Research

19 pages, 5562 KiB

Open AccessArticle

Properties Optimization of Polypropylene/Montmorillonite Nanocomposite Drawn Fibers

by Konstantinos Leontiadis, Katerina Theodoratou, Costas Tsioptsias and Ioannis Tsivintzelis

Nanomaterials 2024, 14(2), 223; https://doi.org/10.3390/nano14020223 - 19 Jan 2024

Viewed by 617

In this study, the mechanical properties and thermal stability of composite polypropylene (PP) drawn fibers with two different organically modified montmorillonites were experimentally investigated and optimized using a response surface methodology. Specifically, the Box-Behnken Design of Experiments method was used in order to [...] Read more.

In this study, the mechanical properties and thermal stability of composite polypropylene (PP) drawn fibers with two different organically modified montmorillonites were experimentally investigated and optimized using a response surface methodology. Specifically, the Box-Behnken Design of Experiments method was used in order to investigate the effect of the filler content, the compatibilizer content, and the drawing temperature on the tensile strength and the onset decomposition temperature of the PP composite drawn fibers. The materials were characterized by tensile tests, thermogravimetry, and X-ray diffraction. Two types of composites were investigated with the only difference being the type of filler, namely, Cloisite^® 10A or Cloisite^® 15A. In both cases, statistically significant models were obtained regarding the effect of design variables on tensile strength, while poor significance was observed for the onset decomposition temperature. Nanocomposite fibers with tensile strength up to 540 MPa were obtained. Among the design variables, the drawing temperature exhibited the most notable effect on tensile strength, while the effect of both clays was not significant. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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24 pages, 6549 KiB

Open AccessArticle

Design of Polymer Nanodielectrics for Capacitive Energy Storage

by Prajakta Prabhune, Yigitcan Comlek, Abhishek Shandilya, Ravishankar Sundararaman, Linda S. Schadler, Lynda Catherine Brinson and Wei Chen

Nanomaterials 2023, 13(17), 2394; https://doi.org/10.3390/nano13172394 - 22 Aug 2023

Cited by 1 | Viewed by 1348

Abstract

Polymer nanodielectrics present a particularly challenging materials design problem for capacitive energy storage applications like polymer film capacitors. High permittivity and breakdown strength are needed to achieve high energy density and loss must be low. Strategies that increase permittivity tend to decrease the [...] Read more.

Polymer nanodielectrics present a particularly challenging materials design problem for capacitive energy storage applications like polymer film capacitors. High permittivity and breakdown strength are needed to achieve high energy density and loss must be low. Strategies that increase permittivity tend to decrease the breakdown strength and increase loss. We hypothesize that a parameter space exists for fillers of modest aspect ratio functionalized with charge-trapping molecules that results in an increase in permittivity and breakdown strength simultaneously, while limiting increases in loss. In this work, we explore this parameter space, using physics-based, multiscale 3D dielectric property simulations, mixed-variable machine learning and Bayesian optimization to identify the compositions and morphologies which lead to the optimization of these competing properties. We employ first principle-based calculations for interface trap densities which are further used in breakdown strength calculations. For permittivity and loss calculations, we use continuum scale modelling and finite difference solution of Poisson’s equation for steady-state currents. We propose a design framework for optimizing multiple properties by tuning design variables including the microstructure and interface properties. Finally, we employ mixed-variable global sensitivity analysis to understand the complex interplay between four continuous microstructural and two categorical interface choices to extract further physical knowledge on the design of nanodielectrics. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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25 pages, 15190 KiB

Open AccessArticle

The Effect of Nano Zirconium Dioxide (ZrO₂)-Optimized Content in Polyamide 12 (PA12) and Polylactic Acid (PLA) Matrices on Their Thermomechanical Response in 3D Printing

by Markos Petousis, Amalia Moutsopoulou, Apostolos Korlos, Vassilis Papadakis, Nikolaos Mountakis, Dimitris Tsikritzis, Ioannis Ntintakis and Nectarios Vidakis

Nanomaterials 2023, 13(13), 1906; https://doi.org/10.3390/nano13131906 - 21 Jun 2023

Cited by 5 | Viewed by 1288

Abstract

The influence of nanoparticles (NPs) in zirconium oxide (ZrO₂) as a strengthening factor of Polylactic Acid (PLA) and Polyamide 12 (PA12) thermoplastics in material extrusion (MEX) additive manufacturing (AM) is reported herein for the first time. Using a melt-mixing compounding method, [...] Read more.

