Induced Nanoelectrospray Ionization for Spontaneous Singlet Oxygen Formation and Oxidative Transformation of Pollutants

Abstract Induced nanoelectrospray ionization (induced nESI) is a noncontact, in situ spray methodology initiated by an externally applied high-voltage electric field. Within this setup, the mass spectrometer serves as a counter electrode that shapes the electric-field distribution and governs charge transport via electrostatic induction, thereby sustaining a stable spray containing positive and negative ions. Notably, the rapid transition from bulk solution into highly charged microdroplets triggers the spontaneous, in situ generation of singlet oxygen (1O2) at the μg mL−1 level, providing the first experimental evidence of spontaneous 1O2 generation within an induced nESI source. Mass spectrometric analysis confirmed this selective 1O2-mediated oxidation, revealing the characteristic signals of 9,10-diphenylanthracene oxidation products with a mass increase of 32 Da. 1O2 formation was further validated using multiple chemical probes, including 1,5-dihydroxynaphthalene, 1,3-diphenylisobenzofuran, and furfuryl alcohol, complemented by deuterium oxide−induced lifetime enhancement and radical-trapping experiments. Leveraging this highly selective oxidation mechanism, this platform enables the efficient transformation of six representative organic pollutants, including dibenzo-p-dioxin and bisphenol A. Collectively, these results establish induced nESI as a powerful new analytical and reaction platform for advanced oxidation processes.