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The nuclear waste problem is one of the main interests of rare earth and actinide element chemistry. Here we present the analysis of frontier orbitals and bonding energy of actinide-organic complexes through four-component relativistic calculations.

Recently, 2D JTMDs with asymmetric electronic structures are inviting an intense research interest in modern science and technology. Using the first principles-based periodic hybrid dispersion-corrected Density Functional Theory (DFT-D) method, we have investigated the equilibrium structure, geometry, and electronic properties of the 2D monolayer MoSSe JTMD with the electrocatalytic activities for the H2 evolution reaction (HER). We have performed non-periodic quantum mechanical DFT computations to find out the most favorable HER pathway on the exposed surfaces of the 2D Janus MoSSe material i.e., on the Mo-edges and S- or Se-edges. To explore the electrocatalytic HER mechanism, reaction pathways and barriers, we have considered a cluster model system Mo10S12Se9 to illustrate the Mo-edges and S- or Se-edges of the 2D monolayer MoSSe material. The present study reveals that the Volmer-Heyrovsky reaction mechanism is thermodynamically favorable reaction pathway to evolute H2 at the Se-terminated Mo-edges. It was found that the change of free energy barrier during the Heyrovsky reaction at the Se-terminated Mo-edges is about 3.93-7.10 kcal.mol-1 (in both the gas and the solvent phases), indicating an exceptional electrocatalyst for HER with the lowest activation barriers. This study showed that the Tafel slope (m) is lower in the case of 2D Janus MoSSe material due to the overlap of the s-orbital of the hydrogen and d-orbitals of the Mo atoms appeared in the HOMO and LUMO transition state TS1 of the H-migration reaction step. The better stabilization of the atomic orbitals in the HER rate-limiting step i.e., H-migration TS1 reaction step (in the solvent phase) is a key for reducing the reaction barrier, thus the overall catalysis indicating a better electrocatalytic performance for H2 evolution.

Hydrogen (H2) is deemed as an attractive energy carrier alternative to fossil fuels, and it is required to be stored for many applications.

TMDs are a new family of 2D materials with features that make them appealing for potential applications in nanomaterials science and engineering. Although, the edges of the 2D TMDs show excellent electrocatalytic performance, their basal plane is inert which hinders the industrial applications for electrocatalysis. Here, we have computationally designed the 2D monolayer MoSe$_2$ and studied its electronic properties with electrocatalytic activities. Pt-atom has been doped in the pristine 2D MoSe$_2$ to activate the inert basal plane resulting zero bandgap. This study reveals that the Pt-MoSe$_2$ is an excellent bifunctional electrocatalyst for both the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) with the aid of the DFT. Periodic hybrid DFT method has been applied to compute the electronic properties of both the pristine MoSe$_2$ and Pt-MoSe$_2$. To determine both the HER and ORR mechanisms on the surface of the Pt-MoSe2 material, a non-periodic DFT calculation has been performed by considering a molecular Pt1-Mo$_9$Se${21}$ cluster model. The present study shows that the 2D Pt-MoSe$_2$ follows Volmer-Heyrovsky mechanism for HER with the energy barriers about 9.29 kcal/mol and 10.55 kcal.mol-1 during the H-migration and Heyrovsky reactions. The ORR is achieved by four-electron transfer mechanism with the formation of two transition energy barriers about 14.94 kcal/mol and 11.10 kcal/mol, respectively. The lower energy barriers and high turnover frequency during the reactions expose that the Pt-MoSe$_2$ can be adopted as an efficient bifunctional electrocatalyst for both the HER and ORR. The present studies demonstrate that the exceptional HER and ORR activity and stability performance shown by the MoSe$_2$ electrocatalyst can be enhanced by Pt-doping, opening a promising concept for the sensible design of high-performance catalyst for H2 production and O2 reduction.

Pyrene-based fluorescent Ru(ii)-arene complexes modulate the cell redox balance to provide a novel chemotherapeutic direction.

