In-situ Raman scattering in nanomaterial flame synthesis: A case on TiO_2 nanoparticle

摘要

Non-intrusive, in-situ spatially and temporally precise Raman spectroscopy technique is employed to diagnose the gas-phase synthesis of nanostructured materials. We demonstrate spontaneous Raman scattering (SRS) measurements with high precision during the transition of gas-phase molecules to structured nanomaterials in strategically chosen flame-based flow fields. Vibrational Stokes Q-branch Raman signals of major and minor species in the gas phase reaction are collected from a volume as small as 10~(-12) m~3. Temperature profile is determined by least-squared fitting the measured spectrum for N_2 to a theoretical spectra library at different temperatures. The measurements are confirmed and combined with computational reaction fluid simulations to discover the complex mechanism behind the chemical and physical transitions. We also test in-situ laser characterization of the nanomaterial growth by monitoring the Raman signature spectrum of interested solid particles. We finally show the potentials of Raman scattering to combine with other characterization techniques as a powerful tool to study the complicated two-phase related flame synthesis process.