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We studied engine-out soot samples collected from a heavy-duty direct-injection diesel engine and a port-fuel injection gasoline spark-ignition engine. The two types of soot samples were characterized using Raman spectroscopy with different laser power. A Matlab program using least-square-method with trust-region-reflective algorithm was developed for curve fitting. We used a DOE (design of experiments) method to avoid local convergence. This method was used for two-band fitting and three-band fitting. The fitting results were used to determine the intensity ratio of D and G Raman bands. We find that high laser power may cause oxidation of soot samples, which gives higher D/G intensity ratio. Diesel soot has consistently higher amorphous/graphitic carbon ratio and thus higher oxidation reactivity, in comparison to gasoline soot, which is revealed by the higher D/G intensity ratio in Raman spectra measured under the same laser power.
Soot is an important material with impacts that depend on particle morphology. Transmission electron microscopy (TEM) represents one of the most direct routes to qualitatively assess particle characteristics. However, producing quantitative informati
Low dimensional systems, nanowires, in particular, have exhibited excellent optical and electronic properties. Understanding the thermal properties in semiconductor nanowires is very important for their applications in their electronic devices. In th
Here we design, construct, and characterize a compact Raman-spectroscopy-based sensor that measures the concentration of a water-methanol mixture. The sensor measures the concentration with an accuracy of 0.5% and a precision of 0.2% with a 1 second
We propose a novel femtosecond stimulated Raman spectroscopy (FSRS) technique that combines entangled photons with interference detection to select matter pathways and enhance the resolution. Following photo excitation by an actinic pump, the measure
Non-intrusive detection systems have the potential to characterise materials through various transparent glass and plastic containers. Food and drink adulteration is increasingly problematic, representing a serious health risk as well as an economic