Tumor-derived exosomes may provide biomarkers for cancer treatment. Using sputtering technology, ... more Tumor-derived exosomes may provide biomarkers for cancer treatment. Using sputtering technology, an affinity-based device to capture exosomes was developed using nanoporous substrate (NPG)-coated silicon microscopy. Immunology-based techniques detect and purify exosomes using gold coating with a specific antigen. Inverted fluorescent microscopy was used to detect target exosomes quantitatively utilizing fluorescent nanospheres as the label. We quantified the expression of CD63 surface protein markers on exosomes from conditioned culture media of breast cancer cells. The exosomes that targeted specific proteins with controls were statistically analyzed and compared to those that targeted non-specific proteins. Results from SEM showed that the exosomes were circular, between 30 and 150 nanometers in size. The porous gold substrates captured more exosomes than the nonporous substrates. Nitric acid treatments at different times resulted in a variety of pore sizes. Despite the increase i...
In the present study, a novel diamine 1,4-bis[4-(hydrazonomethyl)phenoxy]butane (4-BHPB) has been... more In the present study, a novel diamine 1,4-bis[4-(hydrazonomethyl)phenoxy]butane (4-BHPB) has been successfully synthesized by a facile method.
Several metal oxides, such as tungsten oxide (WO3), are considered superior sensing materials for... more Several metal oxides, such as tungsten oxide (WO3), are considered superior sensing materials for hydrogen sulfide (H2S) detection in the ambient environment. In this study, silver loaded tungsten oxide nanoparticles were prepared by microwave-assisted chemical route. Nanoparticle thin films were deposited on substrates with electrical electrodes to explore their gas sensing and electrical properties. The morphology, crystal structure, and chemical state were examined using x-ray diffraction (XRD), scanning electron mi-]] ]]
In this paper, we report oxidation time effect on highly porous silver oxide nanowires thin films... more In this paper, we report oxidation time effect on highly porous silver oxide nanowires thin films fabricated using ultrasonic spray pyrolysis and oxygen plasma etching method. The NW’s morphological, electrical, and optical properties were investigated under different plasma etching periods and the number of deposition cycles. The increase of plasma etching and oxidation time increases the surface roughness of the Ag NWs until it fused to form a porous thin film of silver oxide. AgNWs based thin films were characterized using X-ray diffraction, scanning electron microscope, transmission electron microscope, X-ray photoemission spectroscopy, and UV–Vis spectroscopy techniques. The obtained results indicate the formation of mixed mesoporous Ag2O and AgO NW thin films. The Ag2O phase of silver oxide appears after 300 s of oxidation under the same conditions, while the optical transparency of the thin film decreases as plasma etching time increases. The sheet resistance of the final fil...
ABSTRACT In this paper, we present a novel synthesis approach for preparation of Magnesium Hydrox... more ABSTRACT In this paper, we present a novel synthesis approach for preparation of Magnesium Hydroxide, Mg(OH)2, having nano-sheets morphologies that can find applications in plastic industry as flame-retardant and reinforcing material and can be used for conservation of paper based cultural heritage. The nanomaterials were successfully synthesized using novel microwave synthesis technique using Magnesium sulfates as precursor and Cetyltrimethylammonium bromide (CTAB) as dispersant. The nano-sheets were produced through a reaction of Magnesium sulfates with NaOH in a microwave chemical reactor, operated at a controlled power rating for specific time. A good yield of the precipitates, produced as a result of reaction, were isolated, washed, dried and were subjected to heat treatment at 300 oC to remove the organic dispersant. Characterization technique such as XRD, SEM, HR-TEM were used to elucidate the composition and structure of Mg(OH)2 nanomaterial. The data obtained from these techniques confirmed successful synthesis and nano-structure of Mg(OH)2. The BET surface area and nitrogen adsorption/desorption measurements of Mg(OH)2 nanoparticles showed a surface area of 80.27 m2/g. HRTEM analysis revealed the morphology of Mg(OH)2 to be composed of nano sheets with a unique packing structure that gives a highly porous nano structure to the material. The Mg(OH)2 particles with a size smaller than 5 nm were observed which, in our opinion, can be used for diverse applications.
