Raman Spectroscopy of Nanoparticles Using Hollow-Core Photonic Crystal Fibers

Hollow-core photonic crystal fibers (HC-PCF) were employed for enhancing the Raman signal obtained from ZnO nanoparticles (NPs) in solution. By selectively filling the core of HC-PCF, substantial enhancement in the Raman signal was obtained. By employing this technique, four different stages in the synthesis ZnO NPs were studied with record low pump power levels. The concentration of ZnO NPs in the system was <1% by weight of the total mass. Yet, the different synthesis stages could be differentiated and identified through the Raman modes obtained. It was also demonstrated that the concentration of NPs in solution could be obtained with sensitivity in the millimolar range. This could be achieved by examining the amplitude ratios of the relevant Raman modes.