scholarly journals The Effect of CH4 and CO2 Exposure on Carbon Nanotubes Electrical Resistance

2011 ◽  
Vol 214 ◽  
pp. 655-661 ◽  
Author(s):  
Amin Firouzi ◽  
Shafreeza Sobri ◽  
Faizah Mohd Yasin ◽  
Fakhru'l Razi Ahmadun
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Resistance ◽  
Gas Sensing ◽  
Quartz Substrate ◽  
Chemical Vapor ◽  
High Sensitivity ◽  
Sensing Applications ◽  
Type Semiconductor ◽  
Adsorption Of Co2 ◽  
P Type

This research was carried out to monitor and investigate the gas sensing effects on carbon nanotubes (CNTs) by a systematic study of the variations in the electrical resistance as sensor signal induced by adsorption of CO2 and CH4 gaseous molecules. The CNTs were synthesized by Floating Catalyst Chemical Vapor Deposition (FC-CVD) method on quartz substrate under benzene bubble at temperature of 700°C. Then, they were tested for gas sensing applications operating at room temperature. Upon exposure to gaseous molecules, the electrical resistance of CNTs dramatically increased for both CO2 and CH4 gases with short response time and high sensitivity. It was also observed that the CNTs device behaves as a p-type semiconductor when exposed to gaseous molecules. In addition, the recovery of the sensors and mechanism of gas sensing procedure are discussed.

scholarly journals CH4 and CO2 Detection by Using Carbon Nanotube-Based Sensors

2011 ◽  
Vol 214 ◽  
pp. 482-489 ◽  
Author(s):  
Amin Firouzi ◽  
Shafreeza Sobri ◽  
Faizah Mohd Yasin ◽  
Fakhru'l Razi Ahmadun
Keyword(s):  
Electrical Resistance ◽  
Gas Flow ◽  
Gas Adsorption ◽  
Quartz Substrate ◽  
Chemical Vapor ◽  
Experimental Conditions ◽  
Cvd Method ◽  
Type Semiconductor ◽  
P Type ◽  
Catalyst Chemical Vapor Deposition

This research was carried out to investigate the effect of gas adsorption towards the electrical resistance of carbon nanotubes (CNTs) thin film. CNTs were synthesized by Floating Catalyst Chemical Vapor Deposition (FC-CVD) method on quartz substrate at 950°C under methane gas flow rate of 150 Standard Cubic Centimeters per Minute (SCCM). Then, the electrical resistance of CNTs was measured by exposing the sensors to CO2 and CH4 gases operating at room temperature. The sensors showed high responses to the gaseous molecules. In the same experimental conditions, the recovery of the sensors was different for CO2 and CH4. It was also observed that the CNTs device behaves as a p-type semiconductor when exposed to gaseous molecules. The fabrication process was relatively simple and did not require special techniques.

scholarly journals MWCNT Devices Fabricated by Dielectrophoresis: Study of Their Electrical Behavior Related to Deposited Nanotube Amount for Gas Sensing Applications

2015 ◽  
Vol 10 (1) ◽  
pp. 13-20
Author(s):  
Elisabete Galeazzo ◽  
Marcos C. Moraes ◽  
Henrique E. M. Peres ◽  
Michel O. S. Dantas ◽  
Victor G. C. Lobo ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Gas Sensing ◽  
High Sensitivity ◽  
Cost Effective ◽  
Adsorbed Water ◽  
Fast Response ◽  
Process Time ◽  
Electrical Behavior ◽  
Glass Substrates ◽  
Sensing Applications

Intensive research has been focused on investigating new sensing materials, such as carbon nanotubes (CNT) because of their promising characteristics. However, there are challenges related to their application in commercial devices such as sensitivity, compatibility, and complexity of miniaturization, among others. We report the study of the electrical behavior of devices composed by multi-walled carbon nanotubes (MWCNT) deposited between aluminum electrodes on glass substrates by means of dielectrophoresis (DEP), which is a simple and cost-effective method. The devices were fabricated by varying the DEP process time. Remarkable changes in their electric resistance were noticed depending on the MWCNT quantities deposited. Other electrical properties of devices such as high sensitivity, fast response time and stability are also characterized in humid environment. A humidity sensing mechanism is proposed on the basis of charge transfer between adsorbed water molecules and the MWNTC surface or between water and the glass surface.

