Nanoparticle Networks Research Articles

Nonmonotonic Variation of Rutting Resistance and Fatigue Life for Polyethylene Modified Bitumen with Different Carbon Black Loading

Polyethylene (PE) and carbon black (CB) were premixed in this study for bitumen modification. The service performance of PE/CB-modified bitumen (PMB) was mainly explored by multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS) tests to reveal the rutting resistance and fatigue life, respectively. Low-temperature properties were evaluated by glass transition temperature (Tg) measured by dynamic mechanical analysis (DMA). X-ray diffraction (XRD) results suggested that the crystalline structure of PE was almost the same regardless of different CB loading additions. It was found that the both rutting resistance and fatigue life of PMBs showed nonmonotonic variation with CB loading. The mechanism for this variation was closely related to the microstructure induced by phase separation, CB nanoparticle aggregation and PE crystallinity. As revealed by optical and atomic force microscopy, two different phase structures, network and droplet-matrix structure, can be formed in PMBs when the CB loading changes. In particular, a double percolated network structure can be formed, consisting of a PE-rich network in the bitumen-matrix and CB nanoparticle network within a PE-rich phase. With the presence of this structure, the rutting resistance and fatigue life of PMB can be significantly improved.

Metal organic framework supported surface modification of synthesized nickel/nickel oxide nanoparticles via controlled PEGylation for cytotoxicity profile against MCF-7 breast cancer cell lines via docking analysis

Metal organic framework, (MOFs) supported nanoparticles have proven a path for the treatment of various carcinomas to be effective against MCF-7 Breast cancer cell lines. Despite the globally widespread applications of nickel/nickel oxide nanoparticles, Ni/NiO@LAA_PEG NPs with surfactant Polyethylene glycol, (PEG) and l-Acsorbic acid, (LAA) as reducing agents in industrial, commercial, and biomedical fields, their response to human cells has not been elucidated. Hence in the reported article Ni/NiO@LAA_PEG NPs with an average size range of 75–80 nm was used to study their interaction with MCF-7 Breast cancer cell lines. So the best of our understanding this is the study related to MCF-7 Human Breast cancer cell lines to show cyto-genotoxicity of Ni/NiO@LAA_PEG NPs which seems mediated through MTT analysis with rising effect surface enhancement and indexed porosiveness for the interfacial advancement than standard drug Doxorubicin for their comparison to show their best effectivity to prepared Ni/NiO@LAA_PEG NPs.The theoretical performance was simulated using Gaussian-09@Autodock 4.2 with crystal preparation and docked with MCF-7 Human Breast cancer cell lines PDBs to show their correlation with wet method of preparation. The synthesized Ni/NiO@LAA_PEG NPs was characterized against UV/Vis spectroscopy for determination of peak pattern of 395 nm, the functional group analysis for the best binding of stretching with framed metal network of nanoparticles was to shown out their scissoring, wagging, and CH stretching, etc. at 661, 834 and 3425 cm−1respectively by FTIR analysis and an energy band gap of 2.2 eV for Ni/NiO@LAA_PEG NPs by optical studies. The mesopore range and surface area measurement was calculated with BET adsorption and BJH plot to find their coercivity and retentivity via adsorption-desorption curve for their best catalytic performance. The current interpretation of Ni 2p spectra of oxides and other compounds is based on charge transfer assignment of the main peak at 856.4 eV and broad satellite cantered at about 861 eV to the cd9 L and unscreened cd8 final state configurations.

Strain-Insensitive Stretchable Fiber Conductors Based on Highly Conductive Buckled Shells for Wearable Electronics.

