Excitation energy transfer from dye molecules to doped graphene

Recently, we have reported theoretical studies (J. Chem. Phys. 129, 054703, 2008 and J. Chem. Phys. 130, 086101, 2009) on the rate of energy transfer from an electronically excited molecule to graphene. It was found that graphene is a very efficient quencher of the electronically excited states and that the rate $\propto$ $(distance)^{-4}$. The process was found to be effective up to $30\;nm$ which is well beyond the traditional FRET limit. In this report, we study the transfer of an amount of energy $\hbar \Omega$ from a dye molecule to doped graphene. We find a crossover of the distance dependence of the rate from $(distance)^{-4}$ to exponential as the Fermi level is increasingly shifted into the conduction band, with the crossover occurring at a shift of the Fermi level by an amount $\hbar \Omega/2$.Comment: This paper was submitted to J. Chem. Phys. on 20/05/201

PHYTOCHEMICAL SCREENING AND TLC STUDIES OF MORINGAOLEIFERA EXTRACT: THEIR ANTIBACTERIAL AND ANTI-OXIDANT ACTIVITIES

Objective: India being a rich and varied flora of medicinal plants since the Vedic period. The present study deals with the phytochemical screening and thin-layer chromatographic studies of Moringa Olifera leaf extract belonging to family Moringaceae. Methods: Phytochemical screening determination by some chemical tests and thin layer chromatographic study was carried out by using various solvent system of varying polarity of hexane, chloroform, ethyl acetate, acetone and methanol extracts. Results: Phytochemical screening reflects the presence of alkaloids, glycosides, saponins, phenolic compounds, tannins, phytosterols, carbohydrates, proteins, amino acids, flavonoids, quinones and terpenoids shows different types of results in different solvents extracts. Thin layer chromatographic studies of the Moring olifera root extracts constituted different colored phytochemical compounds with different Rf values The result obtained from DPPH Assay, ABTS assay also confirmed MoringaOlifera as a rich source of natural antioxidants, and Anti-bacterial activity studies revealed that it exerted maximum effect against the few pathogenic and non-pathogenic bacterial strain. Conclusion: Thus it provides evidence that solvent extract of Moringa Olifera contains medicinally important bioactive compounds and this justifies the use of plant species as a traditional medicine for treatment of various diseases