Electric Charge Transfer Research Articles

Design and DFT study of new nano buds from the combination of C60 fullerene and nanobowl

In this research, new nano buds of C60 fullerene compound and nanobowls were designed and their structure, electrical properties and optical properties were calculated. The absence of imaginary frequency and high cohesive energies is proof of stability and confirmation of the possibility of their formation. Calculation of the relative population showed that the E configuration is the dominant population. The calculation of electrical properties showed that combining the structures with each other improves the electrical properties of nanobuds. The highest electric charge transfer from nanobowl to C60 was observed in the configuration of C nanobuds. A high improvement in NLO properties was observed in all nanobud configurations. Calculating the contribution of the dispersion term in the energy of the nanobuds showed that compared to the parents, larger dispersion energy was obtained for the designed nanobuds (especially configuration E). It was shown that the energy of nano buds and their parents decreases in the presence of solvents. The decrease in energy as a function of increasing the dielectric constant of the solvents may be due to the increase in the dipole moments of the nanobud as a result of the electron transfer from the nanobowl to the C60 fullerene.

Electroactive covalent linkers for enhancing conducting polymer adhesion, charge transfer, and biological integration of PEDOT-coated carbon microfibers

Poly(3,4-ethylenedioxythiophene) (PEDOT)-coated carbon microfibers (PCMFs) are a key technology for developing advanced neuroprosthetic electrodes and electroactive tissue scaffolds. However, for their successful application in human therapeutics, PEDOT adhesion to the carbon substrate must be enhanced without compromising electric charge transfer. Here, electrically functional linkers are synthesized to modify the surface at the nanoscale, facilitating the covalent bonding of EDOT to carbon. The properties of the resulting microfibers are compared before and after PEDOT polymerization. PCMFs deterioration is studied by applying controlled mechanical stress in vitro or by implanting them in the rodent spinal cord in vivo. Amino phenyl-EDOT derivatives allow for efficient covalent carbon surface functionalization and PEDOT electropolymerization but substantially reduce charge transfer as assessed by chronopotentiometry, electrochemical impedance spectroscopy, and cyclic voltammetry. Nevertheless, the azido-EDOT (EDOT-Ph-N3) derivative is similarly effective for carbon surface modification, enabling PEDOT polymerization to develop a nanostructured CMF surface based on robust covalent bonds, and enhancing both electric charge transfer and PEDOT adhesion to the carbon substrate. This makes PCMFs more resistant to polymer delamination when assessed in vitro or when implanted into the neural tissue. Azido-EDOT modified PCMFs also show excellent biological integration within the spinal cord, causing negligible tissue damage and cell reactivity. Overall, azido-EDOT provides a superior electroconducting linker for anchoring PEDOT and optimizes the electrical, mechanical, and biological performance of PCMFs.

Impedance Spectroscopy Study of Charge Transfer in the Bulk and Across the Interface in Networked SnO2/Ga2O3 Core–Shell Nanobelts in Ambient Air

Metal oxide core–shell fibrous nanostructures are promising gas-sensitive materials for the detection of a wide variety of both reducing and oxidizing gases. In these structures, two dissimilar materials with different work functions are brought into contact to form a coaxial heterojunction. The influence of the shell material on the transportation of the electric charge carriers along these structures is still not very well understood. This is due to homo-, hetero- and metal/semiconductor junctions, which make it difficult to investigate the electric charge transfer using direct current methods. However, in order to improve the gas-sensing properties of these complex structures, it is necessary to first establish a good understanding of the electric charge transfer in ambient air. In this article, we present an impedance spectroscopy study of networked SnO2/Ga2O3 core–shell nanobelts in ambient air. Tin dioxide nanobelts were grown directly on interdigitated gold electrodes, using the thermal sublimation method, via the vapor–liquid–solid (VLS) mechanism. Two forms of a gallium oxide shell of varying thickness were prepared via halide vapor-phase epitaxy (HVPE), and the impedance spectra were measured at 189–768 °C. The bulk resistance of the core–shell nanobelts was found to be reduced due to the formation of an electron accumulation layer in the SnO2 core. At temperatures above 530 °C, the thermal reduction of SnO2 and the associated decrease in its work function caused electrons to flow from the accumulation layer into the Ga2O3 shell, which resulted in an increase in bulk resistance. The junction resistance of said core–shell nanostructures was comparable to that of SnO2 nanobelts, as both structures are likely connected through existing SnO2/SnO2 homojunctions comprising thin amorphous layers.

