Single-crystal-conjugated polymers with extremely high electron sensitivity through template-assisted in situ polymerization

2D Conjugated Polymer Thin Films for Organic Electronics: Opportunities and Challenges

2D conjugated polymers (2DCPs) possess extended in-plane π-conjugated lattice and out-of-plane π-π stacking, which results in enhanced electronic performance and potentially unique band structures. These properties, along with predesignability, well-defined channels, easy postmodification, and order structure attract extensive attention from material science to organic electronics. In this review, the recent advance in the interfacial synthesis and conductivity tuning strategies of 2DCP thin films, as well as their application in organic electronics is summarized. Furthermore, it is shown that, by combining topology structure design and targeted conductivity adjustment, researchers have fabricated 2DCP thin films with predesigned active groups, highly ordered structures, and enhanced conductivity. These films exhibit great potential for various thin-film organic electronics, such as organic transistors, memristors, electrochromism, chemiresistors, and photodetectors. Finally, the future research directions and perspectives of 2DCPs are discussed in terms of the interfacial synthetic design and structure engineering for the fabrication of fully conjugated 2DCP thin films, as well as the functional manipulation of conductivity to advance their applications in future organic electronics.

A Feasible Strategy for High-Performance Aqueous Zinc-Ion Batteries: Introducing Conducting Polymer

Aqueous zinc ion batteries (AZIBs) offer great potential for large-scale energy storage because of their high safety, low cost and acceptable energy density. However, the cycle life of AZIBs is inevitably affected by parasitic reactions and dendritic growth caused by multiple factors such as electrode, electrolyte and separator, which pose significant obstacles to the practical application of AZIBs. To address these challenges, conducting polymer (CP) based materials have gained widespread attention in the realm of rechargeable batteries due to the adjustable band gap, controllable morphology, and excellent flexibility of CPs. In particular, CPs exhibit remarkable conductivity, low dimensionality, and doping characteristics, making them highly promising for integration into the AZIB system. In this review, the problems associated with the cathode, anode, electrolyte, and separator of AZIBs are discussed, and the application of CPs for their modification is summarized. The review provides a comprehensive analysis of the action mechanisms involved in the CP modification process and offers valuable insights for the design and development of CPs that can be effectively utilized in AZIBs. Additionally, the review presents a promising outlook of this research field, aiming to further advance the application of low-cost and high-performance CPs and their composites in AZIBs.

Precisely Controlled Polymerization of Two-Dimensional Conducting Polymers in Quasi-Liquid Layer Enables Ultrahigh Sensing Performance

Gas sensors based on conducting polymers offer great potential for high-performance room temperature applications due to their cost-effectiveness, high-sensitivity, and operational advantage. However, their current performance is limited by the deficiency of control in conventional polymerization methods, leading to poor crystallinity and inconsistent material properties. Here, the quasi-liquid layer (QLL) on the ice surface acts as a self-regulating nano-reactor for precise control of thermodynamics and kinetics in the polymerization, resulting in a 7.62 nm thick two-dimensional (2D) polyaniline (PANI) film matching the QLL thickness. The ultra-thin film optimizes the exposure of active sites, enhancing the detection of analyte gases at low concentrations. It is validated by fabricating a chemiresistive gas sensor with the 2D PANI film, demonstrating stable room-temperature detection of ammonia down to 10 ppt in ambient air with an impressive 10% response. This achievement represents the highest sensitivity among sensors of this kind while maintaining excellent selectivity and repeatability. Moreover, the QLL-controlled polymerization strategy offers an alternative route for precise control of the polymerization process for conducting polymers, enabling the creation of advanced materials with enhanced properties.

