Optical characterization of Coumarin 334 hybrid with silver nanoparticles in imidazolium-based ionic liquid

Abstract

Fluorescence enhancement of laser dye Coumarin334 (Cu334) hybrid with silver (Ag) nanoparticles in 1-ethyl-3-methylimidazolium ethylsulfate [EMIM EtSO4] and methanol as reference has been reported. The molar concentration of the prepared silver was C= (2.07 × 10−9 mol/L). Spectroscopic studies showed that, the increasing of metal nanoparticles (M-NPs) content resulting in gradual increasing then diminishing of fluorescence of Cu334 with slight red shift. The influence of surface plasmon resonance (SPR) phenomena of Ag NPs, exposure to blue laser radiation, on the photo-physical and optical parameters of Cu334 dye and its respective complex (i.e. profile of absorption & fluorescence spectral, magnitude of stokes shifts, transition dipole moment and lifetime) were evaluated in this paper. Quenching of Cu334 fluorescence with NPs in IL is mainly observed which may be attributed to electrostatic multi-layers formation of cations and anions around NPs resulting in loss of optical properties of Ag NPs. Under transverse pumping of coumarin334 by blue diode laser (450 nm) of (250 mW), the initial ASE for Cu334 dissolved in EMIM EtSO4 without Ag NPs was diminished to about 13% as time progressed to 180 min, while with Ag NPs the initial ASE was reduced to almost 9% as time progressed to 120 min. This instability of complex samples compared with dye itself may attribute to induce a CW laser wave that causes the changing of nanoparticles structural due to exposure for high laser pumping with very intense heating resulting in losing of shape, size and optical properties of NPs.