Arsenic Atoms Research Articles

Dithieno[3,4‐b:3',4'‐d]arsole: A Novel Class of Hetero[5]radialenes

[5]Radialene is known as an unstable cyclic hydrocarbon with a cross‐conjugated system. Incorporation of heteroatoms into [5]radialene skeleton is an effective strategy for stabilization. Herein we synthesized dithieno[3,4‐b:3',4'‐d]arsole (1) as a novel class of hetero[5]radialenes since trivalent arsenic atom is much more stable than phosphorus one, which was used for hetero[5]radialene but unstable in air. The characteristic nature of the arsa[5]radialene was experimentally and computationally studied by comparing with the isomer, dithieno[3,2‐b:2',3'‐d]arsole (2). Structural analysis by X‐ray crystallography and computational evaluation of aromaticity revealed the radialene character of 1. Interestingly, 1 showed phosphorescence though only fluorescence was observed for 2. Time‐dependent density functional theory (TD‐DFT) calculations implied that intersystem crossing could readily occur upon excitation for 1. Furthermore, it was computationally elucidated that dimerization and/or oligomerization via Diels‐Alder reaction, which convert [5]radialene, were circumvented to offer stability for 1.

Adsorption of hazardous atoms on the surface of TON zeolite and bilayer silica: a DFT study

In the present study, the adsorption of two types of hazardous atoms including arsenic and lead with TON zeolite and bilayer silica (2D-SiO2) have been investigated by employing Ab initio-based density functional theory (DFT) calculations. To reach a full structural optimization and the most stable configuration, four sites were considered for TON zeolite as well as five sites for 2D-SiO2, and adsorption energy along with equilibrium geometry was determined. The adsorption energies of arsenic atom on the surface of 2D-SiO2 absorbents and TON zeolite have obtained equal to and - 1.25eV and - 2.76eV, respectively, which both of them are chemisorption type. We also found that the adsorption of lead on the surface of 2D-SiO2 was physisorption type with the adsorption energy accounting for - 0.13eV, while the adsorption energy between lead and TON was calculated equal to - 2.32eV which was chemisorption type. Furthermore, our results demonstrate that the TON zeolite was more capable of adsorbing hazardous atoms compared with 2D-SiO2 due to having greater adsorption energy. The adsorption of arsenic on the 2D-SiO2 and TON adsorbents is also stronger than those of lead atom. Furthermore, we modeled and considered graphene, as a common adsorbent nanostructure, to compare and validate the accuracy of our simulations and obtained results. Finally, the electronic density of states (DOS) calculations and charge analysis were done by the use of Mulliken method, and the results confirmed those results that had already been obtained from adsorption energies. Graphical abstract.

Single-layer Janus black arsenic-phosphorus (b-AsP): Optical dichroism, anisotropic vibrational, thermal, and elastic properties

By using density functional theory (DFT) calculations, we predict a puckered, dynamically stable Janus single-layer black arsenic-phosphorus (b-AsP), which is composed of two different atomic sublayers, arsenic and phosphorus atoms. The calculated phonon spectrum reveals that Janus single-layer b-AsP is dynamically stable with either pure or coupled optical phonon branches arising from As and P atoms. The calculated Raman spectrum indicates that due to the relatively strong P-P bonds, As atoms have no contribution to the high-frequency optical vibrations. In addition, the orientation-dependent isovolume heat capacity reveals anisotropic contributions of LA and TA phonon branches to the low-temperature thermal properties. Unlike pristine single layers of b-As and b-P, Janus single-layer b-AsP exhibits additional out-of-plane asymmetry which leads to important consequences for its electronic, optical, and elastic properties. In contrast to single-layer b-As, Janus single-layer b-AsP is found to possess a direct band gap dominated by the P atoms. Moreover, real and imaginary parts of the dynamical dielectric function, including excitonic effects, reveal the highly anisotropic optical feature of the Janus single-layer. A tight-binding (TB) model is also presented for Janus single-layer b-AsP, and it is shown that, with up to seven nearest hoppings, the TB model reproduces well the DFT band structure in the low-energy region around the band gap. This TB model can be used in combination with the Green's function approach to study, e.g., quantum transport in finite systems based on Janus single-layer b-AsP. Furthermore, the linear-elastic properties of Janus single-layer b-AsP are investigated, and the orientation-dependent in-plane stiffness and Poisson ratio are calculated. It is found that the Janus single layer exhibits strong in-plane anisotropy in its Poisson ratio much larger than that of single-layer b-P. This Janus single layer is relevant for promising applications in optical dichroism and anisotropic nanoelasticity.

