Engineering Proteins for PEDOT Dispersions: A New Horizon for Highly Mixed Ionic-Electronic Biocompatible Conducting Materials.

Poly (3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonate (PSS) is the most used conducting polymer from energy to biomedical applications. Despite its exceptional properties, there is a need for developing new materials that can improve some of its inherent limitations, e.g., biocompatibility. In this context, doping PEDOT is propose with a robust recombinant protein with tunable properties, the consensus tetratricopeptide repeated protein (CTPR). The doping consists of an oxidative polymerization, where the PEDOT chains are stabilized by the negative charges of the CTPR protein. CTPR proteins are evaluated with three different lengths (3, 10, and 20 identical CTPR units) and optimized varied synthetic conditions. These findings revealed higher doping rate and oxidized state of the PEDOT chains when doped with the smallest scaffold (CTPR3). These PEDOT:CTPR hybrids possess ionic and electronic conductivity. Notably, PEDOT:CTPR3 displayed an electronic conductivity of 0.016 S cm-1, higher than any other reported protein-doped PEDOT. This result places PEDOT:CTPR3 at the level of PEDOT-biopolymer hybrids, and brings it closer in performance to PEDOT:PSS gold standard. Furthermore, PEDOT:CTPR3 dispersion is successfully optimized for inkjet printing, preserving its electroactivity properties after printing. This approach opens the door to the use of these novel hybrids for bioelectronics.

CORROSION INHIBITION OF MILD STEEL BY COUMARATE-BASED IONIC LIQUIDS AND COATINGS.

The use of ionic liquids (ILs) as corrosion inhibitors gained attention due to their attractive properties such as high inhibition efficiency and ability to absorb onto metal surfaces. In this work, six  ILs, based on the coumarate anion combined with different nitrogen cations (triethylammonium, pyrrolidinium and imidazolium with short and long alkyl chain attached to the nitrogen atom) have been synthesized and evaluated as inhibitors for steel. The anticorrosion properties of these ILs in solution were investigated electrochemically and the metal surface was analyzed by SEM. Moreover, the IL prepared from the coumarate anion and N-dimethyl-N-tetradecyl ammonium ([DTA]Cou) was incorporated into an UV-coating formulation as an additive and by designing a similar ionic monomer which covalently links to the formulation. Impedance spectroscopy during 11 days of exposure to a solution of NaCl 0,01M, confirmed the high performance of the inhibitor in both solution and when incorporated into a coating. The synthesized ILs present efficiencies in solution exceeding 70%, in particular the ILs [DTA]Cou and tetradecyl imidazolium coumarate ([C14Im]Cou) showed efficiencies of 88% and 91% respectively. The obtained inhibitors showed interesting anticorrosion behaviors and demonstrated how different cations and an increase in the chain length affect the inhibition properties.

Piperazinium Poly(Ionic Liquid)s as Solid Electrolytes for Lithium Batteries.

Poly(ionic liquid)s combine the unique properties of ionic liquids (ILs) within ionic polymers holding significant promise for energy storage applications. It is reported here the synthesis and characterization of a new family of poly(ionic liquid)s synthesized from cationic piperazinium ionic liquid monomers. The cationic poly(acrylamide piperazinium) in combination with sulfonamide anions like bis(trifluoromethanesulfonyl) imide (TFSI) and bis(fluorosulfonyl) imide (FSI) are characterized as solid polymer electrolytes. The polymer electrolytes in combination with pyrrolidonium ILs and LiFSI show high ionic conductivity, 5×10-3 S cm-1 at 100 °C. Piperazinium polymer electrolytes show excellent compatibility with lithium metal reversible plating and stripping at high current density and low temperature 40 °C.

Mixed Conductive, Injectable, and Fluorescent Supramolecular Eutectogel Composites.

