Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 50
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
Nanoscale Adv ; 2024 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-39386120

RESUMO

First principles calculation was performed to study the Sn2Te2X4 (X = P, As) monolayers. Structural investigation confirms the stability of the two monolayers with Young's modulus in the range of 30.34-33.65 N m-1 and a Poisson's ratio of 0.18-0.21. The two monolayers are semiconductors with a direct band gap of 1.52-1.66 eV. The light absorption rate of the two monolayers is rather high 104-105 cm-1. Both monolayers have high charge carrier mobility and suitable VBM and CBM positions for the redox reaction. The η STH efficiency of both materials (15.76-17.12%) is close to the theoretical limit of 18%. Moreover, moderate strains can improve the light absorption rate, while the suitable VBM and CBM positions are preserved. These characteristics suggest that Sn2Te2X4 (X = P, As) monolayers are good candidates for being applied in flexible devices and for the conversion of solar energy to other types of energy.

2.
RSC Adv ; 14(44): 32053-32062, 2024 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-39391622

RESUMO

In the present work, we propose GaGeX2 (X = N, P, As) monolayers and explore their structural, vibrational, piezoelectric, electronic, and transport characteristics for multifunctional applications based on first-principles simulations. Our analyses of cohesive energy, phonon dispersion spectra, and ab initio molecular dynamics simulations indicate that the three proposed structures have good energetic, dynamic, and thermodynamic stabilities. The GaGeX2 are found as piezoelectric materials with high piezoelectric coefficient d 11 of -1.23 pm V-1 for the GaGeAs2 monolayer. Furthermore, the results from electronic band structures show that the GaGeX2 have semiconductor behaviours with moderate bandgap energies. At the Heyd-Scuseria-Ernzerhof level, the GaGeP2 and GaGeAs2 exhibit optimal bandgaps for photovoltaic applications of 1.75 and 1.15 eV, respectively. Moreover, to examine the transport features of the GaGeX2 monolayers, we calculate their carrier mobility. All three investigated GaGeX2 systems have anisotropic carrier mobility in the two in-plane directions for both electrons and holes. Among them, the GaGeAs2 monolayer shows the highest electron mobilities of 2270.17 and 1788.59 cm2 V-1 s-1 in the x and y directions, respectively. With high electron mobility, large piezoelectric coefficient, and moderate bandgap energy, the GaGeAs2 material holds potential applicability for electronic, optoelectronic, piezoelectric, and photovoltaic applications. Thus, our findings not only predict stable GaGeX2 structures but also provide promising materials to apply for multifunctional devices.

3.
Langmuir ; 40(39): 20783-20790, 2024 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-39307988

RESUMO

Recently, searching for a metal-semiconductor junction (MSJ) that exhibits low-contact resistance has received tremendous consideration, as they are essential components in next-generation field-effect transistors. In this work, we design a MSJ by integrating two-dimensional (2D) graphene as the metallic electrode and 2D Janus γ-Ge2SSe as the semiconducting channel using first-principles simulations. All the graphene/γ-Ge2SSe MSJs are predicted to be energetically, mechanically, and thermodynamically stable, characterized by the weak van der Waals (vdW) interactions. The graphene/γ-SGe2Se MSJ-vdWH form the n-type Schottky contact (SC), while the graphene/γ-SeGe2S MSJ-vdWH form the p-type one, suggesting that the switching between p-type and n-type SC in the graphene/γ-Ge2SSe MSJ-vdWHs can occur spontaneously by simply altering the stacking patterns, without requiring any external conditions. Notably, the contact features, including contact types and barriers of the graphene/γ-Ge2SSe MSJs are significant in versatility and can be altered by applying electric gating and adjusting interlayer spacing. Both the applied electric gating and strain engineering induce switchability between p- and n-type and SC to OC in the graphene/γ-Ge2SSE MSJs. This versatility underscores the potential of the graphene/γ-Ge2SSe MSJ for next-generation applications that require low-contact resistance and high performance.