Atomic-Scale Patterning of Arsenic in Silicon by Scanning Tunneling Microscopy.

Over the past two decades, prototype devices for future classical and quantum computing technologies have been fabricated by using scanning tunneling microscopy and hydrogen resist lithography to position phosphorus atoms in silicon with atomic-scale precision. Despite these successes, phosphine remains the only donor precursor molecule to have been demonstrated as compatible with the hydrogen resist lithography technique. The potential benefits of atomic-scale placement of alternative dopant species have, until now, remained unexplored. In this work, we demonstrate the successful fabrication of atomic-scale structures of arsenic-in-silicon. Using a scanning tunneling microscope tip, we pattern a monolayer hydrogen mask to selectively place arsenic atoms on the Si(001) surface using arsine as the precursor molecule. We fully elucidate the surface chemistry and reaction pathways of arsine on Si(001), revealing significant differences to phosphine. We explain how these differences result in enhanced surface immobilization and in-plane confinement of arsenic compared to phosphorus, and a dose-rate independent arsenic saturation density of 0.24 ± 0.04 monolayers. We demonstrate the successful encapsulation of arsenic delta-layers using silicon molecular beam epitaxy, and find electrical characteristics that are competitive with equivalent structures fabricated with phosphorus. Arsenic delta-layers are also found to offer confinement as good as similarly prepared phosphorus layers, while still retaining >80% carrier activation and sheet resistances of <2 kΩ/square. These excellent characteristics of arsenic represent opportunities to enhance existing capabilities of atomic-scale fabrication of dopant structures in silicon, and may be important for three-dimensional devices, where vertical control of the position of device components is critical.

Identification of Degradation Products of Sea-Dumped Chemical Warfare Agent-Related Phenylarsenic Chemicals in Marine Sediment.

Previously unknown phenylarsenic chemicals that originated from chemical warfare agents (CWAs) have been detected and identified in sediment samples collected from the vicinity of chemical munition dumpsites. Nontargeted screening by ultrahigh-performance liquid chromatography–high-resolution mass spectrometry (UHPLC-HRMS) was used for detection of 14 unknown CWA-related phenylarsenic chemicals. Methylated forms of Clark I/II, Adamsite, and phenyldichloroarsine were detected in all analyzed sediment samples, and their identification was based on synthesized chemicals. In addition, other previously unknown CWA-related phenylarsenic chemicals were detected, and their structures were elucidated using MS/HRMS technique. On the basis of relative isotope ratios of protonated molecules and measures of exact masses of formed fragment ions, it could be concluded that some of these unknown chemicals contained a sulfur atom attached to an arsenic atom. In addition to that, some of the samples contained chemicals that had formed via addition of an OH group to the aromatic ring. However, it is not possible to say how these chemicals are formed, but the most plausible cause is activities of marine microbes in the sediment. To our knowledge, these chemicals have not been detected from sediment samples previously. Sensitive analytical methods are needed for these novel chemicals to assess the total CWA burden in marine sediments, and this information is essential for the risk assessment.

Investigation of the shear relaxation behavior of As-Se liquids within the framework of entropic and elastic models of viscous flow

The shear relaxation behavior of supercooled arsenic selenide liquids is studied using small amplitude oscillatory parallel plate rheometry. Compositions with >80% Se, characterized by a low-dimensional network of selenium chain segments cross-linked by threefold coordinated arsenic atoms, display the coexistence of a nearly-Arrhenius, slow relaxation process and a strongly non-Arrhenius, fast relaxation process corresponding to bond scission/renewal and chain segmental motion, respectively. The coupling between the weakly non-Arrhenius bond scission and the strongly non-Arrhenius viscosity is achieved near Tg due to the pronounced temperature-dependence of the modulus corresponding to this relaxation process. The temperature dependence of this relaxation modulus is related to the conformational entropy of the chain segments. The large difference between the activation energy of viscous flow and that of the timescale of the relaxation associated with bond scission/renewal implies the need for a revision of the existing models of viscous flow in the literature.

