Pratim Biswas - Academia.edu (original) (raw)

Papers by Pratim Biswas

Journal of Industrial and Engineering Chemistry, Dec 1, 2007

A laboratory-scale system incorporating a high temperature furnace has been utilized to study the... more A laboratory-scale system incorporating a high temperature furnace has been utilized to study the reaction of heavy metal species and sorbents. The interaction between heavy metal species (cadmium and lead) and sorbents for different injection conditions is studied. Three different sorbents, a solid phase pillar intercalated clay (PICL) and two in-situ generated silica and titania, are used for capture of the heavy metals. The in-situ generated silica agglomerates had a high surface area and suppressed nucleation of cadmium and lead species vapors over all injection conditions. The mean particle size of the resultant heavy metals-silica complex is significantly larger than that of heavy metals alone. It can be tuned for effective capture in existing particle control devices. However, in-situ generated titania showed spherical form due to slow collision characteristic time and hindered to grow by heavy metal species. It showed smaller particle size distribution compared to silica except for injection TiO 2 precursor into the first furnace and then injection heavy metal species into the second furnace. The solid phase pillar intercalated clay sorbent was not stable at 1000 o C, and structural changes resulted. The PICL sorbent showed low removal efficiency of heavy metals.

Aerosol Science and Technology, 2008

Film deposition by electrohydrodynamic atomization of nanoparticle sols was studied experimentall... more Film deposition by electrohydrodynamic atomization of nanoparticle sols was studied experimentally using zinc oxide nanoparticles in ethanol and using sequential Monte Carlo simulations, in which proper statistics and particle transport to the substrate were accounted for. Experimentally produced and simulated films were in good agreement, and simulations were used to determine the influences of deposition time, nanoparticle concentration in the sol, mean droplet size, and droplet polydispersity on the film thickness, porosity, surface roughness, and lateral feature size. Film growth rates were non-constant due to decreases in the film porosity early in the deposition process. Over time, the thickness of films increased, while the porosity decreased. After sufficient deposition time, the porosity reached a constant value and consequently the film growth rate was constant. The use of high concentration sols or large droplets resulted in the deposition of agglomerated particles, which gave rise to thicker, more porous films. Control over film morphology using droplets from size distributions with geometric standard deviations greater than 2.0 was not possible and the film thickness and air to particle volume ratio for all films produced from polydisperse droplets were convergent regardless of the number concentration of nanoparticles in the sol. Film surface roughnesses were less than the volume equivalent diameter of the agglomerated particles deposited, indicating that films were relatively uniform in thickness. Radial distribution functions were calculated for both experimentally deposited and simulated films and were used to determine lateral feature sizes. Lateral feature sizes increased with increasing deposition time and deposited agglomerate size until the deposition surface was completely covered. This work provides the necessary link between electrohydrodynamic atomization parameters and the resulting morphology of deposited films.

Current Pharmaceutical Design, Apr 27, 2016

This review gives a short overview on the widespread use of nanostructured and nanocomposite mate... more This review gives a short overview on the widespread use of nanostructured and nanocomposite materials for disease diagnostics, drug delivery, imaging and biomedical sensing applications. Nanoparticle interaction with a biological matrix/entity is greatly influenced by its morphology, crystal phase, surface chemistry, functionalization, physicochemical and electronic properties of the particle. Various nanoparticle synthesis routes, characteristization, and functionalization methodologies to be used for biomedical applications ranging from drug delivery to molecular probing of underlying mechanisms and concepts are described with several examples (150 references).

Nanoscale Research Letters, Jul 6, 2011

Synthesis and characterization of long wavelength visible-light absorption Cu-doped TiO 2 nanomat... more Synthesis and characterization of long wavelength visible-light absorption Cu-doped TiO 2 nanomaterials with wellcontrolled properties such as size, composition, morphology, and crystal phase have been demonstrated in a single-step flame aerosol reactor. This has been feasible by a detailed understanding of the formation and growth of nanoparticles in the high-temperature flame region. The important process parameters controlled were: molar feed ratios of precursors, temperature, and residence time in the high-temperature flame region. The ability to vary the crystal phase of the doped nanomaterials while keeping the primary particle size constant has been demonstrated. Results indicate that increasing the copper dopant concentration promotes an anatase to rutile phase transformation, decreased crystalline nature and primary particle size, and better suspension stability. Annealing the Cu-doped TiO 2 nanoparticles increased the crystalline nature and changed the morphology from spherical to hexagonal structure. Measurements indicate a band gap narrowing by 0.8 eV (2.51 eV) was achieved at 15-wt.% copper dopant concentration compared to pristine TiO 2 (3.31 eV) synthesized under the same flame conditions. The change in the crystal phase, size, and band gap is attributed to replacement of titanium atoms by copper atoms in the TiO 2 crystal.

