Advanced Functional Materials Research Articles

High-entropy hexacyanoferrates as robust cathode active materials for sodium storage

In a recent study published in <i>Advanced Functional Materials</i>, Ma and colleagues reported a high-entropy Mn-based hexacyanoferrate of composition Na_x(MnFeNiCuCo)[Fe(CN)₆] for reversible sodium storage, showing improved performance over lower configurational entropy cathode counterparts. Systematic comparisons of the properties of high-, medium-, and low-entropy hexacyanoferrates helped to identify the origin of the enhanced cyclability: entropy-mediated suppression of phase transitions.

From Waste to Wealth: Upcycling Waste Polypropylene/Polyethylene for Thermal Management via Pressure-Induced, Flow-Enhanced Segregated Structurizing with Hexagonal Boron Nitride

The low value of recycled products is the main roadblock for sustainable development of polymers. In this work, waste polypropylene and waste polyethylene were chosen to be recycled for value-added thermal management with the addition of hexagonal boron nitride (hBN). Through specific design of melt flow indexes (MFIs), we proposed a novel pressure-induced, flow-enhanced segregated structurization (PiF-SS) process. The segregated structures were visually confirmed by various microscopies at different scales. The highest in-plane thermal conductivities of ∼7.48 W/mk was obtained for the sample with a low hBN loading of 20 wt %. Ultimately, we evaluated the thermal management performance of all samples with various compositions. In this work, we believe that the concept of combinational utilization of a high-MFI polymer and a low-MFI polymer to perform PiF-SS can not only work for the sustainable reuse of waste polymers but also be used for manufacturing advanced functional materials.

Structural investigations of the Bi2–xSbxTe3–ySey topological insulator

Exotic phases of matter such as topological insulators are a captivating class of advanced functional materials. Key to understanding the behavior of topological insulators is elucidating their structure, but this can be challenging. For example, Bi2–xSbxTe3–ySey crystals have been extensively grown and studied, yet there is still ambiguity in the literature concerning the crystal structure due to the availability of multiple competing candidate structures and inconsistent use of crystallographic terminology, specifically with respect to structures in the trigonal and hexagonal crystal systems. In this work, we investigate the Bi2–xSbxTe3–ySey structure using a variety of techniques including single-crystal and powder X-ray diffraction, electron microscopy, X-ray photoelectron spectroscopy, and X-ray fluorescence. Structure refinement of diffraction data suggests that Bi2–xSbxTe3–ySey belongs to the trigonal crystal system having R3¯m symmetry. X-ray photoelectron spectroscopy analysis supports the refined atomic site occupancies. We present two reasons for the misattribution of Bi2–xSbxTe3–ySey to hexagonal symmetry in former literature. First, improper use or misinterpretation of crystallographic terminology has led to crystal symmetry being incorrectly confused with lattice system, crystal family, or unit cell choice. Second, the presence of defects can produce easily misinterpreted diffraction patterns, and we propose that twinning is the primary source of confusion between trigonal and hexagonal symmetry for BSTS.

Recent Developments of High-Pressure Spark Plasma Sintering: An Overview of Current Applications, Challenges and Future Directions.

Spark plasma sintering (SPS), also called pulsed electric current sintering (PECS) or field-assisted sintering technique (FAST) is a technique for sintering powder under moderate uniaxial pressure (max. 0.15 GPa) and high temperature (up to 2500 °C). It has been widely used over the last few years as it can achieve full densification of ceramic or metal powders with lower sintering temperature and shorter processing time compared to conventional processes, opening up new possibilities for nanomaterials densification. More recently, new frontiers of opportunities are emerging by coupling SPS with high pressure (up to ~10 GPa). A vast exciting field of academic research is now using high-pressure SPS (HP-SPS) in order to play with various parameters of sintering, like grain growth, structural stability and chemical reactivity, allowing the full densification of metastable or hard-to-sinter materials. This review summarizes the various benefits of HP-SPS for the sintering of many classes of advanced functional materials. It presents the latest research findings on various HP-SPS technologies with particular emphasis on their associated metrologies and their main outstanding results obtained. Finally, in the last section, this review lists some perspectives regarding the current challenges and future directions in which the HP-SPS field may have great breakthroughs in the coming years.