Eutectogels are an emerging family of soft ionic materials alternative to ionic liquid gels and organogels, offering fresh perspectives for designing functional dynamic platforms in water-free environments. Herein, the first example of mixed ionic and electronic conducting supramolecular eutectogel composites is reported. A fluorescent glutamic acid-derived low-molecular-weight gelator (LMWG) was found to self-assemble into nanofibrillar networks in deep eutectic solvents (DES)/poly(3,4-ethylenedioxythiophene) (PEDOT): chondroitin sulfate dispersions. These dynamic materials displayed excellent injectability and self-healing properties, high ionic conductivity (up to 10-2  S cm-1 ), good biocompatibility, and fluorescence imaging ability. This set of features turns the mixed conducting supramolecular eutectogels into promising adaptive materials for bioimaging and electrostimulation applications.

Selective Chemical Upcycling of Mixed Plastics Guided by a Thermally Stable Organocatalyst.

Chemical recycling of plastic waste represents a greener alternative to landfill and incineration, and potentially offers a solution to the environmental consequences of increased plastic waste. Most plastics that are widely used today are designed for durability, hence currently available depolymerisation methods typically require harsh conditions and when applied to blended and mixed plastic feeds generate a mixture of products. Herein, we demonstrate that the energetic differences for the glycolysis of BPA-PC and PET in the presence of a protic ionic salt TBD:MSA catalyst enables the selective and sequential depolymerisation of these two commonly employed polymers. Employing the same procedure, functionalised cyclic carbonates can be obtained from both mixed plastic wastes and industrial polymer blend. This methodology demonstrates that the concept of catalytic depolymerisation offers great potential for selective polymer recycling and also presents plastic waste as a "greener" alternative feedstock for the synthesis of high added value molecules.

Antibacterial silk fibroin/nanohydroxyapatite hydrogels with silver and gold nanoparticles for bone regeneration.

The rapid emergence of antibiotic resistance is becoming an imminent problem in bone tissue engineering, and therefore biomaterials must be modified to promote the tissue integration before bacterial adhesion. In this work, silk fibroin/nanohydroxyapatite hydrogel was modified with in situ synthesized silver and gold nanoparticles (AgNPs and AuNPs), taking advantage of the tyrosine amino acid. The presence of AgNPs and AuNPs in the hydrogels was characterized by UV spectrophotometer, transmission electron microscopy and thermogravimetric analysis. In vitro antimicrobial studies revealed that hydrogels with AgNPs and AuNPs exhibited significant inhibition ability against both gram-positive and gram-negative bacteria. Cytocompatibility studies carried out using osteoblastic cells revealed that up to 0.5 wt% of AgNPs, and for all concentrations of AuNPs, the hydrogels can be effectively used as antimicrobial materials, without compromising cell behavior. On the basis of the aforementioned observations, these hydrogels are very attractive for bone tissue engineering.

Thermoresponsive Random Poly(ether urethanes) with Tailorable LCSTs for Anticancer Drug Delivery.

A new class of thermoresponsive random polyurethanes is successfully synthesized and characterized. Poly(ethylene glycol) diol (Mn = 1500 Da) and 2,2-dimethylolpropionic acid are reacted with isophorone diisocyanate in the presence of methane sulfonic acid catalyst. It is found that these polyurethanes are thermoresponsive in aqueous media and manifest a lower critical solution temperature (LCST) that can be easily tuned from 30 °C to 70 °C by increasing the poly(ethylene glycol) content. Their sharp LCST transitions make these random polyurethanes ideal candidates for stimuli-responsive drug delivery applications. To that end, the ability of these systems to efficiently sequester doxorubicin (up to 36 wt%) by means of a sonication/dialysis method is successfully demonstrated. Additionally, it is also demonstrated that accelerated doxorubicin release kinetics from the nanoparticles can be attained above the LCST.

Biohybrid Energy Storage Circuits Based on Electronically Functionalized Plant Roots.