ABSTRACT Thermal insulation is considered one of the main factors of reducing heat and energy con... more ABSTRACT Thermal insulation is considered one of the main factors of reducing heat and energy consumption in buildings. There are many insulation materials used to reduce energy consumption and heat loss in buildings, such as: cellulose, glass wool, rock wool, polystyrene, urethane foam.., etc. Unfortunately, most of these materials have problems with their durability, effectiveness and cost. Aerogels being ultra-light, highly porous and highly thermal insulating materials are being considered for applications as varied as thermal and sound insulation for aerospace applications, as absorbents for environmental remediation and as supports for catalysts [1-4]. However, the major problem with aerogels is their mechanically fragility that impeded their commercialization and limited their fabrication in the form of granules or panels of limited thickness. Aerogel production is a slow and tedious process. Wet gels, termed aquogels or alcogels depending on the solvent can be rapidly synthesized following well-established procedures [5,6] but drying is timeconsuming. Because of capillary forces the solvent cannot be evaporated without cracking and shrinking the monolith. We want to share very interesting results of a novel synthesis approach through which mechanically strong aerogels can be fabricated just in few hours instead of few days. The other novelties associated with our process is one pot synthesis for both native and cross-linked aerogels and no need for time consuming process of multiple solvent exchanges. This also significantly truncate large volume of fresh solvent required during the conventional synthesis process. The results are of particular importance, since they dramatically shorten fabrication times for monoliths with large sizes of native and, most importantly, of cross-linked aerogel. We have synthesized samples using base- and acid-catalyzed chemistries, varied alkoxide concentration and, for cross-linked aerogels, monomer concentration. Depending on alkoxide concentration, native oxide aerogels had densities between about 0.06 and 0.17 g.cm-3 and surface areas between about 300 and 500 m2.g-1. Figure 1 shows our synthesized Aerogels. Our group has been developing alternative fabrication methods which enable to produce custom parts which are made mechanically strong by reinforcing the regions of highest solicitation with a polymer. We have fabricated custom parts that may be used as insulation of selected parts of internal combustion engines, passive fire protection of structural elements in building, and lightweight footwear for extreme cold conditions. We also have developed cost-effective and scalable procedures for fabricating these custom- shaped aerogels.
ABSTRACT Thermal insulation is considered one of the main factors of reducing heat and energy con... more ABSTRACT Thermal insulation is considered one of the main factors of reducing heat and energy consumption in buildings. There are many insulation materials used to reduce energy consumption and heat loss in buildings, such as: cellulose, glass wool, rock wool, polystyrene, urethane foam.., etc. Unfortunately, most of these materials have problems with their durability, effectiveness and cost. Aerogels being ultra-light, highly porous and highly thermal insulating materials are being considered for applications as varied as thermal and sound insulation for aerospace applications, as absorbents for environmental remediation and as supports for catalysts [1-4]. However, the major problem with aerogels is their mechanically fragility that impeded their commercialization and limited their fabrication in the form of granules or panels of limited thickness. Aerogel production is a slow and tedious process. Wet gels, termed aquogels or alcogels depending on the solvent can be rapidly synthesized following well-established procedures [5,6] but drying is timeconsuming. Because of capillary forces the solvent cannot be evaporated without cracking and shrinking the monolith. We want to share very interesting results of a novel synthesis approach through which mechanically strong aerogels can be fabricated just in few hours instead of few days. The other novelties associated with our process is one pot synthesis for both native and cross-linked aerogels and no need for time consuming process of multiple solvent exchanges. This also significantly truncate large volume of fresh solvent required during the conventional synthesis process. The results are of particular importance, since they dramatically shorten fabrication times for monoliths with large sizes of native and, most importantly, of cross-linked aerogel. We have synthesized samples using base- and acid-catalyzed chemistries, varied alkoxide concentration and, for cross-linked aerogels, monomer concentration. Depending on alkoxide concentration, native oxide aerogels had densities between about 0.06 and 0.17 g.cm-3 and surface areas between about 300 and 500 m2.g-1. Figure 1 shows our synthesized Aerogels. Our group has been developing alternative fabrication methods which enable to produce custom parts which are made mechanically strong by reinforcing the regions of highest solicitation with a polymer. We have fabricated custom parts that may be used as insulation of selected parts of internal combustion engines, passive fire protection of structural elements in building, and lightweight footwear for extreme cold conditions. We also have developed cost-effective and scalable procedures for fabricating these custom- shaped aerogels.
