A solution-processed n-type conducting polymer with ultrahigh conductivity.

Conducting polymers (CPs) with high conductivity and solution processability have made great advances since the pioneering work on doped polyacetylene1-3, thus creating the new field of 'organic synthetic metals,4. Various high-performance CPs have been realized, which enable the applications of several organic electronic devices5,6. Nevertheless, most CPs exhibit hole-dominant (p-type) transport behaviour7,8, whereas the development of n-type analogues lags far behind and only a few exhibit metallic state, typically limited by low doping efficiency and ambient instability. Here we present a facilely synthesized highly conductive n-type polymer poly(benzodifurandione) (PBFDO). The reaction combines oxidative polymerization and in situ reductive n-doping, greatly increasing the doping efficiency, and a doping level of almost 0.9 charges per repeating unit can be achieved. The resultant polymer exhibits a breakthrough conductivity of more than 2,000 S cm-1 with excellent stability and an unexpected solution processability without extra side chains or surfactants. Furthermore, detailed investigations on PBFDO show coherent charge-transport properties and existence of metallic state. The benchmark performances in electrochemical transistors and thermoelectric generators are further demonstrated, thus paving the way for application of the n-type CPs in organic electronics.

Inhibition of miR-143-3p alleviates myocardial ischemia reperfusion injury via limiting mitochondria-mediated apoptosis.

MicroRNA (miR)-143-3p is a potential regulatory molecule in myocardial ischemia/reperfusion injury (MI/RI), wherein its expression and pathological effects remains controversial. Thus, a mouse MI/RI and cell hypoxia/reoxygenation (H/R) models were built for clarifying the miR-143-3p's role in MI/RI. Following myocardial ischemia for 30 min, mice underwent reperfusion for 3, 6, 12 and 24 h. It was found miR-143-3p increased in the ischemic heart tissue over time after reperfusion. Cardiomyocytes transfected with miR-143-3p were more susceptible to apoptosis. Mechanistically, miR-143-3p targeted B cell lymphoma 2 (bcl-2). And miR-143-3p inhibition reduced cardiomyocytes apoptosis upon H/R, whereas it was reversed by a specific bcl-2 inhibitor ABT-737. Of note, miR-143-3p inhibition upregulated bcl-2 with better mitochondrial membrane potential (Δψm), reduced cytoplasmic cytochrome c (cyto-c) and caspase proteins, and minimized infarction area in mice upon I/R. Collectively, inhibition of miR-143-3p might alleviate MI/RI via targeting bcl-2 to limit mitochondria-mediated apoptosis. To our knowledge, this study further clarifies the miR-143-3p's pathological role in the early stages of MI/RI, and inhibiting miR-143-3p could be an effective treatment for ischemic myocardial disease.

Polyethylene glycol-decorated n-type conducting polymers with improved ion accessibility for high-performance organic electrochemical transistors.

High-performance n-type organic mixed ionic-electronic conductors (OMIECs) are essential for advancing complementary circuits based on organic electrochemical transistors (OECTs). Despite significant progress, current n-type OMIECs often exhibit lower transconductance and slower response times compared to their p-type counterparts, limiting the development of OECT-based complementary circuits. Optimizing the conjugated backbone and side chain structures of OMIECs is critical for enhancing both ion and electron transport efficiencies while maintaining a delicate balance between the two. In this study, hydrophilic polyethylene glycol (PEG) side chains were incorporated into the highly conductive n-type polymer poly(3,7-dihydrobenzo[1,2-b:4,5-b']difuran-2,6-dione) (PBFDO) backbone to achieve this goal. The incorporation of PEG chains improved ion accessibility, and by adjusting the PEG content, the electronic and ionic transport properties were fine-tuned, ultimately enhancing the performance of OECTs and related p-n complementary circuits. The n-type OECTs based on PBFDO-PEG50wt% demonstrated exceptional transfer characteristics, including a transient response time (τON) as low as 72 µs, a high geometry-normalized transconductance exceeding 400 S cm-1, and an impressive µC* value surpassing 720 F cm-1 V-1 s-1. Notably, the use of PBFDO-PEG50wt% in a complementary inverter resulted in a voltage gain of 20 V/V, more than five times higher than that achieved with unmodified PBFDO (<4 V/V). These findings highlight the importance of balancing electron and ion transport characteristics in OMIECs to achieve high performance in OECTs and their associated circuits, and they validate PEG decoration as an effective approach.

