ABSTRACT
A rapidly growing interest in organic bioelectronic applications has spurred the development of a wide variety of organic mixed ionic-electronic conductors. While these new mixed conductors have enabled the community to interface organic electronics with biological systems and efficiently transduce biological signals (ions) into electronic signals, the current materials selection does not offer sufficient selectivity towards specific ions of biological relevance without the use of auxiliary components such as ion-selective membranes. Here, we present the molecular design of an n-type (electron-transporting) perylene diimide semiconductor material decorated with pendant oligoether groups to facilitate interactions with cations such as Na+ and K+. Using the cyclic 15-crown-5 oligoether motif, we find that the resulting mixed conductor PDI-crown displays a strong dependence on the size of the electrolyte cation when tested in an organic electrochemical transistor configuration. In stark contrast to the low current response on the order of 1 µA observed with aqueous sodium chloride, a nearly 200-fold increase in current is observed with aqueous potassium chloride. We ascribe the high selectivity to extended molecular aggregation and therefore efficient charge transport in the presence of K+ due to a favourable sandwich-like structure between two adjacent 15-crown-5 motifs and the potassium ion.
ABSTRACT
Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a benchmark hole-transporting (p-type) polymer that finds applications in diverse electronic devices. Most of its success is due to its facile synthesis in water, exceptional processability from aqueous solutions, and outstanding electrical performance in ambient. Applications in fields like (opto-)electronics, bioelectronics, and energy harvesting/storage devices often necessitate the complementary use of both p-type and n-type (electron-transporting) materials. However, the availability of n-type materials amenable to water-based polymerization and processing remains limited. Herein, we present a novel synthesis method enabling direct polymerization in water, yielding a highly conductive, water-processable n-type conjugated polymer, namely, poly[(2,2'-(2,5-dihydroxy-1,4-phenylene)diacetic acid)-stat-3,7-dihydrobenzo[1,2-b:4,5-b']difuran-2,6-dione] (PDADF), with remarkable electrical conductivity as high as 66 S cm-1, ranking among the highest for n-type polymers processed using green solvents. The new n-type polymer PDADF also exhibits outstanding stability, maintaining 90% of its initial conductivity after 146 days of storage in air. Our synthetic approach, along with the novel polymer it yields, promises significant advancements for the sustainable development of organic electronic materials and devices.
ABSTRACT
Chemical doping is an important approach to manipulating charge-carrier concentration and transport in organic semiconductors (OSCs)1-3 and ultimately enhances device performance4-7. However, conventional doping strategies often rely on the use of highly reactive (strong) dopants8-10, which are consumed during the doping process. Achieving efficient doping with weak and/or widely accessible dopants under mild conditions remains a considerable challenge. Here, we report a previously undescribed concept for the photocatalytic doping of OSCs that uses air as a weak oxidant (p-dopant) and operates at room temperature. This is a general approach that can be applied to various OSCs and photocatalysts, yielding electrical conductivities that exceed 3,000 S cm-1. We also demonstrate the successful photocatalytic reduction (n-doping) and simultaneous p-doping and n-doping of OSCs in which the organic salt used to maintain charge neutrality is the only chemical consumed. Our photocatalytic doping method offers great potential for advancing OSC doping and developing next-generation organic electronic devices.
ABSTRACT
Water-based conductive inks are vital for the sustainable manufacturing and widespread adoption of organic electronic devices. Traditional methods to produce waterborne conductive polymers involve modifying their backbone with hydrophilic side chains or using surfactants to form and stabilize aqueous nanoparticle dispersions. However, these chemical approaches are not always feasible and can lead to poor material/device performance. Here, we demonstrate that ground-state electron transfer (GSET) between donor and acceptor polymers allows the processing of water-insoluble polymers from water. This approach enables macromolecular charge-transfer salts with 10,000× higher electrical conductivities than pristine polymers, low work function, and excellent thermal/solvent stability. These waterborne conductive films have technological implications for realizing high-performance organic solar cells, with efficiency and stability superior to conventional metal oxide electron transport layers, and organic electrochemical neurons with biorealistic firing frequency. Our findings demonstrate that GSET offers a promising avenue to develop water-based conductive inks for various applications in organic electronics.
