Device design principles and bioelectronic applications for flexible organic electrochemical transistors

Organic electrochemical transistors(OECTs) exhibit significant potential for applications in healthcare and human-machine interfaces, due to their tunable synthesis, facile deposition, and excellent biocompatibility. Expanding OECTs to the fexible devices will significantly facilitate stable contact with the skin and enable more possible bioelectronic applications. In this work,we summarize the device physics of fexible OECTs, aiming to offer a foundational understanding and guidelines for material selection and device architecture. Particular attention is paid to the advanced manufacturing approaches, including photolithography and printing techniques, which establish a robust foundation for the commercialization and large-scale fabrication. And abundantly demonstrated examples ranging from biosensors, artificial synapses/neurons, to bioinspired nervous systems are summarized to highlight the considerable prospects of smart healthcare. In the end, the challenges and opportunities are proposed for fexible OECTs. The purpose of this review is not only to elaborate on the basic design principles of fexible OECTs, but also to act as a roadmap for further exploration of wearable OECTs in advanced bio-applications.

Electrochemical Proton Storage:From Fundamental Understanding to Materials to Devices

Simultaneously improving the energy density and power density of electrochemical energy storage systems is the ultimate goal of electrochemical energy storage technology.An effective strategy to achieve this goal is to take advantage of the high capacity and rapid kinetics of electrochemical proton storage to break through the power limit of batteries and the energy limit of capacitors.This article aims to review the research progress on the physicochemical properties,electrochemical performance,and reaction mechanisms of electrode materials for electrochemical proton storage.According to the different charge storage mechanisms,the surface redox,intercalation,and conversion materials are classified and introduced in detail,where the influence of crystal water and other nanostructures on the migration kinetics of protons is clarified.Several reported advanced full cell devices are summarized to promote the commercialization of electrochemical proton storage.Finally,this review provides a framework for research directions of charge storage mechanism,basic principles of material structure design,construction strategies of full cell device,and goals of practical application for electrochemical proton storage.

3D Printing of Next-generation Electrochemical Energy Storage Devices: from Multiscale to Multimaterial

The increasing energy requirements to power the modern world has driven active research into more advanced electrochemical energy storage devices(EESD)with both high energy densities and power densities.Wide range of newly discovered materials with promising electrochemical properties has shown great potential for next-generation devices,but their performance is normally associated with contradicting demands of thin electrodes and high mass loading that can be hardly achieved for practical applications.Design of three-dimensional(3D)porous electrodes can increase the mass loading while maintaining the effective charge transport even with thick electrodes,which has proven to be efficient to overcome the limitations.3D structures have also been demonstrated excellent structural stability to withstand strong strains and stresses generated during charge/discharge cycle.3D printing,which can fabricate various delicate and complex structural designs,thus offering brand-new opportunities for the rational design and facile construction of next-generation EESDs.The recent developments in 3D printing of next-generation EESDs with high performance are reviewed.Advanced/multiscale electrode structures,such as hierarchically porous structure that can be constructed via high-resolution 3D printing or with post-treatment,are further emphasized.The ability of current 3D printing techniques to fulfill multimaterial printing to fulfill simple packaging will be covered.

Coal-derived humic acid for application in acid mine drainage(AMD)water treatment and electrochemical devices

In this research work,isolation of humic acid from coal of Northeastern region of India is reported.The study is also targeted for application of the coal-derived humic acid in acid mine drainage(AMD)water treatment and electrochemical devices.All the obtained results are compared with the standard humic acid and examined the formation of humic acid from the coal.The isolated coal-derived humic acid is found to be high degree of humifications and relatively stable up to about 200℃.The FTIR study indicates the formation of metal-humic acid complexes.On treatment with acidic water(AMD),the coal-derived humic acid was found to have the ability to remove toxic metal such as(in order)Pb>Cu>Zn>Cd.In addition,the preliminary electrochemical properties of the isolated humic acid are also discussed in the paper.The specific capacitance of the isolated coal-derived humic acid via cyclic voltammetry and charge-discharge analysis is found to be 7 mF/g at scan rate 10 mV/s and 22 mF/g within the potential window 0.4 V,respectively.The charge-discharge cycles are stable for more than 1000 cycles within the potential window 0.4 V.This study will create a new pathway for the further research in this field.