Toxicology, Jul 1, 2012

There is an urgent need for in vitro screening assays to evaluate nanoparticle (NP) toxicity. How... more There is an urgent need for in vitro screening assays to evaluate nanoparticle (NP) toxicity. However, the relevance of in vitro assays is still disputable. We administered doses of TiO 2 NPs of different sizes to alveolar epithelial cells in vitro and the same NPs by intratracheal instillation in rats in vivo to examine the correlation between in vitro and in vivo responses. The correlations were based on toxicity rankings of NPs after adopting NP surface area as dose metric, and response per unit surface area as response metric. Sizes of the anatase TiO 2 NPs ranged from 3 to 100 nm. A cell-free assay for measuring reactive oxygen species (ROS) was used, and lactate dehydrogenase (LDH) release, and protein oxidation induction were the in vitro cellular assays using a rat lung Type I epithelial cell line (R3/1) following 24 hr incubation. The in vivo endpoint was number of PMNs in bronchoalveolar lavage fluid (BALF) after exposure of rats to the NPs via intratracheal instillation. Slope analyses of the dose response curves shows that the in vivo and in vitro responses were well correlated. We conclude that using the approach of steepest slope analysis offers a superior method to correlate in vitro with in vivo results of NP toxicity and for ranking their toxic potency.

Single-step processing of copper-doped titania nanomaterials in a flame aerosol reactor

Energy and environmental issues, such as fossil fuel shortage and climate change are global chall... more Energy and environmental issues, such as fossil fuel shortage and climate change are global challenges that need to be addressed. Research and innovation in sustainable energy-related functional materials, produced by environmentally benign technologies, will play a critical role in meeting these challenges. In this sense, energy, environment, and materials constitute a trinomial combination of special relevance for the sustainable development of our society. Aerosol science and technology is an enabling discipline that can address these issues effectively. These gas phase techniques are widely recognized as being capable of producing a variety of novel materials with controlled functionality for energy and environmental applications. Fundamental principles of aerosol processing of materials are briefly described. Specific examples of advanced functional materials development by using aerosol processes are demonstrated, such as photocatalysts for carbon dioxide photoreduction and th...

Nanoscale Advances, 2020

Synthesis of Cu-doped TiO2 nanostructures with excellent high-rate lithium-ion battery performanc... more Synthesis of Cu-doped TiO2 nanostructures with excellent high-rate lithium-ion battery performance and enhanced lithium-ion diffusion.

ACS Applied Bio Materials, 2019

Titanium dioxide (TiO 2) nanoparticles have shown success as photosensitizers in the form of ligh... more Titanium dioxide (TiO 2) nanoparticles have shown success as photosensitizers in the form of lightbased cancer therapy called Cerenkov radiation induced therapy (CRIT). While TiO 2 nanoparticles have been reported to be an effective therapeutic agent, there has been little work to control their functionalization and stability in aqueous suspension. In this work, the controlled coating of 25 nm diameter TiO 2 nanoparticles with the glycoprotein transferrin (Tf) for application in CRIT was demonstrated using an electrospray system. Monodisperse nanoscale droplets containing TiO 2 and Tf were dried during flight, coating the proteins on the surface of the metal oxide nanoparticles. Real-time scanning mobility particle sizing, dynamic light scattering, and transmission electron microscopy show efficient control of the Tf coating thickness when varying the droplet size and the ratio of Tf to TiO 2 in the electrospray precursor suspension. Further, the functionality of Tfcoated TiO 2 nanoparticles was demonstrated, and these particles were found to have enhanced targeting activity of Tf to the Tf receptor after electrospray processing. The electrospray-coated Tf/TiO 2 particles were also found to be more effective at killing the multiple myeloma cell line MM1.S than that of nanoparticles prepared by other reported functionalization methods. In summary, this investigation not only provides a single-step functionalization technique for *

Aerosol Science and Technology, 2017

The ability to properly scale the synthesis of advanced materials through combustion synthesis ro... more The ability to properly scale the synthesis of advanced materials through combustion synthesis routes is limited by our lack of knowledge regarding the initial stages of particle formation. In flame aerosol reactors, the high temperatures, fast reaction rates, and flame chemistry can all play a critical role in determining the properties of the resulting nanomaterials. In particular, multicomponent systems pose a unique challenge as most studies rely on empirical approaches toward designing advanced composite materials. The lack of predictive capabilities can be attributed to a lack of data on particle inception and growth below 2 nm. Measurements for the initial stages of particle formation during the combustion synthesis of SiO 2 and composite SiO 2 /TiO 2 using an atmospheric pressure inlet time-of-flight mass spectrometer are presented. Both positively and negatively charged clusters can be measured and results show the presence of silicic acid species which grow through dehydration, hydrogen abstraction, and interactions with hydroxyl radicals. In the case of composite SiO 2 /TiO 2 particle formation, new molecular species containing Ti atoms emerge. Tandem differential mobility analysis-mass spectrometry (DMA-MS) provided further insight into the size-resolved chemistry of particle formation to reveal that at each cluster size, further hydroxyl-driven reactions take place. From this we can conclude that previous assumptions on collisional growth from simple monomer species of SiO 2 and TiO 2 do not sufficiently describe the collisional growth mechanisms for particle growth below 2 nm.

