Pom Functionalized Ionogels with Tunable Optical, Mechanical, Electrical, and Sensory Properties

Carbon nanosheets are mechanically stable, free‐standing two‐dimensional materials with a thickness of ≈1 nm and well defined physical and chemical properties. They are made by radiation‐induced cross‐linking of aromatic self‐assembled monolayers. Herein, a route is presented to the scalable fabrication of multilayer nanosheets with tunable electrical, optical, and chemical properties on insulating substrates. Stacks of up to five nanosheets with sizes of ≈1 cm2 on oxidized silicon are studied. Their optical characteristics are investigated by visual inspection, optical microscopy, UV–vis reflection spectroscopy, and model calculations. Their chemical composition is studied by X‐ray photoelectron spectroscopy. The multilayer samples are then annealed in an ultrahigh vacuum at various temperatures up to 1100 K. A subsequent investigation by Raman, X‐ray photoelectron, and UV–vis reflection spectroscopy, as well as by electrical four‐point probe measurements, demonstrates that the layered nanosheets transform into nanocrystalline graphene. This structural and chemical transformation is accompanied by changes in the optical properties and electrical conductivity and opens up a new path for the fabrication of ultrathin functional conductive coatings.

For synthesing the FeMo cofactor of nitrogenase N 2 ‐fixing bacteria continuously demand molybdate nonconstantly available in their habitats. Significant selection advantages have those species containing the molybdenum storage protein (MoSto) due to its capability to deposit ca. 130 Mo compactly as polynuclear Mo(VI)‐O or polyoxometalate (POM) clusters. Due to similar physicochemical properties, W can be stored in a related fashion. Heterododecameric MoSto is built up of two heterohexameric (αβ) 3 cages each containing 5 distinct locations for POM clusters. The complex interplay of self‐assembly and protein‐promoted processes creates a great diversity of POM clusters varying between 2 and 16 Mo atoms. Starting from smaller core species multiply linked with protein templates larger aggregates are synthesized that contain as a component an archetypical POM cluster found in solution. Mechanistically, POM cluster formation proceeds within a two‐step process. Molybdate is, at first, pressed through the cage shell in an ATP‐consuming fashion and then spontaneously polymerizes in the cage to POM clusters. Molybdate appears to be activated in the first step by phosphorylation in an ATP kinase reaction. The formed instable phosphoric‐molybdic anhydride intermediate is afterward, instantaneously, hydrolyzed in a locked chamber and the energized molybdate penetrates the protein shell at a thin place.

Ionic solution-processable Ag nanostructures with tunable optical and electrical properties and strong adhesion to general substrates

The tunable electronic, electrical and optical properties of graphene oxide (GO) sheets were investigated using a controlled reduction by 500 keV Ar+-ion irradiation. The carbon to oxygen ratio of the GO sheets upon the ion beam reduction has been estimated using resonant Rutherford backscattering spectrometry analyses and its effect on the electrical and optical properties of GO sheets has been studied using sheet resistance measurements and photoluminescence (PL) measurements. The restoration of sp2-hybridized carbon atoms within the sp3 matrix is found to be increases with increasing the Ar+-ion fluences as evident from Fourier transform infrared, and x-ray absorption near-edge structure measurements. The decrease in the number of disorder-induced local density of states (LDOSs) within the π–π* gap upon the reduction causes the shifting of PL emission from near infra-red to blue region and decreases the sheet resistance. The improved electrical and optical properties of GO sheets were correlated to the decrease in the number of LDOSs within the π–π* gap. Our experimental investigations suggest ion beam irradiation is one of an effective approaches to reduce GO to RGO and to tailor its electronic, electrical and optical properties.

Natural polysaccharide-based injectable hydrogels with tunable mechanical and electrical properties enabled by phytic acid.

Thin film transistors fabricated using ZnSe thin films synthesized using chemical bath deposition.

To facilitate the practical use of ionic conductive materials for flexible electronics, the issues existing in hydrogels and ionogels, such as low thermostability and possible solvent leakage, need to be resolved but are inevitable. Liquid-free ionic elastomers (ICEs) as an alternative option are free of such concerns but have been facing the drawbacks of low conductivity and less satisfying mechanical properties. Here, a versatile copolymer with π-π stacking and cation-π interactions for high-performance ICE is proposed. The ICEs presented tunable mechanical and electrical properties by varying the feed ratio of the ternary monomers. The optimized ICE possessed high stretchability and strength, fast shape-recovery, self-healing, decent conductivity, and desirable stability against heat and under ambient conditions. The use of virgin and self-healed ICEs as the conductors for dielectric elastomer actuators (DEA) is demonstrated and exhibits comparable actuating performance to the reported DEA employing organogels and ionogels. The work provides a facile approach for fabricating ICEs with versatile properties that can be used for flexible electronics.

