Pure Films Research Articles

Multifunctional honeysuckle extract/attapulgite/chitosan composite films containing natural carbon dots for intelligent food packaging

In order to fulfill people's requirements for food quality and safety, it is a promising strategy to develop intelligent biodegradable food packaging materials. Herein, honeysuckle extracts/attapulgite/chitosan composite films containing natural carbon dots were fabricated for intelligent food packaging. Different characterization techniques were employed to study the obtained composite films, while the physicochemical properties, optical properties, antibacterial and antioxidant activities of composite films were determined. The obtained composite films presented good mechanical, antibacterial and antioxidant properties, and the antibacterial ratios of composite films against Escherichia coli and Staphylococcus aureus were 99.27 ± 0.18 % and 98.85 ± 0.65 %, respectively. When the added amount of honeysuckle extracts/attapulgite nanocomposites was 4.76 %, the tensile strength and elongation at break of composite films reached 24.9 ± 2.35 MPa and 64.8 ± 2.11 %, respectively, which were obviously higher than that of pure chitosan film. Furthermore, the composite films exhibited excellent UV shielding and blue fluorescence properties, as well as pH-sensitivity due to the presence of caffeoquinic acid-based natural carbon dots derived from honeysuckle extract. Therefore, the composite films indicated a potential application for intelligent food packaging.

In Situ Surface Polymerization of PANI/SWCNT Bilayer Film: Effective Composite for Improving Seebeck Coefficient and Power Factor

AbstractFlexible thermoelectric composites are promising in harvesting low‐temperature energies and have a wide range of applications in wearable devices. However, the uncontrollable interfaces between the components significantly scatter the transport of electrons leading to a reduced thermoelectric performance. In this research, hydrochloride acid doped polyaniline (PANI) is directly prepared on the surface of a single‐walled carbon nanotube (SWCNT) film to form a bilayer structure in controlling the interfacial filtering effect and preserve the high conductivity. Under optimal conditions, a PANI/SWCNT bilayer composite exhibits a Seebeck coefficient of 26 µVK−1 at near room temperature, and a high electrical conductivity of 1320 S cm−1 is maintained. The Seebeck coefficient is a twofold increase compared to a pure SWCNT film, while the power factor is three times the value from a pure SWCNT film and 500 times that from a solution‐mixed PANI/SWCNT composite. The enhanced thermoelectric performance is attributed to SWCNT‐assisted growth through π–π interaction promoting the formation of an oriented and compacted PANI layer, and the bilayer structure can also maximally maintain the electrical conductivity of the composite. The bilayer composite has then been investigated as an energy harvester and a temperature sensor, indicating its reliable performance in wearable applications.

An innovative strategy to enhance the interfacial interaction and effective contribution of BN in thermal conductivity in aramid based composites films

With the escalating concern over electronic device overheating, BN/polymer based thermal conductive composites have experienced remarkable growth in the field of heat dissipation. However, it is challenging to enhance the thermal conductivity of composites while preserving strong interfacial interaction due to the dilemma of chemical inertness of BN, interfacial thermal resistance and filler-polymer interaction. Herein, we utilized the adjustable surface charge of polydopamine under varying pH to fabricate composite films comprising polydopamine-modified boron nitride nanosheets and aramid sheets (BNNS@PDA/ANFS) by electrostatic assembly. The thermal conductivity of the composite rose to 36.9 W/m⋅K−1 with only 20 wt% filler. According to Density functional theory (DFT) simulation and interface thermal resistance calculation, the electrostatic assembly enhanced interface interactions and greatly reduced thermal resistance barrier. Furthermore, the optimal tensile strength of 304 MPa, is 2.32 times higher than pure ANFS film, accompanied by toughness of 33.2 MJ/m−3. These superior performances are the results of a synergistic strategy, combining interfacial and topological enhancements. This work provides an innovative approach to enhance effective filler contribution in matrix and underscores the significant potential of BNNS@PDA/ANFS composite films in applications related to heat management.