Ultrathin Two-Dimensional Janus transition metal dichalcogenides (2D JTMDs) have attracted much attention due to their potential applications in electrocatalysis, sensors, and other electromechanical devices. In the present work, first principles-based...

Hexagonal boron nitride (hBN) has long been considered chemically inert due to its wide bandgap and robust covalent bonds. Its inertness hinders hBN from functionalization for energy conversion applications. A question arising is whether it is possible to make hBN chemically reactive. Here, we report cryomilling in liquid N2, as an effective strategy to activate the chemical reactivity of hBN by engineering different vacancies to produce defective-BN (d-BN). The local reactivity of the vacancies is probed by photoluminescence (PL) emissions and electron spin resonance spectroscopy (ESR). Density functional theory calculations reveal that the formation of different vacancies with/without oxygen cause the creation of mid-gap states that are responsible for the PL emissions in the visible region. These vacancies also generate localized free radicals which are both theoretically and experimentally confirmed by spin density calculations and ESR. Due to the vacancy induced free radicals and Fermi level shifts, d-BN can be controllably functionalized with single metal atoms by the spontaneous reduction of metal cations; mono-metallic or bi-metallic clusters can also be effectively reduced. As a proof of concept, the surface-bound metal nanostructures, especially substrate confined single metal atoms, exhibit improved hydrogen evolution catalytic performance, and can be further used for sensing, and quantum information.

The oxygen reduction reaction (ORR) is an indispensable reaction in electrochemical energy converting systems such as fuel cells. Generally, reaction kinetics of the ORR is slow, and to speed it up, a practical electrocatalyst is needed. Pt-based catalysts are thermodynamically more appropriate, but due to their scarcity and high cost, they cannot be used on a commercial scale in industries. To search for non-noble metal catalysts, we have performed a theoretical study on the CsPbBr

The discovery of graphene has stirred an intensive research interest in two-dimensional (2D) materials, but its lack of an electronic band gap has stimulated the research for novel materials with semiconducting character. The past few years have witnessed an impressive advancement in 2D materials from fundamental studies to the development of next generation of technologies and materials engineering. Among them, 2D transition metal dichalcogenides (TMDs) have been extensively studied in various areas of research since last few decades, and these 2D TMDs are semiconductors of the type MX2, where M is a transition metal atom (such as Mo or W) and X is a chalcogen atom (such as S, Se, or Te), furnish an auspicious alternative. Due to its unique physical and chemical properties, 2D monolayer TMDs exhibit a distinctive combination of atomic-scale thickness, direct band gap, strong spin–orbit coupling, and favorable electronic and mechanical properties. These properties make the 2D TMD materials (such as MoS2, MoSe2, WTe2, WS2, and WSe2) more interesting for fundamental studies and for applications in high-end electronics, spintronics, optoelectronics, electrocatalysis, energy harvesting, flexible electronics, water splitting, DNA sequencing, and personalized medicine. They exhibit tunable electronic band gaps that can undergo a transition from an indirect band gap (bulk crystal structure) to a direct band gap (2D monolayer nanosheets, i.e., slab structure). Because of its robustness, 2D monolayer MoS2 is the most studied material in this family and especially for the applications of electrocatalysis, H2 evolution reactions (HER), etc. Current state-of-the-art catalysts still rely on expensive and rare noble metals; however, the relatively cheap and abundant TMDs have emerged as exceptionally promising alternative electrocatalysts for HER. In this review, we focus on the development of 2D TMDs, their synthesis methods, electronic structures and phases of the TMDs, theoretical modelling of the 2D TMDs, computations of electronic properties, and their potential applications in HER. They have been widely considered potential candidates for HER electrocatalysts because of their low cost, good electrochemical stability in acidic conditions, and its nearly thermoneutral hydrogen adsorption energy. The mechanism of hydrogen adsorption on TMDs plays an important role in optimizing HER activity. This review emphasizes on recent progress in improving the catalytic properties of TMDs toward highly efficient production of H2 by electrochemical HER. Combining theoretical and experimental considerations, a summary of the progress to date is provided, and a pathway forward for viable hydrogen evolution from TMD driven catalysis is concluded.