Highly sensitive detection of malaria biomarker through matching channel and gate capacitance of integrated organic electrochemical transistors.

Organic electrochemical transistors (OECTs) possess versatile advantages for biochemical and electrophysiological applications due to electrochemical gating and ion-to-electron conversion capability. Although OECTs have been successfully applied for biochemical sensing, the effect of relative capacitance for specific sensing events is still unclear. In the present work, we design integrated interdigitated OECTs (iOECTs) with on-plane gold gate and different channel geometries for point-of-care diagnosis of malaria using aptamer as receptor. The transconductance of the iOECTs gated with micro-size gold electrodes decreased with increasing the channel thicknesses, especially for devices with large channel areas, which is inconsistent with devices gated by typical Ag/AgCl electrodes, attributing to the limited gating efficiency of the micro-size gate electrode. The capacitance of gate electrode was heavily suppressed by receptors but increased with the incubation of targets. In addition, the integrated iOECTs with thin channels exhibited superior sensitivity for malaria detection with the detection limit as low as 3.2 aM, much lower than their thick channel counterpart and other state-of-the-art biosensors. These deviations could be caused by the high relative capacitances, with respect to the gate and channel capacitance (Cg/Cch), resulting in a high gate potential drop over the organic channel and thus entirely gating on the thin channel device. These findings provide guidance to optimize the geometry of OECT devices with on-chip integrated gates and the fabrication of miniaturized OECTs for biosensing applications.

Influence of Interaction between Electrolyte with Side-Chain Free Conjugated Polymer on the Performance of Organic Electrochemical Transistors.

Organic electrochemical transistors (OECTs) offer significant advantages in electrophysiological applications, primarily due to their ability to facilitate ionic-to-electronic conversion and establish a direct interface with the surrounding aqueous environments by using organic mixed ionic-electronic conductors. This study employs a side-chain free n-type conducting polymer, poly(benzodifurandione) (PBFDO), as the channel material in OECTs to scrutinize the interplay between various ion concentrations in electrolytes and the conjugated polymer and to assess their subsequent impact on device performance. Our findings reveal that PBFDO-based OECTs demonstrate superior transfer characteristics, attributed to their high conductivity and remarkable stability in aqueous solutions. Interestingly, the ion concentration does not alter the electronic band structure of PBFDO during the doping process, but a high-salt-concentration electrolyte could accelerate the electrochemical process compared to its counterparts. Furthermore, the diluted solution significantly enhances the surface roughness and decreases the crystalline coherence length of the film compared with concentrated solutions. A quantitative analysis utilizing an electrochemical quartz crystal microbalance discloses that the electrolyte ions penetrate the PBFDO film, inducing the absorption of a fraction of water molecules, which is pronounced in diluted solutions and negligible in their concentrated counterparts. This notable swelling of the polymer in diluted solutions potentially hampers the transport of charge carriers, consequently diminishing the OECT performance. This research elucidates a direct correlation between microstructure alterations and device performance during operation, paving the way for the optimization of ionic and electronic conductivity in polymers to foster the development of high-performance organic electronic devices.

Electrospun Donor/Acceptor Nanofibers for Efficient Photocatalytic Hydrogen Evolution.

