Search Results (162)

This study presents a novel fabrication approach for the precise patterning of conductive polymer coatings (graphene/PEDOT:PSS) on flexible substrates. Traditional lithographic methods often result in chemical or thermal degradation of polymer chains, compromising electrical conductivity. The proposed method utilizes an inversely structured gold nanocoating (400–450 nm) as a sacrificial template. By employing a selective lift-off process in a potassium iodide solution, high-resolution polymer topologies are achieved without damaging the active material. The resulting structures exhibit a sheet resistance of 90–100 Ω/sq and maintain linear sensitivity to temperature and humidity, making them suitable for next-generation wearable medical diagnostics. Full article

Benefiting from their outstanding porosity, considerable specific surface area, and natural flexibility, cellulose nanofibers (CNFs)/MOF materials have emerged as competitive candidates for advanced flexible energy storage devices. However, conventional CNFs/MOFs aerogels or films often suffer from poor recoverability under compression, bending, and folding, accompanied by severe plastic deformation that compromises the cycling and structural stability of devices. To address this issue, we report a rationally designed flexible PU/CNFs/ZIF-8/PANI composite foam with an interconnected micro-mesoporous structure. Using polyurethane foam as a soft substrate and CNFs/ZIF-8 as building blocks, the composite was fabricated through a combined strategy of impregnation, in situ ZIF-8 growth, hot-pressing, and in situ aniline polymerization with simultaneous etching of the ZIF-8. The incorporation of carboxylated CNFs enhances the hydrophilicity of the PU skeleton. This, in combination with the hot-pressed framework, establishes an interconnected 3D network, thereby effectively preventing the agglomeration of active materials. Meanwhile, the hierarchical pores derived from the sacrificial ZIF-8 template provide abundant electroactive sites, accelerate ion transport, and facilitate high PANI loading. By virtue of this synergistic architectural effect, the resultant electrode achieves a high specific capacitance of 449 F/g at 0.2 A/g, with 97% capacitance retention after 2000 cycles at 5 A/g. Furthermore, the composite foam demonstrates excellent mechanical flexibility, with a tensile strength of 0.87 MPa and an elongation at break of 230%. This work offers a feasible approach for developing high-performance flexible supercapacitors and provides novel perspectives for the rational design of portable energy storage devices. Full article

Hollow hydrogels are promising for flexible electronics and bioengineering, yet their fabrication is limited by sacrificial templates, specialized equipment, and complex engineering processes. Herein, a facile wet-spinning strategy is developed to fabricate sodium alginate (SA) hollow hydrogels. Extruding SA/CaCO₃ precursor suspension into an acidic coagulation bath induces simultaneous ionic cross-linking and in situ CO₂ generation, driving the self-formation of hollow tubular architectures with tunable morphologies, mechanical performance, macroscopic architecture, and functional properties. Moreover, the introduction of secondary cross-linking enhances the SA hydrogels’ water retention and resistance to freezing conditions. Utilizing their intrinsic ionic conductivity, the hollow hydrogels demonstrate outstanding sensing performance, enabling reliable detection of both large-amplitude limb motions and subtle muscle activity in the human body. Furthermore, hollow hydrogel tubes with diverse geometries can be readily fabricated by simply modifying the spinning mold, thereby broadening their potential applications. In vitro cytotoxicity assessments further confirm that the SA hollow hydrogels exhibit excellent biocompatibility with minimal cytotoxicity, satisfying the fundamental criteria for bioengineering applications. The combination of a simple yet controllable fabrication strategy with the intrinsic multifunctionality of the SA hollow tubes confers substantial potential for their deployment in bioengineering and flexible electronic applications. Full article

Rechargeable zinc–air batteries (ZABs) are still impeded by the intrinsically sluggish kinetics of oxygen reduction and evolution reactions (ORR/OER) and by the instability or prohibitive price of state-of-the-art noble metal catalysts. Metal–organic frameworks (MOFs) have recently emerged as versatile sacrificial templates for next-generation air–cathode electrocatalysts. By programming pyrolytic or chemical conversion pathways, MOFs can be quantitatively transformed into hierarchically porous, heteroatom-doped carbon scaffolds that embed uniform metal, alloy, or metal-oxide nanodomains. The resulting architectures couple metallic conductivity with molecular-scale active site tunability, delivering exceptional ORR/OER activity, stability, and mass transport properties. This review critically examines the most recent advances in MOF-derived electrocatalysts for ZABs, establishing quantitative structure–composition–performance relationships across mono-, bi-, and multi-metallic systems. Emphasis is placed on deciphering how framework topology, metal–ligand coordination, and post-synthetic parameters dictate the density, electronic structure, and accessibility of surface-active moieties during catalyst evolution. We further dissect engineering strategies that enhance intrinsic activity via electronic modulation, bolster durability through encapsulation effects, and optimize hierarchical porosity for rapid O₂/water transport. This article concludes by outlining unresolved challenges and future research directions, including atomically precise active site construction, multi-scale compositional control, long-term reversibility under realistic ZABs cycles, scalable and green synthesis, providing a roadmap for translating MOF-derived catalysts from laboratory curiosities to commercially viable air–cathode materials. Full article

