Tunable Materials Research Articles

Calcium phosphate graphene with tailorable phosphate and oxygen content for increased osteogenic activity

The treatment of critical bone injuries using autografts and metallic hardware, though effective, carries drawbacks yet to be addressed by modern interventions. One way that researchers have sought to avoid these complications is using bioresorbable synthetic grafts. Ideally, these materials possess mechanical properties like that of bone and support the site of injury until absorbed and replaced by native bone. In this work we seek to continue the work of optimizing the synthesis of one synthetic graft candidate, calcium phosphate graphene (CaPG). CaPG is a functional graphenic material (FGM) made using the Arbuzov reaction to covalently seed polyphosphates on the graphenic backbone. This material releases calcium and phosphate ions and has been shown to induce osteogenesis. Herein, we investigate reaction conditions and demonstrate the ability to tailor the functionalization of CaPG. The differences in these properties were found to affect mechanical properties, ion elution, as well as calcium deposition of stem cells when measured via Alizarin Red S (ARS). These results continue to demonstrate the potential of CaPG scaffolds as tunable materials to promote bone regeneration.

Photocurable vitrimers with malleable and self-healing trade-off enabled by manipulating dynamic boronic ester bonds

Although numerous strategies refer to dynamic covalent bond exchanges of small molecules for self-repairing thermosets, it remains a critical challenge to be able to jointly tune the malleability and dynamic properties of photocurable materials via extending dynamical small molecule bridging chains with tunable kinetic features. Herein, we successfully synthesized two typical diboronic ester molecules (diboronic ester dithiol/diacid) with variable dioxaborolane metathesis kinetics, which acted as dynamical interlinking segments constructing simple hydrogenated bisphenol A (HBA) epoxy backbone to achieve dynamically cross-linking feature. Subsequently, the acrylate- and anhydride-modified HBA vitrimers bearing diboronic ester-extending segment variants and photocuring traits are successfully synthesized by a one-pot reaction. Consequently, it is demonstrated that the embedded amounts of dynamic diboronic ester bonds in the backbone play a key role in the photopolymerization rate of photocurable vitrimers. The photopolymerization rate decreases significantly as more diboronic ester segments. Moreover, the diboronic ester dithiol-mediated photocurable vitrimer (HBA-S) exhibits enhanced malleability (strain at break of 26.6 %), desirable photo-crosslinked network, and accelerated thermal-triggered self-healing ability (scratch self-healing efficiency of closing to 100 % at 150 °C), compared to those of the diboronic ester diacid-mediated vitrimer (HBA-O) under identical conditions. This work validates the probability of transferring the dioxaborolane metathesis of small molecules to dynamic properties of bulk UV-curing materials, which provides valuable guidance for the rational design and fabrication of tunable dynamic photocurable materials.

Perspective: Entropy-stabilized oxide memristors

A memristor array has emerged as a potential computing hardware for artificial intelligence (AI). It has an inherent memory effect that allows information storage in the form of easily programmable electrical conductance, making it suitable for efficient data processing without shuttling of data between the processor and memory. To realize its full potential for AI applications, fine-tuning of internal device dynamics is required to implement a network system that employs dynamic functions. Here, we provide a perspective on multicationic entropy-stabilized oxides as a widely tunable materials system for memristor applications. We highlight the potential for efficient data processing in machine learning tasks enabled by the implementation of “task specific” neural networks that derive from this material tunability.

Deep Blue CsPbBr3 Quantum Wires with Tailored Shapes.

Low-dimension metal halide perovskites are attractive for bandgap tunable optoelectronic materials. Among them, 1-D CsPbBr3 quantum wires (QWs) are emerging as promising deep-blue luminescent material. However, the growth dynamics of 1-D perovskite QWs are intricate, making the study and control of 1-D QWs highly challenging. In this study, a strategy for controlling both the length and width of the CsPbBr3 QWs was realized. The temperature-dependent isotropic growth mechanism was revealed and employed as the main tool for the oriented growth of 1-D CsPbBr3 QWs for various aspect ratios. Our results pave the way for the controlled synthesis of ultrasmall perovskite nanocrystals.

