Synthesis of nanoparticles in a flame aerosol reactor with independent and strict control of their size, crystal phase and morphology (original) (raw)
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Journal of Nanoparticle Research, 2011
This study presents a novel exposure protocol for synthesized nanoparticles (NPs). NPs were synthesized in gas phase by thermal decomposition of metal alkoxide vapors in a laminar flow reactor. The exposure protocol was used to estimate the deposition fraction of titanium dioxide (TiO 2 ) NPs to mice lung. The experiments were conducted at aerosol mass concentrations of 0.8, 7.2, 10.0, and 28.5 mg m -3 . The means of aerosol geometric mobility diameter and aerodynamic diameter were 80 and 124 nm, and the geometric standard deviations were 1.8 and 1.7, respectively. The effective density of the particles was approximately from 1.5 to 1.7 g cm -3 . Particle concentration varied from 4 9 10 5 cm -3 at mass concentrations of 0.8 mg m -3 to 12 9 10 6 cm -3 at 28.5 mg m -3 . Particle phase structures were 74% of anatase and 26% of brookite with respective crystallite sized of 41 and 6 nm. The brookite crystallites were approximately 100 times the size of the anatase crystallites. The TiO 2 particles were porous and highly agglomerated, with a mean primary particle size of 21 nm. The specific surface area of TiO 2 powder was 61 m 2 g -1 . We defined mice respiratory minute volume (RMV) value during exposure to TiO 2 aerosol. Both TiO 2 particulate matter and gaseous by-products affected respiratory parameters. The RMV values were used to quantify the deposition fraction of TiO 2 matter by using two different methods. According to individual samples, the deposition fraction was 8% on an average, and when defined from aerosol mass concentration series, it was 7%. These results show that the exposure protocol can be used to study toxicological effects of synthesized NPs.
J Nanopart Res, 2011
This study presents a novel exposure protocol for synthesized nanoparticles (NPs). NPs were synthesized in gas phase by thermal decomposition of metal alkoxide vapors in a laminar flow reactor. The exposure protocol was used to estimate the deposition fraction of titanium dioxide (TiO 2 ) NPs to mice lung. The experiments were conducted at aerosol mass concentrations of 0.8, 7.2, 10.0, and 28.5 mg m -3 . The means of aerosol geometric mobility diameter and aerodynamic diameter were 80 and 124 nm, and the geometric standard deviations were 1.8 and 1.7, respectively. The effective density of the particles was approximately from 1.5 to 1.7 g cm -3 . Particle concentration varied from 4 9 10 5 cm -3 at mass concentrations of 0.8 mg m -3 to 12 9 10 6 cm -3 at 28.5 mg m -3 . Particle phase structures were 74% of anatase and 26% of brookite with respective crystallite sized of 41 and 6 nm. The brookite crystallites were approximately 100 times the size of the anatase crystallites. The TiO 2 particles were porous and highly agglomerated, with a mean primary particle size of 21 nm. The specific surface area of TiO 2 powder was 61 m 2 g -1 . We defined mice respiratory minute volume (RMV) value during exposure to TiO 2 aerosol. Both TiO 2 particulate matter and gaseous by-products affected respiratory parameters. The RMV values were used to quantify the deposition fraction of TiO 2 matter by using two different methods. According to individual samples, the deposition fraction was 8% on an average, and when defined from aerosol mass concentration series, it was 7%. These results show that the exposure protocol can be used to study toxicological effects of synthesized NPs.
ARTICLE IN PRESS G Model Diffusion flame synthesis of hollow, anatase TiO 2 nanoparticles
Well defined, dense, hollow spheres of anatase titania (TiO 2 ) nanoparticles were produced from TiCl 4 (as precursor) by diffusion flame technique. Flow rates of gases (LPG/air/N 2 compositions) were found to affect particle size. Titania nanoparticles were observed to decrease from 19 to 8 nm when the air flow rates were increased from 20 to 25 lpm. However, the particle size was found to increase from 15 to 21 nm when the nitrogen flow rate was increased from 0.8 to 2.0 lpm. LPG has been used as fuel. The increase in particle size of anatase TiO 2 was due to higher flame height and temperature. The anatase (TiO 2 ) phase was predominant compare to rutile phase in the ratio of 74:26 using air as an oxidant. In the gas phase reaction, the nanoparticles formation occurs due to spontaneous increase of number density of nuclei. The coagulation or aggregation of particles leads to the formation of larger particles due to higher chances of collisions among the particles and sintering at high flame temperature.