Ruthenium-based metallotherapeutics is an interesting alternative for platinum complexes acting as anticancer agents after the entry of KP1019, NAMI-A, and TLD1339 in clinical trials. Herein, we have synthesized three new arene ruthenium(II)-tetrazole complexes viz. [Ru2(η6-p-cymene)2(2-pytz)2Cl2] (1), [Ru2(η6-p-cymene)2(3-pytz)Cl3] (2), [Ru2(η6-p-cymene)2(4-pytz)Cl3] (3) [2-pytzH = 2-pyridyl tetrazole; 3-pytzH = 3-pyridyl tetrazole; 4-pytzH = 4-pyridyl tetrazole] which have been characterized by different analytical techniques. To aid the understanding of the complex formation, reactions of the arene ruthenium(II) dimer with tetrazoles were investigated using the first principles-based Density Functional Theory (DFT) B3LYP method. Electronic structures, equilibrium geometries of the reactants and products with the first-order saddle points, reactions mechanism, the changes of enthalpy (∆H) and free energy (∆G), chemical stability, and reaction barriers of the complexes were computed using the B3LYP DFT approach. The in vitro cytotoxicity of these complexes was investigated by MTT assay on different cancer cell lines which reveal complex 2 as the most significant cytotoxic agent toward the HeLa cell line. The complexes have also shown a strong binding affinity towards CT-DNA and albumin proteins (HSA and BSA) as analyzed through spectroscopic techniques. Investigation of the mechanism of cell death by complex 2 was further performed by various staining techniques, flow cytometry, and gene expression analysis by RT-PCR. Inhibition of cell migration study has been also revealed the possibility of complex 2 to act as a prospective anti-metastatic agent.

Orthorhombic crystal structure of the V₃O₇·H₂O material has large interlayer spacing with an open tunnel, making it promising as an intercalation-based cathode for aqueous zinc-ion batteries. However, structural degradation and dissolution cause quick capacity fading for V₃O₇·H₂O. We addressed this issue via a dual modification of the V₃O₇·H₂O material by pre-intercalation with Ag(I) inside the layers (henceforth will be mentioned as AgₓV₃O₇·H₂O) and simultaneous in situ composite formation with reduced graphene oxide (rGO). Computationally, we showed that Ag(I) pre-intercalation in V₃O₇ facilitates the Zn²⁺ intercalation process by thermodynamically stabilizing the material with an intercalation energy of −34.3 eV. The AgₓV₃O₇·H₂O cathode showed ∼1.44-fold improved capacity (270 mA h g–¹) with much improved rate capability, over the pristine V₃O₇·H₂O. The specific capacity and cycle stability was further significantly improved in the graphene constructed conductive flexible architecture with hydrothermally assisted self-assembled packing of several intertwined AgₓV₃O₇·H₂O microbelt mats with rGO core (AgₓV₃O₇·H₂O@rGO). The AgₓV₃O₇·H₂O@rGO cathode enabled a reversible Zn²⁺ insertion/de-insertion process during charge/discharge (as observed in ex situ XRD study) and a significantly decreased (>27 times) charge transfer resistance over pristine V₃O₇·H₂O to promote high specific capacity of 437 and 170 mA h g–¹ at both low (100 mA g–¹) and high (2000 mA g–¹) current, respectively. The morphological analysis of the AgₓV₃O₇·H₂O@rGO before and after 1000 cycles reveals that, although the structural breakdown of the AgₓV₃O₇·H₂O is inevitable during repetitive cycling, the rGO support provides strong interaction with the AgₓV₃O₇·H₂O mat and buffers the structural strain, prevents the agglomeration of the active material, and slows down the structural dissolution at the interface. The synergistic interaction enabled ∼2.3-fold improved cycle stability over the pristine V₃O₇·H₂O with only 0.028% capacity loss per cycle over 1000 cycles.

Research on carbon-based covalent organic frameworks (COFs) is a fascinating area in the field of material science due to their excellent performance and broad range of applications in technology. ...