Biohybrid systems based on plants integrate plant structures and processes into technological components targeting more sustainable solutions. Plants' biocatalytic machinery, for example, has been leveraged for the organization of electronic materials directly in the vasculature and roots of living plants, resulting in biohybrid electrochemical devices. Among other applications, energy storage devices were demonstrated where the charge storage electrodes were seamlessly integrated into the plant tissue. However, the capacitance and the voltage output of a single biohybrid supercapacitor are limited. Here, we developed biohybrid circuits based on functionalized conducting roots, extending the performance of plant based biohybrid energy storage systems. We show that root-supercapacitors can be combined in series and in parallel configuration, achieving up to 1.5 V voltage output or up to 11 mF capacitance, respectively. We further demonstrate that the supercapacitors circuit can be charged with an organic photovoltaic cell, and that the stored charge can be used to power an electrochromic display or a bioelectronic device. Furthermore, the functionalized roots degrade in composting similarly to native roots. The proof-of-concept demonstrations illustrate the potential of this technology to achieve more sustainable solutions for powering low consumption devices such as bioelectronics for agriculture or IoT applications.

Multiresponsive 4D Printable Hydrogels with Anti-Inflammatory Properties.

Multiresponsive hydrogels are valuable as biomaterials due to their ability to respond to multiple biologically relevant stimuli, i.e., temperature, pH, or reactive oxygen species (ROS), which can be present simultaneously in the body. In this work, we synthesize triple-responsive hydrogels through UV light photopolymerization of selected monomer compositions that encompass thermoresponsive N-isopropylacrylamide (NIPAM), pH-responsive methacrylic acid (MAA), and a tailor-made ROS-responsive diacrylate thioether monomer (EG3SA). As a result, smart P[NIPAMx-co-MAAy-co-(EG3SA)z] hydrogels capable of being manufactured by digital light processing (DLP) 4D printing are obtained. The thermo-, pH-, and ROS-response of the hydrogels are studied by swelling tests and rheological measurements at different temperatures (25 and 37 °C), pHs (3, 5, 7.4, and 11), and in the absence or presence of ROS (H2O2). The hydrogels are employed as matrixes for the encapsulation of ketoprofen (KET), an anti-inflammatory drug that shows a tunable release, depending on the hydrogel composition and stimuli applied. The cytotoxicity properties of the hydrogels are tested in vitro with mouse embryonic fibroblasts (NIH 3T3) and RAW 264.7 murine macrophage (RAW) cells. Finally, the anti-inflammatory properties are assessed, and the results exhibit a ≈70% nitric oxide reduction up to base values of pro-inflammatory RAW cells, which highlights the anti-inflammatory capacity of P[NIPAM80-co-MAA15-co-(EG3SA)5] hydrogels, per se, without being necessary to encapsulate an anti-inflammatory drug within their network. It opens the route for the fabrication of customizable 4D printable scaffolds for the effective treatment of inflammatory pathologies.

ROS-Responsive 4D Printable Acrylic Thioether-Based Hydrogels for Smart Drug Release.

Reactive oxygen species (ROS) play a key role in several biological functions like regulating cell survival and signaling; however, their effect can range from beneficial to nondesirable oxidative stress when they are overproduced causing inflammation or cancer diseases. Thus, the design of tailor-made ROS-responsive polymers offers the possibility of engineering hydrogels for target therapies. In this work, we developed thioether-based ROS-responsive difunctional monomers from ethylene glycol/thioether acrylate (EGnSA) with different lengths of the EGn chain (n = 1, 2, 3) by the thiol-Michael addition click reaction. The presence of acrylate groups allowed their photopolymerization by UV light, while the thioether groups conferred ROS-responsive properties. As a result, smart PEGnSA hydrogels were obtained, which could be processed by four-dimensional (4D) printing. The mechanical properties of the hydrogels were determined by rheology, pointing out a decrease of the elastic modulus (G') with the length of the EG segment. To enhance the stability of the hydrogels after swelling, the EGnSA monomers were copolymerized with a polar monomer, 2-hydroxyethyl acrylate (HEA), leading to P[(EGnSA)x-co-HEAy] with improved compatibility in aqueous media, making it a less brittle material. Swelling properties of the hydrogels increased in the presence of hydrogen peroxide, a kind of ROS, reaching values of ≈130% for P[(EG3SA)7-co-HEA93] which confirms the stimuli-responsive properties. Then, the P[(EG3SA)x-co-HEAy] hydrogels were employed as matrixes for the encapsulation of a chemotherapeutic drug, 5-fluorouracil (5FU), which showed sustained release over time modulated by the presence of H2O2. Finally, the effect of the 5-FU release from P[(EG3SA)x-co-HEAy] hydrogels was tested in vitro with melanoma cancer cells B16F10, pointing out B16F10 growth inhibition values in the range of 40-60% modulated by the EG3SA percentage and the presence or absence of ROS agents, thus confirming their excellent ROS-responsive properties for the treatment of localized pathologies.

