Preparation and application of gallium-based conductive materials in the very recent years

Gallium and its alloys are a group of metallic materials with low-melting points at or around room temperature.Apart from the good electrical conductivity,the unique liquid state endows those metals with excellent compliance and self-healing capacity,which present great value in the development of flexible and stretchable electronics.Constrained by the high surface tension and low viscosity,however,liquid metals cannot be applied to some common microelectronics manufacturing technologies such as micro-electro mechanics in the preceding years,which impedes their mass production in electronic devices.To address these issues and broaden the applications of liquid metals in electronics devices,numerous efforts have been taken and great progress has been made especially in the very recent years.This review summaries the recent development of liquid metal-based conductive materials from the aspects of preparation or modification methods and their accommodative fabrication techniques in flexible electronic applications.Further outlook including expectations and challenges of liquid metal-based conductive materials are also presented.

Direct ink writing of conductive materials for emerging energy storage systems

Direct ink writing(DIW)has recently emerged as an appealing method for designing and fabricating three-dimensional(3D)objects.Complex 3D structures can be built layer-by-layer via digitally controlled extrusion and deposition of aqueous-based colloidal pastes.The formulation of well-dispersed suspensions with specific rheological behaviors is a prerequisite for the use of this route.In this review article,the fundamental concepts of DIW are presented,including the operation principles and basic features.Typical strategies used for ink formulation are discussed with a focus on the most widely used electrode materials,including graphene,Mxenes,and carbon nanotubes.The recent progress in printing design of emerging energy storage systems,encompassing rechargeable batteries,supercapacitors,and hybrid capacitors,is summarized.Challenges and future perspectives are also covered to provide guidance for the future development of DIW.

Copper Ions Removal from Wastewater by Electrocoagulation Using Cement-based Cathode Plates

The present work uses PEO solution to well disperse carbon fiber and identifies percolation thresholds of carbon fiber and carbon black which are used as conductive fillers.The resultant cathode plates have an average compressive strength of 27.3 MPa and flexural strength of 29.09 MPa,which demonstrate excellent mechanical properties.The Cu^(2+)removal efficiency was measured at different current densities in EC process with cement-based cathode plate,while the voltage changes were recorded.The results showed that the cement-based cathode plate operated stably and achieved 99.7%removal of 1 L of simulated wastewater with a Cu^(2+)concentration of 200 ppm at a current density of 8 m A/cm^(2)for 1 h.Characterization of floc and tested cathode plates,SEM and EDS analyses,and repeatability testing of the tested plates demonstrate the reusability of the plates,proving that cement-based plates can effectively replace metal cathode plates,reduce the cost of EC and improve the applicability of EC devices.

Functionalized Fiber-Based Strain Sensors:Pathway to Next-Generation Wearable Electronics

Wearable strain sensors are arousing increasing research interests in recent years on account of their potentials in motion detection,personal and public healthcare,future entertainment,man-machine interaction,artificial intelligence,and so forth.Much research has focused on fiber-based sensors due to the appealing performance of fibers,including processing flexibility,wearing comfortability,outstanding lifetime and serviceability,low-cost and large-scale capacity.Herein,we review the latest advances in functionalization and device fabrication of fiber materials toward applications in fiber-based wearable strain sensors.We describe the approaches for preparing conductive fibers such as spinning,surface modification,and structural transformation.We also introduce the fabrication and sensing mechanisms of state-of-the-art sensors and analyze their merits and demerits.The applications toward motion detection,healthcare,man-machine interaction,future entertainment,and multifunctional sensing are summarized with typical examples.We finally critically analyze tough challenges and future remarks of fiber-based strain sensors,aiming to implement them in real applications.

