Sodium silicate particle size measurements using time-resolved fluorescence anisotropy

We present a development of the method for determining the particle sizes in sodium silicate liquors at high pH by using the measurement of time-resolved fluorescence anisotropy. Rather than the previous approach of using a single dye label, we demonstrate the use and advantages of using two fluorescent labels. Rotational times of the non-binding rhodamine B and electrostatically binding rhodamine 6G are used to independently determine the medium microviscosity and the silicate particle radius, respectively. The anisotropy measurements were performed on the range of samples prepared by diluting the stock solution of silicate to the concentrations ranging between 0.2M and 2M of NaOH and on the stock solution at different temperatures. The recovered average particle size has an upper limit of 7.0±1.2Å.