The O2 reduction reaction (ORR) is a promising reaction in clean energy conversion systems such as fuel cells, metal–air batteries, and electrochemical reactions. Pt shows excellent electrocatalytic activities for ORR, but their high cost and poor durability hinder their wide application in electrochemistry for energy conversion. In this work, we have computationally designed a 2D monolayer Pt-doped MoSe2 (noted by Pt–MoSe2) material, and studied the structural and electronic properties with the ORR activities within the framework of first principles-based periodic hybrid Density Functional Theory (DFT). After doping the Pt atom in the pristine 2D monolayer MoSe2 material, it became metallic with zero band gap and considerable electronic states at the Fermi energy (EF) level, which were confirmed by performing the band structure and total density of states (DOS) calculations. A detailed reaction mechanism based on thermodynamic analysis of ORR on the surfaces of the 2D monolayer Pt–MoSe2 material was carried out by performing quantum mechanical DFT calculations. We explored the electrocatalytic performance of the 2D monolayer Pt–MoSe2 towards ORR, and full ORR pathways and reaction mechanism by computing the relative Gibb's free energy (ΔG) at the same DFT method. The present study shows how to design better electrocatalysts for ORR by understanding the chemical basis for Pt-doping in MoSe2 and modification of the 2D layer structure, which paves the way to create high-performance and easily-accessible electrocatalysts. This work indicates that the 2D monolayer Pt–MoSe2 is a promising candidate to substitute Pt electrodes, and an excellent electrocatalyst for fuel cell components in future applications.

With the enormous progress in ruthenium complexes as promising anticancer agents after the entry of KP1019, KP1339, and NAMI-A in clinical trials, herein three arene ruthenium(II) NSAID (nonsteroidal anti-inflammatory drugs) complexes

This article reports the first instance of exploring a chemically Zn(II) preinserted organic–inorganic hybrid material [vanadyl ethylene glycolate or VEG, (VO(CH2O)2)] as an efficient cathode for r...

The storage of hydrogen (H2) is of economic and ecological relevance, because it could potentially replace petroleum-based fuels. However, H2 storage at mild condition remains one of the bottleneck...

Ruthenium complexes are being studied extensively as anticancer drugs following the inclusion of NAMI-A and KP1019 in phase II clinical trials for the treatment of metastatic phase and primary tumors. Herein, we designed and synthesized four organometallic Ru(II)-arene complexes [Ru(η

Two-dimensional (2D) monolayer pristine MoS

Two-dimensional (2D) monolayer pristine MoS$_2$ transition metal dichalcogenide (TMD) is the most studied material because of its promising aspects as nonprecious electrocatalyst for hydrogen evolution reaction (HER). Previous studies have shown that the basal planes of the 2D MoS$_2$ are catalytically inert and hence, they cannot be used directly in desired applications such as electrochemical HER in industries. Here, we have thoroughly studied the defect-engineered Mn-doped 2D monolayer MoS$_2$ (Mn-MoS$_2$) material where Mn was doped in the pristine MoS$_2$ to activate the inert basal planes. Using density functional theory (DFT) method, we performed rigorous inspection of electronic structures and properties of the 2D monolayer Mn-MoS$_2$ to be a promising alternative to noble metal free catalysts for the effective HER. Periodic 2D slab of the monolayer Mn-MoS$_2$ was created to study the electronic properties and the reaction pathways occurring on the surface of the material. The detailed HER mechanism has been explored by creating the Mn$_1$Mo$_9$S$_{21}$ non-periodic finite molecular cluster model system using M06-L DFT method including solvation effects to determine the reaction barriers and kinetics. Our study reveals that the 2D Mn-MoS$_2$ follows the most favorable Volmer-Heyrovsky reaction mechanism with very low energy barriers during the H$_2$ evolution. It was found that the change of free energy barrier during the Heyrovsky reaction is about 10.34 - 10.79 kcal/mol, indicating an exceptional electrocatalyst for HER. The Tafel slope is lower in the case of 2D monolayer Mn-MoS$_2$ material due to the overlap of the s-orbital of the hydrogen and d-orbitals of the Mn atoms appeared in the HOMO and LUMO transition states (TS1 and TS2) of both the Volmer and Heyrovsky reaction steps., 36 Pages, 10 Figures. arXiv admin note: substantial text overlap with arXiv:2106.14682