Progress on Transition Metal Ions Dissolution Suppression Strategies in Prussian Blue Analogs for Aqueous Sodium-/Potassium-Ion Batteries

Aqueous sodium-ion batteries (ASIBs) and aqueous potassium-ion batteries (APIBs) present significant potential for large-scale energy storage due to their cost-effectiveness, safety, and environmental compatibility. Nonetheless, the intricate energy storage mechanisms in aqueous electrolytes place stringent requirements on the host materials. Prussian blue analogs (PBAs), with their open three-dimensional framework and facile synthesis, stand out as leading candidates for aqueous energy storage. However, PBAs possess a swift capacity fade and limited cycle longevity, for their structural integrity is compromised by the pronounced dissolution of transition metal (TM) ions in the aqueous milieu. This manuscript provides an exhaustive review of the recent advancements concerning PBAs in ASIBs and APIBs. The dissolution mechanisms of TM ions in PBAs, informed by their structural attributes and redox processes, are thoroughly examined. Moreover, this study delves into innovative design tactics to alleviate the dissolution issue of TM ions. In conclusion, the paper consolidates various strategies for suppressing the dissolution of TM ions in PBAs and posits avenues for prospective exploration of high-safety aqueous sodium-/potassium-ion batteries.

Preparation of a polymer nanocomposite via the polymerization of pyrrole : biphenyldisulfonic acid : pyrrole as a two-monomer-connected precursor on MoS2 for electrochemical energy storage

We prepared a poly(pyrrole : biphenyldisulfonic acid : pyrrole (Py:BPDSA:Py)) nanocomposite of molybdenum disulfide (MoS₂), P(Py:BPDSA:Py)-MoS₂, with high crystallinity. The composite is synthesized by oxidative polymerization of Py:BPDSA:Py as a two-monomer-connected precursor (TMCP) linked by ionic bonding on a molybdenum disulfide (MoS₂) monolayer. The chemical, structural and morphological characterization of this composite is confirmed by Raman spectroscopy, FT-IR, X-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), and scanning electron microscopy (SEM). The crystal structure is analysed by X-ray diffraction (XRD) and high-voltage electron microscopy (HVEM), which shows a face-centered cubic (FCC) crystal structure for the composite. Nitrogen adsorption-desorption isotherms show an improved specific surface area (91.3 m² g^-1). The electrochemical properties of the composite with a unique crystal structure and a large specific surface area are analysed through cyclic voltammetry (CV), which shows a specific capacitance of 681 F g^-1 demonstrating that the composite can be used as an efficient electrode active material for electrochemical energy storage systems.

Enhanced Ion Conduction via Epitaxially Polymerized Two-Dimensional Conducting Polymer for High-Performance Cathode in Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) are one of the promising choices for the future large-scale grid energy storage, in which Mn-based cathode materials have the advantages of low cost and environmental friendliness. However, their capacity delivery and cycling stability are limited by the large bulk-induced incomplete zincation and structure pulverization. Here, we develop a strategy of epitaxial polymerization in the liquid phase to fabricate two-dimensional (2D) MnO_x/polypyrrole nanosheets to enhance the zinc-ion storage by realizing the efficient utilization of active materials and improving the structural stability via a polymerized framework. An ultrahigh capacity of 408 mAh g^-1 is demonstrated at 1C rate, and an excellent capacity retention of 78% is realized after 2800 cycles at 5C rate for the AZIB. Electrochemical and morphological characterizations reveal that the unique 2D structure contributes to both the electron/ion conductivity and structural stability. The epitaxial polymerization of the conducting polymer in the liquid phase provides a new perspective to the synthesis of high-performance electrode materials and 2D conducting polymers.

Facile Wearable Vapor/Liquid Amphibious Methanol Sensor

Detection of methanol is a significant segment for body health and work safety in the production of chemical industry. However, there hardly exists highly selective methanol detection system with green environment for vapor or liquid adaptability, as well as large linear relationship. A facile wearable vapor/liquid amphibious electrochemical sensor for monitoring methanol has been carried out for the first time in this Article. This wearable methanol sensor was fabricated by using a simple screen-printing technology for accomplishing a microdevice platform, showing good linear relationship, high selectivity (multiple volatile chemical compounds), reliable repeatability, good stability, and excellent stretching and bending performance (nitrile glove-based sensor) without pretreatment or adding any polymers into inks. Owing to its good environmental adaptability of vapor or liquid and various sensing behaviors (high sensitivity and wide linear range) by being modified with different content of platinum catalyst, this methanol sensor would have tremendous potential application for environmental monitoring on smart wearable devices when employed based on various platforms (such as PET, cotton, and nitrile gloves).