A review of neutral pH polymer electrolytes for electrochemical capacitors:Transitioning from liquid to solid devices

The development of neutral pH polymer electrolytes has enabled high-performance solid-state,thin,and flexible electrochemical capacitors(ECs)to provide power for future consumer electronics and Internet-of-Thing devices.Notwithstanding their promising prospect,there is still some lack of understandings or disconnections from fundamental science to practical applications of these electrolytes.In this review,we provide an overview of stateof-the-art studies on ECs with neutral pH electrolytes in both liquid and solid configurations.Starting from the fundamental studies on the voltage window and ion conduction of salt species in liquid solution to polymer electrolytes,key considerations in developing neutral pH polymer electrolytes are discussed.The performance of the polymer electrolytes along with their enabled solid symmetric and asymmetric EC devices,as well as some enhanced functionalities are presented.The future directions for research on neutral pH polymer electrolytes are proposed,expected to provide reference for further enriching the fundamental knowledge and improving the device performances.

A Study on the Full-Solid-State Electrochemical Systems for Amperometric Carbon Dioxide Gas Sensor Devices

A new type of solid polymer electrolyte based on polyacrylonitrile (PAN )-dimethylsulfoxide (DMSO)-tetrabutylammonium perchlorate (TBAP) system has been prepared. The ionic conductivities of such solid-electrolytes reach values as high as 10-4 S. cm-1 at room temperature. At proper content of each component in the solid-electrolyte the polymeric film has a porous network microstructure of three dimen-sions,and exhibits a good level of mechanical properties and dimensional stability. The full-solid-state elec-trochemical cell contains two coplanar electrodes coated by a thin layer of PAN-DMSO-TBAP solid-elec-trolyte: a Au microdisk as working electrode and a Ag ring counter/reference electrode. This study has shown that the integrated two-electrode assembly can be directly used for the amperometric solid-state car-bon dioxide gas sensor devices,and it shows good response characteristics for direct amperometric determi-nation of the CO2 concentration in the gas phase. Also, such full-solid-state amperometric sensor devices possess their own original advantages.

Next-Generation Intelligent MXene-Based Electrochemical Aptasensors for Point-of-Care Cancer Diagnostics

Delayed diagnosis of cancer using conventional diagnostic modalities needs to be addressed to reduce the mortality rate of cancer.Recently,2 D nanomaterial-enabled advanced biosensors have shown potential towards the early diagnosis of cancer.The high surface area,surface functional groups availability,and excellent electrical conductivity of MXene make it the 2 D material of choice for the fabrication of advanced electrochemical biosensors for disease diagnostics.MXene-enabled electrochemical aptasensors have shown great promise for the detection of cancer biomarkers with a femtomolar limit of detection.Additionally,the stability,ease of synthesis,good reproducibility,and high specificity offered by MXene-enabled aptasensors hold promise to be the mainstream diagnostic approach.In this review,the design and fabrication of MXene-based electrochemical aptasensors for the detection of cancer biomarkers have been discussed.Besides,various synthetic processes and useful properties of MXenes which can be tuned and optimized easily and efficiently to fabricate sensitive biosensors have been elucidated.Further,futuristic sensing applications along with challenges will be deliberated herein.

Layered double hydroxides as electrode materials for flexible energy storage devices

To prevent and mitigate environmental degradation,high-performance and cost-effective electrochemical flexible energy storage systems need to be urgently developed.This demand has led to an increase in research on electrode materials for high-capacity flexible supercapacitors and secondary batteries,which have greatly aided the development of contemporary digital communications and electric vehicles.The use of layered double hydroxides(LDHs)as electrode materials has shown productive results over the last decade,owing to their easy production,versatile composition,low cost,and excellent physicochemical features.This review highlights the distinctive 2D sheet-like structures and electrochemical characteristics of LDH materials,as well as current developments in their fabrication strategies for expanding the application scope of LDHs as electrode materials for flexible supercapacitors and alkali metal(Li,Na,K)ion batteries.

Colorless to black switching with high contrast ratio via the electrochemical process of a hybrid organic-inorganic perovskite

Colorless‐to‐black switching has attracted widespread attention for smart windows and multifunctional displays because they are more useful to control solar energy.However,it still remains a challenge owing to the tremendous difficulties in the design of completely reverse absorptions in transmissive and colored states.Herein,we report on an electrochemical device that can switch between colorless and black by using the electrochemical process of hybrid organic–inorganic perovskite MAPbBr_(3),which shows a high integrated contrast ratio of up to 73%from 400 to 800 nm.The perovskite solution can be used as the active layer to assemble the device,showing superior transmittance over the entire visible region in neutral states.By applying an appropriate voltage,the device undergoes reversible switching between colorless and black,which is attributed to the formation of lead and Br_(2)in the redox reaction induced by the electron transfer process in MAPbBr_(3).In addition,the contrast ratio can be modulated over the entire visible region by changing the concentration and the applied voltage.These results contribute toward gaining an insightful understanding of the electrochemical process of perovskites and greatly promoting the development of switchable devices.

