p-Phenylenediamine-Bridged Binder-Electrolyte-Unified Supramolecules for Versatile Lithium Secondary Batteries.

The binder is an essential component in determining the structural integrity and ionic conductivity of Li-ion battery electrodes. However, conventional binders are not sufficiently conductive and durable to be used with solid-state electrolytes. In this study, a novel system is proposed for a Li secondary battery that combines the electrolyte and binder into a unified structure, which is achieved by employing para-phenylenediamine (pPD) moiety to create supramolecular bridges between the parent binders. Due to a partial crosslinking effect and charge-transferring structure of pPD, the proposed strategy improves both the ionic conductivity and mechanical properties by a factor of 6.4 (achieving a conductivity of 3.73 × 10-4 S cm-1 for poly(ethylene oxide)-pPD) and 4.4 (reaching a mechanical strength of 151.4 kPa for poly(acrylic acid)-pPD) compared to those of conventional parent binders. As a result, when the supramolecules of pPD are used as a binder in a pouch cell with a lean electrolyte loading of 2 µL mAh-1 , a capacity retention of 80.2% is achieved even after 300 cycles. Furthermore, when it is utilized as a solid-state electrolyte, an average Coulombic efficiency of 99.7% and capacity retention of 98.7% are attained under operations at 50 °C without external pressure or a pre-aging process.

Harnessing Liquid Crystal Sensors for High-Throughput Real-Time Detection of Structural Changes in Lysozyme during Refolding Processes.

Despite the rapid advances in process analytical technology, the assessment of protein refolding efficiency has largely relied on off-line protein-specific assays and/or chromatographic procedures such as reversed-phase high-performance liquid chromatography and size exclusion chromatography. Due to the inherent time gap pertaining to traditional methods, exploring optimum refolding conditions for many recombinant proteins, often expressed as insoluble inclusion bodies, has proven challenging. The present study describes a novel protein refolding sensor that utilizes liquid crystals (LCs) to discriminate varying protein structures during unfolding and refolding. An LC layer containing 4-cyano-4'-pentylbiphenyl (5CB) intercalated with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) is used as a sensing platform, and its proof-of-concept performance is demonstrated using lysozyme as a model protein. As proteins unfold or refold, a local charge fluctuation at their surfaces modulates their interaction with zwitterionic phospholipid DOPE. This alters the alignment of DOPE molecules at the aqueous/LC interface, affecting the orientational ordering of bulk LC (i.e., homeotropic to planar for refolding and planar to homeotropic for unfolding). Differential polarized optical microscope images of the LC layer are subsequently generated, whose brightness directly linked to conformational changes of lysozyme molecules is quantified by gray scale analysis. Importantly, our LC-based refolding sensor is compatible with diverse refolding milieus for real-time analysis of lysozyme refolding and thus likely to facilitate the refolding studies of many proteins, especially those lacking a method to determine structure-dependent biological activity.

Controlled synthesis of solid-shelled non-spherical and faceted microbubbles.

The ability to control the shape of hollow particles (e.g., capsules or bubbles) holds great promise for enhancing the encapsulation efficiency and mechanical/optical properties. However, conventional preparation methods suffer from a low yield, difficulty in controlling the shape, and a tedious production process, limiting their widespread application. Here, we present a method for fabricating polyhedral graphene oxide (GO)-shelled microbubbles with sharp edges and vertices, which is based on the microfluidic generation of spherical compound bubbles followed by shell deformation. Sphere-to-polytope deformation is a result of the shell instability due to gradual outward gas transport, which is dictated by Laplace pressure across the shell. The shape-variant behaviours of the bubbles can also be attributed to the compositional heterogeneity of the shells. In particular, the high degree of control of microfluidic systems enables the formation of non-spherical bubbles with various shapes; the structural motifs of the bubbles are easily controlled by varying the size and thickness of the mid-shell in compound bubbles, ranging from tetrahedra to octahedra. The strategy presented in this study provides a new route for fabricating 3D structured solid bubbles, which is particularly advantageous for the development of high-performance mechanical or thermal material applications.

