PbMg1/3Nb2/3O3−0.3PbTiO3 (PMN-PT). The enhancement is coming from the fusion of magnetic skyrmions and electro resistivity tuned by strain simultaneously. The functionality of the strain-mediated RC system is successfully achieved via a sequential waveform classification task with the recognition rate of 99.3% for the last waveform, and a Mackey-Glass time series prediction task with normalized root mean square error (NRMSE) of 0.2 for a 20-step prediction. Our work lays the foundations for low-power neuromorphic computing systems with magneto-electro-ferroelastic tunability, representing a further step towards developing future strain-mediated spintronic applications.

Enhanced antibiotic degradation performance of Cd0.5Zn0.5S/Bi2MoO6 S-scheme photocatalyst by carbon dot modification

S-scheme heterojunction engineering is an effective strategy to attain distinctive photocatalysts. Herein, a carbon dots modulated S-scheme hetero-structured photocatalyst of Cd0.5Zn0.5S nanoparticles/Bi2MoO6 microspheres/carbon dots (CZCBM), aiming to conquer the photo-corrosion and strengthen the photocatalytic property of Cd0.5Zn0.5S, was developed via a facile solvothermal route. Under visible light, the optimal CZCBM-2 affords a 1.8-, 1.5-, or 0.6-time reinforcement in the oxytetracycline degradation rate constant compared to Bi2MoO6, Cd0.5Zn0.5S or Cd0.5Zn0.5S/Bi2MoO6, which is credited to the strengthened visible-light response, increased reactive sites, and efficient dissolution of photo-carriers with optimal redox capacity because of the co-effect of carbon dots and S-scheme heterostructure. Significantly, the photo-corrosion of Cd0.5Zn0.5S is significantly suppressed and CZCBM-2 affords superior stability and reusability during cycling tests. Besides, CZCBM-2 can be well adapted to various environments. The toxicology appraisement unravels the decreased eco-toxicity of most intermediates compared to oxytetracycline. Lastly, an S-scheme charge transfer mechanism with carbon dots as electron reservoir in CZCBM is deduced, which uncloses that •O2− and h+ dominantly account for oxytetracycline eradication and detoxification. This study demonstrates the design of unique carbon dots favored S-scheme heterostructures as an effective “Two Birds with One Stone” strategy to achieve high anti-photo-corrosion performance and reinforced photocatalytic performance of sulfides.

Precise Defect Engineering on Graphitic Carbon Nitrides for Boosted Solar H2 Production.

Defect engineering has been regarded as an "all-in-one strategy" to alleviate the insufficient solar utilization in g-C3N4. However, without appropriate modification, the defect benefits will be partly offset due to the formation of deep localized defect states and deteriorated surface states, lowering the photocarrier separation efficiency. To this end, the defective g-C3N4 is designed with both S dopants and N vacancies via a dual-solvent-assisted synthetic approach. The precise defect control isrealized by the addition of ethylene glycol (EG) into precursor formation and molten sulfur into the pyrolysis process, which simultaneously induced g-C3N4. with shallow defect states. These shallow defect energy levels canact as a temporary electron reservoir, which are critical to evoke the migrated electrons from CB with a moderate trapping ability, thus suppressing the bulky photocarrier recombination. Additionally, the optimized surface states of DCN-ES arealso demonstrated by the highest electron-trapping resistance (Rtrapping) of 9.56×103 Ω cm2 and the slowest decay kinetics of surface carriers (0.057s-1), which guaranteed the smooth surface charge transfer rather than being the recombination sites. As a result, DCN-ES exhibited a superior H2 evolution rate of 4219.9µmol g-1 h-1, which is 29.1-fold higher than unmodified g-C3N4.

