Avogadro is a scientist that was kidnapped by Dimitri Allen to work in his lab. He is the most knowledgeable of the three scientists that were kidnapped.
Avogadro is very smartly dressed and sensitive about his height.
Avogadro is the scientist which makes Professor Layton have a realisation about the laboratory's real location. Professor Layton picked up on the fact that Avogadro's footprints were wet, hence making his realise that the laboratory must be near the river.
Avogadro appears in several quests, he even has his own quest called Avogadro Squared!.
Throughout the plot of Professor Layton and the Unwound Future, Avogadro gives no puzzles.
"Avogadro is a scientist who works in Dimitri's labs. He is impatient and quick tempered but is the most knowledgeable of all the scientists. He is very sensitive about his height."