Nanomaterials

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5 pages, 200 KiB

Open AccessEditorial

Special Issue “Theoretical Calculation and Molecular Modeling of Nanomaterials”

by Frederik Tielens

Nanomaterials 2023, 13(17), 2473; https://doi.org/10.3390/nano13172473 - 1 Sep 2023

Viewed by 1096

Abstract

The continuous advancement of computational chemistry and the chemical modeling of materials is closely aligned with the ever-evolving computational power and related techniques [...] Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

Research

Jump to: Editorial

20 pages, 3886 KiB

Open AccessFeature PaperArticle

On the Origin of Raman Activity in Anatase TiO₂ (Nano)Materials: An Ab Initio Investigation of Surface and Size Effects

by Beata Taudul, Frederik Tielens and Monica Calatayud

Nanomaterials 2023, 13(12), 1856; https://doi.org/10.3390/nano13121856 - 14 Jun 2023

Cited by 13 | Viewed by 3216

Abstract

Titania-based materials are abundant in technological applications, as well as everyday products; however, many of its structure–property relationships are still unclear. In particular, its surface reactivity on the nanoscale has important consequences for fields such as nanotoxicity or (photo)catalysis. Raman spectroscopy has been [...] Read more.

Titania-based materials are abundant in technological applications, as well as everyday products; however, many of its structure–property relationships are still unclear. In particular, its surface reactivity on the nanoscale has important consequences for fields such as nanotoxicity or (photo)catalysis. Raman spectroscopy has been used to characterize titania-based (nano)material surfaces, mainly based on empirical peak assignments. In the present work, we address the structural features responsible for the Raman spectra of pure, stoichiometric TiO₂ materials from a theoretical characterization. We determine a computational protocol to obtain accurate Raman response in a series of anatase TiO₂ models, namely, the bulk and three low-index terminations by periodic ab initio approaches. The origin of the Raman peaks is thoroughly analyzed and the structure–Raman mapping is performed to account for structural distortions, laser and temperature effects, surface orientation, and size. We address the appropriateness of previous experimental use of Raman to quantify the presence of distinct TiO₂ terminations, and provide guidelines to exploit the Raman spectrum based on accurate rooted calculations that could be used to characterize a variety of titania systems (e.g., single crystals, commercial catalysts, thin layered materials, facetted nanoparticles, etc.). Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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10 pages, 1675 KiB

Open AccessArticle

DFT Study of Adsorption Behavior of Nitro Species on Carbon-Doped Boron Nitride Nanoribbons for Toxic Gas Sensing

by Francisco Villanueva-Mejia, Santiago José Guevara-Martínez, Manuel Arroyo-Albiter, José Juan Alvarado-Flores and Adalberto Zamudio-Ojeda

Nanomaterials 2023, 13(8), 1410; https://doi.org/10.3390/nano13081410 - 19 Apr 2023

Cited by 1 | Viewed by 1537

Abstract

The modifications of the electronic properties on carbon-doped boron nitride nanoribbons (BNNRs) as a response to the adsorption of different nitro species were investigated in the framework of the density functional theory within the generalized gradient approximation. Calculations were performed using the SIESTA [...] Read more.

The modifications of the electronic properties on carbon-doped boron nitride nanoribbons (BNNRs) as a response to the adsorption of different nitro species were investigated in the framework of the density functional theory within the generalized gradient approximation. Calculations were performed using the SIESTA code. We found that the main response involved tuning the original magnetic behavior to a non-magnetic system when the molecule was chemisorbed on the carbon-doped BNNR. It was also revealed that some species could be dissociated through the adsorption process. Furthermore, the nitro species preferred to interact over nanosurfaces where dopants substituted the B sublattice of the carbon-doped BNNRs. Most importantly, the switch on the magnetic behavior offers the opportunity to apply these systems to fit novel technological applications. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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12 pages, 6911 KiB

Open AccessArticle

High-Accuracy Neural Network Interatomic Potential for Silicon Nitride

by Hui Xu, Zeyuan Li, Zhaofu Zhang, Sheng Liu, Shengnan Shen and Yuzheng Guo

Nanomaterials 2023, 13(8), 1352; https://doi.org/10.3390/nano13081352 - 13 Apr 2023

Cited by 6 | Viewed by 2698

Abstract

In the field of machine learning (ML) and data science, it is meaningful to use the advantages of ML to create reliable interatomic potentials. Deep potential molecular dynamics (DEEPMD) are one of the most useful methods to create interatomic potentials. Among ceramic materials, [...] Read more.