Electrode Modifications for Polymer Light-Emitting Electrochemical Cells

The influence of different modification methods on the surface properties of indium-tin-oxide (ITO) electrodes were investigated by measurements of chemical composition,surface roughness,sheet resistance,contact angle and surface free energy.Experimental results demonstrate that oxygen plasma treatment more effectively optimizes the surface properties of ITO electrodes compared with the other treatments.Furthermore,the polymer light-emitting electrochemical cells (PLECs) with the differently treated ITO substrates as device electrodes were fabricated and characterized.It is found that oxygen plasma treatment on the ITO electrode enhances injection current,luminance and efficiency,thereby improves the device characteristics of the PLECs.

Safety regulation of gel electrolytes in electrochemical energy storage devices

Electrochemical energy storage devices,such as lithium ion batteries(LIBs),supercapacitors and fuel cells,have been vigorously developed and widely researched in past decades.However,their safety issues have appealed immense attention.Gel electrolytes(GEs),with a special state in-between liquid and solid electrolytes,are considered as the most promising candidates in electrochemical energy storage because of their high safety and stability.This review summarized the recent progresses made in the application of GEs in the safety regulation of the electrochemical energy storage devices.Special attention was paid to the gel polymer electrolytes,the organic low molecule-mass GEs,as well as the fumed silica-based and siloxane-based GEs.Finally,the current challenges and future directions were proposed in terms of the development of GEs.

Autonomous Chemistry Enabling Environment-Adaptive Electrochemical Energy Storage Devices

Next-generation electronics that are fused into the human body can play a key role in future intelligent communication,smart healthcare,and human enhancement applications.As a promising energy supply component for smart biointegrated electronics,environment-adaptive electrochemical energy storage(EES)devices with complementary adaptability and functions have garnered huge interest in the past decade.Owing to the advancements in autonomous chemistry,which regulate the constitutional dynamic networks in materials,EES devices have witnessed higher freedom of autonomous adaptability in terms of mechano-adaptable,biocompatibility,and stimuli-response properties for biointegrated and smart applications.In this mini-review,we summarize the recent progress in emerging environmentadaptive EES devices enabled by the constitutional dynamic network of mechanical adaptable materials,biocompatible materials,and stimuli-responsive supramolecular polymer materials.Finally,the challenges and perspectives of autonomous chemistry on the environment-adaptive EES devices are discussed.

Electrochemical detection of human ferritin based on gold nanorod reporter probe and cotton thread immunoassay device

In this study,a natural cotton thread immunoassay device combined with gold nanorod（GNR） reporter probe is developed for the rapid,sensitive and quantitative electrochemical determination of human ferritin,a lung cancer related biomarker.Human ferritin as an analyte and a pair of monoclonal antibodies are used to demonstrate the proof-of-concept on the cotton thread immunoassay device.An enhancement of the sensitivity is achieved by using gold nanorod as an electroactive report probe compared with a traditional gold nanoparticle（GNP） report probe.The device was capable of measuring 1.58 ng/mL ferritin in 30 min by anodic stripping voltammetry（ASV） testing,which meet the requirement for clinical diagnosis.

Efficient Hybrid Photovoltaic Devices Based on in-situ Electrochemical Copolymerization of 3-Methylthiophene and Bithiophene into Pores of Nanocrystalline TiO2

Novel organic and inorganic hybrid photovoltaic devices were thbricated by in-situ electrochemical copolymerization of 3-methylthiophene（3MT） and bithiophene（BT） into the pores of nanostructured TiO2 sintered on fluorine-doped tin oxide（FTO） substrate. The photoactive layer was investigated by Fourier transform infrared（FTIR） spectroscopy, ultraviolet-visable（UV-Vis） spectrometer, scanning electron microscope（SEM） and cyclic voltammo- gram characterization. Device efficiency based on different molar feed ratios of 3MT and BT during electrochemical polymerization, and the effect of in-situ copolymer state（doped by electrolyte and de-doped） were measured and compared. Under the solar illumination of 100 mW/cm2（AM 1.5）, an optimized device efficiency of 0.938% was obtained when the molar ratio of 3MT to BT was 500：1, polymerization time was 500 s and the system was in doped copolymer state, respectively. The mechanism of overall photovoltaic parameter improvement was discussed.

