Inorganic small particle formation by photochemical reaction in lyotropic liquid crystals

Abstract

Inorganic small particles were obtained by photochemical reaction of Fe(NO₃)₃ and oxalic acid in aqueous solution, anionic AOT-water and cationic CTAB-hexanol-water liquid crystals, respectively. X-ray diffraction and IR spectra identified that the products obtained from these different systems have the same composition, β-FeC₂O₄. 2H₂O, but have different shape and size of particles: rodlike for aqueous solution and needlike for liquid crystals. The size of the particles formed in the three systems followed the sequence: D(water)>D(CTAB-hexanol-water )>D(AOT-water). Varying the intensity of the incident light changed the growth rate of particles and affected the final particle size. The growth rate of the particles was enhanced by increasing the incident light intensity, but the largest average diameters were achieved with decreasing light intensity. This inverse relationship between final size and incident light intensity can be shown by comparing the average diameters of the particles formed in AOT liquid crystal under different conditions: D(weak light), D(moderate light) > D(strong light).