Phase transitions in two-dimensional colloidal particle system observed in Langmuir trough

Langmuir trough is applied as a platform to study the two-dimensional colloidal system. Polystyrene (PS) particles are distributed at decane/water interface in Langmuir trough. Digital video microscopy method is used to evaluate pair distribution function g(r) of the system by directly measuring particle locations in each frame of images. In addition, the phase of the system is determined by calculating its structure factor. A sequence of phase transitions of the system is observed by varying particle density at 20 °C.