Four spinel ferrite compositions of the CuAl(x)Fe(2-x)O4, x = 0.0, 0.2, 0.4, 0.6, system prepared by usual double-sintering ceramic route and quenched (rapid thermal cooling) from final sintering temperature (1373 K) to liquid nitrogen temperature (80 K) were investigated by employing X-ray powder diffractometry, (57)Fe Mossbauer spectroscopy, and micro-Raman spectroscopy at 300 K. The Raman spectra collected in the wavenumber range of 100-1000 cm(-1) were analyzed in a systematic manner and showed five predicted modes for the spinel structure and splitting of A1g Raman mode into two/three energy values, attributed to peaks belonging to each ion (Cu(2+), Fe(3+), and Al(3+)) in the tetrahedral positions. The suppression of lower-frequency peaks was explained on the basis of weakening in magnetic coupling and reduction in ferrimagnetic behavior as well as increase in stress induced by square bond formation on Al(3+) substitution. The enhancement in intensity, random variation of line width, and blue shift for highest frequency peak corresponding to A1g mode were observed. The ferric ion (Fe(3+)) concentration for different compositions determined from Raman spectral analysis agrees well with that deduced by means of X-ray diffraction line-intensity calculations and Mossbauer spectral analysis. An attempt was made to determine elastic and thermodynamic properties from Raman spectral analysis and elastic constants from cation distribution.

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a b s t r a c tObjective: The objective of present work was to prepare a polyelectrolyte complex (PEC) between chitosan (polycation) & pectin (polyanion) and to develop enteric coated tablets for colon delivery using the PEC. Methodology: The PECs were prepared using different concentrations of chitosan and pectin. Drug loaded enteric coated tablets were prepared by wet granulation method using PEC to sustain the release at colon and coating was done with Eudragit S 100 to prevent the early release of the drug in stomach and intestine. Two independent variable, % PEC (chitosan/pectin) and % coating were optimized by 3 2 full factorial design. Statistical model were also used to supplement the optimization. DSC was performed to confirm the interaction between the polyions. Developed formulations were evaluated for physical appearance, weight variation, thickness, hardness, friability, % swelling, assay, in-vitro and ex-vivo drug release studies to investigate the PEC's ability to deliver the drug to colon. Ex-vivo release study using rat caecal content was also carried out on optimized formulation. Results and discussion: DSC results confirmed chitosan/pectin interaction and subsequent formation of PEC. The optimized formulation containing 1.1% of PEC and 3% of coating showed highest swelling and release in alkaline pH mechanism of which was found to be microbial enzyme dependent degradation established by ex-vivo study using rat caecal content.

This communication presents a detailed study on a Fe modified CaCuTiO cubic perovskite system (CaCuTiFeO with x = 0.0-0.7) by performing X-ray powder diffractometry, DC SQUID magnetization and Fe Mössbauer spectroscopy. The first ever Mössbauer studies on the system supported the reported peculiarity of the structure. Mössbauer analysis for the compositions x = 0.1, 0.3, and 0.5 suggest Fe ions in two different environments. The site with larger quadrupole splitting corresponds to Fe in the octahedral symmetry, while the site with lower chemical shift and quadrupole splitting belongs to Fe in the square-planar (A'-) configuration. With the increase in Fe-substitution, Fe appears to prefer A'- symmetry. Antiferromagnetic features are retained up to x = 0.3, but weak ferromagnetic characteristics appear with higher Fe substitution. The switching of antiferromagnetic to ferromagnetic behavior was related to the preferential occupation of Fe in square-planar symmetry accommodating Cu.

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First ever intriguing reversible mechanochromism espied in and chromaticity study on polycrystalline CaCu3Ti4O12 composition milled up to 16 hours are reported. The composition changes its color from blackish‐brown (un‐milled sample)‐reddish‐brown (1 hours milled sample)‐ heina‐green (6 hours milled sample)‐spinach‐green (16 hours milled sample) mainly due to the phase separation and corresponding change in band‐gap energy on milling. The UV‐Vis spectra show three observable absorption edges correspond to dx2-y2↔ditalicxy, dx2-y2↔dz2, and dx2-y2↔ditaliczx, dyz transitions. A marked mechanochromic effect with crystallite size reduction is explained in the light of the difference in the site group symmetry of CuO4 and ligand‐metal charge transfer coupled with Cu2+ d‐d transitions. The observed mechanochromism is reflected and well supported by photoluminescence spectral analysis. CIE chromaticity coordinates are located in the light blue region for an un‐milled sample and violet color region for 6 hours milled sample. The profound correlation between the structural and optical properties has been revealed.