scholarly journals Resistance-Capacitance Gas Sensor Based on Fractal Geometry

Chemosensors ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 31 ◽  
Author(s):  
Taicong Yang ◽  
Fengchun Tian ◽  
James A. Covington ◽  
Feng Xu ◽  
Yi Xu ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Gas Sensor ◽  
Fractal Geometry ◽  
Geometrical Structure ◽  
Gas Sensing ◽  
Superior Performance ◽  
Electrode Structure ◽  
Geometrical Structures ◽  
Surface Areas ◽  
Sensor Resistance

An important component of any chemiresistive gas sensor is the way in which the resistance of the sensing film is interrogated. The geometrical structure of an electrode can enhance the performance of a gas-sensing device and in particular the performance of sensing films with large surface areas, such as carbon nanotubes. In this study, we investigated the influence of geometrical structure on the performance of gas sensors, combining the characteristics of carbon nanotubes with a novel gas sensor electrode structure based on fractal geometry. The fabricated sensors were tested with exposure to nitric oxide, measuring both the sensor resistance and capacitance (RC) of the sensor responses. Experimental results showed that the sensors with fractal electrode structures had a superior performance over sensors with traditional geometrical structures. Moreover, the RC characteristics of these fractal sensors could be further improved by using different test frequencies that could aid in the identification and quantification of a target gas.

scholarly journals Optimizing electrode structure of carbon nanotube gas sensors for sensitivity improvement based on electric field enhancement effect of fractal geometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Taicong Yang
Keyword(s):  
Carbon Nanotubes ◽  
Electric Field ◽  
Gas Sensor ◽  
Fractal Geometry ◽  
Gas Sensing ◽  
Hot Spot ◽  
Rapid Development ◽  
Enhancement Effect ◽  
Electrode Structure ◽  
Geometrical Structures

AbstractWith the rapid development of carbon nanotubes gas sensor, the sensitivity of the sensing response is becoming more and more demanding. Different from the traditional studies on gas-sensitive materials, this paper combines the microscopic dimensional effects and physical properties of fractal geometry theory from the structure and morphology of sensor devices. The electrode structures of carbon nanotubes gas sensor is designed and optimized by Hilbert–Piano curve. Simulation experiments demonstrate that the electric field intensity and hot spot distribution of the fractal electrode are superior to those of the traditional interdigital electrode. Moreover, a novel chemiresistive gas sensor is fabricated combining the characteristics of carbon nanotubes and fractal geometry, and a test with exposure to nitric oxide showed that the sensors with fractal electrode structures improved the gas sensing sensitivity over sensors with traditional geometrical structures. It provides a new idea for the exploration of gas sensing technology.

scholarly journals Transfer Printing Technology as a Straightforward Method to Fabricate Chemical Sensors Based on Tin Dioxide Nanowires

Sensors ◽  
2019 ◽  
Vol 19 (14) ◽  
pp. 3049
Author(s):  
Florentyna Sosada-Ludwikowska ◽  
Robert Wimmer-Teubenbacher ◽  
Martin Sagmeister ◽  
Anton Köck
Keyword(s):  
Gas Sensor ◽  
Tin Dioxide ◽  
Gas Sensing ◽  
Transfer Printing ◽  
Electrode Structure ◽  
Step Method ◽  
Printing Technology ◽  
Straightforward Method ◽  
Spray Pyrolysis Deposition ◽  
Sensor Devices

Metal oxide multi-nanowire-based chemical gas sensors were manufactured by a fast and simple transfer printing technology. A two-step method employing spray pyrolysis deposition and a thermal annealing process was used for SnO 2 nanowires fabrication. A polydimethylsiloxane stamp was used to transfer the SnO 2 nanowires on two different gas sensing devices—Si-based substrates and microhotplate-based platform chips. Both contained a metallic inter-digital electrode structure (IDES), on which the SnO 2 nanowires were transferred for realization of multi-NW gas sensor devices. The gas sensor devices show a very high response towards H 2 S down to the 10 ppb range. Furthermore, a good response towards CO has been achieved, where in particular the microhotplate-based devices exhibit almost no cross sensitivity to humidity.

scholarly journals Novel 3-Dimensional Cotton-Like Graphenated-Carbon Nanotubes Synthesized via Floating Catalyst Chemical Vapour Deposition Method for Potential Gas-Sensing Applications

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Ismayadi Ismail ◽  
Md Shuhazlly Mamat ◽  
Noor Lyana Adnan ◽  
Zainab Yunusa ◽  
Intan Helina Hasan
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Gas Sensor ◽  
Chemical Vapour Deposition ◽  
Vapour Deposition ◽  
Gas Sensing ◽  
Chemical Vapour ◽  
Injection Rate ◽  
Sensing Applications ◽  
Graphenated Carbon Nanotubes