scholarly journals Improvement of NO Gas Sensing Properties of Polyaniline/MWCNT Composite by Photocatalytic Effect of TiO2

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Jumi Yun ◽  
Sonyeo Jeon ◽  
Hyung-Il Kim
Keyword(s):  
Carbon Nanotube ◽  
Electrical Resistance ◽  
Gas Sensing ◽  
Photocatalytic Effect ◽  
Highly Sensitive ◽  
Gas Sensing Properties ◽  
Nanotube Composites ◽  
Type Semiconductor ◽  
P Type ◽  
Coated Carbon

The highly sensitive and rapid NO gas sensor was prepared with polyaniline/TiO2/carbon nanotube composites. Aniline was polymerized on the surface of carbon nanotube (p-type semiconductor) with embedding TiO2. The gas sensing property was measured by the changes of electrical resistance without or with UV irradiation to investigate the photodegradation of NO by TiO2. The photo-degraded products such as HNO2, NO2, and HNO3, which were adsorbed on the PANi-coated carbon nanotubes, resulted in the decreased electrical resistance in the p-type semiconductors of carbon nanotube and polyaniline. The advantages of TiO2photocatalyst in gas sensing were apparent in the improvement in both sensitivity and response rate.

scholarly journals NO2 Selective Sensor Based on α-Fe2O3 Nanoparticles Synthesized via Hydrothermal Technique

Sensors ◽  
2019 ◽  
Vol 19 (1) ◽  
pp. 167 ◽  
Author(s):  
Mokhtar Hjiri ◽  
Mohamed Aida ◽  
Giovanni Neri
Keyword(s):  
Gas Sensing ◽  
Environmental Pollutants ◽  
High Sensitivity ◽  
X Ray Diffraction ◽  
Hydrothermal Route ◽  
Transmission Electron ◽  
Low Concentrations ◽  
Semiconductor Behavior ◽  
Type Semiconductor ◽  
P Type

In the present work, hematite (α-Fe2O3) nanopowders were successfully prepared via a hydrothermal route. The morphology and microstructure of the synthesized nanopowders were analyzed by using scanning and transmission electron microscopy (SEM and TEM, respectively) analysis and X-ray diffraction. Gas sensing devices were fabricated by printing α-Fe2O3 nanopowders on alumina substrates provided with an interdigitated platinum electrode. To determine the sensor sensitivity toward NO2, one of the main environmental pollutants, tests with low concentrations of NO2 in air were carried out. The results of sensing tests performed at the operating temperature of 200 °C have shown that the α-Fe2O3 sensor exhibits p-type semiconductor behavior and high sensitivity. Further, the dynamics exhibited by the sensor are also very fast. Lastly, to determine the selectivity of the α-Fe2O3 sensor, it was tested toward different gases. The sensor displayed large selectivity to nitrogen dioxide, which can be attributed to larger affinity towards NO2 in comparison to other pollutant gases present in the environment, such as CO and CO2.

scholarly journals Surface Modification of Carbon Nanotube Networked Films with Au Nanoclusters for Enhanced Gas Sensing Applications

2008 ◽  
Vol 2008 ◽  
pp. 1-8 ◽  
Author(s):  
M. Penza ◽  
R. Rossi ◽  
M. Alvisi ◽  
G. Cassano ◽  
M. A. Signore ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Gas Sensing ◽  
Chemical Vapor ◽  
Gas Sensitivity ◽  
Multiwalled Carbon ◽  
Sensing Applications ◽  
Sensor Temperature ◽  
P Type ◽  
Gas Response ◽  
Ppm Level

Multiwalled carbon nanotube (MWCNT) films have been deposited by using plasma-enhanced chemical vapor deposition (PECVD) system onto alumina substrates, provided with 6 nm thick cobalt (Co) growth catalyst for remarkably improved gas sensing, at working temperature in the range of 100–. Functionalization of the MWCNTs with nanoclusters of gold (Au) sputtering has been performed to modify the surface of carbon nanotube networked films for enhanced and specific gas detection up to sub-ppm level. It is demonstrated that the gas sensitivity of the MWCNT-based sensors depends on Au-loading used as surface-catalyst. The gas response of MWCNT-based chemiresistor is attributed top-typeconductivity in the Au-modified semiconducting MWCNTs with a very good short-term repeatability and faster recovery. The sensor temperature of maximum sensitivity of the Au-functionalized MWCNTs is found to decrease with increasing Au-loading on their surface, and continuous gas monitoring at ppb level of is effectively performed with Au-modified MWCNT chemiresistors.