Preparation and study on electrical/thermal properties of epoxy/polyacrylate rubber composite dielectric

AbstractWith the development of power systems and electronic devices, epoxy resin (EP) is facing increasingly severe operating environments, and its performance may not meet expectations. In order to broaden the application of EP, the DE/EP composite films were prepared with EP as matrix, polyacrylic rubber dielectric elastomer (DE) as reinforcement materials. The structure of DE/EP composite films was characterized by XRD, SEM, and other methods, and the electrical and thermal properties of the materials were tested and studied. The study found that with appropriate dissolution and stirring treatment, DE can be evenly dispersed in the EP matrix, and the introduction of DE does not significantly affect the structure of the EP molecular chain, also found the introduction of DE improve the electrical and thermal properties of EP. The breakdown strength of the 4% DE/EP composite film surpasses that of the pure EP film by 15.58%. Additionally, the thermal conductivity of the 8% DE/EP composite film is elevated by 41.6% compared to the pure EP film, while its dielectric constant is also enhanced by 8.2%. This work may provide a theoretical basis for studying the application of EP modified system in electrical engineering, integrated circuit packaging and other fields.

Synthesis of MnO@Fe2O3 core-shell doped PVA/PVP polymeric nanocomposites for electronic and optoelectronic devices: Mechanical, electrical, and optical properties

Abstract The aqueous solution cast method was utilized to create biodegradable nanocomposite of polymers (PNC) films from a poly (vinyl alcohol) / poly (vinyl pyrrolidone) blend (70/30 wt%) and MnO@Fe2O3 nFs. The dislocation density, particle size, and interplanar distance were all calculated. The PNC films' surface shape changes from smooth to porous and somewhat rough because of the nanosized MnO@Fe2O3 particles' dispersion in the blend matrix, which diminishes the blended crystallites' size. The composite film's tensile strength increased from 9.45 MPa for the pure (PVA-PVP) film to 22.35 MPa due to the addition of 6 wt% MnO@ Fe2O3. The optical band gap decreases from 5.26 and 4.84 eV for pure (PVA/PVP) blend direct and indirect energy band gap to 5.18 and 4.71 eV for comparable values of 6wt% MnO@Fe2O3 nFs. Up to 6 wt% MnO@Fe2O3 concentration, PNC films' dielectric permittivity first declines, but it is substantially identical to the pure polymer blend matrix. The PNC sheet's dielectric permittivity increases nonlinearly with temperature, although its DC conductivity follows the Arrhenius law. Laser power was attenuated by (PVA- PVP)/MnO@Fe2O3 for both He-Ne and solid-state green laser beams. When the MnO@Fe2O3 concentration in the blend matrix rises to 6 wt%, the output power for lasers with 532 nm and 650 nm wavelengths drops from 5.49 to 2.4 mW and 19.8 to 9.4 mW, respectively. The findings suggest that nanocomposites exist and are widely recommended for optoelectronics, microelectronics, radiation detection, and several other uses.

Incorporation of specific defects through ion bombardment for better ferroelectrics

AbstractIncorporating specific defects into complex oxides facilitates the exploration of exotic phenomena and novel functionalities based on the intricate coupling between the defects and lattice/charge. However, methods for maximizing the density of specific defects while enhancing the desired properties have been rarely explored. In this study, the effect of N+ ion bombardment‐driven specific defects on the properties of bismuth ferrite (BFO) thin films was investigated. Furthermore, atomic structure characterization and computational processing revealed the displacement and orientation of the Fe atoms, which are linearly related to the degree of polarization. The ion bombardment introduced deep‐level trap states within the lattice, leading to a significant reduction in the leakage current and improved insulation performance of the films. By precisely engineering the defect content through N+ ion bombardment, the pure BFO thin films with remarkable and stable ferroelectric properties (remnant polarization, Pr = ∼116.8 µC·cm−2; leakage current, J = ∼1.5 × 10−8 A·cm−2) were fabricated. This innovative defect engineering‐based approach enables the customization and optimization of local ferroelectric order parameters, thereby establishing a solid foundation for designing functionalities across various functional material systems.

Flexible Ti3C2Tx-Polyurethane Electrodes for Versatile Wearable Applications.

