Self-supporting Films Research Articles

Elastic Fluorescent Protein-Based Down-Converting Optical Films for Flexible Display.

Protein-based material design provides great advantages to developing smart biomaterials with tunable structures and desired functions. They have been widely used in many biomedical applications including tissue engineering and drug delivery. However, protein-based materials are not yet widely used in optoelectronic materials despite their excellent optical and tunable mechanical properties. Here, we synthesized engineered fluorescent proteins (FPs) fused with elastic protein for the development of optoelectrical down-converting optical filters for flexible display materials. We synthesized sequence-specific FPs to tune blue, green, yellow, and red colors and fused them with elastic protein to tune mechanical properties. We fabricated flexible self-supporting film materials and characterized mechanical properties and down-converting optical properties. We also fabricated a hybrid light-emitting diode (LED) to down convert blue to desired green, red, and white colors. Furthermore, we constructed a flexible white LED using organic LED as a flexible substrate. Our modular synthesis approach of tunable bio-optoelectrical material approaches will be useful to design future biocompatible and flexible display materials and technologies.

Encapsulation of KTi2(PO4)3 nanoparticles in porous N-doped carbon nanofibers as a free-standing electrode for superior Na/K-storage performance

Herein, a self-supporting electrospinning film of porous N-doped carbon nanofibers impregnated with KTi2(PO4)3 nanoparticles (abbreviated as NF-KTP) is constructed. The free-standing NF-KTP exhibits excellent flexibility and is directly adopted as a binder-free anode for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). The introduction of conductive N-doped carbon matrix enables enhanced intrinsic electronic conductivity and fast ion diffusion kinetics, as well as the fabrication of porous nitrogen-doped interconnected carbon fibers impregnated with KTi2(PO4)3 nanoparticles can offer a short transport path of sodium/potassium ions and buffer the volume expansion during repetitive intercalation/deintercalation. Therefore, the NF-KTP electrode delivers an initial charge capacity of 116.8 mAh g−1 at 0.2 C, superb rate capability of 107.8 mAh g−1 at 50 C and impressive cycling stability with a capacity retention of 92.8 % for 1000 cycles at 5 C in SIBs. Even at 0 °C and 50 °C, it still retains marvelous rate performance with capacities of 99.8 and 106.3 mAh g−1 at 50 C, respectively. Meanwhile, as an anode material for PIBs, NF-KTP also displays good electrochemical performances, as reflected by its exceptional rate performance (99.3 mA h g−1 at 10 C) and superb cycling performance (with no capacity fading after 300 cycles at 5 C). These satisfactory electrochemical properties can be ascribed to the superiority of the stable 3D network formed by KTP nanofibers. Such a simple and effective strategy may provide a new vision for other materials applied in energy storage systems.

Comparative characteristics of products of processing of fusible copoly (urethane-imides) from the solutions and melts formed by them

Self-supporting films and thick-walled moldings (blades) were obtained from solutions and melts of multiblock (segmental) copoly(urethane-imides). The initial copoly(urethane-imides) were obtained on the basis of aliphatic polyesters: poly(propyleneglycol), poly(diethyleneglycoladipinate) and polycaprolactone, dianhydride of 1,3-bis(3’,4-dicarboxyphenoxy) benzene and aromatic diamines: 4,4’-bis-(4”-aminophenoxy)biphenyl and 1,4-bis(4’-aminophenoxy)diphenylsulfone. Samples of films and moldings were studied by IR spectroscopy, TGA, DSC and mechanical analysis under static and dynamic (DMA) experimental conditions. It is assumed that the diff erences in the properties of films and moldings are due to an increase in the proportion of aromatic blocks due to microdestruction of polymer chains and increased interfacial interactions of polyester and urethanimide microphases (blocks) in polymer systems during the processing of polymers from the melt by injection molding.

