Vegetable assisted synthesis of gold nanostructures and its nonlinear optical properties

摘要

The Ecofriendly, cost-effective bio-synthesis of gold nanostructures (Au NSs) were synthesized by using Daucus carota subsp. Sativusand Cucumis sativus extracts efficiently. The plasmonic peaks of Daucuscarota subsp. Sativus and Cucumis sativus extract synthesized Au NSs exhibited at λ_(max) = 554 nm and λ_(max) = 560 nm, owing to excite of surface plasmon vibrations of Au NSs. The formation of NSs is due to the ionization of phenolic groups of vegetable extract. These extracts act as to reduce and capping agents in the formation of nanostructures. Transmission electron microscope (TEM) images of Au NSs revealed that they are in spherical and triangle shapes. The spherical shape of Au NSs of average diameters is 51 nm and 53 nm respectively. The effect of NSs on the luminescence of Eu(TTFA)_3 complexes was investigated with 350 nm excitation. Luminescence quenching is observed for Eu~(3+) with different concentrations of Au NSs in an exponential fashion. In both cases, the electric-dipole and magnetic dipole transitions are quenched with an increase of Au NSs. The quenching is occurring owing to the re-absorption of NSs. Nonlinear optical studies of metal NSs are estimated with a Z-scan technique using 800 nm, 110 fs pulses at 1 kHz repetition rate. Au NSs exhibited reverse saturable absorption (RSA) due to excited state absorption (ESA) and third-order nonlinear absorption coefficients for both Au NSs are of the order of 10~(-10)cm~2/W. Au NSs can be used as luminescent probes and optical limiters.