Minimizing Interfacial Recombination in 1.8 eV Triple-Halide Perovskites for 27.5% Efficient All-Perovskite Tandems.

All-perovskite tandem solar cells show great potential to enable the highest performance at reasonable costs for a viable market entry in the near future. In particular, wide-bandgap (WBG) perovskites with higher open-circuit voltage (VOC ) are essential to further improve the tandem solar cells' performance. Here, a new 1.8 eV bandgap triple-halide perovskite composition in conjunction with a piperazinium iodide (PI) surface treatment is developed. With structural analysis, it is found that the PI modifies the surface through a reduction of excess lead iodide in the perovskite and additionally penetrates the bulk. Constant light-induced magneto-transport measurements are applied to separately resolve charge carrier properties of electrons and holes. These measurements reveal a reduced deep trap state density, and improved steady-state carrier lifetime (factor 2.6) and diffusion lengths (factor 1.6). As a result, WBG PSCs achieve 1.36 V VOC , reaching 90% of the radiative limit. Combined with a 1.26 eV narrow bandgap (NBG) perovskite with a rubidium iodide additive, this enables a tandem cell with a certified scan efficiency of 27.5%.

Thermally Reversible Organocatalyst for the Accelerated Reprocessing of Dynamic Networks with Creep Resistance.

The industrial implementation of covalent adaptable networks hinges on the delicate task of achieving rapid bond exchange activation at specific temperatures while ensuring a sufficiently slow exchange at working temperatures to avoid irreversible deformation. In this pursuit, latent catalysts offer a potential solution, allowing for spatiotemporal control of dynamic exchange in vitrimer networks. However, the irreversible nature of their activation has led to undesired creep deformation after multiple cycles of reprocessing. In this work, we demonstrate that a tetraphenylborate tetramethyl guanidinium salt (TPB:TMG) undergoes a reversible thermal dissociation, releasing free TMG. This thermally reversible organocatalyst can be readily introduced as an additive in industrially relevant materials such as disulfide-containing polyurethane networks (PU) that undergo disulfide exchange in the presence of a base catalyst. In contrast with a free-base-catalyzed process, we demonstrate the dual benefit of adding the thermally reversible TPB:TMG in preventing creep at lower temperatures and also enabling reprocessability of disulfide-containing PU networks at elevated temperatures. The remarkable reversibility of this thermally activated catalyst allows for multiple reprocessing cycles while effectively maintaining a creep-free state at service temperature.

Bio-Based Polyhydroxyanthraquinones as High-Voltage Organic Electrode Materials for Batteries.