Engineering Fast Ion Conduction and Selective Cation Channels for a High-Rate and High-Voltage Hybrid Aqueous Battery

The rechargeable aqueous metal-ion battery (RAMB) has attracted considerable attention due to its safety, low costs, and environmental friendliness. Yet the poor-performance electrode materials lead to a low feasibility of practical application. A hybrid aqueous battery (HAB) built from electrode materials with selective cation channels could increase the electrode applicability and thus enlarge the application of RAMB. Herein, we construct a high-voltage K-Na HAB based on K₂ FeFe(CN)₆ cathode and carbon-coated NaTi₂ (PO₄ )₃ (NTP/C) anode. Due to the unique cation selectivity of both materials and ultrafast ion conduction of NTP/C, the hybrid battery delivers a high capacity of 160 mAh g^-1 at a 0.5 C rate. Considerable capacity retention of 94.3 % is also obtained after 1000 cycles at even 60 C rate. Meanwhile, high energy density of 69.6 Wh kg^-1 based on the total mass of active electrode materials is obtained, which is comparable and even superior to that of the lead acid, Ni/Cd, and Ni/MH batteries.

Touching the theoretical capacity: synthesizing cubic LiTi2(PO4)3/C nanocomposites for high-performance lithium-ion battery

A cubic LiTi2(PO4)3/C composite is successfully prepared via a simple solvothermal method and further glucose-pyrolysis treatment. The as-fabricated LTP/C material delivers an ultra-high reversible capacity of 144 mA h g-1 at 0.2C rate, which is the highest ever reported, and shows considerable performance improvement compared with before. Combining this with the stable cycling performance and high rate capability, such material has a promising future in practical application.

An open holey structure enhanced rate capability in a NaTi2(PO4)3/C nanocomposite and provided ultralong-life sodium-ion storage

Sodium-ion battery (SIB) technology is competitive in the fields of transportation and grid storage, which require electrode materials showing rapid energy conversion (high rate capability) and long cycle life. In this work, a NaTi₂(PO₄)₃/C (NTP/C) nanocomposite with an open holey-structured framework was successfully prepared for the first time using a solvothermal reaction followed by pyrolysis. The nanocomposite realized fast sodium-ion transport and thus preferable battery performances. Within the wide rate range of 0.5-50C, only a very small decrease in capacity from 124 to 120 mA h g^-1 was observed. A high discharge capacity of 103 mA h g^-1 (88.3% retention of the 1st cycle) was delivered even after 10 000 cycles at an ultrahigh rate of 50C without any obvious morphological change and without structural pulverization. Forming open channels for ion transport proved to contribute to such performance enhancement and therefore has the potential to become a universal model for the development of sustainable electrode materials in SIBs and other battery systems.

Auto-generated iron chalcogenide microcapsules ensure high-rate and high-capacity sodium-ion storage

Sodium-ion batteries (SIBs) are regarded as promising alternative energy-storage devices to lithium-ion batteries (LIBs). However, the trade-off of between energy density and power density under high mass-loading conditions restricts the application of SIBs. Herein, we synthesized an FeSe@FeS material via a facile solid-state reaction. A microcapsule architecture was spontaneously achieved in this process, which facilitated electron transport and provided stable diffusion paths for Na ions. The FeSe@FeS material exhibits a high capacity retention (485 mA h g^-1 at 3 A g^-1 after 1400 cycles) and superior rate capability (230 mA h g^-1 at 10 A g^-1 after 1600 cycles) in the half-cell test. Furthermore, superior cycling stability is achieved in the full-cell test. The high mass-loaded FeSe@FeS electrodes (8 mg cm^-2) realize a high areal capacity retention of 2.8 mA h cm^-2 and high thermal stability.

Unprecedented sensitivity towards pressure enabled by graphene foam

Reduced graphene oxide foam (RGOF)-based pressure sensors have been fabricated through the combination of ultrasonic dispersion and freeze-drying methods. Due to the maintenance of the highly disordered structure of the ultrasonic dispersed graphene oxides before the freezing process, the RGOF sensors demonstrated an ultra-high sensitivity of 22.8 kPa^-1, an ultra-low detection limit of around 0.1 Pa, and a superior separation of 0.2-Pascal-scale difference.