Modern wearable electronics require scalable, flexible, and conductive electrodes with tunable properties. Abundant materials such as graphite as a conductive component and polymer as a flexible component forming a composite film (electrode) via simple synthesis technique are particularly captivating. This approach conveniently satisfies the fundamental needs of an ideal electrode yet provides a conductive platform to accommodate a secondary material for various purposes in electrochemical energy conversion and storage. Accordingly, we optimize a graphite-polymer composite film with good conductivity and flexibility to incorporate two-dimensional (2D) VSx (mixed phase predominated by V5S8) as an active material within the film. We exemplify the dual functionalities of the VSx/graphite flexible electrode as i) a photo-electrocatalyst for enhanced hydrogen evolution reaction by visible and near-infrared light irradiation (overpotential ≈500 mV at the current density of −10 mA cm−2), and ii) a conductive electrode for symmetrical solid-state supercapacitor with pseudocapacitive charge storage mechanism (areal capacitance of 123 mF cm−2 and areal capacity of 34 µAh cm−2 at the current density of 0.5 mA cm−2). Our work demonstrates the versatility of graphite films in terms of size, shape, flexibility, and scalability, with tunable physical, optical, and electrical properties by integrating other secondary materials. We combine flexible graphite film and 2D vanadium sulfide with near-infrared photoresponse and pseudocapacitive properties, as an economically feasible avenue for energy harvesting, outer space application, and wearable devices.

Printable, self-healing, stretchable, and conductive materials have tremendous potential for the fabrication of advanced electronic devices. Poly(3,4-ethylenedioxithiopene) doped with polystyrene sulfonate (PEDOT:PSS) has been the focus of extensive research due to its tunable electrical and mechanical properties. Owing to its solution-processability and self-healing ability, PEDOT:PSS is an excellent candidate for developing printable inks. In this study, we developed printable, stretchable, dry, lightly adhesive, and self-healing materials for biomedical applications. Polyurethane diol (PUD), polyethylene glycol, and sorbitol were investigated as additives for PEDOT:PSS. In this study, we identified an optimal printable mixture obtained by adding PUD to PEDOT:PSS, which improved both the mechanical and electrical properties. PUD/PEDOT:PSS free-standing films with optimized composition showed a conductivity of approximately 30 S cm−1, stretchability of 30%, and Young’s modulus of 15 MPa. A low resistance change (<20%) was achieved when the strain was increased to 30%. Excellent electrical stability under cyclic mechanical strain, biocompatibility, and 100% electrical self-healing were also observed. The potential biomedical applications of this mixture were demonstrated by fabricating a printed epidermal electrode on a stretchable silicone substrate. The PUD/PEDOT:PSS electrodes displayed a skin-electrode impedance similar to commercially available ones, and successfully captured physiological signals. This study contributes to the development of improved customization and enhanced mechanical durability of soft electronic materials.

In this paper, we experimentally investigate the effect of annealing and ligand removal on the electrical and photovoltaic properties of polycrystalline films formed from a colloidal solution of heterostructured CdSe/CdS nanoparticles in chlorobenzene using the drop-casting method. Annealing leads to a significant increase in photoconductivity, up to 4 orders of magnitude, while the band gap of the CdSe/CdS nanoplatelet film remains unchanged. Moreover, it was shown that the annealing causes a change in the dominant recombination mechanism from monomolecular to bimolecular due to an increase in charge carrier mobility. These findings directly demonstrate the possibility of creating highly photoconductive nanocrystalline films with tunable optical and electrical properties. Moreover, annealing also provides the growth of photosensitivity from approximately 0.87 to 2.75 A/W for photons with 2.12 eV energy, which is a record value for such nanocrystalline films. Considered films have the potential to significantly enhance the sensitivity of photodetectors and solar cell efficiency.

A new approach to prepare heterometallic cluster organic frameworks has been developed. The method was employed to link Anderson-type polyoxometalate (POM) clusters and transition-metal clusters by using a designed rigid tris(alkoxo) ligand containing a pyridyl group to form a three-fold interpenetrated anionic diamondoid structure and a 2D anionic layer, respectively. This technique facilitates the integration of the unique inherent properties of Anderson-type POM clusters and cuprous iodide clusters into one cluster organic framework.

