RESUMO
In this work, a new porphyrin, 5,10,15,20-tetrakis{4-[((4-methoxyphenyl)acetyl)oxy]phenyl}porphyrin (H2TMAPP) (1), and its cobalt complex [CoII(TMAPP)] (2) were synthesized in good and quantitative yields, respectively. The chemical structures of these synthesized compounds were confirmed by FT-IR, 1H NMR, MS, UV-visible, and fluorescence spectroscopy. Their photophysical properties, namely their molar extinction coefficients (∑), fluorescence quantum yields (Φ f) and lifetimes (τ f), were determined and compared with those of meso-tetraphenylporphyrin. Furthermore, their electrochemical behaviours were examined using cyclic voltammetry (CV). Dielectric properties such as the conductivity (σ) and the real (M') and imaginary (M'') parts of the dielectric modulus were investigated as a function of temperature and frequency. The impedance analysis was carried out using Cole-Cole plots to elucidate the electrical conduction mechanism. The catalytic power and the adsorption properties of the prepared compounds were studied for methylene blue (MB) and crystal violet (CV) degradation. The results reveal that the studied compound [CoII(TMAPP)] can be used as a catalyst for the decolourisation of dyes in the presence of H2O2.
RESUMO
In this study, we report the effects of Ti on the critical behavior of La0.67Ba0.25Ca0.08MnO3 samples prepared by the flux method. Moreover, the critical exponents ß, γ and δ are estimated through numerous techniques such as the modified Arrott plot, the Kouvel-Fisher method and critical isotherm analysis of the magnetic measurements on record near the Curie temperature. Compared to standard models, the estimated critical exponents are close to the theoretical values of the mean-field model for these samples. In order to estimate the spontaneous magnetization at a given temperature, we used a process based on the analysis, in the mean-field theory, of the magnetic entropy change (-ΔS M) vs. magnetization (M). An excellent agreement was found between the spontaneous magnetization determined from -ΔS M vs. M 2 and the classical extrapolation from the Arrott curves (µ 0 H/M vs. M 2), thus confirming that -ΔS M is a valid approach to estimate the spontaneous magnetization in this system. The accuracy of the critical exponent values was confirmed with the scaling hypothesis. The magnetization curves fall onto one of two sides, below and above T C.
RESUMO
The influence of Ti4+ ions incorporated into the B site on the structural, vibrational and optical properties of La0.67Ba0.25Ca0.08Mn(1-x)Ti x O3 (LBCM(1-x)T x ), a polycrystalline compound prepared by a molten salt method, was discussed. The X-ray diffraction (XRD) studies confirmed that at room temperature these compounds crystallize in the rhombohedral phases of R3Ìc. Rietveld refinement indicated that the octahedron (Mn/Ti)O6 underwent a slight deformation and the θ (Mn/Ti)-O-(Mn/Ti) bond angles decreased with the increase in the Ti content. Furthermore, Raman spectra were recorded at room temperature for the LBCM(1-x)T x ceramics to investigate the influence of incorporated Ti4+ ions in LBCM(1-x)T x . Moreover, we controlled the frequency and damping of the optic modes based on Ti incorporation. The infrared (IR) absorption spectrum (FTIR) analysis in the span of 420-750 cm-1 supports the XRD results. The diffuse reflectance data at room temperature verified that both transition levels (5Eg â 5T5g) and (4A2g â 4T2g) correspond to the Mn3+ and Mn4+ ions. The optical band gap (E g) values decreased from 2.90 eV to 2.70 eV with the increase in the Ti4+ content, implying that our samples could be good candidates for some applications in luminescent devices, such as ultrafast optoelectronic devices. Moreover, the photoluminescence spectra (PL) features at room temperature decreased for all samples. CIE were estimated for all the concentrations of Ti4+ ions. The results indicated that are a shifts in the CIE values of the compounds.
