Electronic Transport Properties Research Articles

Layer-dependent transport and optoelectronic properties in 2D all-inorganic Ruddlesden–Popper perovskite Cs2PbBr4

In recent years, two-dimensional (2D) all-inorganic Ruddlesden–Popper (RP) perovskites have attracted significant research attention. In this study, the electronic and carrier transport properties of 2D layered RP perovskite Cs2PbBr4 are studied by DFT calculations. The carrier mobility of the RP perovskite Cs2PbBr4 layers are studied based on deformation-potential (DP) theory. We found that the carrier mobility in 2D Cs2PbBr4 layers are enhanced as the number of layers increases. For trilayer Cs2PbBr4 the electron mobility reaches 7588.7 cm2V−1s−1, which is much higher than the widely studied bulk MAPbI3 (1500 cm2V−1s−1). In addition, the exciton binding energies are also calculated. Our work proves that the 2D RP perovskite Cs2PbBr4 layers are potential candidates for the photoelectronic devices applications.

Exploring Aromaticity Effects on Electronic Transport in Cyclo[n]carbon Single-Molecule Junctions.

Cyclo[n]carbon (Cn) is one member of the all-carbon allotrope family with potential applications in next-generation electronic devices. By employing first-principles quantum transport calculations, we have investigated the electronic transport properties of single-molecule junctions of Cn, with n = 14, 16, 18, and 20, connected to two bulk gold electrodes, uncovering notable distinctions arising from the varying aromaticities. For the doubly aromatic C14 and C18 molecules, slightly deformed complexes at the singlet state arise after bonding with one Au atom at each side; in contrast, the reduced energy gaps between the highest occupied and the lowest unoccupied molecular orbitals due to the orbital reordering observed in the doubly anti-aromatic C16 and C20 molecules lead to heavily deformed asymmetric complexes at the triplet state. Consequently, spin-unpolarized transmission functions are obtained for the Au-C14/18-Au junctions, while spin-polarized transmission appears in the Au-C16/20-Au junctions. Furthermore, the asymmetric in-plane π-type hybrid molecular orbitals of the Au-C16/20-Au junctions contribute to two broad but low transmission peaks far away from the Fermi level (Ef), while the out-of-plane π-type hybrid molecular orbitals dominate two sharp transmission peaks that are adjacent to Ef, thus resulting in much lower transmission coefficients at Ef compared to those of the Au-C14/18-Au junctions. Our findings are helpful for the design and application of future cyclo[n]carbon-based molecular electronic devices.

Tuned Reactivity at the Lithium Metal – Argyrodite Solid State Electrolyte Interphase

Thin intermetallic Li2Te–LiTe3 bilayer (0.75 mm) derived from 2D tellurene stabilizes solid electrolyte interphase (SEI) of lithium metal and argyrodite (LPSCl, Li6PS5Cl) solid-state electrolyte (SSE). Tellurene is loaded onto standard battery separator and reacted with lithium through single-pass mechanical rolling, or transferred directly to SSE surface by pressing. State-of-the-art electrochemical performance is achieved, e.g. symmetric cell stable for 300 cycles (1800 hours) at 1 mA cm-2 and 3 mAh cm-2 (25% DOD, 60 mm foil). Cryo-FIB sectioning and Raman mapping demonstrate that Li2Te–LiTe3 bilayer impedes SSE decomposition. The unmodified Li–LPSCl interphase is electrochemically unstable with geometrically heterogeneous reduction decomposition reaction front that extends deep into the SSE. Decomposition drives voiding in Li metal due to its high flux to the reaction front, as well as voiding in the SSE due to the associated volume changes. Analysis of cycled SSEs found no evidence for pristine (unreacted) lithium metal filaments/dendrites, implying failure driven by decomposition phases with sufficient electrical conductivity that span electrolyte thickness. Density Functional Theory (DFT) calculations clarify thermodynamic stability, interfacial adhesion, and electronic transport properties of interphases, while mesoscale modeling examines interrelations between reaction front heterogeneity (SEI heterogeneity), current distribution and localized chemo-mechanical stresses.