High‑Temperature Electrochemical Devices Based on Dense Ceramic Membranes for CO_(2) Conversion and Utilization

The adverse effects of global warming and climate change have driven the exploration of feasible routes for CO_(2) capture,storage,conversion and utilization.The processes related to CO_(2) conversion in high-temperature electrochemical devices(HTEDs)using dense ceramic membranes are particularly appealing due to the simultaneous realization of highly efficient CO_(2) conversion and value-added chemical production as well as the generation of electricity and storage of renewable energy in some cases.Currently,most studies are focused on the two processes,CO_(2) electrolysis and H2O/CO_(2) co-electrolysis in oxygen-conducting solid oxide electrolysis cell(O-SOEC)reactors.Less attention has been paid to other meaningful CO_(2)-conversion-related processes in HTEDs and systematic summary and analysis are currently not available.This review will fill the gap and classify the CO_(2)-conversion-related processes in HTEDs reported in recent years into four types accord-ing to the related reactions,including assisted CO_(2) reduction to CO,H2O and CO_(2) co-conversion,dry reforming of methane and CO_(2) hydrogenation.Firstly,an overview of the fundamentals of HTED processes is presented,and then the related mechanism and research progress of each type of reactions in different HTEDs are elucidated and concluded accordingly.The remaining major technical issues are also briefly introduced.Lastly,the main challenges and feasible solutions as well as the future prospects of HTEDs for CO_(2)-conversion-related processes are also discussed in this review.

可穿戴汗液传感器系统的研究进展

在新材料和新技术广泛应用的背景下,柔性可穿戴汗液监测设备成为当前国内外研究的热点。目前,基于柔性可穿戴设备的汗液检测一般需要3个环节:汗液的取样、目标分析物的选择性检测以及系统的集成与控制。本文主要从汗液原位检测的优势出发,总结了汗液的刺激和提取的方法,并对电化学类的汗液传感器的研究进展进行多角度的分析与评价。最后讨论了可穿戴的汗液传感器存在的不足,以及未来系统的发展方向。

可穿戴离子检测及电促渗系统研究

汗液作为一种非侵入性健康监测的资源,含有丰富的生理信息,可以进行实时无创监测。然而,人在久坐或者睡眠时无法获得足够的汗液进行采样分析,若要实现汗液成分的长期原位监测并不容易。基于以上两点问题,主要通过电化学传感器与可穿戴传感技术相结合,以非侵入的方式监测汗液中的Na+,并开发测试了一套集成的可穿戴平台,用于实时采集和分析汗液中Na+的浓度。本系统Na+在浓度为20 mmol/L~160 mmol/L的测试范围内,灵敏度达到61.6 mV/decade。除此之外,可以根据受试者自身出汗量情况来调节系统刺激出汗的相关参数,从而能够减小长期电促渗药物刺激对于受试者的影响。

单层石墨烯微米尺度图案化和功能化:调控电子传输特性

石墨烯具有优异的物理特性,如单原子厚度、极高的载流子迁移率等。然而,其零带隙的半金属特性限制了题在高性能场效应晶体管中的应用。为此,研究者们提出了石墨烯纳米化、外场诱导、掺杂以及化学图案化等策略,以调控其带隙宽度。但是,这些方法的可控性以及稳定性还需要进一步改善。在本研究中,我们提出采用电化学溴化并结合光刻图案化调控单层石墨烯的电子传输特性,通过这种方法,成功制备了图案化的溴化石墨烯(SLGBr)。进一步研究表明,单层石墨烯的电子传输性能可以通过溴化程度来调控。当溴化程度较小时,SLGBr表现为电阻特性,且其电导随溴化程度增加而减小;当溴化程度增加到一定值时,SLGBr表现为与半导体类似的特性。本研究将为全石墨烯器件的制备提供可行的技术路线,拓展其在微电子领域的应用。

中空纤维膜结构的电化学检测装置设计

目前中空纤维膜的结构检测手段主要包括扫描电子显微镜(SEM)、原子力显微镜等,存在检测成本高、操作不便等问题。为此,基于电化学交流阻抗谱(EIS)检测方法自主设计并开发了中空纤维膜EIS检测系统。首先,制备中空纤维膜并通过扫描电子显微镜对其进行表征;然后,针对膜结构设计检测装置,进行不同电极材质的可行性分析、不同电极长度的影响分析以及不同结构中空纤维膜的EIS检测;最后,验证了该中空纤维膜电化学检测装置的有效性。