We prepared a series of one-dimensional conjugated-material-based nanofibers with different morphologies and donor/acceptor (D/A) compositions by electrospinning for efficient photocatalytic hydrogen evolution. It was found that homogeneous D/A heterojunction nanofibers can be obtained by electrospinning, and the donor/acceptor ratio can be easily controlled. Compared with the single-component-based nanofibers, the D/A-based nanofibers showed a 34-fold increase in photocatalytic efficiency, attributed to the enhanced exciton dissociation in the nanofibrillar body. In addition, the photocatalytic activity of these nanofibers can be easily optimized by modulating the diameter. The results show that the diameter of the nanofibers can be conveniently controlled by the electrospinning feed rate, and the photocatalytic effect increases with decreasing fiber diameter. Consequently, the nanofibers with the smallest diameter exhibit the most efficient photocatalytic hydrogen evolution, with the highest release rate of 24.38 mmol/(gh). This work provides preliminary evidence of the advantages of the electrospinning strategy in the construction of D/A nanofibers with controlled morphology and donor/acceptor composition, enabling efficient hydrogen evolution.

Synergistic Effect of Oxoammonium Salt and Its Counterions for Fabricating Organic Electrochemical Transistors with Low Power Consumption.

The state-of-the-art poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)-based organic electrochemical transistors (OECTs) are gaining importance for a variety of biological applications due to their mixed electronic and ionic conductivities featuring ion-to-electron conversion. A low operation voltage without sacrificing device performance is desired to realize long-term monitoring of biological activities. In the present work, oxoammonium salts with two different counterions (TEMPO+X-, where TEMPO = 2,2,6,6-tetramethylpiperidine-1-oxoammonium; X = Br- and TFSI-) are employed as secondary dopants to modulate the device performance. Both oxoammonium salts feature a distinct dopant concentration-dependent doping effect, allowing precise control in improving the performance of OECTs. A zero-gate bias, corresponding to the maximum transconductance, and a low threshold voltage are realized by optimizing the dopant concentrations. In addition, TEMPO+TFSI- dopant exerts great capability in modulating the work function and in morphology reconstruction of PEDOT:PSS, ensuring a well-matched work function at the gold electrode-channel material interface and condensed microstructure stacking with an edge-on orientation in the doped PEDOT:PSS films. The synergistic effect of TEMPO and the TFSI- counterion endows the device with superior performance to its counterparts due to the resultant higher µC* figure, benefiting from the efficient injection/extraction of holes at the interface and enhanced intra- and inter-chain carrier transport. The excellent device performance makes the OECT a promising neuromorphic device to mimic basic brain functions.

Delineating charge and capacitance transduction in system-integrated graphene-based BioFETs used as aptasensors for malaria detection.

Despite significant eradication efforts, malaria remains a persistent infectious disease with high mortality due to the lack of efficient point-of-care (PoC) screening solutions required to manage low-density asymptomatic parasitemia. In response, we demonstrate a quantitative electrical biosensor based on system-integrated two-dimensional field-effect transistors (2DBioFETs) of reduced graphene oxide (rGO) as transducer for high sensitivity screening of the main malaria biomarker, Plasmodium falciparum lactate dehydrogenase (PfLDH). The 2DBioFETs were biofunctionalized with pyrene-modified 2008s aptamers as specific PfLDH receptors. While we systematically optimize biosensor interface for optimal performance, aptamer-protein transduction at 2DBioFETs is elucidated based on delineation of charge and capacitance in an updated analytical model for two-dimensional rGO/biofunctional layer/electrolyte (2DiBLE) interfaces. Our 2DBioFET-aptasensors display a limit-of-detection down to 0.78 fM (0.11 pg/mL), dynamic ranges over 9 orders of magnitude (subfemto to submicromolar), high sensitivity, and selectivity in human serum validating their diagnostic potential as rapid PoC tests for malarial management.

PEDOT:PSS-Based Bioelectronic Devices for Recording and Modulation of Electrophysiological and Biochemical Cell Signals.