Recent Progress in All-Solution-Processed Organic Solar Cells

All-solution-processed organic solar cells(OSCs)(from the bottom electrode to the top electrode)are highly attractive thanks to their low cost,lightweight and high-throughput production.However,achieving highly efficient all-solution-processed OSCs remains a significant challenge.One of the key issues is the lack of high-quality solution-processed electrode systems that can replace indium tin oxide(ITO)and vacuum-deposited metal electrodes.In this paper,we comprehensively review recent advances in all-solution-processed osCs,and classified the devices as the top electrode materials,including silver nanowires(AgNWs),conducting polymers and composite conducting materials.The correlation between electrode materials,properties of electrodes,and device performance in all-solution-processed OSCs is elucidated.In addition,the critical roles of the active layer and interface layer are also discussed.Finally,the prospects and challenges of all-solution-processed OSCs are presented.

Skin-Inspired Electronics Enabled by Supramolecular Polymeric Materials

Next-generation electronics that intimately interact with the human body would play crucial roles in future health monitors and early disease diagnosis.Skin-inspired electronics have been rapidly growing in the past decade to emulate the remarkable sensory and responsive nature of the human skin tissue.

A review on structures,materials and applications of stretchable electrodes

With the rapid development of wearable smart devices,many researchershave carried out in-depth research on the stretchable electrodes.As one of the corecomponents for electronics,the electrode mainly transfers the electrons,which plays animportant role in driving the various electrical devices.The key to the research for thestretchable electrode is to maintain the excellent electrical properties or exhibit theregular conductive change when subjected to large tensile deformation.This articleoutlines the recent progress of stretchable electrodes and gives a comprehensiveintroduction to the structures,materials,and applications,including supercapacitors,lithium-ion batteries,organic light-emitting diodes,smart sensors,and heaters.Theperformance comparison of various stretchable electrodes was proposed to clearly showthe development challenges in this field.We hope that it can provide a meaningfulreference for realizing more sensitive,smart,and low-cost wearable electrical devices inthe near future.

Coulometric Response of H-Selective Solid-Contact Ion-Selective Electrodes and Its Application in Flexible Sensors+

The analytical performance of H+-selective solid-contact ion-selective electrodes(SCISEs)based on solid contact polyaniline doped with chloride(PANI(Cl))and poly(3,4-ethylenedioxythiophene)doped with poly(styrene sulfonate)(PEDOT(PSS))was characterized by a developed coulometric signal transduction method.PEDOT(PSS)solid contact is covered by PVC based H+-selective membrane.The obtained coulometric signal demonstrates that the cumulated charge can be amplified by increasing the capacitance of solid contact.SCISEs covered with spin-coated membrane behave faster amperometric response than electrodes with drop-cast mem-brane.In contrast to earlier works,the amperometric response and impedance spectrum demonstrates H+transfer through SCISEs is independent from the thickness of membrane.The exceptional behavior of PANI(Cl)H+-SCISEs shows that the capacitance estimated from impedance spectrum at low frequency 10 mHz and coulometric signal of PANI(Cl)based SCISEs is influenced by the applied po-tentials,whereas PEDOT(PSS)solid contact is independent from the chosen applied potentials.Furthermore,preliminary investiga-tions of coulometric signal transduction on flexible pH sensor implies its potential applications in wearable sensors for sweat ion concentration detection.

Three-Dimensional Hierarchical Ternary Nanostructures Bismuth/Polypyrrole/CNTs for High Performance Potassium-lon Battery Anodes

In recent years,the anode materials of bismuth(Bi)-based potassium ion batteries with high theoretical capacity and suitable potassium ion insertion potential have attracted extensive attention.However,due to the volume expansion of Bi,the performance of Bi-based anode materials is not ideal during potassium ion(de)intercalation.In order to solve these problems,we report a three-dimensional(3D)ternary bismuth nanoparticles/conductive polymers/carbon nanotubes(Bi/PPy/CNT)hybrid anode material for K-ion batteries.At a current density of 100 mA·g^(-1),its reversible capacity reaches 302 mAh·g^(-1) after 200 cycles,while it reaches 195.7 mAh·g^(-1) after 600 cycles at 1 A·g^(-1).Its excellent performance is attributed to the hydrogel network which provides a range of electron transport networks and high porosity.Carbon nanotubes are used as electron enhancers to reduce the volume expansion of Bi particles during the reaction.This study provides a prerequisite for expanding the application of 3D ternary materials.

