Silent-enhancement of multiple Raman modes via tuning optical properties of graphene nanostructures

Raman scattering signal can be enhanced through localization of incident field into sub-wavelength hot-spots through plasmonic nano-structures (Surface-enhanced Raman scattering-SERS). Recently, further enhancement of SERS signal via quantum objects are proposed by [1] without increasing the hot-spot intensity (\textit{silent-enhancement}) where this suggestion prevents the modification of vibrational modes or the breakdown of molecules. The method utilizes path interference in the non-linear response of Stokes-shifted Raman modes. In this work, we extend this phenomenon to tune the spectral position of \textit{silent-enhancement} factor where the multiple vibrational modes can be detected with a better signal-to-noise ratio, simultaneously. This can be achieved in two different schemes by employing either (i) graphene structures with quantum emitters or (ii) replacing quantum emitters with graphene spherical nano-shell in \cite{Postaci2018}. In addition, the latter system is exactly solvable in the steady-state. These suggestions not only preserve conventional non-linear Raman processes but also provide flexibility to enhance (silently) multiple vibrational Raman modes due to the tunable optical properties of graphene

Green Synthesis and the formation kinetics of silver nanoparticles in aqueous Inula Viscosa extract

In this study, we present the production of silver nanoparticles in aqueous Inula Viscosa extract by the green synthesis approach at room temperature. The structural, morphological properties as well as formation kinetics of the synthesized silver nanoparticles were characterized by UV-VIS, STEM, XRD, Raman and FTIR measurements. Mono-dispersed and very stable silver nanoparticles with size of 15$\pm$5 nm and face-centered cubic crystal structure were synthesized in aqueous Inula Viscosa extract. The kinetic studies of silver nanoparticles formation in Inula Viscosa extract show that silver nanoparticle formation reaction reached the equilibrium within 24 h and fit in the first-order reaction kinetics. The results clearly show that the size of fabricated nanoparticles is independent on the dynamical formation process since the reaction time and initial silver ion concentration did not affect on size and morphology of the produced particles