Crystalline F-doped titanium dioxide nanoparticles decorated with graphene quantum dots for improving the photodegradation of water pollutants

Carbon dots are emerging photoactive materials with high chemical stability, aqueous solubility, abundant surface functional groups and low-cost production. Their great advantages, incorporated into the high photocatalytic activity of the TiO2, result in hybrid systems that overcome some of the photocatalytic drawbacks associated with TiO2. In this work, a facile synthesis of hybrids of F-doped TiO2 and N-doped graphene quantum dots (F-TiO2@N-GQDs) is reported. These systems have demonstrated efficient photocatalytic properties in light-driven pollutant reduction from water. Therefore, using a simple and low-cost synthesis method, the N-GQDs act as electron reservoirs improving the pairs e--h+ lifetime in TiO2 by decreasing charge recombination, increasing their photocatalytic capacity. The photocatalysts showed very effective degradations of different contaminants such as methylene blue (90% degradation) ciprofloxacin (62% degradation) and naproxen (60% degradation) in short periods of up to 15 min and 4-chlorophenol (59% degradation) in 30 min using UV light (300 W).

Chiral phonon induced spin polarization

The current understanding of chirality suggests the existence of a connection between structure and angular momentum, including spin. This is particularly emphasized in the chiral induced spin selectivity effect, where chiral structures act as spin filters. However, the recent discovery of chiral phonons have demonstrated that phonons too may carry angular momentum which also can be regarded as magnetic moments adding to the total moment. Here, it is shown that chiral phonons may induce a nontrivial spin texture in an otherwise nonmagnetic electronic structure. By considering a setup in which electrons and phonons are interfaced with each other, it is shown that chiral phonons may transfer their angular momentum into the electron reservoir which, thereby, becomes spin polarized. It is, moreover, shown that an equivalent mechanism does not exist whenever the electrons are interfaced with achiral phonons.Received 23 October 2022Revised 22 March 2023Accepted 26 April 2023DOI:https://doi.org/10.1103/PhysRevResearch.5.L022039Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasMagnetismPhononsSpin Seebeck effectSpin polarizationSpin-orbit couplingSpin-phonon couplingCondensed Matter, Materials & Applied Physics

Noise-to-energy conversion in a nanometer-scale dot observed with electron counting statistics

We converted Gaussian-distributed voltage noise applied to an electron reservoir into the non-equilibrium free energy of a nanometer-scale dot connected to the reservoir via an energy barrier. Counting statistics of single-electron motion into and out of the dot through the energy barrier allows us to quantitatively analyze the energy transported into the dot as well as changes in the internal energy and effective temperature of the dot in this noise-induced non-equilibrium steady state (NESS). By analyzing the transition rates of electrons moving into and out of the dot, we confirmed that the rectification effect caused by the asymmetry with respect to the direction of electron motion is the origin of the increase in the internal energy of the dot. The information on energy transport in a nanometer-scale dot in the noise-induced NESS obtained in this study with electron counting statistics clarifies the relationship between the non-equilibrium dynamics of a nanodevice and noise applied to it. This study provides us with the means to evaluate device operation using noise as a resource.

Self-supported nickel‐cobalt layered double hydroxide for efficient primary amine electrooxidation and decoupled water electrolysis

The hybrid water electrolysis affords a green route for the generation of fine chemicals accompanied with hydrogen production relying on the rapid development of anodic electrocatalysts. Herein, a nickel‐cobalt layered double hydroxide (NiCo LDH) modified nickel foam, prepared at room temperature via simple soaking processes, could effectively catalyze the dehydrogenation oxidation of primary amines to generate aromatic and aliphatic nitriles with good yields. Further expanding the application of the easily available electrode, the NiCo LDH electrode could function as the electron reservoir to realize the decoupled water electrolysis with 100% coulombic efficiency in the membrane-free electrolytic cell.

Hydrogen Peroxide Production with High Solar to Chemical Conversion (0.16%) and Efficient Water Purification Using Carbon Quantum Dots-Modified Indium Sulfide

Photocatalytic production of hydrogen peroxide (H2O2) is the need of the hour for green synthesis and sustainability. Herein, we designed hierarchical carbon quantum dots (CQDs)-supported β-indium sulfide (β-In2S3) nanoflakes as an efficient catalyst for H2O2 generation via a two-electron oxygen reduction reaction. The composite material exhibited a high H2O2 production rate of 634 μM h–1, a solar-to-chemical conversion (SCC) efficiency of 0.16%, a high forward rate constant of ∼19 μM min–1, and a low H2O2 dissociation constant of ∼0.004 min–1, all of which are significantly higher than those of pure β-In2S3. Moreover, this material also manifested good water remediation photocatalytic performance by way of removal of 93% chromium(VI), 58% nickel(II), and 94% rhodamine B in 2 h. The apparent rate constant for chromium(VI) reduction of the composite was 0.023 min–1, which is 10-fold higher than that of the pure material. β-In2S3-CQDs exhibited superior results, which can be attributed to their large electrochemical surface area, good light harnessing ability, upconverted photoluminescence, and the ability to act as an electron reservoir preventing recombination.

