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Flexible ferroelectric materials are in high demand in emerging energy harvesting and self-powered sensing electronics. However, current flexible ferroelectric polymers, such as poly(vinylidene fluoride) (PVDF) and P(VDF-co-trifluoroethylene) [P(VDF-TrFE)], cannot fulfill the requirement of emerging applications because of their low piezoelectric/pyroelectric performance. In this work, using organic–inorganic hybrid perovskite [(4-aminotetrahydropyran)2PbBr2Cl2] ferroelectric nanorods as reinforcement and P(VDF-TrFE) as the matrix, we prepared flexible core–sheath piezoelectric nanofibers and pyroelectric nanocomposite films. The core–sheath nanofibers possess a record-high piezoelectric coefficient of 78.1 pC·N–1, and the output voltage reaches to 192 V, with the maximum power density of 1.04 W·m–2. On the other hand, the nanocomposite film exhibits a high pyroelectric coefficient of 58.2 μC·m–2·K–1at 333 K, which yields a voltage of 6.1 V under 6.6 K temperature fluctuation. An integrated flexible sensing device was prepared by combining piezoelectric nanofibers and pyroelectric films, which can wirelessly detect vibration and temperature fluctuation simultaneously. The integrated device is suitable for pipelines, power equipment, and other scenarios, where vibration and temperature need to be monitored at the same time.

Polymer nanocomposites combine the merits of polymer matrices and the unusual effects of nanoscale reinforcements and have been recognized as important members of the material family. Being a fundamental material property, thermal conductivity directly affects the molding and processing of materials as well as the design and performance of devices and systems. Polymer nanocomposites have been used in numerous industrial fields; thus, high demands are placed on the thermal conductivity feature of polymer nanocomposites. In this Perspective, we first provide roadmaps for the development of polymer nanocomposites with isotropic, in-plane, and through-plane high thermal conductivities, demonstrating the great effect of nanoscale reinforcements on thermal conductivity enhancement of polymer nanocomposites. Then the significance of the thermal conductivity of polymer nanocomposites in different application fields, including wearable electronics, thermal interface materials, battery thermal management, dielectric capacitors, electrical equipment, solar thermal energy storage, biomedical applications, carbon dioxide capture, and radiative cooling, are highlighted. In future research, we should continue to focus on methods that can further improve the thermal conductivity of polymer nanocomposites. On the other hand, we should pay more attention to the synergistic improvement of the thermal conductivity and other properties of polymer nanocomposites. Emerging polymer nanocomposites with high thermal conductivity should be based on application-oriented research.

High thermal conductivities are highly desired for electrocaloric (EC) materials to improve the key performances of EC devices, including cooling power density (CPD) and coefficient of performance (COP). However, despite the large EC effect (ECE), the state-of-the-art EC polymer exhibits low thermal conductivity. The simple mixture of the EC polymer and two-dimensional (2D) high-thermal-conductivity nanofillers would dramatically reduce ECE by increasing long-range ordering. To free dipole orientations, we introduced 3-sulfurouspropyltrimethoxysilane (SPTMS) to covalently graft boron-nitride nanosheets on the EC polymer. The interface-regulated nanocomposite exhibited the EC entropy change of 30.94 Jkg−1K−1under 100 MVm−1and thermal conductivity of 0.72 Wm−1K−1, and utilizing which, the standard model of EC refrigerator achieved a 5.23 Wg−1CPD, 6.8-fold higher than the one operating a simple mixture. A figure of merit of electrocaloric nanocomposites was proposed to assess their overall capability in the heat-pumping applications.

The low piezoelectricity of piezoelectric polymers significantly restricts their applications. Introducing inorganic fillers can slightly improve the piezoelectricity of polymers, whereas it is usually at the cost of flexibility and durability. In this work, using a modulus-modulated core–shell structure strategy, all-organic nanofibers with remarkable piezoelectricity were designed and prepared by a coaxial electrospinning method. It was surprisingly found that the introduction of a nonpiezoelectric polymeric core (e.g., polycarbonate, PC) can result in 110% piezoelectric coefficient (d33) enhancement in a poly(vinylidenefluoride-co-trifluoroethylene) (PVDF-TrFE) nanofiber. Accordingly, the all-organic PVDF-TrFE@PC core–shell nanofiber exhibits record-high energy-harvesting performance (i.e., 126 V output voltage, 710 mW m–2power density) among the reported organic piezoelectric materials. In addition, the excellent sensing capability of the core–shell nanofiber enabled us to develop a wireless vibration monitoring and analyzing system, which realizes the real-time vibration detection of a power transformer.

For capacitive energy storage at elevated temperatures1–4, dielectric polymers are required to integrate low electrical conduction with high thermal conductivity. The coexistence of these seemingly contradictory properties remains a persistent challenge for existing polymers. We describe here a class of ladderphane copolymers exhibiting more than one order of magnitude lower electrical conductivity than the existing polymers at high electric fields and elevated temperatures. Consequently, the ladderphane copolymer possesses a discharged energy density of 5.34 J cm−3with a charge–discharge efficiency of 90% at 200 °C, outperforming the existing dielectric polymers and composites. The ladderphane copolymers self-assemble into highly ordered arrays by π–π stacking interactions5,6, thus giving rise to an intrinsic through-plane thermal conductivity of 1.96 ± 0.06 W m−1K−1. The high thermal conductivity of the copolymer film permits efficient Joule heat dissipation and, accordingly, excellent cyclic stability at elevated temperatures and high electric fields. The demonstration of the breakdown self-healing ability of the copolymer further suggests the promise of the ladderphane structures for high-energy-density polymer capacitors operating under extreme conditions.

As the unique power entrance, the pantograph–catenary electrical contact system maintains the efficiency and reliability of power transmission for the high-speed train. Along with the fast development of high-speed railways all over the world, some commercialized lines are built for covering the remote places under harsh environment, especially in China; these environmental elements including wind, sand, rain, thunder, ice and snow need to be considered during the design of the pantograph–catenary system. The pantograph–catenary system includes the pantograph, the contact wire and the interface—pantograph slide. As the key component, this pantograph slide plays a critical role in reliable power transmission under dynamic condition. The fundamental material characteristics of the pantograph slide and contact wire such as electrical conductivity, impact resistance, wear resistance, etc., directly determine the sliding electrical contact performance of the pantograph–catenary system; meanwhile, different detection methods of the pantograph–catenary system are crucial for the reliability of service and maintenance. In addition, the challenges brought from extreme operational conditions are discussed, taking the Sichuan–Tibet Railway currently under construction as a special example with the high-altitude climate. The outlook for developing the ultra-high-speed train equipped with the novel pantograph–catenary system which can address the harsher operational environment is also involved. This paper has provided a comprehensive review of the high-speed railway pantograph–catenary systems, including its progress, challenges, outlooks in the history and future.