ABSTRACT
Organic electrochemical transistors (OECTs) are a rapidly advancing technology that plays a crucial role in the development of next-generation bioelectronic devices. Recent advances in p-type/n-type organic mixed ionic-electronic conductors (OMIECs) have enabled power-efficient complementary OECT technologies for various applications, such as chemical/biological sensing, large-scale logic gates, and neuromorphic computing. However, ensuring long-term operational stability remains a significant challenge that hinders their widespread adoption. While p-type OMIECs are generally more stable than n-type OMIECs, they still face limitations, especially during prolonged operations. Here, we demonstrate that simple methylation of the pyrrole-benzothiazine-based (PBBT) ladder polymer backbone results in stable and high-performance p-type OECTs. The methylated PBBT (PBBT-Me) exhibits a 25-fold increase in OECT mobility and an impressive 36-fold increase in µC* (mobility × volumetric capacitance) compared to the non-methylated PBBT-H polymer. Combining the newly developed PBBT-Me with the ladder n-type poly(benzimidazobenzophenanthroline) (BBL), we developed complementary inverters with a record-high DC gain of 194 V V-1 and excellent stability. These state-of-the-art complementary inverters were used to demonstrate leaky integrate-and-fire type organic electrochemical neurons (LIF-OECNs) capable of biologically relevant firing frequencies of about 2 Hz and of operating continuously for up to 6.5 h. This achievement represents a significant improvement over previous results and holds great potential for developing stable bioelectronic circuits capable of in-sensor computing.
ABSTRACT
Biointegrated neuromorphic hardware holds promise for new protocols to record/regulate signalling in biological systems. Making such artificial neural circuits successful requires minimal device/circuit complexity and ion-based operating mechanisms akin to those found in biology. Artificial spiking neurons, based on silicon-based complementary metal-oxide semiconductors or negative differential resistance device circuits, can emulate several neural features but are complicated to fabricate, not biocompatible and lack ion-/chemical-based modulation features. Here we report a biorealistic conductance-based organic electrochemical neuron (c-OECN) using a mixed ion-electron conducting ladder-type polymer with stable ion-tunable antiambipolarity. The latter is used to emulate the activation/inactivation of sodium channels and delayed activation of potassium channels of biological neurons. These c-OECNs can spike at bioplausible frequencies nearing 100 Hz, emulate most critical biological neural features, demonstrate stochastic spiking and enable neurotransmitter-/amino acid-/ion-based spiking modulation, which is then used to stimulate biological nerves in vivo. These combined features are impossible to achieve using previous technologies.
Subject(s)
Electrons , Polymers , Neurons/physiology , Signal Transduction , SemiconductorsABSTRACT
Ladder-type conjugated polymers exhibit a remarkable performance in (opto)electronic devices. Their double-stranded planar structure promotes an extended π-conjugation compared to inter-ring-twisted analogues, providing an excellent basis for exploring the effects of charge localization on polaron formation. Here, we investigated alkali-metal n-doping of the ladder-type conjugated polymer (polybenzimidazobenzophenanthroline) (BBL) through detailed in situ spectroscopic and electrical characterizations. Photoelectron spectroscopy and ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy indicate polaron formation upon potassium (K) doping, which agrees well with theoretical predictions. The semiladder BBB displays a similar evolution in the valence band with the appearance of two new features below the Fermi level upon K-doping. Compared to BBL, distinct differences appear in the UV-vis-NIR spectra due to more localized polaronic states in BBB. The high conductivity (2 S cm-1) and low activation energy (44 meV) measured for K-doped BBL suggest disorder-free polaron transport. An even higher conductivity (37 S cm-1) is obtained by changing the dopant from K to lithium (Li). We attribute the enhanced conductivity to a decreased perturbation of the polymer nanostructure induced by the smaller Li ions. These results highlight the importance of polymer chain planarity and dopant size for the polaronic state in conjugated polymers.
