Nanomaterials

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13 pages, 812 KiB

Open AccessArticle

Model and Energy Bounds for a Two-Dimensional System of Electrons Localized in Concentric Rings

by Orion Ciftja, Josep Batle, Mahmoud Abdel-Aty, Mohammad Ahmed Hafez and Shawkat Alkhazaleh

Nanomaterials 2024, 14(20), 1615; https://doi.org/10.3390/nano14201615 - 10 Oct 2024

Viewed by 552

We study a two-dimensional system of interacting electrons confined in equidistant planar circular rings. The electrons are considered spinless and each of them is localized in one ring. While confined to such ring orbits, each electron interacts with the remaining ones by means [...] Read more.

We study a two-dimensional system of interacting electrons confined in equidistant planar circular rings. The electrons are considered spinless and each of them is localized in one ring. While confined to such ring orbits, each electron interacts with the remaining ones by means of a standard Coulomb interaction potential. The classical version of this two-dimensional quantum model can be viewed as representing a system of electrons orbiting planar equidistant concentric rings where the kinetic energy may be discarded when one is searching for the lowest possible energy. Within this framework, the lowest possible energy of the system is the one that minimizes the total Coulomb interaction energy. This is the equilibrium energy that is numerically determined with high accuracy by using the simulated annealing method. This process allows us to obtain both the equilibrium energy and position configuration for different system sizes. The adopted semi-classical approach allows us to provide reliable approximations for the quantum ground state energy of the corresponding quantum system. The model considered in this work represents an interesting problem for studies of low-dimensional systems, with echoes that resonate with developments in nanoscience and nanomaterials. Full article

(This article belongs to the Special Issue Fundamental and Applied Aspects of the Physics in Low-Dimensional Systems)

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14 pages, 3318 KiB

Open AccessArticle

A Quantum Mechanical MP2 Study of the Electronic Effect of Nonplanarity on the Carbon Pyramidalization of Fullerene C₆₀

by Yuemin Liu, Yunxiang Gao, Tariq Altalhi, Di-Jia Liu and Boris I. Yakobson

Nanomaterials 2024, 14(19), 1576; https://doi.org/10.3390/nano14191576 - 29 Sep 2024

Cited by 1 | Viewed by 693

Abstract

Among C₆₀’s diverse functionalities, its potential application in CO₂ sequestration has gained increasing interest. However, the processes involved are sensitive to the molecule’s electronic structure, aspects of which remain debated and require greater precision. To address this, we performed structural [...] Read more.

Among C₆₀’s diverse functionalities, its potential application in CO₂ sequestration has gained increasing interest. However, the processes involved are sensitive to the molecule’s electronic structure, aspects of which remain debated and require greater precision. To address this, we performed structural optimization of fullerene C₆₀ using the QM MP2/6–31G* method. The nonplanarity of the optimized icosahedron is characterized by two types of dihedral angles: 138° and 143°. The 120 dihedrals of 138° occur between two hexagons intersecting at C–C bonds of 1.42 Å, while the 60 dihedrals of 143° are observed between hexagons and pentagons at C–C bonds of 1.47 Å. NBO analysis reveals less pyramidal sp^1.78 hybridization for carbons at the 1.42 Å bonds and more pyramidal sp^2.13 hybridization for the 1.47 Å bonds. Electrostatic potential charges range from −0.04 a.u. to 0.04 a.u. on the carbon atoms. Second-order perturbation analysis indicates that delocalization interactions in the C–C bonds of 1.42 Å (143.70 kcal/mol) and 1.47 Å (34.98 kcal/mol) are 22% and 38% higher, respectively, than those in benzene. MP2/Def2SVP calculations yield a correlation energy of 13.49 kcal/mol per electron for C₆₀, slightly higher than the 11.68 kcal/mol for benzene. However, the results from HOMO-LUMO calculations should be interpreted with caution. This study may assist in the rational design of fullerene C₆₀ derivatives for CO₂ reduction systems. Full article

(This article belongs to the Special Issue Fundamental and Applied Aspects of the Physics in Low-Dimensional Systems)