This study aims to develop an effective tool by integrating traditional analysis methods with advanced sensor array technology and multiple algorithms, to achieve rapid characterization, qualitative identification, and flavor quality evaluation of fermented bean products. Firstly, the flavor compounds and flavor profiles of fermented bean curd from different manufacturers were identified using headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) and quantitative descriptive analysis (QDA). A total of 63 volatile compounds were identified, of which 13 volatile compounds were identified as the key differential compounds in selected samples. Eight descriptors were selected to represent the aroma characteristics of fermented bean curd. Based on the key differential compounds, a low-cost colorimetric sensor array (CSA) was designed and constructed. Furthermore, the feasibility of CSA combined with multiple algorithms was investigated for brand discrimination and flavor quality assessment. Linear discriminant analysis (LDA) exhibited a better performance in distinguishing different flavor quality samples, and the recognition accuracy of its prediction set was 97.22%. The study suggests that CSA combined with multiple algorithms can be an effective tool for flavor characterization and qualitative discrimination of fermented bean curd, and can provide a new multi-dimensional analysis method for food analysis.

The rapid development of 5G equipment and high-power density electronic devices calls for high thermal conductivity materials for heat dissipation. Dielectric polymer composites are highly promising as the electrical insulation, mechanical property, thermal stability, and even fire retardance are also of great importance for electrical and electronic applications. However, the current thermal conductivity enhancement of dielectric polymer composites is usually at the cost of lowering the mechanical and electrical insulating properties. In this work, we report the facile preparation of highly thermally conductive and electrically insulating poly(p-phenylene benzobisoxazole) nanofiber (PBONF) composites by incorporating a low weight fraction of functionalized boron nitride nanosheets (BNNSs). With strong electrostatic interaction, the BNNSs are encapsulated by PBONFs, and the constructed robust interconnected network makes the nanocomposites exhibit a nacre-like structure. Accordingly, the nanocomposite paper has a high in-plane thermal conductivity of 21.34 W m–1K–1at a low loading of 10 wt % BNNSs and exhibits an ultrahigh strength of 206 MPa. Additionally, the nanocomposite paper exhibits superior electrical insulation properties up to higher than 350 °C and excellent fire retardance. The strong heat dissipation capability of the nanocomposite paper was demonstrated in 5G base stations and control transformers, showing wide potential applications in high power density electrical equipment and electronic devices.

A high dielectric solid polymer electrolyte (PVDF–LiFSI) improves the interface stability and cycling lifespan of all-solid-state Li||LiFePO4under high loading (11.5 mg cm−2) at 28 °C.

A low-cost electronic nose (E-nose) based on colorimetric sensors fused with Fourier transform-near-infrared (FT-NIR) spectroscopy was proposed as a rapid and convenient technique for detecting beef adulterated with duck. The total volatile basic nitrogen, protein, fat, total sugar and ash contents were measured to investigate the differences of basic properties between raw beef and duck; GC-MS was employed to analyze the difference of the volatile organic compounds emitted from these two types of meat. For variable selection and spectra denoising, the simple T-test (p< 0.05) separately intergraded with first derivative, second derivative, centralization, standard normal variate transform, and multivariate scattering correction were performed and the results compared. Extreme learning machine models were built to identify the adulterated beef and predict the adulteration levels. Results showed that for recognizing the independent samples of raw beef, beef–duck mixtures, and raw duck, FT-NIR offered a 100% identification rate, which was superior to the E-nose (83.33%) created herein. In terms of predicting adulteration levels, the root means square error (RMSE) and the correlation coefficient (r) for independent meat samples using FT-NIR were 0.511% and 0.913, respectively. At the same time, for E-nose, these two indicators were 1.28% and 0.841, respectively. When the E-nose and FT-NIR data were fused, the RMSE decreased to 0.166%, and the rimproved to 0.972. All the results indicated that fusion of the low-cost E-nose and FT-NIR could be employed for rapid and convenient testing of beef adulterated with duck.

More than a decade of research on the electrocaloric (EC) effect has resulted in EC materials and EC multilayer chips that satisfy a minimum EC temperature change of 5 K required for caloric heat pumps1–3. However, these EC temperature changes are generated through the application of high electric fields4–8(close to their dielectric breakdown strengths), which result in rapid degradation and fatigue of EC performance. Here we report a class of EC polymer that exhibits an EC entropy change of 37.5 J kg−1K−1and a temperature change of 7.5 K under 50 MV m−1, a 275% enhancement over the state-of-the-art EC polymers under the same field strength. We show that converting a small number of the chlorofluoroethylene groups in poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer into covalent double bonds markedly increases the number of the polar entities and enhances the polar–nonpolar interfacial areas of the polymer. The polar phases in the polymer adopt a loosely correlated, high-entropy state with a low energy barrier for electric-field-induced switching. The polymer maintains performance for more than one million cycles at the low fields necessary for practical EC cooling applications, suggesting that this strategy may yield materials suitable for use in caloric heat pumps.

[Display omitted] • Graphene hybrid aerogel with an anisotropic well-oriented structure was designed. • Aerogel-200 has super-hydrophilicity and outstanding wet-resilience properties. • Aerogel-1500 exhibits superior thermal conductivity enhancement in polymers. Three-dimensional (3D) graphene-based aerogels have significant potential for adsorption, sensors, and thermal management applications. However, their practical applications are limited by their disorganized structure and ultra-low resilience after compression. Some methods can realize a well-aligned structure, however, they involve high costs and complex technology. Herein, a 3D graphene hybrid aerogel with an anisotropic open-cell and well-oriented structure is realized by unidirectional freeze casting, which combines the 'soft' (e.g. graphene oxide, Tween-80) and 'hard' (e.g. graphene assembly) components to realize full recovery after flattening. A graphene aerogel annealed at a moderate temperature (∼200 °C) can possess superhydrophilicity and outstanding wet-resilience properties, including after being pressed under 40 MPa. Furthermore, the graphene aerogel annealed at a high temperature of ∼1500 °C exhibits excellent thermal conductivity enhancement efficiency in polydimethylsiloxane (PDMS). The resultant nanocomposites clearly demonstrate anisotropic thermal conductivity and promising applications as thermal interface materials. This strategy offers new insights into the design and fabrication of 3D multifunctional graphene aerogels. [ABSTRACT FROM AUTHOR]

Space charge tend to accumulate at the polarity shell of core-shell structured nanoparticles, which causes leakage current and electrical breakdown at high electrical field, reduce the energy storage performance of nanocomposite dielectric.

Aflatoxin B1 (AFB1) is one of the most carcinogenic chemicals. A novel fluorescence resonance energy transfer (FRET) sensor based on aptamer recognition technology is proposed for the sensitive detection of AFB1 in moldy peanuts using Ag nanocubes as energy acceptors and ZnS quantum dots (QDs) as energy donors. Compared to the traditional FRET system based on an Au quencher, Ag nanocubes can not only quench the fluorescence of aptamer modified ZnS QDs, but are also inexpensive. In addition, compared with heavy metal QDs, ZnS QDs are environmentally friendly, have excellent photochemical properties, and are ideal energy donors. Without Ag nanocubes, the aptamer modified ZnS QDs emits blue fluorescence under an ultraviolet lamp. Because the emission spectrum of ZnS and the absorption spectrum of Ag nanocubes meet the requirements of FRET, the fluorescence quenching of ZnS QDs is realized. Nevertheless, with AFB1, the specific binding of aptamer and complementary chain makes the ZnS QDs break away from the Ag nanocubes, which leads to the fluorescence recovery of the ZnS QDs. Under the optimized detection conditions, the linear range of AFB1 was 5 pg mL−1to 300 ng mL−1, and there was no obvious reaction with other similar mycotoxins. According to S/N = 3, the detection limit of AFB1 was 2.67 pg mL−1. The detection of AFB1 in peanut samples shows that the new FRET system can successfully be applied in the future to agricultural products.

