Synthesis, Crystal Packing Aspects and Pseudosymmetry in Coordination Compounds with a Phosphorylamide Ligand

This work reports the synthesis and crystal structure of new closely related coordination compounds, [ML2]·nTHF, where M is Zn or Mn; L is a phosphorylmethylamide derivative of benzothiadiazole; n = 1 (M = Zn) and 1, 2 (M = Mn); and THF is tetrahydrofuran. The zinc compound, 1·THF, crystallizes in a high-symmetry space group, I41/a, that is relatively rare for compounds with organic ligands. The corresponding manganese congener, 2·THF, with a similar crystal packing, features a pseudosymmetrical structure P21/c of the doubled volume of the unit cell as compared to 1·THF. The main difference between the structures lies in a different arrangement of solvate THF molecules, which likely modulates the crystal packing of the complexes. Another manganese solvatomorph, 2·2THF, reveals a fundamentally different crystal packing while exhibiting a similar geometry of the complex. We consider the problem of localization of solvate THF molecules and the types of their disorder by the example of compounds 1–2.

Black phosphorous-based human-machine communication interface

Assistive technology involving auditory feedback is generally utilized by those who are visually impaired or have speech and language difficulties. Therefore, here we concentrate on an auditory human-machine interface that uses audio as a platform for conveying information between visually or speech-disabled users and society. We develop a piezoresistive tactile sensor based on a black phosphorous and polyaniline (BP@PANI) composite by the facile chemical oxidative polymerization of aniline on cotton fabric. Taking advantage of BP's puckered honeycomb lattice structure and superior electrical properties as well as the vast wavy fabric surface, this BP@PANI-based tactile sensor exhibits excellent sensitivity, low-pressure sensitivity, reasonable response time, and good cycle stability. For a real-world application, a prototype device employs six BP@PANI tactile sensors that correspond to braille characters and can convert pressed text into audio on reading or typing to assist visually or speech-disabled persons. Overall, this research offers promising insight into the material candidates and strategies for the development of auditory feedback devices based on layered and 2D materials for human-machine interfaces.

Polymerization-Driven Self-Wrinkling on a Frozen Hydrogel Surface toward Ultra-Stretchable Polypyrrole-Based Supercapacitors

The construction of ultra-stretchable and smart supercapacitors with a large deformation-tolerance range and highly efficient self-healability is fully desired for next-generation wearable electronics. Herein, a sandwich-structured self-wrinkling hydrogel film (SSHF) is fabricated by freezing-constrained polymerization-driven self-wrinkling. Polypyrrole layers are first polymerized on a frozen pre-stretching hydrogel surface and subsequently self-wrinkled upon releasing the pre-strain. The SSHF with two polypyrrole electrode layers sandwiched with a hydrogel electrolytic layer is finally achieved by cutting four edges, and the all-in-one integrated structure creatively avoids the delamination between the electrodes and the electrolyte. The as-obtained SSHF can be directly used as an integrated all-in-one supercapacitor demonstrating high specific capacitance (79.5 F g^-1 at 0.5 A g^-1), large stretchability (>500%), and reliable room temperature self-healability. The freezing-constrained polymerization-driven self-wrinkling strategy might provide a unique self-wrinkling procedure to fabricate self-healable conducting polymer-based hydrogels for ultra-stretchable smart supercapacitors.

Synergistic 2D MoSe2@WSe2 nanohybrid heterostructure toward superior hydrogen evolution and flexible supercapacitor

Two-dimensional (2D) transition metal dichalcogenide (TMDC) heterostructure is a new age strategy to achieve high electrocatalytic activity and ion storage capacity. The less complex and cost-effective applicability of the large-area TMDC heterostructure (HS) for energy applications require more research. Herein, we report the MoSe₂@WSe₂ nanohybrid HS electrocatalyst prepared using liquid exfoliated nanocrystals, followed by direct electrophoretic deposition (EPD). The improved catalytic activity is attributed to the exposure of catalytic active sites on the edge of nanocrystals after liquid exfoliation and the synergistic effect arises at HS interfaces between the MoSe₂ and WSe₂ nanocrystals. As predicted, the HS catalyst achieves a lower overpotential of 158 mV, a smaller Tafel slope of 46 mV dec^-1 for a current density of 10 mA cm^-2, and is stable for a long time. The flexible symmetric supercapacitor (FSSC) based on the HS catalyst demonstrates the excellent specific capacitance (C_sp) of 401 F g^-1 at 1 A g^-1, 97.20% capacitance retention after 5000 cycles and high flexible stability over 1000 bending cycles. This work presents a less complex and solution-processed efficient catalyst for future electrochemical energy applications.