4.
Nanoscale Adv ; 6(16): 4128-4136, 2024 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-39114137

RESUMO

Breaking structural symmetry in two-dimensional layered Janus materials can result in enhanced new phenomena and create additional degrees of piezoelectric responses. In this study, we theoretically design a series of Janus monolayers HfGeZ3H (Z = N, P, As) and investigate their structural characteristics, crystal stability, piezoelectric responses, electronic features, and carrier mobility using first-principles calculations. Phonon dispersion analysis confirms that HfGeZ3H monolayers are dynamically stable and their mechanical stability is also confirmed through the Born-Huang criteria. It is demonstrated that while HfGeN3H is a semiconductor with a large bandgap of 3.50 eV, HfGeP3H and HfGeAs3H monolayers have narrower bandgaps being 1.07 and 0.92 eV, respectively. When the spin-orbit coupling is included, large spin-splitting energy is found in the electronic bands of HfGeZ3H. Janus HfGeZ3H monolayers can be treated as piezoelectric semiconductors with the coexistence of both in-plane and out-of-plane piezoelectric responses. In particular, HfGeZ3H monolayers exhibit ultra-high electron mobilities up to 6.40 × 103 cm2 V-1 s-1 (HfGeAs3H), indicating that they have potential for various applications in nanoelectronics.

5.
RSC Adv ; 14(30): 21982-21990, 2024 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-38993506

RESUMO

In this article, an attempt is made to explore new materials for applications in piezoelectric and electronic devices. Based on density functional theory calculation, we construct three Janus ZrGeZ3H (Z = N, P, and As) monolayers and study their stability, piezoelectricity, Raman response, and carrier mobility. The results from phonon dispersion spectra, ab initio molecular dynamics simulation, and elastic coefficients confirm the structural, thermal, and mechanical stability of these proposed structures. The ZrGeZ3H monolayers are indirect band gap semiconductors with favourable band gap energy of 1.15 and 1.00 eV for the ZrGeP3H and ZrGeAs3H, respectively, from Heyd-Scuseria-Ernzerhof functional method. It is found that the Janus ZrGeZ3H monolayers possess both in-plane and out-of-plane piezoelectric coefficients, revealing that they are potential piezoelectric candidates. In addition, the carrier mobilities of electrons and holes along transport directions are anisotropic. Notably, the ZrGeP3H and ZrGeAs3H monolayers have high electron mobility of 3639.20 and 3408.37 cm2 V-1 s-1, respectively. Our findings suggest the potential application of the Janus ZrGeZ3H monolayers in the piezoelectric and electronic fields.

6.
Phys Chem Chem Phys ; 26(1): 249-260, 2023 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-38054775

RESUMO

Currently, tremendous efforts have been made to explore efficient glucose oxidation electrocatalysts for enzymeless glucose sensors to meet the urgent demands for accurate and fast detection of glucose in the fields of health care and environmental monitoring. In this work, an advanced nanostructured material based on the well-aligned CuO/Cu2S heteronanorods incorporated with P atoms is successfully synthesized on a copper substrate. The as-synthesized material shows high catalytic behavior accompanied by outstanding electrical conductivity. This, combined with the unique morphology of unstacked nanorod arrays, which endow the entire material with a greater number of exposed active sites, make the proposed material act as a highly efficient electrocatalyst for the glucose oxidation reaction. Density functional theory calculations demonstrate that P doping endows P-doped CuO/Cu2S with excellent electrical conductivity and glucose adsorption capability, significantly improving its catalytic performance. As a result, a non-enzymatic glucose sensor fabricated based on our proposed material exhibits a broad linear detection range (0.02-8.2 mM) and a low detection limit (0.95 µM) with a high sensitivity of 2.68 mA mM-1 cm-2 and excellent selectivity.

7.
Inorg Chem ; 62(41): 16691-16709, 2023 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-37791920

RESUMO

Tl2HgGeSe4 crystal was successfully, for the first time, synthesized by the Bridgman-Stockbarger technology, and its electronic structure and peculiarities of optical constants were investigated using both experimental and theoretical techniques. The present X-ray photoelectron spectroscopy measurements show that the Tl2HgGeSe4 crystal reveals small moisture sensitivity at ambient conditions and that the essential covalent constituent of the chemical bonding characterizes it. The latter suggestion was supported theoretically by ab initio calculations. The present experiments feature that the Tl2HgGeSe4 crystal is a high-resistance semiconductor with a specific electrical conductivity of σ ∼ 10-8 Ω-1 cm-1 (at 300 K). The crystal is characterized by p-type electroconductivity with an indirect energy band gap of 1.28 eV at room temperature. It was established that a good agreement with the experiments could be obtained when performing first-principles calculations using the modified Becke-Johnson functional as refined by Tran-Blaha with additional involvement in the calculating procedure of the Hubbard amendment parameter U and the impact of spin-orbit coupling (TB-mBJ + U + SO model). Under such a theoretical model, we have determined that the energy band gap of the Tl2HgGeSe4 crystal is equal to 1.114 eV, and this band gap is indirect in nature. The optical constants of Tl2HgGeSe4 are calculated based on the TB-mBJ + U + SO model.