A core–sheath structured phase change nanocomposite (PCN) with aligned and overlapping interconnected BNNS networks were successfully fabricated.The PCN has an ultrahigh in-plane thermal conductivity (28.3 W m−1K−1), excellent flexibility and high phase change enthalpy (101 J g−1).The PCN exhibits intensively potential applications in the thermal management of 5G base stations and thermoelectric generators.

AbstractMicrobial food safety is a persistent and exacting global issue due to the multiplicity and complexity of foods and food production systems. Foodborne illnesses caused by foodborne bacterial pathogens frequently occur, thus endangering the safety and health of human beings. Factors such as pretreatments, that is, culturing, enrichment, amplification make the traditional routine identification and enumeration of large numbers of bacteria in a complex microbial consortium complex, expensive, and time-consuming. Therefore, the need for rapid point-of-use detection systems for foodborne bacterial pathogens with high sensitivity and specificity is crucial in food safety control. Hyperspectral imaging (HSI) as a powerful testing technology provides a rapid, nondestructive approach for pathogen detection. This article reviews some fundamental information about HSI, including instrumentation, data acquisition, image processing, and data analysis—the current application of HSI for the detection, classification, and discrimination of various foodborne pathogens. The merits and demerits of HSI for pathogen detection as well as current and future trends are discussed. Therefore, the purpose of this review is to provide a brief overview of HSI, and further lay emphasis on the emerging trend and importance of this technique for foodborne pathogen detection.

Increasing power density makes modern electronic devices and power equipment generate excess heat, which greatly restricts the applications of polymeric materials because of their poor thermal conductivity. In the present work, inspired by the structure and production process of millefeuille cakes, we show that electrostatic spraying of boron nitride nanosheets (BNNSs) onto electrospun poly(vinyl alcohol) (PVA) nanofibers can produce highly thermally conductive, electrically insulating, flexible, and lightweight nanocomposites via a scalable method of building a multilayer PVA/BNNS nanonetwork structure. The PVA/BNNS nanocomposites exhibit an ultrahigh in-plane thermal conductivity of 21.4 W/(m·K) at 22.2 vol % BNNS addition, realized by an orientated BNNS network structure with overlapping interconnections. The BNNS networks exhibit low thermal resistance and interfacial heat scattering between BNNSs. Moreover, for heat dissipation applications, the nanocomposites with an overlapping BNNS network show higher efficiency in dissipating hot spots than randomly dispersed BNNS or directly hot-pressed BNNS composites. These PVA/BNNS nanocomposites can be used as high-performance lateral heat spreaders in next-generation thermal management systems.

Polymer-based gate dielectrics have received growing attention due to their important role in field-effect transistors (OFETs). This review article aims to present the recent progress of polymer dielectrics for high-performance OFET applications. We first discuss the requirements for polymer dielectrics in tailoring the overall performance of OFETs from the perspective of both bulk material properties and surface characteristics of the polymers. On this basis, we introduce the design strategies and desired processing techniques of polymer dielectrics for optimizing the charge transport and stabilizing the operation of OFETs. Then, we highlight the recent advances in polymer-based dielectrics by classifying and comparing different categories of polymeric materials as well as polymer nanocomposites, and focus is also given to elucidating the critical relationships between polymer structures, gate dielectric properties and OFET performance. Finally, a perspective of future research directions and challenges for polymer dielectrics is provided.

Flexible piezoelectric nanogenerators (PENGs) with high output performance are highly desirable for energy harvesting. Coupling triboelectric nanogenerators (TENGs) with the PENGs is a feasible method to enhance the output performance, while the complicated structure and the requirement of skillful operation limited the development of hybridized nanogenerators. In this work, flexible high-performance PENGs are developed using regenerated cellulose/BaTiO3(C/BT) aerogel papers based polydimethylsiloxane (PDMS) nanocomposites. Benefiting from the high loading but uniform dispersion of tetragonal BT nanoparticles and the enhanced Young Modulus of the nanocomposites, the PENGs can exhibit a maximum voltage of 15.5 V and a maximum power of 11.8 μW under an external mechanical impact. By introducing a single electrode TENG, an innovative hybridized nanogenerator has been designed and prepared, which combine different mechanical energy harvesting techniques in a single device. Polarized along proper direction of the PENG, the positive coupling effect can efficiently increase the output voltage and power of the hybridized nanogenerator to 48 V and 85 μW, respectively. This research offers new insights into the design and preparation of high output hybridized nanogenerator with simple structure, high flexibility and easy operation.

Thermally conductive yet electrically insulating polymer composites are urgently required for thermal management applications of modern electrical systems and electronic devices because of their multifunctionality and ease of processing. However, the thermal conductivity enhancement of polymer composites is usually at the price of the loss of lightweight, the deterioration of flexibility, and electrical insulation. Here we report advanced polymer nanocomposites containing orientated boron nitride nanosheets (BNNSs), which simultaneously exhibit high thermal conductivity enhancement, excellent electrical insulation, and outstanding flexibility. These nanocomposite films can be easily constructed by electrospinning polymer/BNNSs nanocomposite fibers, vertically folding the electrospun nanocomposite fibers and the subsequent pressing. The nanocomposite films exhibit thickness-dependent in-plane thermal conductivity, which can reach 16.3 W/(m·K) in the 18 μm thick nanocomposite film with 33 wt % BNNSs. In addition, the nanocomposite films have superior electrically insulating properties compared with the pristine polymer, such as reduced dielectric loss, increased electrical resistivity, and enhanced breakdown strength. The strong thermal management capability of the nanocomposite film was demonstrated in switching power supply, which showed the importance of high in-plane thermal conductivity in thermal management of high-power density electronic devices.

Piezoelectric nanogenerators (PENGs) with good flexibility and high outputs have promising and outstanding applications for harvesting mechanical energy and powering electronics. In this work, PENGs are fabricated by using electrospun nanocomposite fiber mats comprising barium titanate (BT) nanoparticles, graphene nanosheets and poly(vinylidene fluoride) (PVDF). When the nanocomposite fiber mats are composed of 0.15 wt% graphene nanosheets and 15 wt% BT nanoparticles, the open-circuit voltage and electric power of the PENG can reach as high as 11 V and 4.1 μW under a loading frequency of 2 Hz and a strain of 4 mm, and no apparent decline of the open-circuit voltage is observed after 1800 cycles in the durability test. In addition, the PENG generate a peak voltage as high as 112 V during a finger pressing-releasing process, which can light up 15 LEDs and drive an electric watch. The improved output of the PENG is ascribed to the synergistic contribution of the BT nanoparticles and graphene nanosheets to the piezoelectric performance enhancement of the nanocomposite fibers. This study shows that the nanocomposite fiber based flexible PENGs are promising mechanical energy harvesters and effective power sources for portable electronic and wearable devices.