Aerosol Science and Technology, 2016

Composite nanoparticles find application in catalysis, drug delivery, and energy storage and requ... more Composite nanoparticles find application in catalysis, drug delivery, and energy storage and require increasingly fine control of their physical properties and composition. While composite nanoparticles have been widely synthesized and characterized, little work has systematically correlated the initial concentration of precursors and the final composition of flame synthesized composite nanoparticles. This relationship is explored in a diffusion flame aerosol reactor by coupling a scanning mobility particle sizer (SMPS) with an inductively coupled plasma optical emission spectrometer (ICP-OES). A framework for studying the relationship between the initial precursor concentrations of different elements and the final nanoparticle composition is explored. The size-resolved elemental composition was measured by directly injecting size-selected fractions of aggregated magnetite and silicon dioxide composite nanoparticles into the ICP-OES plasma. This work showed a correlation between precursor molar ratio and the measured elemental ratio in the mobility size range of 50 to 140 nm. Building on previous work studying size resolved elemental composition of engineered nanoparticles, the analysis is extended to flame synthesized composite nanoparticle aggregates in this work.

Aerosol Science and Technology, 2017

Flames generate a large amount of chemically and thermally ionized species, which are involved in... more Flames generate a large amount of chemically and thermally ionized species, which are involved in the growth dynamics of particles formed in flames. However, existing models predicting particle formation and growth do not consider particle charging, which may lead to bias in the calculated size distribution of particles. In this study, Fuchs' charging theory was coupled with a monodisperse particle growth model to study the simultaneous charging and coagulation of nanoparticles during combustion. In order to quantify the charging characteristics of nanoparticles, a high-resolution DMA was used to measure the mobilities of ions generated from a premixed flat flame operated at various conditions. The effect of temperature on ion-particle and particle-particle combination coefficients was further examined. The proposed model showed that the influence of charging on particle growth dynamics was more prominent when the ion concentration was comparable to or higher than the particle concentrations, a condition that may be encountered in flame synthesis and solid fuel-burning. Simulated results also showed that unipolar ion environments strongly suppressed the coagulation of particles. In the end, a simplified analysis of the relative importance of particle charging and coagulation was proposed by comparing the characteristic time scales of these two mechanisms.

Chemical Engineering Journal, 2017

The aerosol chemical vapor deposition (ACVD) process has been demonstrated as a promising approac... more The aerosol chemical vapor deposition (ACVD) process has been demonstrated as a promising approach to the single step synthesis of nanostructured metal oxide thin films. Multiple process parameters control the nanostructure morphology and the growth of thin films. This work focuses on utilizing a simulation based approach to understand the role of these parameters in governing the morphology of the thin film. A finite element based computational fluid dynamics model, coupled with a discrete-sectional aerosol model, and a boundary layer diffusion and sintering model has been formulated to predict the evolution of particle size distribution and the morphology of the synthesized nanostructured film. The morphology predicted by the model was validated by experimental observations. The model enables scale up and wider application of the ACVD process and can be extended to other gas phase deposition systems.

Current Pharmaceutical Design, 2016

Catalysts, 2013

TiO 2 nanostructured films were synthesized by an aerosol chemical vapor deposition (ACVD) method... more TiO 2 nanostructured films were synthesized by an aerosol chemical vapor deposition (ACVD) method with different controlled morphologies: columnar, granular, and branched structures for the photocatalytic inactivation of Escherichia coli (E. coli) in water. Effects of film morphology and external applied voltage on inactivation rate were investigated. As-prepared films were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and UV-VIS. Photocatalytic and photoelectrochemical inactivation of E. coli using as-prepared TiO 2 films were performed under irradiation of UVA light (note: UVA has a low efficiency to inactivate E. coli). Inactivation rate constants for each case were obtained from their respective inactivation curve through a 2 h incubation period. Photocatalytic inactivation rate constants of E. coli are 0.02/min (using columnar films), and 0.08/min (using branched films). The inactivation rate constant for the columnar film was enhanced by 330% by applied voltage on the film while that for the branched film was increased only by 30%. Photocatalytic microbial inactivation rate of the columnar and the branched films were also compared taking into account their different surface areas. Since the majority of the UV radiation that reaches the Earth's surface is UVA, this study provides an opportunity to use sunlight to efficiently decontaminate drinking water.

Toxicology, 2012

There is an urgent need for in vitro screening assays to evaluate nanoparticle (NP) toxicity. How... more There is an urgent need for in vitro screening assays to evaluate nanoparticle (NP) toxicity. However, the relevance of in vitro assays is still disputable. We administered doses of TiO 2 NPs of different sizes to alveolar epithelial cells in vitro and the same NPs by intratracheal instillation in rats in vivo to examine the correlation between in vitro and in vivo responses. The correlations were based on toxicity rankings of NPs after adopting NP surface area as dose metric, and response per unit surface area as response metric. Sizes of the anatase TiO 2 NPs ranged from 3 to 100 nm. A cell-free assay for measuring reactive oxygen species (ROS) was used, and lactate dehydrogenase (LDH) release, and protein oxidation induction were the in vitro cellular assays using a rat lung Type I epithelial cell line (R3/1) following 24 hr incubation. The in vivo endpoint was number of PMNs in bronchoalveolar lavage fluid (BALF) after exposure of rats to the NPs via intratracheal instillation. Slope analyses of the dose response curves shows that the in vivo and in vitro responses were well correlated. We conclude that using the approach of steepest slope analysis offers a superior method to correlate in vitro with in vivo results of NP toxicity and for ranking their toxic potency.