Cellulose nanofibers/metal-organic framework (CNFs/MOF) composites hold promise for energy storage thanks to high porosity, large specific surface area, and inherent flexibility, but their poor conductivity limits applications to environmental remediation and gas adsorption. Herein, flexible CNFs served as substrates for in situ growth of continuous ZIF-8 nanolayers via interfacial synthesis, with a CNFs/ZIF-8 gel network built to enhance structural integrity and flexibility. A novel strategy first regulated the layered pore structure: ZIF-8 in CNFs/ZIF-8 nanofibers was etched in the acidic environment of aniline in situ polymerization, constructing a hierarchical porous architecture with interconnected micropores and mesopores. CNFs/ZIF-8/PANI gel composite membranes were then fabricated. As self-supporting electrodes for symmetric supercapacitors, the composites showed excellent electrochemical performance: 1350 F/g at 1 A/g for the electrode, and the flexible solid-state device delivered a specific capacitance of 220.9 F/g at 0.5 A/g, along with a capacitance retention rate of 74% after 5000 charge–discharge cycles at 10 A/g. The superior performance stems from synergistic hierarchical pore structure regulation via partial MOF sacrificial templating and gel matrix-mediated rapid ion diffusion, offering a feasible approach for high-performance flexible energy storage devices. Full article

Three-dimensional ZnO structures were prepared by both thermal atomic layer deposition (ThALD) and plasma-enhanced atomic layer deposition (PEALD) on a sacrificial cellulose template. The synthetic approach consisted of ALD of conformal ZnO nanofilms on the fibrous cellulose template, followed by thermal removal of the polymer. The resulting calcinated samples, consisting of a scaffold of fused polycrystalline ZnO nanoparticles, showed a sevenfold and ninefold increase in photocatalytic activity against methyl orange under ultraviolet-A light, for the ThALD and PEALD samples, respectively, compared to the non-calcined samples prior to cellulose removal. In addition to the improved three-dimensional surface exposure and accessible active sites, it was suggested that the amount of hydroxyl groups on the surface and the density of nanoparticle packing in 3D ZnO structures are critical parameters for improving the photoinduced degradation of the dye. Full article

Three-dimensional (3D) cell culture systems require biocompatible carriers that provide both structural support and efficient mass transport. Conventional alginate-based encapsulation systems suffer from poor molecular diffusion, lack of cell adhesion motifs, and structural instability under physiological conditions. Here, we report the first development of hollow-shell collagen microcapsules (CMCs) fabricated via a gelatin sacrificial template approach that overcomes these critical limitations. The hollow architecture combined with collagen’s intrinsic bioactivity achieved 2.5-fold enhancement in molecular permeability compared to conventional alginate beads, while maintaining structural integrity for 14 days versus 3-day collapse of alginate controls. NIH 3T3 fibroblasts encapsulated within CMCs demonstrated superior proliferation and formed tissue-like multilayered structures with extensive extracellular matrix deposition. This platform represents a significant advance in 3D cell culture technology, providing a biologically functional microenvironment with enhanced mass transport properties for applications in tissue engineering and regenerative medicine. Full article

In this study, surface-modified bio-based hydrogels derived from crosslinked quaternized chitosan (MQCGs) were developed to treat PFAS-contaminated water. The novelty of this work lies in the surface modification and engineering of the hydrogels to enhance the surface area and positive charge of the hydrogels through sacrificial templating. By blending the chitosan solution with polyethylene glycol (PEG) and then removing PEG via sacrificial templating, microscale channels were created on the surface of the hydrogels. This increased the availability of the hydrogel’s positive charges for increased electrostatic interactions with PFAS, achieving >98% PFOS (a long-chain PFAS) adsorption in less than 30 min. Batch adsorption experiments demonstrated that surface-modified quaternized chitosan hydrogels (MQCGs) removed both long- and short-chain PFAS across a pH range of 3 to 12, maintaining their performance over 10 regeneration cycles. The adsorption behavior followed the Freundlich isotherm model and pseudo-second-order kinetics, indicating fast multilayer adsorption on heterogeneous active sites via the combined actions of electrostatic, hydrophobic, and physical interactions. Using PFOS and PFOA as model long-chain PFAS and PFBS and PFHxA as short-chain surrogates, respectively, MQCGs achieved a complete removal of PFOS and PFOA and over a 99.9% removal of PFBS and PFHxA, each at a low concentration of 500 µg/L in water. Moreover, MQCGs exhibited highly efficient removal of PFAS at environmentally relevant concentrations of 20 µg/L in tap water containing MgSO₄ and NaCl as competing electrolytes, demonstrating the potential of MQCGs as a new class of efficient, selective, and regenerable materials for PFAS sequestration. Full article

