Cluster Formation Mechanisms of Titanium Dioxide during Combustion Synthesis: Observation with an APi-TOF
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.
J. Fang et al., "Cluster Formation Mechanisms of Titanium Dioxide during Combustion Synthesis: Observation with an APi-TOF," Aerosol Science and Technology, vol. 51, no. 9, pp. 1071-1081, Taylor & Francis, Sep 2017.
The definitive version is available at https://doi.org/10.1080/02786826.2017.1331028
Civil, Architectural and Environmental Engineering
Keywords and Phrases
Aerosols; Atmospheric pressure; Combustion; Combustion synthesis; Decomposition; Mass spectrometers; Mass spectrometry; Monomers; Organometallics; Particle size; Semiconductor quantum dots; Synthesis (chemical); Titanium dioxide; Chemical compositions; Cluster formations; Negatively charged; Particle formations; Positively charged; Quantum dot synthesis; TiO2 nano-particles; Titanium tetraisopropoxide; Flame synthesis; Monomer; Nitrate; Organometallic compound; Quantum dot; Titanium derivative; Titanium dioxide nanoparticle; Titanium tetraisopropoxide; Unclassified drug; Aerosol; Article; Artifact; Atmospheric pressure; Chemical composition; combustion; Decomposition; Flame; High temperature; Hydrolysis; Particle size; Priority journal; Synthesis
International Standard Serial Number (ISSN)
Article - Journal
© 2017 American Association for Aerosol Research, All rights reserved.
01 Sep 2017