Density Functional Theoretical Calculations Research Articles

Fluorescence detection of hydrazine in an aqueous environment by a corrole derivative.

Broadly, the industrial applications of hydrazine cause environmental pollution and damage to living organisms because of the high toxicity of hydrazine. Therefore, monitoring hydrazine in the environmental system is of great significance to human health. Here, a new fluorescent probe PC-N2 H4 based on corrole dye was developed for the detection of hydrazine that had excellent specificity, low limit of detection (LOD: 88 nM), and a wide pH range (6-12). Upon addition of hydrazine into the probe solution, the strong red fluorescence was 'turned on' centred at 653 nm with a 127-fold fluorescence intensity enhancement. The detection mechanism was proved using ESI-MS, 1 H NMR, and density functional theoretical calculations. Importantly, the probe was utilized to fabricate a ready-to-use test strip to realize the visual inspection of hydrazine. Furthermore, PC-N2 H4 was successfully applied for practical detection of hydrazine in water samples with satisfactory recoveries ranging from 96.2% to 105.0%, and indicating that the designed PC-N2 H4 is highly promising for hydrazine detection in an aqueous environment. Considering the diverse toxicological functions of hydrazine, PC-N2 H4 was also successfully used to image exogenous hydrazine in HeLa cells and zebrafish.

Strong and Ultratough Ionogel Enabled by Ingenious Combined Ionic Liquids Induced Microphase Separation

AbstractIonogels have become a popular material in flexible electronics and soft robotics based on their excellent ionic conductivity, environmental tolerance, and electrochemical stability. However, it remains a challenge to develop an ionogel integrated with high strength, toughness, self‐healing, and adhesion. Herein, a novel strategy is established to design a high‐strength (0.97 MPa) and tensile (980%), excellent crack insensitivity, self‐healing ionogel based on the cosolvent method. By virtue of differential interactions between the specific polymer and various ionic liquids with gradient polarity, cosolvent systems are employed to achieve high‐performance ionogels by a simple one‐step polymerization. Gel permeation chromatography, atomic force microscopy, time‐domain nuclear magnetism, and density functional theoretical calculation are used to analyze the reasons. Microphase separation can be induced by hydrone or stretching to enhance strength of the ionogel. Therefore, ionogels can be assembled as strain and temperature sensors to monitor human movement and person's body temperature with a low detection threshold (0.1 °C) in extreme environments. This concept creates a new path to achieve soft materials with high performance, and provide a prospective strategy to regulate the in situ microphase change and performance of the resulting ionogel via the one‐step polymerization.

Enhancing chemical stability and performance in proton-conducting solid oxide fuel cells through novel composite cathode design

Thermal and chemical compatibility between the cathode and electrolyte is crucial for the development of proton-conducting solid oxide fuel cells (H–SOFCs). To tackle this challenge, composite cathodes are often prepared by mixing traditional cathode materials with BaZr0.1Ce0.7Y0.2O3+δ (BZCY) electrolyte material. However, it should be noted that BZCY has a propensity to react with water generated during cell operation. Thus, this article presents the recent findings on performance enhancement of H–SOFCs through the utilization of a novel composite cathode, consisting of La0.6Sr0.4Co0.2Fe0.8O3+δ (LSCF) and La2-xNixCe2O7-δ (LNCOx) (x = 0.1, 0.2, 0.3, 0.4). The novel composite LSCF-LNCO0.3 cathode has shown significant improvements in the catalytic activity and durability, achieving a maximum power density of 1283 mW cm−2 at 700 °C. Density functional theoretical calculation (DFT) results reveal that the Ni doping in La2Ce2O7+δ (LCO) can effectively reduce the proton migration energy and enhance hydration ability, thereby obtaining high cathode performance. Compared traditional cathode design strategy, a novel design strategy involving the adjustment of the electrolyte component shows great potential for further advancement in cell performance.

