Ion fragmentations via photoelectron activated radical relays and competed hole oxidization on semiconductor nanoparticles for mass spectrometry

• Published in: Analytica chimica acta Vol. 1044; pp. 1 - 11
• Main Authors: Jiang, Ruowei, Qi, Yinghua, Gao, Anji, Zhong, Hongying
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 31-12-2018; Elsevier BV
• Subjects: Animals; Anions; Bismuth oxides; Bismuth trioxide; Chemical bonds; Chemical compounds; Chemical reactions; Contraction; Electron tunneling; Electrons; Energy; Exothermic reactions; Fragmentation; Free Radicals - chemistry; High energy electrons; Hydroxyl radicals; Ion fragmentation; Liver - chemistry; Liver - metabolism; Male; Mass spectrometric imaging; Mass Spectrometry; Mass spectroscopy; Metabolites; Nanoparticles; Nanoparticles - chemistry; Organic chemistry; Oxidation-Reduction; Particle Size; Photochemical Processes; Photoelectrons; Porosity; Quantum dots; Rats; Scientific imaging; Semiconductor lasers; Semiconductors; Soft ionization; Spectroscopy; Substitution reactions; Sulfaquinoxaline - analysis; Sulfaquinoxaline - metabolism; Surface Properties; Tandem mass spectrometry; YAG lasers; Zinc oxide; Electron tunneling; Tandem mass spectrometry; Soft ionization; Ion fragmentation; Mass spectrometric imaging
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2018.06.033

Structural identification is challenging in mass spectrometric imaging because of inadequate sample quantities and limited sampling time in each pixel for tandem mass spectrometry (MS/MS) experiments, which are usually used for the generation of fragment ions. We report herein the observation of a cascade of highly specific chemical bond cleavages via a low-energy photoelectron activated radical relays and a competed hole oxidization on surfaces of (Bi2O3)0.07(CoO)0.03(ZnO)0.9 semiconductor nanoparticles irradiated with the 3rd harmonic (355 nm) of the Nd3+: YAG laser. Distinguished from high energy electron impact (EI), this approach generates gaseous radical anions through the exothermic capture of low-energy tunneling electrons that are not able to cause extensive vibrational excitations. It was found not only original radical center but also secondary or even tertiary radical centers cause specific bond cleavages exclusively on α positions. The original radical center directly activates the cleavages of α-positioned chemical bonds that cause the formation of secondary radical centers. Ion fragmentations proceed along the newly formed radical centers that further activate the cleavages of their α-positioned chemical bonds. Using 8 compounds, we have demonstrated various radical reactions involved in desulfonation, cyclization, and ring contraction reactions as well as competed hole oxidization-generated hydroxyl radical substitution reactions. The interpretable fragment ions provide unambiguous experimental evidences for structural elucidation of drug residues and metabolites in mass spectrometric imaging of tissue slices without tandem mass spectrometry (MS/MS).
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•Electron-hole pairs are generated on surfaces of semiconductor nanoparticles irradiated with ultraviolet laser.•Exothermal capture of photoelectrons results in the formation of radical anions.•Low-energy photoelectrons activate radical relays and highly specific bond cleavages.•Electron-directed fragmentation is competed with that of hole oxidization.•Ion fragmentation without tandem mass spectrometry.