Cluster formation mechanisms of titanium dioxide during combustion synthesis: Observation with an APi-TOF

Jiaxi Fang, Yang Wang, Juha Kangasluoma, Michel Attoui, Heikki Junninen, Markku Kulmala, Tuukka Petäjä, Pratim Biswas

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Few studies reported the formation of Ti-containing clusters in the initial stages of TiO2 flame synthesis. The conversion from synthesis precursor to TiO2 monomers was commonly assumed to take place through global reaction such as thermal decomposition and/or hydrolysis at high temperatures. More recent studies have been able to identify stable intermediates of Ti-containing monomers, most commonly Ti(OH)4, as the final step before the formation of TiO2. However, no larger Ti-containing cluster formation mechanisms or interactions between these monomers have been tracked. To investigate cluster formation pathways of TiO2 during flame synthesis, Charged clusters were measured in an atmospheric pressure interface time-of-flight (APi-TOF) mass spectrometer. TiO2 nanoparticles were synthesized by adding titanium tetraisopropoxide (TTIP) precursor to a premixed CH4/O2/N2 flat flame aerosol reactor. Pure TiO2 clusters were not detected by the APi-TOF. Results from measured mass spectra and mass defect plots show that for positively charged clusters, the abstraction of CH2 groups occurs simultaneously with the clustering of larger intermediate organometallic species. For negatively charged clusters, NOx formation pathways in the flame may play a role during the initial stages of TiO2 formation, since a lot of Ti-containing clusters were attached with nitrate-related species. These research findings provide insights on quantum dot synthesis and molecular doping where rapid dilution of the flame synthesized nanoparticles is needed to better control the particle size and chemical composition. The possible influences of and potential artifacts brought by the dilution system on observing the incipient particle formation in flames were also discussed.

Original languageEnglish (US)
Pages (from-to)1071-1081
Number of pages11
JournalAerosol Science and Technology
Volume51
Issue number9
DOIs
StatePublished - Sep 2 2017
Externally publishedYes

ASJC Scopus subject areas

  • Environmental Chemistry
  • Materials Science(all)
  • Pollution

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