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15 pages, 7504 KiB

Open AccessArticle

The Stability of UV-Defluorination-Driven Crosslinked Carbon Nanotubes: A Raman Study

by Yunxiang Gao, Mohammad Tarequl Islam, Promise Uzoamaka Otuokere, Merlyn Pulikkathara and Yuemin Liu

Nanomaterials 2024, 14(17), 1464; https://doi.org/10.3390/nano14171464 - 9 Sep 2024

Viewed by 769

Abstract

Carbon nanotubes (CNTs) are often regarded as semi-rigid, all-carbon polymers. However, unlike conventional polymers that can form 3D networks such as hydrogels or elastomers through crosslinking in solution, CNTs have long been considered non-crosslinkable under mild conditions. This perception changed with our recent [...] Read more.

Carbon nanotubes (CNTs) are often regarded as semi-rigid, all-carbon polymers. However, unlike conventional polymers that can form 3D networks such as hydrogels or elastomers through crosslinking in solution, CNTs have long been considered non-crosslinkable under mild conditions. This perception changed with our recent discovery of UV-defluorination-driven direct crosslinking of CNTs in solution. In this study, we further investigate the thermal stability of UV-defluorination-driven crosslinked CNTs, revealing that they are metastable and decompose more readily than either pristine or fluorinated CNTs under Raman laser irradiation. Using Raman spectroscopy under controlled laser power, we examined both single-walled and multi-walled fluorinated CNTs. The results demonstrate that UV-defluorinated CNTs exhibit reduced thermal stability compared to their pristine or untreated fluorinated counterparts. This instability is attributed to the strain on the intertube crosslinking bonds resulting from the curved carbon lattice of the linked CNTs. The metallic CNTs in the crosslinked CNT networks decompose and revert to their pristine state more readily than the semiconducting ones. The inherent instability of crosslinked CNTs leads to combustion at temperatures approximately 100 °C lower than those required for non-crosslinked fluorinated CNTs. This property positions crosslinked CNTs as promising candidates for applications where mechanically robust, lightweight materials are needed, along with feasible post-use removal options. Full article

(This article belongs to the Special Issue Fundamental and Applied Aspects of the Physics in Low-Dimensional Systems)

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13 pages, 10050 KiB

Open AccessArticle

Graphitic Carbon Nitride Catalyzes the Reduction of the Azo Bond by Hydrazine under Visible Light

by Makobi C. Okolie, Glory G. Ollordaa, Gopal R. Ramidi, Xin Yan, Yufeng Quan, Qingsheng Wang and Yingchun Li

Nanomaterials 2024, 14(17), 1402; https://doi.org/10.3390/nano14171402 - 28 Aug 2024

Viewed by 686

Abstract

Graphitic carbon nitride is a semiconducting material of a graphite-like 2D layered structure. It is well known for its photocatalytic properties, which can be exploited for solar-light-driven water splitting and degradation of organic pollutants. Here, we report its capabilities of catalyzing the reduction [...] Read more.

Graphitic carbon nitride is a semiconducting material of a graphite-like 2D layered structure. It is well known for its photocatalytic properties, which can be exploited for solar-light-driven water splitting and degradation of organic pollutants. Here, we report its capabilities of catalyzing the reduction of the azo bond by hydrazine to two amines under visible light. This photocatalytic reaction provides a novel, appealing way to reduce azo dye wastes as pollutants other than degradation. With this method, the azo dye wastes can be photochemically converted to amines, which can be used as precursors for new azo dyes. Full article

(This article belongs to the Special Issue Fundamental and Applied Aspects of the Physics in Low-Dimensional Systems)

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15 pages, 4394 KiB

Open AccessArticle

Physical Mechanism of Nanocrystalline Composite Deformation Responsible for Fracture Plastic Nature at Cryogenic Temperatures

by Jianyong Qiao, Ivan Vladimirovich Ushakov, Ivan Sergeevich Safronov, Ayur Dasheevich Oshorov, Zhiqiang Wang, Olga Vitalievna Andrukhova and Olga Vladimirovna Rychkova

Nanomaterials 2024, 14(8), 723; https://doi.org/10.3390/nano14080723 - 20 Apr 2024

Viewed by 1064

Abstract

In this work, we consider the physical basis of deformation and fracture in layered composite nanocrystalline/amorphous material–low-melting crystalline alloy in a wide temperature range. Deformation and fracture at the crack tip on the boundary of such materials as nanocrystalline alloy of the trademark [...] Read more.