ABSTRACT
Organic electrochemical transistors (OECTs) hold promise for developing a variety of high-performance (bio-)electronic devices/circuits. While OECTs based on p-type semiconductors have achieved tremendous progress in recent years, n-type OECTs still suffer from low performance, hampering the development of power-efficient electronics. Here, it is demonstrated that fine-tuning the molecular weight of the rigid, ladder-type n-type polymer poly(benzimidazobenzophenanthroline) (BBL) by only one order of magnitude (from 4.9 to 51 kDa) enables the development of n-type OECTs with record-high geometry-normalized transconductance (gm,norm ≈ 11 S cm-1 ) and electron mobility × volumetric capacitance (µC* ≈ 26 F cm-1 V-1 s-1 ), fast temporal response (0.38 ms), and low threshold voltage (0.15 V). This enhancement in OECT performance is ascribed to a more efficient intermolecular charge transport in high-molecular-weight BBL than in the low-molecular-weight counterpart. OECT-based complementary inverters are also demonstrated with record-high voltage gains of up to 100 V V-1 and ultralow power consumption down to 0.32 nW, depending on the supply voltage. These devices are among the best sub-1 V complementary inverters reported to date. These findings demonstrate the importance of molecular weight in optimizing the OECT performance of rigid organic mixed ionic-electronic conductors and open for a new generation of power-efficient organic (bio-)electronic devices.
ABSTRACT
Conducting polymers, such as the p-doped poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), have enabled the development of an array of opto- and bio-electronics devices. However, to make these technologies truly pervasive, stable and easily processable, n-doped conducting polymers are also needed. Despite major efforts, no n-type equivalents to the benchmark PEDOT:PSS exist to date. Here, we report on the development of poly(benzimidazobenzophenanthroline):poly(ethyleneimine) (BBL:PEI) as an ethanol-based n-type conductive ink. BBL:PEI thin films yield an n-type electrical conductivity reaching 8 S cm-1, along with excellent thermal, ambient, and solvent stability. This printable n-type mixed ion-electron conductor has several technological implications for realizing high-performance organic electronic devices, as demonstrated for organic thermoelectric generators with record high power output and n-type organic electrochemical transistors with a unique depletion mode of operation. BBL:PEI inks hold promise for the development of next-generation bioelectronics and wearable devices, in particular targeting novel functionality, efficiency, and power performance.
ABSTRACT
Root-knot nematodes (Meloidogyne spp.) are the most destructive group of plant-parasitic nematodes. Plants infected by Meloidogyne spp. develop above-ground symptoms, stunting, yellowing, nutrient deficiencies, and gall formations with typical hook-shaped root tips. Infected plants experience yield losses. During 2018-2019 survey, leaf chlorosis rice plants were found in 206 fields of 67 counties in Guangxi, China, around 30 days after transplanting. Galls and hooked tips on the roots and pear-shaped females were observed. About 32.04% of fields were infested with the nematode. The nematodes were identified as Meloidogyne graminicola base on morphological and molecular analysis. To the best of our knowledge, this is the first report of M. graminicola on rice plants in Guangxi, China. The results of this study urge the discovery of resistant cultivars and the development of management strategies.
ABSTRACT
OBJECTIVE: To explore the epidemiological characters of severe acute respiratory syndrome (SARS) in Sichuan province in order to provide evidence for prevention and control. METHODS: To generate data on SARS in Sichuan province through descriptive and analytical studies on time, geographic distribution, population, source of infection, the way of case finding, symptom, diagnosis and treatment of the cases. RESULTS: The peak of the epidemic last from April 16 to May 7. The number of cases in Luzhou and Guangyuan cities took up 60% of the total. Mobile population occupied 68% of the cases. Most of the patients were above the age of 20 with a sex ratio of 1.5:1 (m/f). 80% of the cases had a history of working in Guangdong province and recently returned to their hometowns. The main symptoms and signs of the SARS patients would include fever, cough and chest X-ray changes. CONCLUSION: All cases were imported. Fluctuation of the epidemics was mainly affected by the mobility of working population who recently returned to their hometowns. Measures concerning the prevention and control of the epidemics would mainly target on the isolation of confirmed and suspected patients who might serve as the sources of infection through setting up quarantine station, assigned hospitals and special 'fever-clinics'.