High gas barrier coating using non-toxic nanosheet dispersions for flexible food packaging film

Photothermal controlled antibacterial Ta4C3Tx-AgNPs/nanocellulose bioplastic food packaging

Uncontrolled antibacterial, insufficient barrier and low strength are the bottlenecks of food packaging applications. Herein, Ta4C3Tx nanosheet as a template was used to prepare Ta4C3Tx immobilized silver nanoparticles (Ta4C3Tx-AgNPs), which was compounded with nanocellulose to obtain high-strength and high barrier controllable bactericidal nanocellulose-based bioplastic packaging (CTa-Ag). The results indicated that due to the hydrogen bonding between nanocellulose and Ta4C3Tx, the bridging effect of QCS (quaternized chitosan) and the filling of Ta4C3Tx-AgNPs, the CTa-Ag had tightly stacked microstructure, which endowed them with excellent mechanical properties (4.0 GPa), ultra-low oxygen permeability (0.009 cm3/m2·d·atm) and stable photothermal conversion efficiency. Importantly, the packaging exhibits the ability to control the release of antibacterial active ingredients. Moreover, the synergistic effects of controllable release of nano active factors, photothermal and photocatalysis in CTa-Ag gave it long-lasting antibacterial properties. This study brings new insights into the design and manufacture of multifunctional, controllable and long-lasting antibacterial bioplastic food packaging.

Double-drying 3D lamellar-structured aerogel membrane for efficient oil-water separation and long-lasting antibacterial activity

Conventional oil-water separation membranes are difficult to establish a trade-off between membrane flux and separation efficiency, and often result in serious secondary contamination due to their fouling issue and non-degradability. Herein, a double drying strategy was introduced through a combination of oven-drying and freeze-drying to create a super-wettable and eco-friendly oil-water separating aerogel membrane (TMAdf). Due to the regular nacre-like structures developed in the drying process and the pores formed by freeze-drying, TMAdf aerogel membrane finally develops regularly arranged porous structures. In addition, the aerogel membrane possesses excellent underwater superoleophobicity with a contact angle above 168° and antifouling properties. TMAdf aerogel membrane can effectively separate different kinds of oil-water mixtures and highly emulsified oil-water dispersions under gravity alone, achieving exceptionally high flux (3693 L·m-2·h-1) and efficiency (99 %), while being recyclable. The aerogel membrane also displays stability and universality, making it effective in removing oil droplets from water in corrosive environments such as acids, salts and alkalis. Furthermore, TMAdf aerogel membrane shows long-lasting antibacterial properties (photothermal sterilization up to 6 times) and biodegradability (completely degraded after 50 days in soil). This study presents new ideas and insights for the fabrication of multifunctional membranes for oil-water separation.

Next-generation all-organic composites: A sustainable successor to organic-inorganic hybrid materials

This Review presents an overview of all-organic nanocomposites, a sustainable alternative to organic-inorganic hybrids. All-organic nanocomposites contain nanocellulose, nanochitin, and aramid nanofibers as highly rigid reinforcing fillers. They offer superior mechanical properties and lightweight characteristics suitable for diverse applications. The Review discusses various methods for preparing the organic nanofillers, including top-down and bottom-up approaches. It highlights in situ polymerization as the preferred method for incorporating these nanomaterials into polymer matrices to achieve homogeneous filler dispersion, a crucial factor for realizing desired performance. Furthermore, the Review explores several applications of all-organic nanocomposites in diverse fields including food packaging, performance-advantaged plastics, and electronic materials. Future research directions-developing sustainable production methods, expanding biomedical applications, and enhancing resistance against heat, chemicals, and radiation of all-organic nanocomposites to permit their use in extreme environments-are explored. This Review offers insights into the potential of all-organic nanocomposites to drive sustainable growth while meeting the demand for high-performance materials across various industries.

Control of polymers' amorphous-crystalline transition enables miniaturization and multifunctional integration for hydrogel bioelectronics

Soft bioelectronic devices exhibit motion-adaptive properties for neural interfaces to investigate complex neural circuits. Here, we develop a fabrication approach through the control of metamorphic polymers' amorphous-crystalline transition to miniaturize and integrate multiple components into hydrogel bioelectronics. We attain an about 80% diameter reduction in chemically cross-linked polyvinyl alcohol hydrogel fibers in a fully hydrated state. This strategy allows regulation of hydrogel properties, including refractive index (1.37-1.40 at 480 nm), light transmission (>96%), stretchability (139-169%), bending stiffness (4.6 ± 1.4 N/m), and elastic modulus (2.8-9.3 MPa). To exploit the applications, we apply step-index hydrogel optical probes in the mouse ventral tegmental area, coupled with fiber photometry recordings and social behavioral assays. Additionally, we fabricate carbon nanotubes-PVA hydrogel microelectrodes by incorporating conductive nanomaterials in hydrogel for spontaneous neural activities recording. We enable simultaneous optogenetic stimulation and electrophysiological recordings of light-triggered neural activities in Channelrhodopsin-2 transgenic mice.