Perspective on machine learning in energy material discovery

Perspective on machine learning in energy material discovery

Cellulose-Chitosan Functional Biocomposites.

Here, we present a detailed review of recent research and achievements in the field of combining two extremely important polysaccharides; namely, cellulose and chitosan. The most important properties of the two polysaccharides are outlined, giving rise to the interest in their combination. We present various structures and forms of composite materials that have been developed recently. Thus, aerogels, hydrogels, films, foams, membranes, fibres, and nanofibres are discussed, alongside the main techniques for their fabrication, such as coextrusion, co-casting, electrospinning, coating, and adsorption. It is shown that the combination of bacterial cellulose with chitosan has recently gained increasing attention. This is particularly attractive, because both are representative of a biopolymer that is biodegradable and friendly to humans and the environment. The rising standard of living and growing environmental awareness are the driving forces for the development of these materials. In this review, we have shown that the field of combining these two extraordinary polysaccharides is an inexhaustible source of ideas and opportunities for the development of advanced functional materials.

Internal wettability investigation of mesoporous silica materials by ellipsometric porosimetry

Silica-based mesoporous films have been widely applied in the fabrication of advanced functional materials, such as anti-reflective coatings, bio-, and chemical sensing devices, due to their unique properties, e.g., high surface area, controlled porosity, and the ease and tailorability of their synthesis. Precise knowledge of their pore architecture is crucial, highlighting the need for accurate characterization tools. In this sense, ellipsometric porosimetry represents a powerful and versatile characterization platform, providing access to reliable information about total porosity, pore size, pore size dispersity, mechanical properties (Young's modulus) and surface area of a great variety of mesoporous thin films.While the underlying framework of modeling capillary condensation via the Kelvin equation is well established, one descriptor, the internal wettability of mesoporous architectures remains a challenging variable for reliable material characterization. Wetting on the nanoscale cannot be observed via the traditional drop-shape method, while approximating internal wetting by the macroscopic property can be inaccurate as the two wetting behaviors do not necessarily correlate. Herein, we present a method based on vacuum ellipsometric porosimetry for the determination of the internal contact angle of functionalized mesoporous silica thin films. Tuning of the surface energy for a known mesoporous architecture by methyl-functionalization enabled us to relate differences in the pore filling for various adsorptives (water, methanol, toluene, cyclohexane) to their internal contact angles. Our study serves as a guide for generalized internal contact angle determination suitable for a wide range of organic adsorptives and mesoporous sorbent materials.

Gel Electrolytes for Electrochemical Actuators and Sensors Applications.

Advanced functional materials, especially gel electrolytes, play a very important role in the preparation of electrochemical actuators and sensors, and have received extensive attention. In this review, a general classification of gel electrolytes is firstly introduced according to the type of medium. Then, the research progress of gel electrolytes with different types used to fabricate electrochemical actuators is summarized. Next, the current research progress of gel electrolytes used in different types of electrochemical sensors, including strain sensors, stress sensors, and gas sensors is introduced. Finally, the future challenges and development prospects of electrochemical actuators and sensors based on gel electrolytes are discussed. The huge application prospects of gel electrolyte are worthy of further focusing by researchers, which will have an indispensable impact on human life and development.

Recent Advances in Flexible Ultrasonic Transducers: From Materials Optimization to Imaging Applications.

Ultrasonic (US) transducers have been widely used in the field of ultrasonic and photoacoustic imaging system in recent years, to convert acoustic and electrical signals into each other. As the core part of imaging systems, US transducers have been extensively studied and achieved remarkable progress recently. Imaging systems employing conventional rigid US transducers impose certain constraints, such as not being able to conform to complex surfaces and comfortably come into contact with skin and the sample, and meet the applications of continuous monitoring and diagnosis. To overcome these drawbacks, significant effort has been made in transforming the rigid US transducers to become flexible and wearable. Flexible US transducers ensure self-alignment to complex surfaces and maximize the transferred US energy, resulting in high quality detection performance. The advancement in flexible US transducers has further extended the application range of imaging systems. This review is intended to summarize the most recent advances in flexible US transducers, including advanced functional materials optimization, representative US transducers designs and practical applications in imaging systems. Additionally, the potential challenges and future directions of the development of flexible US transducers are also discussed.