Unique Reversible Conversion-Type Mechanism Enhanced Cathode Performance in Amorphous Molybdenum Polysulfide

A unique reversible conversion-type mechanism is reported in the amorphous molybdenum polysulfide (a-MoS_5.7) cathode material. The lithiation products of metallic Mo and Li₂S₂ rather than Mo and Li₂S species have been detected. This process could yield a high discharge capacity of 746 mAh g^-1. Characterizations of the recovered molybdenum polysulfide after the delithiaiton process manifests the high reversibility of the unique conversion reaction, in contrast with the general irreversibility of the conventional conversion-type mechanism. As a result, the a-MoS_5.7 electrodes deliver high cycling stability with an energy-density retention of 1166 Wh kg^-1 after 100 cycles. These results provide a novel model for the design of high-capacity and long-life electrode materials.

Size-tunable, highly sensitive microelectrode arrays enabled by polymer pen lithography

By combining polymer pen lithography (PPL) patterning with in situ polymerization, we report a straightforward and bottom-up approach for bench-top fabrication of microelectrode arrays (MEAs) with well-controlled dimensions. The as-fabricated MEAs can be used to electrodeposit prussian blue in situ and work as a biosensor for H₂O₂ with a detection limit as low as 5 nM at a sensitivity of 0.7 A cm^-2 M^-1.

Novel Metal Chalcogenide SnSSe as a High-Capacity Anode for Sodium-Ion Batteries

A novel layered SnSSe material is designed as a high-performance anode for sodium-ion batteries with characteristics of high capacity, superior cyclability, facile synthetic method, and large-scale production ability. The transformation from bulk SnSSe particles into closely packed nanoplate aggregates with greater resistance to structure pulverization and the partial pseudocapacitive capacity contribution may engender excellent cycling performance and rate capability.

High-Oriented Polypyrrole Nanotubes for Next-Generation Gas Sensor

Highly oriented PPy nanotubes are grown by in situ vapor phase polymerization within a nanoscale template under low temperature. As-fabricated PPy nanotubes are used for gas sensing, where an ultralow detection limit (0.05 ppb) and very fast response are achieved. Such an in situ mass-productive method for synthesizing highly oriented conducting polymers may pave a new step toward next-generation gas sensors.

Close-packed polymer crystals from two-monomer-connected precursors

The design of crystalline polymers is intellectually stimulating and synthetically challenging, especially when the polymerization of any monomer occurs in a linear dimension. Such linear growth often leads to entropically driven chain entanglements and thus is detrimental to attempts to realize the full potential of conjugated molecular structures. Here we report the polymerization of two-monomer-connected precursors (TMCPs) in which two pyrrole units are linked through a connector, yielding highly crystalline polymers. The simultaneous growth of the TMCP results in a close-packed crystal in polypyrrole (PPy) at the molecular scale with either a hexagonal close-packed or face-centred cubic structure, as confirmed by high-voltage electron microscopy, and the structure that formed could be controlled by simply changing the connector. The electrical conductivity of the TMCP-based PPy is almost 35 times that of single-monomer-based PPy, demonstrating its promise for application in diverse fields.

Atom-Thin SnS2-xSex with Adjustable Compositions by Direct Liquid Exfoliation from Single Crystals

Two-dimensional (2D) chalcogenide materials are fundamentally and technologically fascinating for their suitable band gap energy and carrier type relevant to their adjustable composition, structure, and dimensionality. Here, we demonstrate the exfoliation of single-crystal SnS2-xSex (SSS) with S/Se vacancies into an atom-thin layer by simple sonication in ethanol without additive. The introduction of vacancies at the S/Se site, the conflicting atomic radius of sulfur in selenium layers, and easy incorporation with an ethanol molecule lead to high ion accessibility; therefore, atom-thin SSS flakes can be effectively prepared by exfoliating the single crystal via sonication. The in situ pyrolysis of such materials can further adjust their compositions, representing tunable activation energy, band gap, and also tunable response to analytes of such materials. As the most basic and crucial step of the 2D material field, the successful synthesis of an uncontaminated and atom-thin sample will further push ahead the large-scale applications of 2D materials, including, but not limited to, electronics, sensing, catalysis, and energy storage fields.