Recent Advancements in Ascribing Several Platinum Free Electrocatalysts Pertinent to Hydrogen Evolution from Water Reduction

The advancement of a sustainable and scalable catalyst for hydrogen production is crucial for the future of the hydrogen economy. Electrochemical water splitting stands out as a promising pathway for sustainable hydrogen production. However, the development of Pt-free electrocatalysts that match the energy efficiency of Pt while remaining economical poses a significant challenge. This review addresses this challenge by highlighting latest breakthroughs in Pt-free catalysts for the hydrogen evolution reaction (HER). Specifically, we delve into the catalytic performance of various transition metal phosphides, metal carbides, metal sulphides, and metal nitrides toward HER. Our discussion emphasizes strategies for enhancing catalytic performance and explores the relationship between structural composition and the performance of different electrocatalysts. Through this comprehensive review, we aim to provide insights into the ongoing efforts to overcome barriers to scalable hydrogen production and pave the way for a sustainable hydrogen economy.

Optimising the acid-base ratio of Mg-Al layered double oxides to enhance CO2 capture performance: the critical role of calcination conditions

The effect of calcination conditions (ramp rate, calcination temperature and time) on the formation of Mg2Al layered double oxides (Mg2Al LDOs) as well as their CO2 capture performance, has been systematically investigated. This study explores novel insights into the intricate relationship between these calcination conditions and the resulting surface characteristics, which play a vital role in CO2 capture efficiency. Notably, it is revealed that a rapid ramp rate (100 °C min-1) significantly increases surface area and hydroxyl concentration, leading to a 69% increase in CO2 capture efficiency compared to slower ramp rate. Conversely, short calcination times (1 h) and fast ramp rates (100 °C min-1) are observed to compromise CO2 adsorption due to the presence of dehydrated LDHs. A critical acid : base ratio of 0.37, achieved from a fast ramp rate (100 °C min-1) at 400 °C for 2 h, was found as a key threshold for optimising surface properties, effectively balancing favourable hydroxyl and less favourable strong acid sites, thereby maximizing CO2 capture performance.

Hybrid organic-inorganic coating with enhanced oxygen- and UV-barrier performance: Polyelectrolyte complex based on sodium alginate, poly (vinyl alcohol), and reconstructed layered double hydroxide

Organic-inorganic hybrid materials with high oxygen- and UV-barrier properties were developed using a polyelectrolyte complex comprising sodium alginate (SA), poly (vinyl alcohol) (PVA), and reconstructed layered double hydroxide (RLDH). These materials were applied to poly (ethylene terephthalate) (PET) as a barrier coating layer at a harsh drying temperature of 120 °C, similar to environments for the industrial coating process. The RLDH nanoplatelets within the coating matrix restricted the polymer chain mobility, elevating the glass transition temperature to 105.222-159.114 °C. Below RLDH 0.2 %, the apparent coating density significantly increased to 0.93-0.94 g/cm3. The embedded RLDH gave a tortuosity within the matrix, as evidenced by an intensified (003) diffraction peak in the XRD analysis. These structural alterations contributed to high oxygen- and UV-barrier performance. Notably, the PET/SA1.0PVA0.5RLDH0.2 film exhibited an extremely low oxygen transmission rate of <0.005 cm3/m2·day, with effectively blocking UV-A (62.41 %), -B (92.45 %), and -C light (100 %). Moreover, the susceptibility of the coated film to water vapor was mitigated by laminating cast polypropylene, achieving a water vapor transmission rate of 1.17 g/m2·day. Overall, the packaging materials with advanced oxygen-, water vapor-, and UV-barrier properties show great potential for practical applications in various sectors, including food packaging and medical/electrical devices.

Alginate based films integrated with nitrogen-functionalized carbon dots and layered clay for active food packaging applications

The applications of alginate derived from seaweed polysaccharide in food packaging are restricted due to their inherent deficient antibacterial, antioxidant and UV barrier properties. In this study, nitrogen-functionalized carbon dots (NCDs) with active functions (0.5-3 %) and layered clay (1 %) with barrier property were introduced to construct alginate based active films via solution casting method. The results showed that the synthesized spherical NCDs had a particle size of 2-3 nm, and the internal structure of NCDs was similar to graphene, with a large number of active groups (-NH2, -OH, etc.) on the surface. Infrared analysis revealed that NCDs could form strong hydrogen bonds with alginate matrix, which slowed down the deterioration of mechanical properties and reduced the surface wettability. With the addition of NCDs, active functions and surface hydrophobicity of the active films were enhanced significantly (P < 0.05). When the amount of NCDs reached 3 %, UV barrier, antioxidant and antibacterial properties of the active films were increased by 50.0 %, 61.1 % and 70.1 %, respectively. The addition of NCDs could enhance the anti-browning ability of alginate based coatings and extend the shelf life of banana significantly. Therefore, a suitable amount of NCDs (1-2 %) and layered clay (1 %) can synergistically improve comprehensive performance of alginate based films and promote their food packaging application used as active films/inner coatings.