The influence of nanoparticles (NPs) in zirconium oxide (ZrO₂) as a strengthening factor of Polylactic Acid (PLA) and Polyamide 12 (PA12) thermoplastics in material extrusion (MEX) additive manufacturing (AM) is reported herein for the first time. Using a melt-mixing compounding method, zirconium dioxide nanoparticles were added at four distinct filler loadings. Additionally, 3D-printed samples were carefully examined for their material performance in various standardized tests. The unfilled polymers were the control samples. The nature of the materials was demonstrated by Raman spectroscopy and thermogravimetric studies. Atomic Force Microscopy and Scanning Electron Microscopy were used to comprehensively analyze their morphological characteristics. Zirconium dioxide NPs showed an affirmative reinforcement tool at all filler concentrations, while the optimized material was calculated with loading in the range of 1.0–3.0 wt.% (3.0 wt.% for PA12, 47.7% increase in strength; 1.0 wt.% for PLA, 20.1% increase in strength). PA12 and PLA polymers with zirconium dioxide in the form of nanocomposite filaments for 3D printing applications could be used in implementations using thermoplastic materials in engineering structures with improved mechanical behavior. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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20 pages, 7002 KiB

Open AccessArticle

Morphology and Dynamics in Hydrated Graphene Oxide/Branched Poly(ethyleneimine) Nanocomposites: An In Silico Investigation

by Anastassia Rissanou, Apostolos Konstantinou and Kostas Karatasos

Nanomaterials 2023, 13(12), 1865; https://doi.org/10.3390/nano13121865 - 15 Jun 2023

Cited by 2 | Viewed by 867

Abstract

Graphene oxide (GO)—branched poly(ethyleneimine) (BPEI) hydrated mixtures were studied by means of fully atomistic molecular dynamics simulations to assess the effects of the size of polymers and the composition on the morphology of the complexes, the energetics of the systems and the dynamics [...] Read more.

Graphene oxide (GO)—branched poly(ethyleneimine) (BPEI) hydrated mixtures were studied by means of fully atomistic molecular dynamics simulations to assess the effects of the size of polymers and the composition on the morphology of the complexes, the energetics of the systems and the dynamics of water and ions within composites. The presence of cationic polymers of both generations hindered the formation of stacked GO conformations, leading to a disordered porous structure. The smaller polymer was found to be more efficient at separating the GO flakes due to its more efficient packing. The variation in the relative content of the polymeric and the GO moieties provided indications for the existence of an optimal composition in which interaction between the two components was more favorable, implying more stable structures. The large number of hydrogen-bonding donors afforded by the branched molecules resulted in a preferential association with water and hindered its access to the surface of the GO flakes, particularly in polymer-rich systems. The mapping of water translational dynamics revealed the existence of populations with distinctly different mobilities, depending upon the state of their association. The average rate of water transport was found to depend sensitively on the mobility of the freely to move molecules, which was varied strongly with composition. The rate of ionic transport was found to be very limited below a threshold in terms of polymer content. Both, water diffusivity and ionic transport were enhanced in the systems with the larger branched polymers, particularly with a lower polymer content, due to the higher availability of free volume for the respective moieties. The detail afforded in the present work provides a new insight for the fabrication of BPEI/GO composites with a controlled microstructure, enhanced stability and adjustable water transport and ionic mobility. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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15 pages, 2762 KiB

Open AccessArticle

Non-Isothermal Crystallization Kinetics of Montmorillonite/Polyamide 610 Nanocomposites

by Yang Fu, Cuimeng Huo, Shuangyan Liu, Keqing Li and Yuezhong Meng

Nanomaterials 2023, 13(12), 1814; https://doi.org/10.3390/nano13121814 - 06 Jun 2023

Viewed by 890

Abstract

Non-isothermal crystallization kinetics of montmorillonite (MMT)/polyamide 610 (PA610) composites were readily prepared by in situ melt polymerization followed by a full investigation in terms of their microstructure, performance, and crystallization kinetics. The kinetic models of Jeziorny, Ozawa, and Mo were used in turn [...] Read more.

