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.

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 −1 Pb n I 3 n +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 × 10 12 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.

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.

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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 m is realized. It is expected that OPECTs can be developed as a high-performance platform for numerous biological detections in the future.