With the development of science and technology, wearable electronics are increasingly widely used in medical, environmental monitoring, and other fields. Thus, the demand for flexible electrodes is increasing. The two-dimensional material Ti3C2Tx has attracted much attention in the manufacture of flexible electrodes due to its excellent mechanical and electrical properties. However, the brittleness of pure Ti3C2Tx films has become a major obstacle for their use as flexible electrodes in wearable devices. Therefore, solving the brittleness problem of flexible electrodes based on Ti3C2Tx while maintaining the excellent performance of Ti3C2Tx has become an urgent problem. To solve this problem, Ti3C2Tx was compounded with waterborne polyurethane (WPU), and a Ti3C2Tx-WPU composite film with a hierarchical structure was constructed by evaporation-assisted self-assembly. The Ti3C2Tx-WPU composite film not only retains the excellent electrical conductivity of Ti3C2Tx (100 S m-1) but also has flexibility (20 MJ m-3). Furthermore, the Ti3C2Tx-WPU composite film is applied to functional devices such as contact pressure sensors and non-contact proximity sensors. Finally, the Ti3C2Tx-WPU composite film wearable device demonstrates its practical application potential in the field of wearable devices.

Flame retardant polyvinyl alcohol film with self‐releasing carbon dioxide and ammonia from phytic acid and urea

AbstractThis paper utilizes the reaction of phytic acid (PA) and urea (UM) in polyvinyl alcohol (PVA) solution to synthesize flame retardant gasses (CO2, NH3) for the preparation of PVA composite films containing flame retardant microbubbles. The flame retardancy of PVA composite films was assessed using methods including limiting oxygen index (LOI), vertical burning (UL 94), and cone calorimetry. The results indicated an increase in the LOI of the PVA composite film containing flame retardant microfoam from 20% to 30% compared with the pure PVA film, and that UL 94 reached VTM‐0. Furthermore, its peak exothermic rate and total exothermic amount were reduced by 36.25% and 38.92%, respectively, compared with the pure PVA film. The investigation of the flame‐retardant mechanism employed thermogravimetric‐infrared (TG‐IR), scanning electron microscopy (SEM), Raman spectroscopy, and infrared spectroscopy. The results demonstrate that the CO2 and NH3 flame retardant microbubbles within the composite film render it less ignitable at the initial stage, and that the internal UM of the composite film continues to decompose, releasing CO2 and NH3 upon heating. In addition, the acidic substances decomposed by PA during combustion promote the dehydration, cross‐linking, and cyclization of PVA, generating chemical structures such as POC, POP, and PO4 with enhanced thermal stability. This encourages the formation of a continuous, dense charcoal layer and impedes the transfer of oxygen and heat into the interior.

Influence of the reactive gas mixture on the superconducting properties of nitrogen-doped aluminum thin films

We present a correlation between disorder and superconducting properties in nitrogen-doped aluminum thin films, ranging from a few nitrogen impurities to the insulating limit due to AlN formation. Samples were deposited via reactive sputtering on (100) silicon substrates with native oxide at room temperature. Our findings show that adding nitrogen increases the superconducting critical temperature (Tc) compared to pure metal films. By varying the nitrogen/argon ratio up to 6 %, we observed a dome-like Tc behavior: 2 K at low concentrations, peaking at 3.3 K at intermediate concentrations, and then dropping as the samples become insulating (≈ 4.4 %). Increasing nitrogen raises resistivity and shifts the material from metallic to semiconductor-like behavior. Disorder impacts the upper critical field, starting at 0.2 T for low nitrogen content and reaching up to 3.2 T for nitrogen-rich samples with Tc = 2.2 K. Current-voltage curves reveal typical vortex dissipation, as expected for type II superconductors.

Can pure cellulose nanofibril films replace polyolefins as water vapor barriers in packaging?

Despite significant research into cellulose nanofibril (CNF) films as substitutes to synthetic plastic materials, commercial applications remain very limited. One major hindrance is the poor water vapor barrier properties of CNF films compared to polyolefins, a critical property for product protection, such as food safety and preservation. To date, it is unknown whether full moisture barrier properties can be achieved with materials made by the assembly of nanofibers and fibrils. A comprehensive understanding of the effect of film structure on water vapor transport properties is required. Here, over 200 films were produced with a wide range of grammages from 30 g/m2 to 580 g/m2 by casting and spray deposition. Their structures were quantified by µCT and SEM and related to their water vapor transmission rates (WVTRs). Porosity and pore connectivity decreased with increasing film grammage, which correlates with the exponential decrease in WVTR. However, the WVTR plateaued at 30 g/m2day, indicating that the known open space and adsorption diffusion mechanisms cannot be fully eliminated by producing high grammage films. Pure cellulose nanofibril films therefore cannot replace polyolefins in packaging applications, requiring modifications such as coating and nanofillers.