Cigarettes et constituants de cigarettes, par exemple du tabac de remplissage et du papier a ciga... more Cigarettes et constituants de cigarettes, par exemple du tabac de remplissage et du papier a cigarette, et procede de fabrication de constituants de cigarettes comportant des fibrilles nanostructurees. Ces fibrilles nanostructurees, qui sont eventuellement formees et deposees in situ sur le tabac de remplissage et/ou le papier a cigarette par condensation controlee a vaporisation au laser ou par reaction chimique, sont aptes a servir d'oxydant pour la transformation du monoxyde de carbone en gaz carbonique et/ou de catalyseur pour la transformation du monoxyde de carbone en gaz carbonique. On a egalement prevu des cigarettes comportant du tabac de remplissage et du papier a cigarette, dans lesquelles les fibrilles nanostructurees sont deposees ou incorporer dans le tabac de remplissage et/ou le papier a cigarette.
In the present study, a novel diamine 1,4-bis[4-(hydrazonomethyl)phenoxy]butane (4-BHPB) has been... more In the present study, a novel diamine 1,4-bis[4-(hydrazonomethyl)phenoxy]butane (4-BHPB) has been successfully synthesized by a facile method. 4-BHPB was reacted with pyromellitic dianhydride (PMDA) to derive a novel polyimide (PI). Highly compatibilized PI–SiO2 nanocomposites were tailored using synthesized PI matrix and modified silica nanoparticles. The compatibility between organic–inorganic (O–I) components was remarkably improved by charge transfer complex (CTC) formed between PI chains and modified silica nanoparticles. PI chains have electron donor and acceptor groups (diamine and dianhydride portion, respectively). These groups were generated in silica nanoparticles by the organic modification through 2,6-bis(3-(triethoxysilyl)propyl)pyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone (M-SiO2), which in turn, was prepared reacting PMDA with 3-aminopropyltriethoxysilane. Sol–gel method was used for in situ synthesis of silica nanoparticles from a mixture of M-SiO2 and TEOS. The ...
1,2 Farman Ali, Shaukat Saeed*, Khaled M. Saoud and Syed Sakhawat Shah 1 Department of Metallurgy... more 1,2 Farman Ali, Shaukat Saeed*, Khaled M. Saoud and Syed Sakhawat Shah 1 Department of Metallurgy and Materials Engineering (DMME), Pakistan Institute of Engineering and Applied Sciences (PIEAS), PO Nilore, Islamabad-45650, Pakistan. 2 Department of Chemistry, Hazara University Mansehra, 21120, Pakistan. Liberal Arts and Science Program, Virginia Commonwealth University in Qatar, Doha, Qatar. [email protected], [email protected]*
Self-sustaining and hysteresis behavior of low-temperature CO oxidation on mesoporous Pd/SiO2 aer... more Self-sustaining and hysteresis behavior of low-temperature CO oxidation on mesoporous Pd/SiO2 aerogel s catalyst under dynamics conditions
Cross-linked silica aerogels are promising, strong, lightweight materials for photolithographic a... more Cross-linked silica aerogels are promising, strong, lightweight materials for photolithographic applications. The work presented here details the preparation of ultra-lightweight aerogel materials with tailored properties through the appropriate combination of silica and methacrylate polymer using laser-induced rapid photogelation fabrication technique. For fabrication, an ethanolic solution of hexanediol diacrylate, tetraorthosilicate, Eosin Y and a tertiary amine was prepared. The amounts of reactants were varied to prepare different compositions of aerogel monoliths. The solution was irradiated with a green beam from a low power laser source. The samples, after drying in supercritical ethanol, were characterized using FTIR, BET, SEM, TGA, and a mechanical testing instrument. FTIR data suggests that neither low nor high silica content has an effect on the reactivity of acrylate functionalities during polymer formation. SEM micrographs reveal that variation in silica or polymer content does not produce any phase-separated structures. Instead, uniformly distributed nano-sized polymer–silica structures were obtained for all compositions. Our results suggest that a variety of combinations of mechanical and other properties (such as densities, surface areas, pore sizes, and pore volumes) can be produced through appropriate combination for diverse applications. All these findings provide convincing evidence that the variation of silica and/or polymer content can be used to fabricate aerogels with a variety of properties, which have the depth needed for use in laser-based 3D printing technology of simple or complex structures with nearly any dimensions.
