Photonic Crystal Fibers: A Platform for Raman Spectroscopy of Colloidal Nanoparticles in Solution

Substantial enhancement in Raman back scattering is obtained when the solution investigated is placed in the core of a hollow core photonic crystal fiber. The origin of this enhancement for liquid core waveguides is discussed. The enhancement is then used to study the Raman modes of several types of nanoparticles the Raman spectroscopy of colloidal nanoparticles in dilute solution. By employing this technique, four different stages of the synthesis ZnO nanoparticles were studied with record low pump power levels. The concentration of ZnO in the system was <1% by weight of the total mass. Also the different synthesis stages could be differentiated, and the differences between these stages could be identified through the Raman modes obtained. The concentration of nanoparticles in solution could be obtained with sensitivity for concentrations in the millimolar range. Raman modes of other nanoparticles such as CdTe have also been examined.