In the field of machine learning (ML) and data science, it is meaningful to use the advantages of ML to create reliable interatomic potentials. Deep potential molecular dynamics (DEEPMD) are one of the most useful methods to create interatomic potentials. Among ceramic materials, amorphous silicon nitride (SiN_x) features good electrical insulation, abrasion resistance, and mechanical strength, which is widely applied in industries. In our work, a neural network potential (NNP) for SiN_x was created based on DEEPMD, and the NNP is confirmed to be applicable to the SiN_x model. The tensile tests were simulated to compare the mechanical properties of SiN_x with different compositions based on the molecular dynamic method coupled with NNP. Among these SiN_x, Si₃N₄ has the largest elastic modulus (E) and yield stress (σ_s), showing the desired mechanical strength owing to the largest coordination numbers (CN) and radial distribution function (RDF). The RDFs and CNs decrease with the increase of x; meanwhile, E and σ_s of SiN_x decrease when the proportion of Si increases. It can be concluded that the ratio of nitrogen to silicon can reflect the RDFs and CNs in micro level and macro mechanical properties of SiN_x to a large extent. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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14 pages, 1591 KiB

Open AccessEditor’s ChoiceArticle

A DFT Study of Ruthenium fcc Nano-Dots: Size-Dependent Induced Magnetic Moments

by Marietjie J. Ungerer and Nora H. de Leeuw

Nanomaterials 2023, 13(6), 1118; https://doi.org/10.3390/nano13061118 - 21 Mar 2023

Cited by 3 | Viewed by 3003

Abstract

Many areas of electronics, engineering and manufacturing rely on ferromagnetic materials, including iron, nickel and cobalt. Very few other materials have an innate magnetic moment rather than induced magnetic properties, which are more common. However, in a previous study of ruthenium nanoparticles, the [...] Read more.

Many areas of electronics, engineering and manufacturing rely on ferromagnetic materials, including iron, nickel and cobalt. Very few other materials have an innate magnetic moment rather than induced magnetic properties, which are more common. However, in a previous study of ruthenium nanoparticles, the smallest nano-dots showed significant magnetic moments. Furthermore, ruthenium nanoparticles with a face-centred cubic (fcc) packing structure exhibit high catalytic activity towards several reactions and such catalysts are of special interest for the electrocatalytic production of hydrogen. Previous calculations have shown that the energy per atom resembles that of the bulk energy per atom when the surface-to-bulk ratio < 1, but in its smallest form, nano-dots exhibit a range of other properties. Therefore, in this study, we have carried out calculations based on the density functional theory (DFT) with long-range dispersion corrections DFT-D3 and DFT-D3-(BJ) to systematically investigate the magnetic moments of two different morphologies and various sizes of Ru nano-dots in the fcc phase. To confirm the results obtained by the plane-wave DFT methodologies, additional atom-centred DFT calculations were carried out on the smallest nano-dots to establish accurate spin-splitting energetics. Surprisingly, we found that in most cases, the high spin electronic structures had the most favourable energies and were hence the most stable. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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15 pages, 2634 KiB

Open AccessArticle

Back to the Basics: Probing the Role of Surfaces in the Experimentally Observed Morphological Evolution of ZnO

by Amanda F. Gouveia, Samantha C. S. Lemos, Edson R. Leite, Elson Longo and Juan Andrés

Nanomaterials 2023, 13(6), 978; https://doi.org/10.3390/nano13060978 - 8 Mar 2023

Cited by 2 | Viewed by 1970

Abstract

Although the physics and chemistry of materials are driven by exposed surfaces in the morphology, they are fleeting, making them inherently challenging to study experimentally. The rational design of their morphology and delivery in a synthesis process remains complex because of the numerous [...] Read more.

Although the physics and chemistry of materials are driven by exposed surfaces in the morphology, they are fleeting, making them inherently challenging to study experimentally. The rational design of their morphology and delivery in a synthesis process remains complex because of the numerous kinetic parameters that involve the effective shocks of atoms or clusters, which end up leading to the formation of different morphologies. Herein, we combined functional density theory calculations of the surface energies of ZnO and the Wulff construction to develop a simple computational model capable of predicting its available morphologies in an attempt to guide the search for images obtained by field-emission scanning electron microscopy (FE-SEM). The figures in this morphology map agree with the experimental FE-SEM images. The mechanism of this computational model is as follows: when the model is used, a reaction pathway is designed to find a given morphology and the ideal step height in the whole morphology map in the practical experiment. This concept article provides a practical tool to understand, at the atomic level, the routes for the morphological evolution observed in experiments as well as their correlation with changes in the properties of materials based solely on theoretical calculations. The findings presented herein not only explain the occurrence of changes during the synthesis (with targeted reaction characteristics that underpin an essential structure–function relationship) but also offer deep insights into how to enhance the efficiency of other metal-oxide-based materials via matching. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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16 pages, 4631 KiB

