Credit: Image courtesy of Wim Wenseleers, University of Antwerp
Water molecules (red and white balls) forming a chain in a carbon nanotube (blue lattice) normally orient randomly (yellow arrows; left, top and bottom). As the temperature decreases (right), emission color of an empty nanotube shows a gradual shift (empty data points) whereas a sudden shift in the emission color can be seen at 150 K in the nanotube filled with water (filled data points). This shift is attributed to an unexpected ferroelectric alignment of the water molecules confined within the nanotube (left, middle).