Magnetic Circularly Polarized Luminescence with Heterometallic Molecular Cluster‐Aggregates

AbstractMagnetic circularly polarized luminescence (MCPL) is a technique based on the differential emission of left and right circularly polarized light induced by a magnetic field. This technique is the emission counterpart of to the widely explored magnetic circular dichroism. In this work, the first demonstration of MCPL is presented in heterometallic lanthanide(III) systems by using two molecular cluster aggregates, {Eu1Tb19} and {Eu3Tb17}. The results presented here indicate the potential that MCPL holds for obtaining highly tuned magneto‐optical materials for various applications, such as anti‐counterfeiting materials. Additionally, the findings suggest that magnetic interactions between the ions modulate the dissymmetry factor, opening the possibility of the development of highly tunable MCPL materials.

Achieving Tunable Mechanoluminescence in CaZnOS:Tb3+, Sm3+ for Multicolor Stress Sensing.

Mechanoluminescent (ML) materials can exhibit visible-to-near-infrared mechanoluminescence when responding to the fracture or deformation of a solid under mechanical stimulation. Transforming mechanical energy into light demonstrates promising applications in terms of visual mechanical sensing. In this work, we synthesized the phosphor CaZnOS:Tb3+, Sm3+, which exhibited intense and tunable multicolor mechanoluminescence without pre-irradiation. Intense green ML materials were obtained by doping Tb3+ with different concentrations. Tunable multicolor mechanoluminescence (such as green, yellow-green, and orange-red) could be realized by combining green emission (about 542 nm), attributed to Tb3+, and red emission (about 600 nm) generated from the Sm3+ in the CaZnOS substrate. The tunable multicolor ML materials CaZnOS:Tb3+, Sm3+ exhibited intense luminance and recoverable mechanoluminescence when responding to mechanical stimulation. Benefiting from the excellent ML performance and multicolor tunability in CaZnOS:Tb3+, Sm3+, we mixed the phosphor with PDMS and a curing agent to explore its practical application. An application for visual mechanical sensing was designed for handwriting identification. By taking a time-lapsed shot while writing, we easily obtained images of the writer's handwriting. The images of the ML intensity were acquired by using specific software to transform the shooting data. We could easily distinguish people's handwriting through analyzing the different ML performances.

Fuel‐Driven Dynamic Combinatorial Peptide Libraries

Dynamic combinatorial chemistry (DCC) creates libraries of molecules that are constantly interchanging in a dynamic combinatorial library. When a library member self‐assembles, it can displace the equilibria, leading to emergent phenomena like its selection or even its replication. However, such dynamic combinatorial libraries typically operate in or close to equilibrium. This work introduces a new dynamic combinatorial chemistry fueled by a catalytic reaction cycle that forms transient, out‐of‐equilibrium peptide‐based macrocycles. The products in this library exist out of equilibrium at the expense of fuel and are thus regulated by kinetics and thermodynamics. By creating a chemically fueled dynamic combinatorial library with the vast structural space of amino acids, we explored the liquid‐liquid phase separation behavior of the library members. The study advances DCCs by showing that peptide structures can be engineered to control the dynamic library's behavior. The work paves the way for creating novel, tunable material systems that exhibit emergent behavior reminiscent of biological systems. These findings have implications for the development of new materials and for understanding life's chemistry.

Charge Redistribution in High-Entropy Perovskite Oxide Porous Nanotubes Boosts Nitrate Electroreduction to Ammonia.

High-entropy perovskite oxides are promising materials in the field of electrocatalysis due to their advantages such as large spatial composition regulation, entropy effects, and tunable material properties. However, the preparation of high-entropy perovskite oxides with stable and controllable structures still remains challenging. Herein, we fabricated a series of high-entropy perovskite oxide porous nanotubes (PNTs) by electrospinning as efficient electrocatalysts for the nitrate reduction reaction (NO3RR). We further revealed that the different diffusion and decomposition behaviors of metal ions and polymers during the calcination process are the key to the formation of high-entropy perovskite oxide PNTs. Especially, LaSrNiCoMnFeCuO3 PNTs show excellent performance of the NO3RR, achieving the maximum NH3 Faradaic efficiency of almost 100%, yield rate of 1657.5 μg h-1 mgcat.-1, and durable stability after successive cycling, being one of the best electrocatalysts for the NO3RR. The mechanism studies show that the charge redistribution induced by the multisite synergistic effect and abundant unsaturated sites in the high-entropy perovskite oxide PNTs favors the adsorption of NO3- and key intermediates and reduces the catalytic energy barrier, thus further achieving high NO3- conversion efficiency.