Flame-Nozzle Synthesis of Nanoparticles with Closely Controlled Size, Morphology and Crystallinity
Chemie Ingenieur Technik, 2002
A process for close control of primary particle size, morphology and crystallinity of flame-made nanoparticles is presented. According to this, freshly made titania aerosol nanoparticles are rapidly quenched in a critical flow nozzle, essentially freezing particle growth at desired levels. The nanoparticles are produced in a methane/oxygen diffusion flame reactor by oxidation of titanium-tetra-isopropoxide (TTIP). Precise control of the average primary particle size, reduced agglomeration and phase composition is achieved by positioning of the quenching nozzle above the burner and controlling gas and precursor flow rates. D
Journal of Nanoparticle Research, 2011
The intensive use of nano-sized titanium dioxide (TiO 2 ) particles in many different applications necessitates studies on their risk assessment as there are still open questions on their safe handling and utilization. For reliable risk assessment, the interaction of TiO 2 nanoparticles (NP) with biological systems ideally needs to be investigated using physico-chemically uniform and well-characterized NP. In this article, we describe the reproducible production of TiO 2 NP aerosols using spark ignition technology. Because currently no data are available on inhaled NP in the 10-50 nm diameter range, the emphasis was to generate NP as small as 20 nm for inhalation studies in rodents. For anticipated in vivo dosimetry analyses, TiO 2 NP were radiolabeled with 48 V by proton irradiation of the titanium electrodes of the spark generator. The dissolution rate of the 48 V label was about 1% within the first day. The highly concentrated, polydisperse TiO 2 NP aerosol (3-6 9 10 6 cm -3 ) proved to be constant over several hours in terms of its count median mobility diameter, its geometric standard deviation, and number concentration. Extensive characterization of NP chemical composition, physical structure, morphology, and specific surface area was performed. The originally generated amorphous TiO 2 NP were converted into crystalline anatase TiO 2 NP by thermal annealing at 950°C. Both crystalline and amorphous 20-nm TiO 2 NP were chain agglomerated/aggregated, consisting of primary particles in the range of 5 nm. Disintegration of the deposited TiO 2 NP in lung tissue was not detectable within 24 h.
Electronic Structure and Size of TiO 2 Nanoparticles of Controlled Size Prepared by Aerosol Methods
Monatshefte f�r Chemie / Chemical Monthly, 2002
A complete characterization of nanostructures has to deal both with electronic structure and dimensions. Here we present the characterization of TiO 2 nanoparticles of controlled size prepared by aerosol methods. The electronic structure of these nanoparticles was probed by X-ray absorption spectroscopy (XAS), the particle size by atomic force microscopy (AFM). XAS spectra show that the particles crystallize in the anatase phase upon heating at 500 C, whereas further annealing at 700 C give crystallites of 70% anatase and 30% rutile phases. Raising the temperature to 900 C results in a complete transformation of the particles to rutile. AFM images reveal that the mean size of the anatase particles formed upon heating at 500 C is 30 nm, whereas for the rutile particles formed upon annealing at 900 C 90 nm were found. The results obtained by these techniques agree with XRD data.
Analytical chemistry, 2014
Measuring stable clusters to understand particle inception will aid the synthesis of well-controlled nanoparticles via gas-phase aerosol routes. Using a Half Mini differential mobility analyzer, the presence of monomers, dimers, trimers, and tetramers was detected for the first time in a flame aerosol reactor during the synthesis of pristine TiO2 and TiO2/SiO2 nanocomposites. Atomic force microscopy confirmed the presence and the size of sub-2 nm clusters. The detection of these clusters elucidated the initial stages of particle formation during combustion synthesis and supported previous hypotheses that collisional growth from stable monomers of metal oxides is the first step of particle growth.
Characteristics of Tio 2 Nanoparticles Synthesized Through Low Temperature Aerosol Process
As one of the important process alternatives for the synthesis of nano materials with lower costs, flexibility and versatility, vapor phase synthesis of titania nano particles continue to attract attention. A low temperature aerosol process for the synthesis of titania nano particles is demonstrated by elucidating the influence of temperature, molar ratio of H 2 O/TiCl 4 and concentration of precursors on particle size and phase composition. This paper highlights the advantages of employing amorphous phase titania powder as solid precursor for its transformation to the rutile phase at temperatures less than 973K through vapor phase hydrolysis of TiCl 4 . A mechanistic hypothesis is proposed to explain the catalytic role of water vapor in the enhancement of amorphous to anatase phase transformation at high (15 to 27) molar ratio of H 2 O/TiCl 4 .
Synthesis of non-aggregated titania nanoparticles in atmospheric pressure diffusion flames
Powder Technology, 2006
Flame aerosol synthesis has been employed to synthesize nanoscale titania (TiO 2 ) particles by oxidation of titanium tetraisopropoxide (TTIP) vapor. The influence of reactant mixing and flow rates on particle morphology, size and phase composition has been studied for two different diffusion flame configurations using transmission electron microscopy, X-ray diffraction and photon correlation spectroscopy. Spherical, loosely agglomerated powders with a minimum secondary particle size of 90 nm and a rutile content of up to 35 w % were obtained at low oxygen flow rates in the double diffusion flame, while large anatase-rich aggregates formed at high oxygen flow rates. It is shown that the degree of aggregation of the as-synthesized particles is represented better by the ratio of d PCS 3 /d TEM 3 , than by the ratio of d BET 3 /d XRD 3 commonly used in literature. The differences observed in particle morphology and phase composition can be explained by considering their time-temperature history as a function of flame configuration and gas flow rates.