An isostructural family of f-element compounds (Ce, Nd, Sm, Gd; Am, Bk, Cf) of the redox-active dioxophenoxazine ligand (DOPOq; DOPO = 2,4,6,8-tetra-tert-butyl-1-oxo-1H-phenoxazin-9-olate) was prepared. This family, of the form M(DOPOq)3, represents the first nonaqueous isostructural series, including the later actinides berkelium and californium. The lanthanide derivatives were fully characterized using 1H NMR spectroscopy and SQUID magnetometry, while all species were structurally characterized by X-ray crystallography and electronic absorption spectroscopy. In order to probe the electronic structure of this new family, CASSCF calculations were performed and revealed these systems to be largely ionic in contrast to previous studies, where berkelium and californium typically have a small degree of covalent character. To validate the zeroth order regular approximation (ZORA) method, the same CASSCF analysis using experimental structures versus UDFT-ZORA optimized structures does not exhibit sizable change...

Covalent-organic frameworks (COFs) have emerged as an important class of nano-porous crystalline materials with many potential applications. They are intriguing platforms for the design of porous skeletons with special functionality at the molecular level. However, despite their extraordinary structural tunability, it is difficult to control their electronic properties, thus hindering the potential implementation in electronic devices. A new family of nanoporous materials, COFs intercalated with first row transition metals, is proposed to address this fundamental drawback - the lack of electronic tunability. Using first-principles calculations, we designed 31 new COF materials in silico by intercalating all of the first row transition metals (TMs) with boroxine-linked and triazine-linked COFs: COF-TM-x (where TM = Sc-Zn and x = 3-5). We investigated their structure and electronic properties. Specifically, we predict that the band gap and density of states (DOS) of COFs can be controlled by intercalating first row transition metal atoms (TM: Sc-Zn) and fine tuned by the concentration of TMs. We also found that the d-subshell electron density of the TMs plays a main role in determining the electronic properties of the COFs. Thus intercalated-COFs provide a new strategy to control the electronic properties of materials within a porous network. This work opens up new avenues for the design of TM-intercalated materials with promising future applications in nanoporous electronic devices, where a high surface area coupled with fine-tuned electronic properties is desired.

Black phosphorus (b-P) is an allotrope of phosphorus whose properties have attracted great attention. In contrast to other 2D compounds, or pristine b-P, the properties of b-P alloys have yet to be explored. In this report, we present a detailed study on the Raman spectra and on the temperature dependence of the electrical transport properties of As-doped black phosphorus (b-AsP) for an As fraction x = 0.25. The observed complex Raman spectra were interpreted with the support of Density Functional Theory (DFT) calculations since each original mode splits in three due to P-P, P-As, and As-As bonds. Field-effect transistors (FET) fabricated from few-layered b-AsP exfoliated onto Si/SiO2 substrates exhibit hole-doped like conduction with a room temperature ON/OFF current ratio of ∼103 and an intrinsic field-effect mobility approaching ∼300 cm2 V-1 s-1 at 300 K which increases up to 600 cm2 V-1 s-1 at 100 K when measured via a 4-terminal method. Remarkably, these values are comparable to, or higher, than those initially reported for pristine b-P, indicating that this level of As doping is not detrimental to its transport properties. The ON to OFF current ratio is observed to increase up to 105 at 4 K. At high gate voltages b-AsP displays metallic behavior with the resistivity decreasing with decreasing temperature and saturating below T ∼100 K, indicating a gate-induced insulator to metal transition. Similarly to pristine b-P, its transport properties reveal a high anisotropy between armchair (AC) and zig-zag (ZZ) directions. Electronic band structure computed through periodic dispersion-corrected hybrid Density Functional Theory (DFT) indicate close proximity between the Fermi level and the top of the valence band(s) thus explaining its hole doped character. Our study shows that b-AsP has potential for optoelectronics applications that benefit from its anisotropic character and the ability to tune its band gap as a function of the number of layers and As content.

