Organic nanocrystals grown in sol-gel coatings

Well-defined organic crystals have been grown in inorganic gel coatings with particle sizes in the submicron range and narrow size distributions. The direct characterisation of these hybrid organic-inorganic films by optical confocal microscopy has allowed elucidation of the role of the main experimental parameters such as the nature of the gel precursors or solvents, the organic doping level and the rotation speed of the spin-coating apparatus. This is a one-step process in which nucleation and growth of the organic crystals occur simultaneously with the formation of the gel framework. Nanocrystallisation is optimised through the control of the coupling effect between the three elementary processes: nucleation, growth and matrix polymerisation. The validity and reproducibility of this simple and generic method have been demonstrated through the use of several organic molecules, solvents and silicon alkoxides.