Accurate, convenient, label-free, and cost-effective biomolecules detection platforms are currently in high demand. In this study, we showcased the utilization of electrolyte-gated InGaZnO field-effect transistors (IGZO FETs) featuring a large on-off current ratio of over 106 and a low subthreshold slope of 78.5 mV/dec. In the DNA biosensor, the modification of target DNA changed the effective gate voltage of IGZO FETs, enabling an impressive low detection limit of 0.1 pM and a wide linear detection range from 0.1 pM to 1 μM. This label-free detection method also exhibits high selectivity, allowing for the discrimination of single-base mismatch. Furthermore, the reuse of gate electrodes and channel films offers cost-saving benefits and simplifies device fabrication processes. The electrolyte-gated IGZO FET biosensor presented in this study shows great promise for achieving low-cost and highly sensitive detection of various biomolecules.

Abstract 2D conjugated metal‐organic frameworks (c‐MOFs) have emerged as promising materials for (opto)electronic applications due to their excellent charge transport properties originating from the unique layered‐stacked structures with extended in‐plane conjugation. The further advancement of MOF‐based (opto)electronics necessitates the development of novel 2D c‐MOF thin films with high quality. Cu‐HHHATN (HHHATN: hexahydroxyl‐hexaazatrinaphthylene) is a recently reported 2D c‐MOF featuring high in‐plane conjugation, strong interlayer π–π stacking, and multiple coordination sites, while the production of its thin‐film form has not yet been reported. Herein, large‐area Cu‐HHHATN thin films with preferential orientation, high uniformity, and smooth surfaces are realized by using a convenient layer‐by‐layer growth method. Flexible photodetectors are fabricated, showing broadband photoresponse ranging from UV to short‐wave infrared (370 to 1450 nm). The relatively long relaxation time of photocurrent, which arises from the trapping of photocarriers, renders the device's synaptic plasticity similar to that of biological synapses, promising its use in neuromorphic visual systems. This work demonstrates the great potential of Cu‐HHHATN thin films in flexible optoelectronic devices for various applications.

Organic semiconductors have emerged as promising materials for facilitating communication between electronic systems and biological entities due to their distinctive advantages, such as structural similarity to biological substances, biocompatibility, tailorability, and mechanical flexibility. Organic bioelectronics mainly focuses on developing devices capable of sensing biological substances and signals, as well as stimulating or regulating biological processes. This interdisciplinary field encompasses various applications, ranging from healthcare monitoring and diagnostics to neuroprosthetics and human-machine interfaces. Among various organic devices, organic electrochemical transistors (OECTs) have gained significant attention in bioelectronics due to their effective coupling of electronic and ionic transports. OECTs utilize organic mixed ionic-electronic conductors (OMIECs) as ion-permeable channel materials, enabling ion doping throughout the entire channel. This unique volumetric doping gives OECTs ultrahigh transconductance at low working voltages, making them advantageous for highly sensitive biosensing and reliable recording of electrophysiological signals with enhanced signal-to-noise ratios. The properties of OMIECs play a crucial role in determining the device performance and the application scenarios, leading to considerable interest in recent decades. Understanding the relationship between material figures of merit and specific applications is crucial for guiding material design and selection. This account focuses on the recent advances in OMIECs development for OECTs and highlights their impact on bioelectronic applications. First, we introduce the operation of OECTs, emphasizing the coupling of electronic and ionic circuits and the unique bulk doping mechanism that sets them apart from conventional field-effect transistors. Potential factors influencing transconductance and transient behavior are discussed. Then, we delve into the historical perspective on OMIECs development in OECTs, underscoring material design strategies that enable mixed conduction, including the introduction of glycolated side chains and the utilization of emerging 2D nanoporous structures. Subsequently, we explore the beneficial traits of OMIECs for bioelectronic applications. We discuss the strategies to harness the high transconductance originating from OMIECs for achieving high-performance biosensors and recording electrophysiological signals with superior signal-to-noise ratios. Additionally, we critically examine the latest strategies employed in the realization of stretchable, self-healing, and bioadhesive OMIECs. These innovative features have made significant contributions to wearable and implantable applications. The integration of stretchability ensures compatibility with the dynamic nature of biological entities, enabling robust and reliable performance. The self-healing capabilities of OMIECs exhibit a remarkable ability to autonomously repair damage or degradation, thereby prolonging the lifespan and functionality of bioelectronic devices. Moreover, the bioadhesive properties of OMIECs enable secure attachment to biological surfaces, establishing intimate contact for improved signal acquisition and stability. Finally, we discuss the challenges and opportunities in the further development of OMIECs in OECTs. This article provides an overview of recent advancements in OMIECs and their potential to revolutionize bioelectronic applications. With continuous innovation, OMIECs hold great promise for shaping the future of bioelectronics.