8.
Chem Rev ; 123(16): 10206-10257, 2023 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-37523660

RESUMO

Using compressive mechanical forces, such as pressure, to induce crystallographic phase transitions and mesostructural changes while modulating material properties in nanoparticles (NPs) is a unique way to discover new phase behaviors, create novel nanostructures, and study emerging properties that are difficult to achieve under conventional conditions. In recent decades, NPs of a plethora of chemical compositions, sizes, shapes, surface ligands, and self-assembled mesostructures have been studied under pressure by in-situ scattering and/or spectroscopy techniques. As a result, the fundamental knowledge of pressure-structure-property relationships has been significantly improved, leading to a better understanding of the design guidelines for nanomaterial synthesis. In the present review, we discuss experimental progress in NP high-pressure research conducted primarily over roughly the past four years on semiconductor NPs, metal and metal oxide NPs, and perovskite NPs. We focus on the pressure-induced behaviors of NPs at both the atomic- and mesoscales, inorganic NP property changes upon compression, and the structural and property transitions of perovskite NPs under pressure. We further discuss in depth progress on molecular modeling, including simulations of ligand behavior, phase-change chalcogenides, layered transition metal dichalcogenides, boron nitride, and inorganic and hybrid organic-inorganic perovskites NPs. These models now provide both mechanistic explanations of experimental observations and predictive guidelines for future experimental design. We conclude with a summary and our insights on future directions for exploration of nanomaterial phase transition, coupling, growth, and nanoelectronic and photonic properties.

9.
RSC Adv ; 13(2): 881-887, 2023 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-36686945

RESUMO

The electronic and optical properties of an AgGaGeS4 crystal were studied by first-principles calculations, where the full-potential augmented plane-wave plus local orbital (APW+lo) method was used together with exchange-correlation pseudopotential described by PBE, PBE+U, and TB-mBJ+U approaches. To verify the correctness of the present theoretical calculations, we have measured for the AgGaGeS4 crystal the XPS valence-band spectrum and the X-ray emission bands representing the energy distribution of the electronic states with the biggest contributions in the valence-band region and compared them on a general energy scale with the theoretical results. Such a comparison indicates that, the calculations within the TB-mBJ+U approach reproduce the electron-band structure peculiarities (density of states - DOS) of the AgGaGeS4 crystal which are in fairly good agreement with the experimental data based on measurements of XPS and appropriate X-ray emission spectra. In particular, the DOS of the AgGaGeS4 crystal is characterized by the existence of well-separated peaks/features in the vicinity of -18.6 eV (Ga-d states) and around -12.5 eV and -7.5 eV, which are mainly composed by hybridized Ge(Ga)-s/p and S-p state. We gained good agreement between the experimental and theoretical data with respect to the main peculiarities of the energy distribution of the electronic S 3p, Ag 4d, Ga 4p and Ge 4p states, the main contributors to the valence band of AgGaGeS4. The bottom of the conduction band is mostly donated by unoccupied Ge-s states, with smaller contributions of unoccupied Ga-s, Ag-s and S-p states, too. The AgGaGeS4 crystal is almost transparent for visible light, but it strongly absorbs ultra-violet light where the significant polarization also occurs.

10.
RSC Adv ; 12(45): 29113-29123, 2022 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-36320756

RESUMO

The MXene SnSiGeN4 monolayer as a new member of the MoSi2N4 family was proposed for the first time, and its structural and electronic properties were explored by applying first-principles calculations with both PBE and hybrid HSE06 approaches. The layered hexagonal honeycomb structure of SnSiGeN4 was determined to be stable under dynamical effects or at room temperature of 300 K, with a rather high cohesive energy of 7.0 eV. The layered SnSiGeN4 has a Young's modulus of 365.699 N m-1 and a Poisson's ratio of 0.295. The HSE06 approach predicted an indirect band gap of around 2.4 eV for the layered SnSiGeN4. While the major donation from the N-p orbitals to the band structure makes SnSiGeN4's band gap close to those of similar 2D MXenes, the smaller distributions from the other orbitals of Sn, Si, and Ge slightly vary this band gap. The work functions of the GeN and SiN surfaces are 6.367 eV and 5.903 eV, respectively. The band gap of the layered SnSiGeN4 can be easily tuned by strain and an external electric field. A semiconductor-metal transition can occur at certain values of strain, and with an electric field higher than 5 V nm-1. The electron mobility of the layered SnSiGeN4 can reach up to 677.4 cm2 V-1 s-1, which is much higher than the hole mobility of about 52 cm2 V-1 s-1. The mentioned characteristics make the layered SnSiGeN4 a very promising material for use in electronic and photoelectronic devices, and for solar energy conversion.