Nanotoxicology, 2008

A method to investigate the dependence of the physicochemical properties of nanoparticles (e.g. s... more A method to investigate the dependence of the physicochemical properties of nanoparticles (e.g. size, surface area and crystal phase) on their oxidant generating capacity is proposed and demonstrated for TiO 2 nanoparticles. Gas phase synthesis methods that allow for strict control of size and crystal phase were used to prepare TiO 2 nanoparticles. The reactive oxygen species (ROS) generating capacity of these particles was then measured. The size dependent ROS activity was established using TiO 2 nanoparticles of 9 different sizes (4-195 nm) but the same crystal phase. For a fixed total surface area, an S-shaped curve for ROS generation per unit surface area was observed as a function of particle size. The highest ROS activity per unit area was observed for 30 nm particles, and observed to be constant above 30 nm. There was a decrease in activity per unit area as size decreased from 30 nm to 10 nm; and again constant for particles smaller than 10 nm. The correlation between crystal phase and oxidant capacity was established using TiO 2 nanoparticles of 11 different crystal phase combinations but similar size. The ability of different crystal phases of TiO 2 nanoparticles to generate ROS was highest for amorphous, followed by anatase, and then anatase/rutile mixtures, and lowest for rutile samples. Based on evaluation of the entire dataset, important dose metrics for ROS generation are established. Their implications of these ROS studies on biological and toxicological studies using nanomaterials are discussed.

Nanotechnology, 2007

A flame aerosol reactor (FLAR) was developed to synthesize nanoparticles with desired properties ... more A flame aerosol reactor (FLAR) was developed to synthesize nanoparticles with desired properties (crystal phase and size) that could be independently controlled. The methodology was demonstrated for TiO 2 nanoparticles, and this is the first time that large sets of samples with the same size but different crystal phases (six different ratios of anatase to rutile in this work) were synthesized. The degree of TiO 2 nanoparticle agglomeration was determined by comparing the primary particle size distribution measured by scanning electron microscopy (SEM) to the mobility-based particle size distribution measured by online scanning mobility particle spectrometry (SMPS). By controlling the flame aerosol reactor conditions, both spherical unagglomerated particles and highly agglomerated particles were produced. To produce monodisperse nanoparticles, a high throughput multi-stage differential mobility analyser (MDMA) was used in series with the flame aerosol reactor. Nearly monodisperse nanoparticles (geometric standard deviation less than 1.05) could be collected in sufficient mass quantities (of the order of 10 mg) in reasonable time (1 h) that could be used in other studies such as determination of functionality or biological effects as a function of size.

Nanoscale Research Letters, 2011

Synthesis and characterization of long wavelength visible-light absorption Cu-doped TiO2 nanomate... more Synthesis and characterization of long wavelength visible-light absorption Cu-doped TiO2 nanomaterials with well-controlled properties such as size, composition, morphology, and crystal phase have been demonstrated in a single-step flame aerosol reactor. This has been feasible by a detailed understanding of the formation and growth of nanoparticles in the high-temperature flame region. The important process parameters controlled were: molar feed ratios of precursors, temperature, and residence time in the high-temperature flame region. The ability to vary the crystal phase of the doped nanomaterials while keeping the primary particle size constant has been demonstrated. Results indicate that increasing the copper dopant concentration promotes an anatase to rutile phase transformation, decreased crystalline nature and primary particle size, and better suspension stability. Annealing the Cu-doped TiO2 nanoparticles increased the crystalline nature and changed the morphology from spher...

Nanoscale Research Letters, 2010

Characterizing nanoparticle dispersions and understanding the effect of parameters that alter dis... more Characterizing nanoparticle dispersions and understanding the effect of parameters that alter dispersion properties are important for both environmental applications and toxicity investigations. The role of particle surface area, primary particle size, and crystal phase on TiO2 nanoparticle dispersion properties is reported. Hydrodynamic size, zeta potential, and isoelectric point (IEP) of ten laboratory synthesized TiO2 samples, and one commercial Degussa TiO2 sample (P25) dispersed in different solutions were characterized. Solution ionic strength and pH affect titania dispersion properties. The effect of monovalent (NaCl) and divalent (MgCl2) inert electrolytes on dispersion properties was quantified through their contribution to ionic strength. Increasing titania particle surface area resulted in a decrease in solution pH. At fixed pH, increasing the particle surface area enhanced the collision frequency between particles and led to a higher degree of agglomeration. In addition ...

