The fluorescence of a standard dye Rhodamine 6G (R6G) in solution decreases on addition of reduced graphene oxide (rGO). The absorption spectra and lifetime measurements confirm that no excited-state but a ground-state complex formation is responsible for this effect. For silver decorated rGO (Ag-rGO), the quenching efficiency and ground state complex formation process is small. Z-scan measurements have been done to study the optical nonlinearity at 532 nm under ps time scale. Remarkable reduction in the saturable absorption (SA) effect of R6G indicates no nonlinear contribution from the ground state complex. The results have been explained with varying charge transfer rates and non-fluorescence nature of the complex. © 2014 AIP Publishing LLC.

Prem Ballabh Bisht

Department Of Physics

Sudhakara Reddy Bongu

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Charge Transfer in Graphene Oxide-Dye System for Photonic Applications

AIP Conference Proceedings

The nonlinear optical properties of silver-nanoparticle-decorated functionalized (hydrogen-induced reduction, exfoliated) multilayered graphene (AgNP/fG) composite have been investigated in the picosecond time scale by using the Z-scan technique. Drastic changes in the Z-scan profiles are obtained in AgNP/fG at 1064 nm as the profile flips from the behavior of strong saturable absorption (SA) to reverse saturable absorption (RSA) on increasing the incident intensity. On the other hand, in graphene, the effect of weaker SA is observed at low intensities, but it flips to RSA at higher incident intensities. The strong SA in the case of the composite has been attributed to the electronic interaction between graphene and silver nanoparticles. The metallic plasmonic transition has a contribution to the optical nonlinearity in AgNP/fG at 532 nm. © 2012 Optical Society of America.

Journal of the Optical Society of America B: Optical Physics

Optical nonlinearity of silver-decorated graphene

The absorbance and the fluorescence intensity of dye have been found to decrease on increasing the concentration of either (i) functionalized hydrogen-induced exfoliated multilayer graphene (f-HEG) or (ii) silver nanoparticles (AgNP). The observed static-quenching is due to the weak interaction between the dye and the AgNP or f-HEG in the ground state. In contrast, the spectra of the dye are unaffected by the presence of AgNP-decorated graphene. Pre-existing charge transfer interaction between the metal nanoparticles and graphene has been proposed to be mechanism responsible for this behavior. © 2011 Elsevier B.V. All rights reserved.

Chemical Physics Letters

Restricting charge transfer in dye-graphene system

Fluorescence spectra of two organic dyes doped in polymer beads as well as coated on single microparticles of silica exhibit whispering gallery modes (WGMs). For doped microspheres, theoretical simulations on WGMs have been carried out based on the Lorentz-Mie theory by varying the refractive index and the diameter of the microparticle. Similarly, for a coated microsphere, an Aden and Kerker model of the Lorentz-Mie theory has been used to simulate WGMs. For diameters ≥8 μm, low-resolution simulations of scattering efficiency fail to show modes of higher-quality factors (Q - 108). A new procedure of identifying these modes is given here that does not require use of high-performance computing. Effects of WGMs on decay rates have also been studied. It has been found that, while doped microparticles exhibit no effect on the radiative rate, coated microparticles show inhibition of the decay rate for smaller sizes. Decay rates of single-coated microspheres are found to be distinctly different from those of randomly shaped single microcrystals. © 2009 Optical Society of America.

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Publisher	Data powered by TypesetAmerican Institute of Physics Inc.
Open Access	No