To understand the physiology and pathology of electrogenic cells and the corresponding tissue in their full complexity, the quantitative investigation of the transmission of ions as well as the release of chemical signals is important. Organic (semi-) conducting materials and in particular organic electrochemical transistor are gaining in importance for the investigation of electrophysiological and recently biochemical signals due to their synthetic nature and thus chemical diversity and modifiability, their biocompatible and compliant properties, as well as their mixed electronic and ionic conductivity featuring ion-to-electron conversion. Here, the aim is to summarize recent progress on the development of bioelectronic devices utilizing polymer polyethylenedioxythiophene: poly(styrene sulfonate) (PEDOT:PSS) to interface electronics and biological matter including microelectrode arrays, neural cuff electrodes, organic electrochemical transistors, PEDOT:PSS-based biosensors, and organic electronic ion pumps. Finally, progress in the material development is summarized for the improvement of polymer conductivity, stretchability, higher transistor transconductance, or to extend their field of application such as cation sensing or metabolite recognition. This survey of recent trends in PEDOT:PSS electrophysiological sensors highlights the potential of this multifunctional material to revolve current technology and to enable long-lasting, multichannel polymer probes for simultaneous recordings of electrophysiological and biochemical signals from electrogenic cells.

Dodecacyclic-Fused Electron Acceptors with Multiple Electron-Deficient Units for Efficient Organic Solar Cells.

Fused aromatic cores in non-fullerene electron acceptors (NFEAs) play a significant role in determining their optoelectronic properties and photovoltaic performance. In this work, a dodecacyclic-fused core with three electron-deficient units is synthesized through a double intramolecular Cadogan reduction cyclization. Terminal groups with different halogen substitution (F or Cl) are grafted onto the dodecacyclic-fused core to afford MS-4F and MS-4Cl, both of which showed strong and broad absorption, narrow bandgaps around 1.40 eV, and variable molecular packing model in pristine and blend films. Photovoltaic performance of solar cells containing MS-4F and MS-4Cl as NFEAs were investigated with resultant power conversion efficiencies (PCEs) of 11.75 % and 11.79 %, respectively. The mechanism study indicates that both of PBDB-T : MS-4F- and PBDB-T : MS-4Cl-based devices displayed high hole and electron mobility values, efficient charge transfer, and low charge recombination etc. These results indicate that designing multiple-fused aromatic cores with multiple electron-deficient units is a promising strategy to obtain high-performance NFEAs.

Label-Free Split Aptamer Sensor for Femtomolar Detection of Dopamine by Means of Flexible Organic Electrochemical Transistors.

The detection of chemical messenger molecules, such as neurotransmitters in nervous systems, demands high sensitivity to measure small variations, selectivity to eliminate interferences from analogues, and compliant devices to be minimally invasive to soft tissue. Here, an organic electrochemical transistor (OECT) embedded in a flexible polyimide substrate is utilized as transducer to realize a highly sensitive dopamine aptasensor. A split aptamer is tethered to a gold gate electrode and the analyte binding can be detected optionally either via an amperometric or a potentiometric transducer principle. The amperometric sensor can detect dopamine with a limit of detection of 1 µM, while the novel flexible OECT-based biosensor exhibits an ultralow detection limit down to the concentration of 0.5 fM, which is lower than all previously reported electrochemical sensors for dopamine detection. The low detection limit can be attributed to the intrinsic amplification properties of OECTs. Furthermore, a significant response to dopamine inputs among interfering analogues hallmarks the selective detection capabilities of this sensor. The high sensitivity and selectivity, as well as the flexible properties of the OECT-based aptasensor, are promising features for their integration in neuronal probes for the in vitro or in vivo detection of neurochemical signals.

Amplification of aptamer sensor signals by four orders of magnitude via interdigitated organic electrochemical transistors.

Electrochemical aptamer receptor/transducer systems are key elements of emerging E-AB sensors (aptasensor) used for the detection of various kinds of targets. However, the performance of these amperometric sensors is often limited by the low density of receptors attached to the sensor surface and high background signals. In the present work, interdigitated organic electrochemical transistors (iOECT) were used as a transducer to enhance the sensitivity and dynamic detection range of aptasensors. Therefore, the electrode of an amperometric sensor was utilized as gate electrode to operate the iOECT. This device was used to detect the low weight target molecule adenosine triphosphate (ATP), a common biomarker, which plays an important role for cardiovascular, neurodegenerative, and immune deficiency diseases. The novel aptasensor can selectively detect ATP with ultrahigh sensitivity down to the concentration of 10 pM, which is four orders of magnitude lower than the detection limit of the same aptasensor using an amperometric transducer principle (limit-of-detection of 106 nM) and most other previously reported electrochemical sensors. Furthermore, sensor regeneration was demonstrated, which facilitates reusability of OECT aptasensors. The small device size in combination with high transconductances paves the way for the development of highly sensitive integrated micro-biosensors for point-of-care applications.