Montmorillonite Clay-Based Electrocatalyst for Water Splitting Applications

The goal of reaching net-zero emissions by the year 2050 requires a strategic overhaul to be realistically achievable. Hydrogen energy is considered an ideal substitute for fossil fuels, which leave carbon footprints and release hazardous chemicals into the atmosphere. Thus, large-scale commercialization of hydrogen energy could meet future energy demands with zero emissions. Electrochemical water splitting (EWS) is the most sustainable and efficient method to produce hydrogen for the next century. Thus, designing an electrocatalyst with an enhanced surface structure and abundant earth materials makes it a highly adoptable and affordable green energy. Smectite clay minerals are abundant on earth, non-hazardous, and easy to fabricate due to their clay nature. Among the smectites, montmorillonite is a promising candidate for electrocatalysts due to its unique physicochemical properties like expandable layered structure (TOT layers), high cation exchange, water adsorption, and swelling properties. Due to the high cationic exchange capacity of montmorillonite clays (70-110 meq/100g), the structural and interlayer cations can be tuned according to the water adsorption and desorption properties. When we look into the mineral structure, montmorillonite smectites belong to 2:1 phyllosilicate-layered sheets, composed of two tetrahedral silicate sheets (T) and one octahedral sheet (O). In each layer, an octahedral sheet is sandwiched between the two tetrahedral sheets (TOT), which is shown in Figure a. In the tetrahedral sheets, the dominant cation is Si4+, which is often substituted by the trivalent cation Al3+. The isomorphic substitution of Si4+ by Al3+ in the tetrahedral layer raises charge deficiency in the tetrahedral sheet, which is balanced by the absorbed interlayer cations like K+, Na+, and Ca2+ between the water molecules. In octahedral sheets, the common cations are Al3+, Mg2+, Fe3+, or Fe2+, and other cations like Ni2+, Li2+, and Cr2+. When the Mg2+ ions are substituted by Al3+ ions, it gives rise to a positive charge in the octahedral sheet. Depending upon the charges within the tetrahedral and octahedral sheets, the layered structure properties are altered. By considering their cation-rich and expandable properties, we have employed montmorillonite clay materials [Na,Ca)0.3 (Al,Mg)2 Si4O10(OH)2. nH2O] in electrocatalytic water splitting reactions for the first time. In our observation, annealing the montmorillonite at high temperatures such as 300 oC (Mont300/NF), 600 oC (Mont600/NF), and 900 oC (Mont900/NF), reconstruct the surface, and induce structural defects, which enables isomorphic substitution of bivalent (M2+) or trivalent cations (M3+). The annealed samples were prepared as slurry using binder additives (PVDF and NMP solvent) and coated on nickel foam (NF). The electrochemical performance was tested in a three-electrode potentiostat system in 1M KOH electrolyte, where the prepared sample was employed as the working electrode, graphite rod as the counter electrode, and Hg/HgO as the reference electrode. Figure b and c shows the electrochemical performances of the HER and OER reactions. Initially, the Mont600/NF catalysts show lower overpotential of 178 mV and 250 mV at 10 mA/cm2 for HER and OER reactions respectively. The pristine sample (Mont/NF) show much higher overpotential (240 mV for HER and 360 mV for OER). Thus, annealing promotes the formation of dangling bonds by generating cationic and anionic vacancies, which act as active sites for the adsorption of intermediates, which in turn reduces the requirement for higher overpotential. Furthermore, the pristine montmorillonite is mixed with functionalized CNT powder and annealed at the best performing temperature of 600oC (Mont+CNT600/NF). As a result, Mont+CNT600/NF sample shows much higher performance than Mont600/NF by requiring lower overpotential of 168 mV and 220 mV at 10 mA/cm2 for HER and OER reflecting the higher intrinsic kinetics owing to increased electrical conductivity due to CNT which enhances the electron transport properties and the water splitting kinetics. Interestingly, the used clay materials can be treated with organic solutions and can be reused due to their physicochemical retaining properties even after being treated at high temperatures. This would reduce the amount of solid catalyst waste going into landfills. Therefore, montmorillonite clay materials are the new era of catalyst’s material with recyclability due to their self-retaining physicochemical properties, water hydration, and dehydration properties. In this work, we have successfully optimized the montmorillonite properties by annealing at high temperatures, which helps to reconstruct the surface by breaking the OH lattice ions and creating dangling bonds. The formation of dangling bonds increases the rate of water splitting processes by acting as a surface-active site for the adsorption and desorption of H+ and OH- ions. Thus, tuning montmorillonite clays helps in achieving different water splitting properties. Figure 1

A novel characteristic curve for thermoelectric cooler application in realistic thermal circumstances: Theory and experiment

