Chemiluminescence from luminol solution after illumination of a 355 nm pulse laser

Abstract

Chemiluminescence (CL) on the time scale of microseconds to milliseconds from luminol solution after illumination of a 355 nm pulse laser is reported. It was found that the CL is the emission from 3-aminophthalate ion (AP*). In CL decay after the pulse laser illumination, a peak was observed from about 200 to 30 micros depending on the laser power and the luminol concentration. It seemed that there was a fast and slow decay process; their kinetics were greatly dependent on the laser power and the luminol concentration. Dissolved oxygen was involved in the CL and played the same role on the whole time scale of microseconds to milliseconds. Involvement of reactive oxygen species such as H(2)O(2), (1)O(2), O(2) (*-) and OH in the CL was examined by adding their scavengers. Experimental results suggested that the possibility of involvement of H(2)O(2) and (1)O(2) in the CL was low. The CL in time periods less than 50 micros might be related to *OH. The (*)O(2) (*-)-induced CL increased with time after 50 micros and became dominant on the time scale of milliseconds. The CL was considered to be caused by both the photoionization and type I reaction mechanisms.

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

“…On the other hand, CL spectra of the both CL systems were basically the same as that from a typical luminol CL such as luminol–H 2 O 2 –K 4 Fe(CN) 6 system, with a maximum CL wavelength of about 430 nm. [18] This suggested that the emitters were AP* in both CL systems. Qualitatively, no remarkable difference was observed between the two CL systems in absorbance, fluorescence and CL spectra.…”

“…In our previous paper, it was discussed that there seemed to be an exponential function during 0.15–1.00 mJ/pulse, a linear function during 1.00–2.55 mJ/pulse and another exponential function during 2.55–3.20 mJ/pulse between the 355 nm pulse laser‐induced CL intensity and the laser power. [18] Here, the relation between the 355 nm pulse laser‐induced luminol CL intensity and laser power was further studied by using a log–log plot as shown in Fig. 2(B).…”

“…Experimental setup for the time‐resolved CL system was similar to that reported before. [14–18] Luminol solution or luminol–TiO 2 suspension was added to a quartz cell (1 × 1 × 4 cm). A slit with size adjusted to prevent saturation of CL respondence was used as shown in Fig.…”

“…1(A). [18] The suspension in the cell was stirred with a mini‐stirrer (Pasolina, TR‐100) with speed of 600 rpm, and was illuminated by a third harmonic light (355 nm) of a Q‐switched Nd–YAG laser (pulse width 4–6 ns; maximum output 3.20 mJ/pulse; frequency 10 Hz; Continuum, CA, USA). Light emission from the cell was collected in a perpendicular direction to the excitation light by two lenses.…”

“…[14–17] It was proposed that •OH was greatly involved in the CL on the µs ∼ ms timescale, especially in time period less than 100 µs after illumination of the pulse laser, while CL generated by O 2 •− began to increase from 100 µs, and became dominant after 2.5 ms. On the other hand, luminol CL was also observed in luminol solution even without existence of TiO 2 after illumination of the 355 nm pulse laser, which was considered to be produced by both the photoionization and type‐I reaction mechanisms. [18] Therefore, the CL from luminol–TiO 2 –355 nm pulse laser system must be consisted of two parts mechanistically. One was the 355 nm pulse laser‐induced luminol CL, and the other was the TiO 2 photocatalytically induced luminol CL, i.e.…”