Advanced functional materials and manufacturing processes

Guest Editors Jessica Winter, Jawwad Darr, and John Wang introduce the Materials Advances themed collection on advanced functional materials and manufacturing processes.

Peptide-triggered self-assembly of collagen mimetic peptides into nanospheres by electrostatic interaction and π-π stacking.

Collagen is the most abundant protein in various connective tissues, providing mechanical integrity as well as regulating cellular activities. Self-assembled peptides have been extensively explored to develop collagen mimetic materials, due to their attractive features such as easy synthesis, selective sequences and low immunogenicity. Metal ion-triggered self-assembly of collagen mimetic peptides has recently received increasing interests, since the addition of external stimuli offers programmable control of the self-assembly process. We have for the first time reported a peptide-stimulated self-assembly of collagen mimetic peptides into nanospheres by electrostatic interaction and π-π stacking. We have accidentally discovered that FAM-modified positively-charged triple helical peptide FAM-PRG was highly soluble, while the addition of a single-stranded negatively-charged peptide EOG-10 efficiently drove its self-assembly into well-ordered spherical nanomaterials. Peptide EOG-10 has been shown to mediate similar self-assembly of TPE-modified triple-helical peptide TPE-PRG into luminescent exquisite nanospheres, consistently demonstrating the robustness of this peptide-triggered strategy. Fluorescence monitoring of the interaction of EOG-10 and TPE-PRG at different ratios indicated that EOG-10 specifically binds to TPE-PRG to form a 3 : 1 complex. High salt concentration was shown to inhibit the self-assembly of TPE-PRG with EOG-10, suggesting that their self-assembly was controlled by electrostatic interaction. The self-assembly of TPE-PRG with EOG-10 has been further revealed to require the exact lengths of both peptides as well as complementary sequences without mutations, indicating a pairwise "side-by-side" binding mode. Notably, the identity of the N-terminal residues of X-PRG has been found to play a determinant role in the self-assembly, while non-aromatic residues lost the self-assembling capability, suggesting that π-π stacking and electrostatic interactions collectively modulate the self-assembly of X-PRG and EOG-10. To conclude, we have developed a highly biocompatible and programmably controlled peptide-triggered self-assembly approach to create novel collagen mimetic nanomaterials, which may have great potential in advanced functional materials.

Stimuli-cleavable moiety enabled vinyl polymer degradation and emerging applications

This review delves into degradable vinyl polymers with stimuli-cleavable moieties, their chemistry, mechanisms, and applications in environmental remediation, drug delivery, advanced functional materials, and surface modification.

A novel systematic analysis of the network of H2020 project participants in Road Transport research topics

The paper analyses the properties of the networks constructed by the projects funded by Horizon2020 in four research areas, namely internal combustion engines for hybrid electric vehicles, batteries for electric vehicles, advanced functional materials, and power electronics for automotive applications. Social Network Analysis is used to determine the network properties and the centrality measures of the nodes to identify the most important actors. The analysis is complemented with publication and patent data to investigate if participation in Horizon2020 projects influences research and innovation performance of higher education and research organisations. The results indicate that projects are formed by the same core of key partners, located in or around the main centres of automotive manufacturing in Europe, with the exception of the former Eastern European countries.

AROMA: Anionic ring-opening monomer addition of allyl glycidyl ether to methoxy poly(ethylene glycol) for the synthesis of sequence-controlled polymers

Abstract Herein, a new method to synthesise epoxide-based sequence-controlled polymers via anionic ring-opening monomer addition, a form of anionic ring-opening polymerisation, is presented. This technique allows in combination with post-polymerisation modification (PPM) reactions for the successful preparation of modified mPEG-b-oligo(allyl glycidyl ether) featuring the incorporation of one repeating unit on average at a time. Due to the possible introduction of a vast variety of molecules to the polymeric system via PPM reactions, a multitude of advanced functional polymeric materials can be generated. This, in combination with the chain extension reactions, allows for the synthesis of well-controlled and programmable architectures with particular properties. The structure of the sequence-controlled polymer was confirmed via 1H NMR spectroscopy, size exclusion chromatography, attenuated total reflection Fourier-transform infrared spectroscopy, and differential scanning calorimetry.