On the materials level, the performance of thermoelectric (TE) devices can be defined by the thermoelectric figure of merit (zT). This, however, does not provide a complete picture due to the complex interplay between electronic and thermal transport properties and the uncertain thermal impedance matching between external and internal thermal resistances in different realistic thermal circumstances. Appropriate design of individual material properties and geometry parameters considering the realistic thermal circumstance can greatly enhance the device-level performance of TE devices. In this work, we develop a framework to clarify such interactions in thermoelectric coolers (TEC) with a newly proposed q-h characteristic curve, which can be used to identify how a TEC design is of effectiveness for a specific realistic thermal circumstance. The effects of zT, the individual TE material properties (i.e., thermal conductivity k, electrical conductivity σ and Seebeck coefficient S) as well as the geometry parameters (i.e., pillar height and filling factor) on the q-h characteristic curve are theoretically and experimentally investigated, respectively. TEC modules with higher zT, short pillars and high filling factor show stronger capability to handle high heat flux load, especially for the cases with high heat dissipation coefficient at hot side. The thermal property (k) and electrical properties (σ and S) are responsible for the low heat flux load (e.g., wearable TEC) and high heat flux load (e.g., on-chip TEC cooling), respectively. For wearable TEC, increasing the internal thermal resistance can prevent the back flow heat, which can be achieved with tall pillars, low filling factor and optimizing zT towards lowering thermal conductivity k. For on-chip TEC cooling, reducing the Joule heating and increasing the thermoelectric effect become dominant factors in lowering the code-side temperature of TEC modules. This can be achieved with short pillars, high filling factor and optimizing zT towards increasing the power factor S2σ. This work provides significant insights into the complex interplay between material-level properties, device-level parameters and the external thermal circumstance in determining the performance of TEC devices. The results enable researchers to design optimal TEC devices for realistic applications with different boundary conditions.

Advancing Electrically Conductive Metal-Organic Frameworks for Photocatalytic Energy Conversion.

ConspectusPhotocatalytic energy conversion is a pivotal process for harnessing solar energy to produce chemicals and presents a sustainable alternative to fossil fuels. Key strategies to enhance photocatalytic efficiency include facilitating mass transport and reactant adsorption, improving light absorption, and promoting electron and hole separation to suppress electron-hole recombination. This Account delves into the potential advantages of electrically conductive metal-organic frameworks (EC-MOFs) in photocatalytic energy conversion and examines how manipulating electronic structures and controlling morphology and defects affect their unique properties, potentially impacting photocatalytic efficiency and selectivity. Moreover, with a proof-of-concept study of photocatalytic hydrogen peroxide production by manipulating the EC-MOF's electronic structure, we highlight the potential of the strategies outlined in this Account.EC-MOFs not only possess porosity and surface areas like conventional MOFs, but exhibit electronic conductivity through d-p conjugation between ligands and metal nodes, enabling effective charge transport. Their narrow band gaps also allow for visible light absorption, making them promising candidates for efficient photocatalysts. In EC-MOFs, the modular design of metal nodes and ligands allows fine-tuning of both the electronic structure and physical properties, including controlling the particle morphology, which is essential for optimizing band positions and improving charge transport to achieve efficient and selective photocatalytic energy conversion.Despite their potential as photocatalysts, modulating the electronic structure or controlling the morphology of EC-MOFs is nontrivial, as their fast growth kinetics make them prone to defect formation, impacting mass and charge transport. To fully leverage the photocatalytic potential of EC-MOFs, we discuss our group's efforts to manipulate their electronic structures and develop effective synthetic strategies for morphology control and defect healing. For tuning electronic structures, diversifying the combinations of metals and linkers available for EC-MOF synthesis has been explored. Next, we suggest that synthesizing ligand-based solid solutions will enable continuous tuning of the band positions, demonstrating the potential to distinguish between photocatalytic reactions with similar redox potentials. Lastly, we present incorporating a donor-acceptor system in an EC-MOF to spatially separate photogenerated carriers, which could suppress electron-hole recombination. As a synthetic strategy for morphology control, we demonstrated that electrosynthesis can modify particle morphology, enhancing electrochemical surface area, which will be beneficial for reactant adsorption. Finally, we suggest a defect healing strategy that will enhance charge transport by reducing charge traps on defects, potentially improving the photocatalytic efficiency.Our vision in this Account is to introduce EC-MOFs as an efficient platform for photocatalytic energy conversion. Although EC-MOFs are a new class of semiconductor materials and have not been extensively studied for photocatalytic energy conversion, their inherent light absorption and electron transport properties indicate significant photocatalytic potential. We envision that employing modular molecular design to control electronic structures and applying effective synthetic strategies to customize morphology and defect repair can promote charge separation, electron transfer to potential reactants, and mass transport to realize high selectivity and efficiency in EC-MOF-based photocatalysts. This effort not only lays the foundation for the rational design and synthesis of EC-MOFs, but has the potential to advance their use in photocatalytic energy conversion.