Enhancing the charge transfer in triboelectric nanogenerator based on sulfonated poly ether ether ketone/carbon nanotubes proton exchange composite membrane

This study introduces an innovative type of triboelectric nanogenerator (TENG) that utilizes proton exchange membranes to significantly enhance the transfer of electric charge in a triboelectric layer. To achieve this, composite membranes were fabricated by applying a blade coating technique to a mixture of carbon nanotubes (CNTs) and sulfonated poly ether ether ketone (SPEEK), serving as the critical triboelectric layer in the TENG device. These composite membranes exhibit an exceptional ability to attract water molecules through hydrogen bonding. Thanks to the high electro-positivity of these water molecules, they actively participate in the triboelectrification process, resulting in a substantial increase in charge transfer efficiency within the TENG device. As a result, when compared to the conventional dry-based SP (SPEEK)-TENG, the wet-based SP-TENG demonstrates an astonishing surge in output current, exceeding an 860-fold increase. Furthermore, a SPC (SPEEK/CNTs)-0.5-TENG cell device shows remarkable performance by generating a peak current of 0.91 mA and a power density of 0.39 W/m2. Impressively, four SPC-0.5-TENG cells can rapidly charge a 470 µF capacitor to 2.1 V within 28 seconds, making them a viable power source for a variety of portable electronic devices. This material displays substantial promise for applications in self-powered technologies, ultimately contributing to a reduced dependence on external power sources.

Modulation of catalyst interfacial electric field and charge transfer promotes NiS-modified CoWO4/ZnIn2S4 S-scheme heterojunction for efficient photocatalytic hydrogen evolution

The strategic post-synthetic modification of engineered S-scheme heterojunctions represents a potent and manipulable approach to significantly enhance photocatalytic activity. This study details the synthesis of innovative photocatalysts via the deposition of NiS nanoparticles onto S-scheme heterojunctions of CoWO4/ZnIn2S4 (CWO/ZIS-NiS), facilitated by solvothermal and photochemical methodologies. Under visible light irradiation, the hydrogen production rate of CWO/ZIS-NiS was 22.304 mmol g−1 h−1, which 14.7 times higher than that of the ZnIn2S4. XPS, EPR, SPV and DFT calculations were used to analyze the charge transfer path and the reasons for the performance improvement of the catalyst. The construction of the S-scheme CoWO4/ZnIn2S4 heterojunction, along with NiS modification to enhance the interfacial electric field (IEF) and act as a reaction center, was identified as the primary reason for the enhanced hydrogen production activity. This work provides guidance for the design of efficient photocatalytic systems using the synergistic effect between cocatalysts and S-scheme heterojunctions.

Novel nanobuds from the combination of B12N12 nanocage and carbon nanotube: Design and DFT study

In this research, carbon nanotubes and B12N12 nanocage were combined together and, in different configurations, a covalent bond between them was created to design new nanobuds. After optimizing the designed structures, their vibration frequency was calculated to ensure the absence of imaginary frequencies. Also, the relative energy of the structures was calculated and used to analyze the relative population of different configurations and showed that about 99 % of the molecules belong to a specific configuration (configuration B) and about 1 % belong to another configuration (configuration C). Consequently, the population of other configurations can be ignored. To further investigate the stability of structures, it was shown that configuration B has the highest cohesive energy and the most stability. It was clearly shown that the designed nanobuds have electrical properties similar to nanotubes and higher electrical conductivity than B12N12, and the electric charge transfer from B12N12 to nanotubes been taken place. Polarizability and superpolarizability, which indicate linear and nonlinear optical properties, were calculated. it was shown that the hybridization of B12N12 and carbon nanotubes and the creation of nanobuds improve the linear and nonlinear optical properties to a great extent. Finally, it was shown that similar to the parent nanotube, the nanobuds absorb light in the visible region, while B12N12 absorbs light in the UV region. The resulting nanobuds have more absorption lines than nanotubes and thus, their optical activity is even improved compared to nanotubes.