11.
RSC Adv ; 12(40): 26418-26427, 2022 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-36275110

RESUMO

Exploring Heusler based materials for different practical applications has drawn more and more attention. In this work, the structural, electronic, magnetic, and mechanical properties of NaTMGe (TM = all 3d transition metals) half-Heusler compounds have been systematically investigated using first-principles calculations. The TM modification plays a determinant role in the fundamental properties. Except NaNiGe and NaCuGe, the studied materials exhibit good dynamical stability. Calculations reveal the non-magnetic semiconductor of NaScGe with a direct energy gap of 1.21 eV. Prospective spintronic applications of NaVGe and NaCrGe-NaMnGe are also suggested by their magnetic semiconductor and half-metallic behavior, respectively, where their magnetic properties follow the Slater-Pauling rule. Nevertheless, the remaining materials are either magnetic or non-magnetic metallic. For the magnetic systems, the magnetism is induced mainly by the TM constituents with either spin-up (V, Cr, Mn, and Fe) or spin-down (Co) 3d states. Calculated elastic constants indicate that all compounds are mechanically stable. Furthermore, they exhibit significant elastic anisotropy, where NaScGe and NaZnGe are the least and most anisotropic materials, respectively. Also, modifying the TM elements influences the materials' ductile and brittle behaviors. Our work unravels clearly the effects of TM modification on the fundamental properties of NaTMGe compounds. NaTMGe materials show excellent versatility with promising properties for optoelectronic and spintronic applications.

12.
RSC Adv ; 12(30): 19115-19121, 2022 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-35865616

RESUMO

In this work, we systematically examine the electronic features and contact types of van der Waals heterostructures (vdWHs) combining single-layer boron phosphide (BP) and Janus Ga2SSe using first-principles calculations. Owing to the out-of-plane symmetry being broken, the BP/Ga2SSe vdWHs are divided into two different stacking patterns, which are BP/SGa2Se and BP/SeGa2S. Our results demonstrate that these stacking patterns are structurally and mechanically stable. The combination of single-layer BP and Janus Ga2SSe gives rise to an enhancement in the Young's modulus compared to the constituent monolayers. Furthermore, at the ground state, the BP/Ga2SSe vdWHs possess a type-I (straddling) band alignment, which is desired for next-generation optoelectronic applications. The interlayer separation and electric field are effectively used to tune the electronic features of the BP/Ga2SSe vdWH from the type-I to type-II band alignment, and from semiconductor to metal. Our findings show that the BP/Ga2SSe vdWH would be appropriate for next-generation multifunctional optoelectronic and photovoltaic devices.

13.
Phys Chem Chem Phys ; 24(27): 16512-16521, 2022 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-35781308

RESUMO

We discuss and examine the stability, electronic properties, and transport characteristics of asymmetric monolayers XWGeN2 (X = O, S, Se, Te) using ab initio density functional theory. All four monolayers of quintuple-layer atomic Janus XWGeN2 are predicted to be stable and they are all indirect semiconductors in the ground state. When the spin-orbit coupling (SOC) is included, a large spin splitting at the K point is found in XWGeN2 monolayers, particularly, a giant Rashba-type spin splitting is observed around the Γ point in three structures SWGeN2, SeWGeN2, and TeWGeN2. The Rashba parameters in these structures are directionally isotropic along the high-symmetry directions Γ-K and Γ-M and the Rashba constant αR increases as the X element moves from S to Te. TeWGeN2 has the largest Rashba energy up to 37.4 meV (36.6 meV) in the Γ-K (Γ-M) direction. Via the deformation potential method, we calculate the carrier mobility of all four XWGeN2 monolayers. It is found that the electron mobilities of OWGeN2 and SWGeN2 monolayers exceed 200 cm2 V-1 s-1, which are suitable for applications in nanoelectronic devices.