Arsenic(III) complexes of substituted diphenyldithiophosphate: synthesis, characterization, single crystal X-ray, DFT, and Hirshfeld surface analysis

Reaction of the triethylammonium salt of the substituted diphenyldithiophosphate ligands with AsCl3 in a 3:1 ratio results in the formation of the arsenic complexes As[S2P{OC6H4(4-C2H5)}2]3 (1), As[S2P{OC6H4(4-(CH3)3C)}2]3 (2), As[S2P{OC6H3(2,4-CH3)2}2]3 (3), As[S2P{OC6H3(2,5-CH3)2}2]3 (4), As[S2P{OC6H3(3,4-CH3)2}2]3 (5), and As[S2P{OC6H3(3,5-CH3)2}2]3 (6). The characterization of all the synthesized complexes was done by IR and multinuclear NMR (1H, 13C, and 31P) spectroscopies. Complexes 1 and 2 were structurally elucidated by single-crystal X-ray analysis. The X-ray data reveals that 1 and 2 were crystallized in triclinic crystal system with space group P −1 and monoclinic crystal system with space group C2/c, respectively. In 1 and 2, the coordination geometry around the central arsenic atom is pseudo-trigonally distorted octahedral with a lone pair of electrons positioned on one of the triangular faces of the octahedral. The central As atom in both complexes is surrounded by six sulfur atoms of the chelating anisobidentate ligands. The density functional theory computations are also carried out to further analyze the geometry and quantum chemical parameters in order to support the experimental and structural data. Finally, to estimate the effect of alkyl steric bulk in diphenyldithiophosphate complexes 1 and 2 on the intermolecular contacts contributions to the Hirshfeld surface analysis and 2-D finger-print plots analysis have been employed.

Infrared Photodissociation Spectroscopy of Heteronuclear Arsenic-Iron Carbonyl Cluster Anions.

Heteronuclear arsenic-iron carbonyl cluster anions AsmFe(CO)n- (m, n = 2, 3) have been generated in the gas phase and investigated by mass-selected infrared photodissociation spectroscopy and density functional theory calculations at the B3LYP/BP86/TPSS levels. All the AsmFe(CO)n- (m, n = 2, 3) cluster anions are determined to contain Fe(CO)n- fragments, which can be regarded as being formed by replacing one arsenic atom of the arsenic clusters Asm+1 with the Fe(CO)n- group. Bonding analyses indicated that each As2Fe(CO)n- (n = 2, 3) cluster anion involves two Fe-As single bonds and one As-As double bond. Each As3Fe(CO)n- (n = 2, 3) cluster anion has three Fe-As single bonds and three As-As single bonds. The Fe(CO)3- group with a 15-electron configuration is valence isoelectronic to the As atom and can serve as a building block for forming heteronuclear arsenic-iron carbonyl clusters.

Highly Efficient Silicon Photonic Microheater Based on Black Arsenic–Phosphorus

AbstractWhile black phosphorus has shown excellent optoelectronic properties in many aspects, the environmental instability ultimately places limits on its practical applications. Black arsenic–phosphorus (b‐AsP), an alloy of black phosphorus with arsenic atoms, has emerged as a new 2D material with better stability. Recently, the heterostructure via integration of 2D material with nanophotonic waveguides is opening an avenue for many on‐chip applications of phosphorene. However, the thermo‐optic (TO) properties, which are widely used for waveguide heaters, are not studied on b‐AsP yet. Herein, the TO effects of a b‐AsP/silicon van der Waals heterostructure are first investigated and its application as a transparent waveguide heater is demonstrated. A high efficiency of 0.74 nm mW−1 is achieved with a nonresonant and broadband heater based on 20 nm thick b‐AsP, which eliminates the need for enhancement by cavity‐assisted light–matter interaction, and thus allows for compact footprint, broadband operation, and low latency.

