Comparison of chemiluminescence from luminol solution and luminol-TiO₂ suspension after illumination of a 355 nm pulse laser.

Chemiluminescence (CL) from luminol solution and luminol-TiO₂ suspension after illumination of a 355 nm pulse laser is compared. Both the CL systems showed the CL spectra with maximum wavelength of 430 nm, suggesting that the emission was from the excite state of 3-aminophthalate ion. The TiO₂ photocatalytically induced luminol CL could be separately detected either when the pulse laser power was smaller than 0.15 mJ/pulse or a slit was placed beyond -2-2 mm in the vertical direction of the laser beam. The TiO₂ photocatalytically induced luminol CL intensity was linear to the laser power, while that of the 355 nm pulse laser-induced was nonlinear. A log-log plot between the 355 nm pulse laser-induced luminol CL intensity and laser power showed a near-linear regression fit with a slope of 2.11, suggesting that a two-photon absorption process of luminol was present in the 355 nm pulse laser-induced luminol CL. Adsorbed oxygen on the surface of TiO₂ seemed to greatly contribute to the photocatalytically induced CL.