Journal of Industrial and Engineering Chemistry, Dec 1, 2007

A laboratory-scale system incorporating a high temperature furnace has been utilized to study the... more A laboratory-scale system incorporating a high temperature furnace has been utilized to study the reaction of heavy metal species and sorbents. The interaction between heavy metal species (cadmium and lead) and sorbents for different injection conditions is studied. Three different sorbents, a solid phase pillar intercalated clay (PICL) and two in-situ generated silica and titania, are used for capture of the heavy metals. The in-situ generated silica agglomerates had a high surface area and suppressed nucleation of cadmium and lead species vapors over all injection conditions. The mean particle size of the resultant heavy metals-silica complex is significantly larger than that of heavy metals alone. It can be tuned for effective capture in existing particle control devices. However, in-situ generated titania showed spherical form due to slow collision characteristic time and hindered to grow by heavy metal species. It showed smaller particle size distribution compared to silica except for injection TiO 2 precursor into the first furnace and then injection heavy metal species into the second furnace. The solid phase pillar intercalated clay sorbent was not stable at 1000 o C, and structural changes resulted. The PICL sorbent showed low removal efficiency of heavy metals.

Aerosol Science and Technology, 2008

Film deposition by electrohydrodynamic atomization of nanoparticle sols was studied experimentall... more Film deposition by electrohydrodynamic atomization of nanoparticle sols was studied experimentally using zinc oxide nanoparticles in ethanol and using sequential Monte Carlo simulations, in which proper statistics and particle transport to the substrate were accounted for. Experimentally produced and simulated films were in good agreement, and simulations were used to determine the influences of deposition time, nanoparticle concentration in the sol, mean droplet size, and droplet polydispersity on the film thickness, porosity, surface roughness, and lateral feature size. Film growth rates were non-constant due to decreases in the film porosity early in the deposition process. Over time, the thickness of films increased, while the porosity decreased. After sufficient deposition time, the porosity reached a constant value and consequently the film growth rate was constant. The use of high concentration sols or large droplets resulted in the deposition of agglomerated particles, which gave rise to thicker, more porous films. Control over film morphology using droplets from size distributions with geometric standard deviations greater than 2.0 was not possible and the film thickness and air to particle volume ratio for all films produced from polydisperse droplets were convergent regardless of the number concentration of nanoparticles in the sol. Film surface roughnesses were less than the volume equivalent diameter of the agglomerated particles deposited, indicating that films were relatively uniform in thickness. Radial distribution functions were calculated for both experimentally deposited and simulated films and were used to determine lateral feature sizes. Lateral feature sizes increased with increasing deposition time and deposited agglomerate size until the deposition surface was completely covered. This work provides the necessary link between electrohydrodynamic atomization parameters and the resulting morphology of deposited films.

Current Pharmaceutical Design, Apr 27, 2016

This review gives a short overview on the widespread use of nanostructured and nanocomposite mate... more This review gives a short overview on the widespread use of nanostructured and nanocomposite materials for disease diagnostics, drug delivery, imaging and biomedical sensing applications. Nanoparticle interaction with a biological matrix/entity is greatly influenced by its morphology, crystal phase, surface chemistry, functionalization, physicochemical and electronic properties of the particle. Various nanoparticle synthesis routes, characteristization, and functionalization methodologies to be used for biomedical applications ranging from drug delivery to molecular probing of underlying mechanisms and concepts are described with several examples (150 references).

Nanoscale Research Letters, Jul 6, 2011

Synthesis and characterization of long wavelength visible-light absorption Cu-doped TiO 2 nanomat... more Synthesis and characterization of long wavelength visible-light absorption Cu-doped TiO 2 nanomaterials with wellcontrolled properties such as size, composition, morphology, and crystal phase have been demonstrated in a single-step flame aerosol reactor. This has been feasible by a detailed understanding of the formation and growth of nanoparticles in the high-temperature flame region. The important process parameters controlled were: molar feed ratios of precursors, temperature, and residence time in the high-temperature flame region. The ability to vary the crystal phase of the doped nanomaterials while keeping the primary particle size constant has been demonstrated. Results indicate that increasing the copper dopant concentration promotes an anatase to rutile phase transformation, decreased crystalline nature and primary particle size, and better suspension stability. Annealing the Cu-doped TiO 2 nanoparticles increased the crystalline nature and changed the morphology from spherical to hexagonal structure. Measurements indicate a band gap narrowing by 0.8 eV (2.51 eV) was achieved at 15-wt.% copper dopant concentration compared to pristine TiO 2 (3.31 eV) synthesized under the same flame conditions. The change in the crystal phase, size, and band gap is attributed to replacement of titanium atoms by copper atoms in the TiO 2 crystal.