Patchwork-Structured Heterointerface of 1T-WS2/a-WO3 with Sustained Hydrogen Spillover as a Highly Efficient Hydrogen Evolution Reaction Electrocatalyst.

Using tungsten disulfide (WS2) as a hydrogen evolution reaction (HER) electrocatalyst brought on several ways to surpass its intrinsic catalytic activity. This study introduces a nanodomain tungsten oxide (WO3) interface to 1T-WS2, opening a new route for facilitating the transfer of a proton to active sites, thereby enhancing the HER performance. After H2S plasma sulfurization on the W layer to realize nanocrystalline 1T-WS2, subsequent O2 plasma treatment led to the formation of amorphous WO3 (a-WO3), resulting in a patchwork-structured heterointerface of 1T-WS2/a-WO3 (WSO). Addition of a hydrophilic interface (WO3) facilitates the hydrogen spillover effect, which represents the transfer of absorbed protons from a-WO3 to 1T-WS2. Moreover, the faster response of the cathodic current peak (proton insertion) in cyclic voltammetry is confirmed by the higher degree of oxidation. The rationale behind the faster proton insertion is that the introduced a-WO3 works as a proton channel. As a result, WSO-1.2 (the ratio of 1T-WS2 to a-WO3) exhibits a remarkable HER activity in that 1T-WS2 consumes more protons provided by the channel, showing an overpotential of 212 mV at 10 mA/cm2. Density functional theory calculations also show that the WO3 phase gives higher binding energies for initial proton adsorption, while the 1T-WS2 phase shows reduced HER overpotential. This improved catalytic performance demonstrates a novel strategy for water splitting to actively elicit the related reaction via efficient proton transport.

Self-Assembly of Hausmannite Mn3O4 Triangular Structures on Cocosin Protein Scaffolds for High Energy Density Symmetric Supercapacitor Application.

Recent advances in using biological scaffolds for nanoparticle synthesis have proven to be useful for preparing various nanostructures with uniform shape and size. Proteins are significant scaffolds for generating various nanostructures partly because of the presence of many functional groups to recognize different chemistries. In this endeavor, cocosin protein, an 11S allergen, is prepared from coconut fruit and employed as a potential scaffold for synthesizing Mn3O4 materials. The interaction between protein and manganese ions is studied in detail through isothermal calorimetric titration. At increased scaffold availability, the Mn3O4 material adopts the exact hexamer structure of the cocosin protein. The electrochemical supercapacitive properties of the cocosin-Mn3O4 material are found to have a high specific capacitance of 751.3 F g-1 at 1 A g-1 with cyclic stability (92% of capacitance retention after 5000 CV cycles) in a three-electrode configuration. The Mn3O4//Mn3O4 symmetric supercapacitor device delivers a specific capacitance of 203.8 F g-1 at 1 A g-1 and an outstanding energy and power density of 91.7 W h kg-1 and 899.5 W kg-1, respectively. These results show that cocosin-Mn3O4 could be considered a suitable electrode for energy storage applications. Moreover, the cocosin protein to be utilized as a novel scaffold in protein-nanomaterial chemistry could be useful for protein-assisted inorganic nanostructure synthesis in the future.

Strong Bathochromic Shift of Conjugated Polymer Nanowires Assembled with a Liquid Crystalline Alkyl Benzoic Acid via a Film Dispersion Process.