Organic materials have gained much attention as sustainable electrode materials for batteries. Especially bio-based organic electrode materials (OEMs) are very interesting due to their geographical independency and low environmental impact. However, bio-based OEMs for high-voltage batteries remain scarce. Therefore, in this work, a family of bio-based polyhydroxyanthraquinones (PHAQs)-namely 1,2,3,4,5,6,7,8-octahydroxyanthraquinone (OHAQ), 1,2,3,5,6,7-hexahydroxyanthraquinone (HHAQ), and 2,3,6,7-tetrahydroxyanthraquinone (THAQ)-and their redox polymers were synthesized. These PHAQs were synthesized from plant-based precursors and exhibit both a high-potential polyphenolic redox couple (3.5-4.0 V vs Li/Li+) and an anthraquinone redox moiety (2.2-2.8 V vs Li/Li+), while also showing initial charging capacities of up to 381 mAh g-1. To counteract the rapid fading caused by dissolution into the electrolyte, a facile polymerization method was established to synthesize PHAQ polymers. For this, the polymerization of HHAQ served as a model reaction where formaldehyde, glyoxal, and glutaraldehyde were tested as linkers. The resulting polymers were investigated as cathode materials in lithium metal batteries. PHAQ polymer composites synthesized using formaldehyde as linker and 10 wt % multiwalled carbon nanotubes (MWCNTs), namely poly(THAQ-formaldehyde)-10 wt % MWCNTs and poly(HHAQ-formaldehyde)-10 wt % MWCNTs, exhibited the best cycling performance in the lithium metal cells, displaying a high-voltage discharge starting at 4.0 V (vs Li/Li+) and retaining 81.6 and 77.3 mAh g-1, respectively, after 100 cycles.

In vivo neuromodulation of animal behavior with organic semiconducting oligomers.

Modulating neural activity with electrical or chemical stimulus can be used for fundamental and applied research. Typically, neuronal stimulation is performed with intracellular and extracellular electrodes that deliver brief electrical pulses to neurons. However, alternative wireless methodologies based on functional materials may allow clinical translation of technologies to modulate neuronal function. Here, we show that the organic semiconducting oligomer 4-[2-{2,5-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)thiophen-3-yl}ethoxy]butane-1-sulfonate (ETE-S) induces precise behaviors in the small invertebrate Hydra, which were dissected through pharmacological and electrophysiological approaches. ETE-S-induced behavioral response relies on the presence of head neurons and calcium ions and is prevented by drugs targeting ionotropic channels and muscle contraction. Moreover, ETE-S affects Hydra's electrical activity enhancing the contraction burst frequency. The unexpected neuromodulatory function played by this conjugated oligomer on a simple nerve net opens intriguing research possibilities on fundamental chemical and physical phenomena behind organic bioelectronic interfaces for neuromodulation and on alternative methods that could catalyze a wide expansion of this rising technology for clinical applications.

Dual redox-active porous polyimides as high performance and versatile electrode material for next-generation batteries.

Energy storage will be a primordial actor of the ecological transition initiated in the energy and transport sectors. As such, innovative approaches to design high-performance electrode materials are crucial for the development of the next generation of batteries. Herein, a novel dual redox-active and porous polyimide network (MTA-MPT), based on mellitic trianhydride (MTA) and 3,7-diamino-N-methylphenothiazine (MPT) monomers, is proposed for applications in both high energy density lithium batteries and symmetric all-organic batteries. The MTA-MPT porous polyimide was synthesized using a novel environmentally-friendly hydrothermal polymerization method. Rooted in its dual redox proprieties, the MTA-MPT porous polyimide exhibits a high theoretical capacity making it a very attractive cathode material for high energy density battery applications. The cycling performance of this novel electrode material was assessed in both high energy density lithium batteries and light-weight symmetric all-organic batteries, displaying excellent rate capability and long-term cycling stability.

High Density Body Surface Potential Mapping with Conducting Polymer-Eutectogel Electrode Arrays for ECG imaging.

Electrocardiography imaging (ECGi) is a non-invasive inverse reconstruction procedure which employs body surface potential maps (BSPM) obtained from surface electrode array measurements to improve the spatial resolution and interpretability of conventional electrocardiography (ECG) for the diagnosis of cardiac dysfunction. ECGi currently lacks precision, which has prevented its adoption in clinical setups. The introduction of high-density electrode arrays could increase ECGi reconstruction accuracy but is not attempted before due to manufacturing and processing limitations. Advances in multiple fields have now enabled the implementation of such arrays which poses questions on optimal array design parameters for ECGi. In this work, a novel conducting polymer electrode manufacturing process on flexible substrates is proposed to achieve high-density, mm-sized, conformable, long-term, and easily attachable electrode arrays for BSPM with parameters optimally selected for ECGi applications. Temporal, spectral, and correlation analysis are performed on a prototype array demonstrating the validity of the chosen parameters and the feasibility of high-density BSPM, paving the way for ECGi devices fit for clinical application.