In this work, we consider the physical basis of deformation and fracture in layered composite nanocrystalline/amorphous material–low-melting crystalline alloy in a wide temperature range. Deformation and fracture at the crack tip on the boundary of such materials as nanocrystalline alloy of the trademark 5BDSR, amorphous alloy of the trademark 82K3XSR and low-melting crystalline alloy were experimentally investigated. The crack was initiated by uniaxial stretching in a temperature range of 77–293 K. A theoretical description of the processes of deformation and fracture at the crack tip is proposed, with the assumption that these processes lead to local heating and ensure the plastic character of crack growth at liquid nitrogen temperatures. The obtained results improve the theoretical understanding of the physics of fracture at the boundary of nanocrystalline and crystalline alloys in a wide temperature range. The possibility of preserving the plastic nature of fracture in a thin boundary layer of crystalline–nanocrystalline material at cryogenic temperatures has been experimentally shown. Full article

(This article belongs to the Special Issue Fundamental and Applied Aspects of the Physics in Low-Dimensional Systems)

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63 pages, 5872 KiB

Open AccessArticle

Toward a New Theory of the Fractional Quantum Hall Effect

by Sergey A. Mikhailov

Nanomaterials 2024, 14(3), 297; https://doi.org/10.3390/nano14030297 - 31 Jan 2024

Viewed by 1540

Abstract

The fractional quantum Hall effect was experimentally discovered in 1982. It was observed that the Hall conductivity

σ_{y x}

of a two-dimensional electron system is quantized,

σ_{y x} = e^{2} / 3 h

, in the vicinity of the Landau [...] Read more.

The fractional quantum Hall effect was experimentally discovered in 1982. It was observed that the Hall conductivity

σ_{y x}

of a two-dimensional electron system is quantized,

σ_{y x} = e^{2} / 3 h

, in the vicinity of the Landau level filling factor

ν = 1 / 3

. In 1983, Laughlin proposed a trial many-body wave function, which he claimed described a “new state of matter”—a homogeneous incompressible liquid with fractionally charged quasiparticles. Here, I develop an exact diagonalization theory that allows one to calculate the energy and other physical properties of the ground and excited states of a system of N two-dimensional Coulomb interacting electrons in a strong magnetic field. I analyze the energies, electron densities, and other physical properties of the systems with

N \leq 7

electrons continuously as a function of magnetic field in the range

1 / 4 ≲ ν < 1

. The results show that both the ground and excited states of the system resemble a sliding Wigner crystal whose parameters are influenced by the magnetic field. Energy gaps in the many-particle spectra appear and disappear as the magnetic field changes. I also calculate the physical properties of the

ν = 1 / 3

Laughlin state for

N \leq 8

and compare the results with the exact ones. This comparison, as well as an analysis of some other statements published in the literature, show that the Laughlin state and its fractionally charged excitations do not describe the physical reality, neither at small N nor in the thermodynamic limit. The results obtained shed new light on the nature of the ground and excited states in the fractional quantum Hall effect. Full article

(This article belongs to the Special Issue Fundamental and Applied Aspects of the Physics in Low-Dimensional Systems)

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9 pages, 1928 KiB

Open AccessArticle

Accurate Quantum States for a 2D-Dipole

by Daniel Vrinceanu

Nanomaterials 2024, 14(2), 206; https://doi.org/10.3390/nano14020206 - 17 Jan 2024

Viewed by 1044

Abstract

Edge dislocations are crucial in understanding both mechanical and electrical transport in solid and are modeled as line distributions of dipole moments. The calculation of the electronic spectrum for the two dimensional dipole, represented by the potential energy [...] Read more.