Electronic transport and magnetic properties of La1-xCaxMnO3 (0 < x ≤ 1)

We investigate the electronic transport and magnetic properties of La1-xCaxMnO3 across a wide range of calcium doping (x = 1/8, 1/4, 1/3, 1/2, 2/3, 3/4, and 1), unveiling distinct electronic and magnetic phase transitions. The findings can be summarized as follows. For samples with x = 1/8, 1/4, and 1/3, a transition temperature is observed at 188 K, 240 K, and 270 K, respectively. The x = 1/2 sample exhibits a charge ordering state, showing thermal hysteresis in electrical resistivity, thermopower, and magnetization. For samples with x = 2/3 and 3/4, a charge ordering state is observed at temperatures of 260 K and 225 K, respectively. However, there is no evidence of thermal hysteresis in terms of electrical resistivity, thermopower, and magnetization. Electrical resistivity and thermopower measurements follow the small polaron hopping model for x = 1/8, 1/4 and 1/3, while the variable range hopping model is applicable for x = 2/3, 3/4, and 1 at high temperatures. The sign and magnitude of the thermopower are found to be dependent on the calcium content. For samples with x less than 1/3, the thermopower is positive. In the case of the sample where x = 1/3, the thermopower changes sign, shifting from negative to positive below 101.8 K. Samples with x greater than 1/3 exhibit negative thermopower. The magnetization curves exhibit a decrease near the magnetic transition temperatures, specifically at 240 K for the x = 1/4 sample and 270 K for the x = 1/3 sample.

Triaxial strain enhanced thermoelectric performance and conversion efficiency in Tl3TaSe4

Thermoelectric (TE) materials have garnered significant attention due to their potential in converting waste heat into useful electrical energy. Strain engineering has emerged as a promising strategy for tailoring the properties of materials, offering opportunities to optimize TE performance. In this study, we employ first-principles calculations to investigate the electronic and thermal transport properties of cubic Tl3TaSe4 under triaxial strain. Our results demonstrate that tensile strain can reduce the effective mass of carriers and contribute to high carrier mobility. The phonon calculation and AIMD simulation reveal excellent dynamic stability and thermal stability of Tl3TaSe4 both with and without strain. The red shift phenomenon of phonon vibration modes and the higher portion of phonon DOS in the low frequency region indicate that tensile strain enhances the anharmonicity of Tl3TaSe4. In addition, triaxial tensile strain can effectively reduce the heat capacity, group velocity, and phonon lifetime, while enhancing the anharmonicity of Tl3TaSe4, which contributes to the lower κl. Compared to the condition without strain, the room temperature κl of Tl3TaSe4 under 1 % and 2 % tensile strain is reduced by about 43 % and 79 %, respectively. Furthermore, the tensile strain exhibits a positive enhancement effect on the ZT value of Tl3TaSe4. At 700 K, the optimal ZT values of p-type and n-type Tl3TaSe4 under 2 % tensile strain are 1.31 and 0.94, respectively, which are three times higher than that of 0.4 and 0.33 without strain. Finally, the TE conversion efficiency of Tl3TaSe4 under 2 % tensile strain is 6.8 %, which is higher than BiCuSeO and α-Cu2+xSe, and comparable to SnSe. Our results demonstrate the effectiveness of triaxial tensile strain in enhancing the phonon scattering, reducing the κl, and improving the TE properties of Tl3TaSe4.

