Spectral anion sensing and gamma-radiation induced magnetic modifications of polyphenol generated Ag-nanoparticles

International audienceA fast one step bio-synthesis for in situ preparation of silver nanoparticles is proposed. The method involves reduction of AgNO3 with an aqueous extract of peanut skin, which is a good source of polyphenols. The silver nanoparticles thus synthesized were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis absorption spectroscopy, Fourier Transform infrared (FTIR) spectroscopy and magnetic measurements. Effect of low dose gamma irradiation during the synthesis was studied and their physico-chemical properties were compared with those produced without irradiation. On the contrary to the diamagnetic behavior of bulk silver, the silver nanoparticles thus prepared show a significant ferromagnetic moment component. Variable time exposure to gamma-irradiation results in an exponential decay of ferromagnetic component. A freshly prepared solution of silver nanoparticles shows selective spectral changes towards iodide ions at trace concentration (below 50 muM) among a series of 16 other competing anions. The prepared nanoparticles are therefore suitable for anion sensing application

Four new dinuclear Cu(ii) hydrazone complexes using various organic spacers: syntheses, crystal structures, DNA binding and cleavage studies and selective cell inhibitory effect towards leukemic and normal lymphocytes

Syntheses and crystal structures of four new hydrazone-based Cu(II) complexes, [{Cu(L1)(H2O)}2(m-pyraz)](ClO4)2 (1), [{Cu(L1)(OClO3)}2(m-4,4¢-bipy)] (2), [{Cu(L2H)}(m-pyraz){Cu(L2H)(OClO3)}].(ClO4) (3) and [{Cu(L2)}2(m-bpe)] (4) [L1H = condensation product of benzhydrazide and pyridine-2-carbaldehyde and L2H2 = condensation product of benzoyl acetone and benzhydrazide], bridged by various organic spacers [pyrazine (pyraz), 4,4¢-bipyridine (4,4¢-bipy) and 1,2-di(4-pyridyl)ethane (bpe)] are reported in this paper. The single-crystal X-ray crystallographic studies reveal that all are dinuclear units where 1 and 3 form strong intermolecular H-bonding to form sheets of interconnected ions, whereas 2 forms sheets of dinuclear chains through p–p interactions; in 4, molecules are linked only through van der Waals interactions. The variable-temperature magnetic moment studies reveal that 1 and 3 show antiferromagnetic coupling between the Cu(II) centers at lower temperatures. The binding ability of 1 with calf thymus DNA [CT-DNA] is reported using various spectroscopic studies (UV-Vis titration, circular dichroism and fluorescence). The binding constants of 1 with CT-DNA, as calculated by different methodologies, are of the order of 105 M-1. The mode of interaction between 1 and CT-DNA has been predicted using circular dichroic (CD) spectroscopy, where it has been shown that 1 most probably interacts with DNA via intercalation between the base pairs leading to a change in B-DNA conformation. 1 is also able to cleave supercoiled (SC) plasmid DNA pUC19 in a time and dose dependent manner as demonstrated by agarose gel electrophoresis, and also demonstrates its potential to cleave the SC plasmid DNA via both oxidative and hydrolytic mechanisms. Approximately 50% of leukemic cells are found to be dead when two representative leukemic cell lines are exposed to 1 (~80 mM) even for 24 h as determined by different cell cytotoxicity assays. Preliminary results also showed that, at 20 mM, 1 could selectively induce apoptosis in leukemic cells without affecting normal lymphocytes