Acetone Sensors Based on In₂O₃—Co₃O₄ Composite Nanoparticles

Mirzaei, Ali,Park, Sunghoon,Kheel, Hyejoon,Sun, Gun-Joo,Ko, Taegyung,Lee, Sangmin,Lee, Chongmu American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.6

<P>Pure In2O3 and In2O3/Co3O4 composite nanoparticles were synthesized by a hydrothermal process using indium acetate and cobalt acetate as precursors. The In2O3/Co3O4 composite nanoparticles provided enhanced sensing performance. In particular, the responses of the pure In2O3 and In2O3/Co3O4 composite nanoparticle sensors to 200-ppm acetone at 250 degrees C were 5.55 and 15.54, respectively. The response and recovery times of the pure In2O3 sensors to 200-ppm acetone at 250 degrees C were 7 and 30 s, respectively, whereas those of the In2O3/Co3O4 composite nanoparticle sensor were 2.5 and 18 s, respectively. The underlying mechanism for the improved sensing characteristics of the In2O3/Co3O4 sensor were also discussed.</P>

Modeling and operating conditions optimization of Fischer–Tropsch synthesis in a fixed-bed reactor

Ali Akbar Mirzaei,Bahman Shirzadi,Hossein Atashi,Mohsen Mansouri 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.4

The effect of a range of operation variables such as pressure, low temperature and H2/CO molar feed ration the catalytic performance of 80%Co/20%Ni/30 wt% La2O3/1 wt% Cs catalyst was investigated. It was found that the optimum operating conditions is a H2/CO = 2/1 molar feed ratio at 260 8C temperature and 2 bar pressure. Reaction rate equations were derived on the basis of the Langmuir–Hinshelwood–Hougen–Watson (LHHW) type models for the Fischer–Tropsch reactions. The activation energy obtained was 59.69 kJ/mol for optimal kinetic model.

Kinetic study of CO hydrogenation over co-precipitated iron–nickel catalyst

Ali A. Mirzaei,Rouhoullah M. Kiai,Hossein Atashi,Maryam Arsalanfar,Sara Shahriari 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.4

The kinetic of the Fischer–Tropsch synthesis over a Fe–Ni/Al2O3 catalyst was investigated in a fixed bed micro reactor. Experimental conditions were varied as follow: reaction pressure 2–10 bar, H2/CO feed ratio of 2/1 and space velocity of 96–450 cm3(STP)/h/gramcatalyst at the temperature range 523–573 K. On the basis of carbide-enol mechanism and Langmuir–Hinshelwood–Hougen–Watson (LHHW) type rate equations, seventeen kinetic expressions for CO consumption were tested and interaction between adsorption HCO and dissociated adsorption hydrogen as the controlling step gave the most plausible kinetic model. The activation energy was 46.5 kJ/mole for optimal kinetic model.

Surprising Synthesis of Nanodiamond from Single-Walled Carbon Nanotubes by the Spark Plasma Sintering Process

Ali Mirzaei,Heon Ham,나한길,Yong Jung Kwon,강성용,최명식,방재훈,박노형,강인필,김현우 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.6

Nanodiamond (ND) was successfully synthesized usingsingle-walled carbon nanotubes (SWCNTs) as a pure solidcarbon source by means of a spark plasma sintering process. Raman spectra and X-ray diffraction patterns revealed thegeneration of the cubic diamond phase by means of the SPSprocess. Lattice-resolved TEM images confirmed thatdiamond nanoparticles with a diameter of about ~10 nmexisted in the products. The NDs were generated mainlythrough the gas-phase nucleation of carbon atoms evaporatedfrom the SWCNTs.

Fe2O3/Co3O4 composite nanoparticle ethanol sensor

Ali Mirzaei,Sunghoon Park,Gun-Joo Sun,Hyejoon Kheel,Chongmu Lee,Sangmin Lee 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.3

In this study Fe2O3/Co3O4 nanocomposites were synthesized by using a simple hydrothermal route. The X-ray diffraction analysis results showed that the synthesized powders were pure and nanocrystalline in nature. Moreover, scanning electron microscopy revealed that Fe2O3 nanoparticles had spherical shapes while Co3O4 particles had a rod-like morphology. The ethanol sensing properties of Fe2O3/Co3O4 nanocomposites were examined and compared with those of pristine Fe2O3 nanoparticles. The gas sensing properties of Fe2O3/Co3O4 nanocomposites were shown to be superior to those of pristine Fe2O3 nanoparticles and for all concentrations of ethanol, the response of the nanocomposite sensor was shown to be higher than that of the pristine Fe2O3 nanoparticle sensor. In detail, the response of the Fe2O3/Co3O4 nanocomposite sensor to 200 ppm of ethanol at 300 C was about 3 times higher than that of pristine sensor. Also, in general, the response and recovery times of the Fe2O3/Co3O4 nanocomposite sensor were shorter than those of the pristine one. The improved sensing characteristics of the Fe2O3/Co3O4 sensor were attributed to a combination of several effects: the formation of a potential barrier at the Fe2O3-Co3O4 interface, the enhanced modulation of the conduction channel width accompanying the adsorption and desorption of ethanol gas, the catalytic activity of Co3O4 for the oxidation of ethanol, the stronger oxygen adsorption of p-type Co3O4, and the formation of preferential adsorption sites.

