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Mass spectrometric monitoring of interfacial photoelectron transfer and imaging of active crystalline facets of semiconductors.

ABSTRACT: Monitoring of interfacial electron transfer (ET) in situ is important to understand the ET mechanism and designing efficient photocatalysts. We describe herein a mass spectrometric approach to investigate the ultrafast transfer of photoelectrons that are generated by ultraviolet irradiation on surfaces of semiconductor nanoparticles or crystalline facets. The mass spectrometric approach can not only untargetedly detect various intermediates but also monitor their reactivity through associative or dissociative photoelectron capture dissociation, as well as electron detachment dissociation of adsorbed molecules. Proton-coupled electron transfer and proton-uncoupled electron transfer with radical initiated polymerization or hydroxyl radical abstraction have been unambiguously demonstrated with the mass spectrometric approach. Active crystalline facets of titanium dioxide for photocatalytic degradation of juglone and organochlorine dichlorodiphenyltrichloroethane are visualized with mass spectrometry imaging based on ion scanning and spectral reconstruction. This work provides a new technique for studying photo-electric properties of various materials.

SUBMITTER: Zhong H

PROVIDER: S-EPMC5322523 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Mass spectrometric monitoring of interfacial photoelectron transfer and imaging of active crystalline facets of semiconductors.

Zhong Hongying H Zhang Juan J Tang Xuemei X Zhang Wenyang W Jiang Ruowei R Li Rui R Chen Disong D Wang Peng P Yuan Zhiwei Z

Nature communications 20170222

Monitoring of interfacial electron transfer (ET) in situ is important to understand the ET mechanism and designing efficient photocatalysts. We describe herein a mass spectrometric approach to investigate the ultrafast transfer of photoelectrons that are generated by ultraviolet irradiation on surfaces of semiconductor nanoparticles or crystalline facets. The mass spectrometric approach can not only untargetedly detect various intermediates but also monitor their reactivity through associative o ...[more]

PMID: 28224986

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Project description:Decavanadate (V10O28 6- or V10) is a paradigmatic member of the polyoxidometalate (POM) family, which has been attracting much attention within both materials/inorganic and biomedical communities due to its unique structural and electrochemical properties. In this work we explored the utility of high-resolution electrospray ionization (ESI) mass spectrometry (MS) and ion exclusion chromatography LC/MS for structural analysis of V10 species in aqueous solutions. While ESI generates abundant molecular ions representing the intact V10 species, their isotopic distributions show significant deviations from the theoretical ones. A combination of high-resolution MS measurements and hydrogen/deuterium exchange allows these deviations to be investigated and interpreted as a result of partial reduction of V10. While the redox processes are known to occur in the ESI interface and influence the oxidation state of redox-active analytes, the LC/MS measurements using ion exclusion chromatography provide unequivocal evidence that the mixed-valence V10 species exist in solution, as extracted ion chromatograms representing V10 molecular ions at different oxidation states exhibit distinct elution profiles. The spontaneous reduction of V10 in solution is seen even in the presence of hydrogen peroxide and has not been previously observed. The susceptibility to reduction of V10 is likely to be shared by other redox active POMs. In addition to the molecular V10 ions, a high-abundance ionic signal for a V10O26 2- anion was displayed in the negative-ion ESI mass spectra. None of the V10O26 cations were detected in ESI MS, and only a low-abundance signal was observed for V10O26 anions with a single negative charge, indicating that the presence of abundant V10O26 2- anions in ESI MS reflects gas-phase instability of V10O28 anions carrying two charges. The gas-phase origin of the V10O26 2- anion was confirmed in tandem MS measurements, where mild collisional activation was applied to V10 molecular ions with an even number of hydrogen atoms (H4V10O28 2-), resulting in a facile loss of H2O molecules and giving rise to V10O26 2- as the lowest-mass fragment ion. Water loss was also observed for V10O28 anions carrying an odd number of hydrogen atoms (e.g., H5V10O28 -), followed by a less efficient and incomplete removal of an OH• radical, giving rise to both HV10O26 - and V10O25 - fragment ions. Importantly, at least one hydrogen atom was required for ion fragmentation in the gas phase, as no further dissociation was observed for any hydrogen-free V10 ionic species. The presented workflow allows a distinction to be readily made between the spectral features revealing the presence of non-canonical POM species in the bulk solution from those that arise due to physical and chemical processes occurring in the ESI interface and/or the gas phase.

Dataset Information

Mass spectrometric monitoring of interfacial photoelectron transfer and imaging of active crystalline facets of semiconductors.

Publications

Mass spectrometric monitoring of interfacial photoelectron transfer and imaging of active crystalline facets of semiconductors.

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