Finite dimension of the ion pathway networks in conducting glasses

In disordered materials, the ordinary understanding is that charge carriers tend to occupy energetically favorable sites known as ion-conducting channels. Many studies have revealed that the inherent fractal properties of such pathways lead to a sub-diffusive behavior. The linearity or branching of these pathways is crucial for determining how the charge carriers move. It can be thought that as the space dimensionality decreases, the average distance between the highest energy barriers along the conduction paths increases. In this study the finite dimension of those pathways is computed using an extended version of the classical Hausdorff dimension. Also, the Arrhenius behavior of the most mobile lithium ions is proved, confirming that such are responsible for conductivity behavior. The lithium ions mobility behavior in response to temperature changes and the finite dimension allowed to identify the ion diffusion regions fractal features. The reported results demonstrate that as the temperature increases the conducting channels become broadener, facilitating the transfer of electrical charge through the glassy matrix, below the transition temperature. The pathways behavior confirms the increase of the ionic conductivity when the temperature increases as it is experimentally observed.

Electro-assisted sorption behavior and mechanism of low-concentration rare earth elements on carbon based materials

With increasing demands for rare earth elements (REEs) in high-tech and futuristic applications, developing efficient methods for recovering low-concentration REEs is necessary. Here, electro-assisted sorption of low-concentration REEs, La(III), Gd(III) and Y(III) (as symbol of light, medium, and heavy REEs) on carbon-based materials, activated carbon (AC), graphene, and graphite by a facile method was reported. Recovery of La(III), Gd(III) and Y(III) could reach ∼100 % under low-concentration condition where the maximum adsorption capacity was up to 342.38 mg/(g·dm2). Variants including applied voltage, electrodes-distance, pH, impurities, and concentration were considered to study the effects on REEs recovery. Interestingly, adsorption capacity and recovery under low voltage were respectively almost 20 and 14 folds than that without voltage, because voltage promoted REEs transfer and strengthened electrostatic interaction between electrodes and REEs. The mechanism for enhancing REEs recovery on carbon-based electrodes was resulted from high electric double layer (EDL) capacitance and low charge transfer resistance. Total desorption of REEs from electrodes could be quickly realized using NH4Cl or HCl solution. Overall, the study gave a new insight of low-concentration REEs recovery using carbon-based materials, and provided an efficient route using electric method with porous materials for REEs recovery.

Engineering Local Graphitic Domains to Balance Defect Active Site and Electronic Conduction Ability in Coal‐Derived Carbon Anode for Superior Potassium Ions Storage

AbstractPotassium‐ion hybrid capacitors (PIHCs) are regarded as one of the promising candidates for large‐scale energy storage technologies. Nevertheless, the lack of suitable anode materials combined with fast ion diffusion kinetics and favorable cycle stability restricts their application. Herein, a catalyst‐confined graphitization strategy is proposed to synthesize low‐cost coal‐based carbon anodes, which have controllable heteroatom co‐doping and rich defect sites, together with local graphitic domains. Density functional theory calculations and kinetic analysis are performed to uncover the coupling effect for heteroatom dual‐doping and defective structures. Importantly, the introduction of graphitic domains ensures good electric conductivity and charge transfer kinetics while preserving rich defects and active sites. The optimized NC‐950 exhibits superior potassium storage capacity, which delivers a high reversible specific capacity (363.3 mAh g−1), impressive rate capability (93.9 mAh g−1 at 2 A g−1), and stable cycling performance. As a practical device application, the PIHCs (NC‐950//AC) are assembled using the NC‐950 anode and commercial activated carbon (AC) cathode, which exhibits the maximum energy density of 97.0 Wh kg−1 and excellent cycling stability (10 000 cycles). Significantly, this work unveils a new pathway to developing low‐cost and fast reaction kinetics carbon anode for advanced electrochemical supercapacitors.

Computational Chemistry: Prediction of Compound Accessibility of Targeted Synthesized Compounds.