Toxicology, Jul 1, 2012

There is an urgent need for in vitro screening assays to evaluate nanoparticle (NP) toxicity. How... more There is an urgent need for in vitro screening assays to evaluate nanoparticle (NP) toxicity. However, the relevance of in vitro assays is still disputable. We administered doses of TiO 2 NPs of different sizes to alveolar epithelial cells in vitro and the same NPs by intratracheal instillation in rats in vivo to examine the correlation between in vitro and in vivo responses. The correlations were based on toxicity rankings of NPs after adopting NP surface area as dose metric, and response per unit surface area as response metric. Sizes of the anatase TiO 2 NPs ranged from 3 to 100 nm. A cell-free assay for measuring reactive oxygen species (ROS) was used, and lactate dehydrogenase (LDH) release, and protein oxidation induction were the in vitro cellular assays using a rat lung Type I epithelial cell line (R3/1) following 24 hr incubation. The in vivo endpoint was number of PMNs in bronchoalveolar lavage fluid (BALF) after exposure of rats to the NPs via intratracheal instillation. Slope analyses of the dose response curves shows that the in vivo and in vitro responses were well correlated. We conclude that using the approach of steepest slope analysis offers a superior method to correlate in vitro with in vivo results of NP toxicity and for ranking their toxic potency.

Single-step processing of copper-doped titania nanomaterials in a flame aerosol reactor

Energy and environmental issues, such as fossil fuel shortage and climate change are global chall... more Energy and environmental issues, such as fossil fuel shortage and climate change are global challenges that need to be addressed. Research and innovation in sustainable energy-related functional materials, produced by environmentally benign technologies, will play a critical role in meeting these challenges. In this sense, energy, environment, and materials constitute a trinomial combination of special relevance for the sustainable development of our society. Aerosol science and technology is an enabling discipline that can address these issues effectively. These gas phase techniques are widely recognized as being capable of producing a variety of novel materials with controlled functionality for energy and environmental applications. Fundamental principles of aerosol processing of materials are briefly described. Specific examples of advanced functional materials development by using aerosol processes are demonstrated, such as photocatalysts for carbon dioxide photoreduction and th...

Nanoscale Advances, 2020

Synthesis of Cu-doped TiO2 nanostructures with excellent high-rate lithium-ion battery performanc... more Synthesis of Cu-doped TiO2 nanostructures with excellent high-rate lithium-ion battery performance and enhanced lithium-ion diffusion.

ACS Applied Bio Materials, 2019

Titanium dioxide (TiO 2) nanoparticles have shown success as photosensitizers in the form of ligh... more Titanium dioxide (TiO 2) nanoparticles have shown success as photosensitizers in the form of lightbased cancer therapy called Cerenkov radiation induced therapy (CRIT). While TiO 2 nanoparticles have been reported to be an effective therapeutic agent, there has been little work to control their functionalization and stability in aqueous suspension. In this work, the controlled coating of 25 nm diameter TiO 2 nanoparticles with the glycoprotein transferrin (Tf) for application in CRIT was demonstrated using an electrospray system. Monodisperse nanoscale droplets containing TiO 2 and Tf were dried during flight, coating the proteins on the surface of the metal oxide nanoparticles. Real-time scanning mobility particle sizing, dynamic light scattering, and transmission electron microscopy show efficient control of the Tf coating thickness when varying the droplet size and the ratio of Tf to TiO 2 in the electrospray precursor suspension. Further, the functionality of Tfcoated TiO 2 nanoparticles was demonstrated, and these particles were found to have enhanced targeting activity of Tf to the Tf receptor after electrospray processing. The electrospray-coated Tf/TiO 2 particles were also found to be more effective at killing the multiple myeloma cell line MM1.S than that of nanoparticles prepared by other reported functionalization methods. In summary, this investigation not only provides a single-step functionalization technique for *

Aerosol Science and Technology, 2017

The ability to properly scale the synthesis of advanced materials through combustion synthesis ro... more The ability to properly scale the synthesis of advanced materials through combustion synthesis routes is limited by our lack of knowledge regarding the initial stages of particle formation. In flame aerosol reactors, the high temperatures, fast reaction rates, and flame chemistry can all play a critical role in determining the properties of the resulting nanomaterials. In particular, multicomponent systems pose a unique challenge as most studies rely on empirical approaches toward designing advanced composite materials. The lack of predictive capabilities can be attributed to a lack of data on particle inception and growth below 2 nm. Measurements for the initial stages of particle formation during the combustion synthesis of SiO 2 and composite SiO 2 /TiO 2 using an atmospheric pressure inlet time-of-flight mass spectrometer are presented. Both positively and negatively charged clusters can be measured and results show the presence of silicic acid species which grow through dehydration, hydrogen abstraction, and interactions with hydroxyl radicals. In the case of composite SiO 2 /TiO 2 particle formation, new molecular species containing Ti atoms emerge. Tandem differential mobility analysis-mass spectrometry (DMA-MS) provided further insight into the size-resolved chemistry of particle formation to reveal that at each cluster size, further hydroxyl-driven reactions take place. From this we can conclude that previous assumptions on collisional growth from simple monomer species of SiO 2 and TiO 2 do not sufficiently describe the collisional growth mechanisms for particle growth below 2 nm.

