Ehsan Marzbanrad

Nanocasting Synthesis of Ultrafine WO3 Nanoparticles for Gas Sensing Applications

Ultrafine WO3 nanoparticles were synthesized by nanocasting route, using mesoporous SiO2 as a template. BET measurements showed a specific surface area of 700 m 2/gr for synthesized SiO2, while after impregnation and template removal, this area was reduced to 43 m 2/gr for WO3 nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5 nm possessing a monoclinic structure, which is the favorite crystal structure for gas sensing applications. Gas sensor was fabricated by deposition of WO3 nanoparticles between electrodes via low frequency AC electrophoretic deposition. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO2 at 250°C and 300°C.

Nanocasting Synthesis of Ultrafine WO 3 Nanoparticles for Gas Sensing Applications

Ultrafine WO3 nanoparticles were synthesized by nanocasting route, using mesoporous SiO2 as a template. BET measurements showed a specific surface area of 700 m 2/gr for synthesized SiO2, while after impregnation and template removal, this area was reduced to 43 m 2/gr for WO3 nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5 nm possessing a monoclinic structure, which is the favorite crystal structure for gas sensing applications. Gas sensor was fabricated by deposition of WO3 nanoparticles between electrodes via low frequency AC electrophoretic deposition. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO2 at 250°C and 300°C.

Deposition of Multiwall Carbon Nanotubes Using Low Frequency Alternating Electrophoretic Deposition

In this paper, electrophoretic deposition of multiwall carbon nanotubes (MWNTs) using low frequency (0.01-1000 Hz) AC electric fields, is reported. The effect of depositing parameters such as frequency and waveform on deposit yield is investigated. Results show that the deposit yield decreases with frequency. The rectangular waveform yields more deposit yield than sinusoidal and triangular waveforms. The deposition pattern is also different in AC and DC electric fields. This technique may be used for deposition of MWNTs thick films.

Highly-stable silver nanobelts joined via diffusion-free attachment.

Silver nanobelts are demonstrated here to undergo inter-particle joining at relatively low temperatures of less than 180 °C. For surface-coated networks of nanobelts this joining reduced the network sheet resistance by 95%. The joining mechanism appears to be non-diffusional oriented attachment, caused by the thermal reactivation of the halted oriented attachment mechanism that occurred originally at room temperature during the rapid nanobelt synthesis. This self-assembly mechanism was explored by in situ electrical and calorimetric experiments, and supported by electron microscopy. Unlike pentagonal silver nanowires, silver nanobelts do not rely on diffusional instability to achieve workably low joining temperatures. The oriented attachment displayed by nanobelts represents a new approach to achieving valuable reductions in network resistance, disentangled from the instability and diffusion-driven failure by nanoparticle degradation displayed by competing silver nanoparticles.

Porous silver nanosheets: a novel sensing material for nanoscale and microscale airflow sensors

Fabrication of nanoscale and microscale machines and devices is one of the goals of nanotechnology. For this purpose, different materials, methods, and devices should be developed. Among them, various types of miniaturized sensors are required to build the nanoscale and microscale systems. In this research, we introduce a new nanoscale sensing material, silver nanosheets, for applications such as nanoscale and microscale gas flow sensors. The silver nanosheets were synthesized through the reduction of silver ions by ascorbic acid in the presence of poly(methacrylic acid) as a capping agent, followed by the growth of silver in the shape of hexagonal and triangular nanoplates, and self-assembly and nanojoining of these structural blocks. At the end of this process, the synthesized nanosheets were floated on the solution. Then, their electrical and thermal stability was demonstrated at 120 °C, and their atmospheric corrosion resistance was clarified at the same temperature range by thermogravimetric analysis. We employed the silver nanosheets in fabricating airflow sensors by scooping out the nanosheets by means of a sensor substrate, drying them at room temperature, and then annealing them at 300 °C for one hour. The fabricated sensors were tested for their ability to measure airflow in the range of 1 to 5 ml min(-1), which resulted in a linear response to the airflow with a response and recovery time around 2 s. Moreover, continuous dynamic testing demonstrated that the response of the sensors was stable and hence the sensors can be used for a long time without detectable drift in their response.

