Nominal Effect of Mg Intercalation on the Superconducting Properties of 2H-NbSe2.

2H-NbSe2 is a phonon-mediated, Fermi-surface topology-dependent multiband superconductor with an incommensurate charge-density wave (CDW) that coexists at a local level with superconductivity. Usually, the intercalation in 2H-NbSe2 enriches the CDW, enhances the c-axis lattice parameter, and distorts the Fermi surface, which result in a decrease in the superconducting transition temperature (Tc). The rate of decrease of Tc depends on the electronic structure, size, valence, magnetic nature, and electronegativity of the intercalating species. Herein, we report an unusual effect of Mg intercalation on the superconductivity of 2H-MgxNbSe2 (x = 0.0, 0.02, 0.06, 0.08, 0.10, and 0.12) synthesized by a high-temperature solid-state reaction method. Unlike other s- and p-block elements/species as intercalants (Rb, Sn, Ga, and Al) that have a sharp detrimental effect on the Tc of 2H-NbSe2 within 1-5% of intercalation, Mg is found to be an exception. Upon Mg intercalation up to x = 0.06, no remarkable changes in Tc as compared to the parent 2H-NbSe2 (Tc ∼ 6.7 K) are observed, and further intercalation results in a small decrease in Tc (for x = 0.12, Tc = 6.2 K). From heat-capacity measurements, it is inferred that superconducting Mg-intercalated 2H-NbSe2 exhibits strong electron-phonon coupling. Electronic structure calculations on two s-block element intercalated compounds of formula M0.125NbSe2 (M = Mg, Rb) show that Rb s-, p-, and d-states completely overlap with the Nb d states, while the Mg s states lie in a low-energy region as compared to Nb d states, indicating a weak interaction between the intercalant and the Nb sublattice in Mg0.125NbSe2 as compared to Rb0.125NbSe2. These results suggest that the electronic states of the Nb network in 2H-NbSe2 are least altered with Mg intercalation, which could be one of the reasons for the minimal effect on the Tc with intercalation.

In vitro biosynthesis and genotoxicity bioassay of silver nanoparticles using plants.

Silver nanoparticles (AgNP-P) from AgNO(3) were synthesized by using the broth prepared from the aromatic spath of male inflorescence of screw pine, Pandanus odorifer (Forssk.) Kuntze AgNP-P was then characterized by UV-visible spectroscopy, transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Functional groups in the broth were analyzed by Fourier Transform infrared spectroscopy (FTIR). Genotoxicity of AgNP-P was assessed by utilizing our well-established Allium cepa assay system with biomarkers including the generation reactive oxygen species (ROS: O(2)(·-) and H(2)O(2)), cell death, mitotic index, micronucleus, mitotic aberrations; and DNA damage by Comet assay. Other chemical forms of silver such as Ag(+) ion, colloidal AgCl, and AgNP-S at doses 0-80 mg L(-1) were included for comparison with AgNP-P. The results revealed that AgNP-P and AgNP-S exhibited similar biological effects in causing lesser extent of cytotoxicity and greater extent of genotoxicity than that was exhibited by Ag(+) ion alone. Among different tested chemical forms of silver, colloidal AgCl was identified to be the least cytotoxic and genotoxic. Cell death and DNA-damage induced by AgNP-P were prevented by Tiron and dimethyl thiourea that scavenge O(2)(·-) and H(2)O(2), respectively. The present findings demonstrated the role of ROS in the AgNP-induced cell death and DNA damage.