Hydrogen sensing properties and mechanism of NiO-Nb₂O₅ composite nanoparticle-based electrical gas sensors

Mirzaei, Ali,Sun, Gun-Joo,Lee, Jae Kyung,Lee, Chongmu,Choi, Seungbok,Kim, Hyoun Woo Elsevier 2017 Ceramics international Vol.43 No.6

<P><B>Abstract</B></P> <P>A simple hydrothermal method was used to prepare NiO-Nb<SUB>2</SUB>O<SUB>5</SUB> composite nanoparticle electrical sensors for the detection of hydrogen (H<SUB>2</SUB>) at room temperature. To investigate the morphology and crystal structure of the synthesized powders, the synthesized nanoparticles were characterized by scanning electron microscopy and X-ray diffraction. The NiO-Nb<SUB>2</SUB>O<SUB>5</SUB> composite nanoparticle sensor showed stronger and faster response to H<SUB>2</SUB> than the pristine Nb<SUB>2</SUB>O<SUB>5</SUB> one at room temperature. Only weak responses were observed to carbon monoxide, methane and ethanol, indicating that the NiO-Nb<SUB>2</SUB>O<SUB>5</SUB> composite nanoparticle sensor could be a potential candidate as a practical gas detector. In this study, the H<SUB>2</SUB> sensing properties and mechanism of NiO-Nb<SUB>2</SUB>O<SUB>5</SUB> composite nanoparticle-based electrical gas sensors are discussed in detail.</P>

How shell thickness can affect the gas sensing properties of nanostructured materials: Survey of literature

Mirzaei, Ali,Kim, Jae-Hun,Kim, Hyoun Woo,Kim, Sang Sub Elsevier Sequoia 2018 Sensors and actuators. B Chemical Vol.258 No.-

<P><B>Abstract</B></P> <P>High-performance gas sensors are needed to improve safety in daily life. Even though the gas sensing performance of new nanostructured metal oxides has improved significantly, some aspects of these novel nanomaterials have not been fully explored. Core-shell (C-S) and hollow shell nanostructures are two types of advanced materials for gas sensing applications. Their popularity is mainly due to the synergetic effects of the core and shell in C-S nanostructures, the high surface areas of both C-S and hollow nanostructures, and the possibility of tuning the shell thickness within the range of the Debye length for such nanostructures. In addition to the type of sensing material, morphology, sensing temperature, and porosity, shell thickness is one of the most important design parameters. Unfortunately, less attention has been paid to the effect of shell thickness on the gas sensing properties. Herein, we demonstrate that the thickness has an undeniable role in the gas sensing response of the resulting material. In this review, we present the first overview of this aspect of sensing materials. By referring to related works, we show how shell thickness can affect the sensing properties of both C-S and hollow nanostructures. Researchers in this field will be able to fabricate more sensitive gas sensors for real applications by better understanding the effect of shell thickness on the gas sensing properties of C-S and hollow nanostructured materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Applications of core-shell nanostructures in gas sensors are discussed. </LI> <LI> Mechanisms of gas sensing in core-shell nanostructures are discussed. </LI> <LI> Effect of shell thickness is comprehensively discussed. </LI> </UL> </P>

Fabrication and gas sensing properties of vertically aligned Si nanowires

Mirzaei, Ali,Kang, Sung Yong,Choi, Sun-Woo,Kwon, Yong Jung,Choi, Myung Sik,Bang, Jae Hoon,Kim, Sang Sub,Kim, Hyoun Woo Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.427 No.2

<P><B>Abstract</B></P> <P>In this study, a peculiar configuration for a gas sensor consisting of vertically aligned silicon nanowires (VA-Si NWs) synthesized by metal-assisted chemical etching (MACE) is reported. Si NWs were prepared via a facile MACE method and subsequent thermal annealing. Etching was performed by generation of silver nanoparticles (Ag NPs) and subsequent etching in HF/H<SUB>2</SUB>O<SUB>2</SUB> aqueous solution; the growth conditions were optimized by changing the process parameters. Highly vertically oriented arrays of Si NWs with a straight-line morphology were obtained, and a top–top electrode configuration was applied. The VA-Si NW gas sensor showed good sensing performance, and the VA-Si NWs exhibited a remarkable response (<I>R</I> <SUB>g</SUB>/<I>R</I> <SUB>a</SUB> =11.5∼17.1) to H<SUB>2</SUB> gas (10–50ppm) at 100°C which was the optimal working temperature. The formation mechanism and gas sensing mechanism of VA-Si NWs are described. The obtained results can suggest new approaches to making inexpensive, versatile, and portable sensors based on Si NWs having a novel top–top electrode structure that are fully compatible with well-developed Si technologies.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel configuration for a gas sensor consisting of vertically aligned silicon nanowires synthesized by metal-assisted chemical etching. </LI> <LI> Highly vertically oriented arrays of Si NWs with a straight-line morphology were obtained. </LI> <LI> Vertically aligned silicon nanowires exhibited a remarkable response (<I>R</I> <SUB>g</SUB>/<I>R</I> <SUB>a</SUB> =11.5∼17.1) to H<SUB>2</SUB> gas (10–50ppm) at the optimum working temperature (100°C). </LI> </UL> </P>