Intriguing minerals: photoinduced solid-state transition of realgar to pararealgar—direct atomic scale observation and visualization

This lecture text is aimed at teaching some insight into phase transitions of minerals. It summarizes the results of a detailed study of the reaction mechanism of photoinduced solid-state transformation of the mineral realgar (α-As4S4) to its distinct polymorph pararealgar by a combination of in situ single-crystal X-ray photodiffraction, Fourier transform infrared spectroscopy, and micro-Raman spectroscopy. The process of transformation takes place in four steps. The initiating photoreaction step requires oxygen and thereby the intermediate uzonite (As4S5) and arsenolite (As2O3) are obtained (step 1). The process continues through a set of cyclic reactions in which the sulfur atom released by the decomposition of As4S5 (step 2) reacts with a molecule of realgar to produce a molecule of pararealgar (step 3), whereupon a sulfur atom is released which continues the process (step 4). The photodiffraction technique provides direct atomic resolution evidence of formation of intermediate As4S5 phase in which half of the realgar molecule retains its envelope-type conformation, while the geometry of the other half is transformed by effective switching of positions of one sulfur and one arsenic atom. The migration (hopping) of sulfur atoms between the molecules of the single crystal of realgar is observed and visualized.

First-principles study on adsorption behavior of as on the kaolinite (001) and (00$$\bar {1}$$) surfaces

The environmental fate and behavior of arsenic (As) is receiving increased attention due to the As pollution all over the world. Kaolinite is a natural mineral resource that can be used for the removal of pollution as adsorbent. First-principles calculations based on density-functional theory was employed to explore the adsorption behavior of arsenic atoms adsorption on the kaolinite (001) and (00$$\bar {1}$$) surface. The one-fold top site was found to be energetically preferred for the kaolinite (001) and (00$$\bar {1}$$) surface, and the adsorption energy of the former is obviously higher than the latter. The coverage dependence of the adsorption energetics was systematically studied for a wide range of coverage Θ [from 0.11 to 1.0 monolayers (ML)]. The adsorption energy of As decreased with increasing coverage, thus indicating the lower stability of surface adsorption due to the repulsion of neighboring As atoms. The coverage has obvious effects on the arsenic adsorption process. Other properties of the As/kaolinite (001) system, including the lattice relaxation and changes of electronic density of states, were also studied and discussed in detail.

A remarkable mixture of germanium with phosphorus and arsenic atoms making stable pentagonal hetero-prisms [M@Ge5E5]+, E = P, As and M = Fe, Ru, Os.

A pentagonal hetero-prismatic structural motif was found for singly transition metal doped M@Ge5E5+ clusters, where the transition metal atom is located at the centre of a (5/5) Ge5E5 prism in which Ge is mixed with either P or As atoms. Structural characterization indicates that each (5/5) Ge5E5 prism is established by joining of two Ge3E2 and Ge2E3 strings in a prismatic fashion rather than two Ge5 and E5 strings. Each string results from a remarkable mixture of Ge and E atoms and contains only one E–E connection due to the fact that Ge–E bonds are much stronger than E–E connections. From the donor–acceptor perspective, the Ge5E5 tube donates electrons to the M center, which behaves as an acceptor. NBO atomic charge and ELI_D analyses demonstrate such electrostatic interactions of the M dopant with a Ge5E5+ tube which likely induce thermodynamic stability for the resulting M@Ge5E5+ cluster. CMO analysis illustrates that the conventional 18 electron count is recovered in the M@Ge5E5+ cations.

