suspicious of/about
what is the preposition after suspicious?

For example, in this sentence:

I'm suspicious of/about his behavior. I think he is up to something.

Question

suspicious of/about
what is the preposition after suspicious?

For example, in this sentence:

I'm suspicious of/about his behavior. I think he is up to something.

Answer

There's a subtle difference that you can use either one and use them interchangeably.
The difference:
 Use 'Suspicious Of' when you just think that not in detail. But, use 'Suspicious About' when you think but in detail. (More detailed than 'suspicious of') 
and I think that 'Suspicious Of' is used for people, while 'Suspicious About' is used for something (Not people, but their behavior, habit etc.).

Answer

Either is fine.

Evden çıkmadan dil öğrenme fırsatını kaçırmayın. Deneyimli dil eğitmenlerimizden oluşan seçkimize göz atın ve ilk dersinize şimdi kaydolun!