Non-isothermal crystallization kinetics of montmorillonite (MMT)/polyamide 610 (PA610) composites were readily prepared by in situ melt polymerization followed by a full investigation in terms of their microstructure, performance, and crystallization kinetics. The kinetic models of Jeziorny, Ozawa, and Mo were used in turn to fit the experimental data, in all of which Mo’s analytical method was found to be the best model for the kinetic data. Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) studies were used to investigate the isothermal crystallization behavior and MMT dispersion levels in the MMT/PA610 composites. The experiment results revealed that low MMT content can promote the PA610 crystallization, whilst high MMT content result in MMT agglomeration, and reduce the PA610 crystallization rate. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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20 pages, 6472 KiB

Open AccessArticle

Polyvinyl Alcohol Assisted Iron–Zinc Nanocomposite for Enhanced Optimized Rapid Removal of Malachite Green Dye

by Muhammad Saad, Hajira Tahir, Seher Mustafa, Osama A. Attala, Waleed A. El-Saoud, Kamal A. Attia, Wessam M. Filfilan and Jahan Zeb

Nanomaterials 2023, 13(11), 1747; https://doi.org/10.3390/nano13111747 - 26 May 2023

Cited by 5 | Viewed by 1125

Abstract

Eliminating hazardous contaminants is a necessity for maintaining a healthy environment on Earth. This work used a sustainable method to create Iron–Zinc nanocomposites with polyvinyl alcohol assistance. Mentha Piperita (mint leaf) extract was used as a reductant in the green synthesis of bimetallic [...] Read more.

Eliminating hazardous contaminants is a necessity for maintaining a healthy environment on Earth. This work used a sustainable method to create Iron–Zinc nanocomposites with polyvinyl alcohol assistance. Mentha Piperita (mint leaf) extract was used as a reductant in the green synthesis of bimetallic nanocomposites. Doping with Poly Vinyl Alcohol (PVA) caused a reduction in crystallite size and greater lattice parameters. XRD, FTIR, EDS, and SEM techniques were used to establish their surface morphology and structural characterization. The high-performance nanocomposites were used to remove malachite green (MG) dye using the ultrasonic adsorption technique. Adsorption experiments were designed by central composite design and optimized by response surface methodology. According to this study, 77.87% of the dye was removed at the optimum optimized parameters (10.0 mg L⁻¹ was the concentration of MG dye at a time of 8.0 min, pH 9.0, and 0.02 g of adsorbent amount) with adsorption capacity up to 92.59 mg·g⁻¹. The dye adsorption followed Freundlich’s isotherm model and the pseudo-second-order kinetic model. Thermodynamic analysis affirmed the spontaneous nature of adsorption due to negative ΔG^o values. As a result, the suggested approach offers a framework for creating an effective and affordable technique to remove the dye from a simulated wastewater system for environmental conservation. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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26 pages, 9683 KiB

Open AccessArticle

Optimizing the Rheological and Thermomechanical Response of Acrylonitrile Butadiene Styrene/Silicon Nitride Nanocomposites in Material Extrusion Additive Manufacturing

by Markos Petousis, Nikolaos Michailidis, Vassilis M. Papadakis, Apostolos Korlos, Nikolaos Mountakis, Apostolos Argyros, Evgenia Dimitriou, Chrysa Charou, Amalia Moutsopoulou and Nectarios Vidakis

Nanomaterials 2023, 13(10), 1588; https://doi.org/10.3390/nano13101588 - 09 May 2023

Cited by 12 | Viewed by 2093

Abstract

The current research aimed to examine the thermomechanical properties of new nanocomposites in additive manufacturing (AM). Material extrusion (MEX) 3D printing was utilized to evolve acrylonitrile butadiene styrene (ABS) nanocomposites with silicon nitride nano-inclusions. Regarding the mechanical and thermal response, the fabricated 3D-printed [...] Read more.

The current research aimed to examine the thermomechanical properties of new nanocomposites in additive manufacturing (AM). Material extrusion (MEX) 3D printing was utilized to evolve acrylonitrile butadiene styrene (ABS) nanocomposites with silicon nitride nano-inclusions. Regarding the mechanical and thermal response, the fabricated 3D-printed samples were subjected to a course of standard tests, in view to evaluate the influence of the Si₃N₄ nanofiller content in the polymer matrix. The morphology and fractography of the fabricated filaments and samples were examined using scanning electron microscopy and atomic force microscopy. Moreover, Raman and energy dispersive spectroscopy tests were accomplished to evaluate the composition of the matrix polymer and nanomaterials. Silicon nitride nanoparticles were proved to induce a significant mechanical reinforcement in comparison with the polymer matrix without any additives or fillers. The optimal mechanical response was depicted to the grade ABS/Si₃N₄ 4 wt. %. An impressive increase in flexural strength (30.3%) and flexural toughness (47.2%) was found. The results validate that these novel ABS nanocomposites with improved mechanical properties can be promising materials. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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15 pages, 2973 KiB

