Songrui Wei

C nanosheets can be used as building blocks for various photoelectronic devices, further broadening the application prospects of two-dimensional MXenes.

Abstract As one of the rising 2D materials, niobium‐carbide (Nb 2 C, well‐known as a member of MXene family) has attracted considerable attention owing to its unique physical and chemical properties. In this work, few‐layer Nb 2 C nanosheets (NSs) with large (≈255 nm) and small (≈48 nm) lateral dimensions are obtained via a combination of selective etching and liquid cascade centrifugation. Their relaxation time and photophysics process are systematically investigated by transient absorption spectroscopy, and the size effect is demonstrated by phonon‐bottleneck mechanism. Ultrafast fast relaxation time (37.43 fs) and slow relaxation time (0.5733 ps) are observed due to the symmetric structure and metallicity of Nb 2 C NSs. The nonlinear optical properties of Nb 2 C NSs are studied by Z‐scan technique, and both saturable absorption and reverse‐saturable absorption are observed. According to first principle calculations, these phenomena can be attributed to the special band structure of Nb 2 C near the Fermi level, where two‐photon absorption or multiphoton absorption may occur under the irradiation of long wavelength light. These intriguing results suggest that few‐layer Nb 2 C NSs can be used as building blocks for broadband ultrafast photonics and optoelectronic devices and also hold the potential for breakthrough developments in these fields.

Recent advances in twistronics have revealed tunable optoelectronic properties in twisted bilayer graphene (tBLG), including angle-dependent dielectric responses and enhanced light absorption due to van Hove singularity (VHS). However, achieving high photoresponsivity in tBLG-based sensors typically requires intense illumination. We present an ultrasensitive optoelectronic biosensor integrating tBLG superlattices with Au nanodisks and clustered regularly interspaced short palindromic repeat (CRISPR)-Cas12a via DNA origami. By aligning the 9.4° tBLG's VHS absorption spectrum with Au nanodisks' plasmonic resonance at 60 μW, we achieve a 7-fold photocurrent enhancement over pristine tBLG. CRISPR-Cas12a-mediated trans-cleavage dynamically modulates the local dielectric environment, enabling sub-femtomolar (44.63 attomolar, aM) nucleic acid detection without external amplification. Clinical validation using lung cancer samples shows high concordance with quantitative polymerase chain reaction (qPCR), demonstrating real-time, label-free detection of microRNA (miRNA). This hybrid platform combines moiré-engineered optoelectronics with programmable bio-nanoarrays, offering a scalable solution for precision diagnostics with ultralow detection limits and rapid response times.

Fluxgate magnetic sensors are especially important in detecting weak magnetic fields. The mechanism of a fluxgate magnetic sensor is based on Faraday's law of electromagnetic induction. The structure of a fluxgate magnetic sensor mainly consists of excitation windings, core and sensing windings, similar to the structure of a transformer. To date, they have been applied to many fields such as geophysics and astro-observations, wearable electronic devices and non-destructive testing. In this review, we report the recent progress in both the basic research and applications of fluxgate magnetic sensors, especially in the past two years. Regarding the basic research, we focus on the progress in lowering the noise, better calibration methods and increasing the sensitivity. Concerning applications, we introduce recent work about fluxgate magnetometers on spacecraft, unmanned aerial vehicles, wearable electronic devices and defect detection in coiled tubing. Based on the above work, we hope that we can have a clearer prospect about the future research direction of fluxgate magnetic sensor.

Abstract 2D PbS nanoplatelets (NPLs) form an emerging class of photoactive materials and have been proposed as robust materials for high‐performance optoelectronic devices. However, the main drawback of PbS NPLs is the large lateral size, which inhibits their further investigations and practical applications. In this work, ultra‐small 2D PbS NPLs with uniform lateral size (11.2 ± 1.7 nm) and thickness (3.7 ± 0.9 nm, ≈6 layers) have been successfully fabricated by a facile liquid‐phase exfoliation approach. Their transient optical response and photo‐response behavior are evaluated by femtosecond‐resolved transient absorption and photo‐electrochemical (PEC) measurements. It is shown that the NPLs‐based photodetectors (PDs) exhibit excellent photo‐response performance from UV to the visible range, showing extremely high photo‐responsivity (27.81 mA W −1 ) and remarkable detectivity (3.96 × 10 10 Jones), which are figures of merit outperforming currently reported PEC‐type PDs. The outstanding properties are further analyzed based on the results of first‐principle calculations, including electronic band structure and free energies for the oxygen evolution reaction process. This work highlights promising applications of ultra‐small 2D PbS NPLs with the potential for breakthrough developments also in other fields of optoelectronic devices.