In the present work, a series of novel pyridine carboxamides 3(a-h) were synthesized and screened with antibacterial activity. This research explores the application of Density Functional Theory (DFT) in studying biological systems at the quantum mechanical level, particularly in the context of drug design. DFT offers a streamlined approach to quantum mechanical calculations, making it indispensable in various scientific fields, and for its exceptional accuracy, reduced computational time, and cost-effectiveness has become a pivotal tool in computational chemistry. This research work highlights the integration of DFT studies with POM analyses, which effectively identify pharmacophoric sites. Moreover, the research incorporates in silico pharmacokinetics analyses to assess the pharmacokinetic properties of synthesized compounds. The paper focused on a series of compounds previously reported, aiming to provide a comprehensive understanding of their electronic structure, pharmacophoric features, and potential as drug candidates. This study not only contributes to the evolving field of computational chemistry but also holds implications for advancing drug design processes by combining theoretical insights with practical analyses. The compounds 3(a-h) were subjected to Density Functional Theory (DFT) computations using the B3LYP/6-31G(d) basis set to get optimized geometric structures. GaussViewis used to display the contributions of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). The determination of energy gaps was conducted using Gaussian 09W. The pharmacokinetic profiles were evaluated using existing techniques such as Osiris, Petra, and Molinspiration, as well as a novel platform called POM Analyse. The computational studies DFT, POM and in silico pharmacokinetics studies revealed that the studied compounds are biologically active, non-toxic, non-carcinogenic in nature and may be utilized as drug candidates. Density functional theory (DFT) investigations emphasize the exceptional stability of complex 3d, which possesses the biggest energy gap and the lowest softness. In contrast, compound 3h demonstrates poorer stability among the tested compounds, characterized by the lowest energy gap and the highest softness values. These findings are further substantiated by absolute energy calculations. The negligible energy difference in compound 3h indicates an increased transfer of electric charge within the molecule, which is associated with its enhanced biological effectiveness. The drug-likeness of the compounds is confirmed by POM and in silico pharmacokinetics investigations, with compound 3h being identified as the most biologically active among the investigated compounds.

Synergy of Mo doping and heterostructures in FeCo2S4@Mo-NiCo LDH/NF as durable and corrosion-resistance bifunctional electrocatalyst towards seawater electrolysis at industrial current density

Electrolysis of seawater to produce hydrogen is a replenished way to utilize sustainable hydrogen energy. However, it remains a challenge to develop electrocatalysts with high chloride corrosion resistance and meet the industrial-required low overpotential at large current density. Here, a heterostructure FeCo2S4@Mo-NiCo LDH/NF (FCS@M-NC LDH/NF) catalyst consisting of Mo-doped NiCo LDH nanosheets on FeCo2S4 nanorods grown on nickel foam is demonstrated as a large-current–density electrocatalyst for seawater electrolysis. The hierarchical structure endows FCS@M-NC LDH/NF with abundant active sites and hydrophilic and aerophobic surfaces, which promotes the adsorption of OH− and accelerates gas-release capabilities during water electrolysis. Moreover, the incorporation of high-valence Mo species and the presence of heterostructures contribute to the outstanding corrosion resistance, selectivity, and activity of FCS@M-NC LDH/NF, which only requires 314 mV (HER) and 307 mV (OER) overpotential to achieve a large current density of 1000 mA cm−2 in alkaline electrolysis of seawater. Impressively, it maintains stable operation for 140 h at a current density of 500 mA cm−2 without the production of hypochlorite. Furthermore, density functional theory calculations demonstrate that Mo doping and formation of heterostructures decrease the adsorption energy barrier for intermediate on FCS@M-NC LDH/NF, which promotes electrocatalytic activity. The robust electronic interaction between FCS and M-NC LDH/NF promotes the redistribution of charges on the interface, boosting electrical conductivity and charge transfer in the FCS@M-NC LDH/NF. This study offers a mild way to create a bifunctional electrocatalyst with exceptional corrosion resistance and stability in industrial high-alkaline natural seawater electrolysis.

Mathematical Model Based on Staircase Structure for Impedance Analysis of Non-Ideal and Non-Uniform Processes in Porous Electrodes