Flexible Transparent Near-Infrared Photodetector Based on 2D Ti_(3)C_(2) MXene-Te Van Der Waals Heterostructures

Ti_(3)C_(2) MXe ne servi ng as superior electrical con ductors prese nts more specific performa nee such as tran spar ency,con ductivity tha n gold(Au),and even could form a heterostructure with active materials of the functional devices.Here,a Ti_(3)C_(2) MXene-Te microplate van der Waals heterostructure based tran spare nt near-i nfrared photodetector(PD)is exploited.

Structure and transport properties of zirconia crystals co-doped by scandia,ceria and yttria

This work is a study of the effect of co-doping(ZrO_(2))_(0.9)(Sc_(2)O_(3))_(0.1)solid solution with yttria and/or ceria on the phase composition,local structure and transport properties of the crystals.The solid solution crystals were grown using directional melt crystallization in cold crucible.We show that ceria co-doping of the crystals does not stabilize the high-temperature cubic phase in the entire crystal bulk,unlike yttria codoping.Ceria co-doping of the(ZrO_(2))_(0.9)(Sc_(2)O_(3))_(0.1)crystals increases their conductivity,whereas the addition of 1 mol.%yttria tangibly reduces the conductivity.Equimolar co-doping of the(ZrO_(2))0.9(-Sc_(2_O_(3))0.1 crystals with ceria and yttria changes the conductivity but slightly.Optical spectroscopy of the local structure of the crystals identified different types of optical centers.We found that the fraction of the trivalent cations having a vacancy in the first coordination sphere in the ceria co-doped crystals is smaller compared with that in the yttria co-doped crystals.

Solution-Processed Silver Nanowire as Flexible Transparent Electrodes in Organic Solar Cells

Organic solar cells(OSCs)have attracted much attention due to their advantages in fabricating flexible and semi-transparent devices.Especially,the light weight,flexibility and spectral adjustability make OSCs superior to silicon,perovskite and other thin film based solar cells in applications of integrated photovoltaic devices and wearable electronics.In flexible and semi-transparent OSCs,transparent conducting electrodes(TCEs)play a key role in obtaining high performances.Among various TCEs,silver1 n anowire(AgNW)has become a promisi ng can didate due to its low sheet resistance,high optical transparency,excellent mechanical flexibility and solution processability.In this article,we review the recent advances in AgNW-based TCEs and their applications in the field of OSCs.Firstly,we introduce the general properties of AgNW including optoelectronic and mechanical characteristics.Secondly,the preparation methods of AgNW are discussed,along with some approaches on the optimization of AgNW to overcome the shortcomings of TCEs.Thirdly,we discuss the applications of AgNW as TCEs in fabricating flexible and semi-transparent OSCs,including the use of AgNW as bottom and top electrodes.Finally,we point out the challenges in AgNW-based TCEs and suggest several guidelines for preparing AgNW so as to meet the demands for the practical use of OSCs.

Sub-nanometer supramolecular rectifier based on the symmetric building block with destructive σ-interference

Molecular rectifier, as a basic function of molecular electronic devices, has attracted extensive attention for the opportunity in constructing sub-nanometer electronic devices. However, tunneling leakage current has a significant contribution as electronic devices shrink in size, which leads to a challenge in fabricating molecular rectifiers at the sub-nanometer scale. Here, we experimentally demonstrate a sub-nanometer molecular rectifier based on the supramolecular junction assembled between water and 1,4-diazabicyclo[2.2.2]octane (DABCO) molecule. The charge transport through DABCO and corresponding supramolecular junctions exhibits destructive σ-interference, ensuring a sharp conductance variation for transmission modulation. The supramolecular interaction between DABCO and water readily introduces the asymmetric electrode-molecule interaction, which combines with the destructive σ-interference to support the sub-nanometer rectification.