*2.2. Soot Deposition System*

The soot deposition system was described in detail in the previous report [28]. Briefly, the diesel soot was generated with a Webasto diesel engine preheater (Webasto group, Stockdorf, Germany) from diesel fuel and air. The samples were placed on the heating plate and exposed to exhaust gases for 1.5 min. The amount of deposited soot was measured by weighing the samples.