Electrochemical impedance spectroscopy analysis for porous electrodes in energy conversion and storage, described as resistance and capacitance, is widely used to understand their electrochemical processes. These processes include: (i) electronic resistance inside the electrode (R e), (ii) ionic resistance in the electrolyte bulk and inside the porous electrode (R ion), (iii) electrical double layer formation (C dl) and charge transfer resistance at the electrode electrolyte interface (R ct) , and (iv) diffusion for charge compensation.As one of the mathematical models in electrochemical impedance spectroscopy for porous electrodes, a transmission line model is known, in which the pore structure is described as a cylinder geometry.1 We have proposed an analytical method that combines the transmission line model with electrochemical impedance spectroscopy using a symmetric cell,2 and have investigated resistance separation in lithium-ion batteries and its effect on battery performances.3-5 Due to mathematical constraints, the transmission line model is limited to a representation of an ideal, uniform process model. Here we propose a mathematical model based on a network model consisting of a staircase structure for electrochemical impedance spectroscopy at porous electrodes that can describe not only ideal and uniform processes but also non-ideal and non-uniform processes (Fig. 1), and aims to help elucidate their borderline behavior.6 The proposed staircase model (Z SCM) gives a series equivalent circuit consisting of Z 0, which is a series circuit of electrode/electrolyte interface impedance (Z int0) and electronic resistance (R e0), and electrolyte resistance (R ion0) as an initial step without pores (Z SCM0 = R ion(0) + Z 0). The one-step model (Z SCM1) is then given a series equivalent circuit consisting of the parallel circuit of Z SCM0 and Z 1 and the electrolyte resistance R ion(1) in series (Z SCM1 = R ion(1) + (Z SCM0 −1+Z1 −1)−1). The staircase model is calculated by incorporating the 1 prior step (Fig. 2). Thus, the model with n steps (Z SCM(n)) is composed of a series equivalent circuit of the parallel circuit of Z SCM(n−1) and Z n and the electrolyte resistance R ion(n) (Z SCM(n) = R ion(n) + (Z SCM(n−1) −1 +Z n −1)−1).Fig. 3 shows Nyquist plots computed for each input parameter at 50 steps for non-Faradic and Faradic processes in the staircase model. The results are in good agreement with the profiles calculated for the transmission electric model.2 The presentation will further show examples of the calculated results using the staircase model for non-ideal and inhomogeneous processes and discuss the analysis of impedance behavior using real electrodes reflecting non-uniform processes. References R. de Levie, Electrochim. Acta, 9, 1231-1245 (1964). N. Ogihara, S. Kawauchi, C. Okuda, Y. Itou, Y. Takeuchi and Y. Ukyo, J. Electrochem. Soc., 159, A1034-A1039 (2012). N. Ogihara, Y. Itou, T. Sasaki and Y. Takeuchi, J. Phys. Chem. C, 119, 4612-4619 (2015). N. Ogihara, Y. Itou and S. Kawauchi, J. Phys. Chem. Lett., 10, 5013-5018 (2019). Y. Itou, N. Ogihara and S. Kawauchi, J. Phys. Chem. C, 124, 5559-5564 (2020). N. Ogihara and Y. Itou, Phys. Chem. Chem. Phys., 24, 21863-21871 (2022). Figure 1

Adjustable Ti2C3Alx-based segregated composite network for enhanced electromagnetic shielding and fire safety

With the rapid development of communication technology and portable electronic devices, the demand for the design of electronic devices with superior electromagnetic interference shielding and fire safety performance is increasing. Herein, epoxy resins (EPs) with typical segregated networks were designed by emulsion polymerization and adhesion self-assembly strategies and novel polyphosphonitrile microspheres (PZS) synthesized by precipitation polymerization were used to improve the fire safety of EP composites. It is worth noting that the oil-water (EP to water) ratio in emulsion polymerization is closely related to the microscopic morphology of the segregated network. A smaller ratio of EP to water results in more paths for electrical charge transfer through the EP composites. As a result, EP/PT-3 with a minimum oil-to-water ratio exhibits a high EMI SE (electromagnetic interference shielding effectiveness) in the X-band ranging from 40.12 to 40.30 dB at a loading of 7.20 vol% Ti3C2Alx. Besides, the synergistic action of the adjustable Ti3C2Alx network with PZS endows EP superior flame retardant performance. Compared with EP, the PHRR and THR values of EP/PT-3 are down 55.7 % and 72.6 %, respectively. There is no doubt that EP/PT-3 has provided a new route for the preparation of Ti3C2Alx-based electromagnetic shielding and fireproof materials.

Synthesis and characterization of erbium decorated V2CTx for water splitting properties