Abstract The relationship between both monomer functionality and concentration and the mechanical... more Abstract The relationship between both monomer functionality and concentration and the mechanical properties of cross-linked aerogels was investigated. For this, alcogels were synthesized using a gelation solution containing an alkoxide (tetramethyl orthosilicate, TMOS) to form the oxide gel skeleton, trimethoxysilylpropyl methacrylate (MTMS) to attach a coupling acrylic group to the pore walls, an acrylic monomer, a photoinitiator (Eosin Y) and a tertiary amine acting as base catalyst for gelation and as polymerization co-initiator. The gelation solvent was the ethanol–water azeotrope mixture (4.4% water by volume). After gelation, alcogels were cross-linked by photopolymerization using green light and were dried using the ethanol–water azeotrope as a supercritical fluid. Densities, shrinkage, surface areas, pore sizes, moduli and specific energy absorptions of the resulting monoliths were measured and found to depend very strongly on MTMS and monomer concentration and, to a lesser extent, on monomer functionality. Optimization of the gelation solution composition allowed for the fabrication of aerogel composites with Young's modulus of 257 MPa and specific energy absorption of 19.4 J g −1 , which makes them possible candidates for ballistic protection applications.
In this work, a previously developed (White et al 2015 J. Mater. Chem. A 3 762) rapid synthesis a... more In this work, a previously developed (White et al 2015 J. Mater. Chem. A 3 762) rapid synthesis approach is used to fabricate native and cross-linked aerogel monoliths with customized geometries. This technique does not require solvent exchange, therefore fabrication times do not depend on part size. To prove this, parts with a smallest dimension of approximately 3.6 cm were fabricated within the same time scale as that of small cylinders with a diameter of 7 mm. In addition, monoliths with customized geometries exhibiting physical detail on the order of 1 mm were produced to demonstrate the versatility of this technique. Furthermore, hybrid materials consisting of native silica aerogel integrated with selected regions of polymer cross-linking were produced. The cross-linked regions allow for adhesion to other surfaces or labeling while the majority of the material retains the physical characteristics of a native silica aerogel. The physical and thermal properties of all aerogel components were examined. All aerogel materials produced in this work exhibited characteristics that were within the range of aerogel materials produced using more conventional methods. For native silica materials, this includes densities in the range of 0.03–0.116 g cm−3, surface areas between 342–799 m2 g−1, mode pore sizes in the range of 30–39 nm, and thermal conductivities in the range of 0.020–0.026 W m−1 K−1. For cross-linked aerogel materials, densities ranged between 0.154–0.340 g cm−3, surface areas were between 291–388 m2 g−1, mode pore sizes were in the range of 29–41 nm, and thermal conductivities were in range of 0.038–0.066 W m−1 K−1.
Abstract A method for rapid fabrication of polymer cross-linked silica aerogel through laser indu... more Abstract A method for rapid fabrication of polymer cross-linked silica aerogel through laser induced photogelation and the effect of pre-heating, irradiation conditions, and gelation solvent on the structural and mechanical properties of the resulting aerogel material is presented here. An ethanolic solution of an alkoxysilane (tetraorthosilicate, TEOS), a monomer (hexanedioldiacrylate, HDDA), a visible-light free-radical photoinitiator (Eosin Y) and a tertiary amine (as co-initiator and pH modifier), was prepared. The solution was irradiated with a laser beam, and the energy liberated by the polymerization reactions induced gelation in a matter of seconds. The alcogel was then dried into aerogel using the ethanol-water (or acetone-water) azeotrope mixture as a drying fluid. It was observed that pre-heated solutions gelled instantly and the resulting aerogels showed density, Young's modulus and surface area values comparable to those of aerogels produced through conventional methods. The solutions without pre-heating gelled relatively slowly and yielded composites with Young's modulus values about 3 times and surface areas about 1.5 times smaller than the pre-heated samples. The replacement of ethanol with acetone as a gelation solvent accelerated gelation; however, the composites shrank about 2 times more than samples prepared using ethanol and, consequently, had higher densities and moduli and decreased surface areas. The potential exists for mold-free and rapid fabrication of bulk or thin film aerogel structures using this method to open new avenues for their application in areas such as 3D printing.