Flash sintering of tunable dielectric Ba0.6Sr0.4TiO3 electroceramics

Ba(1-x)SrxTiO3 (BST) is a crucial dielectric material in tunable devices for modern wireless communication technologies, owing to high dielectric tunability and low dielectric loss. However, the conventional processing of BST ceramics requires a high sintering temperature of about 1350 ºC. In this work, we demonstrate the feasibility of using Flash sintering (FS) and corresponding maps to process Ba0.6Sr0.4TiO3 ceramics, resulting in a 350 ºC decrease in sintering temperature and 7 h reduction in sintering process time. The Flash-sintered BST exhibits a finer grain microstructure, lower dielectric loss, and significantly higher K-factor (figure of merit for tunability) when compared to conventionally sintered BST, unequivocally meeting the application criteria for tunable materials. Our findings highlight the effectiveness of FS as an alternative method for the rapid sintering of BST, while also opening up possibilities for further research into more efficient sintering processes for electroceramics.

ATO and Cs0·33WO3 loaded bilayer nanofiber membrane doped polymer dispersed liquid crystals for infrared shielding

Liquid crystals possess a wide range of applications in modulating infrared (IR) light and have drawn great interest especially in near-infrared shielding and passive radiative cooling. Here, a composite structure containing polymer dispersed liquid crystals (PDLC) with antimony doped tin oxide and cesium tungsten oxide loaded bilayer nanofiber membranes with IR shielding properties is proposed. The composite film and the blank liquid crystal cell are irradiated simultaneously under IR light, and the temperature detector shows that the average temperature drop of the PDLC composite film in the scattered state and the fully transparent state over the blank sample are 6.8 °C and 4.1 °C, respectively. More importantly, the dynamic IR shielding properties of the composite films are demonstrated by patterning the nanofiber films. In addition, this organic/inorganic hybrid PDLC system not only modulates IR light, but also exhibits excellent electro-optical properties, aging resistance, flexural stability (1000 cycles), and tensile resistance. The composite film combines ease of preparation with compatibility for industrial-scale roll-to-roll or continuous manufacturing processes, highlighting the great potential of PDLC for applications in tunable optical heat transport materials.

Compositional effects of hybrid MoS2–GO active layer on the performance of unipolar, low-power and multistate RRAM device

Currently, 2D nanomaterials-based resistive random access memory (RRAMs) are explored on account of their tunable material properties enabling fabrication of low power and flexible RRAM devices. In this work, hybrid MoS2–GO based active layer RRAM devices are investigated. A facile hydrothermal co-synthesis approach is used to obtain the hybrid materials and a cost-effective spin coating method adopted for the fabrication of Ag/MoS2–GO/ITO RRAM devices. The performance of the fabricated hybrid active layer RRAM device is analysed with respect to change in material properties of the synthesized hybrid material. The progressive addition of 0.5, 1.5, 2.5 and 4.5 weight % of GO to MoS2, results in a hybrid active layer with higher intermolecular interaction, in the case of Ag/MoS2–GO4.5/ITO RRAM device, resulting in a unipolar resistive switching RRAM behavior with low SET voltage of 1.37 V and high I on/I off of 200 with multilevel resistance states. A space charge limited conduction mechanism is obtained during switching, which may be attributed to the trap states present due to functional groups of GO. The increased number of conduction pathways on account of both Ag+ ions and oxygen vacancies (Vo 2+), participating in the formation of conducting filament, results in higher I on/I off. This is the first report of unipolar Ag/MoS2–GO/ITO RRAM devices, which are particularly important in realizing high density crossbar memories for neuromorphic and in-memory computing as well as enabling flexible 2D nanomaterials-based memristor applications.

