Preparation And Spectra Characterization Of Alkyl Perylene Diimide/Porous SiO₂ Compsite

N,N-dodecyl Perylene diimide derivates(DDPDI) are plannerÏ€-conjugated molecular with relatively high fluorescence quantum yields in monomer state.In solid state or even dense solution,it would be strongly quenched due to the strongÏ€-Ï€aggregation,which was a great disadvantage in applications of light emitting materials where the high fluorescence quantum yields were desired.Poropus SiO₂ materials, owing to their lager surface areas and porous volumes,are one of the most promising hosts for incorporating N,N-dodecyl perylene diimide into the pores to obtain DDPDI monomer in solid state,which would have potential application in light-emitting materials.The spectra of DDPDI located in the porous,however,will boarden or shfit due to the effect of the inorganic framework of porous SiO₂,which generates a considerable difficulty to characterize these monomers in such complex surface.In this paper,DDPDI molecules were incorporated into the porous SiO₂,namely,MCM-41 and sepiolite fiber.The structures were characterized by X-ray diffraction,transmition electron microscopy, scanning electron microscopy,N₂-absorption-desorption technique etc. DDPDI monomer and aggregates were distinguished by UV-vis absorption and fluorescence spectroscopy.The concentration-dependent UV-vis and fluorescence spectra of the DDPDI in toluene at room temperature were studied.The relative intensities of 0-1 and 0-0 transition within the electronic transition procession were carried out to ditinguish monomer and aggregative state of DDPDI.In monomer state,the relative intensity of 0-1 and 0-0,which sharply increased upon aggregates formation,is determined as 0.670. Based on the equal K model,nonlinear least-square regression analysis of the UV-vis spectral.data shows that the value of the equilibrium constent K is 4.45×10⁴L/mol.The average numbers of aggregated DDPDI at different concentrations were calculated as well.N,N-dodecyl perylene diimide/MCM-41 compsite were prepared by liquid adsorption.Both the monomers and aggregates were characterized by UV-vis absorption spectroscopy.Strongly fluorescence at the wavelength of 536nm has been observed with DDPDI content lower than 5.0mg/g where the DDPDI molecules were in monomer state.With the content up to 10.0mg/g,DDPDI aggregates formed and a well-resolved vibronic structure was yet illustrated due to the weakÏ€-Ï€interaction.N,N-dodecyl perylene diimide/sepiolite fiber compsite were prepared by liquid adsorption method and the adsorption kinetic comforms with the general rate law equation at the temperature of 19～80℃.At room temperature,the rate contact k_n is 0.11276.The active energy calculated from Arrhenius equation is 8.148 kJ.DDPDI aggregates were formed at the content of 2.5mg/g as confirmed by UV-vis spectroscopy.Also,a well-resolved vibronic structure has been observed upon aggregation due to weakÏ€-Ï€interaction.An excimer luminescence has been observed at the wavelength of 630nm upon the DDPDI content up to 3.34 whose intensity increased gradually with the increasing of the DDPDI content.