Thermal properties of different transition metal forms of montmorillonite intercalated with mono-, di-, and triethanolammonium compounds

In the present study, different transition metal forms of montmorillonite have been intercalated with mono-, di-, and triethanolammonium cations via d coordination mechanism to investigate their thermal behavior, structural characteristics, surface properties, and elemental composition using TG, XRD, BET, and CHNS techniques. Thermogravimetric analysis showed two thermal transition steps for transition metal-exchanged montmorillonites, which attributed to desorption of the physically adsorbed water and hydrated water, and dehydroxylation of the structural water; whereas for ammonium-montmorillonite complexes, the TG curves showed three thermal transition steps which attributed to desorption of the adsorbed water and dehydration, decomposition of the ammonium cations in the interlayer space of montmorillonite, and the dehydroxylation of the structural water. The thermal analysis of ammonium-montmorillonites affirmed that the molar mass of amine compounds used affects both desorption temperature (position) and the amount of the adsorbed water (intensity). XRD results revealed that the molar mass of amine used has linear relation with the basal spacings of the corresponding ammonium-montmorillonites, indicating structural changes. BET results showed that the molar mass of amines has an inverse effect on the surface area of the studied samples. CHNS analysis for the studied samples quantitatively confirmed the intercalation of ammonium cations into the interlayer space of montmorillonite.     

Photogeneration of reactive oxygen species and photoinduced plasmid DNA cleavage by novel synthetic chalcones

This paper describes the synthesis and photodynamic properties of six different chalcone derivatives. Using N,N-dimethyl-4-nitrosoaniline (RNO) bleaching assay, the singlet oxygen generating efficiencies of these chalcones are determined relative to rose bengal (RB). Superoxide dismutase (SOD) inhibitable cytochrome c reduction assay and electron magnetic resonance (EMR) spin trapping techniques are used to determine the superoxide anion radical (O?·?) yield upon photoirradiation. Photoinduced DNA scission studies show that O?·? is involved in the DNA strand break. In addition, antimicrobial activity of these chalcones is also investigated. Structure activity relationship accounts for the difference in the photogeneration of reactive oxygen species (ROS) by these sensitizers. Presence of electron releasing -OCH? groups enhances the photogeneration of ROS. Cyclic voltammetry studies indicate a correlation between enzymatic O?·? generation efficiency and redox potential of chalcones. Both O?·? (Type I) and 1O? (Type II) paths are involved in the photosensitization of chalcones. The LUMO energies obtained by molecular modeling correlate with the one-electron reduction potentials.     

A New Sodium Thioborate Fast Ion Conductor: Na3B5S9

We report a new sodium fast-ion conductor, Na₃B₅S₉, that exhibits a high Na ion total conductivity of 0.80 mS cm⁻¹ (sintered pellet; cold-pressed pellet=0.21 mS cm⁻¹). The structure consists of corner-sharing B₁₀S₂₀ supertetrahedral clusters, which create a framework that supports 3D Na ion diffusion channels. The Na ions are well-distributed in the channels and form a disordered sublattice spanning five Na crystallographic sites. The combination of structural elucidation via single crystal X-ray diffraction and powder synchrotron X-ray diffraction at variable temperatures, solid-state nuclear magnetic resonance spectra and ab initio molecular dynamics simulations reveal high Na-ion mobility (predicted conductivity: 0.96 mS cm⁻¹) and the nature of the 3D diffusion pathways. Notably, the Na ion sublattice orders at low temperatures, resulting in isolated Na polyhedra and thus much lower ionic conductivity. This highlights the importance of a disordered Na ion sublattice—and existence of well-connected Na ion migration pathways formed via face-sharing polyhedra—in dictating Na ion diffusion.