We present aqueous dispersions of conjugated polymer nanowires (CPNWs) with improved light absorption properties aimed at aqueous-based applications. We assembled films of a donor-acceptor-type conjugated polymer and liquid crystalline 4-n-octylbenzoic acid by removing a cosolvent of their mixture solutions, followed by annealing of the films, and then formed aqueous-dispersed CPNWs with an aspect ratio >1000 by dispersing the films under ultrasonication at a basic pH. X-ray and spectroscopy studies showed that the polymer and liquid crystal molecules form independent domains in film assemblies and highly organized layer structures in CPNWs. Our ordered molecular assemblies in films and aqueous dispersions of CPNWs open up a new route to fabricate nanowires of low-band-gap linear conjugated polymers with the absorption maximum at 794 nm remarkably red-shifted from 666 nm of CPNWs prepared by an emulsion process. Our results suggest the presence of semicrystalline polymorphs ß1 and ß2 phases in CPNWs due to long-range π-π stacking of conjugated backbones in compactly organized lamellar structures. The resulting delocalization with a reduced energy bang gap should be beneficial for enhancing charge transfer and energy-conversion efficiencies in aqueous-based applications such as photocatalysis.

A NiCoP nanocluster-anchored porous Ti3C2Tx monolayer as high performance hydrogen evolution reaction electrocatalysts.

MXenes have received much attention as promising candidates for noble metal-free hydrogen evolution reaction (HER) electrocatalysts due to their high electrical conductivity, surface hydrophilicity, abundant surface functional groups, and great potential for rational hybridization with other materials. Herein, a novel porous monolayered-Ti3C2Tx@NiCoP (P-Ti3C2Tx@NiCoP) nanostructure was synthesized with uniform distribution of bimetallic compounds for improved charge transfer capability and electrocatalytic activity. In experiments, H2O2-utilized oxidation formed a highly mesoporous structure with a maximized surface area of monolayered MXenes as the support. A subsequent solvothermal process followed by phosphidation enabled successful anchoring of highly HER-active NiCoP nanoclusters onto abundantly exposed terminal edges of the P-Ti3C2Tx support. The structural porosity of the P-Ti3C2Tx nanoflakes played an important role in creating additional room for embedding catalytically active species while stably imparting high electrical conductivity to accelerate charge transfer to NiCoP nanoclusters. With structural modification and effective hybridization, P-Ti3C2Tx@NiCoP showed highly enhanced HER activity with significantly lower overpotentials of 115 and 101 mV at a current density of -10 mA cm-2 in 0.5 M H2SO4 and 1.0 M KOH, respectively, along with showing long-term stability over 60 h. As such, our approach of designing structurally modified-Ti3C2Tx and hybridizing with other electrocatalytically active species would function as a solid platform for implementing Ti3C2Tx-based hetero-nanostructures to achieve state-of-the-art performance in next-generation energy conversion applications.

Low-Temperature Synthesis of Wafer-Scale MoS2-WS2 Vertical Heterostructures by Single-Step Penetrative Plasma Sulfurization.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted considerable attention owing to their synergetic effects with other 2D materials, such as graphene and hexagonal boron nitride, in TMD-based heterostructures. Therefore, it is important to understand the physical properties of TMD-TMD vertical heterostructures for their applications in next-generation electronic devices. However, the conventional synthesis process of TMD-TMD heterostructures has some critical limitations, such as nonreproducibility and low yield. In this paper, we synthesize wafer-scale MoS2-WS2 vertical heterostructures (MWVHs) using plasma-enhanced chemical vapor deposition (PE-CVD) via penetrative single-step sulfurization discovered by time-dependent analysis. This method is available for fabricating uniform large-area vertical heterostructures (4 in.) at a low temperature (300 °C). MWVHs were characterized using various spectroscopic and microscopic techniques, which revealed their uniform nanoscale polycrystallinity and the presence of vertical layers of MoS2 and WS2. In addition, wafer-scale MWVHs diodes were fabricated and demonstrated uniform performance by current mapping. Furthermore, mode I fracture tests were performed using large double cantilever beam specimens to confirm the separation of the MWVHs from the SiO2/Si substrate. Therefore, this study proposes a synthesis mechanism for TMD-TMD heterostructures and provides a fundamental understanding of the interfacial properties of TMD-TMD vertical heterostructures.

