Aligned Bioelectronic Polypyrrole/Collagen Constructs for Peripheral Nerve Interfacing

Electrical stimulation has shown promise in clinical studies to treat nerve injuries. This work is aimed to create an aligned bioelectronic construct that can be used to bridge a nerve gap, directly interfacing with the damaged nerve tissue to provide growth support. The conductive three-dimensional bioelectronic scaffolds described herein are composite materials, comprised of conductive polypyrrole (PPy) nanoparticles embedded in an aligned collagen hydrogel. The bioelectronic constructs are seeded with dorsal root ganglion derived primary rat neurons and electrically stimulated in vitro. The PPy loaded constructs support a 1.7-fold increase in neurite length in comparison to control collagen constructs. Furthermore, upon electrical stimulation of the PPy-collagen construct, a 1.8-fold increase in neurite length is shown. This work illustrates the potential of bioelectronic constructs in neural tissue engineering and lays the groundwork for the development of novel bioelectronic materials for neural interfacing applications

A High-Spin Ground-State Donor-Acceptor Conjugated Polymer

Interest in high-spin organic materials is driven by opportunities to enable far-reaching fundamental science and develop technologies that integrate light element spin, magnetic, and quantum functionalities. Although extensively studied, the intrinsic instability of these materials complicates synthesis and precludes an understanding of how fundamental properties associated with the nature of the chemical bond and electron pairing in organic materials systems manifest in practical applications. Here, we demonstrate a conjugated polymer semiconductor, based on alternating cyclopentadithiophene and thiadiazoloquinoxaline units, that is a ground-state triplet in its neutral form. Electron paramagnetic resonance and magnetic susceptibility measurements are consistent with a high-to-low spin energy gap of 9.30 × 10−3 kcal mol−1. The strongly correlated electronic structure, very narrow bandgap, intramolecular ferromagnetic coupling, high electrical conductivity, solution processability, and robust stability open access to a broad variety of technologically relevant applications once thought of as beyond the current scope of organic semiconductors

Establishing Design Guidelines for Conjugated Polymer-Based Sensing Technologies for Environmental Monitoring

The food, energy, and water (FEW) nexus has emerged as a new paradigm to guide scientists, policy makers, and businesses in making a conscious effort toward a sustainable future. The goal of the nexus approach is to transition to a Green Economy, aiming at efficiency, a reduction of negative externalities, and an increased quality of life. The lack of available information regarding the quality of our water resources persists as a major challenge to these efforts. The last few decades have demonstrated the rise of soft condensed matter sensing technologies in the form of solution-processed organic semiconductors based on conjugated polymeric (CP) materials. The delocalized electronic structures, large extinction coefficients, highly emissive properties, and synthetic tunability of CPs have popularized them for the detection of a wide range of analytes. Despite the achievement of significant technological milestones, clear design guidelines by which to tailor CP-based sensors for the detection of environmentally relevant analytes such as nitrates, phosphates, polycyclic aromatic hydrocarbons (PAHs), etc. in seawater remain absent. Chapter I introduces concepts that are the foundation of this research and frames the current limitations in the field. Chapter II demonstrates a simple post-polymerization modification protocol, based on thiol-ene click chemistry, that results in the rapid installation of ionic receptor chemistries onto a CPE scaffold. The fluorescence of the resulting water-soluble CPE is quenched by Fe3+, dequenched selectively by pyrophosphate (PPi), and accurately quantifies PPi within ±6 nM in artificial seawater. Chapters III and IV outline an alternative approach for the detection and discrimination of classes of analytes, such as PAHs and textile dyes, which lack recognition chemistries and are therefore precluded from traditional optical sensing platforms. In these systems the inner filter effect (IFE), in combination with CP array-based sensing, offers a straightforward approach for the quantitative and qualitative profiling of diverse libraries of similar spectroscopically active analytes. Chapter V further investigates the utility of the IFE in CP-based sensing, demonstrating the solvent and spatial independence of signal transduction through a solid-state sensor design, enabling a reusable sensor with broad applicability

Molecular Au(I) Complexes In the Photosensitized Photocatalytic CO\u3csub\u3e2\u3c/sub\u3e Reduction Reaction

Five Au complexes are evaluated for the reduction reaction of CO2 via cyclic voltammetry and in a photocatalytic system. Electrochemically, the complexes were all evaluated for pre-association with CO2 prior to electrochemical reduction and for thermodynamic favorability for CO2 reduction in photocatalytic systems. The complexes were evaluated in photocatalytic reactions using an Ir-based photosensitizer and a sacrificial electron donor for the conversion of CO2 to CO. Au-complex counterion effects on the photocatalytic reaction were analyzed by varying weakly coordinating counterions with significant performance changes noted. At low Au-complex concentrations, a high TON value of 700 was observed

Organic Electrochemical Transistors: From Device Models To a Targeted Design of Materials

Organic electrochemical transistors (OECTs) are highly versatile in terms of their form factor, fabrication approach that can be applied, and freedom in the choice of substrate material. Their ability to transduce ionic into electric signals and the use of bio-compatible organic materials makes them ideally suited for a wide range of applications, in particular in areas where electronic circuits are interfaced with biologic matter. OECT technology has attracted widespread interest in recent years, which has been accompanied by a steady increase in its performance. However, this progress was mainly driven by device optimization and less by targeting the design of new device geometries and OECT materials. To narrow this gap, this review provides an overview on the different device models that are used to explain the underlying physics governing the steady and transient behavior of OECTs. We show how the models can be used to identify synthetic targets to produce higher performing OECT materials and summarize recently reported materials classes. Overall, a road-map of future research in new device models and material design is presented summarizing the most pressing open questions in the understanding of OECTs

