Water Dispersible Triplet–Triplet Annihilation Photon Up–Conversion Particle: Molecules Integrated in Hydrophobized Two–Dimensional Interlayer Space of Montmorillonite and Their Application for Photocatalysis in Aqueous Phase.

Green incident light (λ = ∼500 nm) is converted to blue light (λ = 400–450 nm) in air using bulky alkylammonium (DMDOA+), 9,10-diphenylanthracene (DPA), and Ru(dmb)32+ (dmb = 4,4′-dimethyl-2,2′-bipyridine) intercalated in a layered clay compound called “montmorillonite” [MMT–DMDOA+–DPA–Ru(dmb)32+]. The two-dimensional interstitial space has an interlayer spacing of a few nanometers. Emitter DPA is present in this interlayer spacing, having an intermolecular distance of approximately 3.0 nm at a high concentration. Sensitizer Ru(dmb)32+ is relatively dilute, having an intermolecular distance of 47 nm. The emission decay measurements and quantitative evaluation of the emission intensity demonstrate that blue light emission is induced by sequential processes, which consist of a triplet–triplet (T–T) energy transfer reaction from Ru(dmb)32+ to DPA and T–T annihilation of DPA molecules. From thermogravimetry and Fourier transform infrared spectra measurements, we observe that the cointercalated alkylammonium a...