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.

Carbon Materials for Gas and Bio-Sensing Applications Beyond Graphene

2021 ◽  
pp. 39-68
Keyword(s):  
Carbon Nanotubes ◽  
Active Site ◽  
Material Science ◽  
Gas Sensing ◽  
Functionalized Nanoparticles ◽  
Sensing Applications ◽  
Electrochemical Biosensing ◽  
New Ideas ◽  
Enzymatic Biosensors ◽  
Enhanced Stability

The development of technology in the area of material science and nanotechnology is a worldwide concern to researchers for generating a substance by synthesizing nanoparticles with required properties. Carbonaceous materials have gained numerous interests because of their direct electron or charge transfer capacity between active site reception and functionalized nanoparticles without involvement of a mediator. However, among all existing materials, carbon nanotubes have been proven to elite beyond graphene. Carbon nanotubes (CNTs) possess extraordinary electrochemical biosensing and gas sensing due to their specific properties. This encourages researchers to gain new ideas about construction and development of immunosensors, genosensors, enzymatic biosensors and specific gas sensors based on above nanoparticles. Qualification of working electrode via incorporation of two or more of these nanoparticles gives enhanced stability, better sensitivity and functionality to the sensor. This chapter reviews basic information about sensors, their types, functionalization, fabrication mechanisms and applications for future prospective.

SnO2 Nano/Microfibers for Gas Sensors

2020 ◽  
Vol 405 ◽  
pp. 324-329
Author(s):  
Erika Mudra ◽  
Ivan Shepa ◽  
Alexandra Kovalcikova ◽  
Ondrej Milkovič ◽  
Jan Dusza
Keyword(s):  
Gas Sensors ◽  
Gas Sensing ◽  
Operating Temperature ◽  
Band Gap Energy ◽  
Calcination Process ◽  
Sensing Applications ◽  
Amorphous Nature ◽  
Coating Method ◽  
Type Semiconductor

SnO2 is an n-type semiconductor with the band gap energy of 3.6 eV. It has been widely studied for gas sensing applications, the sensitivity of which can be easily tuned by the operating temperature. The presented paper is focused on the preparation and detailed characterization of the hollow SnO2 nano/microfibers suitable for gas detection sensors. Ceramic SnO2 fibers were produced by needleless electrospinning and followed by the calcination process. The characterization was performed by SEM, TEM, XRD, and Raman spectroscopy. The precursor PVP/SnO2 fibers had amorphous nature. The calcination of the electro spun precursor resulted in the formation of hollow crystalline fibrous structures. The formation mechanism of hollow fibers has been described. Subsequently, a homogeneous fibrous layer was created by the spin coating method for gas sensing applications.

Laser-Doped SiC as Wireless Remote Gas Sensor Based on Semiconductor Optics

2012 ◽  
Vol 717-720 ◽  
pp. 1195-1198
Author(s):  
Geunsik Lim ◽  
Tariq Manzur ◽  
Aravinda Kar
Keyword(s):  
Valence Band ◽  
Energy Gap ◽  
Gas Sensing ◽  
Optical Signal ◽  
Acceptor Level ◽  
Spectral Bands ◽  
Sensing Applications ◽  
Electro Optic ◽  
Midwave Infrared ◽  
P Type

An uncooled SiC-based electro-optic device is developed for gas sensing applications. P-type dopants Ga, Sc, P and Al are incorporated into an n-type crystalline 6H-SiC substrate by a laser doping technique for sensing CO2, CO, NO2 and NO gases, respectively. Each dopant creates an acceptor energy level within the bandgap of the substrate so that the energy gap between this acceptor level and the valence band matches the quantum of energy emitted by the gas of interest. The photons of the gas excite electrons from the valence band to the acceptor level, which alters the electron density in these two states. Consequently, the refractive index of the substrate changes, which, in turn, modifies the reflectivity of the substrate. This change in reflectivity represents the optical signal of the sensor, which is probed remotely with a laser such as a helium-neon laser. Although the midwave infrared (3-5 mm) band is studied in this paper, the approach is applicable to other spectral bands.

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