Open AccessArticle

Nanostructure, Plastic Deformation, and Influence of Strain Rate Concerning Ni/Al₂O₃ Interface System Using a Molecular Dynamic Study (LAMMPS)

by Xueqiong Fu

Nanomaterials 2023, 13(4), 641; https://doi.org/10.3390/nano13040641 - 6 Feb 2023

Cited by 6 | Viewed by 2563

Abstract

The plastic deformation mechanisms of Ni/Al₂O₃ interface systems under tensile loading at high strain rates were investigated by the classical molecular dynamics (MD) method. A Rahman–Stillinger–Lemberg potential was used for modeling the interaction between Ni and Al atoms and between [...] Read more.

The plastic deformation mechanisms of Ni/Al₂O₃ interface systems under tensile loading at high strain rates were investigated by the classical molecular dynamics (MD) method. A Rahman–Stillinger–Lemberg potential was used for modeling the interaction between Ni and Al atoms and between Ni and O atoms at the interface. To explore the dislocation nucleation and propagation mechanisms during interface tensile failure, two kinds of interface structures corresponding to the terminating Ni layer as buckling layer (Type I) and transition layer (Type II) were established. The fracture behaviors show a strong dependence on interface structure. For Type I interface samples, the formation of Lomer–Cottrell locks in metal causes strain hardening; for Type II interface samples, the yield strength is 40% higher than that of Type I due to more stable Ni-O bonds at the interface. At strain rates higher than

1 \times 10^{9} s^{- 1}

, the formation of L-C locks in metal is suppressed (Type I), and the formation of Shockley dislocations at the interface is delayed (Type II). The present work provides the direct observation of nucleation, motion, and reaction of dislocations associated with the complex interface dislocation structures of Ni/Al₂O₃ interfaces and can help researchers better understand the deformation mechanisms of this interface at extreme conditions. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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22 pages, 2994 KiB

Open AccessEditor’s ChoiceArticle

Lanthanide(III) Ions and 5-Methylisophthalate Ligand Based Coordination Polymers: An Insight into Their Photoluminescence Emission and Chemosensing for Nitroaromatic Molecules

by Oier Pajuelo-Corral, Laura Razquin-Bobillo, Sara Rojas, Jose Angel García, Duane Choquesillo-Lazarte, Alfonso Salinas-Castillo, Ricardo Hernández, Antonio Rodríguez-Diéguez and Javier Cepeda

Nanomaterials 2022, 12(22), 3977; https://doi.org/10.3390/nano12223977 - 11 Nov 2022

Cited by 4 | Viewed by 2541

Abstract

The work presented herein reports on the synthesis, structural and physico-chemical characterization, luminescence properties and luminescent sensing activity of a family of isostructural coordination polymers (CPs) with the general formula [Ln₂(μ₄-5Meip)₃(DMF)]_n (where Ln(III) = Sm ( [...] Read more.

The work presented herein reports on the synthesis, structural and physico-chemical characterization, luminescence properties and luminescent sensing activity of a family of isostructural coordination polymers (CPs) with the general formula [Ln₂(μ₄-5Meip)₃(DMF)]_n (where Ln(III) = Sm (1_Sm), Eu (2_Eu), Gd (3_Gd), Tb (4_Tb) and Yb (5_Yb) and 5Meip = 5-methylisophthalate, DMF = N,N-dimethylmethanamide). Crystal structures consist of 3D frameworks tailored by the linkage between infinite lanthanide(III)-carboxylate rods by means of the tetradentate 5Meip ligands. Photoluminescence measurements in solid state at variable temperatures reveal the best-in-class properties based on the capacity of the 5Meip ligand to provide efficient energy transfers to the lanthanide(III) ions, which brings intense emissions in both the visible and near-infrared (NIR) regions. On the one hand, compound 5_Yb displays characteristic lanthanide-centered bands in the NIR with sizeable intensity even at room temperature. Among the compounds emitting in the visible region, 4_Tb presents a high QY of 63%, which may be explained according to computational calculations. At last, taking advantage of the good performance as well as high chemical and optical stability of 4_Tb in water and methanol, its sensing capacity to detect 2,4,6-trinitrophenol (TNP) among other nitroaromatic-like explosives has been explored, obtaining high detection capacity (with K_sv around 10⁵ M⁻¹), low limit of detection (in the 10⁻⁶–10⁻⁷ M) and selectivity among other molecules (especially in methanol). Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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17 pages, 7349 KiB

