Typical Semiconducting Research Articles

Synergetic Effect and Phase Engineering by Formation of Ti3C2Tx Modified 2H/1T-MoSe2 Composites for Enhanced HER

The typical semi conductivity and few active sites of hydrogen evolution of 2H MoSe2 severely restrict its electrocatalytic hydrogen evolution performance. At the same time, the 1T MoSe2 has metal conductivity and plentiful hydrogen evolution sites, making it feasible to optimize the electrocatalytic hydrogen evolution behavior of MoSe2 using phase engineering. In this study, we, through a simple one-step hydrothermal method, composed 1T/2H MoSe2, and then used newly emerging transition metal carbides with several atomic-layer thicknesses Ti3C2Tx to improve the conductivity of a MoSe2-based electrocatalyst. Finally, MoSe2@Ti3C2Tx was successfully synthesized, according to the control of the additional amount of Ti3C2Tx, to form a proper MoSe2/ Ti3C2Tx heterostructure with a better electrochemical HER performance. As obtained MoSe2@4 mg-Ti3C2Tx achieved a low overpotential, a small Tafel slope and this work offers additional insight into broadened MoSe2 and MXenes-based catalyst’s electrochemical application.

First-principles LCPAO approach for insulators under finite electric fields with forces

We propose a linear-combination-of-pseudo-atomic-orbitals scheme for a finite electric field method based on the modern theory of polarization. We derive the matrix elements of the effective potential for the static and homogeneous field and the corresponding terms of the forces on atoms. In addition, we successfully evaluated the static and electronic dielectric constants and Born effective charges of typical semiconducting and insulating materials. Our formalism will aid in the study of materials under electric fields.

A hydrophobic semiconducting metal-organic framework assembled from silver chalcogenide wires.

Silver chalcogenide wires are assembled for the first time using a linear fluorinated carboxylate ligand into a metal-organic framework (MOF) with multifunctional properties. Fluorinated ligands in the host framework endow the MOF with excellent hydrophobicity. More interestingly, it displays typical semiconductivity due to the ordered nanoarray of non-discrete helical (-Ag-S-)n chains.

Perylene bisimide metal complexes as new MWCNTs dispersants: Role of the metal ion in stability and temperature sensing

We report on new dispersants based on metal complexes of an extended polycylic aromatic perylene bisimides (PeryC_M), suitable for the exfoliation of MWCNTs. The formal 1:1 metal complexes provided well-disentangled and undamaged MWCNTs and with a content at least 35wt.% higher than that given by the bare ligand. The ionic charges at the periphery of PeryC_M endowed the π−conjugated perylene core with electrostatic repulsions, thus enhancing MWCNTs dispersibility. MWCNT-based mixtures displayed electrical resistance depending on the MWCNTs content and a typical semiconducting (activated) electrical transport with decreased resistance when heated within the physiological temperature range, i.e. from 20 to 40°C. While perypheral charges are meaningful for MWCNTs deboundling and stabilization, they do not play any significant role in determining resistance sensitivity to temperature variations within the physiological regime. A negative temperature coefficient of about 10−2K−1 and comparable to that of common thermistors was found for the investigated sensors.

Density functional theories study on optoelectronic properties of arsenic-doped GaN nanowires

The electronic and optical properties of As-doped GaN nanowires have been investigated using density functional theory. The energy gaps of As-doped GaN nanowires with different concentrations exhibit indirect band gaps, and the band gaps are decreasing with the increasing doping concentration. The results predicate that alloys exhibit a typical semiconductivity. Moreover, the optical properties, including the complex dielectric function, optical refractive index, energy-loss function, reflectivity, and absorption coefficient are discussed for radiation up to 30 eV. With the increase of the As-fraction, the material gradually exhibits noticeable anisotropy in the photon energy range of 0–15 eV. Quickly increases the static dielectric constant and obviously red-shifts the absorption edge. The results are in good agreement with experimental data reported previously. Furthermore, the work gives a theoretical guidance for the preparation of As-doped GaN optoelectronic nanodevices.

Semiconductive Nanotube Array Constructed from Giant [Pb(II)18I54(I2)9] Wheel Clusters.

Crystalline nanotube array would create great opportunity for novel electrical application. Herein we report the first example of a metal halide based crystalline nanotube array which is constructed from an unprecedented giant [Pb(II)18I54(I2)9] wheel cluster, as determined by synchrotron X-ray diffraction. The electrical properties of the single crystal were studied and the present compound shows typical semiconductivity and highly anisotropic conductivity.