Based on their high applicability to wearable electronics, fiber-based stretchable electronics have been developed via different strategies. However, the electrical conductivity of a fiber electrode is severely degraded, following deformation upon stretching. Despite the introduction of conductive buckled structures to resolve this issue, there still exist limitations regarding the simultaneous realizations of high conductivity and stretchability. Here, we exploit the dense distribution of the Ag nanoparticle (AgNP) network in polyurethane (PU) to fabricate a strain-insensitive stretchable fiber conductor comprising highly conductive buckled shells via a facile chemical process. These buckled AgNPs/PU fibers exhibit stable and reliable electrical responses across a wide range (tensile strain = ∼200%), in addition to their high electrical conductivity (26,128 S/m) and quality factor (Q = 2.29). Particularly, the negligible electrical hysteresis and excellent durability (>10,000 stretching-releasing cycles) of the fibers demonstrate their high applicability to wearable electronics. Furthermore, we develop buckled fiber-based pH sensors exhibiting stable, repeatable, and highly distinguishable responses (changing pH is from 4 to 8, response time is 5-6 s) even under 100% tensile strain. The buckled AgNPs/PU fibers represent a facile strategy for maintaining the stable electrical performances of fiber electrodes across the strain range of human motion for wearable applications.

Dual Origin of Viscoelasticity in Polymer-Carbon Black Hydrogels: A Rheometry and Electrical Spectroscopy Study

Nanocomposites formed by mixing nanoparticles and polymers offer a limitless creative space for the design of functional advanced materials with a broad range of applications in materials and biological sciences. Here we focus on aqueous dispersions of hydrophobic colloidal soot particles, namely carbon black (CB) dispersed with a sodium salt of carboxymethylcellulose (CMC), a food additive known as cellulose gum that bears hydrophobic groups, which are liable to bind physically to CB particles. Varying the relative content of CB nanoparticles and cellulose gum allows us to explore a rich phase diagram that includes a gel phase. We investigate this hydrogel using rheometry and electrochemical impedance spectroscopy. CB-CMC hydrogels display two radically different types of mechanical behaviors that are separated by a critical CMC-to-CB mass ratio $r_c$. For $r<r_c$, i.e., for low CMC concentration, the gel is electrically conductive and shows a glassy-like viscoelastic spectrum, pointing to a microstructure composed of a percolated network of CB nanoparticles decorated by CMC. In contrast, gels with CMC concentration larger than $r_c$ are non-conductive, indicating that the CB nanoparticles are dispersed in the cellulose gum matrix as isolated clusters, and act as physical crosslinkers of the CMC network, hence providing mechanical rigidity to the composite. Moreover, in the concentration range, $r>r_c$ CB-CMC gels display a power-law viscoelastic spectrum that depends strongly on the CMC concentration. These relaxation spectra can be rescaled onto a master curve that exhibits a power-law scaling in the high-frequency limit, with an exponent that follows Zimm theory, showing that CMC plays a key role in the gel viscoelastic properties for $r>r_c$. Our results offer a characterization of CB-CMC dispersions that will be useful for designing nanocomposites based on hydrophobic interactions.

Oxygen Vacancies Engineering in Thick Semiconductor Films via Deep Ultraviolet Photoactivation for Selective and Sensitive Gas Sensing

AbstractRoom‐temperature detection of volatile organic compounds in particle‐per‐billion concentrations is critical for the development of wearable and distributed sensor networks. However, sensitivity and selectivity are limited at low operating temperatures. Here, a strategy is proposed to substantially improve the performance of semiconductor sensors. Tunable oxygen vacancies in thick 3D networks of metal oxide nanoparticles are engineered using deep ultraviolet photoactivation. High selectivity and sensitivity are achieved by optimizing the electronic structure and surface activity while preserving the 3D morphology. Cross‐sectional depth analysis reveals oxygen vacancies present at various depths (≈24% at a depth of 1.13 µm), with a uniform distribution throughout the thick films. This results in ≈58% increase in the sensitivity of ZnO to 20‐ppb ethanol at room temperature while ≈51% and 64% decrease in the response and recovery times, respectively. At an operating temperature of 150 °C, oxygen‐vacant nanostructures achieve a lower limit of detection of 2 ppb. Density functional theory analysis shows that inducing oxygen vacancies reduces activation energy for ethanol adsorption and dissociation, leading to improved sensing performance. This scalable approach has the potential for designing low‐power wearable chemical and bio‐sensors and tuning the activity and band structure of porous, thick oxide films for multiple applications.

Fractal-like gold nanonetworks formed by templated electrodeposition through 3D-mesoporous silica films.

