Tunable Electronic Properties Research Articles

The Emergence of Mem-Emitters.

The advent of memristors and resistive switching has transformed solid-state physics, enabling advanced applications such as neuromorphic computing. Inspired by these developments, we introduce the concept of Mem-emitters, devices that manipulate light-emission properties of semiconductors to achieve memory functionalities. Mem-emitters, influenced by past exposure to stimuli, offer a new approach to optoelectronic computing with potential for enhanced speed, efficiency, and integration. This study explores the unique properties of transition-metal dichalcogenide-based heterostructures as a promising platform for Mem-emitter functionalities because of their atomic-scale thickness, tunable electronic properties, and strong light-matter interaction. When distinguishing between population-driven and transition rate-driven Mem-emitters, we highlight their potential for various applications, including optoelectronic switches, variable light sources, and advanced communication systems. Understanding these mechanisms paves the way for innovative technologies in memory and computation, providing insights into the intrinsic dynamics of complex systems.

Tunable Electronic and Optical Properties of Hydrogenated MoO3 Films by Metal–Acidic Ionic Liquid Treatment

Tunable Electronic and Optical Properties of Hydrogenated MoO3 Films by Metal–Acidic Ionic Liquid Treatment

Biphasic 1T/2H-MoS2 Nanosheets In Situ Vertically Anchored on Reduced Graphene Oxide via Covalent Coupling of the Mo-O-C Bond for Enhanced Electrocatalytic Hydrogen Evolution.

Transition-metal dichalcogenides (TMDs) have recently emerged as promising electrocatalysts for the hydrogen evolution reaction owing to their tunable electronic properties. However, TMDs still encounter inherent limitations, including insufficient active sites, poor conductivity, and instability; thus, their performance breakthrough mainly depends on structural optimization in hybridization with a conductive matrix and phase modulation. Herein, a 1T/2H-MoS2/rGO hybrid was rationally fabricated, which is characterized by biphasic 1T/2H-MoS2 nanosheets in situ vertically anchored on reduced graphene oxide (rGO) with strong C-O-Mo covalent coupling. The rGO substrate improves the conductivity and ensures high-dispersed 1T/2H-MoS2 nanosheets to expose plentiful highly active edges. More importantly, the strong heterointerface electrical interaction by the C-O-Mo covalent bond can enhance the charge-transfer efficiency and reinforce structural stability. Furthermore, the integration with the appropriate 2H phase is in favor of stabilization of the metastable 1T phase; thus, the ratio of 1T and 2H was precisely regulated to balance activity and stability. With these advantages, the 1T/2H-MoS2/rGO catalyst presents a satisfactory activity and stability, as confirmed by the relatively low overpotential (268 and 140 mV at 10 mA cm-2) and the small Tafel slope (102 and 86 mV dec-1) in alkaline and acidic media, respectively. The theory calculations disclose that the electronic structure redistribution has been optimized via the strong coupled C-O-Mo heterointerface and phase interface, significantly reducing the adsorption free energy of hydrogen and improving intrinsic activity.

High stability cubic perovskite Sr0.9Y0.1Co1-xFexO3-δ oxygen evolution by phase control and electrochemical reconstruction

Transition metal oxides are considered ideal electrocatalyst materials due to their low cost and high intrinsic activity. Among them, SrCoO3-δ has received increasing attention due to its multi-phase structure and tunable electronic properties, though its OER reaction kinetics and catalysis stability are unsatisfactory. Herein, based on a simple one-step solid-state reaction method, we use a small amount of rare earth Y ions (10 %) to transform H-SCO2.52 from a hexagonal structure to a stable cubic perovskite Sr0.9Y0.1CoO3−δ. While broadening the atomic ratio of Co and Fe in the B-site under the cubic perovskite Sr0.9Y0.1Co1-xFexO3−δ (x = 0–1), the relationship between the B-site electronic state, oxygen vacancies, and OER performance has been explored. Sr0.9Y0.1Co0.2Fe0.8O3−δ with a high concentration of oxygen vacancies, exhibits the lowest overpotential of 277 mV and maintains stability at 10 mA cm−2 for 88 h. The valence states of Fe and Co atoms in SYC0.2F0.8 O are optimized (Fe2+∼50.81 %, Co2+∼19.39 %), and the oxygen evolution activity is enhanced by electrochemical reconfiguration to form high-valence Fe and Co ions. Selective leaching of Sr ions via electrochemical surface reconstruction activates FeOOH and CoOOH amorphous layer active sites on the catalyst surface, significantly enhancing reaction kinetics.