Dynamically Tunable Half‐Ring Fano Resonator Based on Black Phosphorus

A tunable material black phosphorus (BP) terahertz (THz) half‐ring Fano resonator is proposed, exhibiting enhanced sensitivity, tunable frequency parameters, and the flexible sensing range. A half‐ring is positioned above the main channel, while a groove is excavated beneath it to produce the Fano resonance. The discrete mode of the half‐ring is coupled with the continuous mode of the groove, leading to a significantly enhanced sensitivity. This sensor can pick up subtle changes in the surrounding environment. Additionally, the incorporation of BP into the half‐ring positioned above the channel enables the flexible adjustment of the Fano resonator's resonant frequency. This adjustment is achieved through the manipulation of the electron doping concentration of the BP material. At the third‐order resonance around 5.81 THz, the frequency shift margin can reach 160 GHz. Adjusting the structural parameters of the Fano resonator, such as the radius of its outer ring, the distance of this ring to the main channel, and the groove's height, significantly affects its transmission spectrum. The Fano resonator demonstrates its considerable potential for applications in the field of integrated electronics. It not only provides an innovative design perspective, but also lays the foundation for the study of THz systems.

How Depletion Layers Govern the Dynamic Plasmonic Response of In-Doped CdO Nanocrystals.

Doped metal oxide nanocrystals exhibit a localized surface plasmon resonance that is widely tunable across the mid- to near-infrared region, making them useful for applications in optoelectronics, sensing, and photocatalysis. Surface states pin the Fermi level and induce a surface depletion layer that hinders conductivity and refractive index sensing but can be advantageous for optical modulation. Several strategies have been developed to both synthetically and postsynthetically tailor the depletion layer toward particular applications; however, this understanding has primarily been advanced in Sn-doped In2O3 (ITO) nanocrystals, leaving open questions about generalizing to other doped metal oxides. Here, we quantitatively analyze the depletion layer in In-doped CdO (ICO) nanocrystals, which is shown to have an intrinsically wide depletion layer that leads to broad plasmonic modulation via postsynthetic chemical reduction and ligand exchange. Leveraging these insights, we applied depletion layer tuning to enhance the inherently weak plasmonic coupling in ICO nanocrystal superlattices. Our results demonstrate how an electronic band structure dictates the radial distribution of electrons and governs the response to postsynthetic modulation, enabling the design of tunable and responsive plasmonic materials.

Switchable Dual Circularly Polarized Luminescence in Through-Space Conjugated Chiral Foldamers.

Organic materials with switchable dual circularly polarized luminescence (CPL) are highly desired because they can not only directly radiate tunable circularly polarized light themselves but also induce CPL for guests by providing a chiral environment in self-assembled structures or serving as the hosts for energy transfer systems. However, most organic molecules only exhibit single CPL and it remains challenging to develop organic molecules with dual CPL. Herein, novel through-space conjugated chiral foldamers are constructed by attaching two biphenyl arms to the 9,10-positions of phenanthrene, and switchable dual CPL with opposite signs at different emission wavelengths are successfully realized in the foldamers containing high-polarizability substitutes (cyano, methylthiol and methylsulfonyl). The combined experimental and computational results demonstrate that the intramolecular through-space conjugation has significant contributions to stabilizing the folded conformations. Upon photoexcitation in high-polar solvents, strong interactions between the biphenyl arms substituted with cyano, methylthio or methylsulfonyl and the polar environment induce conformation transformation for the foldamers, resulting in two transformable secondary structures of opposite chirality, accounting for the dual CPL with opposite signs. These findings highlight the important influence of the secondary structures on the chiroptical property of the foldamers and pave a new avenue towards efficient and tunable dual CPL materials.