Open AccessArticle

Positive and Negative Changes in the Electrical Conductance Related to Hybrid Filler Distribution Gradient in Composite Flexible Thermoelectric Films Subjected to Bending

by Lasma Bugovecka, Krisjanis Buks, Jana Andzane, Annija Dinija Miezubrale, Juris Bitenieks, Janis Zicans and Donats Erts

Nanomaterials 2023, 13(7), 1212; https://doi.org/10.3390/nano13071212 - 29 Mar 2023

Cited by 5 | Viewed by 996

Abstract

P-type multiwalled carbon nanotubes (MWCNTs), as well as heterostructures fabricated by direct deposition of inorganic thermoelectric materials as antimony and bismuth chalcogenides on MWCNT networks are known as perspective materials for application in flexible thermoelectric polymer-based composites. In this work, the electrical response [...] Read more.

P-type multiwalled carbon nanotubes (MWCNTs), as well as heterostructures fabricated by direct deposition of inorganic thermoelectric materials as antimony and bismuth chalcogenides on MWCNT networks are known as perspective materials for application in flexible thermoelectric polymer-based composites. In this work, the electrical response of three types of Sb₂Te₃-MWCNT heterostructures-based flexible films—free standing on a flexible substrate, encapsulated in polydimethylsiloxane (PDMS), and mixed in polyvinyl alcohol (PVA) is studied in comparison with the flexible films prepared by the same methods using bare MWCNTs. The electrical conductance of these films when each side of it was subsequently subjected to compressive and tensile stress during the film bending down to a 3 mm radius is investigated in relation to the distribution gradient of Sb₂Te₃-MWCNT heterostructures or bare MWCNTs within the film. It is found that all investigated Sb₂Te₃-MWCNT films exhibit a reversible increase in the conductance in response to the compressive stress of the film side with the highest filler concentration and its decrease in response to the tensile stress. In contrast, free-standing and encapsulated bare MWCNT networks with uniform distribution of nanotubes showed a decrease in the conductance irrelevant to the bending direction. In turn, the samples with the gradient distribution of the MWCNTs, prepared by mixing the MWCNTs with PVA, revealed behavior that is similar to the Sb₂Te₃-MWCNT heterostructures-based films. The analysis of the processes impacting the changes in the conductance of the Sb₂Te₃-MWCNT heterostructures and bare MWCNTs is performed. The proposed in this work bending method can be applied for the control of the uniformity of distribution of components in heterostructures and fillers in polymer-based composites. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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10 pages, 2215 KiB

Open AccessArticle

Magnetic Nanocomposites for the Remote Activation of Sulfate Radicals for the Removal of Rhodamine B

by Pranto Paul, Marissa Nicholson and J. Zach Hilt

Nanomaterials 2023, 13(7), 1151; https://doi.org/10.3390/nano13071151 - 23 Mar 2023

Viewed by 1201

Abstract

The widespread presence of numerous organic contaminants in water poses a threat to the ecological environment and human health. Magnetic nanocomposites exposed to an alternating magnetic field (AMF) have a unique ability for magnetically mediated energy delivery (MagMED) resulting from the embedded magnetic [...] Read more.

The widespread presence of numerous organic contaminants in water poses a threat to the ecological environment and human health. Magnetic nanocomposites exposed to an alternating magnetic field (AMF) have a unique ability for magnetically mediated energy delivery (MagMED) resulting from the embedded magnetic nanoparticles; this localized energy delivery and associated chemical and thermal effects are a potential method for removing contaminants from water. This work developed a novel magnetic nanocomposite—a polyacrylamide-based hydrogel loaded with iron oxide nanoparticles. For this magnetic nanocomposite, persulfate activation and the contamination removal in water were investigated. Magnetic nanocomposites were exposed to AMF with a model organic contaminant, rhodamine B (RhB) dye, with or without sodium persulfate (SPS). The removal of RhB by the nanocomposite without SPS as a sorbent was found to be proportional to the concentration of magnetic nanoparticles (MNPs) in the nanocomposite. With the addition of SPS, approximately 100% of RhB was removed within 20 min. This removal was attributed primarily to the activation of sulfate radicals, triggered by MNPs, and the localized heating resulted from the MNPs when exposed to AMF. This suggests that this magnetic nanocomposite and an AMF could be a unique environmental remediation technique for hazardous contaminants. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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11 pages, 2768 KiB

Open AccessArticle

Cooking Delicacy with Ice—Nanobubble Isolation Switches Stewing to ‘BBQ’

by Qiankang Si, Ruoyang Zhao, Feng Gao, Jun Guo, Feng Zhang and Liping Wang

Nanomaterials 2023, 13(3), 562; https://doi.org/10.3390/nano13030562 - 30 Jan 2023

Viewed by 1471

Abstract

The key role of ice in cooking has been neglected. Here, we found negatively charged bulk nanobubbles (BNBs: average size ~60 nm and zeta potential <−20 mV) can be generated in ice-melted water through freeze/thaw-induced cavitation when we studied a local delicacy, ‘ice-stewed [...] Read more.