1D superlattices with long-ranged periodicity present extraordinary application properties due to their unique electronic structures. Here, the visible light driven synthesis of 1D single-cluster chains constructed by polyoxometalate (POM) and Ag clusters is reported, where two types of clusters align alternatively along the nanowire. Low symmetrical POM clusters of [P2 W17 O61 ]10- , [P2 W15 O56 ]12- , and [EuW10 O36 ]9- can be used as building blocks. The directly bonding cluster units result in interactive electronic structures of Ag and POM clusters, as well as the greatly promoted electron transfer during the redox reaction. The Ag-P2 W17 nanowires perform significantly enhanced activities in both electrochemical sensing and catalytic gasoline desulfurization compared with individual building blocks, demonstrating the extraordinary application properties and promising potentials of cluster-based heteroconstructions.

Low-k dielectric films have been developed using a new silsesquioxane based chemistry that allows both the electrical and mechanical properties to be tuned to specific values. By controlling the composition and film processing conditions of spin-on formulations, dielectric constants in the range 1.5 to 3.0 are obtained with modulus values that range from 1 to 30 GPa. The modulus and dielectric constant are tuned by controlling porosity, which varies from 0 to &gt;60%, and final film composition which varies from HSiO3/2 to SiO4/2. The spin-on formulation includes hydrogen silsesquioxane resin and solvents. Adjusting the ratio of solvents to resin in the spin-on formulation controls porosity. As-spun films are treated with ammonia and moisture to oxidize the resin and form a mechanically self-supporting gel. Solvent removal and further conversion to a more “silica-like” composition occur during thermal curing at temperatures of 400 to 450°C. The final film composition was controlled through both room temperature oxidation and thermal processing. Final film properties are optimized for a balance of electrical, mechanical and thermal properties to meet the specific requirements of a wide range of applications. Processed films exhibit no stress corrosion cracking or delamination upon indentation, with indenter penetration exceeding the film thickness, and followed by exposure to water at room temperature. Films also exhibit high adhesive strength (&gt; 60MPa) and low moisture absorption. Processing conditions, composition and properties of thin are discussed.

In this work, a versatile and simple strategy to build an injectable interpenetrating polymer network (IPN) hydrogel with tunable mechanical properties and self‐healing ability is reported. The gelation time and mechanical properties can be tuned by pH or the solid content. Due to the exchange of acylhydrazone and boronate ester bonds formed between functionalized prepolymers, the hydrogels can self‐heal at either acidic or basic condition. Furthermore, the pH‐induced IPN to semi‐IPN reversible transition endows the hydrogels with tunable pore structure and mechanical properties. It is hoped that this novel strategy will provide new opportunities in design and preparation of 3D‐printable IPN hydrogels, fostering their use in a wide range of applications such as controlled drug release and tissue engineering.

Hydrogels, exhibiting wide applications in soft robotics, tissue engineering, implantable electronics, etc., often require sophisticately tailoring of the hydrogel mechanical properties to meet specific demands. For examples, soft robotics necessitates tough hydrogels; stem cell culturing demands various tissue-matching modulus; and neuron probes desire dynamically tunable modulus. Herein, a strategy to broadly alter the mechanical properties of hydrogels reversibly via tuning the aggregation states of the polymer chains by ions based on the Hofmeister effect is reported. An ultratough poly(vinyl alcohol) (PVA) hydrogel as an exemplary material (toughness 150 ± 20MJm-3 ), which surpasses synthetic polymers like poly(dimethylsiloxane), synthetic rubber, and natural spider silk is fabricated. With various ions, the hydrogel's various mechanical properties are continuously and reversibly in situ modulated over a large window: tensile strength from 50 ± 9kPa to 15 ± 1MPa, toughness from 0.0167± 0.003 to 150 ± 20MJm-3 , elongation from 300± 100% to 2100± 300%, and modulus from 24 ± 2 to 2500 ± 140kPa. Importantly, the ions serve as gelation triggers and property modulators only, not necessarily required to remain in the gel, maintaining the high biocompatibility of PVA without excess ions. This strategy, enabling high mechanical performance and broad dynamic tunability, presents a universal platform for broad applications from biomedicine to wearable electronics.