Open AccessArticle

Electronic Properties of Hexagonal Graphene Quantum Rings from TAO-DFT

by Chi-Chun Chen and Jeng-Da Chai

Nanomaterials 2022, 12(22), 3943; https://doi.org/10.3390/nano12223943 - 9 Nov 2022

Cited by 3 | Viewed by 3400

Abstract

The reliable prediction of electronic properties associated with graphene nanosystems can be challenging for conventional electronic structure methods, such as Kohn–Sham (KS) density functional theory (DFT), due to the presence of strong static correlation effects in these systems. To address this challenge, TAO [...] Read more.

The reliable prediction of electronic properties associated with graphene nanosystems can be challenging for conventional electronic structure methods, such as Kohn–Sham (KS) density functional theory (DFT), due to the presence of strong static correlation effects in these systems. To address this challenge, TAO (thermally assisted occupation) DFT has been recently proposed. In the present study, we employ TAO-DFT to predict the electronic properties of n-HGQRs (i.e., the hexagonal graphene quantum rings consisting of n aromatic rings fused together at each side). From TAO-DFT, the ground states of n-HGQRs are singlets for all the cases investigated (n = 3–15). As the system size increases, there should be a transition from the nonradical to polyradical nature of ground-state n-HGQR. The latter should be intimately related to the localization of active TAO-orbitals at the inner and outer edges of n-HGQR, which increases with increasing system size. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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22 pages, 1769 KiB

Open AccessArticle

Electronic Transport in Weyl Semimetals with a Uniform Concentration of Torsional Dislocations

by Daniel Bonilla and Enrique Muñoz

Nanomaterials 2022, 12(20), 3711; https://doi.org/10.3390/nano12203711 - 21 Oct 2022

Cited by 5 | Viewed by 1738

Abstract

In this article, we consider a theoretical model for a type I Weyl semimetal, under the presence of a diluted uniform concentration of torsional dislocations. By means of a mathematical analysis for partial wave scattering (phase-shift) for the T-matrix, we obtain the corresponding [...] Read more.

In this article, we consider a theoretical model for a type I Weyl semimetal, under the presence of a diluted uniform concentration of torsional dislocations. By means of a mathematical analysis for partial wave scattering (phase-shift) for the T-matrix, we obtain the corresponding retarded and advanced Green’s functions that include the effects of multiple scattering events with the ensemble of randomly distributed dislocations. Combining this analysis with the Kubo formalism, and including vertex corrections, we calculate the electronic conductivity as a function of temperature and concentration of dislocations. We further evaluate our analytical formulas to predict the electrical conductivity of several transition metal monopnictides, i.e., TaAs, TaP, NbAs, and NbP. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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11 pages, 2676 KiB

Open AccessArticle

Mechanism for the Intercalation of Aniline Cations into the Interlayers of Graphite

by Yifan Guo, Ying Li, Wei Wei, Junhua Su, Jinyang Li, Yanlei Shang, Yong Wang, Xiaoling Xu, David Hui and Zuowan Zhou

Nanomaterials 2022, 12(14), 2486; https://doi.org/10.3390/nano12142486 - 20 Jul 2022

Cited by 4 | Viewed by 2434

Abstract

The dynamic behaviors of aniline cation (ANI⁺) intercalating into graphite interlayers are systematically studied by experimental studies and multiscale simulations. The in situ intercalation polymerization designed by response surface methods implies the importance of ultrasonication for achieving the intercalation of ANI [...] Read more.

