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Significantly Enhanced Energy Density by Tailoring the Interface in a Hierarchical-Structured TiO2-BaTiO3-TiO2 Nanofillers in PVDF Based Thin Film Polymer Nanocomposite
摘要： Dielectric polymer nanocomposites with high breakdown field and high dielectric constant have drawn significant attention in modern electrical and electronic industries due to their potential applications in dielectric and energy storage systems. The interfaces of the nanomaterials play a significant role in improving the dielectric performance of polymer nanocomposites. In this work, polydopamine (dopa) functionalized TiO2-BaTiO3-TiO2 (TiO2-BT-TiO2@dopa) core@double-shell nanoparticles have been developed as novel nanofillers for high energy density capacitor application. The hierarchically designed nanofillers help in tailoring the interfaces surrounding the polymer matrix as well as act as individual capacitors in which core and outer TiO2 shell functions as capacitor plate because of their high electrical conductivity while the middle BT layer functions as a dielectric medium due to high dielectric constant. Detailed electrical characterizations have revealed that TiO2-BT-TiO2@dopa/PVDF possess maximum relative dielectric permittivity (εr), breakdown strength (Eb), as well as energy densities in comparison to PVDF, TiO2/PVDF, TiO2@dopa/PVDF, TiO2-BT@dopa/PVDF polymer nanocomposites. The εr and energy density of TiO2-BT-TiO2@dopa/PVDF was 12.6 at 1 kHz and 4.4 J cm-3 at 3128 kV cm-1, respectively, which was comparatively much higher than commercially available biaxially oriented polypropylene (BOPP) having εr of 2.2 and the energy density of 1.2 J cm-3 at much higher electric field of 6400 kV cm-1. It is expected that these results will further open new avenues for the design of novel architecture for high-performance polymer nanocomposites-based capacitors having core@multishell nanofillers with tailored interfaces.
关键词： capacitors,polymer nanocomposites,core-shell nanomaterials,dielectrics,BaTiO3 nanoparticles
更新于2025-11-14 15:19:41
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Light-induced EPR study of spin-assisted charge transport in PFOT:PC61BM composite
摘要： Magnetic resonance, relaxation and dynamic parameters of polaron spins and methanfullerene radical anions, initiated by the infrared-visible-ultraviolet photons in bulk heterojunctions of the composite formed by narrow-band poly[(9,9-dioctylfluorenyl-2.7-diyl)-co-(bithiophene)] (PFOT, F8T2) copolymer and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) globules were investigated by the direct Light-Induced Electron Paramagnetic Resonance (LEPR) spectroscopy. It was shown that some of the polarons are captured by spin traps formed in the copolymer matrix due to its disordering. The number, spatial distribution and energy depth of such traps depend on the structure and morphology of composite. It is shown that the main parameters of both charge carriers are determined by the exchange interaction of the spin ensembles, as well as the energy of the photons. The formation of spin traps in the copolymer matrix and the exchange interaction between different spin packets cause the extreme sensitivity of the composite's magnetic resonance and electronic parameters to the number and energy of the initiating photons. The predominant photoinitiation of localized polarons in the copolymer matrix was demonstrated. This process is substantially accelerated when the composite is illuminated by photons with the energy lying near 1.8 and 2.7 eV. The recombination of both charge carriers can be described in terms of a bimolecular process of the second order. It was found that the contributions of polarons and methanofullerene radical anions to the effective paramagnetic susceptibility increase substantially near the photon energy of 2.6 and 2.1 eV due to the exchange interaction of these charge carriers. It is shown that the mobility of polarons varies monotonically throughout all the photon energy range, whereas the librational spin dynamics of the methanofullerene globules is substantially accelerated near the photon energy of 2.0 and 2.7 eV.