Kinetics-favorable heterojunctional CNTs@CuCo-LDH/BPQD electrode with boosted charge storage capability for supercapacitor

Component modulation and structure construction are the fundamental strategies in designing electrode materials for supercapacitors. Layered double hydroxide (LDH) is considered the promising electrode material, while with the drawback of low electron transmission efficiency and pulverization hinder. Herein, a novel kinetics-favorable heterojunctional self-supporting film electrode, composed of carbon nanotubes (CNTs), CuCo-LDH, and black phosphorus quantum dots (BPQD), is successfully prepared and directly utilized as electrodes in the supercapacitor. Highly conductive CNTs evenly and heavily entangled with CuCo-LDH hollow structures, resulting in robust mechanical property, enhanced electrical conductivity, and accelerated charge transfer during a redox reaction. Together with the surface decorated high-carrier-mobility BPQD, constructing heterojunction and acting as an electron donor to provide numerous active sites and facilitate energy storage behavior, a promoted pseudocapacitive performance was obtained and furtherly demonstrated by the density functional theory simulations based on the adsorption energies of OH–. The as-fabricated CNTs@CuCo-LDH/BPQD electrode presents a maximum capacitance of 1061.6 F g−1. The as-assembled hybrid supercapacitor device represents energy density up to 62.1 Wh kg−1 and remarkable cycling performance with 79.1% capacity retention after 10,000 cyclic tests. The prototype supercapacitor of this work shed light on the engineering of LDH-based materials for practical energy storage devices.

A Flexible and Robust Structural Color Film Obtained by Assembly of Surface-Modified Melanin Particles.

In this study, core–shell-hairy-type melanin particles surface modified with a polydopamine shell layer and a polymer brush hairy layer were fabricated and assembled to readily obtain bright structural color films. The hot pressing of freeze-dried samples of melanin particles decorated with a hydrophilic, low glass transition temperature polymer brush results in films that exhibit an angle-dependent structural color due to a highly periodic microstructure, with increased regularity in the arrangement of the particle array due to the fluidity of the particles. Flexible, self-supporting, and easy-to-cut and process structural color films are obtained, and their flexibility and robustness are demonstrated using compression tests. This method of obtaining highly visible structural color films using melanin particles as a single component will have a significant impact on practical materials and applications.

Synthesis of Large-Area MXenes with High Yields through Power-Focused Delamination Utilizing Vortex Kinetic Energy.

Evaluating the delamination process in the synthesis of MXenes (2D transition metal carbides and nitrides) is critical for their development and applications. However, the preparation of large defect‐free MXene flakes with high yields is challenging. Here, a power‐focused delamination (PFD) strategy is demonstrated that can enhance both the delamination efficiency and yield of large Ti3C2T x MXene nanosheets through repetitive precipitation and vortex shaking processes. Following this protocol, a colloidal concentration of 20.4 mg mL–1 of the Ti3C2T x MXene can be achieved after five PFD cycles, and the yield of the basal‐plane‐defect‐free Ti3C2T x nanosheets reaches 61.2%, which is 6.4‐fold higher than that obtained using the sonication–exfoliation method. Both nanometer‐thin devices and self‐supporting films exhibit excellent electrical conductivities (≈25 000 and 8260 S cm‐1 for a 1.8 nm thick monolayer and 11 µm thick film, respectively). Hydrodynamic simulations reveal that the PFD method can efficiently concentrate the shear stress on the surface of the unexfoliated material, leading to the exfoliation of the nanosheets. The PFD‐synthesized large MXene nanosheets exhibit superior electrical conductivities and electromagnetic shielding (shielding effectiveness per unit volume: 35 419 dB cm2 g–1). Therefore, the PFD strategy provides an efficient route for the preparation of high‐performance single‐layer MXene nanosheets with large areas and high yields.

Mussel-inspired sulfated nanocellulose-mediated conductive nanofiber for thermoelectric and humidity sensing multifunctional applications

The catechol groups of mussel-inspired polydopamine (PDA) act as the active sites to induce in-situ polymerization of 3,4-ethylenedioxythiophene (EDOT) on the surface of tunicate sulfated nanocellulose (TSN) to prepare PEDOT:PDA:TSN (PPTSN) conductive nanofiber with a core-sheath structure. The abundant negative sulfate groups on the surface of TSN endow PPTSN with outstanding dispersion stability. The flexible self-supporting PPTSN nanocomposite films formed by solution casting, inheriting the excellent mechanical properties of the TSN core and electrical conductivity of the PEDOT sheath, exhibit decent thermoelectric properties for thermoelectric material applications. Furthermore, based on the humidity responsiveness of PPTSN, the obtained nanocomposite films have great application prospects in constructing respiratory monitoring and non-contact sensors for sensing human humidity-related behaviors.