Intrabasal Plane Defect Formation in NiFe Layered Double Hydroxides Enabling Efficient Electrochemical Water Oxidation

Defect engineering has proven to be one of the most effective approaches for the design of high-performance electrocatalysts. Current methods to create defects typically follow a top-down strategy, cutting down the pristine materials into fragmented pieces with surface defects yet also heavily destroying the framework of materials that imposes restrictions on the further improvements in catalytic activity. Herein, we describe a bottom-up strategy to prepare free-standing NiFe layered double hydroxide (LDH) nanoplatelets with abundant internal defects by controlling their growth behavior in acidic conditions. Our best-performing nanoplatelets exhibited the lowest overpotential of 241 mV and the lowest Tafel slope of 43 mV/dec for the oxygen evolution reaction (OER) process, superior to the pristine LDHs and other reference cation-defective LDHs obtained by traditional etching methods. Using both material characterization and density functional theory (DFT) simulation has enabled us to develop relationships between the structure and electrochemical properties of these catalysts, suggesting that the enhanced electrocatalytic activity of nanoplatelets mainly results from their defect-abundant structure and stable layered framework with enhanced exposure of the (001) surface.

Comprehensive Analysis of the Chemical and Structural Transformations of Mg-Al-CO3 Layered Double Hydroxides with Different Mg/Al Ratios at Elevated Temperatures

Mg-Al layered double hydroxides (LDHs) with CO32- interlayer anions are promising CO2 adsorbents. Here, we analyzed the quantitative gas evolution behaviors of Mg-Al LDH particles with different Mg/Al ratios during the multistep chemical/structural transformations at elevated temperatures. The Mg/Al molar ratio strongly affects the behavior: the transformation changes from two apparent steps to three steps depending on the Mg/Al ratio. The transformation occurs in essentially the same way as that observed for large Mg-Al LDH crystals: (1) release of the interlayer water, (2) partial dehydroxylation of the hydroxyl layers followed by coordination of carbonate ions to the metals, and (3) collapse of the layered structure. We provide a molecular/atomic level picture of the structure in each step of the transformation by first-principles density functional theory (DFT) calculation. The structurally optimized model and reexamination of experimental data showed that step (1) results in a large decrease in the interlayer distance of the LDH from ∼7.6 to ∼6.7 Å (a decrease of ∼0.9 Å) and the possible explanation is the waving of the metal hydroxide layers. This study provides a comprehensive understanding of the structural changes of LDHs with various Mg/Al ratios to resolve the various interpretations in the literature.

Bottom-up Synthesis of Nanosheets at Various Interfaces

Nanostructured materials with high aspect ratios have been widely studied for their unique properties. In particular, nanosheets have safety, dispersibility, and nanosized effects, and nanosheets with exceptionally small thicknesses exhibit unique properties. For non-exfoliable materials, the bottom-up nanosheet growth using various interfaces as templates have been investigated. This review article presents the synthesis of nanosheets at the interfaces and layered structure; it explains the features of each interface type, its advantages, and its uniqueness. The interfaces work as templates for nanosheet synthesis. We can easily use the liquid-liquid and gas-liquid interfaces as the templates; however, the thickness of nanosheets usually becomes thick because it allows materials to grow in thickness. The solid-gas and solid-liquid interfaces can prevent nanosheets from growing in thickness. However, the removal of template solids is required after the synthesis. The layered structures of various materials provide two-dimensional reaction fields between the layers. These methods have high versatility, and the nanosheets synthesized by these methods are thin. Finally, this review examines the key challenges and opportunities associated with scalable nanosheet synthesis methods for industrial production.

Atomization-Induced High Intrinsic Activity of a Biocompatible MgAl-LDH Supported Ru Single-Atom Nanozyme for Efficient Radicals Scavenging

Developing efficient nanozymes to mimic natural enzymes for scavenging reactive radicals remains a significant challenge owing to the insufficient activity of conventional nanozymes. Herein, we report a novel Ru single-atom nanozyme (SAE), featuring atomically dispersed Ru atoms on a biocompatible MgAl-layered double hydroxide (Ru1 /LDH). The prepared Ru1 /LDH SAE shows high intrinsic peroxidase (POD)-like catalytic activity, which outperforms the Ru nanoclusters (NCs) nanozyme by a factor of 20 and surpasses most SAEs. The density functional theory calculations reveal that the high intrinsic POD-like activity of Ru1 /LDH can be attributed to a heterolytic path of H2 O2 dissociation on the single Ru sites, which requires lower free energy (0.43 eV) compared to the homolytic path dissociation on Ru NC (0.63 eV). In addition, the Ru1 /LDH SAE shows excellent multiple free radicals scavenging ability, including superoxide anion radical (O2 ⋅- ), hydroxyl radical (⋅OH), nitric oxide radical (NO⋅) and 2, 2-diphenyl-1-picrylhydrazyl radical (DPPH⋅). Given the advantages of Ru1 /LDH with high enzymatic activities, biosafety, and ease to scale up, it paves the way for exploring SAEs in the practical biological immunity system.