Flexible dielectric materials with high electrical energy densities are of crucial importance in advanced electronics and electric power systems. The conventional methods for fabricating flexible dielectric materials with high electrical energy densities are introducing zero-, one-, and three-dimensional high-k inorganic nanofiller into a dielectric polymer matrix while less two-dimensional high-k nanofillers were included. Herein, two-dimensional (2D) high-k titanium dioxide nanosheets prepared by a one-step hydrothermal reaction were utilized to boost the energy storage performance of dielectric polymer nanocomposites. It was found that compared with the polymer matrix the nanocomposites not only exhibit an enhanced dielectric constant but also show suppressed dielectric loss, which is desirable for energy storage applications. The nanocomposite with 5 wt % 2D nanosheets exhibits a superhigh discharged energy density of 13.0 J/cm3at 570 MV/m, which is nearly four times greater than that of commercialized biaxially oriented polypropylene (BOPP) (3.6 J/cm3at 600 MV/m). In addition, nanocomposites with 5 wt % zero- and one-dimensional (0D and 1D) nanofiller are also fabricated for comparison. Results reveal that discharged energy densities of nanocomposites with 5 wt % 2D nanosheets are 236% and 382% higher than those of nanocomposites with 5 wt % 1D (5.5 J/cm3at 400 MV/m) and 0D (3.4 J/cm3at 300 MV/m) nanofiller, respectively. Finite element simulation was conducted to study the electric field distribution in nanocomposites with different shapes of nanofillers. Furthermore, the comparison of the current nanocomposites and previous reported nanocomposites with 0D, 1D, and 3D nanofillers shows that the 2D high-k nanofiller exhibited superior potential in advancing the energy storage nature of polymer nanocomposites. This remarkable exhibition of energy storage capability provides new insights into the development of high performance dielectric materials.

The urgent demand of high energy density and high power density devices has triggered significant interest in high dielectric constant (high-k) flexible nanocomposites comprising dielectric polymer and high-kinorganic nanofiller. However, the large electrical mismatch between polymer and nanofiller usually leads to earlier electric failure of the nanocomposites, resulting in an undesirable decrease of electrical energy storage capability. A few studies show that the introduction of moderate-kshell onto a high-knanofiller surface can decrease the dielectric constant mismatch, and thus, the corresponding nanocomposites can withstand high electric field. Unfortunately, the low apparent dielectric enhancement of the nanocomposites and high electrical conductivity mismatch between matrix and nanofiller still result in low energy density and low efficiency. In this study, it is demonstrated that encapsulating moderate-knanofiller with high-kbut low electrical conductivity shell is effective to significantly enhance the energy storage capability of dielectric polymer nanocomposites. Specifically, using BaTiO3nanoparticles encapsulated TiO2(BaTiO3@TiO2) core–shell nanowires as filler, the corresponding poly(vinylidene fluoride-co-hexafluoropylene) nanocomposites exhibit superior energy storage capability in comparison with the nanocomposites filled by either BaTiO3or TiO2nanowires. The nanocomposite film with 5 wt % BaTiO3@TiO2nanowires possesses an ultrahigh discharged energy density of 9.95 J cm–3at 500 MV m–1, much higher than that of commercial biaxial-oriented polypropylene (BOPP) (3.56 J cm–3at 600 MV m–1). This new strategy and corresponding results presented here provide new insights into the design of dielectric polymer nanocomposites with high electrical energy storage capability.

The continuous evolution toward semiconductor technology in the “more-than-Moore” era and rapidly increasing power density of modern electronic devices call for advanced thermal interface materials (TIMs). Here, we report a novel strategy to construct flexible polymer nanocomposite TIMs for advanced thermal management applications. First, aligned polyvinyl alcohol (PVA) supported and interconnected 2D boron nitride nanosheets (BNNSs) composite fiber membranes were fabricated by electrospinning. Then, the nanocomposite TIMs were constructed by rolling the PVA/BNNS composite fiber membranes to form cylinders and subsequently vacuum-assisted impregnation of polydimethylsiloxane (PDMS) into the porous cylinders. The nanocomposite TIMs not only exhibit a superhigh through-plane thermal conductivity enhancement of about 10 times at a low BNNS loading of 15.6 vol % in comparison with the pristine PDMS but also show excellent electrical insulating property (i.e., high volume electrical resistivity). The outstanding thermal management capability of the nanocomposite TIMs was practically confirmed by capturing the surface temperature variations of a working LED chip integrated with the nanocomposite TIMs.

Rapid evolution of energy storage devices expedites the development of high-energy-density materials with excellent flexibility and easy processing. The search for such materials has triggered the development of high-dielectric-constant (high-k) polymer nanocomposites. However, the enhancement of kusually suffers from sharp reduction of breakdown strength, which is detrimental to substantial increase of energy storage capability. Herein, the combination of bio-inspired fluoro-polydopamine functionalized BaTiO3nanowires (NWs) and a fluoropolymer matrix offers a new thought to prepare polymer nanocomposites. The elaborate functionalization of BaTiO3NWs with fluoro-polydopamine has guaranteed both the increase of kand the maintenance of breakdown strength, resulting in significantly enhanced energy storage capability. The nanocomposite with 5 vol % functionalized BaTiO3NWs discharges an ultrahigh energy density of 12.87 J cm–3at a relatively low electric field of 480 MV m–1, more than three and a half times that of biaxial-oriented polypropylene (BOPP, 3.56 J cm–3at 600 MV m–1). This superior energy storage capability seems to rival or exceed some reported advanced nanoceramics-based materials at 500 MV m–1. This new strategy permits insights into the construction of polymer nanocomposites with high energy storage capability.

Supercapacitors have been attracting significant attention as promising energy storage devices. However, the voltage window limitation associated with electrolyte solutions has hindered the improvement of their capacitance. To address this issue and enhance the energy storage capabilities of general traditional supercapacitors, we put forward the dipole-induced effects observed in the theoretical framework of the electric double-layer structure. The molecular dynamics results demonstrate that, compared to traditional systems, an improvement of over 50% in integral capacitance at low voltages is achieved. Moreover, a new material-based experimental results obtained from a dielectric supercapacitor employing a hydrated electrolyte solution corroborated the effectiveness of our proposed model, yielding consistent outcomes. We attribute the large capacitance variation to the reorientation of the dipoles, which induces the neutral-to-bilayer transition and the overscreening-to-steric transition, consistent with the polarization process of the polymer in the experiment. We further investigate the capacitance variations under different dipole parameters, such as varying the number of layers, different number densities and different spacings, thereby enriching the experimental results with additional conclusions not previously obtained. This work presents a novel approach that exploits dipole-induced capacitance effects, paving the way for further advances in the field of energy storage technology.