A Robust Fabrication Technique for Hydrogel Films Containing Micropatterned Opal Structures via Micromolding and an Integrated Evaporative Deposition-Photopolymerization Approach.

Opal-structured thin-film hydrogel materials with micropatterns hold great potential for utility in a wide range of sensing applications. Micropatterning offers key advantages such as ready addressability, high throughput assay, and multiplexing. However, controlled fabrication of such films in a rapid, inexpensive, and reliable manner remains a challenge. Existing techniques suffer from long opal deposition times and often involve complex and arduous steps. In this report, we examined a simple micromolding-based evaporation-polymerization method for the fabrication of poly(ethylene glycol)-based hydrogel films containing micropatterned opal structures. Specifically, intense and uniform opalescent colors were achieved by evaporative deposition of polystyrene bead solution in patterned micromolds. These opal micropatterns were then captured in hydrogel films by simple photopolymerization of a UV-curable PEG diacrylate solution. The as-prepared films show high tunability as well as responsiveness to various environmental cues readily manifested via shifts in color. Combined with UV-vis reflectance spectroscopy and scanning electron microscopy results, these findings illustrate the robust, simple, and reliable nature of our integrated deposition-polymerization approach for controlled fabrication of optically active and stimuli-responsive functional materials. We thus envision that the results and the facile approach reported here can be extended to many application areas including environmental monitoring, diagnostics, and biosensing applications.

Microfluidic Synthesis of Carbon Nanotube-Networked Solid-Shelled Bubbles.

Carbon nanotubes (CNTs) have attracted considerable attention because of their high electrical conductivity and outstanding mechanical properties. As such, there have been numerous attempts to form CNTs into diverse structures for use in a wide range of applications. However, the intrinsic high aspect ratios of CNTs and resulting deformability have prevented the fabrication of sophisticated CNT-based structures, especially for three-dimensional (3D) cellular architectures. To challenge this limitation, we present a novel method to fabricate a 3D CNT cellular network from the assembly of microfluidically synthesized CNT-shelled microbubbles. We successfully generated stable spherical CNT-shelled bubbles with excellent size and shape uniformity by precisely controlling bubble dimensions by varying microfluidic variables. We also developed a fundamental understanding of the bubble stability, which allowed us to suppress shrinkage-induced deformation. The synthesized CNT-shelled bubbles were assembled into a 3D close-packed structure, followed by treatment with thermal reduction to induce interfacial bonding and transformation into a closed cellular network structure. Overall, this work provides a new strategy of assembling 1D nanomaterials as the building blocks for well-regulated 3D closed cellular architectures with improved structural or physical properties.

Metal-Phenolic Network-Coated Hyaluronic Acid Nanoparticles for pH-Responsive Drug Delivery.

Although self-assembled nanoparticles (SNPs) have been used extensively for targeted drug delivery, their clinical applications have been limited since most of the drugs are released into the blood before they reach their target site. In this study, metal-phenolic network (MPN)-coated SNPs (MPN-SNPs), which consist of an amphiphilic hyaluronic acid derivative, were prepared to be a pH-responsive nanocarrier to facilitate drug release in tumor microenvironments (TME). Due to their amphiphilic nature, SNPs were capable of encapsulating doxorubicin (DOX), chosen as the model anticancer drug. Tannic acid and FeCl3 were added to the surface of the DOX-SNPs, which allowed them to be readily coated with MPNs as the diffusion barrier. The pH-sensitive MPN corona allowed for a rapid release of DOX and effective cellular SNP uptake in the mildly acidic condition (pH 6.5) mimicking TME, to which the hyaluronic acid was exposed to facilitate receptor-mediated endocytosis. The DOX-loaded MPN-SNPs exhibited a higher cytotoxicity for the cancer cells, suggesting their potential use as a drug carrier in targeted cancer therapy.

Carbonization/oxidation-mediated synthesis of MOF-derived hollow nanocages of ZnO/N-doped carbon interwoven by carbon nanotubes for lithium-ion battery anodes.