Nacre-inspired biodegradable nanocellulose/MXene/AgNPs films with high strength and superior gas barrier properties

Super strength and high barrier properties are the bottleneck of the application of cellulose film materials. Herein, it is reported a flexible gas barrier film with nacre-like layered structure, in which 1D TEMPO-oxidized nanocellulose (TNF) and 2D MXene self-assembled to form an interwoven stack structure with 0D AgNPs filling the void space. The strong interaction and dense structure endowed TNF/MX/AgNPs film with mechanical properties far superior to PE films and acid-base stability. Importantly, the film presented ultra-low oxygen permeability confirmed by molecular dynamics simulations and better barrier properties to volatile organic gases than PE films. It is here considered the tortuous path diffusion mechanism of the composite film responsible for the enhanced gas barrier performance. The TNF/MX/AgNPs film also possessed antibacterial properties, biocompatibility and degradability (completely degraded after 150 days in soil). Collectively, the TNF/MX/AgNPs film brings innovative insights into the design and fabrication of high-performance materials.

Surface modification of two-dimensional layered double hydroxide nanoparticles with biopolymers for biomedical applications

Layered double hydroxides (LDHs) are appealing nanomaterials for (bio)medical applications and their potential is threefold. One can gain advantage of the structure of LDH frame (i.e., layered morphology), anion exchanging property towards drugs with acidic character and tendency for facile surface modification with biopolymers. This review focuses on the third aspect, as it is necessary to evaluate the advantages of polymer adsorption on LDH surfaces. Beside the short discussion on fundamental and structural features of LDHs, LDH-biopolymer interactions will be classified in terms of the effect on the colloidal stability of the dispersions. Thereafter, an overview on the biocompatibility and biomedical applications of LDH-biopolymer composite materials will be given. Finally, the advances made in the field will be summarized and future research directions will be suggested.

Advances in Polyethylene Terephthalate Beverage Bottle Optimization: A Mini Review

Compared with other materials, polyethylene terephthalate (PET) has high transparency, excellent physical and mechanical properties in a wide temperature range and good hygiene and safety, so it is widely used in the packaging industry, especially in the packaging of beverages and foods. The optimization of PET bottles is mainly reflected in three aspects: material optimization, structure optimization and process optimization, among which there is much research on material optimization and process optimization, but there is no complete overview on structure optimization. A summary of structural optimization is necessary. Aiming at structural optimization, the finite element method is a useful supplement to the beverage packaging industry. By combining the computer-aided design technology and using finite element software for finite element simulation, researchers can replace the experimental test in the pre-research design stage, predict the effect and save cost. This review summarizes the development of PET bottles for beverage packaging, summarizes various optimization methods for preventing stress cracking in beverage packaging, and especially focuses on comparing and evaluating the effects of several optimization methods for packaging structure. Finally, the future development of all kinds of optimization based on structural optimization in the field of beverage packaging is comprehensively discussed, including personalized design, the combination of various methods and the introduction of actual impact factor calculation.

Layered double hydroxide-based nanomaterials for biomedical applications

Against the backdrop of increased public health awareness, inorganic nanomaterials have been widely explored as promising nanoagents for various kinds of biomedical applications. Layered double hydroxides (LDHs), with versatile physicochemical advantages including excellent biocompatibility, pH-sensitive biodegradability, highly tunable chemical composition and structure, and ease of composite formation with other materials, have shown great promise in biomedical applications. In this review, we comprehensively summarize the recent advances in LDH-based nanomaterials for biomedical applications. Firstly, the material categories and advantages of LDH-based nanomaterials are discussed. The preparation and surface modification of LDH-based nanomaterials, including pristine LDHs, LDH-based nanocomposites and LDH-derived nanomaterials, are then described. Thereafter, we systematically describe the great potential of LDHs in biomedical applications including drug/gene delivery, bioimaging diagnosis, cancer therapy, biosensing, tissue engineering, and anti-bacteria. Finally, on the basis of the current state of the art, we conclude with insights on the remaining challenges and future prospects in this rapidly emerging field.

Phonon Symphony of Stacked Multilayers and Weak Bonds Lowers Lattice Thermal Conductivity

Controlling lattice vibrations to obtain intrinsic low thermal conductivity play a critical role in thermal management of electronic and photonic devices, energy converters, and thermal insulation, which necessitates exploring new compounds and a thorough understanding of their chemical structure, bonding, and lattice dynamics. Herein, a new chalcogenide, Ga₆ Cr₅ Se₁₆ , shows intrinsic low lattice thermal conductivity κ_lat , which crystallizes in the monoclinic phase (C2/m) with the stacked inverse GaSe₄ layers (g'), close-packed Cr³⁺ Se₆ layers (c), GaSe₄ layers (g) and loosely-stacked Cr²⁺ Se₆ layers (c') along the c-axis. In this structure, a wide variety of chemical bonding is arranged in each layer, such as covalent Ga-Se, covalent Cr³⁺ -Se, and weaker Cr²⁺ -Se bonding, which endow it with a large phonon symphony by strong coupling of soft acoustic and low-lying optical phonons. As a result, Ga₆ Cr₅ Se₁₆ realizes an intrinsic low κ_lat of 0.79 W m^{- 1}  K^{- 1} at 323 K, which is almost four times, or twice lower than that of Cr₃ Se₄ (2.95 W m^{- 1}  K^{- 1} ), or Cr₂ Se₃ (1.56 W m^{- 1}  K^{- 1} ), Ga₂ Se₃ (1.36 W m^{- 1} K^{- 1} ) at 323 K, respectively. These insights will offer comprehensive understanding of the phonon propagation in complex layered chalcogenides, and also shed useful light on future design of low-κ_lat solids.

