University of Madras

About: University of Madras is a education organization based out in Chennai, Tamil Nadu, India. It is known for research contribution in the topics: Ring (chemistry) & Lipid peroxidation. The organization has 8496 authors who have published 11369 publications receiving 211152 citations. The organization is also known as: Madras University & University of Chennai.

Compliments of confinements: substitution and dimension induced magnetic origin and band-bending mediated photocatalytic enhancements in Bi1−xDyxFeO3 particulate and fiber nanostructures

Abstract: The manifestation of substitution and dimension induced modifications in the magnetic origin and photocatalytic properties of Dy substituted bismuth ferrite (BDFOx) particulate and fiber nanostructures are reported herein. A gradual transformation from rhombohedral to orthorhombic structure is observed in BFO with the increasing concentration of Dy. Substitution induced size reduction in particulate and fiber nanostructures is evident from the scanning and transmission electron micrographs. Energy band structures of both particulate and fiber nanostructures are considerably influenced by the Dy substitution, which is ascribed to the formation of new energy states underneath the conduction band of host BFO. Field dependent and temperature dependent magnetic studies reveal that the origin of magnetism in pure BFO systems is due to the antiferromagnetic-core/ferromagnetic-shell like structure. On the other hand, it gets completely switched into ‘canted’ spin structures due to the substitution induced suppression of cycloidal spins in BFO, which is found to be the origin of magnetism in BDFOx particulate and fiber nanostructures. The visible light driven photocatalytic activity of BDFOx nanostructures is found to be enhanced with increasing concentration of Dy. Substitution induced band gap modification, semiconductor band bending phenomenon mediated charge transfer and reduced recombination resistances are attributed to the observed photocatalytic enhancements in these nanostructures.

Rare Earth Elements in Limestones of Kallankurichchi Formation of Ariyalur Group, Tiruchirapalli Cretaceous, Tamil Nadu

Abstract: Studies on calcium carbonate (CaCO 3 ), trace elements and rare earth elements were carried out on the Kallankurichchi Formation in order to understand the elemental behaviour in marine limestones of the Tiruchirapalli Cretaceous. Variation in EREE content between Sandy Fossiliferous Limestone (SFL) and Fossiliferous Limestone (FL) can be explained as due to the varying amounts of terrigenous material present in the limestones. PAAS (Post Archaean Australian Shale) normalised REE patterns and La N /Yb N ((La Sample /La Shale )/(Yb Sample /Yb Shale )) ratios suggest that the terrestrial rocks are the major source for REE in these limestones. The SFL and FL show negative Ce anomalies, with slight variation between these limestones. The negative correlation between CaCO 3 and Ce/Ce* values indicates that the observed Ce anomalies are not related to the CaCO 3 content in SFL and FL, whereas Ce/Ce* values show positive correlation with detrital elements implying that the observed variations in the Ce anomalies resulted from the variation in the terrigenous material supplied by the continental area. SFL and FL show low U/Th ratio and U content. Low U contents suggest that the oxic condition prevailed in the bottom water and sediment column during the deposition of Kallankurichchi Formation.