Fractal-like networks of gold nanoparticles created by templated electrodeposition are described. Templated electrodeposition is a powerful and efficient technique for the bottom-up fabrication of nanostructures which can effectively control the size and shape of the electrodeposits. In this work, mesoporous silica films with highly ordered mesopores and three-dimensional mesostructure are synthesised and are used as templates for the electrodeposition of gold nanoparticles. The mesoporous silica films have small mesopores (∼8 nm) and complex mesopore channels (Fmmm structure with the [0 1 0] axis perpendicular to the substrate). A variety of nucleation conditions were applied to investigate their effect on the nanoparticles' arrangement and growth in templated electrodeposition. The electrodeposited gold particles are characterised by electron microscopy and grazing incidence small-angle X-ray scattering (GISAXS). GISAXS shows changes in the lattice parameters of the mesostructure after gold electrodeposition that relate to dimensional changes in directions linked to the shortest distances between the main spherical pores. Top-view SEM shows large areas of gold nanoparticles were deposited into the film and they were growing towards the surface. After removing the silica film templates, the gold nanoparticles display interesting fractal morphologies: the linked gold nanonetworks form a branched structure. The lengths of branches vary from the applied nucleation deposition conditions. Generally, with increasing nucleation time, fractal gold nanoparticles with longer branches are more likely to be obtained.

Probing into the physicochemical consequences of pristine and X0.06Ni0.94O (X = Co, Fe, Cu) nanoparticles for bactericidal, antifungal and hemolytic competency

Nano-scaled transition metal oxides are massively gaining an exciting horizon of research interest among material scientists by triggering scientific attention due to its prime advancements in physico-chemical, magneto-optical, electro-chemical, bio-medical and bio-compatible characteristics. The current work highlights the fabrication and formalisation of pure and X0.06Ni0.94O (X = Co, Fe, Cu) nanoparticles via bottom-up sol-gel pathway employing citric acid as the gelling factor. The crystallite size evaluated from X-Ray Diffraction (XRD) analysis decreased with respect to doping were estimated by successive systems among which Halder-Wagner (H-W) and Wagner-Agua (W-A) approach delivered prime results. Fourier Transform Infra-Red (FTIR) spectroscopy analysis regulated at room temperature in the mid infrared frequency continuum 400–4000 cm−1 confirmed the cubic conformation and the presence of predicted functional groups in the as-synthesized nanoparticles. The bandgap energy calculated from Ultra Violet-visible (UV–vis) spectroscopy is found to decrease for Co-NiO and Cu-NiO nanoparticles and increased for Fe doped NiO nanoparticles in comparison with the bandgap of pure NPs reasoned out by the Burstein-Moss shift. The device dependent parameter Urbach energy, and other pivotal optical parameters crucial in the fabrication of optoelectronic devices were evaluated. Surface morphological features and porous network of doped nanoparticles were investigated from Scanning Electron Microscopy (SEM) technique. Energy Dispersive X-ray (EDX) spectra ascertained the molecular matrix array and elemental composition in synthesized samples. The surface area measured from Brunauer-Emmett-Teller (BET) analysis revealed higher surface area (42 m2/g) for Fe-doped NiO nanoparticles than other counterparts. The thermal decomposition and stability of the pure and doped samples were analysed by Thermo-Gravimetric (TG) studies. The fundamental kinetic and thermodynamic parameters such as entropy, enthalpy, activation and Gibb’s free energy were elucidated through six different models viz., Coats-Redfern (CR), Piloyan-Novikava (PN), Horowitz-Metzger (HM), Van-Krevelen (VK), MacCallum-Tanner (MT) and Broido methods. Vibrating Sample Magnetometer (VSM) analysis coupled with the Law of Approach to Saturation (LAS) operandi extracted two critical magnetic criteria and the saturation magnetization is noticed to reduce with doping. The antibacterial and antifungal efficacies of the as-synthesized NPs were deeply discussed by portraying the nanoparticles-microbes interface. Iron and copper doped nickel oxide nanoparticles encountered favorable antimicrobial activity against pathogenic organisms. Furthermore, the bio-compatibility nature of the NPs was examined through hemolytic activity and the samples exhibited non-toxic behavior towards human cells till 50 μg/ml.