Self-heating effects and switching dynamics in graphene multiterminal Josephson junctions

We experimentally investigate the electronic transport properties of a three-terminal graphene Josephson junction. We find that self-heating effects strongly influence the behavior of this multiterminal Josephson junction (MTJJ) system. We show that existing simulation methods based on resistively and capacitively shunted Josephson junction networks can be significantly improved by taking into account these heating effects. We also investigate the phase dynamics in our MTJJ by measuring its switching current distribution and find correlated switching events in different junctions. We show that the switching dynamics is governed by phase diffusion at low temperatures. Furthermore, we find that self-heating introduces additional damping that results in overdamped I−V characteristics when normal and supercurrents coexist in the device. Published by the American Physical Society 2024

Endless Dirac nodal lines and high mobility in kagome semimetal Ni3In2Se2 : a theoretical and experimental study

Kagome-lattice crystal is crucial in quantum materials research, exhibiting unique transport properties due to its rich band structure and the presence of nodal lines and rings. Here, we investigate the electronic transport properties and perform first-principles calculations for Ni3In2Se2kagome topological semimetal. First-principles calculations of the band structure without the inclusion of spin-orbit coupling (SOC) shows that three bands are crossing the Fermi level (EF), indicating the semi-metallic nature. With SOC, the band structure reveals a gap opening of the order of 10 meV.Z2index calculations suggest the topologically nontrivial natures (ν0;ν1ν2ν3) = (1;111) both without and with SOC. Our detailed calculations also indicate six endless Dirac nodal lines and two nodal rings with aπ-Berry phase in the absence of SOC. The temperature-dependent resistivity is dominated by two scattering mechanisms:s-dinterband scattering occurs below 50 K, while electron-phonon (e-p) scattering is observed above 50 K. The magnetoresistance (MR) curve aligns with the theory of extended Kohler's rule, suggesting multiple scattering origins and temperature-dependent carrier densities. A maximum MR of 120% at 2 K and 9 T, with a maximum estimated mobility of approximately 3000 cm2V-1s-1are observed. Ni3In2Se2is an electron-hole compensated topological semimetal, as we have carrier density of electron (ne) and hole (nh) arene≈nh, estimated from Hall effect data fitted to a two-band model. Consequently, there is an increase in the mobility of electrons and holes, leading to a higher carrier mobility and a comparatively higher MR. The quantum interference effect leading to the two dimensional (2D) weak antilocalization effect (-σxx∝ln(B)) manifests as the diffusion of nodal line fermions in the 2D poloidal plane and the associated encircling Berry flux of nodal-line fermions.

Weak localization and magnetoresistance phenomena of hydrogen-annealed WO3 films

We explore the electronic transport properties of hydrogenated epitaxial WO3 films. Ionized hydrogen not only generates an electron carrier but also acts as an impurity center, providing a useful approach to investigate a macroscopic quantum transport phenomenon of weak localization. Temperature dependent-resistivity and anomalous magnetoresistance results are analyzed based on Mott's variable range hopping and weak localization. From the model studies, the phase coherence length is estimated to have a temperature dependence of T −1.6 and is determined to vary from ∼22 nm at 80 K to ∼180 nm at 20 K. The length at 20 K is of a similar order of magnitude of film thickness, which requires a dimensional crossover between three-dimensional and two-dimensional localization.

Electron Transport through Linear-, Broken-, and Cross-Conjugated Polycyclic Compounds.

Quantum interference (QI) effects offer unique opportunities to modulate charge transport through single molecules. In recent years, several transmission selection rules have been developed to determine constructive and destructive QIs in an intuitive and simple manner, although some of these rules fail for cross-conjugated systems. In this work, we evaluate the performance of distinct transmission rules on a broad series of anthracene and fluorene derivatives with distinctive structural features including linear-, broken-, and cross-conjugation, heteroatoms, and five-membered rings as such species affords a predictive challenge for the qualitative selection rules for QI effects. The electron transport properties and local transmission plots are first evaluated by combining DFT and the nonequilibrium Green function method allowing for an equal-footing comparison of the conductance of the different polycyclic compounds. Our findings are in line with experimental observations on the influence of the type of conjugation and the connectivity to the metallic electrodes on the transport properties. Thus, cross-conjugated systems exhibit reduced conductance values as compared to the linear-conjugated ones, although the transmission is enhanced in the meta-connected junctions. Remarkably, our study reveals that aromatic cores exhibit generally larger zero-bias conductance for a given connectivity, in contrast to the negative aromaticity-conductance relationship found in literature.

Ultra-high electron mobility in Sn-doped two-dimensional Ga2O3 modified by biaxial strain and electric field

2D Ga2O3 exhibits overwhelming advantages over its bulk counterpart, whereas manipulating the carriers is rare. We report strain-dependent electronic structures and transport properties of Sn-doped 2D Ga2O3 using first-principles calculations with deformation potential theory. The band gaps are tunable from 2.23 eV to 1.20 eV due to the strain-mediated σ* anti-bonding and π bonding state variations. Specifically, ultra-high electron mobility of 22579.32 cm2V−1s−1 is predicated under 8% tensile. Further electric field modulations suggest the retaining of band gap and effective mass. These results highlight its property manipulations and nanoscale electronic applications.