Aerosol Science and Technology, 2016

Composite nanoparticles find application in catalysis, drug delivery, and energy storage and requ... more Composite nanoparticles find application in catalysis, drug delivery, and energy storage and require increasingly fine control of their physical properties and composition. While composite nanoparticles have been widely synthesized and characterized, little work has systematically correlated the initial concentration of precursors and the final composition of flame synthesized composite nanoparticles. This relationship is explored in a diffusion flame aerosol reactor by coupling a scanning mobility particle sizer (SMPS) with an inductively coupled plasma optical emission spectrometer (ICP-OES). A framework for studying the relationship between the initial precursor concentrations of different elements and the final nanoparticle composition is explored. The size-resolved elemental composition was measured by directly injecting size-selected fractions of aggregated magnetite and silicon dioxide composite nanoparticles into the ICP-OES plasma. This work showed a correlation between precursor molar ratio and the measured elemental ratio in the mobility size range of 50 to 140 nm. Building on previous work studying size resolved elemental composition of engineered nanoparticles, the analysis is extended to flame synthesized composite nanoparticle aggregates in this work.

Aerosol Science and Technology, 2017

Flames generate a large amount of chemically and thermally ionized species, which are involved in... more Flames generate a large amount of chemically and thermally ionized species, which are involved in the growth dynamics of particles formed in flames. However, existing models predicting particle formation and growth do not consider particle charging, which may lead to bias in the calculated size distribution of particles. In this study, Fuchs' charging theory was coupled with a monodisperse particle growth model to study the simultaneous charging and coagulation of nanoparticles during combustion. In order to quantify the charging characteristics of nanoparticles, a high-resolution DMA was used to measure the mobilities of ions generated from a premixed flat flame operated at various conditions. The effect of temperature on ion-particle and particle-particle combination coefficients was further examined. The proposed model showed that the influence of charging on particle growth dynamics was more prominent when the ion concentration was comparable to or higher than the particle concentrations, a condition that may be encountered in flame synthesis and solid fuel-burning. Simulated results also showed that unipolar ion environments strongly suppressed the coagulation of particles. In the end, a simplified analysis of the relative importance of particle charging and coagulation was proposed by comparing the characteristic time scales of these two mechanisms.

Chemical Engineering Journal, 2017

The aerosol chemical vapor deposition (ACVD) process has been demonstrated as a promising approac... more The aerosol chemical vapor deposition (ACVD) process has been demonstrated as a promising approach to the single step synthesis of nanostructured metal oxide thin films. Multiple process parameters control the nanostructure morphology and the growth of thin films. This work focuses on utilizing a simulation based approach to understand the role of these parameters in governing the morphology of the thin film. A finite element based computational fluid dynamics model, coupled with a discrete-sectional aerosol model, and a boundary layer diffusion and sintering model has been formulated to predict the evolution of particle size distribution and the morphology of the synthesized nanostructured film. The morphology predicted by the model was validated by experimental observations. The model enables scale up and wider application of the ACVD process and can be extended to other gas phase deposition systems.

Current Pharmaceutical Design, 2016

Catalysts, 2013

TiO 2 nanostructured films were synthesized by an aerosol chemical vapor deposition (ACVD) method... more TiO 2 nanostructured films were synthesized by an aerosol chemical vapor deposition (ACVD) method with different controlled morphologies: columnar, granular, and branched structures for the photocatalytic inactivation of Escherichia coli (E. coli) in water. Effects of film morphology and external applied voltage on inactivation rate were investigated. As-prepared films were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and UV-VIS. Photocatalytic and photoelectrochemical inactivation of E. coli using as-prepared TiO 2 films were performed under irradiation of UVA light (note: UVA has a low efficiency to inactivate E. coli). Inactivation rate constants for each case were obtained from their respective inactivation curve through a 2 h incubation period. Photocatalytic inactivation rate constants of E. coli are 0.02/min (using columnar films), and 0.08/min (using branched films). The inactivation rate constant for the columnar film was enhanced by 330% by applied voltage on the film while that for the branched film was increased only by 30%. Photocatalytic microbial inactivation rate of the columnar and the branched films were also compared taking into account their different surface areas. Since the majority of the UV radiation that reaches the Earth's surface is UVA, this study provides an opportunity to use sunlight to efficiently decontaminate drinking water.

Toxicology, 2012

There is an urgent need for in vitro screening assays to evaluate nanoparticle (NP) toxicity. How... more There is an urgent need for in vitro screening assays to evaluate nanoparticle (NP) toxicity. However, the relevance of in vitro assays is still disputable. We administered doses of TiO 2 NPs of different sizes to alveolar epithelial cells in vitro and the same NPs by intratracheal instillation in rats in vivo to examine the correlation between in vitro and in vivo responses. The correlations were based on toxicity rankings of NPs after adopting NP surface area as dose metric, and response per unit surface area as response metric. Sizes of the anatase TiO 2 NPs ranged from 3 to 100 nm. A cell-free assay for measuring reactive oxygen species (ROS) was used, and lactate dehydrogenase (LDH) release, and protein oxidation induction were the in vitro cellular assays using a rat lung Type I epithelial cell line (R3/1) following 24 hr incubation. The in vivo endpoint was number of PMNs in bronchoalveolar lavage fluid (BALF) after exposure of rats to the NPs via intratracheal instillation. Slope analyses of the dose response curves shows that the in vivo and in vitro responses were well correlated. We conclude that using the approach of steepest slope analysis offers a superior method to correlate in vitro with in vivo results of NP toxicity and for ranking their toxic potency.