Preferential graphitic-nitrogen formation in pyridine-extended graphene nanoribbons

Graphene nanoribbons (GNRs), nanometer-wide strips of graphene, have garnered significant attention due to their tunable electronic and magnetic properties arising from quantum confinement. A promising approach to manipulate their electronic characteristics involves substituting carbon with heteroatoms, such as nitrogen, with different effects predicted depending on their position. In this study, we present the extension of the edges of 7-atom-wide armchair graphene nanoribbons (7-AGNRs) with pyridine rings, achieved on a Au(111) surface via on-surface synthesis. High-resolution structural characterization confirms the targeted structure, showcasing the predominant formation of carbon-nitrogen (C-N) bonds (over 90% of the units) during growth. This favored bond formation pathway is elucidated and confirmed through density functional theory (DFT) simulations. Furthermore, an analysis of the electronic properties reveals metallic behavior due to charge transfer to the Au(111) substrate accompanied by the presence of nitrogen-localized states. Our results underscore the successful formation of C-N bonds on the metal surface, providing insights for designing new GNRs that incorporate substitutional nitrogen atoms to precisely control their electronic properties.

Tunable electronic structure and excellent catalytic properties of transition-metal-doped BeN4 monolayer.

The electronic properties and OER catalytic activity of pristine BeN4 monolayers and single-transition-metal-doped BeN4 monolayers (TM@BeN4) were systematically investigated using density functional theory. Among all the types of TM@BeN4 analyzed, Fe@BeN4 was determined to exhibit the best OER activity, with an overpotential of 0.33 V, and to display excellent metallic conductivity. Besides, the OER catalytic activity of Fe@BeN4 can be further enhanced by applying biaxial strain and designing X-Fe@BeN4 (X = B, C, O, P, S) catalysts.

Efficient CeO2/ZnO heterojunction for enhanced heterogeneous photocatalytic application

Organic pollutants pose a significant challenge due to their toxicity and potential carcinogenicity, thereby posing a severe threat to the environment and human health. Heterogeneous photocatalysts offer promising advantages over traditional water purification methods due to their tunable electronic properties such as bandgap, easy separation from the reaction solution and formidable nanostructures. Herein, we prepare a CeO2/ZnO heterostructure via simple hydrothermal synthesis. The electronic structure of this nanocomposite was tuned to achieve a band gap of ∼2.94 eV, which was between the individual bandgaps of CeO2 and ZnO nanoparticles. In addition, the mixed valence character of Ce further enhanced the electronic properties of the CeO2/ZnO heterostructure. The photocatalytic performance of CeO2, ZnO and CeO2/ZnO heterostructure was evaluated and it was found that CeO2/ZnO heterostructure with a Zn/Ce ratio of 0.2 exhibited the highest photocatalytic activity, where the degradation efficiency was 99.28 % after irradiation for 60 min. It was mainly ascribed to the heterojunction structure of the CeO2/ZnO nanocomposite, leading to a higher separation efficiency of electron-hole pairs and generating more superoxide radicals, which in turn improved the photocatalytic activity effectively.

Strain engineered structural, mechanical and electronic properties of monolayer phosphorene: A DFT study

Role of strain in engineering structural, mechanical and electronic properties and their anisotropy in monolayer phosphorene has been investigated using density functional calculations. The in-plane Youngs's modulus, estimated as 102.45 N/m and 23.43 N/m along zigzag and armchair directions, respectively confirms substantial elastic anisotropy. Phosphorene is also verified as a super flexible material which can withstand a tensile strain up to 35 % (70 %) along zigzag (armchair) direction. Furthermore, band gap (Eg) engineering, band dispersion mechanism, multiple direct-to-indirect band gap transition, semiconductor-to-metal transition, anisotropy in carrier effective mass in phosphorene due to application of strain has been comprehensively investigated and explained. It is predicted that, Eg of phosphorene can be widely tuned in the range, 0–1.12 eV by applying compressive and tensile strains. The observed super flexible nature, wide tunable electronic properties and their anisotropy recommends phosphorene a preferred material for designing flexible optoelectronic devices with directional selectivity.

Tunable electronic and optical properties of BAs/InS heterojunction based on first-principles calculations.

