Organic electrochemical transistors (OECTs) have garnered significant interest due to their ability to facilitate both ionic and electronic transport. A large proportion of research efforts thus far have focused on investigating high-performance materials that can serve as mixed ion doping and charge transport layers. However, relatively less attention has been given to the gate-electrode materials, which play a critical role in controlling operational voltage, redox processes, and stability, especially in the context of semiconductor-based OECTs working in accumulation mode. Moreover, the demand for planarity and flexibility in modern bioelectronic devices presents significant challenges for the commonly used Ag/AgCl electrodes in OECTs. Herein, we report the construction of high-performance accumulation-mode OECTs by utilizing a gate electrode made of three-dimensional (3D)-printed graphene oxide. The 3D-printed graphene oxide electrode incorporating one-dimensional (1D) carbon nanotubes, is directly printed using an aqueous-based ink and showcases exceptional mechanical flexibility and porosity properties, enabling high-throughput preparation for both top gates and integrated planar architecture, as well as fast ion/charge transport. OECTs with high performance comparable to that of Ag/AgCl-gated OECTs are thus achieved and present promising feasibility for electrocardiograph (ECG) signal recording. This provides a promising choice for the application of flexible bioelectronics in medical care and neurological recording.

The fabrication of surface enhanced Raman spectroscopy (SERS) substrates with controlled high density hot spots still remains challenging. Herein, we report highly effective SERS substrates containing the self-generating (SG) nanogaps from polystyrene nanosphere monolayer through isotropic plasma etching. The emergence of multimode hot spots, i.e., metal film over nanosphere (MFON)-like hot spots (closed gaps, 0 nm), individual self-aligned hot spots (discrete gaps, > 20 nm) and three-dimensional (3D) hot spots (nanogaps, 1–10 nm), makes the SG SERS substrates superior as compared to the traditional MFON or the well-ordered self-aligned SERS substrates in terms of enhancement, uniformity, and reproducibility. The SG SERS substrates can function as the excellent SERS platforms for trace molecule detection in the practical application fields.

The traditional single material with two-dimensional (2D) biomimetic moth-eye structures is limited by its narrowband antireflection and single functional capability. To overcome these disadvantages, we exploited wet etching and hydrothermal synthesis coupled with chemical oxidation for fabricating a three- dimensional (3D) biomimetic moth-eye coating with ternary materials (polypyrrole nanoparticles, TiO₂ nanorods, and Si micropyramids, i.e., PPy/TiO₂/Si-p). This coating reduced the reflectivity to < 4% at wavelengths ranging from 200 to 2, 300 nm and exhibited remarkable superhydrophilicity with a low water contact angle of 1.8°. Moreover, the composite coating had double p-n heterojunctions, allowing the high-efficiency separation of photogenerated carriers. The photocurrent density of PPy/TiO₂/Si-p was more than three times higher than that of TiO₂/Si-p at a positive potential of 1.5 V. The proposed method provides a means to enhance solar energy conversion.