Detection of Hydrogen Peroxide Using Photofragmentation Laser-Induced Fluorescence

Abstract

Photofragmentation laser-induced fluorescence (PF-LIF) is for the first time demonstrated to be a practical diagnostic tool for detection of hydrogen peroxide. Point measurements as well as two-dimensional (2D) measurements in free-flows, with nitrogen as bath gas, are reported. The present application of the PF-LIF technique involves one laser, emitting radiation of 266 nm wavelength, to dissociate hydrogen peroxide molecules into OH radicals, and another laser, emitting at 282.25 nm, to electronically excite OH, whose laser-induced fluorescence is detected. The measurement procedure is explained in detail and a suitable time separation between photolysis and excitation pulse is proposed to be on the order of a few hundred nanoseconds. With a separation time in that regime, recorded OH excitation scans were found to be thermal and the signal was close to maximum. The PF-LIF signal strength was shown to follow the same trend as the vapor pressure corresponding to the hydrogen peroxide liquid concentration. Thus, the PF-LIF signal appeared to increase linearly with hydrogen peroxide vapor-phase concentration. For 2D single shot measurements, a conservatively estimated value of the detection limit is 30 ppm. Experiments verified that for averaged point measurements the detection limit was well below 30 ppm.

Solution to the perturbation of LIF measurements via photodissociation, OH measurement in atmospheric‐pressure multihollow DBD

“…The plasma product cannot be identified from the presented fluorescence measurements. However, we can suppose that hydrogen peroxide is this species, as it can produce OH radicals by photodissociation [31,32] and it can be produced in the studied discharge. H 2 O 2 is generated in atmospheric-pressure discharges via the three-body recombination of OH radicals, eventually by the reaction of OH with excited water molecules.…”

Simultaneous Visualization of Hydrogen Peroxide and Water Concentrations Using Photofragmentation Laser-Induced Fluorescence

“…The dye laser was fired 100 ns after the excimer laser in order to ensure that the OH fragments had attained thermal equilibrium at the time of the arrival of the 282 nm probe pulse. 8 A schematic description of the experimental setup is illustrated in Fig. S2 (Supplemental Material).…”

“…A UV-laser pulse first photodissociates the H 2 O 2 molecule into two OH fragments, whereupon a probe laser pulse, tuned to an absorption line of OH, induces fluorescence, whose intensity is related to the H 2 O 2 concentration. The PFLIF technique for H 2 O 2 has been demonstrated for 2-D measurements under ambient conditions, 8 but also in various fields such as combustion diagnostics and for sterilization of food packages. 9 For combustion diagnostics H 2 O 2 has been visualized both in flames 10 and in an HCCI engine 11 detection was limited due to poor collimation characteristics of the excimer laser beam, preventing efficient focusing of the beam, which is critical for the 2-photon LIF signal as it depends on the square of the laser intensity.…”

Quantitative Imaging of Ozone Vapor Using Photofragmentation Laser-Induced Fluorescence (LIF)

“…Nevertheless, it is possible to detect ozone by first photodissociating the molecule with a pump photon, creating O and O 2 , whereupon a second photon (probe) detects the O 2 photofragment using PLIF. This pump-probe technique is called photofragmentation laser induced fluorescence (PF-LIF) and has previously been applied for visualization of hydrogen peroxides in free gas flows, 24,25 flames, 26 and combustion engines. 27 Furthermore, Pitz et al have previously applied the measurement concept in flow-field velocimetry based on photochemical ozone production.…”