The geometric structure, electronic properties, and optical characteristics of BAs/InS heterostructures are investigated in the present study through the first-principles calculations of Density Functional Theory. The analysis shows that H1-stacking BAs/InS heterostructures with an interlayer distance of 3.6 Å have excellent stability compared with monolayer materials. Furthermore, this heterostructure is classified as a Type-II heterostructure, which promotes the formation of photo-generated electron-hole pairs. The band alignment, direction and magnitude of electronic transfer in BAs/InS heterostructures can be fine-tuned by applying the external electric field and stress, which can also induce a transition from Type-II to Type-I behavior, the indirect bandgap to direct bandgap also occurs. Moreover, absorption coefficient of the heterostructure can also be moderately enhanced and adjusted by external electric fields and stress. These findings suggest that BAs/InS heterostructures have potential applications in photoelectric detectors and laser technology.

A New CuI/Oxalamide Catalytic System for the Large‐Scale Aerobic Oxidation of Alcohols

AbstractSince the report of oxamide ligands, they have been widely used for the efficient construction of various types of C−X (such as C, N, O and S) bonds. To evaluate whether the easily tunable electronic properties and unique coordination modes of oxamide ligands can also shine in the field of oxidation, we initiated a study on oxamide ligand/copper/air oxidation and applied it to the oxidation of alcohols to assess its practicality and potential applications. The practicality of this strategy was further verified through scale‐up reactions on a 100 mmol scale and gram‐scale derivatization of pharmaceutical molecules.

Tunable Electronic and Optical Properties of Al- and Fe-Doped Lizardite/h-BN Heterostructures.

Recent advancements in the chemical substitution of clay minerals have yielded promising results in the development of innovative materials. The utilization of the serpentine mineral lizardite holds significance not only due to its abundance in nature but also for its environmentally friendly characteristics. A comprehensive investigation of a lizardite/h-BN van der Waals heterostructure in the presence of impurities has been conducted. Formation energy calculations for the 12 possible heterostructures demonstrate the chemical stability of all configurations. The analysis of energy bands and density of states reveals the altered electronic properties of the system attributed to impurities. Substituting Al for Mg and Si induces a transition to a metallic state, whereas characteristics due to Fe substitution depend on its position. Substituting Fe for Mg results in a metallic nature, while substitution for Si maintains semiconducting behavior with a reduced band gap compared to the pristine case. Furthermore, the modified optical properties of the heterostructures broaden the potential applications of h-BN and the clay mineral, leading to significant advancements in optoelectronic and field-effect devices.

The tunable electronic and optical properties of WS2/PtO2 heterojunctions are calculated by first principles

In this paper, the optical and electrical characteristics of WS2/PtO2 heterojunction are calculated by first principles method. The results show that WS2/PtO2 heterojunction is a semiconductor heterojunction with an indirect bandgap of 0.7 eV and a Type-Ⅱ band distribution, which can achieve rapid division and transport of photogenerated carriers. Its narrow band gap has a unique electronic structure and tunability, which shows great application potential in high-performance optoelectronic devices and solar cells. When we apply biaxial strain and electric field, the WS2/PtO2 heterojunction has semiconductor–metal transition. This transformation can be used in electronic devices to regulate the carrier concentration and transport characteristics in electronic devices. It also shows excellent properties in optics. The above shows that the stable structure and tunable electronic properties make WS2/PtO2 heterojunctions hold significant promise for future optoelectronic devices and other applications.

Nanocomposite superstructure of zinc oxide mesocrystal/reduced graphene oxide with effective photoconductivity

Metal oxide mesocrystals are the alignment of metal oxide nanoparticles building blocks into the ordered superstructure, which have potentially tunable optical, electronic, and electrical properties suitable for practical applications. Herein, we report an effective method for synthesizing mesocrystal zinc oxide nanorods (ZnONRs). The crystal, surface, and internal structures of the zinc oxide mesocrystals were fully characterized. Mesocrystal zinc oxide nanorods/reduced graphene oxide (ZnONRs/rGO) nanocomposite superstructure were synthesized also using the hydrothermal method. The crystal, surface, chemical, and internal structures of the ZnONRs/rGO nanocomposite superstructure were also fully characterized. The optical absorption coefficient, bandgap energy, band structure, and electrical conductivity of the ZnONRs/rGO nanocomposite superstructure were investigated to understand its optoelectronic and electrical properties. Finally, the photoconductivity of the ZnONRs/rGO nanocomposite superstructure was explored to find the possibilities of using this nanocomposite superstructure for ultraviolet (UV) photodetection applications. Finally, we concluded that the ZnONRs/rGO nanocomposite superstructure has high UV sensitivity and is suitable for UV detector applications.