Enhanced thermoelectric properties for eco-friendly CaTiO3 by band sharpening and atomic-scale defect phonon scattering

CaTiO3-based compounds have emerged as a promising thermoelectric material, renowned for their environmentally benign, thermally stable, and cost-efficient merits. Non-etheless, the pristine CaTiO3 manifests inherently low electronic transport properties. Herein, the thermoelectric properties of Ca1-xDyxTiO3 (x = 0, 0.05, 0.10, 0.15, 0.20) compounds are systematically investigated. The electrical transport properties are markedly enhanced by synergistic optimization of the carrier concentration, mobility, and density-of-states effective mass. Density functional theory results demonstrate that the conduction band tends to be sharper and that the lighter band participates in carrier transport after Dy doping. The large discrepancy in atomic mass results in considerable mass fluctuations, which give rise to intense phonon scattering. Benefitting from the modulated band structure and reduced thermal conductivity, the highest thermoelectric figure of merit (ZT) of 0.31 is achieved at 1073 K, enhanced by 287.5% in contrast with pristine CaTiO3 (ZTmax = 0.08). The defect and energy band modulation strategies proposed to optimize thermoelectric performance are applicable to other thermoelectric materials. This investigation inspires the exploration of high-performance and eco-friendly high-temperature thermoelectric material.

Tellurium doped sulfurized polyacrylonitrile nanoflower for high-energy-density, long-lifespan sodium-sulfur batteries

Sodium-sulfur (Na−S) batteries are promising energy storage devices for large-scale applications due to their high-energy-density and abundant material reserve. However, the practical implementation of room temperature (RT) Na−S batteries faces challenges, including low-energy-density and limited lifespan, particularly attributed to the properties of sulfurized polyacrylonitrile (SPAN). In this study, we address these challenges by introducing tellurium doping into SPAN nanoflowers, enhancing their performance for Na−S batteries. The resulting material exhibits high sulfur loading as well as superior electron and ion transport properties, leading to enhanced redox kinetics and improved battery performance. The tellurium-doped SPAN nanoflower electrode delivers an exceptional composite capacity of 700 mAh g−1 at 0.1 C and demonstrates stable cycling over 2400 cycles with minimal capacity fade (0.01 % average fading rate). Even under challenging conditions (24.0 mg cm−2, E/S=5 mg μLS−1, N/P=2.1), the Na−S battery achieves a high areal capacity of 16.1 mAh cm−2, resulting in an impressive energy density of 340.9 Wh kg–1 based on cathode and anode. This work presents a promising approach to designing high-energy-density, long-lifespan RT Na−S batteries, with potential applications for other metal-sulfur battery systems.

Molecularly Imprinted Viral Protein Integrated Zn-Cu-In-Se-P Quantum Dots Superlattice for Quantitative Ratiometric Electrochemical Detection of SARS-CoV-2 Spike Protein in Saliva.

Solution-processable colloidal quantum dots (QDs) are promising materials for the development of rapid and low-cost, next-generation quantum-sensing diagnostic systems. In this study, we report on the synthesis of multinary Zn-Cu-In-Se-P (ZCISeP) QDs and the application of the QDs-modified electrode (QDs/SPCE) as a solid superlattice transducer interface for the ratiometric electrochemical detection of the SARS-CoV-2-S1 protein in saliva. The ZCISeP QDs were synthesized through the formation of In(Zn)PSe QDs from InP QDs, followed by the incorporation of Cu cations into the crystal lattice via cation exchange processes. A viral-protein-imprinted polymer film was deposited onto the QDs/SPCE for the specific binding of SARS-CoV-2. Molecular imprinting of the virus protein was achieved using a surface imprinting electropolymerization strategy to create the MIP@QDs/SPCE nanosensor. Characterization through spectroscopic, microscopic, and electrochemical techniques confirmed the structural properties and electronic-band state of the ZCISeP QDs. Cyclic voltammetry studies of the QDs/SPCE superlattice confirmed efficient electron transport properties and revealed an intraband gap energy state with redox peaks attributed to the Cu1+/2+ defects. Binding of SARS-CoV-2-S1 to the MIP@QDs/SPCE cavities induced a gating effect that modulated the Fe(CN)6 3-/4- and Cu1+/2+ redox processes at the nanosensor interface, producing dual off/on ratiometric electrical current signals. Under optimal assay conditions, the nanosensor exhibited a wide linear detection range (0.001-100 pg/mL) and a low detection limit (0.34 pg/mL, 4.6 fM) for quantitative detection of SARS-CoV-2-S1 in saliva. The MIP@QDs/SPCE nanosensor demonstrated excellent selectivity against nonspecific protein targets, and the integration with a smartphone-based potentiostat confirmed the potential for point-of-care applications.

