Titanylphthalocyanine takes various crystal polymorphism. The titanylphthalocyanine with Y-form shows excellent optical and photoelectric conversion. However, preparing the Y-form titanyl-phthalocyanine nanocrystals smaller than 200nm is difficult. Here, we prepared Y-form titanylphthalocyanine nanocrystals smaller than 100nm in a mixed solvent of phosphoric acid as a good solvent and a mixture of water and methyl ethyl ketone as a poor solvent. The size of the Y-form titanylphthalocyanine nanocrystals was controlled by changing the temperature of the poor solvent.
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