Ultrathin Copper Monosulfide Films for an Optically Semitransparent, Highly Selective Ammonia Chemosensor.

Transition-metal sulfides are emerging as promising materials for chemiresistive gas sensors─a field still dominated by semiconducting metal oxides. Despite the availability of materials with tunable electronic, optical, physical, and chemical properties, few studies have moved beyond synthesis to provide strategies for enhancing gas sensing performance through material modification. Here, we present a simple, scalable synthetic strategy for developing an optically semitransparent, flexible NH3 gas sensor with a highly uniform, ultrathin CuS (covellite) active sensing layer. The optical and chemical properties of the CuS were precisely controlled near the percolation threshold of thin-film formation by varying key experimental parameters such as the Cu film thickness (<10 nm) and the sulfurization time (∼90 s) under ambient conditions. Experimental and computational studies of CuS and its NH3 sensing characteristics identify key physicochemical properties. The controlled surface chemistry and morphology of the ultrathin CuS layer demonstrate its effectiveness in functional NH3 sensing devices, which achieve a calculated detection limit of 1.38 ppm for NH3 gas at 150 °C, along with exceptional mechanical robustness and optical semitransparency in the visible-light spectrum.

Strain effect on the electronic and optical characteristics of FAGeX3 (X=Cl, Br, and I) perovskite materials: DFT analysis

This study investigates the electronic and optical properties of a perovskite material known as Formamidinium Germanium Halide (FAGeX3), where X represents the elements Chlorine (Cl), Bromine (Br), and Iodine (I). We explore the bandgap, density of state (DOS), and partial density of state (PDOS) to understand their electronic properties. We use two methods, PBE and HSE-06, to determine the bandgap. Further, we investigate the optical properties by investigating the real and imaginary functions of the dielectric constant, refractive index, electron energy loss function, and absorption coefficient. Our research extends to the impact of biaxial strain, both tensile and compressive, in the −6% to +6 % range. Without strain, the materials exhibit direct bandgaps at the R point, with FAGeCl3 showing the highest bandgap (2.1359 eV), followed by FAGeBr3 (1.7325 eV), and FAGeI3 with the lowest (1.2581 eV). Our results reveal that applying tensile strain increases the bandgap and induces a blueshift, shifting the optical responses to shorter wavelengths, while compressive strain reduces the bandgap and causes a redshift, enhancing longer wavelength responses. Our findings demonstrate that FAGeX3 perovskites exhibit highly tunable electronic and optical properties under strain, making them exceptional candidates for advanced optoelectronic applications.

Carbon dot-based type I photosensitizers for photocatalytic oxidation reaction of arylboric acid and N-phenyl tetrahydroisoquinoline

Carbon dots (CDs) have emerged as promising materials for photocatalytic organic transformations due to their excellent photostability, tunable electronic properties, and environmental friendliness; However, the ability of CDs to selectively generate reactive oxygen species (ROS) and its integration with organic photocatalytic synthesis applications has always been a long-term challenge. In this work, we synthesized a new nitrogen and phosphorus co-doped carbon dots (N,P-CDs) with enhanced light absorption and notable efficiency in generating superoxide anion (O2•−) selectively. Leveraging the selective generation of superoxide anions, we achieved highly efficient photooxidation of boronic acids and N-phenyl tetrahydroisoquinolines, demonstrating the practical applicability of N,P-CDs as photocatalysts and represents good functional-group tolerance as well as a broad substrate scope. This study provides valuable insights into the design of carbon-based photocatalysts with controlled ROS generation, opening new avenues for environmentally benign organic transformations.

Tuning Optical and Electrical Properties of Vanadium Oxide with Topochemical Reduction and Substitutional Tin.

Vanadium oxides are widely tunable materials, with many thermodynamically stable phases suitable for applications spanning catalysis to neuromorphic computing. The stability of vanadium in a range of oxidation states enables mixed-valence polymorphs of kinetically accessible metastable materials. Low-temperature synthetic routes to, and the properties of, these metastable materials are poorly understood and may unlock new optoelectronic and magnetic functionalities for expanded applications. In this work, we demonstrate topochemical reduction of α-V2O5 to produce metastable vanadium oxide phases with tunable oxygen vacancies (>6%) and simultaneous substitutional tin incorporation (>3.5%). The chemistry is carried out at low temperature (65 °C) with solution-phase SnCl2, where Sn2+ is oxidized to Sn4+ as V5+ sites are reduced to V4+ during oxygen vacancy formation. Despite high oxygen vacancy and tin concentrations, the transformations are topochemical in that the symmetry of the parent crystal remains intact, although the unit cell expands. Band structure calculations show that these vacancies contribute electrons to the lattice, whereas substitutional tin contributes holes, yielding a compensation doping effect and control over the electronic properties. The SnCl2 redox chemistry is effective on both solution-processed V2O5 nanoparticle inks and mesoporous films cast from untreated inks, enabling versatile routes toward functional films with tunable optical and electronic properties. The electrical conductance rises concomitantly with the SnCl2 concentration and treatment time, indicating a net increase in density of free electrons in the host lattice. This work provides a valuable demonstration of kinetic tailoring of electronic properties of vanadium-oxygen systems through top-down chemical manipulation from known thermodynamic phases.

