A gas nanosensor unaffected by humidity (original) (raw)
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Electrical and gas sensing properties of polyaniline functionalized single-walled carbon nanotubes
Nanotechnology, 2010
Electrical and gas sensing properties of single-walled carbon nanotube networks functionalized with polyaniline (PANI-SWNTs) were systematically investigated to understand the gas sensing mechanisms and optimize sensing performance. The temperature-dependent electrical resistance and field-effect transistor (FET) transfer characteristics indicated that the electrical properties of PANI-SWNTs are dominated by the PANI coating. The FET transfer characteristics of PANI-SWNTs exposed to different NH3 concentrations indicated that the dominant sensing mechanism is the deprotonation of PANI by NH3. Sensing experiments with different gas analytes revealed that PANI-SWNTs responded positively to NH3, and negatively to NO2 and H2S with sensitivities of 5.8% per ppmv of NH3, 1.9% per ppmv of NO2, and 3.6% per ppmv of H2S. The lower detection limits were 50, 500, and 500 ppb for NH3, NO2, and H2S, respectively.
Electrochemically Functionalized Single-Walled Carbon Nanotube Gas Sensor
Electroanalysis, 2006
We demonstrate a facile fabrication method to make chemical gas sensors using single-walled carbon nanotubes (SWNT) electrochemically functionalized with polyaniline (PANI). The potential advantage of this method is to enable targeted functionalization with different materials to allow for creation of high-density individually addressable nanosensor arrays. PANI-SWNT network based sensors were tested for on-line monitoring of ammonia gas. The results show a superior sensitivity of 2.44% DR/R per ppm v NH 3 (which is more than 60 times higher than intrinsic SWNT based sensors), a detection limit as low as 50 ppb v , and good reproducibility upon repeated exposure to 10 ppm v NH 3 . The typical response time of the sensors at room temperature is on the order of minutes and the recovery time is a few hours. Higher sensitivities were observed at lower temperatures. These results indicate that electrochemical functionalization of SWNTs provides a promising new method of creating highly advanced nanosensors with improved sensitivity, detection limit, and reproducibility.
Poly(m-aminobenzene sulfonic acid) functionalized single-walled carbon nanotubes based gas sensor
Nanotechnology, 2007
We have demonstrated a NH 3 , NO 2 and water vapour sensor based on poly(m-aminobenzene sulfonic acid) functionalized single-walled carbon nanotube (SWNT-PABS) networks. The SWNT-PABS based sensors were fabricated by simple dispersion of SWNT-PABS on top of pre-fabricated gold electrodes. SWNT-PABS sensors showed excellent sensitivity with ppb v level detection limits (i.e., 100 ppb v for NH 3 and 20 ppb v for NO 2 ) at room temperature. The response time was short and the response was totally reversible. The sensitivity could be tuned by adjusting the sensor initial resistance. The sensors were also suitable for monitoring relative humidity in air.
An effective monitoring of the air quality in an urban environment requires the capability to measure polluting gas concentrations in the low-ppb range, a limit so far virtually neglected in most of the novel carbon nanotube (CNT)-based sensors, as they are usually tested against pollutant concentrations in the ppm range. We present low-cost gas sensors based on single-walled CNT (SWCNT) layers prepared on plastic substrates and operating at room temperature, displaying a high sensitivity to [NH3]. Once combined with the low noise, the high sensitivity allowed us to reach an ammonia detection limit of 13 ppb. This matches the requirements for ammonia monitoring in the environment, disclosing the possibility to access the ppt detection limit. Furthermore, a blend of SWCNT bundle layers with indium-tin oxide (ITO) nanoparticles resulted in a threefold sensitivity increase with respect to pristine CNT for concentrations above 200 ppb. Finally, the peculiar response of the ITO-SWCNT blend to water vapor provides a way to tailor the sensor selectivity with respect to the relevant interfering effects of humidity expected in outdoor environmental monitoring.
ACS sensors, 2018
Fabrication and comparative analysis of the gas sensing devices based on individualized single-walled carbon nanotubes of four different types (pristine, boron doped, nitrogen doped, and semiconducting ones) for detection of low concentrations of ammonia is presented. The comparison of the detection performance of different devices, in terms of resistance change under exposure to ammonia at low concentrations combined with the detailed analysis of chemical bonding of dopant atoms to nanotube walls sheds light on the interaction of NH with carbon nanotubes. Furthermore, chemoresistive measurements showed that the use of semiconducting nanotubes as conducting channels leads to the highest sensitivity of devices compared to the other materials. Electrical characterization and analysis of the structure of fabricated devices showed a close relation between amount and quality of the distribution of deposited nanotubes and their sensing properties. All measurements were performed at room t...