The implication of two-dimensional (2D) MXene and their composites as catalysts for hydrogen (H2) and oxygen (O2) production represents an exciting area of research with great potential to revolutionize the field of catalysis. Herein, we demonstrated a method for surface modification of V2CTx MXene nanosheets (NSs) as an effective bifunctional nanocomposite electrocatalyst for water-splitting applications. This method involves the careful adsorption of the Erbium (Er) onto V2CTx NSs. Nanocomposites of Er@V2CTx were prepared by the sonication method. The Er@V2CTx in weight percentage ratio (0.12:1) nanocomposite (labeled as) achieved overpotentials of 174 mV vs. RHE (Reversible hydrogen electrode) and 370 mV (vs. OER) at the Tafel slope of 107 mV/dec for hydrogen evolution reaction (HER) and 131 mV/dec for the oxygen evolution reaction (OER) respectively, in 1.0 M KOH solution. The X-ray diffraction (XRD) analysis of pristine V2CTx and Er-decorated V2CTx (Er@V2CTx) nanocomposites revealed the presence of a 2D MXene structure with an increase in c-lattice parameter from 13.01 Å to 19.94 Å, indicating the successful adsorption of Er into MXene. Further, scanning electron microscopy (SEM) demonstrates that all samples have layered structures with evident sheet separation. The V2CTx MXene had strong electrical coupling, charge transfer, and contact, which resulted in substantially improved water-splitting performance, structural stability, and low charge transfer resistance, ultimately enhancing the catalyst's intrinsic activity.

Mapping Capillary Infiltration-Induced Potential in Water-Triggered Electric Generator Using an Electrical Probe Integrated Microscope.

Power generation from water-triggered capillary action in porous structures has recently geared extensive attention, offering the potential for generating electricity from ubiquitous water evaporation. However, conclusively establishing the nature of electrical generation and charge transfer is extremely challenging arising from the complicated aqueous solid-liquid interfacial phenomenon. Here, an electric probe-integrated microscope is developed to on-line monitor the correlation between water capillary action and potential values at any desired position of an active layer. With a probe spatial resolution reaching up to fifty micrometers, the internal factors prevailing over the potential distribution across the whole wet and dry regions are comprehensively identified. Further, the self-powered sensing capabilities of this integrated system are also demonstrated, including real-time monitoring of wind speed, environmental humidity, ionic strength, and inclination angle of generators. The combination of electric potential and chemical color indicator suggests that charge generation is likely correlated with ion-selective transport in the nanoporous channel during the water infiltration process. And unipolar ions (for instance protons) should be the dominant charge-transfer species. The work reveals the fundamental principles regulating charge generation/transfer during the water-triggered electric generation process.

Zero-Field Spin Waves in YIG Nanowaveguides.

Spin-wave-based transmission and processing of information is a promising emerging nanotechnology that can help overcome limitations of traditional electronics based on the transfer of electrical charge. Among the most important challenges for this technology is the implementation of spin-wave devices that can operate without the need for an external bias magnetic field. Here we experimentally demonstrate that this can be achieved using submicrometer wide spin-wave waveguides fabricated from ultrathin films of a low-loss magnetic insulator, yttrium iron garnet (YIG). We show that these waveguides exhibit a highly stable single-domain static magnetic configuration at zero field and support long-range propagation of spin waves with gigahertz frequencies. The experimental results are supported by micromagnetic simulations, which additionally provide information for the optimization of zero-field guiding structures. Our findings create the basis for the development of energy-efficient zero-field spin-wave devices and circuits.

Electrical properties of hierarchical nitrogen-doped multi-walled carbon nanotubes obtained using cobalt nanoparticles

In this work, for the first time, both initial and secondary branches of hierarchical nitrogen-doped multi-walled carbon nanotubes (h-N-MWCNTs) were obtained using chemical vapor deposition due to the decomposition of ace-tonitrile over Co-based nanoparticles. The results of a study of the electrical conductivity of h-N-MWCNTs for a wide temperature range of 300−4.2 K are presented. It was shown that fluctuation-assisted tunneling between delocalized states is the dominant conduction mechanism at temperatures above 50 K. An analysis of the temperature and electric field dependences of the resistance indicates that the transfer of electric charges below 50 K occurs due to hoppings between localized states located in the vicinity of the Fermi level. It was shown that the Coulomb interaction affects the charge carrier transport. The width of the Coulomb gap estimated from the temperature dependence of the resistance is 0.5 meV. The electrical conductivity of h-N-MWCNTs in the temperature range of 50−4.2 K occurs by the Efros–Shklovskii variable range hopping conduction mechanism. It was found that the charge localization length is ≈150 nm. Electrical property analysis indicates that the dielectric constant of the h-N-MWCNTs is ≈ 100.

