Enhancement of electrical conductivity and magnetic properties of bimetallic Schiff base complex on grafting to MWCNTs

In present work, we report a newly synthesized nano-inorganic hybrid magnetic material, [SBCu(II)Gd(III)]@MWCNT-COOH which is obtained by anchoring of a copper(II)–gadolinium(III) heteronuclear bimetallic complex, [triaqua(2-hydroxy-1,3-bis(3-methoxysalicylaldiminato)Cu(II)Gd(III)dinitrato)]nitrate monohydrate, [SBCu(II)Gd(III)] to carboxylated multiwalled carbon nanotubes (MWCNT-COOH) through a chemical method. MWCNT-COOH have been loaded with a number of [SBCu(II)Gd(III)] molecules on their surfaces, which generated multinuclear metal centers. [SBCu(II)Gd(III)]@MWCNT-COOH was characterized by FT-IR, UV–Vis, TGA, powder XRD, Raman spectroscopy, TEM, HRSEM, EDAX and elemental mapping. The DC electrical conductivity of materials was evaluated using two probe method suggesting that [SBCu(II)Gd(III)]@MWCNT-COOH is more conducting than [SBCu(II)Gd(III)]. The increased conductivity of [SBCu(II)Gd(III)]@MWCNT-COOH is confirmed by CV and EIS study. The capacitive and dielectric properties of the materials were investigated by Mott–Schottky electrochemical analysis. The positive value of slope signified n-type semiconducting nature of materials. The lower slope for [SBCu(II)Gd(III)] signified the strong dielectric behavior of the material. The positive shift in flat-band potential of [SBCu(II)Gd(III)]@MWCNT-COOH compared to [SBCu(II)Gd(III)] indicated its more conducting nature. Further small optical band gap obtained for [SBCu(II)Gd(III)]@MWCNT-COOH than [SBCu(II)Gd(III)] by UV–Vis studies suggested better conductivity of nano-inorganic hybrid material. Field dependent magnetization revealed enhanced saturation magnetization, remanent magnetization and coercivity of [SBCu(II)Gd(III)]@MWCNT-COOH due to generation of multinuclear metal centers on carboxylated MWCNTs. The temperature dependent magnetization measurement exhibited overlapping of field cooled and zero field cooled curves in entire temperature range (2–300 K), suggests intrinsic ferromagnetism in [SBCu(II)Gd(III)]@MWCNT-COOH. Hence, trend in variation of magnetization with magnetic field and temperature opens its utility in spin-based electronic devices.