Flexible wearable MXene Ti3C2-Based power patch running on sweat

Flexible supercapacitors (FSCs) have received a lot of interest as portable power sources for wearable electronics. The biocompatibility of electrodes and electrolytes in wearable FSCs is important to consider although research into these topics is still in its early stages. In this work, we developed a wearable FSC that uses MXene Ti₃C₂ nanosheets and polypyrrole-carboxymethylcellulose nanospheres composite (Ti₃C₂@PPy-CMC) as the active electrode material and sweat as the electrolyte. The electrochemical performances of Ti₃C₂@PPy-CMC FSC were analyzed using an artificial sweat solution and exhibited excellent specific capacitance, power density, cycling stability, and bending stability. To demonstrate a real application of Ti₃C₂@PPy-CMC FSC, a sweat-chargeable FSC patch has been developed that can be applied directly to human clothing and skin to power a portable electronic gadget when the wearer is exercising. A comprehensive electrochemical study of the FSC patch was also conducted in various sweat secretion body regions such as the finger, foot sole, and wrist. Ti₃C₂@PPy-CMC composite's outstanding electrochemical performance indicates its potential capabilities and biocompatibility in wearable energy storage devices.

Real-Time Biomonitoring Device Based on 2D Black Phosphorus and Polyaniline Nanocomposite Flexible Supercapacitors

Flexible energy storage devices are becoming significantly important to power wearable and portable devices that monitor physiological parameters for many biomedical applications. Many hybrid nanomaterials based on 2D materials are used in order to improve the performance of flexible energy storage devices. Here, a hybrid nanocomposite is synthesized through in situ polymerization of aniline in the presence of black phosphorus (BP) nanoflakes. This nanocomposite, polyaniline (PANI)@BP, is employed to fabricate flexible supercapacitor (FSC) electrodes. PANI@BP FSCs can provide a power source for biometric devices. The generated signal can be transmitted to a smartphone in real time via wireless communication. Such a compact and lightweight integrated device has been used to track a human heart beat while powered by PANI@BP FSC. These findings are providing a promising example of a flexible energy storage device that can be integrated with different real-time health monitoring devices.

Surface modification of manganese monoxide through chemical vapor deposition to attain high energy storage performance for aqueous zinc-ion batteries

Surface modification of the manganese-based oxide electrode is considered to be a viable strategy to improve electrochemical property in aqueous zinc-ion batteries (ZIBs). However, the modification method through traditional wet-chemical technology can hardly to satisfy high rate capability for aqueous ZIBs due to unhomogeneous and nonconformal coating originates from surface energy mismatch. Herein, a surface modification strategy based on chemical vapor deposition is developed to enhance the electrochemical property of the inactive MnO in aqueous ZIBs. The constructed carbon coating modified MnO electrode shows excellent reversible capacity and superior rate capability with remarkable energy density of 351 Wh kg^-1 at 625 W kg^-1. The energy storage mechanism of the electrode during the charge and discharge processes is elucidated according to the ex-situ measurements of X-ray diffraction and photoelectron spectroscopy, Fourier transform infrared spectra, and galvanostatic intermittent titration techniques. Moreover, soft-packaged batteries are fabricated with the carbon coating modified MnO, which shows great promises for the practical application of the material. The work paves the way for the exploitation of high performance surface-modified electrode through chemical vapor deposition for aqueous ZIBs.

MXene-Based Flexible Supercapacitors: Influence of an Organic Ionic Conductor Electrolyte on the Performance

Owing to the rise of miniaturized wearable electronic devices in the last decade, significant demands have arisen to obtain high-performance flexible supercapacitors (FSCs). Recently, a lot of research has been focused on developing smart components of FSCs and integrating them into new device configurations. In this work, FSCs based on a Ti₃C₂ nanosheet (NS) and an organic ionic conductor (OIC)-induced hydrogel as the electrode and the electrolyte, respectively, were used. The FSCs fabricated have three different configurations (sandwich, twisted fiber, and interdigitated) and a comparative study of their electrochemical performance was investigated in terms of cycle stability, bending stability, power density, and energy density. Finally, the experimental validation of practical application was conducted, which suggested excellent electrochemical stability of Ti₃C₂ NS FSCs for driven commercial electronic gadgets. This study presents mechanically robust, lightweight, high-performance FSCs, which can be assembled in different configurations for powering wearable electronic devices.