Caffeine and taurine slow down water molecules

In this work we study the effect of caffeine and taurine on the mobility of water molecules at 298 K using femtosecond mid-infrared and dielectric relaxation spectroscopy. We observe both molecules to have a slowing down effect on the mobility of surrounding water molecules: a single caffeine molecule slows down ~9 water molecules, a single taurine molecule slows down ~4 water molecules. The reorientation time constant of these slow water molecules is 4–5 times longer than the reorientation time constant of 2.5 ps of water molecules in bulk liquid water.