The phrasal verb “look up” consists of the verb “look” and the adverbial 'particle' “up.”
There is 'not a particle of' evidence to support their claim.
There is 'not a particle of' truth in what he said.
(..) - Tough little ship. - Little? Mr Worf, we could use some help at tactical. You do remember how to fire phasers? We're detecting chronometric particles. - They're creating a temporal vortex. - Time travel. - Data, report. - We're caught in a temporal wake. Captain... Earth. (..)1996 Star Trek: First Contact
(..) Number One, set a course for the Neutral Zone. - Bizet? - Berlioz. What do you have? We've finished our first sweep of the Neutral Zone. Fascinating. particles of dust per cubic metre. ultraviolet radiation spikes and a class-two comet. This is certainly worthy of our attention. (..)1996 Star Trek: First Contact