This research demonstrates, for the first time, the integration of aero-titania material in sensor devices. An innovative approach for the practical application of aero-titania (aero-TiO₂) materials in photodetectors and the characterization under ultraviolet irradiation was assessed. The fabrication of aero-materials was carried out through the atomic layer deposition (ALD) of titanium dioxide ultrathin layers on a sacrificial network consisting of zinc oxide micro-tetrapods. This process was followed by a selective etching of the sacrificial ZnO template and formation of aero-titania hollow micro-tetrapods. The obtained material has been characterized using UV-Vis spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. The development of photodetectors was achieved through the sequential spin-coating deposition of aero-TiO₂ onto an interdigitated ceramic electrode. The obtained results show that, for high-intensity ultraviolet, the maximum sensitivity was reached for the two-deposited-layer aero-TiO₂ sensor at about 23, since for the low-intensity UV the highest sensitivity was recorded for the one-deposited-layer aero-TiO₂ sensor at about 12. In terms of the responsivity, the highest response was obtained for the one-deposited-layer aero-TiO₂ sensor under low-intensity illumination, reaching about 1.23 × 10⁻⁴ A W⁻¹ cm⁻². Thus, the aero-TiO₂ structure demonstrates the practical viability and application potential of this emerging class of materials in advanced sensing technologies. Full article

The increasing demand for sustainable chemical processes has fostered the development of advanced catalytic systems for biomass valorization. In this work, a series of mono-, bi-, and trimetallic oxides (FeO, FeCuO, FeZnO, and FeCuZnO) were successfully synthesized using MIL-101-based MOFs as sacrificial templates. The obtained materials were thoroughly characterized by N₂ adsorption–desorption, XRD, FTIR, and TEM/STEM-EDX to investigate their structural, morphological, and textural properties. Their catalytic performance was evaluated in the selective oxidation of benzyl alcohol, a lignin-derived platform molecule, into benzaldehyde under microwave irradiation as a sustainable heating strategy. The results demonstrate that MOF-derived oxides exhibit superior activity compared to their parent MOFs, highlighting the beneficial effect of thermal treatment on the exposure of active sites. Among the catalysts, heterometallic oxides showed enhanced performance due to synergistic effects between metals. In particular, FeZnO reached a maximum yield of 62.1% towards benzaldehyde at 150 °C and 30 min, outperforming the monometallic oxide. Recycling tests revealed that FeZnO retained higher overall performance than FeCuO, which suffered from progressive copper leaching. These findings confirm the potential of MOF-derived multimetallic oxides as efficient and reusable heterogeneous catalysts for selective biomass-derived alcohol oxidation. The combination of microwave-assisted processes and the tuneable nature of MOF-derived oxides provides a promising pathway for designing sustainable catalytic systems with industrial relevance. Full article

Aerogels combine ultralow density with high surface area, yet their brittle, open networks preclude tensile deformation and hinder integration into wearable electronics. Here we introduce a prestrain-enabled coaxial architecture that converts a brittle conductive aerogel into a highly stretchable fiber. A porous thermoplastic elastomer (TPE) hollow sheath is wet-spun using a sacrificial lignin template to ensure solvent exchange and robust encapsulation. Conductive polymer-based precursor dispersions are infused into prestretched TPE tubes, frozen, and lyophilized; releasing the prestretch then programs a buckled aerogel core that unfolds during elongation without catastrophic fracture. The resulting TPE-wrapped aerogel fibers exhibit reversible elongation up to 250% while retaining electrical function. At low strains (<60%), resistance changes are small and stable (ΔR/R₀ < 0.04); at larger strains the response remains monotonic and fully recoverable, enabling broad-range sensing. The mechanism is captured by a strain-dependent percolation model in which elastic decompression, contact sliding, and controlled fragmentation/reconnection of the aerogel network govern the signal. This generalizable strategy decouples elasticity from conductivity, establishing a scalable route to ultralight, encapsulated, and skin-compatible aerogel fibers for smart textiles and deformable electronics. Full article