Two-Dimensional Ultra-Thin Nanosheets with Extraordinarily High Drug Loading and Long Blood Circulation for Cancer Therapy

Nanoparticle drug delivery is largely restricted by the low drug loading capacity of nanoparticle carriers. To address this critical challenge and maximize the potential of nanoparticle drug delivery, a 2D ultra-thin layered double hydroxide (LDH) nanosheet with exceptionally high drug loading, excellent colloidal stability, and prolonged blood circulation for cancer treatment is constructed. The nanosheet is synthesized via a biocompatible polymer-assisted bottom-up method and exhibits an ultra-thin 2D sheet-like structure that enables a considerable amount of cargo anchoring sites available for drug loading, leading to an extraordinary 734% (doxorubicin/nanoparticle mass ratio) drug loading capacity. Doxorubicin delivered by the nanosheet remains stable on the nanosheet carrier under the physiological pH condition, while showing sustained release in the tumor microenvironment and the intracellular environment, thus demonstrating on-demand drug release as a result of pH-responsive biodegradation of nanosheets. Using in vitro and in vivo 4T1 breast cancer models, the nanosheet-based ultra-high drug-loading system demonstrates even enhanced therapeutic performance compared to the multilayered LDH-based high drug-loading system, in terms of increased cellular uptake efficiency, prolonged blood circulation, superior therapeutic effect, and reduced systemic toxicity.

Enhancement of Gas Barrier Properties and Durability of Poly(butylene succinate-co-butylene adipate)-Based Nanocomposites for Food Packaging Applications

Poly(butylene succinate-co-butylene adipate) (PBSA)-based materials are receiving growing attention in the packaging industry for their promising biodegradability. However, poor gas barrier properties and low durability of biodegradable polymers, such as PBSA, have limited their wide-spread use in food packaging applications. Here we report a scalable solution to improve gas barrier properties and stabilize PBSA against photo-aging, with minimal modifications to the biodegradable polymer backbone by using a commercially available and biocompatible layered double hydroxide (LDH) filler. We investigate and compare the mechanical, gas barrier, and photoaging properties of PBSA and PBSA-LDH nanocomposite films produced on a pilot scale. An increase in rigidity in the nanocomposite was observed upon addition of LDH fillers to neat PBSA, which direct the application of neat PBSA and PBSA-LDH nanocomposite to different food packaging applications. The addition of LDH fillers into neat PBSA improves the oxygen and water vapour barriers for the PBSA based nanocomposites, which increases the attractiveness of PBSA material in food packaging applications. Through changes in the viscoelastic behaviour, we observe an improved photo-durability of photoaged PBSA-LDH nanocomposites compared to neat PBSA. It is clear from our studies that the presence of LDH enhances the lifetime durability and modulates the photodegradation rate of the elaborated biocomposites.

Gas permeation and microstructure of reduced graphene oxide/polyethyleneimine multilayer films created via recast and layer-by-layer deposition processes

Gas barrier property and microstructure of reduced graphene oxide/polyethyleneimine multilayer films created via recast and layer-by-layer deposition processes.

Controlled Release of Molecular Intercalants from Two-Dimensional Nanosheet Films

Solution co-deposition of two-dimensional (2D) nanosheets with chemical solutes yields nanosheet-molecular heterostructures. A feature of these macroscopic layered hybrids is their ability to release the intercalated molecular agent to express chemical functionality on their surfaces or in their near surroundings. Systematic design methods are needed to control this molecular release to match the demand for rate and lifetime in specific applications. We hypothesize that release kinetics are controlled by transport processes within the layered solids, which primarily involve confined molecular diffusion through nanochannels formed by intersheet van der Waals gaps. Here a variety of graphene oxide (GO)/molecular hybrids are fabricated and subject to transient experiments to characterize release kinetics, locations, and mechanisms. The measured release rate profiles can be successfully described by a numerical model of internal transport processes, and the results used to extract effective Z-directional diffusion coefficients for various film types. The diffusion coefficients are found to be 8 orders of magnitude lower than those in free solution due to nanochannel confinement and serpentine path effects, and this retardation underlies the ability of 2D materials to control and extend release over useful time scales. In-plane texturing of the heterostructured films by compressive wrinkling or crumpling is shown to be a useful design tool to control the release rate for a given film type and molecular intercalant. The potential of this approach is demonstrated through case studies on the controlled release of chemical virucidal agents.