Combined Experimental and Theoretical Insights on Selectivity of Rare Earth Elements with Tetra‐2‐ethylhexyl Diglycolamide

AbstractA diglycolamide based extractant namely tetra‐2‐ethylhexyl diglycolamide [TEHDGA] has been synthesized and characterized for extraction of rare earths from coal fly ash (CFA). The formation rare earth‐TEHDGA complex in the organic phase was determined from slope analysis method. The same structure was further corroborated by the density functional theoretical calculation. Furthermore, DFT approach was adopted to explain the relative stability of rare earth complex with TEHDGA over other matrix elements like Fe, Ca, Al, Mg of CFA by determining their free energy of extraction. The calculated selectivity trend from the free energy of extraction is obtained after consideration of 1 : 3 stoichiometry for Europium – the representative of all rare earth elements. Thus the correct selectivity order was established from a combined experimental and density functional theoretical studies.

Calix[4]arene-Derived 2D Covalent Organic Framework with an Electron Donor-Acceptor Structure: A Visible-Light-Driven Photocatalyst.

The calixarenes are ideal building blocks for constructing photocatalytic covalent organic frameworks (COFs), owing to their electron-rich and bowl-shaped π cavities that endow them with electron-donating and adsorption properties. However, the synthesis and structural confirmation of COFs based on calixarenes are still challenging due to their structural flexibility and conformational diversity. In this study, a calix[4]arene-derived 2D COF is synthesized using 5,11,17,23-tetrakis(p-formyl)-25,26,27,28-tetrahydroxycalix[4]arene (CHO-C4A) as the electron donor and 4,7-bis(4-aminophenyl)-2,1,3-benzothiadiazole (BTD) as the acceptor. The powder X-ray diffraction data and theoretical simulation of crystal structure indicate that COF-C4A-BTD exhibits high crystallinity and features a non-interpenetrating undulating 2D layered structure with AA-stacking. The density functional theory theoretical calculation, transient-state photocurrent tests, and electrochemical impedance spectroscopy confirm the intramolecular charge transfer behavior of COF-C4A-BTD with a donor-acceptor structure, leading to its superior visible-light-driven photocatalytic activity. COF-C4A-BTD exhibits a narrow band gap of 1.99eV and a conduction band energy of -0.37V versus normal hydrogen electrode. The appropriate energy band structure can facilitate the participation of ·O2- and h+ . COF-C4A-BTD demonstrates high efficacy in removing organic pollutants, such as bisphenol A, rhodamine B, and methylene blue, with removal rates of 66%, 85%, and 99% respectively.

Dynamic Metastable Characteristics of Carbon Cages Embedded with Er2C2.

Novel endohedral metallofullerenes (EMFs), namely, Er2C2@C2v(5)-C80, Er2C2@Cs(6)-C82, Er2C2@Cs(15)-C84, Er2C2@C2v(9)-C86, Er2C2@Cs(15)-C86, and Er2C2@Cs(32)-C88, had been experimentally synthesized, and the unique structures and many fascinating properties had also been widely explored. Nevertheless, the position of the Er atoms inside the cage shows a severe disorder within the stable EMF monomer, which is difficult to understand and explain from the experimental point of view. In this work, based on the density functional theoretical calculations, the Er2C2@Cs(6)-C82 has 73 directional isomers and 2 Er atoms that are far beyond from Er-Er single bonding and tend to be close to the cage side (marked as "shell"), and the core (Er2C2 units) takes on a butterfly shape as generally revealed. The energy difference between any two of the isomers is in the range of 0.05 to 25.6 kcal/mol, indicating a relatively easy thermodynamic transition between the isomers. The other five Er carbide cluster EMFs (Er2C2@C2v(5)-C80, Er2C2@Cs(15)-C84, Er2C2@C2v(9)-C86, Er2C2@Cs(15)-C86, and Er2C2@Cs(32)-C88) are also studied in the same way, and 30, 37, 39, and 43 most stable Er-oriented sites inside the cage, respectively, are obtained. In addition, the shape of the Er2C2 gradually changed from butterfly to linear. Moreover, the electronic structure and molecular orbital analyses show that it is easy for Er2C2@C80-88 to form a charge transfer state of [Er2C2]4+@[C80-88]4- via the dynamic core-shell coordination equilibrium. Er2C2 with a steep drop in chemical stability is restricted to forming varying degrees of metastable states in the shell, determined by the shell size, to ensure the overall stability. The lowest unoccupied molecular orbital energy level of these EMFs is increased by 0.5-1.1 eV compared with fullerenes C80-88, potentially providing favorable conditions for suitable energy level matching with EMF as an electron acceptor used in organic solar cell devices.