The dynamic behaviors of aniline cation (ANI⁺) intercalating into graphite interlayers are systematically studied by experimental studies and multiscale simulations. The in situ intercalation polymerization designed by response surface methods implies the importance of ultrasonication for achieving the intercalation of ANI⁺. Molecular dynamics and quantum chemical simulations prove the adsorption of ANI⁺ onto graphite surfaces by cation–π electrostatic interactions, weakening the π–π interactions between graphene layers. The ultrasonication that follows breaks the hydrated ANI⁺ clusters into individual ANI⁺. Thus, the released positive charges of these dissociative cations and reduced steric hindrance significantly improve their intercalation ability. With the initial kinetic energy provided by ultrasonic field, the activated ANI⁺ are able to intercalate into the interlayer of graphite. This work demonstrates the intercalation behaviors of ANI⁺, which provides an opportunity for investigations regarding organic-molecule-intercalated graphite compounds. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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11 pages, 6138 KiB

Open AccessEditor’s ChoiceArticle

Effect of the Dopant Configuration on the Electronic Transport Properties of Nitrogen-Doped Carbon Nanotubes

by Kim Eklund and Antti J. Karttunen

Nanomaterials 2022, 12(2), 199; https://doi.org/10.3390/nano12020199 - 7 Jan 2022

Cited by 9 | Viewed by 3062

Abstract

Nitrogen-doped carbon nanotubes (N-CNTs) show promise in several applications related to catalysis and electrochemistry. In particular, N-CNTs with a single nitrogen dopant in the unit cell have been extensively studied computationally, but the structure-property correlations between the relative positions of several nitrogen dopants [...] Read more.

Nitrogen-doped carbon nanotubes (N-CNTs) show promise in several applications related to catalysis and electrochemistry. In particular, N-CNTs with a single nitrogen dopant in the unit cell have been extensively studied computationally, but the structure-property correlations between the relative positions of several nitrogen dopants and the electronic transport properties of N-CNTs have not been systematically investigated with accurate hybrid density functional methods. We use hybrid density functional theory and semiclassical Boltzmann transport theory to systematically investigate the effect of different substitutional nitrogen doping configurations on the electrical conductivity of N-CNTs. Our results indicate significant variation in the electrical conductivity and the relative energies of the different dopant configurations. The findings can be utilized in the optimization of electrical transport properties of N-CNTs. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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19 pages, 1161 KiB

Open AccessArticle

Grand Canonical Monte Carlo Simulations to Determine the Optimal Interlayer Distance of a Graphene Slit-Shaped Pore for Adsorption of Methane, Hydrogen and their Equimolar Mixture

by Jelle Vekeman, Daniel Bahamon, Inmaculada García Cuesta, Noelia Faginas-Lago, José Sánchez-Marín, Alfredo Sánchez de Merás and Lourdes F. Vega

Nanomaterials 2021, 11(10), 2534; https://doi.org/10.3390/nano11102534 - 28 Sep 2021

Cited by 7 | Viewed by 2980

Abstract

The adsorption—for separation, storage and transportation—of methane, hydrogen and their mixture is important for a sustainable energy consumption in present-day society. Graphene derivatives have proven to be very promising for such an application, yet for a good design a better understanding of the [...] Read more.

The adsorption—for separation, storage and transportation—of methane, hydrogen and their mixture is important for a sustainable energy consumption in present-day society. Graphene derivatives have proven to be very promising for such an application, yet for a good design a better understanding of the optimal pore size is needed. In this work, grand canonical Monte Carlo simulations, employing Improved Lennard–Jones potentials, are performed to determine the ideal interlayer distance for a slit-shaped graphene pore in a large pressure range. A detailed study of the adsorption behavior of methane, hydrogen and their equimolar mixture in different sizes of graphene pores is obtained through calculation of absolute and excess adsorption isotherms, isosteric heats and the selectivity. Moreover, a molecular picture is provided through z-density profiles at low and high pressure. It is found that an interlayer distance of about twice the van der Waals distance of the adsorbate is recommended to enhance the adsorbing ability. Furthermore, the graphene structures with slit-shaped pores were found to be very capable of adsorbing methane and separating methane from hydrogen in a mixture at reasonable working conditions (300 K and well below 15 atm). Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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12 pages, 1512 KiB

Open AccessArticle

Electronic Properties of Carbon Nanobelts Predicted by Thermally-Assisted-Occupation DFT

by Sonai Seenithurai and Jeng-Da Chai

Nanomaterials 2021, 11(9), 2224; https://doi.org/10.3390/nano11092224 - 29 Aug 2021

Cited by 13 | Viewed by 3917

Abstract

Accurate prediction of properties of large-scale multi-reference (MR) electronic systems remains difficult for traditional computational methods (e.g., the Hartree–Fock theory and Kohn–Sham density functional theory (DFT)). Recently, thermally-assisted-occupation (TAO)-DFT has been demonstrated to offer reliable description of electronic properties of various large-scale MR [...] Read more.

