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.


Civil, Architectural and Environmental Engineering


This work is supported by the Solar Energy Research Institute for India and the United States (SERIIUS), funded jointly by the U.S. Department of Energy (Office of Science, Office of Basic Energy Sciences, and Energy Efficiency and Renewable Energy, Solar Energy Technology Program, under Subcontract DE-AC36-08GO28308 to the National Renewable Energy Laboratory, Golden, Colorado) and the Government of India, AEROSOL SCIENCE AND TECHNOLOGY 1079 through the Department of Science and Technology under Subcontract IUSSTF/JCERDC-SERIIUS/2012. The work was also supported by Academy of Finland via Center of Excellence project in Atmospheric Sciences (272041) and European Commission via ACTRIS2 (654109).

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)

0278-6826; 1521-7388

Document Type

Article - Journal

Document Version


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© 2017 American Association for Aerosol Research, All rights reserved.

Publication Date

01 Sep 2017