Two‐Dimensional Amorphous Iridium Oxide for Acidic Oxygen Evolution Reaction

AbstractThe increasing popularity of proton exchange membrane electrolysis technology for hydrogen production has brought attention to the electrolytic water reaction. However, the slow kinetics of the oxygen evolution reaction (OER) at the anode have great influence on the overall efficiency of the reaction. While iridium oxide shows excellent stability under acidic conditions, its OER activity still needs to be improved. Here, we synthesized two‐dimensional amorphous iridium oxide (Am−IrO2) nanosheets with the thickness of only 6 nm by a mixed molten salt method. Such nanosheets show an ultralow overpotential of only 230 mV at 10 mA cm−2 in 0.5 M H2SO4. The overpotential increases only 40 mV after 90 hours of the stability test at this current density. Am−IrO2 can maintain the current density of ~400 mA cm−2 after 120 hours of test at 1.8 V in the PEM device, demonstrating good industrial prospects. Density functional theoretical calculations show that the oxygen vacancies, together with the upshift of the O 2p band center, are responsible for the improvement of OER in Am−IrO2.

A novel hydrangea-like ZnIn2S4/FePO4 S-scheme heterojunction via internal electric field for boosted photocatalytic H2 evolution

Reasonable design of high-performance catalysts with heterojunction to suppress the combination of electron-hole pairs has become an appealing challenge in photocatalytic field. Herein, a novel hydrangea-like ZnIn2S4/FePO4 with S-scheme heterojunction was constructed via an ultrasound-annealing process for photocatalytic H2 evolution. The composites showed remarkable photocatalytic H2 production performance (3.337 mmol h−1 g−1), which was approximately 7.5 times higher than that of blank ZnIn2S4 (0.446 mmol h−1 g−1). The improved photocatalytic H2 evolution was mainly ascribed to the accelerated electron-hole separation through the construction of S-scheme heterojunction in interface. Moreover, the hydrangea-like structure provided abundant active sites and huge specific surface area, which was conducive to the exceptional photocatalytic activity. Simultaneously, both experimental and Density Functional Theoretical calculation results provided strong evidence for the transfer path of photogenerated carriers following the S-scheme heterojunction, and the unique mechanism of photocatalytic H2 production was proposed. In addition, the hydrangea-like ZnIn2S4/FePO4 heterojunction photocatalyst showed a commendable stability with no distinct decrease after three cycle tests, demonstrating its potential as a recoverable photocatalyst. This work offered insights into the design and preparation of highly efficient photocatalysts with S-scheme heterojunction.

Freestanding fibers assembled by CoPSe@N-doped carbon heterostructures as an anode for fast potassium storage in hybrid capacitors