High conduction band inorganic layers are manufactured via simple but efficient methodology.The multilayered nanocomposite possesses an outstanding breakdown strength of 611 MV m−1and an excellent discharged energy density of 14.3 J cm−3, which are 119% and 177% of the randomly dispersed nanocomposite (515 MV m−1, and 8.1 J cm−3).The current work offers a new paradigm for design and production of high energy density flexible dielectric films.

This work reports the advances of utilizing a core@double-shell nanostructure to enhance the electrical energy storage capability and suppress the dielectric loss of polymer nanocomposites. Two types of core@double-shell barium titanate (BaTiO3) matrix-free nanocomposites were prepared using a surface initiated atom transfer radical polymerization (ATRP) method to graft a poly(2-hydroxylethyle methacrylate)-block-poly(methyl methacrylate) and sodium polyacrylate-block-poly(2-hydroxylethyle methacrylate) block copolymer from BaTiO3nanoparticles. The inner shell polymer is chosen to have either high dielectric constant or high electrical conductivity to provide large polarization, while the encapsulating outer shell polymer is chosen to be more insulating as to maintain a large resistivity and low loss. Finite element modeling was conducted to investigate the dielectric properties of the fabricated nanocomposites and the relaxation behavior of the grafted polymer. It demonstrates that confinement of the more conductive (lossy) phase in this multishell nanostructure is the key to achieving a high dielectric constant and maintaining a low loss. This promising multishell strategy could be generalized to a variety of polymers to develop novel nanocomposites.

This work reports the advances of utilizing molybdenum disulfide (MoS2) nanosheet superstructures to enhance dielectric property and electrical energy storage capability of flexible ferroelectric polymer composites. Hydrangea-like flowers or clusters comprising MoS2nanosheets were synthesized by hydrothermal methods and used as filler of ferroelectric polymer composites. Both MoS2superstructure based composites show percolation-like electrical behavior. The composites with high loading of MoS2superstructures exhibit significantly enhanced dielectric constant, whereas those with low loading of MoS2superstructures can withstand high electric field and exhibit significantly enhanced electric polarization, resulting in significant improvement of electrical energy storage capability. The MoS2flowers show strong potential to enhance the dielectric constant and electrical energy storage capability of the composites.

Freshness is one of the most significant parameters of fish quality. This study aims to develop a new rapid non-destructive technique to assess fish freshness. Two different technologies including computer vision and near-infrared spectroscopy (NIR spectroscopy) were employed in the detection. Subsequently a new data fusion detection method was developed to improve the accuracy of classification by combining the inspection data of computer vision with that of NIR spectroscopy. Parabramis pekinensisbought from a local market were taken as experimental samples. The total volatile basic nitrogen (TVB-N) content of the samples was measured as an indicator of fish freshness using conventional methods. Computer vision and NIR spectroscopy were used to acquire image information for organoleptic changes and spectrum information for structural changes in the fish samples during storage, respectively. Principal component analysis (PCA) was used for data compression to reduce the dimensionality of the data set while essential information was retained, which made the analysis easier than it would have been for the original huge data set. A back propagation artificial neural network (BP-ANN) was used to build a prediction model by obtaining a non-linear relation between the fish freshness and the body changes during storage. The results showed that computer vision technology outperformed NIR spectroscopy techniques, for the BP-ANN model reached a 94.17% success rate in the training set and 90.00% in the prediction set using the computer vision technology, while the model of NIR spectroscopy reached 86.67% and 80.00% in the training set and prediction set respectively. This showed improved fish freshness classification using computer vision technology rather than the NIR spectroscopic method. Therefore, the data from the two techniques were considered simultaneously, using the classification model BP-ANN, which achieves the optimum performance of 96.67% and 93.33% corresponding to the training set and prediction set respectively using data fusion. Therefore, this demonstrated for the first time the feasibility and superiority of data fusion by integrating computer vision and NIR spectroscopy in the classification of fish freshness.

Flexible high-dielectric-constant (high-κ) nanocomposite dielectrics comprising polymer matrix and ceramic nanoparticles have important applications in the fields of electrical insulation and energy storage. However, most of the flexible high-κ nanocomposites are fabricated by using nonbiodegradable polymers as matrixes, which may not meet the increasing demands of society for environmental sustainability. In this study, using biodegradable polylactic acid (PLA) as a matrix and core–shell structured BaTiO3(BT) nanoparticles as high-κ filler, we report the preparation and structure–property relationship of environmentally friendly flexible high-κ polymer nanocomposites. Two types of core–shell structured high-κ nanoparticles [polydopamine-encapsulated BT (BT@PDA) and PLA-encapsulated BT@PDA (BT@PDA@PLA)] as well as as-prepared BT nanoparticles were used as filler of the PLA-based high-κ nanocomposites. It was found that, compared with the as-prepared BT nanocomposites, the core–shell nanoparticle-based composites show enhanced dielectric constant, suppressed dielectric loss tangent, and enhanced breakdown strength. In addition, the BT@PDA@PLA nanocomposites have much higher dielectric constant and energy density. The nanoparticle–PLA compatibility and its influence on the dielectric and energy storage properties of the nanocomposites were also investigated. Because the polymer matrix is environmentally friendly and the preparation process of the core–shell nanoparticles is facile and nontoxic, the nanocomposites reported here may be used in the next generation of environmentally friendly high-performance energy storage devices.

We proposed a facile method to prepare the nitrogen-doped graphene quantum dots (NGQDs) doped silica (NGQDs@SiO2) nanoparticles (NPs). The NGQDs@SiO2NPs were further explored as a versatile signal indicator for ochratoxin A (OTA) aptasensing by combination with electrochemiluminescence (ECL) and fluorescence (FL) detection. In this strategy, the core–shell Fe3O4@Au magnetic beads (MBs) acted as a nanocarrier to immobilize the thiolated aptamer specific for OTA, and the amino modified capture DNA (cDNA) was efficiently tagged with NGQDs@SiO2NPs. The multifunctional aptasensor was thus fabricated by assembly of the NGQDs@SiO2NPs onto the surface of Fe3O4@Au MBs through the high specific DNA hybridization between aptamer and cDNA. Upon OTA incubation, the aptamer linked with Fe3O4@Au MBs preferred to form an aptamer–OTA complex, which resulted in the partial release of the preloaded NGQDs@SiO2NPs. The more OTA molecules in the detection system, the more NGQDs@SiO2NPs were released into the bulk solution and the less preloaded NGQDs@SiO2NPs were accumulated on the magnetic electrode surface. This provided a dual channel for OTA detection by combination with the enriched solid-state ECL and homogeneous FL detection. The FL assay exhibits a wide dynamic range and is more reproducible due to the homogeneous detection while the ECL assay possesses a lower detection limit and is preferable by using a cheaper instrument. One can obtain a preliminary screen from FL assay and a more accurate result from ECL assay. Integrating the virtues of dual analytical modality, this aptasensing strategy well-balanced the rapidity, sensitivity, and dynamic range, making it promising to other targets with aptamer sequences.