Milk protein-based active edible packaging for food applications: An eco-friendly approach

Whey and casein proteins, in particular, have shown considerable promise in replacing fossil-based plastics in a variety of food applications, such as for O2 susceptible foods, thereby, rendering milk proteins certainly one of the most quality-assured biopolymers in the packaging discipline. Properties like excellent gas barrier properties, proficiency to develop self-supporting films, adequate availability, and superb biodegradability have aroused great attention toward whey and other milk proteins in recent years. High thermal stability, non-toxicity, the ability to form strong inter cross-links, and micelle formation, all these attributes make it a suitable material for outstanding biodegradability. The unique structural and functional properties of milk proteins make them a suitable candidate for tailoring novel active package techniques for satisfying the needs of the food and nutraceutical industries. Milk proteins, especially whey proteins, serve as excellent carriers of various ingredients which are incorporated in films/coatings to strengthen barrier properties and enhance functional properties viz. antioxidant and antimicrobial. In this review, the latest techniques pertaining to the conceptualization of active package models/ systems using milk proteins have been discussed. Physical and other functional properties of milk protein-based active packaging systems are also reviewed. This review provides an overview of recent applications of milk protein-sourced active edible packages in the food packaging business.

Flexible thermoelectric device with excellent durability towards self-powered light intensity detection

Thermoelectric technology can generate thermoelectric electromotive force under the condition of temperature difference, which have unlimited prospects in the emerging fields of sensing, wearable electronic devices, self-powered arbitrary doors, electronic skin. These application scenarios also put forward higher requirements for thermoelectric devices, excellent flexibility and self-supporting characteristics. Herein, a novel flexible self-supported thermoelectric device based on carbon nanotubes (CNTs) was designed and constructed with simple laminated construction of electrical series and thermal parallel. CNTs/PEDOT:PSS and polyethylenimine (PEI)-doped CNTs/polyvinylidene fluoride (PVDF) flexible self-supported films were used as p- and n-type films respectively. The obtained flexible self-supported thermoelectric device can generate a voltage of 3.31 mV under temperature difference of 35 K. The excellent light absorption and photothermal conversion of CNTs, together with the thermoelectric characteristics of CNTs and PEDOT:PSS, enables its promising applications in self-powered light intensity detection. Furthermore, its excellent flexibility and self-supporting characteristics give it outstanding durability.

Heterogeneous Pd-PdO mesoporous film for ammonia electrosynthesis

Exploring cost-effective and highly active electrocatalysts is of great significance for sustainable electrochemical NH3 synthesis. Palladium (Pd)-based catalysts have been unanimously considered as one of the most efficient catalysts for the nitrogen reduction reaction (NRR). Herein, self-supported mesoporous Pd film with partial oxidation on Ni foam (mPd-PdO/NF) was synthesized through the micelle-assisted chemical replacement method coupled with air oxidation under 260 °C, and the mPd-PdO/NF electrocatalyst exhibited superior NRR performance with the maximum values of r NH3 (24.8 mg h−1 mgcat. −1) and FE (16.64%) were obtained at −0.1 V, relative to the single counterparts (mPd/NF and mPdO/NF). It is proposed that both metallic Pd and its oxide domains when co-existing with a phase boundary between them can facilitate nitrogen activation and hydrogenation, resulting in an enhanced NRR performance. This work provides an inspiring strategy for the rational design of highly active and durable metal–metal–oxide nanoarchitectonics for ammonia electrosynthesis.

Broadband photodetector based on vapor-deposited selenium self-supporting films

As a high-quality p-type semiconductor, Selenium (Se) has become an important potential candidate for photoelectric devices due to its high photoconductivity, non-linear optical response, and large piezoelectricity. However, the intrinsic Se has a wide bandgap (about 1.77 eV), so it is usually used for photodetection in the visible region. In this work, the Se self-supporting films have been successfully fabricated by an improved physical vapor deposition (PVD) method, and a metal-semiconductor-Metal (MSM) photodetector based on the Se self-supporting films has been designed for the first time. The photodetector shows broadband photoresponse from visible light to near-infrared (450–1550 nm), which is consistent with the experimental absorption spectrum of the obtained film. Besides, photodetection results indicate that the device exhibits a fast response speed (Tr = 4.5 ms, Td = 63.8 ms) with perfect responsivity (8.1 μA/W) and detectivity (1.3 × 105) under 3 V bias voltage and 450 nm (0.971 mW) light irradiation. The research of this paper will further enrich the application and development of traditional Se semiconductors in the field of optoelectronics.