Charged magnons on the surface of a topological insulator

We study a system of two-dimensional Dirac electrons (as is realized on the surface of a 3D topological insulator) coupled to an array of localized spins. The spins are coupled ferromagnetically to each other, forming an ordered ground state with low-energy spin-wave excitations (magnons). The Dirac electrons couple to the spins through a spin-dependent effective Zeeman field. The out-of-plane effective Zeeman field therefore serves as a Dirac mass that gaps the electronic spectrum. Once a spin is flipped, it creates a surrounding domain in which the sign of the Dirac mass is opposite to that of the rest of the sample. Therefore, an electronic bound state appears on the domain wall, as predicted by Jackiw and Rebbi. However, in a quantum magnet, a localized spin flip does not produce an eigenstate. Instead, the eigenstates correspond to delocalized spin waves (magnons). As in the case of the single flipped spin, the delocalized magnon also binds an in-gap electronic state. We name this excitation a `Jackiw-Rebbi-Magnon' (JRM) and study its signature in the dynamic spin susceptibility. When the sample is tunnel-coupled to an electronic reservoir, a magnon produced in a system without any electrons hybridizes with a JRM (which binds a single electron), producing magnon-JRM polaritons. For such a system, we identify a quantum phase transition when the magnon-JRM polariton energy falls below that of the fully polarized ferromagnetic ground state.

Two-dimensional interface engineering of g-C3N4/g-C3N4 nanohybrid: Synergy between isotype and p-n heterojunctions for highly efficient photocatalytic CO2 reduction

The creation of an isotype phase junction has been recognized as an effective means of improving the spatial charge separation and migration in g-C3N4 materials. Nevertheless, due to a lack of electrostatic control in the internal electric field, isotype heterojunction alone is incapable of providing a sufficient driving force to maximize charge carrier transfer. Herein, we present an interface engineering strategy for co-integrating isotype and p-n heterojunctions to fabricate g-C3N4/g-C3N4 nanohybrids using a facile ultrasonic-assisted self-assembly method. The coherent boundary between the two distinct phases of g-C3N4 demonstrates that an intimate 2D interfacial contact can be easily established by π-π stacking interactions because of their high structural similarities and low lattice strain. Furthermore, their compatible and well-matched electronic band structures led to a staggered type II alignment in the lateral heterojunction, which confers the resulting composite with strong redox ability, efficient exciton dissociation, and desirable optoelectronic characteristics beyond those of the two constituents. Essentially, the isotype and p-n heterojunctions work in tandem to create a robust built-in electric field, allowing for effective interfacial charge steering for directional electron migration from BCN to CNx. Benefiting from these merits, the BCN/CNx nanohybrid manifested remarkable CH4 generation from photocatalytic CO2 reduction, outperforming its CNx and BCN counterparts by 1.91 and 6.88-fold, respectively. The midgap states induced by nitrogen defects in CNx also pose a positive effect on the improved photoactivity of the binary composite by acting as an electron reservoir to mediate electron transfer and further impede charge carrier recombination. This proof-of-concept study highlights the significance of interface engineering in charge flow manipulation and utilization for photocatalytic enhancement.