关键词： Polymer nanocomposites,Spin recombination,Transport properties,Spin interaction,Polaron,Light-induced EPR
更新于2025-09-23 15:23:52
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Preparation and Characterization of Polymer Composite Materials Based on PLA/TiO2 for Antibacterial Packaging
摘要： Polymer composite materials based on polylactic acid (PLA) filled with titanium dioxide (TiO2) nanoparticles were prepared. The aim of this work was to investigate the antibacterial action of TiO2 against a strain of E. coli (DH5α) to obtain information on their potential uses in food and agro-alimentary industry. PLA/TiO2 systems were prepared by a two-step process: Solvent casting followed by a hot-pressing step. Characterization was done as a function of particle size (21 nm and <100 nm) and particle content (0%, 1%, 5%, 10%, and 20%, wt %). Structural characterization carried out by X-ray diffraction (XRD) and Fourier Transformed Infrared spectroscopy (FTIR) did not reveal significant changes in polymer structure due to the presence of TiO2 nanoparticles. Thermal characterization indicated that thermal transitions, measured by differential scanning calorimetry (DSC), did not vary, irrespective of size or content, whereas thermogravimetric analysis (TGA) revealed a slight increase in the temperature of degradation with particle content. Bacterial growth and biofilm formation on the surface of the composites against DH5α Escherichia coli was studied. Results suggested that the presence of TiO2 nanoparticles decreases the amount of extracellular polymeric substance (EPS) and limits bacterial growth. The inhibition distances estimated with the Kirby-Bauer were doubled when 1% TiO2 nanoparticles were introduced in PLA, though no significant differences were obtained for higher contents in TiO2 NPs.
关键词： antibacterial packaging,polylactic acid (PLA),polymer nanocomposites,TiO2 nanoparticles
更新于2025-09-23 15:22:29
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Role of Graphene-Doped Organic/Polymer Nanocomposites on the Electronic Properties of Schottky Junction Structures for Photocell Applications
摘要： In this study, the current–voltage characteristics of non-doped and distinct graphene (Gr)-doped polyvinyl alcohol (PVA) interlayers in metal/organic polymer semiconductor type Schottky junction structures (SJSs) were investigated on both forward and reverse biases under distinct levels of illumination. The distinct doping concentration ratios (1%, 3% and 7%) of the Gr added to the PVA interlayers were compared by taking into account the basic electrical parameters, such as saturation current (Io), ideality factor (n), barrier height (UBo), series (Rs) and shunt resistance (Rsh). The 7% Gr-doped structure displayed the lowest Io values at zero bias. Moreover, the results indicated that the 7% Gr-doped PVA decreased the n value but increased the UBo value compared with values associated with structures that have different doping concentrations. In terms of quality and reliability, the Rs and Rsh values of the SJSs were obtained using Ohm’s law and Cheung’s functions, and the 7% Gr-doped structure eventually displayed more uniformly distributed and lower Rs values and the highest Rsh values. Consequently, the 7% Gr-doped structure had better overall quality because of its superior electrical properties compared with structures that have other doping concentrations. Therefore, the 7% Gr-doped structure can be used as a photodiode in electronic devices.
关键词： photovoltaic,basic electronic properties,organic polymer nanocomposites,Graphene,I–V characteristics
更新于2025-09-23 15:21:21
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Upconversion luminescence properties of Y2O3: Yb3+/Er3+/Tm3+ nanocrystal doped PMMA nanocomposites
摘要： Y2O3 nanocrystals triply doped with Yb3+, Er3+, Tm3+ ions were synthesized via alginic acid-assisted gelation using thermal decomposition method and annealed at 800 °C for 24 h. Nanopowders were embedded into PMMA matrix via free-radical polymerization in an ultrasonic bath. X-ray diffraction and transmission electron microscopy measurements have shown that the crystal grain sizes decreased significantly with the narrow size distributions of the nanocrystals in PMMA matrix. A diode laser at 975 nm was used to measure the upconversion luminescence of the annealed nanopowders and those embedded in PMMA between the 400–850 nm wavelength region. The Er3+ concentration and the excitation power density dependencies of the relative intensities for red, green and blue upconversion luminescence in the nanopowder and PMMA nanocomposites are found to be different. The measured CIE-1931 color coordinates of the upconversion luminescence in PMMA nanocomposites show appreciable color stability under different excitation power densities, which is required for potential applications in the field of photonics.
