Dielectric anomalous response of water at 60 degrees C

Recently, the paraelectric response of water was investigated in the range 0-100 degrees C. It showed an almost perfect Curie-Weiss behaviour up to 60 degrees C, but a slight change in slope of 1/epsilon(d) versus T at 60 degrees C was overlooked. In this work, we report optical extinction measurements on metallic (gold and silver) nanoparticles dispersed in water, annealed at various temperatures in the range from 20 to 90 degrees C. An anomalous response at 60 degrees C is clearly detectable, which we associate to a subtle structural transformation in the water molecules at that temperature. This water anomaly is also manifested by means of a blue shift in the longitudinal surface plasmon resonance of the metallic nanoparticles for the solutions annealed at temperatures higher than about 60 degrees C. A reanalysis of 1/epsilon(d) (T) for water in the whole temperature range leads us to conclude that the water molecule undergoes a subtle transformation from a low temperature (0-60 degrees C) configuration with a dipole moment mu(1)=2.18 D (close to the molecular dipole moment of ice) to a high temperature (60-100 degrees C) configuration with mu(2)=1.87 D (identical to the molecular dipole moment in water vapour).