Accurate prediction of properties of large-scale multi-reference (MR) electronic systems remains difficult for traditional computational methods (e.g., the Hartree–Fock theory and Kohn–Sham density functional theory (DFT)). Recently, thermally-assisted-occupation (TAO)-DFT has been demonstrated to offer reliable description of electronic properties of various large-scale MR electronic systems. Consequently, in this work, TAO-DFT is used to unlock the electronic properties associated with C-Belt[n] (i.e., the carbon nanobelts containing n fused 12-membered carbon rings). Our calculations show that for all the system sizes reported (n = 4–24), C-Belt[n] have singlet ground states. In general, the larger the size of C-Belt[n], the more pronounced the MR character of ground-state C-Belt[n], as evident from the symmetrized von Neumann entropy and the occupation numbers of active TAO-orbitals. Furthermore, the active TAO-orbitals are delocalized along the circumference of C-Belt[n], as evident from the visualization of active TAO-orbitals. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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12 pages, 2068 KiB

Open AccessArticle

In Search of an Efficient Complexing Agent for Oxalates and Phosphates: A Quantum Chemical Study

by Jelle Vekeman, Javier Torres, Cristina Eugenia David, Els Van de Perre, Karl Martin Wissing, Emmanuel Letavernier, Dominique Bazin, Michel Daudon, Agnieszka Pozdzik and Frederik Tielens

Nanomaterials 2021, 11(7), 1763; https://doi.org/10.3390/nano11071763 - 6 Jul 2021

Cited by 10 | Viewed by 3559

Abstract

Limiting gastrointestinal oxalate absorption is a promising approach to reduce urinary oxalate excretion in patients with idiopathic and enteric hyperoxaluria. Phosphate binders, that inhibit gastrointestinal absorption of dietary phosphate by the formation of easily excretable insoluble complexes, are commonly used as a treatment [...] Read more.

Limiting gastrointestinal oxalate absorption is a promising approach to reduce urinary oxalate excretion in patients with idiopathic and enteric hyperoxaluria. Phosphate binders, that inhibit gastrointestinal absorption of dietary phosphate by the formation of easily excretable insoluble complexes, are commonly used as a treatment for hyperphosphatemia in patients with end-stage renal disease. Several of these commercially available phosphate binders also have affinity for oxalate. In this work, a series of metallic cations (Li⁺, Na⁺, Mg²⁺, Ca²⁺, Fe²⁺, Cu²⁺, Zn²⁺, Al³⁺, Fe³⁺ and La³⁺) is investigated on their binding affinity to phosphate and oxalate on one side and anionic species that could be used to administer the cationic species to the body on the other, e.g., acetate, carbonate, chloride, citrate, formate, hydroxide and sulphate. Through quantum chemical calculations, the aim is to understand the competition between the different complexes and propose possible new and more efficient phosphate and oxalate binders. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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14 pages, 3845 KiB

Open AccessArticle

Surface Energy of Curved Surface Based on Lennard-Jones Potential

by Dan Wang, Zhili Hu, Gang Peng and Yajun Yin

Nanomaterials 2021, 11(3), 686; https://doi.org/10.3390/nano11030686 - 9 Mar 2021

Cited by 16 | Viewed by 3488

Abstract

Although various phenomena have confirmed that surface geometry has an impact on surface energy at micro/nano scales, determining the surface energy on micro/nano curved surfaces remains a challenge. In this paper, based on Lennard-Jones (L-J) pair potential, we study the geometrical effect on [...] Read more.

Although various phenomena have confirmed that surface geometry has an impact on surface energy at micro/nano scales, determining the surface energy on micro/nano curved surfaces remains a challenge. In this paper, based on Lennard-Jones (L-J) pair potential, we study the geometrical effect on surface energy with the homogenization hypothesis. The surface energy is expressed as a function of local principle curvatures. The accuracy of curvature-based surface energy is confirmed by comparing surface energy on flat surface with experimental results. Furthermore, the surface energy for spherical geometry is investigated and verified by the numerical experiment with errors within 5%. The results show that (i) the surface energy will decrease on a convex surface and increase on a concave surface with the increasing of scales, and tend to the value on flat surface; (ii) the effect of curvatures will be obvious and exceed 5% when spherical radius becomes smaller than 5 nm; (iii) the surface energy varies with curvatures on sinusoidal surfaces, and the normalized surface energy relates with the ratio of wave height to wavelength. The curvature-based surface energy offers new insights into the geometrical and scales effect at micro/nano scales, which provides a theoretical direction for designing NEMS/MEMS. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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14 pages, 4082 KiB