关键词： Color Tunable Emission,Upconversion Luminescence,Polymer nanocomposites,Color Stability,Polymethyl methacrylate (PMMA)
更新于2025-09-23 15:21:21
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High-Performance Biobased Unsaturated Polyester Nanocomposites with Very Low Loadings of Graphene
摘要： Graphene-reinforced tung oil (TO)-based unsaturated polyester nanocomposites were prepared via in situ melt polycondensation intergrated with Diels–Alder addition. Functionalized graphene sheets derived from graphene oxide (GO) were then extracted from the obtained nanocomposites and carefully characterized. Furthermore, dispersion state of the graphene nanosheets in the cured polymer composites and ultimate properties of the resultant biobased nanocomposites were investigated. Mechanical and thermal properties of the TO-based unsaturated polyester resin (UPR) were greatly improved by the incorporation of GO. For example, at the optimal GO content (only 0.10 wt %), the obtained biobased nanocomposite showed tensile strength and modulus of 43.2 MPa and 2.62 GPa, and Tg of 105.2 ?C, which were 159%, 191%, and 49.4% higher than those of the unreinforced UPR/TO resin, respectively. Compared to neat UPR, the biobased UPR nanocomposite with 0.1 wt % of GO even demonstrated superior comprehensive properties (comparable stiffness and Tg, while better toughness and thermal stability). Therefore, the developed biobased UPR nanocomposites are very promising to be applied in structural plastics.
关键词： unsaturated polyester resins,graphene,in situ melt polycondensation,tung oil,biobased polymer nanocomposites
更新于2025-09-23 15:21:21
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Optimization of Quantum Yield of Highly Luminescent Graphene Oxide Quantum Dots and Their Application in Resistive Memory Devices
摘要： A facile chemical method of acid treatment has been followed for the cutting of graphene oxides (GOs) sheet to extract graphene oxide quantum dots (GOQDs) in aqueous medium at different pH. Strong blue emission and excitation dependent photoluminescence (PL) spectrum are observed in GOQDs synthesized at pH11. Presence of defect related states and oxygen containing functional groups in GOQDs are confirmed through Raman and fourier transform infrared (FTIR) analysis, respectively. High resolution transmission electron microscopy (HR-TEM) analysis suggests that the sizes of GOQDs are distributed in the range ~2.0 to 8.0 nm with d-spacing of 0.245 nm. AFM measurement confirms the topography height of GOQDs in the range ~ 6.0-9.0 nm. Synthesized GOQDs at different pH are dispersed in poly (vinyl alcohol) (PVA) matrix and spin coated to fabricate polymer nanocomposites (PNCs) devices. Electrical studies have been performed which display write-once-read-many (WORM) characteristics and the set voltage (????????) increases with the increase in pH of the GOQDs. Very low ???????? ~ - 0.9 V and ??????/???????? ~104 have been obtained for the device containing GOQDs synthesized at pH1. Retention tests up to 104 s are performed for the PNCs devices in order to confirm the stability. A suitable energy band diagram is proposed to discuss the carrier transport through the composites devices.
关键词： Polymer nanocomposites,GOQDs,Blue emission,WORM,Quantum yield
更新于2025-09-23 15:19:57
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Finely depressed dielectric loss and conductivity achieved in high-kappa stannic oxide/polymer nanocomposites from surfactant-assisted electric percolation
摘要： During past decades, both of interface polarization and electric percolation mechanisms have been found to have a significant influence on the dielectric and conductive properties of polymer based nanocomposites bearing electrically conducting nanoparticles. Although the significantly elevated high dielectric constant of composites has gained great success, the finely balanced high dielectric constant, depressed dielectric loss and low conductivity have been faced with a huge challenge. Instead of the high-cost organic modification onto the surfaces of inorganic conductive nanofiller, in current work, a small quantity of polyvinylpyrrolidone surfactant was introduced to prepare the ternary polymer based nanocomposite films bearing stannic oxide nanoparticles. Their dielectric and conductive performances were compared with that of the corresponding binary composites without bearing that surfactant. The positive influence of that surfactant on the finely balanced high comprehensive electric properties of composites namely high dielectric constant and depressed loss/conductivity was confirmed due to the improving of interface compatibility and depressing of interface air voids. The ternary nanocomposite bearing 10 vol% filler could have a dielectric constant of ca. 175, loss of ca. 0.35 and conductivity of ca. 1.8 × 10?5 S cm?1 at 1 kHz under 1 V bias voltage. This work might open the door to the large-scale fabrication of promising composite dielectrics materials by facilely introducing the third surfactant component.