Aged layered double hydroxide nanosheet-polyvinyl alcohol dispersions for enhanced gas barrier coating performance

Whilst applying a coating layer to a polymer film is a routine approach to enhance the gas barrier properties of the film, it is counter-intuitive to consider that the gas barrier performance of the film would improve by ageing the coating dispersion for weeks before application. Herein, we report that the oxygen barrier performance of a 12 μm PET film coated with a dispersion of inorganic nanosheets in polyvinyl alcohol can be significantly enhanced by ageing this coating dispersion for up to 8 weeks before application. We found up to a 37-fold decrease in the oxygen transmission rate (OTR) of the PET coated film using aged dispersions of [Mg_0.66Al_0.33(OH)₂](NO₃)_0.33 layered double hydroxide nanosheets (Mg₂Al-LDH NS) in polyvinyl alcohol (PVA) compared to the film coated with an equivalent freshly prepared LDH/PVA dispersion. A limiting OTR value of 0.31 cc m^-2 day^-1 was achieved using the PET film coated with a 3 week aged LDH NS/PVA dispersion. X-ray diffraction experiments show that the degree of in plane alignment of LDH NS on the PET film surface increased significantly from 70.6 ± 0.6 to 86.7 ± 0.6 (%) (100% represents complete alignment of LDH NS platelets on the film surface) for the 4 week aged dispersion compared to the freshly prepared layer. We postulate that when the Mg₂Al-LDH NS are aged in PVA the coiled PVA aggregates start to unwrap and attach onto the Mg₂Al-LDH NS through hydrogen bonding and eventually form a hydrogen bonded ordered network that facilitates the alignment of nanosheet dispersions during the coating process. Our results suggest that the ageing of inorganic nanosheet dispersions in PVA or other potential hydrogen bonding adhesive systems could be a general approach to improve the alignment of the nanosheets on the polymer film surface once applied and thus improve their performance characteristics for barrier coating applications.

The current knowledge concerning solid cancer and therapy

Solid cancers comprise a large number of new cases and deaths from cancer each year globally. There are a number of strategies for addressing tumors raised from solid organs including surgery, chemotherapy, radiotherapy, targeted therapy, immunotherapy, combinational therapy, and stem cell and extracellular vesicle (EV) therapy. Surgery, radiotherapy, and chemotherapy are the dominant cures, but are not always effective, in which even in a localized tumor there is a possibility of tumor relapse after surgical resection. Over half of the cancer patients will receive radiotherapy as a part of their therapeutic schedule. Radiotherapy can cause an abscopal response for boosting the activity of the immune system outside the local field of radiation, but it may also cause an unwanted bystander effect, predisposing nonradiated cells into carcinogenesis. In the context of immunotherapy, immune checkpoint inhibition is known as the standard-of-care, but the major concern is in regard with cold cancers that show low responses to such therapy. Stem-cell therapy can be used to send prodrugs toward the tumor area; this strategy, however, has its own predicaments, such as unwanted attraction toward the other sites including healthy tissues and its instability. A substitute to such therapy and quite a novel strategy is to use EVs, by virtue of their stability and potential to cross biological barriers and long-term storage of contents. Combination therapy is the current focus. Despite advances in the field, there are still unmet concerns in the area of effective cancer therapy, raising challenges and opportunities for future investigations.

Ni2Mn-layered double oxide electrodes in organic electrolyte based supercapacitors

The development of future mobility (e.g. electric vehicles) requires supercapacitors with high voltage and high energy density. Conventional active carbon-based supercapacitors have almost reached their limit of energy density which is still far below the desired performance. Advanced materials, particularly metal hydroxides/oxides with tailored structure are promising supercapacitor electrodes to push the limit of energy density. To date, research has largely focused on evaluation of these materials in aqueous electrolyte, while this may enable high specific capacitance, it results in low working voltage window and poor cycle stability. Herein, we report the development of Ni₂Mn-layered double oxides (Ni₂Mn-LDOs) as mixed metal oxide-based supercapacitor electrodes for use in an organic electrolyte. Ni₂Mn-LDO obtained by calcination of [Ni_0.66Mn_0.33(OH)₂](CO₃)_0.175·nH₂O at 400 °C produced the best performing Ni₂Mn-LDOs with high working voltage of 2.5 V and a specific capacitance of 44 F g⁻¹ (at 1 A g⁻¹). We believe the performance of the Ni₂Mn-LDOs is related to its unique porous structure, high surface area and the homogeneous mixed metal oxide network. Ni₂Mn-LDO outperforms both the single metal oxides (NiO, MnO₂) and the equivalent physical mixture of the two oxides. We propose this performance boost arises from synergy between NiO and MnO_x due to a more effective homogeneous network of NiO/MnO_x domains in the Ni₂Mn-LDO. This work clearly shows the advantage of an LDO over the single component metal oxides as well as the physical mixture of mixed metal oxides and highlights the possibilities of development of further mixed metal oxides-based supercapacitors in organic electrolyte using LDH precursors.

Ni₂Mn-layered double oxide (LDO) electrode not only expands the working voltage and enhances the specific capacitance of layered double hydroxide (LDH) in the organic electrolyte but also outperforms NiO, MnO₂ and their physical mixture.