Aging Behavior of Yttria Stabilized Zirconia (YSZ) in Non Aqueous Suspensions for Electrophoretic Deposition Application

In this research aging behaviors of yttria stabilized zirconia (YSZ) in non aqueous suspensions, namely ethanol, isopropanol, n-propanol, acetylacetone and the mixture of ethanol-acetylacetone were investigated. For this purpose, electrical conductivity, electrophoretic mobility and suspension stability during aging time (6 to 7 days) were evaluated. Except for the ethanol-acetyl acetone mixture, each suspension contained 0 to 0.8 g/L iodine. It was revealed that, the alcoholic suspensions indicated lower conductivity in comparison with acetylacetone suspensions. However, acetylacetone suspension showed lower conductivity variation with time. Although iodine could improve the electrophoretic mobility of ethanol and acetylacetone suspensions, it had little effect on electrophoretic mobility of isopropanol and n-propanol suspensions. Also, it was indicated that iodine as a dispersant was not helpful for alcoholic suspensions stability. It was concluded that the mixture of acetylacetone-ethanol suspension was the best candidate in this study for electrophoretic deposition of YSZ, owing to its little behavior variation with the aging time, low conductivity and high electrophoretic mobility. High quality crack-free layers were electrophoretically deposited from this suspension on the substrate by applying 50 V/cm electrical field.

Mathematical modeling for predicting betamethasone profile and burst release from in situ forming systems based on PLGA

This paper examines the application of mathematical modeling to a novel drug delivery system using artificial neural networks. For this purpose, a Feed-Forward back propagation network was trained by two different concepts and the behavior of this drug delivery system was analyzed based on the simulated results. The network also successfully determined the most accurate release profiles under specific formulation parameters. The simulated results showed a high correlation with the real data in this study. Furthermore, a new method was proposed in order to predict the burst release point in Poly Lactic-co-Glycolic Acid (PLGA) based drug delivery systems. This paper reveals that the mathematical modeling of novel drug delivery systems not only significantly decreases time and cost, but also facilitates the design of new pharmaceutical formulations.

AC Electrophoresis, a New Technique for Deposition of Ceramic Nanoparticles; Introduction, Application and Mechanism

Deposition of ceramic nanoparticles (dispersed in non-aqueous suspension) on in-plane electrodes and under the influence of AC electric fields in the frequency range of 0.01 Hz - 10 kHz is investigated. Analysis of the particle response to the applied field is a difficult task due to the mutual effect of electric and hydrodynamic forces which are present in the system. In this work, however, we show the possibility of dividing the frequency range into four domains with four distinct governing mechanisms. Possible mechanisms are suggested and dominant forces are determined for each domain. In situ optical microscopy observations are used for visualization of nanoparticles´ movement dispersed in liquid medium. These observations show that applying AC electrophoresis at frequencies below 10 kHz is an effective way for manipulating ceramic nanoparticles and device fabrication.

SYNTHESIS AND MANIPULATION OF WO3 NANO PARTICLES FOR GAS SENSING APPLICATIONS

Ultra fine WO3 nanoparticles were synthesized by nanocasting route, using mesoporous SiO2 as a template. BET measurements showed a specific surface area of 700m2/gr for synthesized SiO2 while after impregnation and template removal, this area was reduced to 43m2/gr for WO3 nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5nm possessing a monoclinic structure which is the favorite crystal structure for gas sensing applications. Alternative electric field was applied to align synthesized WO3 nanoparticles between electrodes. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO2 at 250°C.

Nanocasting Synthesis of Ultrafine WO3

Ultrafine WO3 nanoparticles were synthesized by nanocasting route, using mesoporous SiO2 as a template. BET measurements showed a specific surface area of 700 m 2/gr for synthesized SiO2, while after impregnation and template removal, this area was reduced to 43 m 2/gr for WO3 nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5 nm possessing a monoclinic structure, which is the favorite crystal structure for gas sensing applications. Gas sensor was fabricated by deposition of WO3 nanoparticles between electrodes via low frequency AC electrophoretic deposition. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO2 at 250°C and 300°C.