Quenching of fluorescence of aromatic molecules by graphene due to electron transfer

Investigations on the fluorescence quenching of graphene have been carried out with two organic donor molecules, pyrene butanaoic acid succinimidyl ester (PyBS, I) and oligo(p-phenylenevinylene) methyl ester (OPV-ester, II). Absorption and photoluminescence spectra of I and II recorded in mixture with increasing the concentrations of graphene showed no change in the former, but remarkable quenching of fluorescence. The property of graphene to quench fluorescence of these aromatic molecules is shown to be associated with photo-induced electron transfer, on the basis of fluorescence decay and time-resolved transient absorption spectroscopic measurements.Comment: 18 pages, 6 figure

Synthesis, Characterization and Biological Activities of a New 5-Chloroisatin Schiff Base and its Metal Complexes

Copper(II), cobalt(II), nickel(II) and zinc(II) complexes of 5-chloroisatin Schiff base (L) (L= Schiff base derived from 5-chloroisatin and 2-methyl-4- nitro aniline) were synthesized and characterized. The authenticity of the ligand and its metal complexes had been established by micro analysis, IR, NMR, LC/MS, UV-Vis and electrical conductance measurements. The ligand acts as a bidentate in which the carbonyl oxygen and the azomethine nitrogen of 5-chloroisatin are involved in co-ordination. Square planar geometry was proposed for Cu(II) and Ni(II) complexes and tetrahedral geometry was proposed for Co(II) and Zn(II) complexes. The ligand and its metal complexes have been screened for their antibacterial activity against bacterias viz. Staphylococcus aureus and Escherichia coli etc. and antifungal activity against fungi Aspergillus niger and Aspergillus flavous etc. The activities of both the samples have shown significant and noticeable changes on complexations

Imaging the Near Field

In an earlier paper we introduced the concept of the perfect lens which focuses both near and far electromagnetic fields, hence attaining perfect resolution. Here we consider refinements of the original prescription designed to overcome the limitations of imperfect materials. In particular we show that a multi-layer stack of positive and negative refractive media is less sensitive to imperfections. It has the novel property of behaving like a fibre-optic bundle but one that acts on the near field, not just the radiative component. The effects of retardation are included and minimized by making the slabs thinner. Absorption then dominates image resolution in the near-field. The deleterious effects of absorption in the metal are reduced for thinner layers.Comment: RevTeX, (9 pages, 8 figures

Novel magnetic properties of graphene: Presence of both ferromagnetic and antiferromagnetic features and other aspects

Investigations of the magnetic properties of graphenes prepared by different methods reveal that dominant ferromagnetic interactions coexist along with antiferromagnetic interactions in all the samples. Thus, all the graphene samples exhibit room-temperature magnetic hysteresis. The magnetic properties depend on the number of layers and the sample area, small values of both favoring larger magnetization. Molecular charge-transfer affects the magnetic properties of graphene, interaction with a donor molecule such as tetrathiafulvalene having greater effect than an electron-withdrawing molecule such as tetracyanoethyleneComment: 16 pges, 5 figure

Testudines of India: A Review on Diversity, Threats and Conservation Initiatives

The present review is a collection of the available literature resources related to Testudines of India. Different aspects of diversity studies pertaining to turtles in India is presented in this review along with threats and conservation initiatives in different parts of India in different timeline