Synchronously enhanced breakdown strength and energy storage ability of cellulose acetate flexible films via introducing ultra-low content of carbonized polymer dots

Developing green and environmentally friendly biomass materials for energy storage and application is of great significance to sustainable development. Novel composite films containing cellulose acetate (CA) and carbonized polymer dots (CPDs) are reported herein. The CPDs have strong hydrogen bonding interactions with CA matrix, in which CPDs act as the physical crosslinking points and enhance the entanglement density of the matrix. And the composite films demonstrate a significant enhancement in breakdown strength (Eb), reaching up to 520.58 MV/m with the addition of 0.1 wt% CPDs (1.62 times higher than 321.94 MV/m of pure CA). Furthermore, the discharging energy density (Ud) achieves 2.55 J/cm3 at 450 MV/m, which is 1.36 times higher than that of the pure CA film (1.87 J/cm3 at 400 MV/m) and simultaneously, the energy efficiency (η) is maintained at 73.3 %. The Coulomb-blockade effect induced by the ultra-low content of CPDs effectively inhibiting carrier migration, and the enhanced entanglement density of the matrix improving mechanical properties and reducing polarization loss, mainly contribute to the enhanced dielectric performances. Furthermore, CPDs also improve the mechanical properties of the composite films apparently. This work provides some references for the fabrication of the next generation of environmentally friendly dielectric composite films.

Impact of PTQ11 polymer doping on the optoelectronic and structural properties of a CH3NH3PbI3 perovskite photovoltaic cell

At present, one of the most swiftly progressing domains in solar photovoltaics is perovskite-based solar cells. Chemical modification of perovskites with foreign atoms represents a potentially fruitful approach to customizing material characteristics with the aim of enhancing the functionality and durability of solar cells. In this study, we first documented the inverted structure of PTQ11 polymer-doped perovskite solar cells composed of CH3NH3PbI3 (MAPbI3) perovskite thin film. The findings indicate that the active layer morphology is enhanced through PTQ11 doping, leading to rapid suppression of photoluminescence and delayed carrier recombination. The XRD and Raman spectral analyses revealed the crystalline, single phase, tetragonal, and highly pure MAPbI3 thin film with the preferred (220) orientation. Energy gaps ranging from 1.596 eV to 1.577 eV and absorption coefficients exceeding 105 cm−1 were characteristics of the doped thin film, which varied with the doping concentration. A transition occurred on the perovskite film’s surface to form smooth, compressed pores measuring 1.63 µm in diameter. This modification potentially enhanced the photovoltaic performance by facilitating charge transport. With an open circuit voltage of 1.11 V, a power conversion efficiency (PCE) of 18.24 %, a short-circuit current density of 22.32 mA/cm2, and a fill factor of 73.65 %, the PTQ11-9 mg/mL sample constituted the solar cell device base. Hence, the findings suggest that the doping of PTQ11 polymer represents a potentially effective approach to improve the performance of perovskite solar cells.

Enhancing the mechanical properties of polylactic acid (PLA) composite films using Pueraria lobata root microcrystalline cellulose

To enhance the mechanical properties of polylactic acid (PLA) material, the PLA-based composite films are prepared by using Pueraria lobata (Willd.) Ohwi root microcrystalline cellulose (PRMCC) treated with 3-aminopropyl triethoxysilane (KH550) silane coupling agent as the dispersed phase through solvent casting method. The effects of the concentrations of PRMCC and KH550 as well as the KH550 pretreating condition (ethanol concentration) on the tensile properties of PLA-based composite films are investigated. The PLA-based composite film treated with 5 wt% PRMCC and 18 wt% KH550 (pretreated by 90 % EtOH) exhibits the greatest performance. Its elongation at break value is detected to be 4.0 %, 1.6 times as large as that of pure PLA film. The water absorption of the as-prepared PLA-based composite film is reduced from 0.49 % of the unmodified PLA/PRMCC film to 0.12 %. Moreover, the modified PLA-based composite film has a hydrophobic surface and exhibits good thermal stability. Compared with pure PLA film, the modified PLA-based composite film exhibits improved UV shielding performance with acceptable transparency. Furthermore, after adding poly(butylene adipate-co-terephthalate) (PBAT) to the composite system, the elongation at break of the PLA-based composite film is up to 7.2 %. This research can provide theoretical guidance for enhancing the performance of PLA products.