Nickel oxide nanoparticles on the surface of the gallium arsenide nanocluster structure

This paper describes how the efficiency of the active element of a solar cell of gallium arsenide (GaAs) is increased by nickel oxide nanoparticles. The simulated structure of a semiconductor GaAs compound with a diamond-like lattice shows how the intersphere space grid is generated based on the face-centered cubic lattice motif. A theoretically determined optimal concentration of nanoparticles on the surface and the corresponding values of the experimental data are shown. Studies of the electronic structure on small GaAs clusters at n = 18 correspond to a minimum value of –19·238 eV and a maximum value of –5·606 eV for the state n = 0, –2·99 eV and 20·232 eV for the state n = 1, –0·693 eV and –0·03 eV for the state n = 2, –0·16 eV and –2·646 × 10–4 eV for the state n = 3, respectively. Peaks in the spectra sequentially observed within these limits coincide with the maximum value of the wave vector. Spectral variations, depending on the size of the interspheric space and the number of ion cores, correlate well with changes in densities. The electron density structure of GaAs has a complex structure. The maximum probability of finding is concentrated near four Ga ions. When approaching the center, the electron density changes in a wave-like fashion with a small maximum in the center. The results of the calculations show that gallium atoms in clusters with a higher binding energy, as a rule, are located on the surface or in the places of atomic edges, since the atoms of the faces are less consistent. Arsenic atoms are located in the center, surrounded by gallium atoms.

Theoretical Investigation of Arsenic and Selenium Species Adsorption Behavior on Different Mineral Adsorbents

CaO and Fe₂O₃ are effective mineral sorbents to inhibit the damage of arsenic and selenium release into the atmospheric environment. Density functional theory was applied to explore the adsorption mechanism of different arsenic and selenium species (atom, hydride, oxide, and chloride) on CaO and Fe₂O₃ surfaces. The effect of the As₄O₆ cluster on the adsorption behavior of CaO and Fe₂O₃ surfaces was also examined. The results show that the O top sites serve as the active sites for arsenic and selenium atom adsorption on the CaO(001) surface. For the Fe₂O₃(001) surface, the adsorption energy of the As atom at the Fe top and O bridge site can reach −381.38 and −439.55 kJ/mol, respectively. The results show that the Fe top site and O bridge site are both effective chemical adsorption sites. CaO and Fe₂O₃ also exhibit a good performance to adsorb atomic arsenic and selenium under the condition of multicoverage. In addition, the interactions between two adsorbents and complex arsenic/selenium species are weakened in different degrees, but still belong to chemical adsorption. The adsorption of the As₄O₆ cluster on the CaO surface is mainly attributed to the interaction between As atoms and O atoms on the CaO surface. The As₄O₆ adsorption on the Fe₂O₃ surface depends on the interaction between O atoms of As₄O₆ and Fe atoms on the Fe₂O₃ surface. However, the interactions can both lead to the formation of more stable arsenate, which contributes to the reduction of detrimental arsenic release.

Massless Dirac fermions in stable two-dimensional carbon-arsenic monolayer

We predict from DFT based electronic structure calculations that a monolayer made up of Carbon and Arsenic atoms, with a chemical composition (CAs3) forms an energetically and dynamically stable system. The optimized geometry of the monolayer is slightly different from the buckled geometric configuration observed for silicene and germanene. The results of electronic structure calculations predict that it is a semi-metal. Interestingly, the electronic band structure of this material possesses a linear dispersion and a Dirac cone at the Fermi level around the high symmetric K point in the reciprocal lattice. Thus, at low energy excitation (up to 105 meV), the charge carriers in this system behave as massless Dirac-Fermions. Detailed analysis of partial density of state suggests that the 2pz orbital of C atoms plays vital role in determining the nature of the states, which has a linear dispersion and hence the Dirac cone, around the Fermi level. Thus, the electronic properties of CAs3 monolayer are similar to those of graphene and other group IV based monolayers. In addition, we have also investigated the influence of mechanical strain on the properties of CAs3 monolayer. The buckled configuration becomes the planar configuration for a tensile strain beyond 18%. Our results indicate that the monolayer possesses linear dispersion in the electronic band structure for a wide range of mechanical strain from -12 to 20%, though the position of Dirac point may not lie exactly at the Fermi level. The linear dispersion disappears for a compressive strain beyond -12% & it is due to the drastic changes in the geometrical environment around C atom. Finally, we wish to point out that CAs3 monolayer belongs to the class of Dirac materials where the behaviour of particles, at low energy excitations, are characterized by the Dirac-like Hamiltonian rather than the Schrodinger Hamiltonian.