Switchable Dual Circularly Polarized Luminescence in Through‐Space Conjugated Chiral Foldamers

AbstractOrganic materials with switchable dual circularly polarized luminescence (CPL) are highly desired because they can not only directly radiate tunable circularly polarized light themselves but also induce CPL for guests by providing a chiral environment in self‐assembled structures or serving as the hosts for energy transfer systems. However, most organic molecules only exhibit single CPL and it remains challenging to develop organic molecules with dual CPL. Herein, novel through‐space conjugated chiral foldamers are constructed by attaching two biphenyl arms to the 9,10‐positions of phenanthrene, and switchable dual CPL with opposite signs at different emission wavelengths are successfully realized in the foldamers containing high‐polarizability substitutes (cyano, methylthiol and methylsulfonyl). The combined experimental and computational results demonstrate that the intramolecular through‐space conjugation has significant contributions to stabilizing the folded conformations. Upon photoexcitation in high‐polar solvents, strong interactions between the biphenyl arms substituted with cyano, methylthio or methylsulfonyl and the polar environment induce conformation transformation for the foldamers, resulting in two transformable secondary structures of opposite chirality, accounting for the dual CPL with opposite signs. These findings highlight the important influence of the secondary structures on the chiroptical property of the foldamers and pave a new avenue towards efficient and tunable dual CPL materials.

Antibacterial Hydrogel Adhesives Based on Bifunctional Telechelic Dendritic-Linear-Dendritic Block Copolymers.

Antibiotic-resistant pathogens have been declared by the WHO as one of the major public health threats facing humanity. For that reason, there is an urgent need for materials with inherent antibacterial activity able to replace the use of antibiotics, and in this context, hydrogels have emerged as a promising strategy. Herein, we introduce the next generation of cationic hydrogels with antibacterial activity and high versatility that can be cured on demand in less than 20 s using thiol-ene click chemistry (TEC) in aqueous conditions. The approach capitalizes on a two-component system: (i) telechelic polyester-based dendritic-linear-dendritic (DLDs) block copolymers of different generations heterofunctionalized with allyl and ammonium groups, as well as (ii) polyethylene glycol (PEG) cross-linkers functionalized with thiol groups. These hydrogels resulted in highly tunable materials where the antibacterial performance can be adjusted by modifying the cross-linking density. Off-stoichiometric hydrogels showed narrow antibacterial activity directed toward Gram-negative bacteria. The presence of pending allyls opens up many possibilities for functionalization with biologically interesting molecules. As a proof-of-concept, hydrophilic cysteamine hydrochloride as well as N-hexyl-4-mercaptobutanamide, as an example of a thiol with a hydrophobic alkyl chain, generated three-component networks. In the case of cysteamine derivatives, a broader antibacterial activity was noted than the two-component networks, inhibiting the growth of Gram-positive bacteria. Additionally, these systems presented high versatility, with storage modulus values ranging from 270 to 7024 Pa and different stability profiles ranging from 1 to 56 days in swelling experiments. Good biocompatibility toward skin cells as well as strong adhesion to multiple surfaces place these hydrogels as interesting alternatives to conventional antibiotics.

Metal Ion Responsive Luminescent Bio-Templated Co-Assemblies: Label-Free Detection of Multi-Metal Ions in Aqueous Media.

Recently, anionic bio-templates have emerged as promising platforms for designing dynamic and stimuli-responsive chromophoric assemblies capable of light harvesting in aqueous media thereby mimicking natural photosynthesis. Here, we present multi-metal ion-responsive luminescent co-assemblies between cationic pyrene-imidazolium amphiphile and anionic bio-templates (ATP, heparin, and DNA) in aqueous media. The anionic bio-templates enhance Förster resonance energy transfer (FRET) in the co-assemblies, with pyrene serving as an excellent donor for generating tunable multi-luminescent materials with embedded acceptor dyes. However, a significant loss in energy transfer towards acceptor dyes was observed in the presence of various metal ions, attributed to excimeric emission quenching facilitated by electron transfer between the pyrene chromophore and metal ions. Interestingly, detailed studies revealed that only ATP-based co-assemblies exhibited quenching phenomena in the presence of metal ions, contrasting with heparin and ctDNA co-assemblies. Additionally, label-free detection of multi-metal ions in aqueous environments, such as Fe2+, Fe3+, and Cu2+ ions, was successfully achieved with lower detection limits of 0.01 μM (3 ppb), 0.12 μM (30 ppb), and 0.58 μM (150 ppb) respectively. These co-assemblies hold significant promise for practical applications in environmental and biomedical sensing, enabling sensitive monitoring of metal ion concentrations.