A film electrode composed of micron-diamond embedded in phenolic resin derived amorphous carbon for electroanalysis of dopamine in the presence of uric acid

A self-supporting array-like film electrode composed of micron-diamond particles distributed in amorphous carbon matrix was synthesized by vacuum annealing the mixture of phenolic resin and micro-diamond for electroanalysis of dopamine in the presence of uric acid. • The D/AC electrode was prepared by vacuum annealing the PR and micro-diamond. • The AC matrix was divided by micron-diamond to realize array-like structure. • The D/AC exhibited low LOD for DA (0.238 μM, 0.334 μM in the presence of UA). • Excellent selectivity to DA on D/AC in the presence of UA (300 mV) was confirmed. Levels of dopamine (DA) in the human body is directly related to an individual’s health status. It is crucial to detect DA via economical and effective means, especially when it coexists with other molecules. A self-supporting array-like electrode composed of micron-diamond particles distributed in amorphous carbon (AC) matrix (D/AC) was synthesized by vacuum annealing the mixture of phenolic resin (PR) and micro-diamond. During the annealing process, the PR was converted to AC. The AC was divided into micron-level areas using micron-diamond particles to obtain an array-like electrode, which improved the response of electroanalysis signals. The D/AC exhibited a low limit of detection for DA (0.238 μM), which was attributed to the array-like structure. Moreover, outstanding selectivity towards DA on D/AC in the presence of uric acid was confirmed, and the evident peak potential differences (300 mV) facilitated detection of DA. The detection limit of DA on D/AC in the presence of uric acid was 0.334 μM. Accordingly, D/AC may be suitable as biosensor candidate due to its decent stability, reproducibility and selectivity.

Ru clusters anchored on Magnéli phase Ti4O7 nanofibers enables flexible and highly efficient Li–O2 batteries

Lithium–oxygen (Li–O2) batteries have attracted tremendous attention due to their high specific energy density. However, their sluggish conversion kinetics and detrimental parasitic reactions would deteriorate the lifespan of batteries. Herein, a combined density functional theory (DFT) calculation and experimental approach is carried out to design an efficient cathode electrocatalyst for Li–O2 batteries. A self-supporting film of Ru clusters anchored on Magnéli phase Ti4O7 enriched with oxygen vacancy (Ru/Ti4O7) is fabricated upon electrospinning and carbothermal reduction. In such a synergistic configuration of Ru/Ti4O7 hybrid film, the strong metal-support interaction (SMSI) between Ru and Ti4O7 can improve the charge transfer at the interface and enhance the adsorption energy of intermediates, accelerating the reaction kinetics of the formation/decomposition of Li2O2. Benefitting from this SMSI, the electrochemical stability of Ru/Ti4O7 over cycling is also enhanced. As a result, as-prepared Ru/Ti4O7 cathodes could realize excellent electrochemical performance, including high specific capacity (11000 mAh g–1), low discharge/charge polarization (0.36 V), long lifespan (> 100 cycles) and superior rate capability. Furthermore, a flexible Li–O2 pouch cell, constructed with as-fabricated Ru/Ti4O7 film cathode, lithium foil anode and GPE, can exert an impressive areal capacity of 5 mAh cm–2 with a low voltage gap of 0.82 V in ambient air. This work suggests that the activity of catalysts can be significantly enhanced with interfacial modification, offering an efficient approach for rational designing of electrocatalysts for use in Li–air batteries and beyond.

Strain Balanced Self‐Supporting Single‐Crystalline LiNbO3 Thin Films for Flexible Electronics (Adv. Electron. Mater. 5/2022)

Exfoliated Ultrathin Films In article number 2100986, a novel strain-balanced model of a sandwich structure is proposed by Hongyan Zhou, Shibin Zhang, Xin Ou, and co-workers to balance the residual strain in the exfoliated LiNbO3 ultrathin films, and consequently, the self-supporting single-crystalline LiNbO3 films with an intermediate layer of benzocyclobutene can be successfully fabricated by the strain compensation bonding method, which has great potential for flexible electronics.