In the co-crystals of diphenyl dichalcogenides Ph2E2 (E = Se, Te), the E–E and E–π(Ph) chalcogen bonds assemble Ph2E2 molecules into the chains, which imitate the typical packing patterns of the parent Ph2E2 crystals. These co-crystals consist of quite stable tectonic 1D and 2D Ph2E2 chain architectures, which are repeated in the crystals of pure Ph2E2 as well as in their co-crystals with the halogen bond donor molecules. These chains can be clearly visualized as separate parallel 1D and 2D structures in the energy framework diagrams in CrystalExplorer. From this point of view, the supramolecular reaction of Ph2E2 with the halogen bond donor 1,4-diiodotetrafluorobenzene (p-DITFB) can be considered as the insertion of p-DITFB molecules between the Ph2E2 chains in such a way that I–E and I–π(Ph) halogen bonds come in place of E–E and Te–π(Ph) chalcogen bonds, which are responsible for the close packing of these chains in the parent crystal form. Persistent packing patterns found in parent and binary crystals can provide insight into the mechanism of the crystallization process.

Solid-state thermoelastic behavior-a sudden exertion of an expansive or contractive physical force following a temperature change and phase transition in a solid-state compound-is rare in organic crystals, few are reversible systems, and most of these are limited to a dozen or so cycles before the crystal degrades or they reverse slowly over the course of many minutes or even hours. Comparable to thermosalience, wherein crystal phase changes induce energetic jumping, thermomorphism produces physical work via consistent and near-instantaneous predictable directional force. In this work, we show a fully reversible thermomorphic actuator that is stable at room temperature for multiple years and is capable of actuation for more than 200 cycles at near-ambient temperature. Specifically, the crystals shrink to 90% of their original length instantaneously upon heating beyond 45 °C and expand back to their original length upon cooling below 35 °C. Furthermore, the phase transition occurs instantaneously, with little obvious hysteresis, allowing us to create real-time actuating thermal fuses that cycle between on and off rapidly.

Solid state thermosalience—a sudden exertion of an expansive or contractive physical force following a temperature change in a solid state compound—is rare, few are reversible systems, and most of these are limited to a dozen or so cycles before the crystal degrades or they reverse slowly over the course of many minutes or even hours. In this work, we show a fully reversible actuator that is stable at room temperature for multiple years and is capable of actuation for more than two hundred cycles at near ambient temperature. Specifically, the crystals shrink to 90% of its original length instantaneously upon heating beyond 45 °C and expands back to its original length upon cooling below 35 °C. This temperature regime is important because it occurs around physiologically important temperatures. Furthermore, the phase transition occurs instantaneously, with little obvious hysteresis, allowing us to create real-time actuating thermal fuses that cycle between on and off rapidly.

Solid state thermosalience—a sudden exertion of an expansive or contractive physical force following a temperature change in a solid state compound—is rare, few are reversible systems, and most of these are limited to a dozen or so cycles before the crystal degrades or they reverse slowly over the course of many minutes or even hours. In this work, we show a fully reversible actuator that is stable at room temperature for multiple years and is capable of actuation for more than two hundred cycles at near ambient temperature. Specifically, the crystals shrink to 90% of its original length instantaneously upon heating beyond 45 °C and expands back to its original length upon cooling below 35 °C. This temperature regime is important because it occurs around physiologically important temperatures. Furthermore, the phase transition occurs instantaneously, with little obvious hysteresis, allowing us to create real-time actuating thermal fuses that cycle between on and off rapidly.

In this study, we report a nonprecious metal catalyst for high-efficiency hydrogen evolution reaction (HER). A self-organized S-doped MoP nanoporous layer (S-MoP NPL) is achieved through a facile e...