Nanostructured supramolecular networks from self-assembled diamondoid molecules under ultracold conditions.

Diamondoid molecules and their derivatives have attracted attention as fascinating building blocks for advanced functional materials. Depending on the balance between hydrogen bonds and London dispersion interactions, they can self-organize in different cluster structures with functional groups tailored for various applications. Here, we present a new approach to supramolecular aggregation where self-assembly of diamondoid acids and alcohols in the ultracold environment of superfluid helium nanodroplets (HNDs) was analyzed by a combination of time-of-flight mass spectrometry and computational tools. Experimentally observed magic numbers of the assembled cluster sizes were successfully identified and computed cluster structures gave valuable insights into a different conglomeration mode when compared to previously explored less-polar diamondoid derivatives. We have confirmed that functional groups acting as good hydrogen bond donors completely take over the self-organization process, resulting in fascinating pair-wise or cyclic supramolecular assemblies. Particularly noteworthy is that mono- and bis-substituted diamondoid derivatives of both series engage in completely different modes of action, which is reflected in differing non-covalent cluster geometries. Additionally, formed cyclic clusters with a polar cavity in the center and a non-polar diamondoid outer layer can be of high interest in porous material design and provide insights into the structural requirements needed to produce bulk materials with desired properties.

A review on electrospun polyvinylpyrrolidone-derived carbon composite nanofibers as advanced functional materials for energy storage applications and beyond

Polyvinylpyrrolidone (PVP) is soluble in many solvents and compatible with various precursors. PVP-derived carbon composite nanofibers have a porous structure of unique properties and wide potential application in batteries, catalysts, and beyond.

Recent progress in emulsion gels: from fundamentals to applications.

Emulsion gels, also known as gelled emulsions or emulgels, have garnered great attention both in fundamental research and practical applications due to their superior stability, tunable morphology and microstructure, and promising mechanical and functional properties. From an application perspective, attention in this area has been, historically, mainly focused on food industries, e.g., engineering emulsion gels as fat substitutes or delivery systems for bioactive food ingredients. However, a growing body of studies has, in recent years, begun to demonstrate the full potential of emulsion gels as soft templates for designing advanced functional materials widely applied in a variety of fields, spanning chemical engineering, pharmaceutics, and materials science. Herein, a concise and comprehensive overview of emulsion gels is presented, from fundamentals to applications, highlighting significant recent progress and open questions, to scout for and deepen their potential applications in more fields.

Homoleptic complexes of isocyano- and diisocyanobiazulenes with a 12-electron, ligand-based redox capacity.