The key role of ice in cooking has been neglected. Here, we found negatively charged bulk nanobubbles (BNBs: average size ~60 nm and zeta potential <−20 mV) can be generated in ice-melted water through freeze/thaw-induced cavitation when we studied a local delicacy, ‘ice-stewed mutton’. Freeze/thaw-induced BNBs are so robust that they can, in turn, isolate food from water; in this way, they protect and enhance the delicacy by protecting protein structures and preventing flavorful components from being lost. In comparison to cooking with ordinary water, cooking with ice can switch ‘stewing’ to ‘BBQ’, which has been proved experimentally via diverse characterization from the nano to micro scale. This study not only provides a novel mechanism for ice-based cooking but also might shed light on the design of potential applications of BNBs in chemical engineering and biomedicine. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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13 pages, 2548 KiB

Open AccessArticle

Modeling the Additive Effects of Nanoparticles and Polymers on Hydrogel Mechanical Properties Using Multifactor Analysis

by Emma Barrett-Catton, Kyle Pedersen, Maryam Mobed-Miremadi and Prashanth Asuri

Nanomaterials 2022, 12(24), 4461; https://doi.org/10.3390/nano12244461 - 15 Dec 2022

Cited by 1 | Viewed by 1163

Abstract

Interpenetrating networks (IPN)s have been conceived as a biomimetic tool to tune hydrogel mechanical properties to the desired target formulations. In this study, the rheological behavior of acrylamide (AAm) [2.5–10%] hydrogels crosslinked with N,N′-methylenebis(acrylamide) (Bis) [0.0625–0.25%] was characterized in terms of the saturation [...] Read more.

Interpenetrating networks (IPN)s have been conceived as a biomimetic tool to tune hydrogel mechanical properties to the desired target formulations. In this study, the rheological behavior of acrylamide (AAm) [2.5–10%] hydrogels crosslinked with N,N′-methylenebis(acrylamide) (Bis) [0.0625–0.25%] was characterized in terms of the saturation modulus affected by the interaction of silica nanoparticle (SiNP) nanofillers [0–5%] and dextran [0–2%] at a frequency of 1 Hz and strain rate of 1% after a gelation period of 90 min. For single-network hydrogels, a prominent transition was observed at 0.125% Bis for 2.5% AAm and 0.25% Bis for 5% AAm across the SiNP concentrations and was validated by retrospective 3-level factorial design models, as characterized by deviation from linearity in the saturation region (R² = 0.86). IPN hydrogels resulting from the addition of dextran to the single network in the pre-saturation region, as outlined by the strong goodness of fit (R²= 0.99), exhibited a correlated increase in the elastic (G’) and viscous moduli (G”). While increasing the dextran concentrations [0–2%] and MW [100 kDa and 500 kDa] regulated the increase in G’, saturation in G” or the loss tangent (tan(δ)) was not recorded within the observed operating windows. Results of multifactor analysis conducted on Han plots in terms of the elastic gains indicate that amongst the factors modulating the viscoelasticity of the IPN hydrogels, dextran concentration is the most important (R_Dex = 35.3 dB), followed by nanoparticle concentration (R_SiNP = 7.7 dB) and dextran molecular weight (R_MW = 2.9 dB). The results demonstrate how the Han plot may be systematically used to quantify the main effects of intensive thermodynamic properties on rheological phase transition in interpenetrating networks where traditional multifactor analyses cannot resolve statistical significance. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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13 pages, 3108 KiB

Open AccessArticle

Molecular Dynamics Simulations on the Elastic Properties of Polypropylene Bionanocomposite Reinforced with Cellulose Nanofibrils

by Vaibhav Modi and Antti J. Karttunen

Nanomaterials 2022, 12(19), 3379; https://doi.org/10.3390/nano12193379 - 27 Sep 2022

Cited by 2 | Viewed by 1843

Abstract

Cellulose-reinforced polypropylene bionanocomposites can show improved elastic properties over their pure polypropylene counterparts. We have used equilibrium and non-equilibrium molecular dynamics (MD) simulations to study the elastic properties of polypropylene bionanocomposite systems composed of cellulose nanofibrils (CNF), polypropylene (PP) matrix, and maleic anhydride [...] Read more.