We reported the synthesis of graphenated-carbon nanotubes (G-CNTs) using a floating catalyst chemical vapour deposition (FCCVD) method and formed a bulk-cotton-like structure. The objectives of this work were to study the effect of the injection rate parameter of the carbon source on the formation of G-CNTs and CNTs and later to test them as an ammonia gas sensor. Ethanol, thiophene, and ferrocene were mixed and injected into FCCVD at 1150°C. The as-synthesized samples were then characterized using FESEM, HRTEM, TGA, Raman spectroscopy, XPS, and electrical conductivity measurement. We found that the injection rate of 5 ml/h was suitable for the formation of G-CNTs and a higher injection rate resulted in the formation of CNTs. Our measurement showed that the electrical conductivity response of G-CNTs was higher compared to that of CNTs. The gas-sensing performance of the gas sensor made of G-CNT materials also showed good response compared to that of CNTs. This experimental work paved the way for how we can selectively synthesize CNTs and G-CNTs via the FCCVD method, and G-CNTs have proven to be a better material for gas sensors.

scholarly journals Gas Sensing Properties of High-Purity Semiconducting Single-Walled Carbon Nanotubes for NH3, H2, and NO

2021 ◽  
Author(s):  
Akihiro Tsuruta ◽  
Takafumi Akamatsu ◽  
Kojiro Naito ◽  
Takayoshi Hirai ◽  
Seiichiro Murase ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Gas Sensor ◽  
High Purity ◽  
Gas Sensing ◽  
Single Walled Carbon Nanotubes ◽  
Oxide Semiconductor ◽  
Sensing Properties ◽  
Single Walled Carbon ◽  
Gas Sensing Properties ◽  
Walled Carbon Nanotubes

Abstract Gas sensors are advantageous as they can be applied in various fields. The metal-oxide semiconductor gas sensor is the most widely used gas sensor. In this study, the gas-sensing properties of high-purity semiconducting single-walled carbon nanotubes (SWCNTs), which behave as p-type semiconductors, are analyzed at temperatures of 50, 100, and 200 °C for NH3, H2, and NO at various O2 concentrations. The SWCNTs are separated from a mixture of metallic and semiconducting SWCNTs based on the agarose gel column chromatography. The SWCNT gas sensor responds to all the gases in 20% O2, and the gas selectivity to NH3 and H2 is controlled by the operating temperature. NO transforms to NO2 in the presence of O2 and decreases the resistance of the sensor as an oxidizing gas. The sensor can detect NH3, H2, and NO without O2. Along with the good conductivity of the SWCNTs, the good conductive paths between the SWCNTs through the semiconducting polymer dispersant reduce the noise of the sensor resistance and enable the detection of small changes in the resistance to minimal gas concentration.

Metal-oxide based ammonia gas sensors: A review

2020 ◽  
Vol 10 ◽  
Author(s):  
Priya Gupta ◽  
Savita Maurya ◽  
Narendra Kumar Pandey ◽  
Vernica Verma
Keyword(s):  
Metal Oxide ◽  
Metal Oxides ◽  
Gas Sensor ◽  
Gas Sensors ◽  
Review Paper ◽  
Gas Sensing ◽  
Gas Sensitivity ◽  
Ammonia Gas ◽  
Ammonia Sensing ◽  
Ammonia Gas Sensors

: This review paper encompasses a study of metal-oxide and their composite based gas sensors used for the detection of ammonia (NH3) gas. Metal-oxide has come into view as an encouraging choice in the gas sensor industry. This review paper focuses on the ammonia sensing principle of the metal oxides. It also includes various approaches adopted for increasing the gas sensitivity of metal-oxide sensors. Increasing the sensitivity of the ammonia gas sensor includes size effects and doping by metal or other metal oxides which will change the microstructure and morphology of the metal oxides. Different parameters that affect the performances like sensitivity, stability, and selectivity of gas sensors are discussed in this paper. Performances of the most operated metal oxides with strengths and limitations in ammonia gas sensing application are reviewed. The challenges for the development of high sensitive and selective ammonia gas sensor are also discussed.

scholarly journals Explosive Molecule Sensing at Lattice Defect Sites in Metallic Carbon Nanotubes

2021 ◽  
Author(s):  
Manasi Doshi ◽  
Eric Paul Fahrenthold
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Experimental Research ◽  
Gas Sensing ◽  
Lattice Defect ◽  
Sensing Mechanism ◽  
Defect Sites ◽  
Chemiresistive Sensing ◽  
Hazardous Gas

Explosives and hazardous gas sensing using carbon nanotube (CNT) based sensors has been a focus of considerable experimental research. The simplest sensors have employed a chemiresistive sensing mechanism, and rely...

