Influence of the cationic groups of substrate surfaces on the melting behavior of electrostatic interactional colloidal crystals grown via heterogeneous nucleation

The effect of the substrate surface groups on the thermal stability of colloidal crystals formed via heterogeneous nucleation was investigated by observing the melting behavior of the colloidal crystals on three types of substrate: one charged negatively by silanol groups, one with introduced amino groups, and one with introduced quaternary ammonium groups. The degree of particle binding by the substrate in the colloidal dispersion was evaluated in terms of the particle arrangement formed through a dry deposition process that involved drying the dispersion on each substrate. The particle mobility on the substrates was higher in the order of the negatively charged substrate, the substrate with introduced amino groups, and the substrate with introduced quaternary ammonium groups. The melting temperature was measured in terms of the colloidal crystals formed on each substrate and was found to be 40.5 degrees C on the negatively charged substrate, 46.0 degrees C on the substrate with introduced amino groups, and 52.4 degrees C on the substrate with introduced quaternary ammonium groups. The increase in melting temperature was derived from the decrease in the particle mobility on the substrates with introduced positively charging groups, which resulted in an increase in the thermal stability of the colloidal crystalline lattice in relation to the Brownian motion due to the reduction in the particle mobility through the interaction between the negatively charged particles and the substrates.