Cellulose-reinforced polypropylene bionanocomposites can show improved elastic properties over their pure polypropylene counterparts. We have used equilibrium and non-equilibrium molecular dynamics (MD) simulations to study the elastic properties of polypropylene bionanocomposite systems composed of cellulose nanofibrils (CNF), polypropylene (PP) matrix, and maleic anhydride (MAH) coupling agent. The components of the bionanocomposite were parametrized for compatibility with the AMBER14SB force fields. The elastic properties of pure PP systems converge for the chains with at least 20 monomers. The ratio of cellulose in CNF-PP bionanocomposites strongly affects their elastic properties. The elastic modulus of CNF-PP bionanocomposites shows small improvement when the adhesion between hydrophobic and hydrophilic components is facilitated by a MAH coupling agent. The results demonstrate how fully-atomistic MD simulations can be systematically used to evaluate the elastic properties of CNF-PP bionanocomposites and to make predictions that are in agreement with experiments. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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13 pages, 2917 KiB

Open AccessCommunication

From Bubbles to Nanobubbles

by George Z. Kyzas and Athanasios C. Mitropoulos

Nanomaterials 2021, 11(10), 2592; https://doi.org/10.3390/nano11102592 - 01 Oct 2021

Cited by 16 | Viewed by 2890

Abstract

Nanobubbles are classified into surface and bulk. The main difference between them is that the former is immobile, whereas the latter is mobile. The existence of sNBs has already been proven by atomic force microscopy, but the existence of bNBs is still open [...] Read more.

Nanobubbles are classified into surface and bulk. The main difference between them is that the former is immobile, whereas the latter is mobile. The existence of sNBs has already been proven by atomic force microscopy, but the existence of bNBs is still open to discussion; there are strong indications, however, of its existence. The longevity of NBs is a long-standing problem. Theories as to the stability of sNBs reside on their immobile nature, whereas for bNBs, the landscape is not clear at the moment. In this preliminary communication, we explore the possibility of stabilizing a bNB by Brownian motion. It is shown that a fractal walk under specific conditions may leave the size of the bubble invariant. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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10 pages, 3058 KiB

Open AccessArticle

Revealing the Hemispherical Shielding Effect of SiO₂@Ag Composite Nanospheres to Improve the Surface Enhanced Raman Scattering Performance

by Fengyan Wang, Daxue Du, Shan Liu, Linna Wang, Tifeng Jiao, Zhaopeng Xu and Haiyan Wang

Nanomaterials 2021, 11(9), 2209; https://doi.org/10.3390/nano11092209 - 27 Aug 2021

Cited by 8 | Viewed by 2252

Abstract

Many studies widely used SiO₂@Ag composite nanospheres for surface enhanced Raman scattering (SERS), which mainly contributes to electromagnetic enhancement. In addition to experiments, previous simulations mostly adopted a two-dimensional model in SERS research, resulting in the three-dimensional information being [...] Read more.

Many studies widely used SiO₂@Ag composite nanospheres for surface enhanced Raman scattering (SERS), which mainly contributes to electromagnetic enhancement. In addition to experiments, previous simulations mostly adopted a two-dimensional model in SERS research, resulting in the three-dimensional information being folded and masked. In this paper, we adopted the three-dimensional model to simulate the electric field distribution of SiO₂@Ag composite nanospheres. It is found that when the Ag nanoparticles are distributed densely on the surface of SiO₂ nanospheres, light cannot pass through the upper hemisphere due to the local surface plasmon resonance (LSPR) of the Ag nanoparticles, resulting in the upper hemisphere shielding effect; and if there are no Ag nanoparticles distributed densely on the surface of SiO₂ nanospheres, the strong LSPR cannot be formed, so the incident light will be guided downward through the whispering gallery mode of the spherical structure. At the same time, we designed relevant experiments to synthesize SiO₂@Ag composite nanosphere as SERS substrate and used Rhodamine 6G as a probe molecule to study its SERS performance. This design achieved a significant SERS effect, and is very consistent with our simulation results. Full article

(This article belongs to the Special Issue Polymer Based Nanocomposites: Experiment, Theory and Simulations)

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