Synthesis Method and Investigation of o-, m-, p-Nitrophenylarsonic Acid Properties

The importance of studying arylated arsenic derivatives is conditioned by a number of reasons. In particular, as biologically active substances, they attract attention in terms of their fungicidal activity and stimulating effect on cardiac activity. Besides, they serve as an interesting object for intermolecular interaction study conditioned by the H-bond. Finally, as the main starting products, they are the source of a wide range of arsenic-organic compound synthesis, including aromatic primary, secondary arsinghalides, tertiary asymmetric arsines and their derivatives. The aim of the present work was to study the possibility of diazonium salt use obtained from weakly basic arylamines in a strongly acidic medium for arylation of arsinic acid sodium salt. This article discusses the methods for the synthesis of arylated arsenic derivatives containing the substituents in the benzene ring that affect the electronic structure, reactivity, and biological properties of the compounds. They studied the ability of an arsenic atom to transit from a four-coordinate state to a five-coordinate state with the formation of strong monohydrates. They showed the disadvantages and positive aspects of the already known and used synthesis methods. The most practical version of arylated arsenic compound synthesis has been tested and recommended.

Computational study of GanAsm (m + n = 2–9) clusters using DFT calculations

Gallium arsenide is a semiconductor compound with well-known properties in its bulk phase. Theoretical works explain some of the properties of this material at a cluster scale; nevertheless, more research is required to fully understand these systems. In this work, we used the density functional theory (DFT) formalism, specifically the PBE functional and the TZ2P basis set for the study of structural, electronic, and chemical properties of GanAsm (m + n = 2–9) clusters in the gas phase, for all possible compositions. Our study reveals that the structural and electronic properties in GanAsm clusters present a size and composition dependence, with a size range within 3–10 A. Even/odd behavior is observed in most electronic and chemical properties of the clusters. The even/odd behavior is related to the electronic close shell structure of the system. It is found that the predominance of arsenic atoms in the GanAsm clusters generate comparatively more stable molecules, with lower binding energies per atom, higher hardness values, ionization potentials, and GapHOMO-LUMO.

Coordination chemistry of 2D and layered gray arsenic: photochemical functionalization with chromium hexacarbonyl

The functionalization of layered materials is one of the current challenges in material science. Exfoliated rhombohedral (gray) arsenic represents a promising layered material for the fabrication of electronic devices and sensors; however, synthetic protocols for tuning its properties or protecting the surface by covalent functionalization are not known. In this communication, we present its covalent functionalization accompanied by the exfoliation of rhombohedral arsenic in the presence of ultraviolet light irradiation and chromium hexacarbonyl. During this modification, the arsenic atoms act as ligands to the chromium metal center. We believe that this study provides a promising approach for the modification of rhombohedral few-layer arsenene and enables its application in various fields, including electronic devices, sensors, and energy devices.

Dibenzoarsepins: Planarization of 8π‐Electron System in the Lowest Singlet Excited State

AbstractDibenzo[b,f]arsepins possessing severely distorted cores compared to those of other heteropins were synthesized. These derivatives exhibited dual photoluminescence in the green‐to‐red region (500–700 nm) and the near‐ultraviolet region (&lt;380 nm), which could be attributed to the planarization of the arsepin core in the lowest singlet excited (S1) state. The computational approach for the assessment of the aromatic indices revealed that the dibenzoarsepins studied show aromaticity (8π system) in the S1 states in line with Baird's rule. The lone pair electrons of the arsenic atoms play a crucial role in the aromaticity in the S1 states.

Dibenzoarsepins: Planarization of 8π-Electron System in the Lowest Singlet Excited State.

Dibenzo[b,f]arsepins possessing severely distorted cores compared to those of other heteropins were synthesized. These derivatives exhibited dual photoluminescence in the green-to-red region (500-700 nm) and the near-ultraviolet region (<380 nm), which could be attributed to the planarization of the arsepin core in the lowest singlet excited (S1 ) state. The computational approach for the assessment of the aromatic indices revealed that the dibenzoarsepins studied show aromaticity (8π system) in the S1 states in line with Baird's rule. The lone pair electrons of the arsenic atoms play a crucial role in the aromaticity in the S1 states.