High Performance Flexible Organic Electrochemical Transistors for Monitoring Cardiac Action Potential.

Flexible and transparent electronic devices possess crucial advantages over conventional silicon based systems for bioelectronic applications since they are able to adapt to nonplanar surfaces, cause less chronic immunoreactivity, and facilitate easy optical inspection. Here, organic electrochemical transistors (OECTs) are embedded in a flexible matrix of polyimide to record cardiac action potentials. The wafer-scale fabricated devices exhibit transconductances (12 mS V-1 ) and drain-source on-to-off current ratios (≈105 ) comparable to state of the art nonflexible and superior to other reported flexible OECTs. The transfer characteristics of the devices are preserved even after experiencing extremely high bending strain and harsh crumpling. A sub-micrometer poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) layer results in a fast transport of ions between the electrolyte and the polymer channel characterized by a cut-off frequency of 1200 Hz. Excellent device performance is proved by mapping the propagation of cardiac action potentials with high signal-to-noise ratio. These results demonstrate that the electrical performance of flexible OECTs can compete with hard-material-based OECTs and thus potentially be used for in vivo applications.

Nucleation ability of thermally reduced graphene oxide for polylactide: role of size and structural integrity.

Following our previous work on graphene oxide-induced polylactide (PLA) crystallization [Macromolecules 2010, 43, 5000-5008], in the current work, we further revealed the role of size and structural integrity of thermally reduced graphene oxide (RGO) in PLA crystallization. RGO nanoplatelets with different architectures were obtained via bath and probe ultrasound (RGOw and RGOp). The average size of RGO decreased substantially with ultrasound intensity and time, where the generation of RGO edges constituted the translocation of functional group sites from in-plane to edges. The formation of sp(3)-configuration dominated in RGOw, whereas the partial recovery of sp(2)-configuration occurred in RGOp, giving rise to either the escalation of sp(3)/sp(2) ratio for RGOw or retrogradation of that for RGOp. Isothermal crystallization kinetics of PLA nanocomposites containing RGOw and RGOp was determined by in situ synchrotron wide-angle X-ray diffraction. The induction period and overall crystallization rate of PLA/RGOw nanocomposites were strengthened with diminishing platelet size because of more nucleation sites encouraged by redistribution of functional groups. However, the adverse situation was found in PLA/RGOp nanocomposites. The observed phenomenon was ascribed to the disruption of the internal structure, i.e., the C═C sp(2) π-bond network, which deteriorated the CH-π interaction between PLA and RGO. These results conclusively suggested that the size and structural integrity of RGO had a concerted effort to determine the final nucleation ability of RGO dispersed by ultrasound.

Graphene Oxide Nanosheet Induced Intrachain Conformational Ordering in a Semicrystalline Polymer.

The physical origin of graphene oxide nanosheet (GONS)-driven polymer crystallization was studied from the perspective of intrachain conformational ordering. Time-resolved Fourier-transform infrared spectroscopy indicated that both conformational ordering and crystallization of isotactic polypropylene (iPP) were obviously accelerated by the presence of GONSs, indicating their efficient nucleation activity for iPP crystallization. Furthermore, the ordering of long helical segments occurred prior to the crystallization of iPP, as revealed by two-dimensional correlation infrared analysis. Compared to pure bulk system, the presence of GONSs was in favor of the formation of long ordering segments, especially at the early stage, accompanied by considerable enhancement of the crystallization kinetics. GONS-driven iPP crystallization was suggested to be attributed to this GONS-induced intrachain conformational ordering.