14.
RSC Adv ; 12(26): 16677-16683, 2022 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-35754866

RESUMO

In this work, the effects of transition metal (TM = V and Cr) adsorption on AlN monolayer electronic and magnetic properties are investigated using first-principles density functional theory (DFT) calculations. TMs prefer to be adsorbed on-top of a bridge position as indicated by the calculated adsorption energy. V adatoms induce half-metallicity, while Cr adatoms metallize the monolayer. The magnetic properties are produced mainly by the V and Cr adatoms with magnetic moments of 3.72 and 4.53 µ B, respectively. Further investigation indicates that antiferromagnetic (AFM) ordering is energetically more favorable than ferromagnetic (FM) ordering. In both cases, the AFM state is stabilized upon increasing adatom coverage. The AlN monolayer becomes an AFM semiconductor with 0.5 ML of V adatom, and metallic nature is induced with 1.0 ML. Meanwhile, the degree of metallicity increases with increasing Cr adatoms. Results reported herein may provide a feasible new approach to functionalize AlN monolayers for spintronic applications.

15.
RSC Adv ; 12(21): 12971-12977, 2022 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-35497018

RESUMO

Due to the broken vertical symmetry, the Janus material possesses many extraordinary physico-chemical and mechanical properties that cannot be found in original symmetric materials. In this paper, we study in detail the structural, electronic, and transport properties of 1T Janus PdXO monolayers (X = S, Se, Te) by means of density functional theory. PdXO monolayers are observed to be stable based on the analysis of the vibrational characteristics and molecular dynamics simulations. All three PdXO structures exhibit semiconducting characteristics with indirect bandgap based on evaluations with hybrid functional Heyd-Scuseria-Ernzerhof (HSE06). The influences of the spin-orbit coupling (SOC) on the band diagram of PdXO are strong. Particularly, when the SOC is included, PdTeO is calculated to be metallic by the HSE06+SOC approach. With high electron mobility, Janus PdXO structures have good potential for applications in future nanodevices.

16.
Environ Res ; 212(Pt B): 113277, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-35461850

RESUMO

Road traffic constitutes a major source of air pollutants in urban Beijing, which are responsible for substantial premature mortality. A series of policies and regulations has led to appreciable traffic emission reductions in recent decades. To shed light on long-term (2014-2020) roadside air pollution and assess the efficacy of traffic control measures and their effects on public health, this study quantitatively evaluated changes in the concentrations of six key air pollutants (PM2.5, PM10, NO2, SO2, CO and O3) measured at 5 roadside and 12 urban background monitoring stations in Beijing. We found that the annual mean concentrations of these air pollutants were remarkably reduced by 47%-71% from 2014 to 2020, while the concurrent ozone concentration increased by 17.4%. In addition, we observed reductions in the roadside increments in PM2.5, NO2, SO2 and CO of 54.8%, 29.8%, 20.6%, and 59.1%, respectively, indicating the high effectiveness of new vehicle standard (China V and VI) implementation in Beijing. The premature deaths due to traffic emissions were estimated to be 8379 and 1908 cases in 2014 and 2020, respectively. The impact of NO2 from road traffic relative to PM2.5 on premature mortality was comparable to that of traffic-related PM2.5 emissions. The public health effect of SO2 originating from traffic was markedly lower than that of PM2.5. The results indicated that a reduction in traffic-related NO2 could likely yield the greatest benefits for public health.


Assuntos
Poluentes Atmosféricos , Poluição do Ar , Poluentes Atmosféricos/análise , Poluição do Ar/análise , Pequim , Monitoramento Ambiental/métodos , Dióxido de Nitrogênio , Material Particulado/análise , Saúde Pública
17.
RSC Adv ; 12(13): 7973-7979, 2022 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-35424776

RESUMO

In this paper, the structural, electronic, and transport properties of Janus GaInX3 (X = S, Se, Te) single-layers are investigated by a first-principles calculations. All three structures of GaInX3 are examined to be stable based on the analysis of their phonon dispersions, cohesive energy, and Born's criteria for mechanical stability. At the ground state, The Janus GaInX3 is a semiconductor in which its bandgap decreases as the chalcogen element X moves from S to Te. Due to the vertical asymmetric structure, a difference in the vacuum level between the two surfaces of GaInX3 is found, leading to work functions on the two sides being different. The Janus GaInX3 exhibit high directional isotropic transport characteristics. Particularly, GaInX3 single-layers have high electron mobility, which could make them potential materials for applications in electronic nanodevices.

