What does "di" do here?

Although in this case it is :qualcosa di"you'll find the answer below. http://italian.about.com/library/fare/blfare157a.htm

1. The preposition di is used with certain verbs and adjectives:

Accorgersi di qualcosa (to notice something) Innamorarsi di qualcuno (to be in love with someone) Malato di una malattia (ill with a sickness) Vergognarsi di qualcosa (to be ashamed by something)