Fabrication and characterization of self supporting 48Ti thin films

Fabrication of self-supporting 48Ti films of thickness ≈500μg/cm2 using 100 mg of the material by electron-beam evaporation technique in a high vacuum environment has been discussed. A simple and novel method of slowly evaporating the enriched material has been adopted in contrast to complex setup modifications utilized in earlier studies. Various techniques employed for successful fabrication of thin films have been discussed. The thickness measurements and characterizations of fabricated thin films have been carried out using advanced techniques viz., α-transmission method, Rutherford Backscattering Spectrometry (RBS), Energy Dispersive X-ray Spectrometry (EDS), Field Emission Scanning Electron Microscopy (FE-SEM), and Energy Dispersive X-ray Fluorescence (EDXRF). One of the fabricated targets has successfully been used in nuclear physics experiments.

Mo2C@C nanofibers film as durable self-supported electrode for efficient electrocatalytic hydrogen evolution

Self-supported electrocatalytic thin films consist 3D conducting network and well-embedded electrocatalysts, which endows the advantage in mass flow kinetics and durability for large-scale water splitting. Synthesis of such self-supported electrode still remains a big challenge due to the difficulty in the control over the 3D conducting network and the simultaneous growth of catalyst with well attachment on the conducting fibers. Herein, a self-supported Mo2C@carbon nanofibers (Mo2C@C NF) film has been successfully fabricated with outstanding electrocatalytic performance under optimized pyrolysis temperature and precursors mass ratio conditions. During the carbonation process, the Mo2C nanoparticles (∼16 nm) were simultaneously grown and well dispersed on the inter-connected carbon nanofibers, which formed a 3D conducting network. The as-formed 3D carbon network was strong enough to support direct electrocatalytic application without additional ink or supporting substrates. This particular electrode structure facilitated easy access to the active catalytic sites, electron transfer, and hydrogen diffusion, resulting in the high hydrogen evolution reaction activity. A low overpotential of 86 mV was needed to achieve 10 mA cm−2 current density with outstanding kinetics metric (Tafel 43 mV dec−1) in 1 M KOH. Additionally, the self-supported Mo2C@C NF film, a binder-free electrode, exhibited extraordinary stability of more than 340 h.

Self-Supporting Electrocatalyst Film Based on Self-Assembly of Heterogeneous Bottlebrush and Polyoxometalate for Efficient Hydrogen Evolution Reaction.

Developing efficient electrocatalysts to promote the hydrogen evolution reaction (HER) is essential for a green and sustainable future energy supply. For practical applications, it is a challenge to achieve the self-assembly of electrocatalyst from microscopic to macroscopic scales. Herein, a facile strategy is proposed to fabricate a self-supporting electrocatalyst film (CNT-g-PSSCo/PW12 ) for HER by electrostatic interaction-induced self-assembly of cobalt polystyrene sulfonate-grafted carbon nanotube heterogeneous bottlebrush (CNT-g-PSSCo) and polyoxometalate (PW12 ). Co2+ ions of CNT-g-PSSCo can function as junctions for interconnecting neighboring bottlebrushes to form the 3D nanonetwork structure and enable electrostatic capture of negatively charged PW12 nanodots. Moreover, CNT backbones can provide highly conductive pathways to CNT-g-PSSCo/PW12 . Such a self-assembled CNT-g-PSSCo/PW12 displays a low overpotential of 31mV at a current density of 10mA cm-2 and a small Tafel slope of 25mV dec-1 , showing high efficiency toward HER. Furthermore, CNT-g-PSSCo/PW12 with a stable self-supporting film morphology exhibits long-term electrocatalytic stability over 1000 CV cycles without noticeable overpotential change in acidic media. The findings may provide a new avenue for constructing self-assembled functional nanonetwork materials with well-orchestrated structural hierarchy for many applications in energy, environment, catalysis, medicine, and others.

Lignin-Based/Polypyrrole Carbon Nanofiber Electrode With Enhanced Electrochemical Properties by Electrospun Method.