Nanoparticle‐Based Strain Gauges: Anisotropic Response Characteristics, Multidirectional Strain Sensing, and Novel Approaches to Healthcare Applications

AbstractDirectional strain sensing is essential for advanced sensor applications in the field of human‐machine interfaces and healthcare. Here, the angle dependent anisotropic strain sensitivity caused by charge carriers percolating through cross‐linked gold nanoparticle (GNP) networks is studied and these versatile materials are used for the fabrication of wearable triaxial pulse and gesture sensors. More specifically, the anisotropic response of 1,9‐nonanedithiol cross‐linked GNP films is separated into geometric and piezoresistive contributions by fitting the measured data with an analytic model. Hereby, piezoresistive coefficients of g11 ∼ 32 and g12 ∼ 21 are extracted, indicating a slightly anisotropic response behavior of the GNP‐based material. To use the material for healthcare applications, arrangements of three GNP transducers are patterned lithographically and fully embedded into a highly flexible silicone polymer (Dragon Skin 30). The new encapsulation method ensures good and robust electrical contacts and enables facile handling and protection from external influences. A facile read‐out with wireless data transmission using off‐the‐shelf electrical components underlines the great potential of these devices for applications as skin‐wearable healthcare sensors.

Multiscale bridging method to characterize elasto-plastic properties of polymer nanocomposites

A multiscale bridging method is proposed to describe the elasto-plastic behavior of polymer nanocomposites affected with the interphase elasto-plastic constitutive law (near the nanoparticle). The inverse characterization method of the interphase elasto–plastic constitutive law was proposed by combining full atomistic molecular dynamics and finite element homogenization. Based on the proposed multiscale bridging method, the influences of the crosslink ratio of the epoxy network and radius of nanoparticles on the elasto-plastic behavior of the interphase were investigated. Additionally, a multiscale homogenization analysis of the representative volume element of the multi-particulate systems was conducted using the elasto–plastic constitutive law of interphase.

Multifunctional Poly(acrylic acid)/Chitosan nanoparticle network hydrogels with tunable mechanics

Nanoparticle network hydrogels (NNHs) employ nanoparticles as key building blocks of hydrogel networks to provide excellent mechanical properties and multifunctionality. Herein, poly(acrylic acid)/chitosan nanoparticle network hydrogels (PAAc/CS NNHs) with prominent mechanical properties were fabricated using catechol functional methacryloyl chitosan-silver nanoparticles (CFMC-Ag NPs) as multifunctional nanoparticle crosslinkers. The PAAc/CS NNHs were composed of hybrid networks derived from CFMC-Ag NPs crosslinked PAAc and entangled chitosan (CS) chains. The mechanical properties of PAAc/CS NNHs were highly impacted by the concentration of CFMC-Ag NPs. A maximum tensile strength of 2.22 MPa, a compressive strength of 10.61 MPa, and a toughness of 5.57 MJ·m−3 were obtained at a nanoparticle concentration of 10 mg/mL. In addition, PAAc/CS NNHs exhibited great self-recovery performance and excellent fatigue resistance. It was demonstrated that PAAc/CS NNHs possessed antibacterial activity, electrical conductivity and anti-freezing capability. This strategy could be applied for the preparation of other multifunctional hydrogels with significant mechanical properties.

A comparative study on nanoparticle network‐dependent electrical conductivity, electromagnetic wave shielding effectiveness and rheological properties in multiwall carbon nanotubes filled polymer nanocomposites

AbstractHerein, a comparative study for the effect of nanoparticle networks on rheological behavior, electrical conductivity, and electromagnetic wave (EMW) shielding effectiveness (SE) is carried in conductive polymer composites (CPC). Two different polymers, that is, poly(ε‐caprolactone) (PCL) and isotactic polypropylene (iPP), which have different dispersion of multiwall carbon nanotubes (MWCNT), are used as polymer matrices. A transmission electron microscope (TEM) and a scanning electron microscope (SEM) are employed to determine the dispersion of MWCNTs in different polymer matrices. A rotational rheometer and a vector network analyzer are used to evaluate the percolation thresholds of storage modulus, complex viscosity and EMW SE, respectively. The results indicate that the EMW SE percolation thresholds are much larger than the electrical and rheological percolation thresholds. Specifically, the percolation thresholds of storage modulus and complex viscosity are 0.39 and 0.33 vol% for the MWCNT/PCL samples, and 1.57 and 1.57 vol% for the MWCNT/iPP samples, respectively. The electrical and EMW SE percolation thresholds are 0.33 and 1.99 vol%, 1.24 and 5.41 vol% for the MWCNT/PCL and MWCNT/iPP nanocomposites, respectively. The electrical and rheological percolation may happen in the samples with a sparse MWCNT network, while EMW SE percolation may require a dense MWCNT network in the samples.