Transition metal oxide (TMO)-based anode materials for Li-ion batteries (LIBs) have generally suffered from limitations of intrinsically severe pulverization upon lithiation and reduced electrical conductivity. To address these issues, an approach of generating hollow nanostructures of TMOs complexed with highly conductive species has been attempted. As a novel means to implement highly electrochemically active TMO-based hollow nanostructures, a pre-synthesized template of a metal organic framework, zeolitic imidazolate framework (ZIF-8), was sequentially treated with partial carbonization and oxidation processes, whereby a hollow, nanocage-like structure of ZnO was obtained while preserving the carbonaceous frame as the electroconductive matrix. Furthermore, through additional incorporation of carbon nanotubes (CNTs), hollow nanocages of ZnO/N-doped carbon were successfully interwoven to form a well-complexed three-dimensional network, imparting enhanced electrical conductivity and mechanical stability to the complexes. When the synthesized ternary nanocomposites of ZnO/N-doped carbon/CNTs were used as anodes of LIBs, enhanced electrochemical performance was achieved, with high specific capacity, excellent rate capability, and greatly extended cycling stability, which could be attributed to the facilitated Li-ion diffusivity and improved electrical conductivity. Therefore, it is highly expected that the proposed strategy could be extended as a general platform for realizing uniquely structured TMO-based electrode materials for high-performance energy storage systems.

Si nanoparticle clusters in hollow carbon capsules (SNC@C) as lithium battery anodes: toward high initial coulombic efficiency.

Large volumetric expansion and structural pulverization have been major problems in Si-based anode materials for Li-ion batteries. To overcome this limitation, yolk-shell structured Si-carbon structures have been proposed to allow for the reversible structural breathing of Si nanoparticles confined inside the carbon shell. However, initial coulombic efficiency (ICE) of the yolk-shell structured anodes is highly decreased mainly due to their extremely high specific surface area (SSA) and the resulting excessive formation of solid electrolyte interphase (SEI) over the carbon shell. Here, instead of using a single Si nanoparticle-containing yolk-shell structure, we propose a novel structure comprising hollow carbon capsules internally encapsulating Si nanoparticle clusters (SNC@Cs). To implement this structural design, Si nanoparticle clusters are encompassed by a polystyrene matrix (SNC@PS) by emulsion polymerization, followed by coating with a polydopamine (PDA) layer (SNC@PS@PDA). Then, after annealing them for carbonization, SNC@Cs are finally prepared, which can decrease the SSA by a factor of one-third compared to the conventional yolk-shell structures. These SNC@C particles have shown remarkably high ICE values of up to 81%. Moreover, the cycling stability could be improved up to 100 cycles because the properly confined Si cluster inside the stable carbon capsule mitigates structural pulverization during repeated lithiation-delithiation processes of Si nanoparticles.

Hydrogen bonding-based strongly adhesive coacervate hydrogels synthesized using poly(N-vinylpyrrolidone) and tannic acid.

When multiple intermolecular interactions occur simultaneously, complexed molecules undergo gelation by inter-cohesive bonding, inducing a pseudo-crosslinking effect to form a supramolecular gel. Among the number of substances that can induce supramolecular assembly, phenolic species such as 3,4-dihydroxy-l-phenylalanine (DOPA) are widely utilized for synthesizing adhesive materials. However, despite the strong adhesion capability of monomeric phenol, it lacks cohesive strength and rarely forms a supramolecular gel to secure its mechanical properties. In this study, to overcome this obstacle, we synthesized a supramolecular coacervate hydrogel by simply mixing poly(N-vinylpyrrolidone) (PVP) and tannic acid (TA), resulting in strong cohesive interactions by virtue of the larger molecular size of TA and reinforced molecular interactions attributed to the presence of galloyl groups with a high density. We further analyzed the rheological and adhesive properties of PVP-TA coacervate hydrogels, revealing that they could exhibit not only a self-healing property, but also super adhesive properties with an average adhesion strength of 3.71 MPa on a glass substrate, which is >4 times stronger than that of conventional PVP.