Tailoring the structure and properties of lignin is an important step toward electrochemical applications. In this study, lignin/polypyrrole (PPy) composite electrode films with microporous and mesoporous structures were designed effectively by electrostatic spinning, carbonization, and in situ polymerization methods. The lignin can not only reduce the cost of carbon fiber but also increase the specific surface area of composite films due to the removal of carbonyl and phenolic functional groups of lignin during carbonization. Besides, the compact three-dimensional (3D) conductive network structures were constructed with PPy particles densely coated on the lignin nanofibers, which was helpful to improve the conductivity and fast electron transfer during the charging and discharging processes. The synthesized lignin carbon fibers/PPy anode materials had good electrochemical performance in 1 M H2SO4 electrolyte. The results showed that, at a current density of 1 A g−1, the lignin carbon nanofibers/PPy (LCNFs/PPy) had a larger specific capacitance of 213.7 F g−1 than carbon nanofibers (CNFs), lignin carbon nanofibers (LCNFs), and lignin/PPy fiber (LPAN/PPy). In addition, the specific surface area of LCNFs/PPy reached 872.60 m2 g−1 and the average pore size decreased to 2.50 nm after being coated by PPy. Therefore, the independent non-binder and self-supporting conductive film is expected to be a promising electrode material for supercapacitors with high performance.

Blue emission from silk fibroin-Yb3+/Tm3+:YAG films by up-conversion

Developing systems that can stop counterfeiting is crucial. In this sense, luminescent markers are a good strategy because the label is only visible under special conditions. In this scenario, the up-conversion emission mechanism is an example of cutting-edge knowledge, especially the blue emission, which requires at least three photons to occur. Here, we have prepared a new material based on silk fibroin and inorganic particles doped with Yb3+/Tm3+ ions and investigated the blue up-conversion process in it. This association of particles and silk fibroin allowed us to explore the exceptional properties of this protein allied with the multifunctionality of lanthanides: the resulting biodegradable, self-supported film emits in the blue region and can be applied as an anti-counterfeiting device, surface coating, or even an ink for 3D printers.

Synthesis of paramylon ester-graft-PLA copolymers and its two-step enzymatic degradation by proteinase K and β-1,3-glucanase

Paramylon ester-graft-poly(lactic acid) (PLA) copolymers were synthesized by the ring opening polymerization of l-lactide with paramylon acetate (PaAc) samples having an acetate degree of substitution (DS) from 0.5 to 2.2 (PaAc-g-PLA) or paramylon propionate (PaPr) samples with a propionate DS of 1.6 or 2.0 (PaPr-g-PLA). These copolymers exhibited thermoplasticity and some formed self-supporting melt-pressed films. Analyses of annealed films using differential scanning calorimetry showed that their thermal properties varied with the PLA DS. The enzymatic degradation behaviors of the neat paramylon as well as the PaAc and PaPr were investigated by treating these materials with β-1,3-glucanase followed by spectrometric analysis of the glucose levels in the buffer solutions, prior to the investigation of the copolymers. The data showed that 9 wt% glucose was obtained from the neat paramylon after 7 d and that the PaAc and PaPr were also degraded by β-1,3-glucanase. The concentration of liberated glucose was also found to decrease as the DS increased. Two-step enzymatic degradation tests were subsequently carried out with PaAc-g-PLA and PaPr-g-PLA specimens. In the first step, proteinase K was applied to degrade the PLA side-chains and high performance liquid chromatography (HPLC) was used to assess the release of lactic acid. Both HPLC and nuclear magnetic resonance (NMR) analyses established that the PLA side-chains of both the PaAc-g-PLA and PaPr-g-PLA specimens were successfully degraded. In the second step, β-1,3-glucanase was employed to decompose the remaining paramylon ester backbones. Monitoring the release of glucose showed that these backbones were successfully degraded in trials using the PaAc0.5-g-PLA and PaAc1.0-g-PLAs after 7 d These results confirmed that both copolymers could be broken down via this two-step enzymatic treatment, and that degradation by β-1,3-glucanase was dependent on the DS of the paramylon ester backbone. The results of this work show that PaAc1.0-g-PLA is a plastic material capable of thermal processing and is also completely biodegradable.