On thermal stability and decomposition mechanisms of aromatic diamines employed as links in novel Pt nanoparticle network catalysts

The thermal stability of microporous networks of Pt nanoparticles interlinked by p-Phenylenediamine (PDA) was investigated by temperature-programmed desorption spectroscopy (TPD) and transmission electron microscopy (TEM). The detection of aniline, benzene, and NH3 as major desorbing fragments in TPD revealed cleavage of the C-N bonds in PDA as a major route of thermally induced decomposition, probably via hydrogenolysis assisted by dehydrogenation reactions of PDA running alongside. Varying the Pt:PDA ratio in the networks demonstrated that the Pt nanoparticles catalytically promote the decomposition of their PDA links. A quantitative analysis of the TPD spectra indicated that the thermal stability of PDA strongly correlates with the number of bonds (0, 1 or 2) formed by the amino groups of an individual PDA molecule with Pt. Only the most stable PDA species appears to be of relevance for the structural stability of the nanoparticle network, as heating experiments with in situ TEM showed. The results have strong implications for the application of PDA-linked Pt nanoparticles as heterogeneous catalysts in hydrogen gas microsensors where the choice of operating temperature has to balance maximization of signal-to-noise ratio and maintenance of structural stability. An anealing step up to 450–500 K after synthesis of the catalyst is suggested in order to optimize its catalytic activity by removing PDA species that are not essential for structural stabilty.

Influence of Thermal Treatment on Preceramic Polymer Grafted Nanoparticle Network Formation: Implications for Thermal Protection Systems and Aerospace Propulsion Components

Influence of Thermal Treatment on Preceramic Polymer Grafted Nanoparticle Network Formation: Implications for Thermal Protection Systems and Aerospace Propulsion Components

Flow determination via nanoparticle strain sensors for easy Lab on Chip integration

With the advancement of microfluidic and Lab on Chip systems, new challenges arise regarding efficient system monitoring as well as the detailed tracking of fluids within the system’s microfluidic channels. In this paper, a strain-sensing module offering facile integration with most microfluidic-systems is used for the determination of flow in a microfluidic chip. The sensor is based on platinum nanoparticle networks that are produced via a modified-sputtering technique; the nanoparticles self-assemble on top of flexible polyolefin substrates that also serve as the sealing layer of the microfluidic channels (fabricated on printed circuit board substrates or PCBs, by means of milling and computer numerical control machining). By introducing varying flow rates, pressure within the microfluidic channel increases thus resulting in the straining of the polyolefin layer and in modifying the resistance of the module. Numerical calculations, which take into account the bidirectional connection of fluid flow with the deformation of the sealing layer, are used to extract the channel geometry maximizing the sealing layer strain. Flow determination or flow-sensing experiments have also underlined the importance of polyolefin to PCB bonding-strength, which was greatly improved by oxygen plasma treatment. The module is able to detect flow rates as low as 5 μL/min, corresponding to a strain of 0.00337%, and showing a sensitivity of 0.021 (μL/min)−1, showcasing a) a competitive limit of detection (LoD), and b) low-cost, low-power requirements and easy integration with existing microfluidic systems, either as an autonomous unit or by integrating it on its sealing material.