CO gas sensing properties of In₄Sn₃O₁₂ and TeO₂ composite nanoparticle sensors

Mirzaei, Ali,Park, Sunghoon,Sun, Gun-Joo,Kheel, Hyejoon,Lee, Chongmu Elsevier 2016 Journal of hazardous materials Vol.305 No.-

<P><B>Abstract</B></P> <P>A simple hydrothermal route was used to synthesize In<SUB>4</SUB>Sn<SUB>3</SUB>O<SUB>12</SUB> nanoparticles and In<SUB>4</SUB>Sn<SUB>3</SUB>O<SUB>12</SUB>–TeO<SUB>2</SUB> composite nanoparticles, with In(C<SUB>2</SUB>H<SUB>3</SUB>O<SUB>2</SUB>)<SUB>3</SUB>, SnCl<SUB>4</SUB>, and TeCl<SUB>4</SUB> as the starting materials. The structure and morphology of the synthesized nanoparticles were examined by X-ray diffraction and scanning electron microscopy (SEM), respectively. The gas-sensing properties of the pure and composite nanoparticles toward CO gas were examined at different concentrations (5–100ppm) of CO gas at different temperatures (100–300°C). SEM observation revealed that the composite nanoparticles had a uniform shape and size. The sensor based on the In<SUB>4</SUB>Sn<SUB>3</SUB>O<SUB>12</SUB>–TeO<SUB>2</SUB> composite nanoparticles showed stronger response to CO than its pure In<SUB>4</SUB>Sn<SUB>3</SUB>O<SUB>12</SUB> counterpart. The response of the In<SUB>4</SUB>Sn<SUB>3</SUB>O<SUB>12</SUB>–TeO<SUB>2</SUB> composite-nanoparticle sensor to 100ppm of CO at 200°C was 10.21, whereas the maximum response of the In<SUB>4</SUB>Sn<SUB>3</SUB>O<SUB>12</SUB> nanoparticle sensor was 2.78 under the same conditions. Furthermore, the response time of the composite sensor was 19.73s under these conditions, which is less than one-third of that of the In<SUB>4</SUB>Sn<SUB>3</SUB>O<SUB>12</SUB> sensor. The improved sensing performance of the In<SUB>4</SUB>Sn<SUB>3</SUB>O<SUB>12</SUB>–TeO<SUB>2</SUB> nanocomposite sensor is attributed to the enhanced modulation of the potential barrier height at the In<SUB>4</SUB>Sn<SUB>3</SUB>O<SUB>12</SUB>–TeO<SUB>2</SUB> interface, the stronger oxygen adsorption of p-type TeO<SUB>2</SUB>, and the formation of preferential adsorption sites.</P> <P><B>Highlights</B></P> <P> <UL> <LI> In4Sn3O12–TeO2 composite nanoparticles were synthesized via a facile hydrothermal route. </LI> <LI> The response of the In4Sn3O12–TeO2 composite sensor to CO was stronger than the pristine In4Sn3O12 sensor. </LI> <LI> The response of the In4Sn3O12–TeO2 composite sensor to CO was faster than the pristine In4Sn3O12 sensor. </LI> <LI> The improved sensing performance of the In4Sn3O12–TeO2 nanocomposite sensor is discussed in detail. </LI> <LI> The In4Sn3O12-based nanoparticle sensors showed selectivity to CO over NH3, HCHO and H2. </LI> </UL> </P>

Effect of Noble Metals on Hydrogen Sensing Properties of Metal Oxide-based Gas Sensors

Ali Mirzaei,Jae Hoon Bang,김상섭,김현우 한국센서학회 2020 센서학회지 Vol.29 No.6

As a green and abundant source of energy, H2 has attracted the attention of researchers for use in different applications. Nevertheless, it is highly flammable, and because of its significantly small size, extreme attention is needed to detect its leakage. In this review, we discuss different effects of noble metals on the H2 gas response and performance of metal oxide-based gas sensors. In this regard, we discuss the effects of noble metals, in combination with metal oxides, on H2 gas detection. The catalytic activity towards H2 gas and the formation of heterojunctions with metal oxides are the main contributions of noble metals to the sensing improvement of H2 gas sensors. Furthermore, in the special case of Pd and somewhat Pt, the formation of PdHx and PtHx also affects the H2 sensing performance. This review paper provides useful information for researchers working in the field of H2 gas detection.