Tumor-derived exosomes may provide biomarkers for cancer treatment. Using sputtering technology, ... more Tumor-derived exosomes may provide biomarkers for cancer treatment. Using sputtering technology, an affinity-based device to capture exosomes was developed using nanoporous substrate (NPG)-coated silicon microscopy. Immunology-based techniques detect and purify exosomes using gold coating with a specific antigen. Inverted fluorescent microscopy was used to detect target exosomes quantitatively utilizing fluorescent nanospheres as the label. We quantified the expression of CD63 surface protein markers on exosomes from conditioned culture media of breast cancer cells. The exosomes that targeted specific proteins with controls were statistically analyzed and compared to those that targeted non-specific proteins. Results from SEM showed that the exosomes were circular, between 30 and 150 nanometers in size. The porous gold substrates captured more exosomes than the nonporous substrates. Nitric acid treatments at different times resulted in a variety of pore sizes. Despite the increase i...
In the present study, a novel diamine 1,4-bis[4-(hydrazonomethyl)phenoxy]butane (4-BHPB) has been... more In the present study, a novel diamine 1,4-bis[4-(hydrazonomethyl)phenoxy]butane (4-BHPB) has been successfully synthesized by a facile method.
Several metal oxides, such as tungsten oxide (WO3), are considered superior sensing materials for... more Several metal oxides, such as tungsten oxide (WO3), are considered superior sensing materials for hydrogen sulfide (H2S) detection in the ambient environment. In this study, silver loaded tungsten oxide nanoparticles were prepared by microwave-assisted chemical route. Nanoparticle thin films were deposited on substrates with electrical electrodes to explore their gas sensing and electrical properties. The morphology, crystal structure, and chemical state were examined using x-ray diffraction (XRD), scanning electron mi-]] ]]
In this paper, we report oxidation time effect on highly porous silver oxide nanowires thin films... more In this paper, we report oxidation time effect on highly porous silver oxide nanowires thin films fabricated using ultrasonic spray pyrolysis and oxygen plasma etching method. The NW’s morphological, electrical, and optical properties were investigated under different plasma etching periods and the number of deposition cycles. The increase of plasma etching and oxidation time increases the surface roughness of the Ag NWs until it fused to form a porous thin film of silver oxide. AgNWs based thin films were characterized using X-ray diffraction, scanning electron microscope, transmission electron microscope, X-ray photoemission spectroscopy, and UV–Vis spectroscopy techniques. The obtained results indicate the formation of mixed mesoporous Ag2O and AgO NW thin films. The Ag2O phase of silver oxide appears after 300 s of oxidation under the same conditions, while the optical transparency of the thin film decreases as plasma etching time increases. The sheet resistance of the final fil...
ABSTRACT In this paper, we present a novel synthesis approach for preparation of Magnesium Hydrox... more ABSTRACT In this paper, we present a novel synthesis approach for preparation of Magnesium Hydroxide, Mg(OH)2, having nano-sheets morphologies that can find applications in plastic industry as flame-retardant and reinforcing material and can be used for conservation of paper based cultural heritage. The nanomaterials were successfully synthesized using novel microwave synthesis technique using Magnesium sulfates as precursor and Cetyltrimethylammonium bromide (CTAB) as dispersant. The nano-sheets were produced through a reaction of Magnesium sulfates with NaOH in a microwave chemical reactor, operated at a controlled power rating for specific time. A good yield of the precipitates, produced as a result of reaction, were isolated, washed, dried and were subjected to heat treatment at 300 oC to remove the organic dispersant. Characterization technique such as XRD, SEM, HR-TEM were used to elucidate the composition and structure of Mg(OH)2 nanomaterial. The data obtained from these techniques confirmed successful synthesis and nano-structure of Mg(OH)2. The BET surface area and nitrogen adsorption/desorption measurements of Mg(OH)2 nanoparticles showed a surface area of 80.27 m2/g. HRTEM analysis revealed the morphology of Mg(OH)2 to be composed of nano sheets with a unique packing structure that gives a highly porous nano structure to the material. The Mg(OH)2 particles with a size smaller than 5 nm were observed which, in our opinion, can be used for diverse applications.