Flexible nanocomposites comprising a dielectric polymer matrix and high-knanoparticle fillers have shown great potential for power energy storage applications. However, the addition of high-knanoparticles usually causes low breakdown strength and low energy efficiency of the nanocomposites, which limit their practical applications, particularly at high electric fields. In this work, we report a novel method to enhance the energy storage efficiency and breakdown strength of high-knanowire (NW)-based poly(vinylidene fluoride-co-hexafluoropropylene) nanocomposites. Ba0.7Sr0.3TiO3NWs were synthesized by a hydrothermal method, and their surface was grafted with a layer of poly(pentafluorophenyl acrylate) (PPFPA) via in situ reversible addition–fragmentation chain transfer polymerization. Compared with the addition of as-prepared NWs, the incorporation of PPFPA-encapsulated NWs apparently enhanced the breakdown strength of the nanocomposites. On the other hand, the incorporation of PPFPA-encapsulated NWs results in much lower dielectric loss at low frequencies and higher energy storage efficiency of the nanocomposites. Although the two nanocomposites exhibit comparable discharged energy densities at relatively low electric field (e.g., <200 kV/mm), much higher energy storage capability can be expected in the nanocomposites with PPFPA-encapsulated NWs because of their high breakdown strength.

The interfacial interaction between the carbonized matrix and binder directly correlates with the performance of the carbon-matrix composites. The involvement of the reduced graphene oxide (rGO) in composites is considered an effective strategy to enhance the performance of composites via improving the interface property. Herein, the rGO was converted in-situ from the graphene oxide (GO) on the interface between the matrix and the carbonized binder during the sintering process. Compared with the pristine composites, the compressive strength (203.90 MPa ±2.85 MPa) and flexural strength (40.53 ± 1.42 MPa) of carbon-matrix composites doping 0.2 wt% of GO can be increased by 112.1% and 71.2%, respectively. It is attributed to the fact that rGO forms an ideal interface bond with the carbonized matrix and binder, which effectively promotes the deflection of the crack propagation path. Meanwhile, molecular dynamics simulations unlocked an automatic protective reinforcement mechanism of the rGO-enhanced composites. A low-cost yet effective scheme for improving composites interfaces is proposed here, which lays a theoretical foundation for developing the high-strength carbon-matrix composites.

Dielectric polymer composites with high dielectric constants and high thermal conductivity have many potential applications in modern electronic and electrical industry. In this study, three-phase composites comprising poly(vinylidene fluoride) (PVDF), barium titanate (BT) nanoparticles, and β-silicon carbide (β-SiC) whiskers were prepared. The superiority of this method is that, when compared with the two-phase PVDF/BT composites, three-phase composites not only show significantly increased dielectric constants but also have higher thermal conductivity. Our results show that the addition of 17.5 vol % β-SiC whiskers increases the dielectric constants of PVDF/BT nanocomposites from 39 to 325 at 1000 Hz, while the addition of 20.0 vol % β-SiC whiskers increases the thermal conductivity of PVDF/BT nanocomposites from 1.05 to 1.68 W m–1K–1at 25 °C. PVDF/β-SiC composites were also prepared for comparative research. It was found that PVDF/BT/β-SiC composites show much higher dielectric constants in comparison with the PVDF/β-SiC composites within 17.5 vol % β-SiC. The PVDF/β-SiC composites show dielectric constants comparable to those of the three-phase composites only when the β-SiC volume fraction is 20.0%, whereas the dielectric loss of the PVDF/β-SiC composites was much higher than that of the three-phase composites. The frequency dependence of the dielectric property for the composites was investigated by using broad-band (10–2–106Hz) dielectric spectroscopy.

High dielectric constant (k) polymer nanocomposites have shown great potential in dielectric and energy storage applications in the past few decades. The introduction of high-knanomaterials into ferroelectric polymers has proven to be a promising strategy for the fabrication of high-knanocomposites. One-dimensional large-aspect-ratio nanowires exhibit superiority in enhancing kvalues and energy density of polymer nanocomposites in comparison to their spherical counterparts. However, the impact of their intrinsic properties on the dielectric properties of polymer nanocomposites has been seldom investigated. Herein, four kinds of nanowires (Na2Ti3O7, TiO2, BaTiO3, and SrTiO3) with different inherent characteristics are elaborately selected to fabricate high-kferroelectric polymer nanocomposites. Dopamine functionalization facilitates the excellent dispersion of these nanowires in the ferroelectric polymer matrix because of the strong polymer/nanowire interfacial adhesion. A thorough comparative study on the dielectric properties and energy storage capability of the nanowires-based nanocomposites has been presented. The results reveal that, among the four types of nanowires, BaTiO3NWs show the best potential in improving the energy storage capability of the proposed nanocomposites, resulting from the most signficant increase of kwhile retaining the rather low dielectric loss and leakage current.

For rapid evaluation of fish freshness, a colorimetric sensor array has been developed for the sensitive detection to measure simultaneously TVB-N and Kvalue of fish during its storage period. Silver carps were taken as fish samples which were stored at constant temperature of 4 °C during experiment period. 10 kinds of porphyrin compounds and 6 pH indicators were selected as chromogenic materials in this experiment according to the previous study and the theoretical research. For comparison, total volatile basic nitrogen (TVB-N) values of fishes were tested by conventional chemical method, and the K-values were measured using High Performance Liquid Chromatography (HPLC). As sensing materials used in the sensor array were chromogenic, the color of the sensor array changed when reacting with odor emitted by fish sample. The color change profiles of the sensor array before and after exposure to the odor of each sample were got using image processing method. And color features were extracted to be analyzed using principal component analysis (PCA), linear discriminant analysis (LDA). The relationship between these analysis results and the TVB-N values and K-values obtained by conventional methods were established using support vector regression (SVR). And therefore models were set up for rapid prediction of TVB-N values and K-values, respectively. For the SVR model of TVB-N content and K-values, calibration correlation coefficient (Rtr) was 0.8564 and 0.8712, and the root mean square error of calibration (RMSEC) was 4.2177 and 0.06127, respectively. It is feasible to predict TVB-N values and K-values according to experiment results of colorimetric sensor array. The results indicated that the novel method based on colorimetric sensor array developed provide a feasible way for rapid and nondestructive evaluation of fish freshness.