In this work, we report a new concept of upconversion-powered photoelectrochemical (PEC) bioanalysis. The proof-of-concept involves a PEC bionanosystem comprising a NaYF4:Yb,Tm@NaYF4 upconversion nanoparticles (UCNPs) reporter, which is confined by DNA hybridization on a CdS quantum dots (QDs)/indium tin oxide (ITO) photoelectrode. The CdS QD-modified ITO electrode was powered by upconversion absorption together with energy transfer effect through UCNPs for a stable photocurrent generation. By measuring the photocurrent change, the target DNA could be detected in a specific and sensitive way with a wide linear range from 10 pM to 1 μM and a low detection limit of 0.1 pM. This work exploited the use of UCNPs as signal reporters and realized upconversion-powered PEC bioanalysis. Given the diversity of UCNPs, we believe it will offer a new perspective for the development of advanced upconversion-powered PEC bioanalysis.

The improvement of living standards and the advancement of medical technology have led to an increased focus on health among individuals. Detections of biomarkers are feasible approaches to obtaining information about health status, disease progression, and response to treatment of an individual. In recent years, organic electrochemical transistors (OECTs) have demonstrated high electrical performances and effectiveness in detecting various types of biomarkers. This review provides an overview of the working principles of OECTs and their performance in detecting multiple types of biomarkers, with a focus on the recent advances and representative applications of OECTs in wearable and implantable biomarker detections, and provides a perspective for the future development of OECT-based biomarker sensors.

Flexible and stretchable biosensors can offer seamless and conformable biological-electronic interfaces for continuously acquiring high-fidelity signals, permitting numerous emerging applications. Organic thin film transistors (OTFTs) are ideal transducers for flexible and stretchable biosensing due to their soft nature, inherent amplification function, biocompatibility, ease of functionalization, low cost, and device diversity. In consideration of the rapid advances in flexible-OTFT-based biosensors and their broad applications, herein, a timely and comprehensive review is provided. It starts with a detailed introduction to the features of various OTFTs including organic field-effect transistors and organic electrochemical transistors, and the functionalization strategies for biosensing, with a highlight on the seminal work and up-to-date achievements. Then, the applications of flexible-OTFT-based biosensors in wearable, implantable, and portable electronics, as well as neuromorphic biointerfaces are detailed. Subsequently, special attention is paid to emerging stretchable organic transistors including planar and fibrous devices. The routes to impart stretchability, including structural engineering and material engineering, are discussed, and the implementations of stretchable organic transistors in e-skin and smart textiles are included. Finally, the remaining challenges and the future opportunities in this field are summarized.

Electrocardiogram (ECG) mapping can provide vital information in sports training and cardiac disease diagnosis. However, most electronic devices for monitoring ECG signals need to use multiple long wires, which limit their wearability and conformability in practical applications, while wearable ECG mapping based on integrated sensor arrays has been rarely reported. Herein, ultra‐flexible organic electrochemical transistor (OECT) arrays used for wearable ECG mapping on the skin surface above a human heart are presented. QRS complexes of ECG signals at different recording distances and directions relative to the heart are obtained. Furthermore, the ECG signals are successfully analyzed by the devices before and after exercise, indicating potential applications in some sports training and fitness scenarios. The OECT arrays that can conveniently monitor spacial ECG signals in the heart region may find niche applications in wearable electronics and healthcare products in the future.

Electrochemical transistors (ECTs) have shown broad applications in bioelectronics and neuromorphic devices due to their high transconductance, low working voltage, and versatile device design. To further improve the device performance, semiconductor materials with both high carrier mobilities and large capacitances in electrolytes are needed. Here, we demonstrate ECTs based on highly oriented two-dimensional conjugated metal-organic frameworks (2D c-MOFs). The ion-conductive vertical nanopores formed within the 2D c-MOFs films lead to the most convenient ion transfer in the bulk and high volumetric capacitance, endowing the devices with fast speeds and ultrahigh transconductance. Ultraflexible device arrays are successfully used for wearable on-skin recording of electrocardiogram (ECG) signals along different directions, which can provide various waveforms comparable with those of multilead ECG measurement systems for monitoring heart conditions. These results indicate that 2D c-MOFs are excellent semiconductor materials for high-performance ECTs with promising applications in flexible and wearable electronics.

Flexible bioelectronics, offering soft functionalized interfaces to couple biology and electronics, have gained increasing interest due to its great promise in personalized health monitoring, point-of-care diagnosis, and the Internet of Things (IoT). Organic electrochemical transistors (OECTs), capable of mixed ionic-electronic transport, have been widely implemented in flexible bioelectronics due to their flexibility, biocompatibility, high transconductance, low working voltage, design diversity, and facile manufacturing. In this review, we focus on the representative bioelectronic applications of flexible OECTs. We first introduce the device physics of OECTs, with a highlight on their identifying features compared to conventional field-effect transistors. Then, the state-of-the-art channel materials used in OECTs are summarized, with discussions on their figures of merit. Followed by an introduction to the main techniques employed for fabricating flexible OECTs, we examine the up-to-date progress in flexible OECTs for bioelectronic applications, including diverse biosensors, electrophysiological monitoring, and neuromorphic devices. Accompanied by a concise summary, the challenges and opportunities in the commercialization of flexible OECTs are discussed.

