M (M: Cu, Co, Cr or Fe) nanoparticles-loaded metal-organic framework MIL-101(Cr) material by sonication process: Catalytic activity and antibacterial properties

The current study deals with the preparation and development of nanomaterials based on iron, copper, chromium or cobalt to study their antibacterial and catalytic properties. To achieve this, the different metals were dispersed in the material MIL-101(Cr) by an ultrasonic-assisted method and then treated by chemical reduction in order to produce corresponding metal nanoparticles (MNPs). The obtained nanocatalysts MIL-101(Cr)/MNPs were characterized by various techniques such as XRD, XPS, SEM, TEM, FTIR; TGA, XRF, Adsorption-desoprtion of nitrogen at 77 K and UV–vis DR. The results showed that the nanocatalysts consist of a mixture of metal phases and oxides. All the prepared nanocatalysts were evaluated based on their performance in reducing the methylene blue (MB) dye in the presence of NaBH4 as reducing agent, for selection of the optimal catalyst. The best catalytic activity was obtained by the MIL-101 (Cr)/CuNPs nanocatalyst in which 6 min was sufficient to reduce the MB dye and the recorded rate constant kapp was 0.503 min−1. The performance of this catalyst was evaluated by varying the effects of three important parameters such as catalyst loading and the concentration of NaBH4 and MB dye. The study of the effects of these three parameters on the reduction process reveals that more than 99% of MB dye was reduced using 0.6 mM of MB dye, 6.8 mM of NaBH4 and 3 mg of nanocatalyst. The kinetic study shows that the reduction of MB dye by the MOF-101(Cr)/CuNPs nanocatalyst follows pseudo-first order kinetics. In addition, the MIL-101(Cr)/CoNPs and MIL-101(Cr)/CuNPs samples demonstrated efficacy at inhibiting bacterial and fungal growth. Hence, it is concluded through this work that the nature, size and concentration of nanoparticles present in the MOF matrix are the key parameters that can influence the catalytic and antibacterial properties of these MNP-loaded MIL-101(Cr) systems

Ab-initio study of structural, elastic, thermal, electronic and magnetic properties of quaternary Heusler alloys CoMnCrZ (Z = Al, As, Si, Ge)

First-principles approach is used to study the structural, electronic and magnetic properties of CoMnCrZ (Z = Al, Si, Ge and As) quaternary Heusler compounds, using full-potential linearized augmented plane wave (FP-LAPW) scheme within the generalized gradient approximation (GGA). The computed equilibrium lattice parameters agree well with the available theoretical data. The obtained negative formation energy shows that CoMnCrZ (Z = Al, Si, Ge, As) compounds have strong structural stability. The elastic constants Cij are calculated using the total energy variation with strain technique. The polycrystalline elastic moduli (namely: the shear modulus, Young’s modulus, Poisson’s ratio, sound velocities, Debye temperature and melting temperature were derived from the obtained single-crystal elastic constants. The ductility mechanism for the studied compounds is discussed via the elastic constants Cij. Our calculations with the GGA approximation predict that CoMnCrGe, CoMnCrAl, CoMnCrSi and CoMnCrAs are half-metallic ferrimagnets (HMFs) with a half-metallic gap EHM of 0.03 eV, 0.19 eV, 0.34 eV and 0.50 eV for, respectively. We also find that the half-metallicity is maintained on a wide range of lattice constants