Enzyme biosensors, despite their high specificity and sensitivity, are constrained by the inherent fragility of enzymes. Despite being considered ideal for enzyme protection by in-situ covalent organic frameworks (COFs) immobilization, the harsh conditions of COFs synthesis often lead to enzyme inactivation. Herein, a strategy was developed to prepare robust enzyme@COFs microcapsules (enzyme@MC_COFs) by the interfacial assembly of hydrophobic COFs spheres to form stable Pickering emulsions, followed by COFs regrowth to reinforce the microcapsules. Compared with conventional methods, this approach confines the enzymes in a mild environment, achievig an impressive encapsulation efficiency of 85.9 %. Enzymes are protected from inhospitable conditions by the mechanical robustness of microcapsules COFs shell which also features adjustable pores to enhance substrate transport and exhibit size selectivity. The success of strategy was verified by the construction of enzyme@MC_COFs based on various hydrophobic COFs spheres (water contact angle>90°) with different pore sizes and degrees of functionalization, and they can be pre-modified to meet specific application requirements. The strategy is simple yet effective. COFs employed in this strategy only requires a slight degree of hydrophobicity, rather than specific functional groups. In addition, a formula was also proposed to predict and control the size of the enzyme@MC_COFs accurately. A cascade catalytic system based on enzyme@MC_COFs has been emulated for the construction of a colorimetric and electrochemical glucose biosensing platform. This study provides new insight into the construction of enzyme@MC_COFs and their biosensing applications.

Acetaminophen (APAP), also known as paracetamol, is a widely used analgesic and antipyretic, but its metabolites are toxic and can cause liver damage when used in excess. Rapid detection of APAP is essential, and conventional methods such as HPLC and GC are expensive and complex. To this purpose, we successfully prepared CoO/Co₃O₄/NC porous carbon composites with large specific surface area, homogeneous pore structure, and abundant adsorption active sites as electrochemical sensors for the rapid, simple, and inexpensive detection of acetaminophen. The CoO/Co₃O₄/NC porous carbon composites were prepared by doping Co²⁺ and calcining, and a large number of N and O metal chelate sites in COF_TZT-DVA could coordinate with Co²⁺, which effectively suppressed the aggregation phenomenon of CoO/Co₃O₄ in the composites, and realized the uniform dispersion of Co²⁺. This composite material not only has excellent stability, but also exhibits excellent catalytic performance. The experimental results showed that the sensor had an extremely low detection limit (0.79 μM) and a wide linear response range (2.5 μM–423 μM), and the sensitivity was up to 2000 μA mM⁻¹ cm⁻². This study provides a new strategy for the preparation of high-performance paracetamol sensors.

Silicon nanochannels possess adjustable structural characteristics and excellent mechanical properties, and have great application potential in nanoelectromechanical systems, seawater desalination, and nanoreactors. However, achieving controllable synthesis and precise structural modulation remains highly challenging. Metal-assisted chemical etching (MACE), with its advantages of simple operation and low cost, has been widely used in the fabrication of silicon nanochannels. This study systematically investigates the morphological regulation mechanism of silicon nanochannels prepared via MACE, with a focus on analyzing the influence of etching solution composition, gold nanoparticle microstructure, and reaction time on the formation of helical structures. By combining thermomechanical molding for replicating nanochannel structures with electron microscopy characterization, comprehensive morphological analysis was achieved. The results indicate that an etching solution ratio of HF:H₂O₂:H₂O = 6:4:5 (v/v/v) yields helical nanochannels with greater length and higher yield. Increasing the HF proportion promotes the formation of helical structures; however, excessively high HF concentration leads to severe lateral etching, inhibiting deep channel propagation. The study further reveals an externally-driven mechanism for helical structure formation: the hydrogen bubbles generated during the reaction and the flow of the etching solution exert thrust on the nanoparticles, causing them to move and carve helical pathways.