Cu3 (HHTT)2 (HHTT: 2,3,7,8,12,13-hexahydroxytetraazanaphthotetraphene) is a novel 2D conjugated metal-organic framework (2D c-MOF) with efficient in-plane d-π conjugations and strong interlayer π-π interactions while the growth of Cu3 (HHTT)2 thin films has never been reported until now. Here, the successful fabrication of highly oriented wafer-scale Cu3 (HHTT)2 thin films with a layer-by-layer growth method on various substrates is presented. Its semiconducting behavior and carrier transport mechanisms are clarified through temperature and frequency-dependent conductivity measurements. Flexible photodetectors based on Cu3 (HHTT)2 thin films exhibit reliable photoresponses at room temperature in a wavelength region from UV to mid-IR, which is much broader than those of solution-processed broadband photodetectors reported previously. Moreover, the photodetectors can show a typical synaptic behavior and excellent data recognition accuracy in artificial neural networks. This work opens a window for the exploration of high-performance and multifunctional optoelectronic devices based on 2D c-MOFs.

Photodetectors (PDs) are the building block of various imaging and sensing applications. However, commercially available PDs based on crystalline inorganic semiconductors cannot meet the requirements of emerging wearable/implantable applications due to their rigidity and fragility, which creates the need for flexible devices. Here, a high-performance flexible PD is presented by gating an organic electrochemical transistor (OECT) with a perovskite solar cell. Due to the ultrahigh transconductance of the OECT, the device demonstrates a high gain of ≈106 , a fast response time of 67 µs and an ultrahigh detectivity of 6.7 × 1017 Jones to light signals under a low working voltage (≤0.6 V). Thanks to the ultrahigh sensitivity and fast response, the device can track photoplethysmogram signals and peripheral oxygen saturation under ambient light and even provide contactless remote sensing, offering a low-power and convenient way for continuous vital signs monitoring. This work offers a novel strategy for realizing high-performance flexible PDs that are promising for low-power, user-friendly and wearable optoelectronics.

The outbreak of COVID-19 and its continued spread have seriously threatened public health. Antibody testing is essential for infection diagnosis, seroepidemiological analysis, and vaccine evaluation. However, convenient, fast, and accurate antibody detection remains a challenge in this protracted battle. Here, we report an ultrafast, lowcost, label-free, and portable SARS-CoV-2 immunoglobulin G (IgG) detection platform based on organic electrochemical transistors (OECTs), which can be remotely controlled by a mobile phone. To enable faster detection, voltage pulses are applied on the gate electrode of the OECT to accelerate binding between the antibody and antigen. By optimizing ion concentrations and pH values of test solutions, we realize specific detection of SARS-CoV-2 IgG in several minutes with a detectable region from 10 fM to 100 nM, which encompasses the range of serum SARS-CoV-2 IgG levels in humans. These portable sensors show promise for use in diagnosis and prognosis of COVID-19.

An n-type solution-gated MOF transistor (SGMT) is realized for the first time. The device is exploited as a low-voltage dopamine sensor, exhibiting high sensitivity and selectivity.

A novel introduction of an amorphous functional layer in perovskite films significantly improved the efficiency and stability of perovskite solar cells.

Agricultural soils are under threat of toxic metal/metalloid contamination from anthropogenic activities,leading to excessive accumulation of arsenic (As),cadmium (Cd),lead (Pb),and mercury (Hg) in food crops that poses significant risks to human health.Understanding how these toxic metals and their methylated species are taken up,translocated,and detoxified is prerequisite to developing strategies to limit their accumulation for safer food.Toxic metals are taken up and transported across different cellular compart-ments and plant tissues via various transporters for essential or beneficial nutrients,e.g.As by phosphate and silicon transporters,and Cd by manganese (Mn),zinc (Zn),and iron (Fe) transporters.These transport processes are subjected to interactions with nutrients and the regulation at the transcriptional and post-translational levels.Complexation with thiol-rich compounds,such as phytochelatins,and sequestration in the vacuoles are the common mechanisms for detoxification and for limiting their translocation.A num-ber of genes involved in toxic metal uptake,transport,and detoxification have been identified,offering tar-gets for genetic manipulation via gene editing or transgenic technologies.Natural variations in toxic metal accumulation exist within crop germplasm,and some of the quantitative trait loci underlying these variations have been cloned,paving the way for marker-assisted breeding of low metal accumulation crops.Using plants to extract and remove toxic metals from soil is also possible,but this phytoremediation approach requires metal hyperaccumulation for efficiency.Knowledge gaps and future research needs are also discussed.