ABSTRACT Thermal insulation is considered one of the main factors of reducing heat and energy con... more ABSTRACT Thermal insulation is considered one of the main factors of reducing heat and energy consumption in buildings. There are many insulation materials used to reduce energy consumption and heat loss in buildings, such as: cellulose, glass wool, rock wool, polystyrene, urethane foam.., etc. Unfortunately, most of these materials have problems with their durability, effectiveness and cost. Aerogels being ultra-light, highly porous and highly thermal insulating materials are being considered for applications as varied as thermal and sound insulation for aerospace applications, as absorbents for environmental remediation and as supports for catalysts [1-4]. However, the major problem with aerogels is their mechanically fragility that impeded their commercialization and limited their fabrication in the form of granules or panels of limited thickness. Aerogel production is a slow and tedious process. Wet gels, termed aquogels or alcogels depending on the solvent can be rapidly synthesized following well-established procedures [5,6] but drying is timeconsuming. Because of capillary forces the solvent cannot be evaporated without cracking and shrinking the monolith. We want to share very interesting results of a novel synthesis approach through which mechanically strong aerogels can be fabricated just in few hours instead of few days. The other novelties associated with our process is one pot synthesis for both native and cross-linked aerogels and no need for time consuming process of multiple solvent exchanges. This also significantly truncate large volume of fresh solvent required during the conventional synthesis process. The results are of particular importance, since they dramatically shorten fabrication times for monoliths with large sizes of native and, most importantly, of cross-linked aerogel. We have synthesized samples using base- and acid-catalyzed chemistries, varied alkoxide concentration and, for cross-linked aerogels, monomer concentration. Depending on alkoxide concentration, native oxide aerogels had densities between about 0.06 and 0.17 g.cm-3 and surface areas between about 300 and 500 m2.g-1. Figure 1 shows our synthesized Aerogels. Our group has been developing alternative fabrication methods which enable to produce custom parts which are made mechanically strong by reinforcing the regions of highest solicitation with a polymer. We have fabricated custom parts that may be used as insulation of selected parts of internal combustion engines, passive fire protection of structural elements in building, and lightweight footwear for extreme cold conditions. We also have developed cost-effective and scalable procedures for fabricating these custom- shaped aerogels.
ABSTRACT Thermal insulation is considered one of the main factors of reducing heat and energy con... more ABSTRACT Thermal insulation is considered one of the main factors of reducing heat and energy consumption in buildings. There are many insulation materials used to reduce energy consumption and heat loss in buildings, such as: cellulose, glass wool, rock wool, polystyrene, urethane foam.., etc. Unfortunately, most of these materials have problems with their durability, effectiveness and cost. Aerogels being ultra-light, highly porous and highly thermal insulating materials are being considered for applications as varied as thermal and sound insulation for aerospace applications, as absorbents for environmental remediation and as supports for catalysts [1-4]. However, the major problem with aerogels is their mechanically fragility that impeded their commercialization and limited their fabrication in the form of granules or panels of limited thickness. Aerogel production is a slow and tedious process. Wet gels, termed aquogels or alcogels depending on the solvent can be rapidly synthesized following well-established procedures [5,6] but drying is timeconsuming. Because of capillary forces the solvent cannot be evaporated without cracking and shrinking the monolith. We want to share very interesting results of a novel synthesis approach through which mechanically strong aerogels can be fabricated just in few hours instead of few days. The other novelties associated with our process is one pot synthesis for both native and cross-linked aerogels and no need for time consuming process of multiple solvent exchanges. This also significantly truncate large volume of fresh solvent required during the conventional synthesis process. The results are of particular importance, since they dramatically shorten fabrication times for monoliths with large sizes of native and, most importantly, of cross-linked aerogel. We have synthesized samples using base- and acid-catalyzed chemistries, varied alkoxide concentration and, for cross-linked aerogels, monomer concentration. Depending on alkoxide concentration, native oxide aerogels had densities between about 0.06 and 0.17 g.cm-3 and surface areas between about 300 and 500 m2.g-1. Figure 1 shows our synthesized Aerogels. Our group has been developing alternative fabrication methods which enable to produce custom parts which are made mechanically strong by reinforcing the regions of highest solicitation with a polymer. We have fabricated custom parts that may be used as insulation of selected parts of internal combustion engines, passive fire protection of structural elements in building, and lightweight footwear for extreme cold conditions. We also have developed cost-effective and scalable procedures for fabricating these custom- shaped aerogels.