Although the fast development of potassium-ion hybrid capacitors (PIHC) recently, the issues such as the slow kinetics and poor durability of potassium ion hosts greatly restric their applications. Herein, a freestanding fiber (NHF fiber) with necklace-like configuration and CoPSe@N-doped carbon (CoPSe@NCNT) heterostructured units is introduced as the anode in PIHC. The highly porous network of NHF fiber facilitates the fast ion transports and promises the good high-rate property. Additionally, the nanoscle crystallites inside in-situ grown NCNT favor the high adaption to volume expansion/shrinkage and endow good structure stability during ion insertion/deinsertion. Density function theoretical (DFT) calculations disclose the CoPSe@NCNT heterostructure has improved intrinsic conductivity, fast potassium migration, and decreased energy barrier. Meanwhile, the finite element simulation analysis (FEA) reveals the decreased stress inside the NHF architecture during charge/discharge processes. Moreover, the electrochemical tests confirm the fast and durable properties of the CoPSe@NCNT NHF fibers for potassium storage. Furthermore, the PIHC full cell with the anode of CoPSe@NCNT NHF fiber is assembled, which obtains the superior energy/power densities and high capacity retention (89%) after 2000 cycles at 2 A g−1. When the polymer electrolyte is incooperated, the flexible PIHC device achieves the good pliability and good adaptation during wide temperature changes from −20 to 25 °C. Therefore, this work introduces a novel anode for fast potassium ion storage, and opens a new approach to assemble the power sources for flexible electronics in diverse conditions.

Rapid and deep photocatalytic degradation of polyvinyl alcohol by black phosphorus quantum dot sensitized g-C3N4

To address the pollution caused by polyvinyl alcohol (PVA) waste, a composite photocatalyst is developed by sensitizing g-C3N4 with black phosphorus quantum dots (BPQDs) using a simple mechanical stirring method. Both g-C3N4 and BPQDs are inorganic nonmetallic semiconductors with well-matched band positions, facilitating efficient photoinduced charge transfer. The periodic table’s adjacent relationship between C, N and P elements allows easy formation of P-N or P-C bonds by replacing C or N atoms with P atoms. The resulting composite shows uniform decoration of two-dimensional layered g-C3N4 with BPQDs with an average size of 2.2 nm. Under solar light simulator irradiation for 20 min, the composite photocatalyst exhibits significantly enhanced photocatalytic activity, with PVA degradation efficiency increasing from 27.1% (pure g-C3N4) to 85.9%. Experimental results and density functional theoretical calculations suggest the formation of a Z-scheme route at the g-C3N4/BPQDs interface. This facilitates photoinduced electron transfer from g-C3N4 to BPQDs, leading to improved carrier production and separation, reduced charge-transfer resistance, and accelerated PVA degradation. The proposed composite photocatalyst holds promise for addressing PVA pollution and improving environmental sustainability.

Adsorption and anticorrosion studies of newly designed Schiff bases for the protection of EN3B mild steel in 3.5% NaCl solution: A combined experimental and theoretical approach

Three newly synthesized Schiff bases; 5-(diethylamino)-2-[(n-undecylimino)methyl]phenol (NS11), 5-(diethylamino)-2-[(n-tetradecylimino)methyl]phenol (NS14) and 5-(diethylamino)-2-[(n-hexadecylimino)methyl]phenol (NS16) have been presented as efficient corrosion inhibitors for the protection of EN3B mild steel in 3.5% NaCl solution at acidic pH 1.5. The inhibitors were characterized by multitude techniques i.e., Fourier transform-infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry and single crystal X-ray diffraction (XRD) analysis. An anti-corrosive film of the inhibitors was generated on EN3B mild steel surface by dip-coating method and the presence of adsorbed molecules in a monolayer was detected via reflection absorption infrared spectroscopy (RAIRS). Electrochemical measurements revealed a strong inhibition potential of the inhibitors with the maximum inhibition efficiency of 99.8% achieved by NS16. These results were further complemented by morphological examinations and density functional theoretical (DFT) calculations revealing that the electron donating power of substituents is directly related to the inhibition potential of the inhibitors.