18.
RSC Adv ; 12(17): 10249-10257, 2022 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-35425004

RESUMO

First-principles calculations were performed to study a novel layered SnGe2N4 compound, which was found to be dynamically and thermally stable in the 2H phase, with the space group P6̄m2 and lattice constant a = 3.143 Å. Due to its hexagonal structure, SnGe2N4 exhibits isotropic mechanical properties on the x-y plane, where the Young's modulus is 335.49 N m-1 and the Poisson's ratio is 0.862. The layered 2H SnGe2N4 is a semiconductor with a direct band gap of 1.832 eV, allowing the absorption of infrared and visible light at a rate of about 104 cm-1. The DOS is characterized by multiple high peaks in the valence and conduction bands, making it possible for this semiconductor to absorb light in the ultraviolet region with an even higher rate of 105 cm-1. The band structure, with a strongly concave downward conduction band and rather flat valence band, leads to a high electron mobility of 1061.66 cm2 V-1 s-1, which is substantially greater than the hole mobility of 28.35 cm2 V-1 s-1. This difference in mobility is favorable for electron-hole separation. These advantages make layered 2H SnGe2N4 a very promising photoelectric material. Furthermore, the electronic structure of 2H SnGe2N4 responds well to strain and an external electric field due to the specificity of the p-d hybridization, which predominantly constructs the valence bands. As a result, strain and external electric fields can efficiently tune the band gap value of 2H SnGe2N4, where compressive strain widens the band gap, meanwhile tensile strain and external electric fields cause band gap reduction. In particular, the band gap is decreased by about 0.25 eV when the electric field strength increases by 0.1 V Å-1, making a semiconductor-metal transition possible for the layered SnGe2N4.

19.
Polymers (Basel) ; 14(3)2022 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-35160531

RESUMO

Coarse-grained modeling methods allow simulations at larger scales than molecular dynamics, making it feasible to simulate multifluid systems. It is, however, critical to use model parameters that represent the fluid properties with fidelity under both equilibrium and dynamic conditions. In this work, dissipative particle dynamics (DPD) methods were used to simulate the flow of oil and water in a narrow slit under Poiseuille and Couette flow conditions. Large surfactant molecules were also included in the computations. A systematic methodology is presented to determine the DPD parameters necessary for ensuring that the boundary conditions were obeyed, that the oil and water viscosities were represented correctly, and that the velocity profile for the multifluid system agreed with the theoretical expectations. Surfactant molecules were introduced at the oil-water interface (sodium dodecylsulfate and octaethylene glycol monododecyl ether) to determine the effects of surface-active molecules on the two-phase flow. A critical shear rate was found for Poiseuille flow, beyond which the surfactants desorbed to form the interface forming micelles and destabilize the interface, and the surfactant-covered interface remained stable under Couette flow even at high shear rates.

20.
J Colloid Interface Sci ; 609: 158-169, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34894550

RESUMO

HYPOTHESIS: Janus particles (JPs) and surfactants express different behaviors at the oil-water interface under compression. When both are present at the interface, their synergies result in a different collapse mechanism than when present individually depending on the concentration of the JPs and surfactants. EXPERIMENTS: Coarse-grained modeling methods were used to probe the synergies between Janus nanoparticles and nonionic surfactants on the stability of an oil-water interface under compression. When both JPs and surfactants were present, the interface was covered at 0-55% area by JPs and contained surfactants at 0-40% of the interfacial surfactant concentration corresponding to the critical micelle concentration (CMC). FINDINGS: Compression of the interface with only surfactants resulted in the expulsion of surfactant molecules to the water phase once the interfacial concentration of surfactant molecules reached the CMC value. Compression of a Janus particle-laden interface past the closed-packing point led to a buckled interface, so that the total interfacial area remained constant upon further compression. When both surfactants and JPs were present on the interface, JPs still caused buckling, which helped retain the surfactant molecules on the interface. The interface exhibited a higher level of deformation in presence of surfactants. When the surfactant concentration was high, under compression, the surfactants partitioned into the water phase, but the buckling of the interface persisted.


Assuntos
Nanopartículas Multifuncionais , Tensoativos , Micelas , Pressão , Água
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA