Final Report Summary - FLAMENANOMANUFACTURE (Flame Aerosol Reactors for Manufacturing of Surface-Functionalized Nanoscale Materials and Devices)
This research focused on scalable flame (aerosol) synthesis of functional nanomaterials for devices. The program had 3 columns: a) quantitative understanding of the ensuing aerosol dynamics of fractal-like nanoparticles for development of efficient processes for synthesis of b) novel nanomaterials and c) their incorporation into functional products and devices.
The first column was addressed with multi-scale modeling of aerosol synthesis of nanoparticles. By mesoscale simulations we developed power laws that showed how fractal-like particles fuse or sinter or coalesce from ramified filamentary to compact shape, regardless of sintering mechanism and primary particle size distribution. Using these laws and mass-mobility measurements, we showed, for the first time, how to distinguish between flame-made aggregate and agglomerate nanoparticles and identify conditions for their synthesis as they have distinctly different industrial applications. Various aspects of this research received prizes in 5 different intnl. conferences. By molecular dynamics (MD) we showed how individual TiO2 primary particle pairs sinter, revealing, for the first time again, that during the industrially-relevant gas-phase particle formation by coagulation-coalescence, surface diffusion is the dominant mechanism rather than the sintering mechanisms derived by conventional sintering experiments of powder compacts. Furthermore easy-to-use expressions for the coalescence of nanoparticles were developed from these MD simulations to be readily used for mesoscale and computational fluid-particle dynamics for process design for manufacture of nanoparticles. Such an understanding facilitated the construction a unique pilot plant (at an academic institution) for continuous synthesis of nanoparticles up to 5 kg/h that has facilitated our interaction with industry.
Our second research column on novel nanomaterial development focused on the performance & health effects of plasmonic, superparamagnetic and phosphorescent compositions for their broad applications, esp. in bioimaging. By preparation of nanosilver solutions of different particle size, we quantified, for the first time, the bactericidal action of silver ions in aquatic solutions, to one or two surface layers with decreasing nanosilver size. This motivated synthesis of biocompatible Ag-Au nanoalloys as Au seems to preferentially occupy the alloy particle surface drastically reducing the release of toxic silver ions in aquatic solutions. A unique achievement of our program is the hermetic coating of nanoparticles by nanothin silica films at appreciable production rates, 25 g/h. For example, we showed, for the first time, how toxic nanosilver could be “cured” so-to-speak by such films and harvest its plasmonic properties. Also Janus-like particles with superparamagnetic Fe2O3 and nano-Ag for imaging of cancer cells were made. This concept was applied to various nanoparticle compositions bringing a number of awards and distinctions to our students and even impacting other fields. In fact, the U.S. National Science Foundation awarded a 3-year grant to the Harvard School of Public Health to distinguish between chemical and physical toxicity of nanomaterials using this technique. An intriguing advancement was the rapid synthesis and deposition of multi-layered and -functional nanocomposite films of high filler content (up to 40% wt) opening the potential for synthesis of magnetic cantilevers and highly conductive nanocomposite films. Furthermore, we advanced synthesis of gas sensing and catalytic nanomaterials, most notably by our invention of flame-made crystalline Ti-suboxides onto nanosilver/TiO2 that exhibit superior visible-light photocatalytic performance. Very recently, we have been developing novel nanomaterials for magnetic resonance imaging and theranostics.
Our third research column focused on the development of devices with the above inexpensive nanomaterials. So a number of device components were built including heterogeneous catalysts, gas sensors, battery electrodes, solar cells and flexible, magnetic cantilevers demonstrating the potential of this technology. Perhaps the most visible achievement was the full assembly of portable, WO3-based breath acetone sensors for diabetics that were successfully tested online and offline with humans. So, it was shown that such sensors have the potential to replace the cumbersome finger-pricking of diabetics in the morning, the standard test for diagnosis and monitoring of diabetes. Most notably, our sensor was integrated into an industrial prototype for clinical evaluations by Loccioni SA in Italy.
The first column was addressed with multi-scale modeling of aerosol synthesis of nanoparticles. By mesoscale simulations we developed power laws that showed how fractal-like particles fuse or sinter or coalesce from ramified filamentary to compact shape, regardless of sintering mechanism and primary particle size distribution. Using these laws and mass-mobility measurements, we showed, for the first time, how to distinguish between flame-made aggregate and agglomerate nanoparticles and identify conditions for their synthesis as they have distinctly different industrial applications. Various aspects of this research received prizes in 5 different intnl. conferences. By molecular dynamics (MD) we showed how individual TiO2 primary particle pairs sinter, revealing, for the first time again, that during the industrially-relevant gas-phase particle formation by coagulation-coalescence, surface diffusion is the dominant mechanism rather than the sintering mechanisms derived by conventional sintering experiments of powder compacts. Furthermore easy-to-use expressions for the coalescence of nanoparticles were developed from these MD simulations to be readily used for mesoscale and computational fluid-particle dynamics for process design for manufacture of nanoparticles. Such an understanding facilitated the construction a unique pilot plant (at an academic institution) for continuous synthesis of nanoparticles up to 5 kg/h that has facilitated our interaction with industry.
Our second research column on novel nanomaterial development focused on the performance & health effects of plasmonic, superparamagnetic and phosphorescent compositions for their broad applications, esp. in bioimaging. By preparation of nanosilver solutions of different particle size, we quantified, for the first time, the bactericidal action of silver ions in aquatic solutions, to one or two surface layers with decreasing nanosilver size. This motivated synthesis of biocompatible Ag-Au nanoalloys as Au seems to preferentially occupy the alloy particle surface drastically reducing the release of toxic silver ions in aquatic solutions. A unique achievement of our program is the hermetic coating of nanoparticles by nanothin silica films at appreciable production rates, 25 g/h. For example, we showed, for the first time, how toxic nanosilver could be “cured” so-to-speak by such films and harvest its plasmonic properties. Also Janus-like particles with superparamagnetic Fe2O3 and nano-Ag for imaging of cancer cells were made. This concept was applied to various nanoparticle compositions bringing a number of awards and distinctions to our students and even impacting other fields. In fact, the U.S. National Science Foundation awarded a 3-year grant to the Harvard School of Public Health to distinguish between chemical and physical toxicity of nanomaterials using this technique. An intriguing advancement was the rapid synthesis and deposition of multi-layered and -functional nanocomposite films of high filler content (up to 40% wt) opening the potential for synthesis of magnetic cantilevers and highly conductive nanocomposite films. Furthermore, we advanced synthesis of gas sensing and catalytic nanomaterials, most notably by our invention of flame-made crystalline Ti-suboxides onto nanosilver/TiO2 that exhibit superior visible-light photocatalytic performance. Very recently, we have been developing novel nanomaterials for magnetic resonance imaging and theranostics.
Our third research column focused on the development of devices with the above inexpensive nanomaterials. So a number of device components were built including heterogeneous catalysts, gas sensors, battery electrodes, solar cells and flexible, magnetic cantilevers demonstrating the potential of this technology. Perhaps the most visible achievement was the full assembly of portable, WO3-based breath acetone sensors for diabetics that were successfully tested online and offline with humans. So, it was shown that such sensors have the potential to replace the cumbersome finger-pricking of diabetics in the morning, the standard test for diagnosis and monitoring of diabetes. Most notably, our sensor was integrated into an industrial prototype for clinical evaluations by Loccioni SA in Italy.