Room Temperature Single Walled Carbon Nanotubes (SWCNT) Chemiresistive Ammonia Gas Sensor
Single walled carbon nanotubes were functionalized with carboxyl (–COOH) group using simple acid treatment process. Thin films of functionalized SWCNTs were fabricated using drop cast technique from the dispersion prepared in de-ionized water. These films were characterized using FE-SEM, FTIR, Raman spectroscopy techniques and current-voltage measurements were carried at room and elevated temperature. SWCNT chemiresistor gas sensor devices on silicon substrate were fabricated using conventional microfabrication technology with pristine and functionalized SWCNTs. Fabricated gas sensors were exposed to ammonia in an in-house developed gas sensor characterization system and response was measured at ammonia concentration up to 50 ppm at room temperature. Functionalized SWCNTs chemiresistor showed an impressive ammonia response of 20.2 % compared with 2.9 % of pristine counterpart. Response enhancement mechanisms are discussed in terms of defects and gas molecule adsorption on CNT surfac...
Study of chemiresistor type CNT doped polyaniline gas sensor
Synthetic Metals, 2010
The composite thin films of polyaniline (Pani) with multiwall carbon nanotube (MWNT) and single wall carbon nanotube (SWNT) for hydrogen gas sensing application are presented in this paper. Polyaniline (Pani) was synthesized by chemical oxidative polymerization of aniline using ammonium persulfate in acidic medium. The SWNT and MWNT were doped in Pani in presence of champhor sulfonic acid (CSA) by solution mixing method. Thin films of CNT/Pani composites were prepared by spin coating method. Finally, the response of these composite films for hydrogen gas was evaluated by monitering the change in electrical resistance at room tempeature. It is observed that the SWNT/Pani and MWNT/Pani composite films show a higher response as compare to pure Pani. The structural and optical properties of these composite films have been characterised by X-ray diffraction (XRD) and UV–visible spectroscopy respectively. Surface morphology of these films has also been characterised by optical microscopy.
Room Temperature Ammonia Gas Sensing Using Polyaniline Nanoparticles Based Sensor
2017
In the present research effort, we account for the acquisition of room temperature ammonia gas sensor based on polyaniline (PANI) nanoparticles. The polyaniline thin film was deposited on porous silicon substrate using the spin coating method. PANI nanofilms were characterized for their structural as well as surface morphologies. The XRD analysis showed partially crystalline nature polyaniline thin film. The Ammonia gas sensing response of PANI was obtained for different concentration of ammonia (50, 100, 200, 300, 400, 500 and 600 ppm). The sensitivity of PANI was observed to increase with the increase in the concentration of ammonia.
The possibility of using novel architectures based on carbon nanotubes (CNTs) for a realistic monitoring of the air quality in an urban environment requires the capability to monitor concentrations of polluting gases in the low-ppb range. This limit has been so far virtually neglected, as most of the testing of new ammonia gas sensor devices based on CNTs is carried out above the ppm limit. In this paper, we present single-wall carbon nanotube (SWCNT) chemiresistor gas sensors operating at room temperature, displaying an enhanced sensitivity to NH3. Ammonia concentrations in air as low as 20 ppb have been measured, and a detection limit of 3 ppb is demonstrated, which is in the full range of the average NH3 concentration in an urban environment and well below the sensitivities so far reported for pristine, non-functionalized SWCNTs operating at room temperature. In addition to careful preparation of the SWCNT layers, through sonication and dielectrophoresis that improved the quality of the CNT bundle layers, the lowppb limit is also attained by revealing and properly tracking a fast dynamics channel in the desorption process of the polluting gas molecules.
Carbon Nanotube Sensors for Gas and Organic Vapor Detection
Nano Letters, 2003
A gas sensor, fabricated by the simple casting of single-walled carbon nanotubes (SWNTs) on an interdigitated electrode (IDE), is presented for gas and organic vapor detection at room temperature. The sensor responses are linear for concentrations of sub ppm to hundreds of ppm with detection limits of 44 ppb for NO 2 and 262 ppb for nitrotoluene. The time is on the order of seconds for the detection response and minutes for the recovery. The variation of the sensitivity is less than 6% for all of the tested devices, comparable with commercial metal oxide or polymer microfilm sensors while retaining the room-temperature high sensitivity of the SWNT transistor sensors and manufacturability of the commercial sensors. The extended detection capability from gas to organic vapors is attributed to direct charge transfer on individual semiconducting SWNT conductivity with additional electron hopping effects on intertube conductivity through physically adsorbed molecules between SWNTs.