Prediction of crystal structure, phase group, and stability of 2D materials through data science coupled with DFT

Two-dimensional materials offer unique mechanical strength, electrical conductivity, and tunable electronic properties, driving advancements in electronics, energy storage, and catalysis. The crystal structure of the materials is fundamental to several properties. In this study, we employ solely the elemental features to construct a random forest classification model achieving an 82.56 % accuracy in predicting the crystal structure of the compounds. Additionally, one vs rest binary classifiers are developed for each crystal structure within our 2D materials dataset, with accuracies ranging from 86 % to 99 %, enhancing their practical utility. Features based on stoichiometric norms have been found to play a major role in the prediction because of the fact that certain crystal structures are associated with more balanced compositions, leading to lower norm values, while others with imbalances have higher norm values. It has also been observed that material compositions with an overall higher amount of p valence electrons tend to show monoclinic, orthorhombic and triclinic crystal structures. Moreover, in compounds with a lower total electronegativity of the constituent elements, the occurrence of trigonal and tetragonal systems has been found to be more probable. In a similar fashion, hexagonal crystal systems have been more often found in compounds where the sum of Van Der Waals radius of the constituent atoms is lower. To validate our model, Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method, and Density Functional Theory (DFT) are utilized to predict the crystal structure, phase group, and stability of a 2D material.

Half-metallic behavior and anisotropy of two-dimensional MoSi2N4/ScSi2N4 heterojunction

Heterojunctions formed by stacking different two-dimensional monolayer materials typically have tunable electronic properties, which will greatly broaden the application prospects of 2D materials in electron devices. In this paper, the structures, electron properties, and anisotropy of MoSi2N4/ScSi2N4 heterojunctions formed by stacking MoSi2N4 monolayer with semiconductor properties and ScSi2N4 monolayer with half-metallic properties have been systematically studied. The results show that Type-Ⅰ configuration has the most stable structure in terms of total energy, binding energy, phonon spectrum and molecular dynamics among the three configurations formed by MoSi2N4/ScSi2N4 heterojunctions. The MoSi2N4/ScSi2N4 heterojunction has robust half-metallic behavior and tensile anisotropy at equilibrium. At the same time, MoSi2N4/ScSi2N4 heterojunction can still maintain stable ferromagnetic and half-metallic properties under large interlayer distance changes. Studies of magnetic anisotropy show that the direction of hard axis for MoSi2N4/ScSi2N4 heterojunction is perpendicular to the 2D layer plane. The tunable properties of MoSi2N4/ScSi2N4 heterojunction provides promising exploration for novel 2D materials.

Boron interaction with double-walled carbon nanotubes across temperature ranges

Boron-adsorbing carbon nanotubes receive considerable attention in materials science due to their unique properties and potential applications. In particular, boron-adsorbing double-walled carbon nanotubes (DWNTs) exhibit a wide range of tunable electronic and optoelectronic properties. This study explores the influence of boron atoms on metallic (5,5@10,10) and semiconducting (8,0@17,0) DWNTs. We examine alterations in partial charge depending on the quantity of boron atoms adsorbed and affixed to the DWNT surface across temperatures from 300 K to 900 K. The results show that in both DWNTs, with the increase of energy corresponding to the temperature, the adsorption index of boron atoms (adsorbed to the first layer of DWNT) and the positive partial charge increase. Specifically, the maximum partial charge of DWNT(8,0)@(17,0) and DWNT(5,5)@(10,10) is 1.94e and 1.30e (at 300 K), 4.87e and 3.66e (at 600 K), 6.97e and 6.16e (at 900 K). Increasing boron concentration leads to heightened positive partial charge of DWNTs. This, in turn, affects the conductivity of the nanotube.