Open AccessArticle

Molecular Understanding of Electrochemical–Mechanical Responses in Carbon-Coated Silicon Nanotubes during Lithiation

by Chen Feng, Shiyuan Liu, Junjie Li, Maoyuan Li, Siyi Cheng, Chen Chen, Tielin Shi and Zirong Tang

Nanomaterials 2021, 11(3), 564; https://doi.org/10.3390/nano11030564 - 24 Feb 2021

Cited by 9 | Viewed by 2284

Abstract

Carbon-coated silicon nanotube (SiNT@CNT) anodes show tremendous potential in high-performance lithium ion batteries (LIBs). Unfortunately, to realize the commercial application, it is still required to further optimize the structural design for better durability and safety. Here, the electrochemical and mechanical evolution in lithiated [...] Read more.

Carbon-coated silicon nanotube (SiNT@CNT) anodes show tremendous potential in high-performance lithium ion batteries (LIBs). Unfortunately, to realize the commercial application, it is still required to further optimize the structural design for better durability and safety. Here, the electrochemical and mechanical evolution in lithiated SiNT@CNT nanohybrids are investigated using large-scale atomistic simulations. More importantly, the lithiation responses of SiNW@CNT nanohybrids are also investigated in the same simulation conditions as references. The simulations quantitatively reveal that the inner hole of the SiNT alleviates the compressive stress concentration between a-Li_xSi and C phases, resulting in the SiNT@CNT having a higher Li capacity and faster lithiation rate than SiNW@CNT. The contact mode significantly regulates the stress distribution at the inner hole surface, further affecting the morphological evolution and structural stability. The inner hole of bare SiNT shows good structural stability due to no stress concentration, while that of concentric SiNT@CNT undergoes dramatic shrinkage due to compressive stress concentration, and that of eccentric SiNT@CNT is deformed due to the mismatch of stress distribution. These findings not only enrich the atomic understanding of the electrochemical–mechanical coupled mechanism in lithiated SiNT@CNT nanohybrids but also provide feasible solutions to optimize the charging strategy and tune the nanostructure of SiNT-based electrode materials. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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13 pages, 7355 KiB

Open AccessArticle

Atomistic Insights into Aluminum Doping Effect on Surface Roughness of Deposited Ultra-Thin Silver Films

by Zhong Tian, Han Yan, Qing Peng, Lin Jay Guo, Shengjun Zhou, Can Ding, Peng Li and Qi Luo

Nanomaterials 2021, 11(1), 158; https://doi.org/10.3390/nano11010158 - 10 Jan 2021

Cited by 10 | Viewed by 3807

Abstract

Ultra-thin and continuous metallic silver films are attracting growing interest due to the applications in flexible transparent conducting electrodes. The surface morphology and structure of silver film are very important for its electrical resistivity and optical loss. Therefore, roughness control is essential for [...] Read more.

Ultra-thin and continuous metallic silver films are attracting growing interest due to the applications in flexible transparent conducting electrodes. The surface morphology and structure of silver film are very important for its electrical resistivity and optical loss. Therefore, roughness control is essential for the production of ultra-thin metallic electrode film. We have investigated the effect of aluminum doping on the improvement of surface morphology of ultra-thin silver films using molecular dynamics simulations. Al-doped silver films showed smaller surface roughness than pure silver films at various substrate temperatures. When the temperature of the substrate was 600 K, the roughness of Al-doped silver film first decreased, and then increased with the increase of the incident velocity of silver atoms. Silver atoms were more likely to agglomerate on the surface of the substrate after adding aluminum atoms, as aluminum dopants promoted the immobilization of silver atoms on SiO₂ substrate due to the anchoring effect. The smoother surface could be attributable to the reduced mean free path of silver due to the cage effect by the aluminum dopant. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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12 pages, 2484 KiB

Open AccessArticle

Exfoliation Energy as a Descriptor of MXenes Synthesizability and Surface Chemical Activity

by Daniel Dolz, Ángel Morales-García, Francesc Viñes and Francesc Illas

Nanomaterials 2021, 11(1), 127; https://doi.org/10.3390/nano11010127 - 7 Jan 2021

Cited by 21 | Viewed by 3242

Abstract

MXenes are two-dimensional nanomaterials isolated from MAX phases by selective extraction of the A component—a p-block element. The MAX exfoliation energy, E_exf, is considered a chemical descriptor of the MXene synthesizability. Here, we show, by density functional theory (DFT) estimations [...] Read more.