Abstract 2D Ruddlesden–Popper perovskites have attracted wide attention recently because of tunable optoelectronic properties and have been used as alternatives to their 3D counterparts in various optoelectronic devices. Here, a series of (PEA)2(MA)n−1PbnI3n+1 perovskite thin films is designed and fabricated by a convenient hot‐casting method to obtain gradient n in the films, which leads to the formation of vertical heterojunctions that can enhance charge separation in the films under light illumination. Based on a single gradient perovskite film, a highly sensitive and stable photodetector with a responsivity up to 149 AW−1 and a specific detectivity of 2 × 1012 Jones is obtained. This work paves a way to realizing high‐performance optoelectronic devices with enhanced charge separation by introducing compositional gradient in a perovskite film.

Caspase-3 is an important proteolytic enzyme that cleaves several key substrates in apoptotic processes, resulting in DNA fragmentation, the degradation of nuclear proteins, and the formation of apoptotic bodies. However, it is challenging to detect caspase-3 due to its low expression levels in cells. In this work, organic electrochemical transistors (OECTs) are used in the detection of caspase-3 for the first time. A self-assembled monolayer of the peptide is bonded to the Au gate electrode (GE) of an OECT via gold-sulphur bonds. It is found that the transfer curve of the transistor shifts to a lower gate voltage due to the modulation of the surface potential of the GE by the peptides. Then, the device is used in the detection of caspase-3 in aqueous solutions and shows a detection limit of 0.1 pM. Due to its high sensitivity, the device can detect caspase-3 in induced apoptotic HeLa cells. The system is low-cost, conveniently used and applicable for biological and medical monitoring where caspase-3 detection and quantification are required.

Electrolyte‐gated organic electrochemical transistors (OECTs) are attractive for synaptic electronics owing to the ionic–electronic coupling, huge specific capacitance, physiological environmental compatibility, and architectural flexibility. Here, an identical spike‐polarity method is reported to realize the concomitance of excitatory and inhibitory short‐term plasticities in unipolar poly(3,4‐ethylenedioxythiophene)–poly(styrenesulphonate) (PEDOT:PSS) OECTs. Dynamical reconfiguration between the excitatory and inhibitory responses with multilevel and well‐balanced synaptic strength is realized, without performing operations or introducing additional modulation terminals. Owing to the distinctive volumetric capacitance of OECTs, the PEDOT:PSS synapse affords remarkable characteristics such as an ultrahigh stimulus‐resolution capability of 10 mV and an ultralow power consumption of ≈2 pJ per spike. Moreover, spatiotemporal‐correlated logics is realized. This work demonstrates on‐demand manipulation of ionic dynamics for building synaptic elements with sophisticated functionalities at a single‐device level.

Organic bioelectronics have shown promising applications for various sensing purposes due to their significant advantages in term of high flexibility, portability, easy fabrication, and biocompatibility. Here, a new type of organic device, organic photo‐electrochemical transistor (OPECT), is reported, which is the combination of an organic electrochemical transistor and a photo‐electrochemical gate electrode modified with CdS quantum dots (QDs). Thanks to the inherent amplification function of the transistor, the OPECT‐based biosensor exhibits much higher sensitivity than that of a traditional biosensor. The sensing mechanism of the OPECT is attributed to the charge transfer between the photosensitive semiconductor CdS QDs and the gate electrode. In an OPECT‐based DNA sensor, target DNA is labeled with Au nanoparticles (NPs) and captured on the gate electrode, which can influence the charge transfer on the gate caused by the exciton–plasmon interactions between CdS QDs and Au NPs. Consequently, a highly sensitive and selective DNA sensor with a detection limit of around 1 × 10 −15 m is realized. It is expected that OPECTs can be developed as a high‐performance platform for numerous biological detections in the future.

An organic electrochemical transistor (OECT) based on poly(3,4-ethylenedioxythiophene): polystyrene sulfonate with porous anodic aluminum oxide (AAO) as a gate electrode was proposed for DNA sensing. The AAO substrate, which possesses a pore size of 200 nm, underwent gold nanofilm deposition by the thermal evaporation technique and is referred to as a nanoporous gold electrode in this work. Due to its high sensitivity, target DNA as low as 0.1 nM in concentration was achieved on an OECT device with a nanoporous gold gate electrode using a peptide nucleic acid probe. One-base and two-base mismatched DNA sequences could be discriminated. A sensing mechanism for the OECT device based on the nanoporous gold electrode was proposed. The synergetic effect of capacitance with the surface potential on the nanoporous gold electrode enlarged the increase in gate potential, which resulted in high sensitivity for DNA sensing.