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[Display omitted] • N-POP (COFs) with microporous structure and high nitrogen content was synthesized. • The multifunctional support favors controllable AuNPs growth on the surface. • The N-riched porous structure of N-POP showed synergistic effect on catalytic activity of AuNPs toward As(III) reduction. • The chemical changes brought about by the N-POP are responsible of stable catalytic performance toward As(III) reduction. • It was successfully implemented in the determination of As(III) in real samples with good recoveries. An effective electrochemical sensing platform for As(III) determination was developed through in situ growing gold nanoparticles electrocatalyst inside the highly microporous melamine-based chemical organic framework (N-POP) with a large surface area prepared through the catalyst-free polycondensation between melamine and terephthalaldehyde. The microporous structure afforded support for the synchronous anchoring of more gold nanoparticles and exposing abundant unsaturated active sites for highly sensitive As(III) detection. The optimized synthesis was characterized by FT-IR, SEM, HR-TEM, UV–Vis, and XPS successful formation of the polymer, and the morphologically favorable heterojunction between AuNPs and the N-POP gave rise to enhanced electrochemical responses toward As(III) determination. Several parameters related to the synthesis of the nanocomposite and instrumental parameters were optimized to achieve the best performance of the sensor. Under optimized conditions, the electrode exhibits enhanced electrochemical performance toward As(III) without noticeable interference from other commonly coexisting ions on the determination of As(III). Additionally, robust stability and reproducibility were achieved for the electrodes. While this work forms the basis for further progress on nanomaterials-coated COFs, As(III) detection in different water samples was successfully demonstrated here. [ABSTRACT FROM AUTHOR]

Achieving efficient chiral discrimination by a convenient method remains a challenge in pharmaceutical and biotechnology industries. Our aim in this paper was to develop a dual-signaling enantioselective sensing strategy based on the competitive binding assay. A combination of β-cyclodextrin (β-CD) and methylene blue (MB) was used as an enantioselective discrimination probe to develop a straightforward electrochemical chiral sensor using the drug naproxen (R-and S-NaX) as the representative enantiomers. The principle relied on the difference between two enantiomers in the ability to replace a pre-binding redox probe, which in turn resulted in different dual signals for the two enantiomers. The applicability of the optimized procedure was demonstrated by the analysis of NaX enantiomers in the range of 0.4–6.0 μM. Featuring both signal-on and signal-off elements, the electrode presented significantly enhanced electrochemical activity with a low limit of detection (LOD) of 0.07 μM. We expect that our work will inspire interesting engineering strategies for developing novel enantioselective electrochemical sensors. [ABSTRACT FROM AUTHOR]

• S-doped C 3 N 4 synthesized by in situ thermal co-polymerization of urea and APS. • Doping process is responsible for morphological changes in g-C 3 N 4. • Multifunctional support favors controllable AuNPs growth on the surface. • Sensor shows stable catalytic performance. To investigate heteroatom-doped carbon nitride (C 3 N 4) materials as supports, Au nanoparticles anchored on sulfur-doped carbon nitride nanosheets (AuNPs@SCNN) was prepared and used as a catalyst for arsenic electroreduction. Novel SCNN was synthesized for the first time via a simple thermally induced copolymerization route using ammonium persulfate (APS) as a low-cost sulfur source. Thereafter, the SCNN was used to integrate with AuNPs for the benefit of enhancing the quality of assembly and interface between SCNN and AuNPs and improving the catalytic activity of the AuNPs@SCNN nanocatalyst. This optimized assembly was characterized by different techniques, morphologically favorable heterojunction formation between SCNN and AuNPs. More importantly, it was confirmed that the addition of APS during the polymerization of urea not only afforded a significant morphological change from a layered material to a porous structure with many in-plane holes, but also resulted in a higher yield than urea. The electrocatalytic reduction of arsenic was considered at a glassy carbon electrode modified by the composite (AuNPs@SCNN/GCE), which exhibited enhanced electrochemical responses in a wide range of pH conditions with minimal interference of Cu. More distinctly, this robust and repeatable detection method exhibits a linearity range of 0.2–30.0 ppb and a detection limit of 0.07 ppb. The successful determination of arsenic concentration in real water samples also underpins its practical applications in the real world. This promotes innovative design for the synthesis of novel functional nanocomposites. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The SA-CD double-layer hydrogel was fabricated using green synthesized carbon dots. • Carbon dots can improve water swelling, vapor transmission rate, and mechanical properties. • SA-CD double-layer hydrogel is biocompatible, hemostatic, and flexible. In this study, a new double-layer sodium alginate (SA) hydrogel was fabricated using green synthesized carbon dots (CDs). The Urtica dioica was used as a natural precursor to synthesize CDs. The casting/solvent evaporation process was employed to fabricate SA-CD double-layer hydrogel. The properties of the SA-CD double-layer hydrogel were examined, including morphology, swelling, water vapor permeability, mechanical and rheological properties. The results show that SA-CD double-layer hydrogels are biocompatible, hemostatic, and flexible. They also have adequate water swelling, a high rate of water vapor transmission, and better mechanical properties, which make them candidates for biomedical applications such as wound dressing. [ABSTRACT FROM AUTHOR]

Nowadays, many studies are conducted on multilayer hydrogels for wound dressing. On the other hand, considering the emergence of bacterial resistance to common antibiotics, studies on the use of natural essential oils and their derivatives that have antibacterial and antioxidant activity can be useful. Herein, a novel bilayer hydrogel developed from polyvinyl alcohol and chitosan with the incorporation of Saqez essential oil (SEO) was synthesized. The results showed a gel-type structure with specific compression and flexibility, while the microscopic images confirmed the formation of a bilayer hydrogel. Further, the data showed that increasing the concentration of SEO reduces the swelling and water vapor permeability and increases the water retention and hydrophobicity of the hydrogel surface. The effects of the combination of SEO in the bilayer hydrogel led to a strong antioxidant property and increased antimicrobial activity. Also, the in vitro results demonstrated that the bilayer hydrogels are biocompatible, non-toxic, and blood compatible. Finally, the results of the in vivo tests showed that these bilayer hydrogels had good homeostatic efficiency. Overall, the obtained results indicate that these bilayer hydrogels are promising candidates for wound dressing. [Display omitted] [ABSTRACT FROM AUTHOR]