The widespread contamination of aquatic systems by ciprofloxacin (CIP)—a persistent fluoroquinolone antibiotic—poses severe ecological risks due to its antibacterial resistance induction. Conventional sulfate radical-based advanced oxidation processes (SR-AOPs) suffer from inefficient catalyst synthesis, exemplified by low-yield ZIF-67 precursors (typically <25%). To address this, a nitrogen-doped carbon composite Co₃O₄/N@C was synthesized via ammonia-assisted ligand exchange followed by pyrolysis, using N-doped ZIF-67 as a self-sacrificial template. The ammonia incorporation quadrupled precursor yield compared to ammonia-free methods. This catalyst activated peroxydisulfate (PDS) to degrade 95% CIP within 90 min under the optimized conditions (0.5 g/L catalyst, 2 mmol/L PDS, pH 5), representing a 30% enhancement over non-ammonia analogs. Mechanistic studies identified singlet oxygen (¹O₂) as the dominant reactive species, facilitated by N-doped carbon-mediated electron transfer. This strategy overcomes the scalability barrier of MOF-derived catalysts for practical antibiotic wastewater remediation. Full article

Metal–organic frameworks (MOFs) have become a hot topic in various research fields nowadays. And MOF-derived metal oxides prepared by the sacrificial template method have been widely applied as catalysts for pollutant removal. Accordingly, we prepared a series of MOF-derived MnO_x catalysts with diverse morphologies (rod-like, flower-like, slab-like) via the pyrolysis of MOF precursors, and the as-prepared MnO_x catalysts demonstrated superior performance compared to the one prepared using the co-precipitation method. MnO_x-II, with a flower-like structure, exhibited excellent activity for formaldehyde (HCHO) catalytic ozonation at room temperature, reaching complete HCHO conversion at O₃/HCHO of 1.5 and more than 90% CO₂ selectivity at an O₃/HCHO ratio of 2.5. On the basis of various characterization methods, it was clarified that the enhanced catalytic performance of MnO_x-II benefited from its larger BET surface area, abundant oxygen vacancies, better redox ability at lower temperature, and more Lewis acid sites. The H₂O resistance and stability tests were also conducted. Furthermore, DFT calculations substantiated the enhanced adsorption of HCHO and O₃ on oxygen vacancies, while in–situ DRIFTS measurements elucidated the degradation pathway of HCHO during catalytic ozonation through detected intermediates. Full article

Transparent conductive electrodes (TCEs) are essential components in modern optoelectronic devices, including organic light-emitting diodes and solar cells, sensors, and flexible displays. Indium tin oxide has been the dominant material for TCEs due to its high transparency and conductivity. However, its brittleness, high cost, and increasingly limited availability pose significant challenges for electronics. Crack-template (CT)-assisted fabrication has emerged as a promising technique to develop metal mesh-based TCEs with superior mechanical flexibility, high conductivity, and excellent optical transmittance. This technique leverages the spontaneous formation of random and continuous microcrack networks in sacrificial templates, followed by metal deposition (e.g., Cu, Ag, Al, etc.), to produce highly conductive, scalable, and low-cost electrodes. Various crack formation strategies, including controlled drying of polymer suspensions, mechanical strain engineering, and thermal processing, have been explored to tailor electrode properties. Recent studies have demonstrated that crack-templated TCEs can achieve transmittance values exceeding 85% and sheet resistances below 10 Ω/sq, with mesh line widths as low as ~40 nm. Moreover, these electrodes exhibit enhanced stretchability and robustness under mechanical deformation, outperforming ITO in bend and fatigue tests. This review aims to explore recent advancements in CT engineering, highlighting key fabrication methods, performance metrics across different metals and substrates, and presenting examples of its applications in optoelectronic devices. Additionally, it will examine current challenges and future prospects for the widespread adoption of this emerging technology. Full article

Recently, a new class of materials with very high porosity and ultra-lightweight, namely, semiconductor aero-materials, has attracted the attention of many researchers. Semiconductor aero-materials, due to their special properties, can be used in the development of devices applied in biomedical, electronics, optoelectronic, energy conversion and storage, sensors, biosensors, catalysis, automotive, and aeronautic industries. Although aero-materials and aerogels are similar, different methods of obtaining them are used. Aerogels are synthesized from organic, inorganic, or hybrid precursors, the main characteristic being that they are gel-like solids with a high air content (99.9%) in the structure. Thus, three-dimensional (3D) interconnected porous network chains are formed, resulting in light solid-state structures with very high porosity due to the large number of air pores in the network. On the other hand, to obtain aero-materials with controlled properties such as morphology, shape, or the formation of 3D hollow structures, sacrificial templates are used. Thus, sacrificial structures (which can be easily removed) can be obtained depending on the morphology of the 3D structure to be obtained. Therefore, this review paper offers a comprehensive coverage of the synthesis methods of different types of semiconductor aero-materials that use ZnO tetrapod, ZnO(T), as a sacrificial template, related to the present and future perspectives. These ZnO(T) sacrificial substrates offer several advantages, including diverse synthesis processes and easy removal methods that occur simultaneously with the growth of the desired aero-materials. Full article