Cephalopods-Inspired Rapid Self-Healing Nanoclay Composite Coatings with Oxygen Barrier and Super-Bubble-Phobic Properties

Polymeric coatings with oxygen barrier properties are an important technology in food packaging that can extend the shelf life of food products and reduce waste. Although a typical technology in practical use is the deposition of metal or inorganic materials between multilayer films to reduce the oxygen transmission rate, once the film is damaged, oxygen permeates through the damaged area, damaging the packaged food. In addition, nanobrick wall structures consisting of nanoplatelet bricks have the potential to replace barrier films made of inorganic materials; however, they similarly lack repair performance or have slow repair speed despite having repair performance. Inspired by the rapid self-repair mechanism of cephalopods, the study develops a nanoclay-containing coating that can rapidly repair surface damage via water within 10 s. By introducing CaCl₂-derived counterions and montmorillonite for nanobrick wall structures into polyelectrolyte multilayers stacked by layer-by-layer self-assembly, the noncovalent polymer network is increased, resulting in mimicking a strong cephalopod-derived β-sheet structure and noncovalent intermolecular interactions derived from cephalopods. The high water retention at the surface showed super-bubble-phobicity in water and inhibited gas permeation. The oxygen permeability of the coatings with more than a certain amount of montmorillonite was less than 1/100 of that of bare polyethylene. The ultrafast self-healing gas barrier coating has the potential to be used not only for food products but also for electronics and pharmaceutical packaging and gas separation applications. The key technology developed in this study provides novel insights into the construction of self-healing membranes made of composite materials and will contribute to the formation of a sustainable society.

Bioinspired Oil-Infused Slippery Surfaces with Water and Ion Barrier Properties

Encapsulation materials play an important role in many applications including wearable electronics, medical devices, underwater robotics, marine skin tagging system, food packaging, and energy conversation and storage devices. To date, all the encapsulation materials, including polymer layers and inorganic materials, are solid materials. These solid materials suffer from limited barrier lifetimes due to pinholes, cracks, and nanopores or from complicated fabrication processes and limited stretchability for interfacing with complex 3D surfaces. This paper reports a solution to this material challenge by demonstrating bioinspired oil-infused slippery surfaces with excellent waterproof property for the first time. A water vapor transmission test shows that locking a thin layer of oil on the silicone elastomer improves the water vapor barrier performance by three orders of magnitude. Accelerated lifetime tests suggest robust water barrier characteristics that approach 226 days at 37 °C even under severe mechanical damage. A combination of temperature- and thickness-dependent experimental measurements and reaction-diffusion modeling reveals the key waterproof property. In addition to serving as a barrier to water, the oil-infused surface demonstrates an attractive ion barrier property. All these exceptional properties suggest the potential applications of slippery surfaces as encapsulation materials for medical devices, underwater electronics, and many others.

Biorenewable, transparent, and oxygen/moisture barrier nanocellulose/nanochitin-based coating on polypropylene for food packaging applications

Aluminum-coated polypropylene films are commonly used in food packaging because aluminum is a great gas barrier. However, recycling these films is not economically feasible. In addition, their end-of-life incineration generates harmful alumina-based particulate matter. In this study, coating layers with excellent gas-barrier properties are assembled on polypropylene films through layer-by-layer (LbL) deposition of biorenewable nanocellulose and nanochitin. The coating layers significantly reduce the transmission of oxygen and water vapors, two unfavorable gases for food packaging, through polypropylene films. The oxygen transmission rate of a 60 μm-thick, 20 LbL-coated polypropylene film decreases by approximately a hundredfold, from 1118 to 13.10 cc m^-2 day^-1 owing to the high crystallinity of nanocellulose and nanochitin. Its water vapor transmission rate slightly reduces from 2.43 to 2.13 g m^-2 day^-1. Furthermore, the coated film is highly transparent, unfavorable to bacterial adhesion and thermally recyclable, thus promising for advanced food packaging applications.

Single-Step Application of Polyelectrolyte Complex Films as Oxygen Barrier Coatings

Polyelectrolyte complex (PEC) films such as polyelectrolyte multilayers have demonstrated excellent oxygen barrier properties, but unfortunately, the established layer-by-layer approaches are laborious and difficult to scale up. Here, we demonstrate a novel single-step approach to produce a PEC film, based on the use of a volatile base. Ammonia was used to adjust the pH of poly(acrylic acid) (PAA) so that direct complexation was avoided when it was mixed with polyethylenimine (PEI). Different charge ratios of homogeneous PEI/PAA solutions were successfully prepared and phase diagrams varying the concentration of ammonia or polyelectrolyte were made to study the phase behavior of PEI, PAA, and ammonia in water. Transparent ∼1 μm thick films were successfully deposited on biaxially orientated polypropylene (BOPP) sheets using a Meyer rod. After casting the films, the decrease in pH, caused by the evaporation of ammonia, triggered the complexation during drying. The oxygen permeation properties of films with different ratios and single polyelectrolytes were tested. All films displayed excellent oxygen barrier properties, with an oxygen permeation below 4 cm³·m^-2·day^-1·atm^-1 (<0.002 barrer) at the optimum ratio of 2:1 PEI/PAA. This ammonia evaporation-induced complexation approach creates a new pathway to prepare PEC films in one simple step while allowing the possibility of recycling.

Preparation of Well-Exfoliated Poly(ethylene-co-vinyl acetate)/α-Zirconium Phosphate Nanocomposites

Poly(ethylene-co-vinyl acetate) (PEVAc) nanocomposites containing exfoliated α-zirconium phosphate (ZrP) have been prepared using a simple solution mixing method to improve their barrier and mechanical properties. ZrP was pre-exfoliated with a surfactant, followed by additional targeted surface functionalization and surfactant exchange to allow for hydrogen bonding of ZrP with the acetate functionality on PEVAc and to improve ZrP surface hydrophobicity. The solvent is found to play an important role in stabilizing ZrP exfoliation in the presence of PEVAc to retain full exfoliation and homogeneous dispersion upon the removal of the solvent. The PEVAc/ZrP nanocomposite exhibits greatly improved oxygen barrier, melt strength, and mechanical properties. The usefulness of the present study for the preparation of olefinic polymer nanocomposites is discussed.