Semiconductive Nanotube Array Constructed from Giant [PbII18I54(I2)9] Wheel Clusters

AbstractCrystalline nanotube array would create great opportunity for novel electrical application. Herein we report the first example of a metal halide based crystalline nanotube array which is constructed from an unprecedented giant [PbII18I54(I2)9] wheel cluster, as determined by synchrotron X‐ray diffraction. The electrical properties of the single crystal were studied and the present compound shows typical semiconductivity and highly anisotropic conductivity.

Electronics and Structural Properties of Single-Walled Carbon Nanotubes Interacting with a Glucose Molecule: ab initio Calculations

The adsorption of glucose molecule on single-walled carbon nanotubes (SWCNTs) is investigated by density functional theory calculations. Adsorption energies and equilibrium distances are evaluated, and glucose binding to the typical semiconducting and metallic nanotubes with various diameters and chirality are compared. We also investigated the role of the structural defects on the adsorption capability of the SWCNTs. We could observe larger adsorption energies for the larger diameters semiconducting CNTs, while the story is paradoxical for the metallic CNTs. The obtained results reveal that the adsorption energy is significantly higher for nanotubes with higher chiral angles. Finally, the adsorption energies are calculated for defected nanotubes for various configurations such as glucose molecule approaching to the pentagon, hexagon, and heptagon sites in the tube surface. We find that the respected defects have a minor contribution to the adsorption mechanism of the glucose on SWNTs. The calculation of electron transfers and the density of states supports that the electronic properties of SWCNTs do not change significantly after the gluycose molecular adsorption. Consequently, one can predict that presence of glucose would neither modify the electronic structure of the SWCNTs nor direct to a change in the conductivity of the intrinsic nanotubes.

Visible‐Light‐Responsive β‐Rhombohedral Boron Photocatalysts

Photocatalytic solar-energy conversion has been attracting worldwide attention owing to its great significance in the provision of renewable energy and protection of the environment. As important as the tailoring of well-known photocatalysts, such as TiO2, for high photocatalytic efficiency [4–7] is the investigation of unknown semiconductor photocatalysts. So far, hundreds of photocatalysts have been examined, most of which have been compounds. Recently, elemental semiconductors (Si, Se, P, S) have emerged as an attractive class of photocatalysts owing to their visible-light response and suitable band edges for targeted photocatalysis reactions. It is logical to also anticipate the use of elemental boron in photocatalysis because of its semiconducting properties. When we investigated b-rhombohedral boron crystals with and without an amorphous oxide layer on their surface, we discovered that the crystals were indeed photocatalytically active under visible light, and that the existence of a surface amorphous oxide layer substantially impaired their photocatalytic activity. The findings in this study may open a door to the development boron-based photocatalysts. Boron has aroused wide interest owing to its fascinating properties (light weight, high strength, high hardness, high melting point, high chemical resistance, typical semiconductivity, and superconductivity at high pressure), although a pure phase was not obtained until 1909. It has at least 17 polymorphs (or more precisely, boron-rich compounds) as a result of electron-deficient bonding. All polymorphs contain B12 icosahedral clusters as a basic building block (see the inset in Figure 1a). Among these polymorphs, a-tetragonal, a-rhombohedral, b-tetragonal, and b-rhombohedral boron are the four main forms under ambient conditions. Experimentally, b-rhombohedral boron is the most thermodynamically stable form, although its superior stability was not supported by theoretical investigations until 2007. This long-term discrepancy stems from the difference between the idealized structural model of 105 boron atoms (B105) that is used to describe the b-rhombohedral form and the real structure, which contains partially occupied sites. As a consequence, the theoretically predicted metallic property does not agree with the experimentally derived p-type semiconducting behavior of b-rhombohedral boron with a proposed bandgap of 1.5–1.6 eV. Improved crystallographic studies and optimized theoretical structure models have reduced the gap between experiment and theory to some extent and provided a strong background for the further investigation of structure–property relationships and the exploration of new uses for b-rhombohedral boron. The bandgap of 1.5–1.6 eV indicates that b-rhombohedral boron should respond to visible light over a wide range of wavelengths. It was also found in quasi-four-electrode measurements that b-rhombohedral boron exhibited strong photoconductivity under illumination by a halogen lamp or argonion laser (at 488 nm). Encouraged by these favorable properties, we investigated the photocatalytic activity of two kinds of commercially available b-rhombohedral boron crystals (sub-micrometer-sized and micrometer-sized) by structural characterization, measurement of their optical properties, and theoretical calculation of their electronic structures. Figure 1a shows the X-ray diffraction (XRD) pattern of sub-micrometer-sized boron powder. All diffraction peaks can be assigned to b-rhombohedral boron (JCPDS: 11-0618; space group: R 3m (166); a= 10.952 , c= 23.824 ). Besides the sharp peaks, there are several diffuse peaks in the background, which indicate the existence of amorphous Figure 1. Structure characterization: a) XRD pattern of sub-micrometer-sized b-rhombohedral boron. b) High-resolution TEM image recorded at the edge of a sub-micrometer-sized b-rhombohedral boron particle. The inset in (a) shows the structure of an icosahedral B12 cluster.