Chitosan-Modified Polyethyleneimine Nanoparticles for Enhancing the Carboxylation Reaction and Plants' CO2 Uptake.

Increasing plants' photosynthetic efficiency is a major challenge that must be addressed in order to cover the food demands of the growing population in the changing climate. Photosynthesis is greatly limited at the initial carboxylation reaction, where CO2 is converted to the organic acid 3-PGA, catalyzed by the RuBisCO enzyme. RuBisCO has poor affinity for CO2, but also the CO2 concentration at the RuBisCO site is limited by the diffusion of atmospheric CO2 through the various leaf compartments to the reaction site. Beyond genetic engineering, nanotechnology can offer a materials-based approach for enhancing photosynthesis, and yet, it has mostly been explored for the light-dependent reactions. In this work, we developed polyethyleneimine-based nanoparticles for enhancing the carboxylation reaction. We demonstrate that the nanoparticles can capture CO2 in the form of bicarbonate and increase the CO2 that reacts with the RuBisCO enzyme, enhancing the 3-PGA production in in vitro assays by 20%. The nanoparticles can be introduced to the plant via leaf infiltration and, because of the functionalization with chitosan oligomers, they do not induce any toxic effect to the plant. In the leaves, the nanoparticles localize in the apoplastic space but also spontaneously reach the chloroplasts where photosynthetic activity takes place. Their CO2 loading-dependent fluorescence verifies that, in vivo, they maintain their ability to capture CO2 and can be therefore reloaded with atmospheric CO2 while in planta. Our results contribute to the development of a nanomaterials-based CO2-concentrating mechanism in plants that can potentially increase photosynthetic efficiency and overall plants' CO2 storage.

Interface engineering for high-performance, triple-halide perovskite-silicon tandem solar cells.

Improved stability and efficiency of two-terminal monolithic perovskite-silicon tandem solar cells will require reductions in recombination losses. By combining a triple-halide perovskite (1.68 electron volt bandgap) with a piperazinium iodide interfacial modification, we improved the band alignment, reduced nonradiative recombination losses, and enhanced charge extraction at the electron-selective contact. Solar cells showed open-circuit voltages of up to 1.28 volts in p-i-n single junctions and 2.00 volts in perovskite-silicon tandem solar cells. The tandem cells achieve certified power conversion efficiencies of up to 32.5%.

Correction: Biohybrid plants with electronic roots via in vivo polymerization of conjugated oligomers.

Correction for 'Biohybrid plants with electronic roots via in vivo polymerization of conjugated oligomers' by Daniela Parker et al., Mater. Horiz., 2021, 8, 3295-3305, DOI: 10.1039/D1MH01423D.

Natural Deep Eutectic Solvents Based on Choline Chloride and Phenolic Compounds as Efficient Bioadhesives and Corrosion Protectors.

Natural deep eutectics solvents (NADES), owing to their high solvation capacity and nontoxicity, are actively being sought for many technological applications. Herein, we report a series of novel NADES based on choline chloride and plant-derived polyphenols. Most of the obtained phenolic NADES have a wide liquid range and high thermal stability above 150 °C. Among them, small-sized polyphenols, like pyrogallol, vanillyl alcohol, or gentisic acid, lead to low-viscosity liquids with ionic conductivities in the order of 10-3 S cm-1 at room temperature. Interestingly, polyphenols possess valuable properties as therapeutic agents, antioxidants, adhesives, or redox-active compounds, among others. Thus, we evaluated the potential of these novel NADES for two applications: bioadhesives and corrosion protection. The mixture of choline chloride-vanillyl alcohol (2:3 mol ratio) and gelatin resulted in a highly adhesive viscoelastic liquid (adhesive stress ≈ 135 kPa), affording shear thinning behavior. Furthermore, choline chloride-tannic acid (20:1) showed an extraordinary ability to coordinate iron ions, reaching excellent corrosion inhibitive efficiencies in mild steel protection.