Stable low friction of sp2 nanocrystallited carbon films in different vacuum pressures

This study reported the stable low friction of sp2 nanocrystallited carbon films in vacuum environment. Carbon film with larger sp2 nanocrystallites size demonstrated consistently low friction in different vacuum pressures. The lowest friction coefficient arrived 0.018 at 10–6 Pa with a long stable sliding cycles. The mechanisms were ascribed to the stable contact interfaces formed by the rapidly transferred sp2 nanocrystallites and the oxidation passivation layer. The low shear force at the nanocrystallited interface reduced the friction and the oxidation passivation promised the stabilization of interface. Carbon film with smaller sp2 nanocrystallite size only achieved low friction of 0.023 at 10–6 Pa, and the film exhibited high friction at 10-1∼10-3 Pa due to the insufficient passivation and large dangling bonds. As pure carbon film, sp2 nanocrystallited carbon films offer broadly application possibilities for vacuum micro-/nano- devices.

Exploring the influence of Zn impurities on the structural, optical, and H2 sensor properties of ultrasonic spray pyrolysis-grown MgO thin films

Magnesium oxide (MgO) thin films, both pure and zinc (Zn) doped, were fabricated on soda lime glass substrates using ultrasonic spray pyrolysis. Zn was introduced at concentrations of 0.5 %, 1 %, 2 %, 4 %, and 8 %. The effects of these doping levels on the films' structural, morphological, optical, and H2 gas sensing properties were studied using XRD, SEM, EDAX, UV–vis spectroscopy, PL spectroscopy, gas sensing measurements, and XPS. The films showed a cubic crystal structure without secondary phases, and grain sizes generally decreased with doping. Morphological changes in nanocrystal shapes were noted due to impurities. Optimal doping enhanced MgO's absorbance, with a slight increase in bandgap. The PL spectra showed increased luminescent emissions with higher doping, due to defects from Zn ions. Pure films were responsive to H2 gas, while Zn-doped samples showed weaker responses. The XPS confirmed the expected chemical compositions.

Amphiphilic colloidal particles/Ca2+ reinforced edible agar nanocomposite film by multiple cross-linking/microphase separation strategies

The agar (AG) film exhibited poor mechanical and water-resistant properties which limited its application for food packaging. The structural modification of AG nanocomposite film greatly impacts their macroscopic properties. In this paper, edible AG nanocomposite films were achieved by incorporating colloidal particles based on conjugates of whey protein isolate (WPI) and alginate oligosaccharides (AOS) as the nanofiller to obtain the micro-phase separation structure and the multiple cross-linking network with the synergistic interactions of the Ca2+ crosslinking. Firstly, WPI-AOS colloidal particles were synthesized through the Wet-heating Maillard reaction. Good compatibility between WPI-AOS colloidal particles and AG was exhibited, resulting in improved mechanical and water-resistant properties of AG composite films. Compared to pure AG film, the tensile strength (TS) of the agar composite film with 10% WPI-AOS colloidal particles increased significantly to 81.87 MPa from 24.02 MPa, and the elongation at break (EAB) also improved to 46.25% from 18.65%. The moisture content (MC), water solubility (WS), and water vapor permeability (WVP) of the AG composite film decreased by 33.1%, 18.0%, and 22.4% respectively. In addition, the multiple cross-linking network hindered the relative sliding between the AG molecular chain, which resulted in improved thermal stability of the composite film. Using soft colloidal particles as nanofillers to fabricate edible films for improving their properties is an effective and promising strategy.