On the encapsulation of azafullerenes inside the single-walled carbon nanotubes: Density-functional theory based treatments

We theoretically studied the encapsulation of azafullerene (C 59N) inside the single-walled carbon nanotubes (SWCNTs) from the first-principles. Adsorption energy is calculated, and the azafullerene affinities for the typical semiconducting and metallic nanotubes are investigated and compared with those of pure C 60 fullerene. It has been found that the azafullerene as well as the fullerene affinity for the semiconducting nanotubes is stronger than that for the metallic ones, and the energy values and binding distances are typical for the physisorption. Our first-principles results indicate that the interaction between SWCNTs and azafullerenes is comparable with the nanotubes–C 60 system. The charge analysis shows, however, that the charges have been transferred from the cage to the tube in the azafullerene peapods, while in the fullerene peapods the charges were found to be transferred from the tube to the fullerene nanocage. Furthermore, it was found that the interaction between the considered fullerenes and host nanotubes strongly depends on the tube diameters.

Synthesis, structure and conductivity of molecular conductor β-(BEDT-TTF)(HSO 4)

A new BEDT-TTF-based radical salt, β-(BEDT-TTF)(HSO 4) [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene], has been synthesized by oxidative electrocrystallization. The crystal structure was determined by four-circle X-ray diffraction. The crystal belongs to monoclinic system, C2/c space group with the unit cell parameters of: a = 1.5996(2) nm, b = 1.06173(10) nm, c = 1.15083(11) nm, β = 120.534(8)°, V = 1.6834(3) nm 3, and R = 0.0611. In the title crystal, the BEDT-TTF radicals are stacked to form columns along the [1 0 1] axis and the molecular planes of BEDT-TTFs in adjacent columns are parallel to each other. The inter-stack side-by-side S…S short contacts along the b-axis help to form a kind of cationic conducting sheet parallel to (1 0 1) plane. The room temperature conductivity at certain direction on (1 0 1) plane of β-(BEDT-TTF)(HSO 4) single crystal was measured to be 11.7 S cm −1. From 100 K to 290 K, the resistivity–temperature curve demonstrates its typical semiconductivity with an excitation energy of 0.26 eV.

Interaction of Methane with Single-Walled Carbon Nanotubes: Role of Defects, Curvature and Nanotubes Type

We investigate the interaction of single-walled carbon nanotubes (SWCNTs) and methane molecule from the first principles. Adsorption energies are calculated, and methane affinities for the typical semiconducting and metallic nanotubes are compared. We also discuss role of the structural defects and nanotube curvature on the adsorption capability of the SWCNTs. We could observe larger adsorption energies for the metallic CNTs in comparison with the semiconducting CNTs. The obtained results for the zig zag nanotubes with various diameters reveal that the adsorption energy is higher for nanotubes with larger diameters. For defected tubes the adsorption energies are calculated for various configurations such as methane molecule approaching to the defect sites pentagon, hexagon, and heptagon in the tube surface. The results show that the introduce defects have an important contribution to the adsorption mechanism of the methane on SWNTs.

Interaction of single-walled carbon nanotubes with alkylamines: An ab initio study

We study the interaction of single-walled carbon nanotubes and organic amines with sizable alkyl groups from the first principles. Adsorption energy is calculated, and amine affinities for the typical semiconducting and metallic nanotubes are compared. We discuss role of the amine in nanotube debundling. Our results support the idea of using alkylamines as nanotube purifying agents in addition to ultrasonic treatment.

Synthesis and Properties of Polyacetylene

Abstract This paper presents an introductory review on synthesis and properties of polyacetylene, a typical semiconducting and conducting organic polymer. Electrical conductivity of polyacetylene can be tailored by an appropriate chemical and/or electrochemical doping with electron accepting or electron donating reagents, spanning the range of insulators (10−12 S/cm) and metals (105 S/cm).

(Invited) Polyacetylene: A Typical Semiconducting and Metallic Polymer

This paper presents an introductory review of polyacetylene, a typical semiconducting and metallic organic polymer. The electrical conductivity of polyacetylene can be tailored by appropriate “chemical and/or electrochemical doping” with electron accepting or electon donating reagents, spanning the range of insulators (10-12 S/cm) and metals (103 S/cm). Some of the potential applications of the doped polyacetylene are described.