Advancing beyond Li-ion batteries requires translating the beneficial characteristics of Li+ electrodes to attractive, yet incipient, candidates such as those based on K+ intercalation. Here, we use ultrathin few-layer graphene (FLG) electrodes as a model interface to show a dramatic enhancement of K+ intercalation performance through a simple conditioning of the solid-electrolyte interphase (SEI) in a Li+ containing electrolyte. Unlike the substantial plating occurring in K+ containing electrolytes, we found that a Li+ based SEI enabled efficient K+ intercalation with discrete staging-type phase transitions observed via cyclic voltammetry at scan rates up to 100 mVs–1 and confirmed as ion-intercalation processes through in situ Raman spectroscopy. The resulting interface yielded fast charge–discharge rates up to ∼360C (1C is fully discharge in 1 h) and remarkable long-term cycling stability at 10C for 1000 cycles. This SEI promoted the transport of K+ as verified via mass spectrometric depth profiling. T...

This work reports a highly sensitive and selective nonenzymatic detection of glucose that has been achieved by hybridization of 1D α-MnO2 nanorods modified with surface decoration of Co3O4 nanopart...

A combined theoretical and experimental investigation into the structure and mechanism of the classical Vandenberg catalyst for the isoselective polymerization of epoxides has led to a consistent mechanistic proposal. The most likely reaction pathway was based on a bis(μ-oxo)di(aluminum) (BOD) resting state that proceeded through a mono(μ-oxo)di(aluminum) (MOD) transition state. The isoselectivity of the Vandenberg catalyst was derived from the rigidity of the BOD structure and its bonding to the ultimate and penultimate oxygen heteroatoms along the polyether backbone. The energetic driving force for isoselectivity was the loss of an energetically favorable secondary Al–O interaction during enchainment of oppositely configured epoxides, providing a ca. 2 kcal/mol driving force for the emergent isoselectivity. Experimental spectroscopic and kinetic evidence based on model BOD and MOD complexes support the new mechanistic framework developed using density functional theory calculations. A purposefully synth...

The electronic properties and extreme thinness of graphene make it an attractive platform for exploring electrochemical interactions across dissimilar environments. Here, we report on the systematic tuning of the electrocatalytic activity toward the oxygen reduction reaction (ORR) via heterostructures formed by graphene modified with a metal underlayer and an adlayer consisting of a molecular catalyst. Systematic voltammetric testing and electrochemical imaging of patterned electrodes allowed us to confidently probe modifications on the ORR mechanisms and overpotential. We found that the surface configuration largely determined the ORR mechanism, with adlayers of porphyrin molecular catalysts displaying a higher activity for the 2e– pathway than the bare basal plane of graphene. Surprisingly, however, the underlayer material contributed substantially to lower the activation potential for the ORR in the order Pt > Au > SiOx, strongly suggesting the involvement of the solution-excluded metal on the reaction...

Modern nanoscience has focused on two-dimensional (2D) layer structure materials which have garnered tremendous attention due to their unique physical, chemical, and electronic properties since the discovery of graphene in 2004. A recent advancement in graphene nanotechnology opens a new avenue of creating 2D bilayer graphene (BLG) intercalates. Using first-principles dispersion-corrected DFT techniques, we have designed 20 new materials in silico by intercalating first-row transition metals (TMs) with BLG, i.e., 10-layered structure and 10 bulk crystal structures of TM intercalated in BLG. More specifically, we investigated the equilibrium structure and electronic properties of layered and bulk structure BLG intercalated with first-row TMs (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn). The present DFT-D calculations show that the 2pz subshells of C atoms in graphene and the 3dyz subshells of the TM atoms provide the electron density near the Fermi energy level, controlling the material properties of the BL...