Novel through-holes g-C3N4/BiOBr S-scheme heterojunction: Charge relocation mechanism and DFT insights

A novel multiscale through-holes g-C3N4/BiOBr S-scheme heterojunction with homogeneous morphology was fabricated via a solvothermal method. Notably, the prepared through-holes g-C3N4 yielded a subband gap (2.11 eV) attributed to the fracture and reorganization of triazine ring units, leading to a narrow band gap complex. Photocatalyst A-2 (2.73 eV) was significantly broadened at the absorption edge. A reasonable S-scheme heterojunction charge relocation mechanism was demonstrated based on active species trapping experiments, atomic force microscope (AFM) equipped with a Kelvin probe force microscope (KPFM), and density functional theoretical (DFT) theoretical calculations. The S-scheme g-C3N4/BiOBr heterojunction and the constructed internal electric field facilitate the retention of high redox properties and facilitated charge relocation. Hence, the synergistic interaction between the S-scheme heterojunction and through-holes structure enabled specimens to be exhibited high-efficiency degradation activity. The degradation efficiency of photocatalyst A-2 for TC·HCL and RhB was 94.5% (60 min) and 99.9% (30 min), respectively. At pH = 5.1, the TC·HCL photoreaction time was reduced to 30 min, whereas at pH = 2.3, the RhB photoreaction time was shortened to 15 min. Five repeatable recovery tests still maintain excellent stability. This work contributes new insights into the charge relocation mechanism of S-scheme heterojunction high-efficiency photocatalysts.

Electrochemical detection of fluoride ions using 4-aminophenyl boronic acid dimer modified electrode

Fluoride is a widely used component in dental products, offering benefits such as cavity prevention through bacterial growth inhibition. However, excessive fluoride consumption can lead to fluorosis, which causes tooth discoloration and pitting, and in severe cases, skeletal fluorosis with joint pain and stiffness. Therefore, monitoring fluoride levels in dental products and drinking water is essential. In this study, we developed a rapid electrochemical detection method for fluoride ions using a preanodized screen-printed carbon electrode modified with 4-aminophenylboronic acid dimer (SPCE*/APBAD). The preanodization process involved applying a constant potential of +2 V for 5 min to capture APBAD. The resulting APBAD facilitated a chemical reaction between fluoride ions and boronic acid, forming a fluorophenylboronate complex. This complexation reaction enabled the detection of fluoride ions in a wide linear range (5 µM to 30 mM) with a detection limit of 0.3 µM. The detection behaviour of fluoride ion using SPCE*/APBAD has been studied using cyclic voltammetry, potentiometry, Density Functional Theoretical calculations and flow injection analysis. Furthermore, the practical utility of the sensor was validated by successfully detecting fluoride ions in toothpaste and water samples. The developed method offers a rapid and reliable means of monitoring fluoride ion levels for ensuring safe and beneficial use in dental products and drinking water.

Interaction Mechanism between Cyano-Organic Molecular Structures and Energy Storage of Aluminum Complex Ions in Aluminum Batteries.

Aluminum ion batteries (AIBs) are widely regarded as the most potential large-scale metal ion battery because of its high safety and environment-friendly characteristics. To solve the problem of weak electrical conductivity of organic materials, different structures of cyano organic molecules with electrophilic properties are selected as the cathode materials of aluminum batteries. Through experimental characterization and density functional theory theoretical calculation, Phthalonitrile is the best cathode material among the five organic molecules and proved that the C≡N group is the active site for insertion/extraction of AlCl2 + ions. The first cycle-specific capacity of the assembled flexible package battery is as high as 191.92mAhg-1 , the discharge-specific capacity is 112.67mAhg-1 after 1000 cycles, and the coulombic efficiency is ≈97%. At the same time, the influences of different molecular structures and functional groups on the battery are also proved. These research results lay a foundation for selecting safe and stable organic aluminum batteries and provide a new reference for developing high-performance AIBs.