Rapid and Ultrasensitive Electrochemical Detection of TP53 Gene Mutation in Blood: Hybridization with a DNA/Gold‐Coated Magnetic Nanoparticle Network

AbstractMutant TP53 has been demonstrated to be a promising biomarker as it is the most frequently mutated gene in human cancer. However, quantifying TP53 mutation presents two unique challenges: a broad concentration range and ultralow abundance. This study reports on the development of an ultrasensitive and highly‐selective electrochemical biosensor for the rapid detection of TP53 mutation in blood. TP53 mutation analysis is based on a network of gold‐coated magnetic nanoparticles modified with probe DNA (DNA−Au@MNPs). The DNA−Au@MNPs biosensor can rapidly and selectively detect TP53 gene with a single‐base mutation at a high background of wild‐type TP53 gene in blood. Moreover, the sensor presents a broad dynamic range of 1 aM to 10 nM for the mutant TP53 gene with the lowest detected concentration of 1 aM and significantly reduced response time of 20 min. Therefore, this biosensor demonstrates the potential to be used for minimally invasive analysis of cancer.

Oxide Films and Nanoparticles for Lithium Ion Battery and Oxygen Electrocatalyst Applications

The global energy crisis coupling with the consumption of fossil fuels and the associated environmental issues, has stimulated extensive interest in searching for clean, efficient and sustainable energy storage and conversion systems. In this talk we are going to introduce a novel chemical solution approach for epitaxial thin film deposition and oxide nanoparticle network synthesis. The use of water soluable polymer to bind the metal ions has several advantages. The formation of covalent complexes between the lone pairs on the nitrogen atoms of the polymer and the metal cations make it possible to prepare almost any metal polymer precursor solutions. The unique chemistry and processing design of this technique deliver stable and homogeneous solutions at a molecular level that allows epitaxial growth of high-quality thin films and oxide nanoparticle network materials. Oxygen electrocatalysis, including both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), dominates the performance of the devices. However, the sluggish kinetics of these two reactions limits their performance. Therefore, development of non-precious metal-based oxygen electrocatalysts is greatly demanded. Metal oxides have attracted extensive interest as alternative electrocatalysts due to their low price and good endurance under relatively high temperature, which can be doped with a wide range of cations attributed to their flexible compositions and structures, leading to easy manipulation of their electrocatalytic properties. We study the nanoscale engineering of perovskite oxides and layered oxides in energy conversion/storage devices and focus on the electrode catalyst design and fabrication for boosting ORR and OER electrocatalysis.

Multiscale modeling of the dynamical conductivity of self-assembled nanoparticle networks: Numerical simulations vs analytical models

Impedance spectroscopy experiments are able to reveal the fundamental charge transport properties of a wide variety of complex disordered and nano-structured materials provided that appropriate modeling tools are used. In this paper, we present a numerical simulation-based approach to model the dynamical conductivity of networks formed by self-assembled metal nanoparticles. Inter-particle nano-resistance and nano-capacitance are implemented at the nano-scale assuming inter-particle charge transfer and accumulation mechanisms that can be adapted depending on the nature of the nano-particles and the surrounding medium. The actual positions and spatial arrangements of the nanoparticles within the network are taken into consideration, allowing the attributes of percolating conducting routes to be extracted, classified, and compared in terms of path conductance and statistical distribution of path lengths. Our findings are contrasted to those obtained using analytic models, which are commonly used, but rely on strong assumptions about the electric properties of the conducting paths. We address these assumptions and show that in the case of weakly disordered systems, there is a general agreement between numerical simulations and analytic modeling-based approaches. In the case of disordered networks where the nano-particle size and position fluctuations are included, we show that the path length distribution is frequency-dependent and can differ significantly from the lognormal distribution usually assumed in the analytic models. The impedance of individual pathways may be extracted from the numerical simulations; we discovered that the conductance and susceptance of a specific path are frequency-dependent and inversely proportional to the path length only in ordered networks. Strong scattering of conductance values is caused by disorder effects. The developed numerical approach is generic and applies to most nano-devices where charge transport relies on percolation; it allows to bridge the gap between the nano-scale and micro-scale electric characteristics and, thus, permits a deeper understanding of the charge transport properties of nano-structured materials.