Oligo- and polyazulenes are attractive π-conjugated building blocks in designing advanced functional materials. Herein, we demonstrate that anchoring one or both isocyanide termini of the redox non-innocent 2,2'-diisocyano-6,6'-biazulenic π-linker (1) to the redox-active [Cr(CO)5] moiety provided a convenient intramolecular redox reference for unambiguously establishing that the 6,6'-biazulenic scaffold undergoes a reversible one-step 2e- reduction governed by reduction potential compression/inversion. Treatment of bis(η6-naphthalene)chromium(0) with six equiv. of 2-isocyano-1,1',3,3'-tetraethoxycarbonyl-6,6'-biazulene (6) or [(OC)5Cr(η1-2,2'-diisocyano-1,1',3,3'-tetraethoxycarbonyl-6,6'-biazulene)] (11) afforded homoleptic Cr(0) complexes 13 and 14 with a 12e- (per molecule) ligand-based reduction capacity at mild E1/2 of -1.29 V and -1.15 V vs. Cp2Fe0/+, respectively. The overall reversible redox capacity varies from 15e- for the mononuclear complex 13 to 21e- for the heptanuclear complex 14. The latter "nanocomplex" has a diameter of ca. 5 nm and features seven Cr(0) centers interlinked with six 2,2'-diisocyano-6,6'-biazulenic bridges. The X-ray structure of [(OC)5Cr(2-isocyano-1,1',3,3'-tetraethoxycarbonyl-6,6'-biazulene)] (7) indicated a 43.5° interplanar angle between the two azulenic moieties. Self-assembly of 11 on a Au(111) substrate afforded an organometallic monolayer film of 11 featuring approximately upright orientation of the 2,2'-diisocyano-6,6'-biazulenic linkers, as evidenced by ellipsometric measurements and the RAIR signature of the C4v-symmetric [(-NC)Cr(CO)5] infrared reporter within 11. Remarkably, comparing the FTIR spectrum of 11 in solution with the RAIR spectrum of 11 adsorbed on Au(111) suggested electronic coupling at a ca. 2 nm distance between the Cr(0) and Au atoms linked by the 2,2'-diisocyano-6,6'-biazulene bridge.

Multi-objective optimization of actuation waveform for high-precision drop-on-demand inkjet printing

High-precision drop-on-demand (DOD) inkjet printing has been considered as one of the promising technologies for the fabrication of advanced functional materials. For a DOD printer, high-precision dispensing techniques for achieving satellite-free smaller droplets have long been desired for patterning thin-film structures. Optimization of an actuation waveform driving a DOD inkjet printer is one of the most versatile and effective strategies to obtain high-precision droplets. Considering the complexity of physics behind the droplet dispensing mechanisms and the large degrees of freedom in the applied waveforms, conventional trial-and-error approaches are not effective for searching the optimal waveform. The present study considers the inlet velocity of a liquid chamber located upstream of a dispensing nozzle as a control variable and aims to develop an automated waveform tuning framework to optimize its waveform using a sample-efficient Bayesian optimization (BO) algorithm. First, the droplet dispensing dynamics are numerically reproduced by using an open-source OpenFOAM solver, interFoam, and the results are passed on to another code based on PyFoam. Then, the parameters characterizing the actuation waveform driving a DOD printer are determined by the BO algorithm so as to maximize a prescribed multi-objective function expressed as the sum of two factors, i.e., the size of a primary droplet and the presence of satellite droplets. The results show that the present BO algorithm can successfully find high-precision dispensing waveforms within 150 simulations. Specifically, satellite droplets can be effectively eliminated and the droplet diameter can be significantly reduced to 24.9% of the nozzle diameter by applying the optimal waveform. Moreover, the prediction using the Gaussian process regression suggests that the size of the primal droplet is highly correlated with the period of a waveform. Finally, the criterion for achieving single-droplet dispensing is proposed based on the energy budget analysis.

Graft onto approaches for nanocellulose-based advanced functional materials.

The resurgence of cellulose as nano-dimensional 'nanocellulose' has unlocked a sustainable bioeconomy for the development of advanced functional biomaterials. Bestowed with multifunctional attributes, such as renewability and abundance of its source, biodegradability, biocompatibility, superior mechanical, optical, and rheological properties, tunable self-assembly and surface chemistry, nanocellulose presents exclusive opportunities for a wide range of novel applications. However, to alleviate its intrinsic hydrophilicity-related constraints surface functionalization is inevitably needed to foster various targeted applications. The abundant surface hydroxyl groups on nanocellulose offer opportunities for grafting small molecules or macromolecular entities using either a 'graft onto' or 'graft from' approach, resulting in materials with distinctive functionalities. Most of the reviews published to date extensively discussed 'graft from' modification approaches, however 'graft onto' approaches are not well discussed. Hence, this review aims to provide a comprehensive summary of 'graft onto' approaches. Furthermore, insight into some of the recently emerging applications of this grafted nanocellulose including advanced nanocomposite formulation, stimuli-responsive materials, bioimaging, sensing, biomedicine, packaging, and wastewater treatment has also been reviewed.