Cigarettes et constituants de cigarettes, par exemple du tabac de remplissage et du papier a ciga... more Cigarettes et constituants de cigarettes, par exemple du tabac de remplissage et du papier a cigarette, et procede de fabrication de constituants de cigarettes comportant des fibrilles nanostructurees. Ces fibrilles nanostructurees, qui sont eventuellement formees et deposees in situ sur le tabac de remplissage et/ou le papier a cigarette par condensation controlee a vaporisation au laser ou par reaction chimique, sont aptes a servir d'oxydant pour la transformation du monoxyde de carbone en gaz carbonique et/ou de catalyseur pour la transformation du monoxyde de carbone en gaz carbonique. On a egalement prevu des cigarettes comportant du tabac de remplissage et du papier a cigarette, dans lesquelles les fibrilles nanostructurees sont deposees ou incorporer dans le tabac de remplissage et/ou le papier a cigarette.
In the present study, a novel diamine 1,4-bis[4-(hydrazonomethyl)phenoxy]butane (4-BHPB) has been... more In the present study, a novel diamine 1,4-bis[4-(hydrazonomethyl)phenoxy]butane (4-BHPB) has been successfully synthesized by a facile method. 4-BHPB was reacted with pyromellitic dianhydride (PMDA) to derive a novel polyimide (PI). Highly compatibilized PI–SiO2 nanocomposites were tailored using synthesized PI matrix and modified silica nanoparticles. The compatibility between organic–inorganic (O–I) components was remarkably improved by charge transfer complex (CTC) formed between PI chains and modified silica nanoparticles. PI chains have electron donor and acceptor groups (diamine and dianhydride portion, respectively). These groups were generated in silica nanoparticles by the organic modification through 2,6-bis(3-(triethoxysilyl)propyl)pyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone (M-SiO2), which in turn, was prepared reacting PMDA with 3-aminopropyltriethoxysilane. Sol–gel method was used for in situ synthesis of silica nanoparticles from a mixture of M-SiO2 and TEOS. The ...
1,2 Farman Ali, Shaukat Saeed*, Khaled M. Saoud and Syed Sakhawat Shah 1 Department of Metallurgy... more 1,2 Farman Ali, Shaukat Saeed*, Khaled M. Saoud and Syed Sakhawat Shah 1 Department of Metallurgy and Materials Engineering (DMME), Pakistan Institute of Engineering and Applied Sciences (PIEAS), PO Nilore, Islamabad-45650, Pakistan. 2 Department of Chemistry, Hazara University Mansehra, 21120, Pakistan. Liberal Arts and Science Program, Virginia Commonwealth University in Qatar, Doha, Qatar. [email protected], [email protected]*
Self-sustaining and hysteresis behavior of low-temperature CO oxidation on mesoporous Pd/SiO2 aer... more Self-sustaining and hysteresis behavior of low-temperature CO oxidation on mesoporous Pd/SiO2 aerogel s catalyst under dynamics conditions
Cross-linked silica aerogels are promising, strong, lightweight materials for photolithographic a... more Cross-linked silica aerogels are promising, strong, lightweight materials for photolithographic applications. The work presented here details the preparation of ultra-lightweight aerogel materials with tailored properties through the appropriate combination of silica and methacrylate polymer using laser-induced rapid photogelation fabrication technique. For fabrication, an ethanolic solution of hexanediol diacrylate, tetraorthosilicate, Eosin Y and a tertiary amine was prepared. The amounts of reactants were varied to prepare different compositions of aerogel monoliths. The solution was irradiated with a green beam from a low power laser source. The samples, after drying in supercritical ethanol, were characterized using FTIR, BET, SEM, TGA, and a mechanical testing instrument. FTIR data suggests that neither low nor high silica content has an effect on the reactivity of acrylate functionalities during polymer formation. SEM micrographs reveal that variation in silica or polymer content does not produce any phase-separated structures. Instead, uniformly distributed nano-sized polymer–silica structures were obtained for all compositions. Our results suggest that a variety of combinations of mechanical and other properties (such as densities, surface areas, pore sizes, and pore volumes) can be produced through appropriate combination for diverse applications. All these findings provide convincing evidence that the variation of silica and/or polymer content can be used to fabricate aerogels with a variety of properties, which have the depth needed for use in laser-based 3D printing technology of simple or complex structures with nearly any dimensions.