Thermoelectric study of the time-dependent resonant level model

We study the non-interacting time-dependent resonant level model mimicking a driven quantum dot connected through leads to two electronic reservoirs held at different temperatures and electrochemical potentials. Using a scattering approach, we provide analytical formulas of the time-dependent particle currents, heat currents, and input driving power under the wideband limit approximation. We also derive Landauer formulas for the corresponding time-integrated quantities when the perturbation applied on the dot is of finite duration. Then, we focus on the case of a single square pulse, benchmark our analytical results against numerical ones that are valid beyond the wideband limit, and perform numerical simulations for a smooth square pulse and a periodic square pulse train. Finally, we discuss whether the efficiency of the device in a stationary Seebeck configuration can be enhanced by driving the dot potential. We find numerically that the transient increase of the efficiency observed in some cases is eventually canceled out at long times.

Fabrication of direct Z-scheme Cu2O@V-CN (octa) heterojunction with exposed (1 1 1) lattice planes and nitrogen-rich vacancies for rapid sterilization

The Z-scheme heterojunction has demonstrated significant potential for promoting photogenerated carrier separation. However, the rational design of all-solid Z-scheme heterojunctions catalysts and the controversies about carrier transfer path of direct Z-scheme heterojunctions catalysts face various challenges. Herein, a novel heterojunction, Cu2O@V-CN (octa), was fabricated using V-CN (carbon nitride with nitrogen-rich vacancies) in-situ electrostatic self-wrapping Cu2O octahedra. Density functional theory (DFT) calculations revealed that the separation of carriers across the Cu2O@V-CN (octa) heterointerface was directly mapped to the Z-scheme mechanism compared to Cu2O/V-CN (sphere). This is because the Cu2O octahedra expose more highly active (111) lattice planes with more terminal Cu atoms and V-CN with abundant nitrogen vacancies to form delocalized electronic structures like electronic reservoirs. This facilitates the wrapping of Cu2O octahedra by V-CN and protects their stability via tighter interfacial contact, thus enhancing the tunneling of carriers for rapid photocatalytic sterilization. These findings provide novel approaches for designing high-efficiency Cu2O-based photocatalytic antifoulants for practical applications.

Conversion of Dinitrogen and Oxygen to Nitric Oxide Mediated by Triatomic Yttrium Cations: Reversible N-N Bond Switching.

The direct coupling of dinitrogen (N2) and oxygen (O2) to produce value-added chemicals such as nitric acid (HNO3) at room temperature is fascinating but quite challenging because of the inertness of N2 molecules. Herein, an interesting reaction pathway is proposed for a direct conversion of N2 and O2 mediated by all-metal Y3+ cations. This reaction pattern begins with the N≡N triple bond cleavage by Y3+ to generate a dinitride cation Y2N2+, and the electrons that lead to N2 activation in this process mainly originate from Y atoms. In the following consecutive reactions with two O2 molecules, the electrons stored in the N atoms are gradually released to reduce O2 through re-formation and re-fracture of the N-N bonds, with concomitant release of two NO molecules. Therefore, the reversible N-N bond switching acts as an efficient electron reservoir to drive the oxidation of the reduced N atoms, leading to the formation of NO molecules. This method of producing NO by direct coupling N2 and O2 molecules, which is the reversible N-N bond switching, may provide a new strategy for the direct synthesis of HNO3, etc.

Integration of TADF Photosensitizer as "Electron Pump" and BSA as "Electron Reservoir" for Boosting Type I Photodynamic Therapy.

Type I photosensitization provides an effective solution to the problem of unsatisfactory photodynamic therapeutic (PDT) effects caused by the tumor hypoxia. The challenge in the development of Type I mode is to boost the photosensitizer's own electron transfer capacity. Herein, we found that the use of bovine serum albumin (BSA) to encapsulate a thermally activated delayed fluorescence (TADF) photosensitizer PS can significantly promote the Type I PDT process to generate a mass of superoxide anions (O2•-). This Type I photosensitization opened a new strategy by employing BSA as "electron reservoir" and TADF photosensitizer as "electron pump". We integrated these roles of BSA and PS in one system by preparing nanophotosensitizer PS@BSA. The Type I PDT performance was demonstrated with tumor cells under hypoxic conditions. Furthermore, PS@BSA took full advantage of the tumor-targeting role of BSA and achieved efficient PDT for tumor-bearing mice in the in vivo experiments. This work provides an effective route to improve the PDT efficiency of hypoxic tumors.