Thiol-ene Click Post-Polymerization Modification of a Fluorescent Conjugated Polymer for Parts-Per-Billion Pyrophosphate Detection in Seawater

The evolution of conjugated polyelectrolytes (CPEs) that transduce analyte-receptor interactions into detectable fluorescent responses in complex aqueous environments is predicated on advancements in molecular design and improved synthetic accessibility. Here, we demonstrate a simple post-polymerization modification protocol based on thiol-ene click chemistry that results in the rapid installation of sodium sulfate terminated side chains to a poly(fluorene-co-ethynyl) scaffold. The fluorescence of the resulting water-soluble CPE is quenched by Fe3+, dequenched selectively by pyrophosphate (PPi), and accurately quantifies PPi within ±6 nM in artificial seawater. The broad utility of thiol-ene click chemistry should offer the straightforward integration of diverse sensing elements

Monitoring Water Resources Governance Progress Globally: Experiences from Monitoring SDG Indicator 6.5.1 on Integrated Water Resources Management Implementation

Improved water resources governance supports important social, economic, and environmental objectives. The 2030 Agenda recognizes improved water governance to be critical for achievement of the Sustainable Development Goals (SDGs) and commits to monitor the progress of implementation of integrated water resources management (IWRM). This paper critically reviews the approach to monitoring SDG indicator 6.5.1 on implementation of IWRM. Firstly, the paper places the indicator monitoring within the context of other initiatives to measure water governance. Secondly, it analyzes experiences of application of the SDG indicator 6.5.1 methodology to evaluate the strengths and weaknesses of the indicator and presents the key findings of the 2017/2018 global baseline assessment of IWRM implementation. Baseline reporting shows that degree of IWRM implementation globally is 49%, though country scores range from 10 to 100%. Disaggregating the data by country and by aspect of water resources governance provides a diagnostic tool to identify areas of high and low progress, and, therefore, where increased resources and attention are required. The article concludes by suggesting how the next iteration of SDG indicator 6.5.1 monitoring cycle can be made into a tool for advancing the IWRM implementation and improved governance practices on the ground. It also proposes how the methodology can be strengthened to address current limitations, including aspects relating to integrity, accountability and transparency

Linear Supramolecular Polymers Driven by Anion-Anion Dimerization of Difunctional Phosphate Monomers Inside Cyanostar Macrocycles

Supramolecular polymers have enabled far-reaching fundamental science and the development of diverse macromolecular technologies owing to the reversible and noncovalent chemical connectivities that define their properties. Despite the unabated development of these materials using highly tailorable recognition elements, anion-based polymers remain rare as a result of the weak interactions they mediate. Here, we use design rules inspired by cation-driven polymers to demonstrate a new noncovalent link based on receptor-stabilized anion–anion interactions that enables the efficient linear polymerization of simple difunctional phosphonates. The linear main chain connectivity and molecular topology were confirmed by single crystal X-ray diffraction, which demonstrates the rare 2:2 stoichiometry between the anionic phosphonate end groups and a pair of π-stacked cyanostar macrocycles. The stability of these links enables rapid polymerization of difunctional phosphonates employing different aliphatic linkers (C6H12, C8H16, C10H20, C12H24). Diphosphonates with greater chain flexibility (C12H24) enable greater polymerization with an average degree of polymerization of nine emerging at 10 mM. Viscosity measurements show a transition from oligomers to polymers at the critical polymerization concentration of 5 mM. In a rare correlation, NMR spectroscopy shows a coincident molecular signature of the polymerization at 5 mM. These polymers are highly concentration dependent, reversibly polymerize with acid and base, and respond to competitive anions. They display the design simplicity of metallo-supramolecular polymers with transfer of the strong 2:2 recognition chemistry to macromolecules. The simplicity and understanding of this new class of supramolecular polymer is anticipated to open opportunities in tailoring anion-based functional materials

Tunable Adhesion From Stoichiometry-Controlled and Sequence-Defined Supramolecular Polymers Emerges Hierarchically From Canostar-Stabilized Anion-Anion Linkages

Sequence-controlled supramolecular polymers offer new design paradigms for generating stimuli-responsive macromolecules with enhanced functionalities. The dynamic character of supramolecular links present challenges to sequence definition in extended supramolecular macromolecules, and design principles remain nascent. Here, we demonstrate the first example of using stoichiometry-control to specify the monomer sequence in a linear supramolecular polymer by synthesizing both a homopolymer and an alternating copolymer from the same glycol-substituted cyanostar macrocycle and phenylene-linked diphosphate monomers. A 2:1 stoichiometry between macrocycle and diphosphate produces a supramolecular homopolymer of general formula (A)n comprised of repeating units of cyanostar-stabilized phosphate–phosphate dimers. Using a 1:1 stoichiometry, an alternating (AB)n structure is produced with half the phosphate dimers now stabilized by the additional counter cations that emerge hierarchically after forming the stronger cyanostar-stabilized phosphate dimers. These new polymer materials and binding motifs are sufficient to bear normal and shear stress to promote significant and tunable adhesive properties. The homopolymer (A)n, consisting of cyanostar-stabilized anti-electrostatic linkages, shows adhesion strength comparable to commercial superglue formulations based on polycyanoacrylate but is thermally reversible. Unexpectedly, and despite including traditional ionic linkages, the alternating copolymer (AB)n shows weaker adhesion strength more similar to commercial white glue based on poly(vinyl acetate). Thus, the adhesion properties can be tuned over a wide range by simply controlling the stoichiometric ratio of monomers. This study offers new insight into supramolecular polymers composed of custom-designed anion and receptor monomers and demonstrates the utility of emerging functional materials based on anion–anion linkages