Abstract The relationship between both monomer functionality and concentration and the mechanical... more Abstract The relationship between both monomer functionality and concentration and the mechanical properties of cross-linked aerogels was investigated. For this, alcogels were synthesized using a gelation solution containing an alkoxide (tetramethyl orthosilicate, TMOS) to form the oxide gel skeleton, trimethoxysilylpropyl methacrylate (MTMS) to attach a coupling acrylic group to the pore walls, an acrylic monomer, a photoinitiator (Eosin Y) and a tertiary amine acting as base catalyst for gelation and as polymerization co-initiator. The gelation solvent was the ethanol–water azeotrope mixture (4.4% water by volume). After gelation, alcogels were cross-linked by photopolymerization using green light and were dried using the ethanol–water azeotrope as a supercritical fluid. Densities, shrinkage, surface areas, pore sizes, moduli and specific energy absorptions of the resulting monoliths were measured and found to depend very strongly on MTMS and monomer concentration and, to a lesser extent, on monomer functionality. Optimization of the gelation solution composition allowed for the fabrication of aerogel composites with Young's modulus of 257 MPa and specific energy absorption of 19.4 J g −1 , which makes them possible candidates for ballistic protection applications.
In this work, a previously developed (White et al 2015 J. Mater. Chem. A 3 762) rapid synthesis a... more In this work, a previously developed (White et al 2015 J. Mater. Chem. A 3 762) rapid synthesis approach is used to fabricate native and cross-linked aerogel monoliths with customized geometries. This technique does not require solvent exchange, therefore fabrication times do not depend on part size. To prove this, parts with a smallest dimension of approximately 3.6 cm were fabricated within the same time scale as that of small cylinders with a diameter of 7 mm. In addition, monoliths with customized geometries exhibiting physical detail on the order of 1 mm were produced to demonstrate the versatility of this technique. Furthermore, hybrid materials consisting of native silica aerogel integrated with selected regions of polymer cross-linking were produced. The cross-linked regions allow for adhesion to other surfaces or labeling while the majority of the material retains the physical characteristics of a native silica aerogel. The physical and thermal properties of all aerogel components were examined. All aerogel materials produced in this work exhibited characteristics that were within the range of aerogel materials produced using more conventional methods. For native silica materials, this includes densities in the range of 0.03–0.116 g cm−3, surface areas between 342–799 m2 g−1, mode pore sizes in the range of 30–39 nm, and thermal conductivities in the range of 0.020–0.026 W m−1 K−1. For cross-linked aerogel materials, densities ranged between 0.154–0.340 g cm−3, surface areas were between 291–388 m2 g−1, mode pore sizes were in the range of 29–41 nm, and thermal conductivities were in range of 0.038–0.066 W m−1 K−1.
Abstract A method for rapid fabrication of polymer cross-linked silica aerogel through laser indu... more Abstract A method for rapid fabrication of polymer cross-linked silica aerogel through laser induced photogelation and the effect of pre-heating, irradiation conditions, and gelation solvent on the structural and mechanical properties of the resulting aerogel material is presented here. An ethanolic solution of an alkoxysilane (tetraorthosilicate, TEOS), a monomer (hexanedioldiacrylate, HDDA), a visible-light free-radical photoinitiator (Eosin Y) and a tertiary amine (as co-initiator and pH modifier), was prepared. The solution was irradiated with a laser beam, and the energy liberated by the polymerization reactions induced gelation in a matter of seconds. The alcogel was then dried into aerogel using the ethanol-water (or acetone-water) azeotrope mixture as a drying fluid. It was observed that pre-heated solutions gelled instantly and the resulting aerogels showed density, Young's modulus and surface area values comparable to those of aerogels produced through conventional methods. The solutions without pre-heating gelled relatively slowly and yielded composites with Young's modulus values about 3 times and surface areas about 1.5 times smaller than the pre-heated samples. The replacement of ethanol with acetone as a gelation solvent accelerated gelation; however, the composites shrank about 2 times more than samples prepared using ethanol and, consequently, had higher densities and moduli and decreased surface areas. The potential exists for mold-free and rapid fabrication of bulk or thin film aerogel structures using this method to open new avenues for their application in areas such as 3D printing.
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Papers by Khaled Saoud