Metal-organic-framework-derived porous core/shell CoP polyhedrons intertwined with 2D MXene as anode for Na-ion storage

Transition metal phosphides (TMPs) are considered satisfactory anode candidates for sodium-ion batteries (SIBs) due to their high energy density and modest plateau. However, the TMPs anode suffers from poor cycling and rate properties owing to the negative effects of severe volumetric expansion and sluggish reaction kinetics. Herein, a novel structure of porous core/shell CoP@N-C nano polyhedral embedding on 2D MXene nanosheets (CoP@N-C/MXene) was synthesized by self-assembly and in-situ phosphorization methods. The porous CoP@N-C with the unique core/shell structure benefits the infiltration of electrolytes and alleviates the volumetric change. Besides, high-conductive 2D MXene nanosheets could enhance electrical conductivity and charge transfer kinetics, and effectively inhibit CoP@N-C pulverization and agglomeration. Based on the above advantages, the as-prepared CoP@N-C/MXene anode delivers an excellent cycling capacity, outstanding rate capability and low-temperature high-rate capability. This synthetic strategy of CoP@N-C/MXene architecture can be extended to other materials which are promising for SIBs electrodes.

Quantum Chemical Studies on Possible Molecular Devices Based on Electric Field-Induced Intramolecular Charge Transfer.

We report quantum chemical studies on possible molecular devices working based on electric field-induced intramolecular charge transfer (EFIMCT). In the case of donor-acceptor (DA)-type molecular systems, intramolecular charge transfer (IMCT) can be induced by applying the external electric field to molecular systems along the charge transport direction, providing a possible switching mechanism which does not depend upon the electron-phonon coupling effect and is different from the negative differential resistance mechanism observed in the well-known NO2-substituted phenylene ethynylene oligomers. When the EFIMCT proceeds, the molecular systems have strong static electron correlation effects, where the standard nonequilibrium Green's function-density functional theory (DFT) approach cannot be applied to the molecular junction. As a first step toward practical switching devices, we do quantum chemical studies on the EFIMCT in such molecular systems as an isolated molecule, instead of using the electrode-junction-electrode open quantum system model. A prototype molecule P1 is designed as a tentative candidate molecule where the EFIMCT can proceed. The complete active space self-consistent field (CASSCF) molecular orbital calculations on P1 indicate that the EFIMCT can proceed at the external electric field intensity of 0.003 au, corresponding to about 2.25 V bias voltage. This calculated result strongly suggests that the development of this type of switching devices working at practically low bias voltage is feasible if the molecular system is properly designed. Broken symmetry unrestricted Hartree-Fock and spin-polarized Kohn-Sham DFT calculations also qualitatively reproduce the CASSCF results on P1, to some extent, indicating that these approaches can be employed for rough estimations on the EFIMCT such as the first screening of a large quantity of candidate molecules for this type of molecular devices. The possibility of molecular memory devices based on the EFIMCT is also discussed by analyzing the ground and excited potential energy surface model. Remaining challenges to develop practical molecular devices are discussed.

Octacalcium Phosphate-Laden Hydrogels on 3D-Printed Titanium Biomaterials Improve Corrosion Resistance in Simulated Biological Media.

The inflammatory-associated corrosion of metallic dental and orthopedic implants causes significant complications, which may result in the implant's failure. The corrosion resistance can be improved with coatings and surface treatments, but at the same time, it might affect the ability of metallic implants to undergo proper osteointegration. In this work, alginate hydrogels with and without octacalcium phosphate (OCP) were made on 3D-printed (patterned) titanium alloys (Ti Group 2 and Ti-Al-V Group 23) to enhance their anticorrosion properties in simulated normal, inflammatory, and severe inflammatory conditions in vitro. Alginate (Alg) and OCP-laden alginate (Alg/OCP) hydrogels were manufactured on the surface of 3D-printed Ti substrates and were characterized with wettability analysis, XRD, and FTIR. The electrochemical characterization of the samples was carried out with open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). It was observed that the hydrophilicity of Alg/OCP coatings was higher than that of pure Alg and that OCP phase crystallinity was increased when samples were subjected to simulated biological media. The corrosion resistance of uncoated and coated samples was lower in inflammatory and severe inflammatory environments vs. normal media, but the hydrogel coatings on 3D-printed Ti layers moved the corrosion potential towards more nobler values, reducing the corrosion current density in all simulated solutions. These measurements revealed that OCP particles in the Alg hydrogel matrix noticeably increased the electrical charge transfer resistance at the substrate and coating interface more than with Alg hydrogel alone.