The interfacial region plays a critical role in determining the electrical properties and energy storage density of dielectric polymer nanocomposites. However, we still know a little about the effects of electrical properties of the interfacial regions on the electrical properties and energy storage of dielectric polymer nanocomposites. In this work, three types of core–shell structured polymer@BaTiO3nanoparticles with polymer shells having different electrical properties were used as fillers to prepare ferroelectric polymer nanocomposites. All the polymer@BaTiO3nanoparticles were prepared by surface-initiated reversible-addition–fragmentation chain transfer (RAFT) polymerization, and the polymer shells were controlled to have the same thickness. The morphology, crystal structure, frequency-dependent dielectric properties, breakdown strength, leakage currents, energy storage capability, and energy storage efficiency of the polymer nanocomposites were investigated. On the other hand, the pure polymers having the same molecular structure as the shells of polymer@BaTiO3nanoparticles were also prepared by RAFT polymerization, and their electrical properties were provided. Our results show that, to achieve nanocomposites with high discharged energy density, the core–shell nanoparticle filler should simultaneously have high dielectric constant and low electrical conductivity. On the other hand, the breakdown strength of the polymer@BaTiO3-based nanocomposites is highly affected by the electrical properties of the polymer shells. It is believed that the electrical conductivity of the polymer shells should be as low as possible to achieve nanocomposites with high breakdown strength.

The poor interfacial interaction between carbon fiber (CF) and a matrix is the main factor restricting the enhancement in performance of carbon-matrix composites. Herein, CF was modified via a facile high-speed blending with matrix pitch-cokes particles. AFM force measurements and 3D particle tracking simulations unlocked the blending CF@pitch-cokes assembly mechanism. Inspired by the strong interaction between tree roots and soil, a tree-root-like reinforced structure was designed and developed in carbon-matrix composites by the subsequent carbonization coupling effect between the pitch-cokes adsorbed CF surface and the carbonized matrix. It was found that the tree-root-like structure significantly improved the interfacial interaction and enhanced the mechanical properties of the carbon-matrix composites. Compared with the pristine CF reinforced composites, the compressive strength (158.33 ± 1.95 MPa) and flexural strength (36.65 ± 1.32 MPa) of the carbon-matrix composites with tree-root-like structures increased by 101.4% and 65.8%, respectively. A mechanical interlock mechanism is suggested to explain the enhanced mechanical properties of the composites. This work provides a facile strategy for improving the interface of CF-reinforced carbon-matrix composites and paves the way for scalable, low-cost, and environment-friendly processing of high strength composites.

Nanodielectric materials with high dielectric constant, low dielectric loss, and high energy storage capability are highly desirable in modern electric and electronics industries. It has been proved that the preparation of core–shell structured dielectric polymer nanocomposites via “grafting from” method is an effective approach to these materials. However, by using this approach, the deep understanding of the structure–dielectric property relationship of the core–shell structured nanodielectrics has been limited because of the lack of detailed information (e.g., molecular weight, grafting density) about the macromolecules grafted onto the nanoparticle surfaces. In this work, by the combination of reversible addition–fragmentation chain transfer (RAFT) polymerization and thiol–ene click reaction, two types of core–shell structured polymer@BaTiO3(polymer@BT) nanocomposites with high dielectric constant and low dielectric loss were successfully prepared via a “grafting to” method. Compared with the “grafting from” method, this “grafting to” method has two merits: the molecular weight of the polymer chains in the shell layer can be easily controlled and the grafting density can be tailored by changing the molecular weight of the grafting polymer. Moreover, a clear insight into the relationship among the dielectric properties and energy storage capability of the core–shell structured polymer@BT nanocomposites, the molecular weight of the polymer chains, and the grafting density of the core–shell structured nanoparticles was achieved. The study provides new insights into the design and preparation of nanodielectric materials with desirable dielectric properties.

A colorimetric sensor array is a rapid and high sensitivity sensor for the detection and identification of volatile organic compounds. Theoretical investigations are performed to study the binding ability of the colorimetric sensor array with volatile organic compounds. Cobalt-porphyrin is selected to investigate the binding ability of the colorimetric sensor array with small volatile organic compounds. The binding energy of cobalt-porphyrin with small volatile organic compounds, such as O2, N2, H2S, trimethylamine, propanol, propane, ethyl acetate, butanone and so on, is investigated using density functional theory (DFT) methods at three different spin multiplicities: low-spin (singlet), intermediate-spin (triplet) and high-spin (quintet) states. The relative and absolute binding energies of all the complexes are obtained at the optimized geometries. The triplet state is found to have the lowest energy for the CoP–O2complex, whereas the singlet state has the lowest energy for the other complexes. The binding energies for the complexes considered are in order starting from the lowest energy state: H2S < propane < O2< N2< ethyl acetate < butanone < propanol < trimethylamine. This theoretical result can be used to optimize the sensor to increase the detection ability of the colorimetric sensor array.

To achieve the rapid and nondestructive determination of bamboo shoots lignification associated with crude fiber content and firmness, Fourier transform near infrared (FT-NIR) spectroscopy technique was used in this paper. The identification of efficient spectral variables selection algorithms: backward interval PLS (Bi-PLS), Monte Carlo uninformative variables elimination method (MC-UVE), competitive adaptive reweighted sampling (CARS) and genetic algorithms (GA) were also discussed. The partial least squares (PLS) algorithm was applied to establish prediction models for crude fiber content and firmness after spectral preprocessing and variables selection. The correlation coefficient (R) and root mean square error of prediction (RMSEP) were used to assess predictive effects of PLS models. Modeling results showed that the CARS-GA-PLS model was prime for crude fiber content prediction (R= 0.9508, RMSEP = 0.0598), and the CARS-PLS model was superior for firmness prediction (R= 0.9681, RMSEP = 0.8003). The overall results sufficiently demonstrated that the FT-NIR spectroscopy technique could determine successfully crude fiber content and firmness of postharvest bamboo shoots.

Rapid and nondestructive measurement of freshness is essential for the control of fish and the quality and safety of its products. In this study, Kvalue was measured by high performance liquid chromatography (HPLC) and employed as an index of fish freshness. The prediction models of the silver chub freshness were developed using Fourier Transform Near Infrared Reflectance Spectroscopy (FT-NIRS) with Several Partial Least Squares (PLS, i-PLS, Si-PLS), Support Vector Machines Regression (SVMR) and Synergy interval plus Support Vector Machine Regression leading to Si-SVMR. By comparison, the performance of Si-SVMR model was superior to the others for the prediction of Kvalue, where RMSECV = 0.027095 and Rc= 95.59% for the calibration set, whereas RMSEP = 0.036525 and Rp= 93.74% for the prediction set. The results indicated that FT-NIR spectroscopy together with Si-SVMR model could be a reliable method for the detection of fish freshness.

Total polyphenols content (TPC) is an important measure of phytochemicals in cocoa beans due to its numerous health benefits. This work attempts to measure the total polyphenols content in cocoa beans by using a novel approach of integrating near infrared spectroscopy (NIRS) and electronic tongue (ET). 110 samples of cocoa beans with different polyphenol content were used for data acquisition by NIRS and ET. The optimum individual characteristic variables were extracted and scaled by normalization in principal component analysis (PCA). Support vector machine regression (SVMR) was used to construct the model. The performance of the final model was evaluated according to: correlation coefficient (Rpre), root mean square error of prediction (RMSEP) and bias in the prediction set. Compared with a single technique (NIRS or ET), the data fusion was superior for the determination of TPC in cocoa beans. The optimal data fusion model was achieved with: Rpre= 0.982, RMSEP = 0.900 g g−1and bias = 0.013 in the prediction set. The overall results demonstrate that integrating NIRS and ET is possible and could improve the prediction of TPC in cocoa beans.

