Enhanced photoluminescence properties of morin and trypsin absorbed on porous alumina films with ordered pores array

For the first time, the photoluminescence (PL) spectra of anodic porous alumina (P-Al) films impregnated with essentially non-fluorescent morin and morin-trypsin (Try) were investigated and compared with those of liquid solutions. It was found that their PL positions are similar to that of dye-Al³⁺ in ethanol solution, and the PL intensity of embedded dye-Try is much higher than that of embedded dye alone. We infer that the appearance of the PL band detected here is due to the formation of morin-Al complex in the holes of P-Al with the inner wall involved, and a likely luminescent mechanism is proposed to elucidate the PL enhancement phenomena due to the coexistence of morin and Try in the P-Al pores, which is confirmed by UV and FTIR measurements. Moreover, it is also found that the PL intensity increases with the pore size.