Structurally Controlled Cellular Architectures for High-Performance Ultra-Lightweight Materials.

The design and synthesis of cellular structured materials are of both scientific and technological importance since they can impart remarkably improved material properties such as low density, high mechanical strength, and adjustable surface functionality compared to their bulk counterparts. Although reducing the density of porous structures would generally result in reductions in mechanical properties, this challenge can be addressed by introducing a structural hierarchy and using mechanically reinforced constituent materials. Thus, precise control over several design factors in structuring, including the type of constituent, symmetry of architectures, and dimension of the unit cells, is extremely important for maximizing the targeted performance. The feasibility of lightweight materials for advanced applications is broadly explored due to recent advances in synthetic approaches for different types of cellular architectures. Here, an overview of the development of lightweight cellular materials according to the structural interconnectivity and randomness of the internal pores is provided. Starting from a fundamental study on how material density is associated with mechanical performance, the resulting structural and mechanical properties of cellular materials are investigated for potential applications such as energy/mass absorption and electrical and thermal management. Finally, current challenges and perspectives on high-performance ultra-lightweight materials potentially implementable by well-controlled cellular architectures are discussed.

Electrostatically regulated ternary-doped carbon foams with exposed active sites as metal-free oxygen reduction electrocatalysts.

Pt, a representative electrocatalyst for the oxygen reduction reaction (ORR), has suffered from high cost and poor stability, and thus it is essential to develop alternative electrocatalyst with a high catalytic activity comparable to Pt. Herein, we propose a rationally designed metal-free electrocatalyst with exposed active sites using an N, P, and S ternary-doped and graphene-incorporated porous carbon foam. We developed a novel template-free synthetic approach wherein the electrostatically-mediated complexation of graphene oxide (GO) with 2-aminothiazole (2AT) and branched polyethylenimine (PEI) in the presence of phytic acid (PA) was first induced, followed by a carbonization process to drive the formation of a three-dimensionally interconnected porous carbon foam. The resulting electrocatalyst exhibited a high pore volume and greatly extended specific surface area along with exposed active sites. Benefiting from these properties, the synthesized ternary-doped carbon foam displayed an outstanding electrocatalytic activity for the oxygen reduction ORR through four-electron transfer pathways. We observed that the remarkably improved ORR performance of the synthesized materials manifested an onset and a half-wave potential, mostly close to those of the commercially available ORR electrocatalyst of 20 wt% Pt/C while securing a greater stability in alkaline media.

A Plesiohedral Cellular Network of Graphene Bubbles for Ultralight, Strong, and Superelastic Materials.

Advanced materials with low density and high strength impose transformative impacts in the construction, aerospace, and automobile industries. These materials can be realized by assembling well-designed modular building units (BUs) into interconnected structures. This study uses a hierarchical design strategy to demonstrate a new class of carbon-based, ultralight, strong, and even superelastic closed-cellular network structures. Here, the BUs are prepared by a multiscale design approach starting from the controlled synthesis of functionalized graphene oxide nanosheets at the molecular- and nanoscale, leading to the microfluidic fabrication of spherical solid-shelled bubbles at the microscale. Then, bubbles are strategically assembled into centimeter-scale 3D structures. Subsequently, these structures are transformed into self-interconnected and structurally reinforced closed-cellular network structures with plesiohedral cellular units through post-treatment, resulting in the generation of 3D graphene lattices with rhombic dodecahedral honeycomb structure at the centimeter-scale. The 3D graphene suprastructure concurrently exhibits the Young's modulus above 300 kPa while retaining a light density of 7.7 mg cm-3 and sustaining the elasticity against up to 87% of the compressive strain benefiting from efficient stress dissipation through the complete space-filling closed-cellular network. The method of fabricating the 3D graphene closed-cellular structure opens a new pathway for designing lightweight, strong, and superelastic materials.