Silane modified Cr2O3/polyimide nanocomposite films with excellent surface insulation performance for space applications

The exploration of deep space significantly increases the probability of spacecraft failures due to surface electrostatic discharge, which imposes higher vacuum insulation protection requirements on polyimide (PI), the external insulation material of spacecrafts. To address this challenge, this study proposes using silane coupling agent KH550 for organic grafting treatment of Cr2O3nanoparticles, which are then used to dope and modify PI to enhance the vacuum surface insulation of PI films. The KH550 grafting improves the interface strength between the fillers and the matrix, allowing the fillers to be uniformly dispersed in the matrix. Compared to pure PI films, the prepared PI-Cr2O3@KH550 composite films exhibit significantly enhanced vacuum surface flashover voltage, improved surface/volume resistivity, and dielectric properties. The results demonstrate that PI composite films with 0.8% by mass of Cr2O3@KH550 show the most notable performance improvement, with the DC flashover voltage and impulse flashover voltage in vacuum increasing by 20.7% and 27.8%, respectively. The doping of chromium oxide nanoparticles introduces more deep traps into the PI films and reduce the surface resistivity. The higher deep trap density inhibits charge migration, thereby alleviating secondary electron emission and surface electric field distortion. Simultaneously, the lower surface resistivity facilitates dissipating surface charges and improves the surface insulation. These findings are of significant reference value for promoting the enhancement of aerospace insulation performance.

Boosting third-order optical nonlinearity in ITO/Au multilayer films via interfacial effects

We present the enhancement of third-order optical nonlinearity in indium tin oxide (ITO)/Au multilayer films via interfacial effects. The overall thickness of prepared ITO and Au layer was kept as 200 nm and 14 nm, respectively, and thus multilayers are 214 nm, i.e., for the sandwich structure ITO/Au/ITO, the thickness of ITO and Au is 100 nm and 14 nm, respectively, while the thickness of ITO and Au is 40 nm and 3.5 nm in the nine-layer films composed of five layers of ITO and four layers of Au. The measured nonlinear refractive index (n2) and absorption coefficient (β) of the multilayers rise as the number of layers increases. The maximum n2 and β in the nine-layer film are 2.6×10−14 m2/W and −3.7×10−8 m/W, which are 3.8 and 2.3 times larger than the values in the pure ITO film, respectively. Such enhancement of optical nonlinearity as the number of layers increases originates from the increase of carrier concentrations in multilayers due to contact of metals/semiconductors (interfacial effects), not following the traditional effective media theory and epsilon-near-zero effect. The results pave a way to modulate the optical nonlinearity in special metal-dielectric multilayers of interfacial effects and indicates the promising applications in nonlinear photonics.

Control of second-and third-order nonlinear optical properties of DCM and Znq2 composites fabricated by the physical vapor co-deposition process

In the present work, investigations on the second and third-order NLO properties of, 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) reddye co-doped bis(8-hydroxyquinoline) Zinc (Znq2) thin films with different concentrations were investigated. The samples have a thickness of 100 nm. They were prepared using the physical vapor deposition (PVD) method under a high vacuum. The morphological properties were studied by atomic force microscopy. The second-order nonlinear susceptibility χ(2) after applying the corona poling technique was estimated using the comparative model of Lee, while the third-order nonlinear susceptibility χ(3) was estimated using the comparative model of Kubodera and Kobayashi. The tested samples varied in terms of the concentration of DCM in the structure, which visibly influenced their nonlinear response. The pure DCM thin film showed a large value of the second and third-order nonlinear susceptibility, while pure Znq2 had only the second harmonic response with a low value. In this study, we have demonstrated that doping with DCM, even with small concentrations, has also strongly enhanced the non-linearity of Znq2. The obtained results show that such compositions can be a good alternative for optoelectronic applications.

Thin Ga-doped ZnO Film with Enhanced Dual Visible Lines Emission

Introduction: In this study, a simple and facile route was employed to prepare a highly transparent and luminescent ultra-thin gallium doped ZnO film (GZO). Methods: The thin GZO film has been deposited using the simultaneously ultrasonic vibration and sol-gel spin-spray coating technique. The structural and optical properties of pure and doped thin films were investigated by various methods, such as X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), scanning electron microscopy (SEM), UV-Vis, and PL spectroscopy. Results: XRD results indicated that both pure and doped ZnO films had a hexagonal wurtzite structure with (101) preferred orientation. XPS and EDX studies confirmed the incorporation and presence of Ga ions into the ZnO lattice structure. The doped sample showed nearly 90% of transparency, and a strong blue-green emission in the visible region. Conclusion: The obtained results proved that the prepared thin film could be a novel candidate for optoelectronic applications.