The comprehension of the controlling factors for the self-assembly and corresponding nanostructure formations are very necessary to elucidate the structure-property relation in semiconducting organic molecules. Herein, we are reporting the successful tuning of the self-assembly property and emission behavior of anionic perylene diimide molecule, disodium salt of N,N′-bis(4-benzosulfonic acid)perylene-3,4,9,10-tetracarboxylbisimide (PSA) using a simple solvent-induced technique. The emission enhancement of anionic PSA is revealed with the addition of miscible polar solvents like ethanol, tetrahydrofuran, or dimethyl sulfoxide with water. The lowering of aggregation in the mixed solvent is demonstrated using UV–Vis and photoluminescence studies. The solvent tuneable different assembled structures in water and the mixed solvent were further confirmed by nuclear magnetic resonance (NMR), X-ray diffraction (XRD), dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM), confocal microscopy, and time-correlated single-photon counting (TCSPC) techniques. Alongside the spectroscopic changes, FESEM reveals the change of assembly morphology from highly ordered micro-rod structure in water to homogeneous nanosphere. Furthermore, experimental results of solvent-induced tuneable self-assembly are validated by computational simulation study which elucidates the feasible dimer formation in water and that is not thermodynamically favorable with increasing the ethanol percentage in water. The micro-rods show superior semiconducting characteristics to the nanosphere as investigated by the I–V characteristic due to the extended percolating pathway.

Covalent–organic frameworks (COFs) are intriguing platforms for designing functional molecular materials. Here, we present a computational study based on van der Waals dispersion-corrected hybrid density functional theory (UB3LYP-D2, i.e., DFT-D) to design boroxine-linked and triazine-linked COFs intercalated with Fe. Keeping the original P–6m2 symmetry of the pristine COF (COF-Fe-0), we have computationally designed seven new COFs by intercalating Fe atoms between two organic layers. The equilibrium structures and electronic properties of both the pristine and Fe-intercalated COF materials are investigated here. We predict that the electronic properties of COFs can be fine-tuned by adding Fe atoms between two organic layers in their structures. Our calculations show that these new intercalated-COFs are promising semiconductors. The effect of Fe atoms on the electronic band structures and density of states (DOSs) has also been investigated using the aforementioned DFT-D method. The contribution of the d-s...

Large-area (∼cm2) films of vertical heterostructures formed by alternating graphene and transition-metal dichalcogenide (TMD) alloys are obtained by wet chemical routes followed by a thermal treatment at low temperature. In particular, we synthesized stacked graphene and WxMo1–xS2 alloy phases that were used as hydrogen evolution catalysts. We observed a Tafel slope of 38.7 mV dec–1 and 96 mV onset potential (at current density of 10 mA cm–2) when the heterostructure alloy was annealed at 300 °C. These results indicate that heterostructures formed by graphene and W0.4Mo0.6S2 alloys are far more efficient than WS2 and MoS2 by at least a factor of 2, and they are superior compared to other reported TMD systems. This strategy offers a cheap and low temperature synthesis alternative able to replace Pt in the hydrogen evolution reaction (HER). Furthermore, the catalytic activity of the alloy is stable over time, i.e., the catalytic activity does not experience a significant change even after 1000 cycles. Using...

Organic bridging linkers or ligands play an important role in gas and fuel storage, CO2 capture, and controlling the radical polymerization reactions in metal–organic frameworks (MOFs) nanochannels. The rotation of the linkers causes the expansion of the pore size and pore volume in MOFs. To understand the rotational behavior of organic linkers in MOFs and the substituent effects of the linkers, we investigated the equilibrium structure, stability, potential energy curves (PECs), and rotational energy barriers of the organic bridging linkers of a series of MOF model systems imposing three constrained imaginary planes. Both the dispersion-uncorrected and dispersion-corrected density functional theory (DFT and DFT-D i.e. B3LYP and B3LYP-D3) methods with the correlation consistent double-ζ quality basis sets have been applied to study the model MOF systems [Cu4(X)(Y)6(NH3)4] (where X = organic bridging linker, and Y = HCO2). The present study found that the structural parameters and rotational energy barrier of the model MOF containing 1,4-benzendicarboxylate (BDC) linker are in accord with previous experiments. This study reveals that rotational barriers significantly differ depending on the substituents of organic linkers, and the linker dynamical rotation provides information about the framework flexibility with various potential applications in porous materials science. Changing the linkers in the MOFs could be helpful for designing various new kinds of flexible MOFs which will have many important applications in gas storage and separation, catalysis, polymerization, sensing, etc.