Tunable dye adsorbing materials from crab and shrimp waste shells for water remediation

Crab and shrimp shells are waste byproducts from shellfish farming and processing. In this study, we demonstrated that it is possible to obtain individual shell components either separately or in combinations. These diverse materials were composed of calcium carbonate and organic molecules inter- and intra-mineral, calcium carbonate and organic molecules intra-mineral, organic molecules such as chitin and proteins, only calcium carbonate, and only chitin. These substrates were tested for the adsorption of Methylene Blue and Eosin dyes. The goal is to demonstrate that the organic dye adsorption capacity can be modified by controlling the degree of deconstruction of the starting material. The best adsorption for the positively charged Methylene Blue was achieved on the chitin-calcium carbonate substrates, while the negatively charged Eosin adsorbed best on the chitin substrate. In conclusion, this research demonstrates that it is possible to obtain different materials by deconstructing the shells from crabs and shrimps at various levels reducing the generation of additional wastes. Moreover, these materials exhibit features that are related to the original material and possess new properties that can be also exploited in other fields like material sciences.

Structure property correlation of (1-x)MgTiO3 - xSrTiO3 microwave dielectric ceramics for dielectric resonator antenna applications

The current paper reports on the crystal structure, microwave dielectric properties as well as the antenna parameters of (1-x)MgTiO3 - xSrTiO3 (abbreviated as (1-x)MT-xST) for x = 0.025, 0.05, 0.075, 0.1 ceramic based dielectric resonator antennas (DRAs). The (1-x) MT - xST samples have been prepared with the help of a solid-state reaction route. The SrTiO3 was introduced to MgTiO3 as a τf compensator for developing a tunable τf material. Rietveld refinement results of X-ray diffraction data suggest that all the samples exhibit a combination of two crystallographic phases i.e., rhombohedral (R-3) + cubic (Pm-3m). The SEM micrographs show clear and well-defined grains for (1-x)MT - xST (for x = 0.025–0.1) ceramics. The modes of vibration of the crystal structures of the materials have been identified by the Raman spectroscopy method. The bond strength, bond valency, bond energy, and tolerance factor have been determined for (1-x)MT - xST (for x = 0.025–0.1) materials. The microwave dielectric performances of ceramics have been analyzed over a frequency band of 1–10 GHz. It has been found that the dielectric constant is almost constant along the microwave frequency range. The behavioral change of tuned temperature coefficient of resonant frequency (τf) along with quality factor have been reported. Besides, DRAs have been formed using all ceramic compositions, and simulations were performed to determine the various antenna properties, such as efficiency, input impedance, radiation properties, gain, and reflection coefficient. This study supports the use of microwave dielectric ceramics in antenna fields and highlights the enormous potential of (1-x)MT - xST for (x = 0.05) materials in communication systems.

Investigation of silicon doped carbon dots/Carboxymethyl cellulose gel platform with tunable afterglow and dynamic multistage anticounterfeiting

The remarkable optical properties of carbon dots, particularly their tunable room-temperature phosphorescence, have garnered significant interest. However, challenges such as aggregation propensity and complex phosphorescence control via energy level manipulation during synthesis persist. Addressing these issues, we present a facile gel platform for tunable afterglow materials. This involves chemically cross-linking biomass-derived silicon-doped carbon dots with carboxymethylcellulose and incorporating non-precious metal salts (BaCl2, CaCl2, MgCl2, ZnCl2, ZnBr2, ZnSO4) to enhance phosphorescence. Metal salts boost intersystem crossing via spin–orbit coupling, elevating triplet state transitions and activating phosphorescence. Chemical bonding and salt-induced coordination/electrostatic interactions establish confinement effects, suppressing non-radiative transitions. Diverse salt-gel interactions yield gels with tunable phosphorescence lifetimes (9.48 ms to 32.13–492.39 ms), corresponding to afterglow durations ranging from 3.20 to 11.86 s. With its broad tunability and high recognition, this gel material exhibits promising potential for dynamic multilevel anti-counterfeiting applications.