Photothermal behavior for two-dimensional nanoparticle ensembles: Multiple scattering and thermal accumulation effects

Light-assisted micro-nanoscale temperature control in complex nanoparticle network attracts lots of research interests. Many efforts have been put on the optical properties of the nanoparticle networks and only a few investigations on its light-induced thermal behavior was reported. We consider two-dimensional (2D) square-lattice nanoparticle ensemble made of typical metal Ag with a radius of 5 nm. The effect of complex optical coupling and thermal accumulation on the light-induced thermal behavior in plasmonic resonance frequency (around 383 nm) is analyzed by means of the Green\textquotesingle s function approach. Regime borders of both optical coupling and thermal accumulation effects on the photothermal behavior of 2D square-lattice nanoparticle ensemble are figured out clearly and quantitatively. A dimensionless parameter $\varphi$ is defined as the ratio of full temperature increase to that without considering the optical coupling or thermal accumulation to quantify the optical coupling and thermal accumulation effects on photothermal behavior. The more compact the nanoparticle ensemble is, the stronger the optical coupling on thermal behavior is. When the lattice spacing increases to tens of nanoparticle radius, the optical coupling becomes insignificant. When $\varphi \approx 1$ (lattice spacing increases to hundreds of nanoparticle radius), the thermal accumulation effects are weak and can be neglected safely. The polarization-dependent distribution of temperature increase of nanoparticles is observed only in the compact nanoparticle ensemble, while for dilute ensemble, such polarization-dependent temperature increase distribution can not be observed anymore. This work may help for the understanding of the light-induced thermal transport in the 2D particle ensemble.

Evolution of the Seebeck effect in nanoparticle-percolated networks under applied strain

Nanoparticle clouds feature a unique evolution of the Seebeck coefficient under applied strain. At low strain, the Seebeck effect is very stable while, when a critical strain threshold is reached, it sharply decreases to zero. The evolution mechanism of this phenomenon that contributes to the development of various strain-insensitive sensors has yet to be documented. We elucidate here this evolution by proposing a phenomenological model supported by strong experimental evidence. We realize a full study of the Seebeck effect evolution for a network of nanoparticles under variable strain. We describe the evolution of this network as three subsequent stages: completely connected, partially connected, and disconnected. Based on the conductance-weighted formula, we theoretically analyze the evolution of the Seebeck coefficient in each stage. The Seebeck coefficient’s initial stability is attributed to the connected pathways that exist in the first two stages. We validated these theoretical results by constructing percolated networks with embedded silver nanowires in elastomers and calculating the Seebeck coefficient under various stretching conditions. Finally, using the theoretical results as a guide, we created a temperature sensor that is highly resistant to mechanical damage.

Mussel-inspired strategy to construct 3D silver nanoparticle network in flexible phase change composites with excellent thermal energy management and electromagnetic interference shielding capabilities

Nowadays, efficient thermal management and electromagnetic interference shielding as effective measures for maintaining the normal operation of electronic devices are extremely significant. However, composites with both thermal management and electromagnetic interference shielding performance are rarely reported. In this study, a kind of flexible polydopamine (PDA) and silver nanoparticles (AgNPs) wrapped melamine foam (MF) constructed by adopting the mussel-inspired strategy was used to fabricate MPAχ-PEG phase change materials (PCMs) via encapsulating polyethylene glycol (PEG). PDA was selected to enhance the interface bonding between MF and AgNPs due to its strong adhesion based on mussel-inspired surface chemistry. Continuous AgNPs wrapped on skeleton of MF construct the three-dimensional (3D) thermal/electrical-conductive porous network. MPAχ-PEG PCMs exhibit a relatively high phase change enthalpy of 148.9 J/g and a high thermal conductivity enhancement of 1400% in comparison with that of MF-PEG. Moreover, MPAχ-PEG PCMs are provided with electromagnetic interference (EMI) shielding performance with the mean SET of 82.02 dB and electro-to-thermal energy conversion efficiency (86.3% under the voltage of 1.2 V) due to the 3D conductive AgNPs network. Combining the elasticity of MPAχ foams and the phase change feature of PEG, the MPAχ-PEG PCMs show good solar-induced shape memory performance. The flexible PCMs could avoid the sharp temperature increase of smartphone by the solid-liquid phase change process of PEG. Therefore, this study provides a promising strategy to prepare flexible PCMs, which can achieve various forms of energy conversion, as well as thermal management and EMI shielding performance, can definitely broaden their application prospect in electronic devices.