A low-cost and efficient route for large-scale synthesis of NiCoSx nanosheets with abundant sulfur vacancies towards quasi-industrial electrocatalytic oxygen evolution

Transition-metal sulfides (TMS) have piqued a great deal of interest due to their unprecious nature and high intrinsic catalytic activity for water splitting. In this work, a low-cost and efficient route was developed, which included electrodeposition to prepare Ni-Co layered double hydroxide (NiCo-LDH) followed by ion exchange to form nickel cobalt sulfide (NiCoSx). Electrochemical reduction was used to modulate sulfur vacancies in order to produce sulfur vacancies-rich NiCoSx with nanosheet arrays on -three-dimensional nickel foam (NiCoSx-0.4/NF) with a large area of more than 250 cm2. Combining data from experiments and density functional theoretical (DFT) calculations reveals that engineered sulfur vacancies change the electronic structure, electron transfer property, and surface electron density of NiCoSx, significantly improving the free energy of water adsorption and boosting electrocatalytic activity. The developed NiCoSx-0.4/NF has long-term stability of more than 300 h at 500 mA cm−2 in 1 M KOH at ambient temperature and only needs a 289 mV overpotential at 100 mA cm−2. Remarkably, the synthesized electrocatalyst rich in sulfur vacancies, exhibits exceptional performance with a high current density of up to 1.9 A cm−2 and 1 A cm−2 in 6 M KOH and leads to overpotentials of 286 mV at 80 °C and 358 mV at 60 °C, respectively. The catalyst's practicability under quasi-industrial conditions (60 °C, 6 M KOH) is further demonstrated by its long-term stability for 220 h with only a 3.9 % potential increase at 500 mA cm−2.

Selective Electrocatalytic Oxidation of Nitrogen to Nitric Acid Using Manganese Phthalocyanine.

Ammonia is produced through the energy-intensive Haber-Bosch process, which undergoes catalytic oxidation for the production of commercial nitric acid by the senescent Ostwald process. The two energy-intensive industrial processes demand for process sustainability. Hence, single-step electrocatalysis offers a promising approach toward a more environmentally friendly solution. Herein, we report a 10-electron pathway associated one-step electrochemical dinitrogen oxidation reaction (N2OR) to nitric acid by manganese phthalocyanine (MnPc) hollow nano-structures under ambient conditions. The catalyst delivers a nitric acid yield of 513.2 μmol h-1 gcat-1 with 33.9% Faradaic efficiency @ 2.1 V versus reversible hydrogen electrode. The excellent N2OR performances are achieved due to the specific-selectivity, presence of greater number of exposed active sites, recyclability, and long period stability. The extended X-ray absorption fine structure confirms that Mn atoms are coordinated to the pyrrolic and pyridinic nitrogen via Mn-N4 coordination. Density functional theory-based theoretical calculations confirm that the Mn-N4 site of MnPc is the main active center for N2OR, which suppresses the oxygen evolution reaction. This work provides a new arena about the successful example of one step nitric acid production utilizing a Mn-N4 active site-based metal phthalocyanine electrocatalyst by dinitrogen oxidation for the development of a carbon-neutral sustainable society.

Anticancer and antimicrobial activities of a novel 4-nitrobenzohydrazone and the Cu(II), Ni(II), Co(II), and Mn(II) complexes

Antimicrobial and anticancer activities against prostate (PC-3) and breast (MCF-7) cancer cells by Schiff base derived from novel 4-Nitrobenzohydrazone ligand and its Cu(II), Ni(II), Co(II), and Mn(II) complexes are reported in this study. Characterizations by conventional spectroscopic techniques and elemental analyses suggest successful syntheses. The cobalt complex, Co(HL)2 was found to be moderately effective on both Pseudomonas aeruginosa ATCC 35032 and Candida albicans ATCC 10231, other compounds did not affect the test microorganisms. Results indicated that the compounds are effective on both prostate and breast cell lines at concentrations between 5 and 40 μM, and exhibit their effects by apoptotic mechanisms. The complex Mn(HL)2 could be a potential candidate against prostate cancer cells (PC-3). The interactions of ligand and complexes with biological targets were predicted by molecular docking which indicated high binding affinities, and artificial neural network explained their anticancer activities. Density functional theoretical calculations corroborated experimental findings.