MXenes are two-dimensional nanomaterials isolated from MAX phases by selective extraction of the A component—a p-block element. The MAX exfoliation energy, E_exf, is considered a chemical descriptor of the MXene synthesizability. Here, we show, by density functional theory (DFT) estimations of E_exf values for 486 different MAX phases, that E_exf decreases (i) when MAX is a nitride, (ii) when going along a metal M component d series, (iii) when going down a p-block A element group, and (iv) when having thicker MXenes. Furthermore, E_exf is found to bias, even to govern, the surface chemical activity, evaluated here on the CO₂ adsorption strength, so that more unstable MXenes, displaying larger E_exf values, display a stronger attachment of species upon. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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10 pages, 3317 KiB

Open AccessArticle

Heterofullerene MC₅₉ (M = B, Si, Al) as Potential Carriers for Hydroxyurea Drug Delivery

by Peng Wang, Ge Yan, Xiaodong Zhu, Yingying Du, Da Chen and Jinjuan Zhang

Nanomaterials 2021, 11(1), 115; https://doi.org/10.3390/nano11010115 - 7 Jan 2021

Cited by 26 | Viewed by 2285

Abstract

As a representative nanomaterial, C₆₀ and its derivatives have drawn much attention in the field of drug delivery over the past years, due to their unique geometric and electronic structures. Herein, the interactions of hydroxyurea (HU) drug with the pristine C₆₀ [...] Read more.

As a representative nanomaterial, C₆₀ and its derivatives have drawn much attention in the field of drug delivery over the past years, due to their unique geometric and electronic structures. Herein, the interactions of hydroxyurea (HU) drug with the pristine C₆₀ and heterofullerene MC₅₉ (M = B, Si, Al) were investigated using the density functional theory calculations. The geometric and electronic properties in terms of adsorption configuration, adsorption energy, Hirshfeld charge, frontier molecular orbitals, and charge density difference are calculated. In contrast to pristine C₆₀, it is found that HU molecule is chemisorbed on the BC₅₉, SiC₅₉, and AlC₅₉ molecules with moderate adsorption energy and apparent charge transfer. Therefore, heterofullerene BC₅₉, SiC₅₉, and AlC₅₉ are expected to be promising carriers for hydroxyurea drug delivery. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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19 pages, 3185 KiB

Open AccessArticle

A Theoretical Study of the Occupied and Unoccupied Electronic Structure of High- and Intermediate-Spin Transition Metal Phthalocyaninato (Pc) Complexes: VPc, CrPc, MnPc, and FePc

by Silvia Carlotto, Mauro Sambi, Francesco Sedona, Andrea Vittadini and Maurizio Casarin

Nanomaterials 2021, 11(1), 54; https://doi.org/10.3390/nano11010054 - 28 Dec 2020

Cited by 8 | Viewed by 4387

Abstract

The structural, electronic, and spectroscopic properties of high- and intermediate-spin transition metal phthalocyaninato complexes (MPc; M = V, Cr, Mn and Fe) have been theoretically investigated to look into the origin, symmetry and strength of the M–Pc bonding. DFT calculations coupled to the [...] Read more.

The structural, electronic, and spectroscopic properties of high- and intermediate-spin transition metal phthalocyaninato complexes (MPc; M = V, Cr, Mn and Fe) have been theoretically investigated to look into the origin, symmetry and strength of the M–Pc bonding. DFT calculations coupled to the Ziegler’s extended transition state method and to an advanced charge density and bond order analysis allowed us to assess that the M–Pc bonding is dominated by σ interactions, with FePc having the strongest and most covalent M–Pc bond. According to experimental evidence, the lightest MPcs (VPc and CrPc) have a high-spin ground state (GS), while the MnPc and FePc GS spin is intermediate. Insights into the MPc unoccupied electronic structure have been gained by modelling M L_2,3-edges X-ray absorption spectroscopy data from the literature through the exploitation of the current Density Functional Theory variant of the Restricted Open-Shell Configuration Interaction Singles (DFT/ROCIS) method. Besides the overall agreement between theory and experiment, the DFT/ROCIS results indicate that spectral features lying at the lowest excitation energies (EEs) are systematically generated by electronic states having the same GS spin multiplicity and involving M-based single electronic excitations; just as systematically, the L₃-edge higher EE region of all the MPcs herein considered includes electronic states generated by metal-to-ligand-charge-transfer transitions involving the lowest-lying π^* orbital (7e_g) of the phthalocyaninato ligand. Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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