Interface charge transfer in polypyrrole coated perovskite manganite magnetic nanoparticles

Abstract

Structure and magnetism of nanocrystalline and epitaxial (Mn,Zn,Fe)3O4 thin films J. Appl. Phys. 111, 07A337 (2012) Memory effects in superparamagnetic and nanocrystalline Fe50Ni50 alloy J. Appl. Phys. 111, 033919 (2012) Bulk nanocomposite using self-forming core/shell nanoparticles and its magnetic properties for high-frequency applications J. Appl. Phys. 111, 07A307 (2012) E-field tuning microwave frequency performance of Co2FeSi/lead zinc niobate-lead titanate magnetoelectric coupling composites J. Appl. Phys. 111, 07C705 (2012) Additional information on J. Appl. Phys. Different hybrid structures were obtained by coating magnetic nanoparticles of perovskite type manganite at optimal doping (La 0.67 Sr 0.33 MnO 3 ,LSMO) with different quantities of polypyrrole (PPy). The amorphous layer of polypyrrole surrounding the crystalline magnetic core was observed by high resolution transmission electron microscopy (HRTEM) and analyzed by using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) measurements in near edge structure (XANES) techniques. By analyzing the magnetic behavior of the samples one can observe that the surface modification of magnetic nanoparticles by PPy results in an increase in the saturation magnetization of the composites. The process is ascribed to paired electrons transferred from the delocalized p states of the PPy into the outer disordered layers of the manganite. The analysis of pre-edge peak of the Mn K-edge XANES spectra in the case of PPy coated LSMO nanoparticles indicates that the charge transfer between polymer and nanoparticles is (directed) going to missing or distorted oxygen positions, hence increasing the 3d electrons' mobility and orbital hybridization between the neighboring manganese ion. As a consequence, within the surface layers of LSMO nanoparticles, both energy bands disrupted the structure, and the double exchange process between Mn ions was reestablished determining the saturation magnetizations and pre-edge features increase, respectively.

A valence states approach for luminescence enhancement by low dopant concentration in Eu-doped ZnO nanoparticles

“…3d 5/2 and Zn 2p 3/2 to C 1s lines by the corresponding escape depths according to Ref. [54] by using the general formula given by Cumpson and Seah [55].This formula accounts for the mean molar mass, the mean electronic number, the density, and the kinetic energy corresponding for each of the analyzed peak positions. The calculated values of the escape depth corrections were 0.46, and 0.60-0.62 for Eu 2 O 3 and ZnO, respectively.…”

Synthesis and physical properties of electromagnetic polypyrrole composites via addition of magnetic crystals

“…The in situ polymerization process has been well accepted as a synthesis method for electromagnetic PPy composites. [9][10][11][12][13][14][15][16][17][18][19] Fig. 4 shows a schematic illustration of the in situ polymerization procedure for the synthesis of electromagnetic PPy composites.…”

“…Therefore, the M s of the PPy composites is generally lower than that of the magnetic additives due to the non-magnetic character of PPy. [9][10][11][12][13][14][15][16]18,19,21,[27][28][29]32,36,37,[45][46][47][61][62][63][64][65][74][75][76] On the other hand, Prasad et al 17 93 suggested that such an increase in the magnetization could be attributed to the crystallite grain Fig. 10 The dependence of the magnetism at room temperature of the PPy powders on the applied magnetic field.…”

“…Electromagnetic PPy composites possess applicative potential as microwave absorbing materials, [9][10][11][12][13][14][15][16][17][18][19][20] adsorption materials, [21][22][23][24][25] electrocatalytic reagents to biospecies, 26 and specialized contrast agents for 1 H magnetic resonance imaging; 27 they also have potential applications in magnetic-controlled switches, 28 the magnetic separation of genomic DNA, 29 cancer cell targeting, 30 chemical sensing of H 2 O 2 , 31 and biosensing. 32 As mentioned in section 3.3, magnetic PPy composites possess good microwave absorbing properties which is required for electromagnetic shielding materials.…”

“…[1][2][3][4][5][6][7][8] In the past two decades, electromagnetic PPy has become one of the most attractive research topics due to its various potential applications. Electromagnetic PPy composites possess applicative potential as microwave absorbing materials, [9][10][11][12][13][14][15][16][17][18][19][20] adsorption materials, [21][22][23][24][25] electrocatalytic reagents to biospecies, 26 and specialized contrast agents for 1 H magnetic resonance imaging; 27 they also have potential applications in magnetic-controlled switches, 28 the magnetic separation of genomic DNA, 29 cancer cell targeting, 30 chemical sensing of H 2 O 2 , 31 and as biosensors. 32 Intrinsic magnetic PPy may be obtained via the control of the molecular structure during the synthesis of conducting PPy; also, electromagnetic PPy can be obtained via the incorporation of external magnetic crystals.…”