More recently, the silica gel can be doped by organic dyes with concentration of 10-5M via sol–gel processing. In view of the iso-electronic relation with SiO2, AlPO4 materials such as AlPO4-8 and AlPO4-5 are probably new latent hosts for laser dyes. So far, no work has been reported on the AlPO4 gel doped Rh6G. Rh6G is a popular laser dye applied frequently in probes and dyes lasers because of its high fluorescent yield and tunable property in visible (500–600 nm) range.

Researchers at Shanghai Institute of Optics and Fine Mechanics(SIOM/China) demonstrated the Rh6G molecule in the AlPO4 gels aggregates as H-dimers when the loading dyes molar ratio of Rh6G/Al(lact)3 is more than 1.0×10−4, and a further increasing of loading concentration gives rise to more serious aggregates as trimers and even multimers based on Exciton theory.[Materials Chemistry and Physics 125 (1-2), 87-92,2011]

Homogeneous monolith of AlPO4 gel doped with Rhodamine 6G (Rh6G) in different dye concentration is prepared by one step process with sol-gel method using the precursors Al(lact)(3) and H3PO4. The optical properties of AlPO4 gel doped with Rh6G have been characterized by UV-vis absorption spectra and fluorescence spectra. Rh6G molecular J-dimers and H-dimers even multimers are analyzed by excitation spectra based on Exciton theory. The structure of AlPO4 gel doped with Rh6G is investigated by 27Al and 31P Magic Angle Solid Nuclear Magnetic Resonance (MAS NMR), 27Al {31P } Rotational Echo Double Resonance (REDOR) NMR and 27Al Triple Quantum Magic Angle Spinning (TQ-MAS) NMR. Based on the results of optical spectra and the structural analysis by NMR techniques, The AlPO4 gel doped with Rh6G dye with molar ratio of Rh6G/Al(lact)3 of 1 x 10-4 displays excellent optical properties.