Fujian Normal University

Au NRs/HA/CMC-PVA hydrogel membranes were successfully prepared by mixing sodium hyaluronate (HA) and carboxymethyl cellulose (CMC) solutions for immersion crosslinking on the basis of freeze-thaw crosslinking of polyvinyl alcohol (PVA) with gold nanorods (Au NRs). By adjusting the density of Au NRs and the concentrations of CMC and HA, more 'hot spots' could be generated to enhance the SERS signals, thus improving the sensitivity and homogeneity of the hydrogels (low detection limit of 10^-9 mol/L Rhodamine 6G (R6G), RSD = 3.04 %). Meanwhile, the strong hydrogen bonds formed in the hydrogel network were utilized to increase the cross-linking degree of the hydrogels, which led to the improvement of the mechanical properties and flexural flexibility of the hydrogels (elongation at break of 308.07 % and tensile strength of 26.09 MPa). The hydrophilic groups of the Au NRs/HA/CMC-PVA hydrogel film were able to adsorb sweat and diffuse urea molecules from sweat into the hydrogel. It showed high sensitivity for the detection of urea, exhibiting a linear relationship at concentrations of 1000-1 mM, with a LOD = 7.83 × 10^-5 M.

A novel nanocomposite hydrogel-based Surface-enhanced Raman scattering (SERS) platform was successfully fabricated using Ag NPs/S-CNF/PVA hydrogel as the core matrix, demonstrating exceptional swelling-deswelling behavior. By evenly distributing a large number of Ag NPs on the surface of S-CNF, a one-dimensional tightly arranged "hot spot" was successfully constructed, which significantly improved the SERS effect and improved the sensitivity and uniformity of the SERS platform. The experimental results show that Rhodamine 6G (R6G) of 10^-7 M can be detected, RSD = 1.90 %. At the same time, PVA hydrogel, as an excellent packaging material, can effectively isolate Ag NPs/S-CNF/PVA composite from the external environment, which helps to maintain the SERS property of the film, but also makes the film more durable and reliable in practical applications. By using different signal molecule modification, different substances were determined. It is worth mentioning that the substrate showed excellent SERS activity on glucose and pH, which has the potential to be applied in non-invasive tear glucose and pH monitoring system. Given its excellent flexibility and repeatability, the substrate is expected to be integrated into a variety of wearable biosensors, thus advancing the development of biological process research. Overall, by combining a flexible SERS 3D substrate, this approach shows great potential and application prospects in the study of biological processes.

Driven by the urgent need for eco-friendly, safe and facile production processes for hydrogen peroxide (H₂O₂), piezocatalysis shows significant potential due to its accessible energy supply and capacity for on-site H₂O₂ preparation. Owing to their tunable surface properties and unique electronic structures, transition metal dichalcogenides (TMDCs) are regarded as promising piezocatalysts. Nevertheless, the uneven distribution of active sites, poor stability, and restricted electron transport capabilities hinder the further improvement of their piezocatalytic performance. In this study, WS₂ thin sheets were prepared by liquid-phase stripping, which significantly increase the number of exposed active sites to provide an optimized interfacial environment for the adsorption of reactant molecules, and the resulting thin-layer structure greatly improves the charge transfer efficiency. More importantly, WS₂ thin sheets were utilized in piezocatalytic H₂O₂ evolution. Remarkably, under conditions of pure water and ambient air, these thin sheets exhibit outstanding piezocatalytic performance with an H₂O₂ evolution rate as high as 994.7 μmol g^-1 h^-1. And they retained 80.14 % of their activity after 10 h of cyclic operation, demonstrating excellent cycling stability. Furthermore, mechanistic investigations propose three potential pathways for H₂O₂ evolution, providing a novel perspective for elucidating the underlying mechanism of piezocatalysis in TMDCs.