关键词： surfactant,stannic oxide,dielectric properties,polymer nanocomposites,electric percolation
更新于2025-09-23 15:19:57
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Peculiarities of holographic microfabrication of photonic structures in functional polymer nanocomposites
摘要： Light sensitive polymer nanocomposites may be used for holographic recording of di?ractive optical elements due to the formation of periodical refractive index modulation in the volume or/and due to the geometrical surface relief formation [1–4]. In comparison with simple organic photosensitive materials polymer nanocomposites with organic and inorganic nanoparticles possess additional variable parameters, which can upgrade the quality and functionality of the recorded elements, photonic structures including the creation of layers with different thickness, plasticity, stability, luminescence properties and not least applicability in di?erent environments, biology and medicine. The holographic recording in polymer nanocomposites consists of the simple polymerization processes as well as processes of volume di?usion, redistribution of di?erent nanoparticles [1–4]. But the in?uence of matrix, initiator compositions and properties as well as of their optical parameters, which can in?uence the level of scattered light, absorption at the selected optical wavelengths, and their interconnection with optimal recording conditions are still not investigated in detail. We elaborated few high transparent polymer nanocomposites with low light scattering levels for surface relief and volume photonic structures recording - gratings and 2D photonic structures [5]. Our last investigations showed the applicability of multi-beam interference method of holographic recording for creation of one-, two- or even three-dimensional structures on the surface and in the volume of nanocomposite layer [6]. Few initial experiments demonstrated that these nanocomposites are biocompatible. In the present paper we summarized the results of the investigations of interrelation between the initial composition of urethane-acrylate nanocomposites with silica nanoparticles, optical parameters, holographic recording and di?raction e?ciency of resulting, spatially modulated structures.
关键词： Di?ractive elements,Polymer nanocomposites,Photonic structure,Holographic recording
更新于2025-09-19 17:15:36
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Thermally Superstable Cellulosic-Nanorod-Reinforced Transparent Substrates Featuring Microscale Surface Patterns
摘要： The recent rapid expansion of thin-film, bendable, and wearable consumer (opto)electronics demands flexible and transparent substrates other than glass. Plastics are the traditional choice, but they require amelioration because of their thermal instability. Here, we report the successful conversion of a soft and thermally vulnerable polymer into a highly thermally stable transparent nanocomposite material. This is achieved by the meticulous choice of a polymer with a glass-transition temperature below 0 °C that gives stable mechanics above room temperature, reinforcing the polymer with a load-bearing hierarchical network of the incredibly strong and stable natural material: cellulose nanorods. Owing to the Pickering emulsification process, the nanocomposites inherit the self-assembled structural hierarchy from the cellulose nanorod-encapsulated resin droplets. The ameliorated nanocomposites have highly desirable high-temperature endurance (～150?180 °C) in terms of the thermomechanical, thermodimensional, and thermo-optical performance. Any photonic nano- or microstructures can be directly molded on the surface of the nanocomposites in high precision for better light management in photonic and optoelectronic applications. The highlight of this work is the demonstration of a highly thermally stable microlens array on the ameliorated transparent nanocomposite.
关键词： thermal stability,polymer nanocomposites,flexible electronics,Pickering emulsion,microlens array,nanocellulose
更新于2025-09-19 17:15:36