Edge dislocations are crucial in understanding both mechanical and electrical transport in solid and are modeled as line distributions of dipole moments. The calculation of the electronic spectrum for the two dimensional dipole, represented by the potential energy

V (r, θ) = p cos θ / r

, has been the topic of several studies that show significant difficulties in obtaining accurate results. In this work, we demonstrate that the source of these difficulties is a logarithmic contribution to the behavior of the wave function at the origin that was neglected by previous authors. By taking into account this non-analytic deviation of the solution of Schrödinger’s equation, superior results, with the expected rate of convergence, are obtained. This goal is accomplished by “adapting” general algorithms for solving partial derivative differential equations to include the desired asymptotic behavior. We illustrate this principle for the variational principle and finite difference methods. Accurate energies and wave functions are obtained not only for the ground state but also for the first eleven excited states and are useful for designing nanoelectronic devices. This paper demonstrates that augmentary knowledge about analytic properties of the solutions leads to the improved convergence and stability of numerical methods. Full article

(This article belongs to the Special Issue Fundamental and Applied Aspects of the Physics in Low-Dimensional Systems)

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14 pages, 11241 KiB

Open AccessArticle

Physical Mechanism of Selective Healing of Nanopores in Condensed Matter under the Influence of Laser Irradiation and Plasma

by Zhiqiang Wang, Ivan Vladimirovich Ushakov, Ivan Sergeevich Safronov and Jianping Zuo

Nanomaterials 2024, 14(2), 139; https://doi.org/10.3390/nano14020139 - 8 Jan 2024

Cited by 3 | Viewed by 1557

Abstract

The investigation of the features of laser control over the state of nanoscale objects in solid materials is an urgent task of condensed matter physics. We experimentally established the potential for the simultaneous enhancement of hardness and resistance to surface cracking in a [...] Read more.

The investigation of the features of laser control over the state of nanoscale objects in solid materials is an urgent task of condensed matter physics. We experimentally established the potential for the simultaneous enhancement of hardness and resistance to surface cracking in a titanium alloy due to selective laser irradiation. The regularities of selective heating near nanopores and the influence of the nanopore system on the features of isotherm propagation have been revealed. A physical model is proposed for the healing of nanopores situated in the surface layer of the sample. According to this model and as a result of laser irradiation and laser plasma, a brief transition of the material surface to extreme conditions is initiated. Full article

(This article belongs to the Special Issue Fundamental and Applied Aspects of the Physics in Low-Dimensional Systems)

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15 pages, 379 KiB

Open AccessArticle

Interaction Potential between a Uniformly Charged Square Nanoplate and Coplanar Nanowire

by Orion Ciftja

Nanomaterials 2023, 13(23), 2988; https://doi.org/10.3390/nano13232988 - 21 Nov 2023

Cited by 1 | Viewed by 853

Abstract

We study a structure consisting of two electrostatically interacting objects, a uniformly charged square nanoplate and a uniformly charged nanowire. A straightforward motivation behind this work is to introduce a model that allows a classical description of a finite two-dimensional quantum Hall system [...] Read more.

We study a structure consisting of two electrostatically interacting objects, a uniformly charged square nanoplate and a uniformly charged nanowire. A straightforward motivation behind this work is to introduce a model that allows a classical description of a finite two-dimensional quantum Hall system of few electrons when the Landau gauge is imposed. In this scenario, the uniformly charged square nanoplate would stand for the neutralizing background of the system while a uniformly charged nanowire would represent the resulting quantum striped state of the electrons. A second important feature of this model is that it also applies to hybrid charged nanoplate-nanowire systems in which the dominant interaction has electrostatic origin. An exact analytical expression for the electrostatic interaction potential between the uniformly charged square nanoplate and coplanar nanowire is obtained by using a special mathematical method adept for this geometry. It is found that the resulting interaction potential is finite, monotonic and slowly-varying for all locations of the nanowire inside the nanoplate. Full article

(This article belongs to the Special Issue Fundamental and Applied Aspects of the Physics in Low-Dimensional Systems)

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