The cell structures and mechanical properties (i.e., hardness, Young's modulus , shear modulus , and Poisson's ratio) of (Hf 0.2 Zr 0.2 Ti 0.2 Nb 0.2 Ta 0.2 )C (HEC) and (Hf 0.2 Zr 0.2 Ti 0.2 Nb 0.2 Ta 0.2 )N (HEN) high-entropy ceramics were simulated by special quasi-random structure (SQS) and general random structure (GRS) with atomic occupation preference based on the first-principles density functional theory. The results show that compared to SQS, the cell structure constructed by GRS is more realistic, which is verified via scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive spectroscopy. The mechanical properties simulated by GRS were also determined by microhardness and dynamic elastic modulus testers. The hardness, Young's modulus，shear modulus and Poisson's ratio predicted by GRS are 23.07 GPa, 449.71 GPa, 183.28 and 0.227 for HEC and 22.96 GPa, 413.71 GPa, 162.47 and 0.241 for HEN, which are in a reasonable agreement with the measured results (i.e., 22.05 ± 0.32 GPa, 433 ± 12 GPa, 172 ± 18 GPa, 0.21 for HEC and 22.12 ± 0.13 GPa, 372 ± 23 GPa, 158 ± 11 GPa, 0.23 for HEN). This work can provide a promising reference for preparing high-entropy non-oxide ceramics via the prediction.
Flap endonuclease 1 (FEN1), a ubiquitous enzyme involved in DNA repair and replication, is overexpressed in highly proliferative cancer cells. FEN1 has been recognized as a promising diagnostic marker of cancers; however, very few analytical techniques have been developed for the convenient detection of FEN1. To realize the simplified quantification of FEN1, we developed a FEN1-responsive fluorescent nanoprobe based on DNA-silver nanoclusters (DNA-AgNCs). The nanoprobe was rationally designed with a double-flapped dumbbell conformation, where its 5′ flap was produced with DNA-AgNCs, and the 3′ flap was elongated by a guanine-rich enhancer sequence (GRS). Rigidified by the DNA scaffold, DNA-AgNCs and the GRS are in close proximity, resulting in high fluorescence because of the GRS-induced activation of DNA-AgNCs. Upon the addition of FEN1, the 5’ flap of the nanoprobe is cleaved due to the structure-specific endonuclease activity of FEN1. This cleavage released the DNA-AgNCs from the nanoprobe, broke the proximity between DNA-AgNCs and the GRS, and caused decreased fluorescence. This nanoprobe can be applied in the sensitive detection of FEN1 with a detection limit of 40 fM, and it showed high specificity for the monitoring of FEN1 in clinical samples. As the first attempt to develop biosensors targeting FEN1 based on DNA-AgNCs, this work provided a potent platform for monitoring FEN1 and screening FEN1 inhibitors.
危险品化学品经营许可证（带存储）