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Constructing low cost and efficient electrochemical sensors for highly sensitive detection of hydrazine has a great significance in the field of environmental monitoring and protection. Herein, metal–organic framework derived Co3S4 nanosheets grown on Ti mesh (Co3S4/TM) were successfully synthesized by employing a facile anion exchange reaction and hydrothermal vulcanization with Co-MOF as the precursor. The crystalline structure and morphology of as-synthesized samples were characterized by XRD, SEM, Raman, XPS and TEM analysis. It was found that Co3S4 nanosheets were stacked loosely and irregularly on each other to form a three-dimensional (3D) porous structure. The electrochemical sensing performance of Co3S4/TM toward hydrazine was investigated in 0.1 M NaOH solution. The results showed that Co3S4/TM presented a better electrocatalytic activity toward hydrazine oxidation than Co-MOF/TM and Co(OH)2/TM, owing to the high electrical conductivity of Co3S4 for enhancing electron transfer and the 3D porous structure for providing many more accessible active sites and shortening ion diffusion length as well as promoting mass transfer for hydrazine electrooxidation. As a result, Co3S4/TM exhibited a superior analytical performance with a wide linear range of 0.005–2.0 mM, a high sensitivity of 2956 μA mM−1 cm−2 and a low detection limit of 0.7 μM (S/N = 3), which was superior or comparable to that of the recently reported sensor. Because of the good selectivity and reproducibility, Co3S4/TM was applied to detection of hydrazine in tap water and it showed good recovery, indicating that it could be a promising candidate for analyzing hydrazine in practical application. [ABSTRACT FROM AUTHOR]

Invasion and migration are major characteristics of malignant cancers. Inhibiting the migration of cancer cells, rather than simply removing the primary tumor, is essential for improving the survival rates. Two-dimensional (2D) materials have important application prospects in the field of biomedicine (especially in cancer therapy) due to their unique physicochemical properties. However, the basic biological effects of 2D material cobalt-based layered double hydroxides, especially its cytotoxicity and migration effects on a variety of cells, have not yet been revealed. Herein, the effect of 5 nm thick β-Co(OH)2 nanosheets (NSs) on cell viability and migration of normal cells and various cancer cells and their possible mechanisms were investigated. The cell viability assay and migration ability analysis found that β-Co(OH)2 NSs had a concentration-dependent and selective biological effects on normal cells HUVEC and cancer cells (4T1, SMMC-7721, and B16 cells). Compared with normal cells HUVEC, β-Co(OH)2 NSs showed remarkably stronger and differentiated cytotoxicity to cancer cells (4T1, SMMC-7721, and B16 cells), and it was found by wound healing and transwell assays that β-Co(OH)2 NSs also can inhibit cancer cell migration more sensitively which may be attributed to the down-regulation of the key epithelial-mesenchymal transition protein Snail2. This study on revealing the basic biological effects of cobalt-based nanosheets will not only promote the understanding of the interaction between nanosheets and cells, but will also help in developing cancer treatment platforms based on cobalt-based nanosheets to promote their applications in the inhibition of tumor migration and metastasis. [ABSTRACT FROM AUTHOR]

Three-dimensional interconnected Co(OH)2 nanosheets (Co(OH)2 NS) were electrodeposited onto a Ti mesh (TM) surface, which was demonstrated by XRD, Raman spectroscopy, XPS and SEM characterization. The electrochemical sensing performance of the Co(OH)2 NS/TM toward hydrazine was investigated by cyclic voltammetry and amperometric techniques in a 0.1 M NaOH aqueous solution. The as-prepared Co(OH)2 NS/TM with an electrodeposition time of 10 min exhibited prominent capacity to detect hydrazine with a wide linear range from 5 μM to 3.0 mM and limit of detection (LOD) of 1.98 μM. Co(OH)2 NS/TM electrodes also showed a high sensitivity of 2793.9 μA mM−1 cm−2, excellent selectivity, reproducibility, appreciable stability with a RSD less than 3.5%, as well as the high recovery of hydrazine in real samples, indicating its potential application in real sample analysis. [ABSTRACT FROM AUTHOR]