Surface modification of aqueous miscible organic layered double hydroxides (AMO-LDHs)

Silane modification of layered double hydroxides (LDHs) plays an important role in controlling the surface hydrophobicity and improving the compatibility of LDHs dispersed in non-polar materials. However, the surface modification of conventional LDHs in hydrous conditions typically results in aggregated particle morphologies, low surface areas and accessible pore volumes. In this study, well dispersed and high surface area silane grafted AMO-Zn₂MgAl-CO₃ LDH were prepared using the silane coupling agents (triethoxyvinylsilane (TEVS), triethoxyoctylsilane (TEOS) and (3-glycidyloxypropyl)trimethoxysilane (TMGPS)) in anhydrous acetone. Solution ¹H NMR spectroscopy was initially used to study the rate and extent of silane reactivity with AMO-Zn₂MgAl-CO₃ LDH. Powder XRD, TEM, N₂ BET specific surface area and total pore volume measurements showed that the structure and morphology of silane-treated AMO-Zn₂MgAl-CO₃ LDHs remained largely unchanged. Solid state ¹³C CP-MAS, ²⁷Al DP-MAS and ²⁹Si CP-MAS NMR spectroscopy indicates that the silanes have been successfully grafted onto the surface of the LDH. In addition to maintaining their structure, morphology, high surface area and total pore volume, these surface-functionalised LDHs are now more hydrophobic, displaying a saturation water vapour uptake (<4 wt%) that is ca. 60% lower than the untreated AMO-LDH.

Aspect Ratio Control of Layered Double Hydroxide Nanosheets and Their Application for High Oxygen Barrier Coating in Flexible Food Packaging

We report a method to rationally control the aspect ratio of layered double hydroxide for use as a barrier coating for food packaging films. The reconstruction of a Mg₂Al-layered double oxide (LDO) in concentrated aqueous glycine solutions produces dispersions of Mg₂Al-LDH nanosheets. The nanosheet thickness decreases and diameter increases with increasing reconstruction time from 16 to 96 h. We observe a limiting nanosheet aspect ratio of ca. 336 ± 170. These Mg₂Al-LDH nanosheets can be dispersed in PVA to give a water-based dispersion that can be used to coat flexible polymeric films. Oxygen transmission rate (OTR) of a PET film decreases when the thickness of the dried coated layer increases, an OTR of <0.005 mL·m^-2·day^-1 is observed for a coating with thickness of 1175 ± 101 nm.

Lignin Redistribution for Enhancing Barrier Properties of Cellulose-Based Materials

Renewable cellulose-based materials have gained increasing interest in food packaging because of its favorable biodegradability and biocompatibility, whereas the barrier properties of hydrophilic and porous fibers are inadequate for most applications. Exploration of lignin redistribution for enhancing barrier properties of paper packaging material was carried out in this work. The redistribution of nanolized alkali lignin on paper surface showed excellent water, grease, and water vapor barrier. It provided persisted water (contact angle decrease rate at 0.05°/s) and grease (stained area undetectable at 72 h) resistance under long-term moisture or oil direct contact conditions, which also inhibited the bacterial growth to certain degree. Tough water vapor transmission rate can be lowered 82% from 528 to 97 g/m2/d by lignin redistribution. The result suggests that alkali lignin, with multiple barrier properties, has great potential in bio-based application considering the biodegradability, biocompatibility, and recyclability.

Reliability of Protective Coatings for Flexible Piezoelectric Transducers in Aqueous Environments

Electronic devices used for marine applications suffer from several issues that can compromise their performance. In particular, water absorption and permeation can lead to the corrosion of metal parts or short-circuits. The added mass due to the absorbed water affects the inertia and durability of the devices, especially for flexible and very thin micro-systems. Furthermore, the employment of such delicate devices underwater is unavoidably subjected to the adhesion of microorganisms and formation of biofilms that limit their reliability. Thus, the demand of waterproofing solutions has increased in recent years, focusing on more conformal, flexible and insulating coatings. This work introduces an evaluation of different polymeric coatings (parylene-C, poly-dimethyl siloxane (PDMS), poly-methyl methacrylate (PMMA), and poly-(vinylidene fluoride) (PVDF)) aimed at increasing the reliability of piezoelectric flexible microdevices used for sensing water motions or for scavenging wave energy. Absorption and corrosion tests showed that Parylene-C, while susceptible to micro-cracking during prolonged oscillating cycles, exhibits the best anti-corrosive behavior. Parylene-C was then treated with oxygen plasma and UV/ozone for modifying the surface morphology in order to evaluate the biofilm formation with different surface conditions. A preliminary characterization through a laser Doppler vibrometer allowed us to detect a reduction in the biofilm mass surface density after 35 days of exposure to seawater.