Electronic transport properties of tetracene molecular junctions formed with different metallic electrodes

Density functional theory in combination with non-equilibrium Green’s function is employed to study the electron transport properties of tetracene-based molecular junctions formed with silver, gold, copper and platinum electrodes. The physical origin of the IV curves is discussed by analyzing their density of states, molecular projected self-consistent Hamiltonian, transmission spectra, conductance trends and HOMO-LUMO gap at different operating voltages. The results indicate that till a low bias voltage of 1.4 V, the tetracene molecule shows metallic behavior with silver and copper electrodes while semi-metallic and non-metallic nature with gold and platinum electrodes respectively is observed. The zero bias conductance is found to be greatest for Ag followed by Cu and Au with the least in Pt. Furthermore, it is worth mentioning that negative differential resistance feature is observed in molecular junctions with all the electrodes except Pt, with the highest peak-to-valley current ratio of 1.283 found in Ag-Tetracene-Ag molecular junction.

Effects of strain and ferromagnetic metal stripe on the electron transport properties in a graphene

Effects of strain and ferromagnetic metal stripe on the electron transport properties in a graphene

Interstitials in Thermoelectrics.

Defect structure is pivotal in advancing thermoelectric performance with interstitials being widely recognized for their remarkable roles in optimizing both phonon and electron transport properties. Diverse interstitial atoms are identified in previous works according to their distinct roles and can be classified into rattling interstitial, decoupling interstitial, interlayer interstitial, dynamic interstitial, and liquid interstitial. Specifically, rattling interstitial can cause phonon resonance in cage compound to scatter phonon transport; decoupling interstitial can contribute to phonon blocking and electron transport due to their significantly different mean free paths; interlayer interstitial can facilitate out-of-layer electron transport in layered compounds; dynamic interstitial can tune temperature-dependent carrier density and optimize electrical transport properties at wide temperatures; liquid interstitial could improve the carrier mobility at homogeneous dispersion state. All of these interstitials have positive impact on thermoelectric performance by adjusting transport parameters. This perspective therefore intends to provide a thorough overview of advances in interstitial strategy and highlight their significance for optimizing thermoelectric parameters. Finally, the profound potential for extending interstitial strategy to various other thermoelectric systems is discussed and some future directions in thermoelectric material are also outlined.

Observing the Role of Electron Delocalization in Electronic Transport by Incorporating Actinides into Ligated Metal-Chalcogenide Superatoms.

Since delocalization of electronic states is a prerequisite for exerting unique electron transport properties, early actinides (An) with highly delocalized 5f/6d orbitals are natural candidates. However, given the experimental difficulties of such radioactive compounds and the complex relativistic effects in theoretical studies, understanding the electronic structure and bonding of actinides is underdeveloped on the periodic table. A further challenge is the very complicated electronic structures encountered in the confinement of actinides, as vividly illustrated by the weakly radioactive Th(Thorium)-encapsulated metal chalcogenide clusters, Th@Co6Te8L6 (L = PH3, PMe3, PEt3). Here we report the electronic structure and the electron transport properties of the Th@Co6Te8L6 clusters and compare them with those of the hollow Co6Te8L6 clusters using the nonequilibrium Green's function combined with relativistic density functional theory (NEGF-DFT). We found that the equilibrium conductance in Th@Co6Te8(PH3)6 (0.76 G0) has been greatly improved over that in Co6Te8(PH3)6 (0.03 G0), which has also been verified under an applied different bias voltage. The covalent bonding character between 6d (Th) and 3d (Co) atomic orbitals resulting from steric confinement is the source of the performance enhancement and a most important factor governing the accessibility of such 5f/6d orbitals. The results are of significance to the rapidly developing field of molecular nanoelectronics.