Layer-by-layer assembled multilayers of charged polyurethane and graphene oxide platelets for flexible and stretchable gas barrier films.

With the advent of the era of consumer-oriented displays and mobile devices, the importance of barrier film coatings for securing devices from oxygen or moisture penetration has become more salient. Recently developed approaches to generate gas barrier films in a combination of polyelectrolyte multilayer matrices and incorporated inorganic nanosheets have shown great potential in outperforming conventional gas barrier films. However, these films have the intrinsic drawback of vulnerability to brittleness and inability to stretch for flexible device applications. To overcome this issue, we present a method in which we prepare multilayered films of complementarily charged polyurethane and graphene oxide platelets using spin-assisted, layer-by-layer self-assembly to obtain well-stacked film structures. As a result, the multilayered, thin films deposited on a poly(ethylene terephthalate) (PET) substrate can exhibit significantly reduced oxygen penetration properties (∼30 cc m-2 day-1 for the oxygen transmission rate) while still demonstrating large bending or stretching deformations. Therefore, the proposed approach in this study is anticipated to be extensively utilized for surface coating and protection of flexible and stretchable devices under various operating conditions.

Cumulative energy analysis of thermally-induced surface wrinkling of heterogeneously multilayered thin films.

Wrinkling is a well-known example of instability-driven surface deformation that occurs when the accumulated compressive stress exceeds the critical value in multilayered systems. A number of studies have investigated the instability conditions and the corresponding mechanisms of wrinkling deformation. Force balance analysis of bilayer systems, in which the thickness of the capping layer is importantly considered, has offered a useful approach for the quantitative understanding of wrinkling. However, it is inappropriate for multilayer wrinkling (layer number > 3) consisting of heterogeneous materials (e.g. polymer/metal or inorganic), in which the thickness variation in the substrate is also crucial. Therefore, to accommodate the additive characteristics of multilayered systems, we thermally treated tri- or quad-layer samples of polymer/metal multilayers to generate surface wrinkles and used a cumulative energy balance analysis to consider the individual contribution of each constituent layer. Unlike the composite layer model, wherein the thickness effect of the capping layer is highly overestimated for heterogenously stacked multilayers, our approach precisely reflects the bending energy contribution of the given multilayer system, with results that match well with experimental values. Furthermore, we demonstrate the feasibility of this approach as a metrological tool for simple and straightforward estimation of the thermomechanical properties of polymers, whereby a delicate change in the Young's modulus of a thin polymeric layer near its glass transition temperature can be successfully monitored.

Mediator- and co-catalyst-free direct Z-scheme composites of Bi2WO6-Cu3P for solar-water splitting.

Exploring new single, active photocatalysts for solar-water splitting is highly desirable to expedite current research on solar-chemical energy conversion. In particular, Z-scheme-based composites (ZBCs) have attracted extensive attention due to their unique charge transfer pathway, broader redox range, and stronger redox power compared to conventional heterostructures. In the present report, we have for the first time explored Cu3P, a new, single photocatalyst for solar-water splitting applications. Moreover, a novel ZBC system composed of Bi2WO6-Cu3P was designed employing a simple method of ball-milling complexation. The synthesized materials were examined and further investigated through various microscopic, spectroscopic, and surface area characterization methods, which have confirmed the successful hybridization between Bi2WO6 and Cu3P and the formation of a ZBC system that shows the ideal position of energy levels for solar-water splitting. Notably, the ZBC composed of Bi2WO6-Cu3P is a mediator- and co-catalyst-free photocatalyst system. The improved photocatalytic efficiency obtained with this system compared to other ZBC systems assisted by mediators and co-catalysts establishes the critical importance of interfacial solid-solid contact and the well-balanced position of energy levels for solar-water splitting. The promising solar-water splitting under optimum composition conditions highlighted the relationship between effective charge separation and composition.