Synthesis and magnetic properties of nanostructured metallic Co, Mn and Ni oxide materials obtained from solid-state metal-macromolecular complex precursors

Abstract

International audienceThe simple reaction of chitosan with metallic salts yields (chitosan) (MLn)(x), MLn = MnCl2, CoCl2, NiCl2, macromolecular complexes which, after a thermal treatment at 800 degrees C under air, give nanostructured Mn2O3, Co3O4 and NiO. The polymer acts as a template in the solid state, which is eliminated after the combustion process. At an intermediate stage, a layered graphitic carbon matrix was observed by HRTEM over the grown metal oxides. A mechanism for the growth of nanostructured oxides is discussed, including Raman studies. The nanostructured Mn2O3, Co3O4 and NiO particles grow over graphite layers and the solid-state role of chitosan is crucial for the formation of this graphite substrate. An antiferromagnetic transition was observed in Co3O4 nanoparticles, with T-N = 38 K, whereas NiO nanoparticles behave as a superparamagnetic material with a blocking temperature above 300 K

Incorporation of Nanostructured ReO3 in Silica Matrix and Their Activity Toward Photodegradation of Blue Methylene

“…If the preparation methods (all in solution) for ReO3 oxides are scarce [4][5][6][7][8][9], more limited are those for the oxides into SiO2, being the only one the core/shell ReO3/SiO2 structures reported by Ghosh et al [8]. In this work we propose the incorporation of ReO3 into sol-gel SiO2 by The broad peak around 2θ = 15°-25° observed in all these nanocomposites is typical of amorphous SiO2 as matrix in metal oxide nanostructured inside [10][11][12][13][14][15][16][17][18][19][20][21][22]. Unfortunately, the diffraction peaks of ReO3 are not clearly observed probably due to their small size, as it will be later confirmed by HR-TEM.…”

“…Here we report a general and suitable method for the preparation of Re metal oxides nanostructured materials [10][11][12]. Regarding to the possible application of these Re metal oxides, the first step is usually their incorporation in solid matrices.…”

Incorporation of Au and Ag Nanostructures Inside Sio2

“…The macromolecular complexes (PS-co-4-PVP)•(AuCl3)n and (Chitosan•(AuCl3)n prepared as previously described (see experimental part and ref. [22][23][24][25][26].and the SiO2 (prepared by sol-gel method see experiemental part and ref. 27,28) were mixture in solid state in a crucible and pyrolyzed under air at 800 °C.…”

“…In a typical synthesis [22][23][24][25][26] , the respective metallic salts AuCl3 and Ag(NO3) were added in a Schlenk tube using CH2Cl2 as solvent under magnetic stirring and then the respective Chitosan amount was added according to the 1:1 (1),(5) or 1:5 (2), (6) respectively for Au and Ag molar ratio (compound numeration according Table 1). Table 1.…”

“…Previously we have reported a versatile and reliable solid-state method to prepare metallic and metal oxides nanostructures materials [22][23][24][25][26] and their incorporation in SiO2 matrices 27,28 . The method consists in the pyrolysis of the macromolecular precursors (Chitosan)•(MLn)n•(SiO2)m and (PS-co-4-PVP)•(MLn)n•(SiO2)m where the precursors (Chitosan)•(MLn)m and (PS-co-4-PVP)•(MLn)m are generated according previous reports [22][23][24][25][26] .Now, we use this approach to prepare Au° and Ag° inside SiO2 to give Au/SiO2 and Ag/SiO2 composites founding that the dispersion of the metal noble nanoparticles into the silica matrix can be controlled by the 1:1 or 1:5 metal/polymer ratio, as well as, by the nature of the polymer. The results are compared with those previously obtained 27 for bimetallic composites Au/Ag//SiO2.…”