Raman spectroscopy of diesel and gasoline engine-out soot using different laser power

Haiwen Ge, Zhipeng Ye, Rui He

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


We studied engine-out soot samples collected from a heavy-duty direct-injection diesel engine and port-fuel injection gasoline spark-ignition engine. The two types of soot samples were characterized using Raman spectroscopy with different laser powers. A Matlab program using least-square-method with trust-region-reflective algorithm was developed for curve fitting. A DOE (design of experiments) method was used to avoid local convergence. The method was used for two-band fitting and three-band fitting. The fitting results were used to determine the intensity ratio of D (for “Defect” or “Disorder”) and G (for “Graphite”) Raman bands. It is found that high laser power may cause oxidation of soot sample, which gives higher D/G intensity ratio. Diesel soot has consistently higher amorphous/graphitic carbon ratio, and thus higher oxidation reactivity, compared to gasoline soot, which is reflected by the higher D/G intensity ratio in Raman spectra measured under the same laser power.

Original languageEnglish
Pages (from-to)74-80
Number of pages7
JournalJournal of Environmental Sciences (China)
StatePublished - May 2019


  • Diesel engine
  • Gasoline engine
  • Particulate matter
  • Raman spectroscopy
  • Soot emission


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