Polymer nanocomposites with high dielectric constant have extensive applications in the electronic and electrical industry because of ease of processing and low cost. Blending and in situpolymerization are two conventional methods for the preparation of polymer nanocomposites. However, the resulting nanocomposites, particularly highly filled nanocomposites, generally have some disadvantages such as high dielectric loss and low dielectric constant and thus show low energy density and low energy efficiency. Here we developed a core@double-shell strategy to prepare barium titanate (BT)-based high performance polymer nanocomposites, in which the first shell is hyperbranched aromatic polyamide (HBP) and the second shell is poly(methyl methacrylate) (PMMA). This method utilized the advantages of both polymer shells, resulting in superior dielectric property which cannot be achieved in nanocomposites prepared by the conventional blending methods. It is found that, compared with the conventional solution blended BT/PMMA nanocomposites, the core@double-shell structured BT@HBP@PMMA nanocomposites had higher dielectric constant and lower dielectric loss. The energy densities of BT@HBP@PMMA nanocomposites were higher than that of BT/PMMA nanocomposites accordingly. The dielectric response of the nanocomposites was analyzed, and the mechanisms resulting in the higher dielectric constant and lower dielectric loss in BT@HBP@PMMA nanocomposites were proposed. This study suggests that the core@double-shell strategy shows strong potential for preparing polymer nanocomposites with desirable dielectric properties.

Polymer nanocomposites with the dielectric constant comparable to that of percolative composites are successfully prepared by using core–shell structured hyperbranched aromatic polyamide grafted barium titanate (BT-HBP) hybrid nanofiller. Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (PVDF-TrFE-CFE) was used as the polymer matrix because of its high intrinsic dielectric constant and easy processability. The BT-HBP hybrid nanofiller were prepared by a solution polymerization of diaminobenzoic acid on the surface of amino-funcationalized BT nanoparticles. Nuclear magnetic resonance (1H NMR) and transmission electron microscopy (TEM) were used to verify the chemical structure of the hyperbranched aromatic polyamide and core-shell structure of the hybrid filler, respectively. It was found that the nanocomposite with 40 vol % BaTiO3–HBP had a dielectric constant of 1485.5 at 1000 Hz, whereas the corresponding nanocomposite sample with untreated BaTiO3only showed a dielectric constant of 206.3. Compared with classic percolative composites, the advantage of the PVDF-TrFE-CFE/BaTiO3–HBP nanocomposites is that the composites show high enough breakdown strength and high dielectric constant simultaneously. An enhanced interfacial polarization mechanism between the BT-HBP and the polymer matrix was suggested for understanding the observed unusually high dielectric constant.

A new method was developed to detect fish freshness nondestructively by combining electronic nose (E-nose) and electronic tongue (E-tongue) in conjunction with chemometric methods. An E-nose with nine metal oxide semiconductor gas sensors and a commercial E-tongue were employed in this research. Pseudosciaena croceastored at 4 °C for different days were used as experimental samples. Total viable counts (TVC) of the fish were detected by the conventional method. E-nose and E-tongue data were analyzed by principal component analysis. Three-layer radial basis function neural network (RBF-NN) models were established for qualitative discrimination of the fish freshness. Performances of RBF-NN models with different numbers of principal components (PCs) as the input were compared. Experimental results revealed that the best RBF-NN model was acquired at seven PCs of E-nose data with an optimal performance of 87.9% and 80.0% in the training set and prediction set respectively. While, the best RBF-NN model of E-tongue data analysis was at five PCs with an optimal performance of 86.3% in the training set and 81.8% in prediction set. Another RBF-NN model was built with the combination of E-nose and E-tongue. The result shows that the discrimination rates improved to 94.0% and 93.9% in the training set and prediction set respectively. A support vector machine regression model was applied to establish a relationship between the combined data from E-nose and E-tongue and from TVC values for quantitative determination. A high correlation was found between the merged data and the parameter of TVC with correlation coefficients more than 0.91. The results proved that, a single system of E-nose and E-tongue was enough to classify samples stored on different days at 4 °C, while a higher discrimination rate was acquired by the combination of the two sensors. The combined system could also be used to quantitatively evaluate the fish freshness. In conclusion, the combined system of E-nose and E-tongue in conjunction with appropriate chemometric analysis methods can conveniently and nondestructively evaluate the freshness of fish stored at 4 °C.

Utilizing synergetic effects of different fillers is an important strategy to design and develop high-performance nanocomposites. However, owing to the well-known problems such as dispersion, solution viscosity control, and so on, synergetic enhancement effects are usually offset by the defects induced by fillers in highly loaded nanocomposites. In this work, remarkable synergetic efficiency was realized in graphene nanoplatelet (GNP) and multiwalled carbon nanotube (CNT) highly loaded epoxy composites through a well-designed fabrication method. Dramatic thermal conductivity enhancement was observed in the epoxy composites with 10–50 vol% nanocarbon filler due to synergetic effects. For example, the composite with 20 vol% CNTs and 20 vol% GNPs possess a thermal conductivity up to 6.31 W/mK. This is even much higher than that of the composites with individual 50 vol % CNTs or 50 vol% GNPs. A maximum thermal conductivity 7.30 W/mK was obtained, which is 38-fold of that of the pure epoxy resin. Thermal transport channels in the composites were thoroughly analyzed, and the mechanism of high synergetic effects achieved in thermal conductivity enhancement was discussed from the viewpoints of intrinsic properties, dispersion, contact, and matrix interaction of the fillers.

High dielectric constant polymer composites capable of withstanding a high electrical field have much application in electronic devices and electrical equipment because of their ease of processing, flexibility, and low cost. Conventional polymer composites with a high dielectric constant, namely ceramic particulate composites and conductive filler based percolative composites, either show low dielectric enhancement or cannot withstand high electric field. Here we report a new strategy for preparing high dielectric constant polymer composites by using novel three-dimensional zinc oxide (3D ZnO) superstructures as fillers. Two kinds of 3D ZnO (flower-like and walnut-like) superstructures were prepared via a template-free solvothermal method. Their poly(vinylidene fluoride) (PVDF) composites as well as commercial ZnO filled PVDF composite were investigated by a broadband dielectric spectroscopy at a wide temperature range (−50 to +150 °C). Our results showed that, compared with the commercial ZnO, the newly synthesized ZnO superstructures not only significantly increase the dielectric constant of their PVDF composites but also show similar effect on the breakdown strength of their composites. For instance, the dielectric constants (100 Hz) of the composite samples with commercial ZnO, flower-like, and walnut-like ZnO superstructures are 19.4, 221.1, and 104.9, respectively, whereas their breakdown strengths are 45, 42, and 40 kV/mm, respectively. The dielectric investigation evidenced that the higher dielectric constant in the composites with ZnO superstructures should be attributed to the formation of a ZnO percolation network.