Ensemble and single-particle level fluorescent fine-tuning of carbon dots via positional changes of amines toward "supervised" oral microbiome sensing.

Carbon dots (CDs) have attracted a host of research interest in recent years mainly due to their unique photoluminescence (PL) properties that make them applicable in various biomedical areas, such as imaging and image-guided therapy. However, the real mechanism underneath the PL is a subject of wide controversy and can be investigated from various angles. Our work investigates the effect of the isomeric nitrogen position as the precursor in the synthesis of CDs by shedding light on their photophysical properties on the single particles and ensemble level. To this end, we adopted five isomers of diaminopyridine (DAP) and urea as the precursors and obtained CDs during a hydrothermal process. The various photophysical properties were further investigated in depth by mass spectroscopy. CD molecular frontier orbital analyses aided us in justifying the fluorescence emission profile on the bulk level as well as the charge transfer processes. As a result of the varying fluorescent responses, we indicate that these particles can be utilized for machine learning (ML)-driven sensitive detection of oral microbiota. The sensing results were further supported by density functional theoretical calculations and docking studies. The generating isomers have a significant effect on the overall photophysical properties at the bulk/ensembled level. On the single-particle level, although some of the photophysical properties such as average intensity remained the same, the overall differences in brightness, photo-blinking frequency, and bleaching time between the five samples were conceived. The various photophysical properties could be explained based on the different chromophores formed during the synthesis. Overall, an array of CDs was demonstrated herein to achieve separation efficacy in segregating a mixed oral microbiome culture in a rapid (), high-throughput manner with superior accuracy. We have indicated that the PL properties of CDs can be regulated by the precursors' isomeric position of nitrogen. We emancipated this difference in a rapid method relying on ML algorithms to segregate the dental bacterial species as biosensors.

Engineering accordion-like Fe-doped NiS2 enabling high-performance aqueous supercapacitors and Zn-Ni batteries

Metal-organic frameworks are of great potential as electrode material in aqueous energy storage applications. In this work, a Fe-doped accordion-like Fe/NiS2 is fabricated by a simple hydrothermal treatment followed by anion exchange strategy. The Fe/NiS2 possesses large specific surface area and enhanced electrical conductivity ascribed to the unique 2D structure and rich defects aroused by Fe doping. By controlling the molar ratio of Ni:Fe to 1:0.01, the obtained Fe0.01NiS2 shows high specific capacitance (1965.9F/g at 0.5 A/g), the assembled Fe0.01NiS2//AC exhibits satisfying specific capacitance (183.11F/g at 0.2 A/g) and cycling property (75.6 % capacitance retention after 15,000 cycles). The aqueous Fe0.01NiS2//Zn also displays high capacity (193.33 mAh g−1 at 0.25 A/g) and cycling stability. The density functional theoretical calculations demonstrate that the Fe-doping can boost the charge storage ability and optimize adsorption energy of OH–. This work reveals a new method for construction of metal ion-doped MOF-based electrode materials for aqueous and other energy storage application.

Two-Dimensional Self-Assembly Driven by Intermolecular Hydrogen Bonding in Benzodi-7-azaindole Molecules on Au(111).

The control of molecular structures at the nanoscale plays a critical role in the development of materials and applications. The adsorption of a polyheteroaromatic molecule with hydrogen bond donor and acceptor sites integrated in the conjugated structure itself, namely, benzodi-7-azaindole (BDAI), has been studied on Au(111). Intermolecular hydrogen bonding determines the formation of highly organized linear structures where surface chirality, resulting from the 2D confinement of the centrosymmetric molecules, is observed. Moreover, the structural features of the BDAI molecule lead to the formation of two differentiated arrangements with extended brick-wall and herringbone packing. A comprehensive experimental study that combines scanning tunneling microscopy, high-resolution X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and density functional theory theoretical calculations has been performed to fully characterize the 2D hydrogen-bonded domains and the on-surface thermal stability of the physisorbed material.