Carbon Nanotube Gas Sensor Fabricated on Anodic Aluminum Oxide

2007 ◽  
Vol 124-126 ◽  
pp. 1309-1312
Author(s):  
Nguyen Duc Hoa ◽  
Nguyen Van Quy ◽  
Gyu Seok Choi ◽  
You Suk Cho ◽  
Se Young Jeong ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Gas Sensor ◽  
Chemical Vapor ◽  
Fast Response ◽  
Device Fabrication ◽  
Alumina Oxide ◽  
Response And Recovery ◽  
New Type ◽  
P Type

A new type of gas sensor was realized by directly depositing carbon nanotube on nano channels of the anodic alumina oxide (AAO) fabricated on p-type silicon substrate. The carbon nanotubes were synthesized by thermal chemical vapor deposition at a very high temperature of 1200 oC to improve the crystallinity. The device fabrication process was also developed. The contact of carbon nanotubes and p-type Si substrate showed a Schottky behavior, and the Schottky barrier height increased with exposure to gases while the overall conductivity decreased. The sensors showed fast response and recovery to ammonia gas upon the filling (400 mTorr) and evacuation.

scholarly journals Ammonia Gas Sensing Characteristic of P3HT-rGO-MWCNT Composite Films

2021 ◽  
Vol 11 (15) ◽  
pp. 6675
Author(s):  
Tran Si Trong Khanh ◽  
Tran Quang Trung ◽  
Le Thuy Thanh Giang ◽  
Tran Quang Nguyen ◽  
Nguyen Dinh Lam ◽  
...  
Keyword(s):  
Response Time ◽  
Gas Sensor ◽  
Gas Sensing ◽  
Composite Films ◽  
Weight Ratio ◽  
Film Surface ◽  
Relative Sensitivity ◽  
Ammonia Gas ◽  
Casting Technique ◽  
Multi Walled Carbon Nanotubes

In this work, the P3HT:rGO:MWCNTs (PGC) nanocomposite film applied to the ammonia gas sensor was successfully fabricated by a drop-casting technique. The results demonstrated that the optimum weight ratio of the PGC nanocomposite gas sensor is 20%:60%:20% as the weight ratio of P3HT:rGO:MWCNTs (called PGC-60). This weight ratio leads to the formation of nanostructured composites, causing the efficient adsorption/desorption of ammonia gas in/out of the film surface. The sensor based on PGC-60 possessed a response time of 30 s, sensitivity up to 3.6% at ammonia gas concentration of 10 ppm, and relative sensitivity of 0.031%/ppm. These results could be attributed to excellent electron transportation of rGO, the main adsorption activator to NH3 gas of P3HT, and holes move from P3HT to the cathodes, which works as charge “nano-bridges” carriers of Multi-Walled Carbon Nanotubes (MWCNTs). In general, these three components of PGC sensors have significantly contributed to the improvement of both the sensitivity and response time in the NH3 gas sensor.

scholarly journals Gold and ZnO-Based Metal-Semiconductor Network for Highly Sensitive Room-Temperature Gas Sensing

Sensors ◽  
2019 ◽  
Vol 19 (18) ◽  
pp. 3815
Author(s):  
Renyun Zhang ◽  
Magnus Hummelgård ◽  
Joel Ljunggren ◽  
Håkan Olin
Keyword(s):  
Solar Cells ◽  
Gas Sensor ◽  
Network Structure ◽  
Room Temperature ◽  
Gas Sensing ◽  
Zno Nanowires ◽  
Gold Particles ◽  
Highly Sensitive ◽  
Semiconductor Electronics ◽  
New Type

Metal-semiconductor junctions and interfaces have been studied for many years due to their importance in applications such as semiconductor electronics and solar cells. However, semiconductor-metal networks are less studied because there is a lack of effective methods to fabricate such structures. Here, we report a novel Au–ZnO-based metal-semiconductor (M-S)n network in which ZnO nanowires were grown horizontally on gold particles and extended to reach the neighboring particles, forming an (M-S)n network. The (M-S)n network was further used as a gas sensor for sensing ethanol and acetone gases. The results show that the (M-S)n network is sensitive to ethanol (28.1 ppm) and acetone (22.3 ppm) gases and has the capacity to recognize the two gases based on differences in the saturation time. This study provides a method for producing a new type of metal-semiconductor network structure and demonstrates its application in gas sensing.

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