Enhancing Effect of Alcoholic Solvent on Hydrosulfite-Hydrogen Peroxide Chemiluminescence System

In this work, a chemiluminescence (CL) reaction between hydrogen peroxide (H2O2) and sodium hydrosulfite (NaHSO3) was developed. Hydroxyl radical ((OH)-O-center dot) and sulfite radical ((SO3-)-S-center dot) were the main intermediates generated in the NaHSO3-H2O2 CL system. Inhibition effects of radical scavengers such as thiourea, chloride ion, nitro blue tetrazolium chloride (NBT), and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) indicated the existence of these two radicals. Singlet oxygen (O-1(2)) and excited sulfur dioxide (SO2*) were emitting species involved in NaHSO3-H2O2 CL system. O-1(2) were confirmed by 1,4-diazobicyclo[2,2,2]octane (DABCO) and sodium azide (NaN3), which were specific O-1(2) scavengers. In addition, electron spin resonance (ESR) spectra clearly show the existence of O-1(2) and (OH)-O-center dot. Alcoholic solvent, especially n-butanol, enhanced the ultraweak CL emission more than 40 times. The enhancing effect of alcoholic solvent on NaHSO3-H2O2 CL system was ascribed to the formation of solvent cage, which can accelerate the reaction rate and protect the emitting species from quenching by water. The CL emission of the NaHSO3-n-butanol-H2O2 system was measured by cutoff filters. The maximum wavelength was located around 490 nm, which belongs to O-1(2). The wide peak from 400 to 600 nm is the characteristic peak of SO2*.