Nanotoxicology, 2008

A method to investigate the dependence of the physicochemical properties of nanoparticles (e.g. s... more A method to investigate the dependence of the physicochemical properties of nanoparticles (e.g. size, surface area and crystal phase) on their oxidant generating capacity is proposed and demonstrated for TiO 2 nanoparticles. Gas phase synthesis methods that allow for strict control of size and crystal phase were used to prepare TiO 2 nanoparticles. The reactive oxygen species (ROS) generating capacity of these particles was then measured. The size dependent ROS activity was established using TiO 2 nanoparticles of 9 different sizes (4-195 nm) but the same crystal phase. For a fixed total surface area, an S-shaped curve for ROS generation per unit surface area was observed as a function of particle size. The highest ROS activity per unit area was observed for 30 nm particles, and observed to be constant above 30 nm. There was a decrease in activity per unit area as size decreased from 30 nm to 10 nm; and again constant for particles smaller than 10 nm. The correlation between crystal phase and oxidant capacity was established using TiO 2 nanoparticles of 11 different crystal phase combinations but similar size. The ability of different crystal phases of TiO 2 nanoparticles to generate ROS was highest for amorphous, followed by anatase, and then anatase/rutile mixtures, and lowest for rutile samples. Based on evaluation of the entire dataset, important dose metrics for ROS generation are established. Their implications of these ROS studies on biological and toxicological studies using nanomaterials are discussed.

Nanotechnology, 2007

A flame aerosol reactor (FLAR) was developed to synthesize nanoparticles with desired properties ... more A flame aerosol reactor (FLAR) was developed to synthesize nanoparticles with desired properties (crystal phase and size) that could be independently controlled. The methodology was demonstrated for TiO 2 nanoparticles, and this is the first time that large sets of samples with the same size but different crystal phases (six different ratios of anatase to rutile in this work) were synthesized. The degree of TiO 2 nanoparticle agglomeration was determined by comparing the primary particle size distribution measured by scanning electron microscopy (SEM) to the mobility-based particle size distribution measured by online scanning mobility particle spectrometry (SMPS). By controlling the flame aerosol reactor conditions, both spherical unagglomerated particles and highly agglomerated particles were produced. To produce monodisperse nanoparticles, a high throughput multi-stage differential mobility analyser (MDMA) was used in series with the flame aerosol reactor. Nearly monodisperse nanoparticles (geometric standard deviation less than 1.05) could be collected in sufficient mass quantities (of the order of 10 mg) in reasonable time (1 h) that could be used in other studies such as determination of functionality or biological effects as a function of size.

Nanoscale Research Letters, 2011

Synthesis and characterization of long wavelength visible-light absorption Cu-doped TiO2 nanomate... more Synthesis and characterization of long wavelength visible-light absorption Cu-doped TiO2 nanomaterials with well-controlled properties such as size, composition, morphology, and crystal phase have been demonstrated in a single-step flame aerosol reactor. This has been feasible by a detailed understanding of the formation and growth of nanoparticles in the high-temperature flame region. The important process parameters controlled were: molar feed ratios of precursors, temperature, and residence time in the high-temperature flame region. The ability to vary the crystal phase of the doped nanomaterials while keeping the primary particle size constant has been demonstrated. Results indicate that increasing the copper dopant concentration promotes an anatase to rutile phase transformation, decreased crystalline nature and primary particle size, and better suspension stability. Annealing the Cu-doped TiO2 nanoparticles increased the crystalline nature and changed the morphology from spher...

Nanoscale Research Letters, 2010

Characterizing nanoparticle dispersions and understanding the effect of parameters that alter dis... more Characterizing nanoparticle dispersions and understanding the effect of parameters that alter dispersion properties are important for both environmental applications and toxicity investigations. The role of particle surface area, primary particle size, and crystal phase on TiO2 nanoparticle dispersion properties is reported. Hydrodynamic size, zeta potential, and isoelectric point (IEP) of ten laboratory synthesized TiO2 samples, and one commercial Degussa TiO2 sample (P25) dispersed in different solutions were characterized. Solution ionic strength and pH affect titania dispersion properties. The effect of monovalent (NaCl) and divalent (MgCl2) inert electrolytes on dispersion properties was quantified through their contribution to ionic strength. Increasing titania particle surface area resulted in a decrease in solution pH. At fixed pH, increasing the particle surface area enhanced the collision frequency between particles and led to a higher degree of agglomeration. In addition ...