Which of the following is an uncoupler?

The rate of the ATP-32P exchange reaction was reduced by thyroxine and this inhibition was doubled by adding the thyroxine to the incubation medium after the paicles rather than before.The increased inhibition of the exchange reaction was associated with a reduction in P/O ratios and a loss of the stimulatory effect of thyroxine on substrate oxidation.Ref: DM Vasudevan, 7th edition, page no: 265, 266