Robust fabrication of selective and reversible polymer coated carbon nanotube-based gas sensors (original) (raw)
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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.
Nano Letters, 2003
Arrays of electrical devices with each comprising multiple single-walled carbon nanotubes (SWNT) bridging metal electrodes are obtained by chemical vapor deposition (CVD) of nanotubes across prefabricated electrode arrays. The ensemble of nanotubes in such a device collectively exhibits large electrical conductance changes under electrostatic gating, owing to the high percentage of semiconducting nanotubes. This leads to the fabrication of large arrays of low-noise electrical nanotube sensors with 100% yield for detecting gas molecules. Polymer functionalization is used to impart high sensitivity and selectivity to the sensors. Polyethyleneimine coating affords n-type nanotube devices capable of detecting NO 2 at less than 1 ppb (parts-per-billion) concentrations while being insensitive to NH 3 . Coating Nafion (a polymeric perfluorinated sulfonic acid ionomer) on nanotubes blocks NO 2 and allows for selective sensing of NH 3 . Multiplex functionalization of a nanotube sensor array is carried out by microspotting. Detection of molecules in a gas mixture is demonstrated with the multiplexed nanotube sensors.
TOPICAL REVIEW: Recent progress in carbon nanotube-based gas sensors
Nanotechnol, 2008
The development of carbon nanotube-(CNTs-)based gas sensors and sensor arrays has attracted intensive research interest in the last several years because of their potential for the selective and rapid detection of various gaseous species by novel nanostructures integrated in miniature and low-power consuming electronics. Chemiresistors and chemical field effect transistors are probably the most promising types of gas nanosensors. In these sensors, the electrical properties of nanostructures are dramatically changed when exposed to the target gas analytes. In this review, recent progress on the development of different types of CNT-based nanosensors is summarized. The focus was placed on the means used by various researchers to improve the sensing performance (sensitivity, selectivity and response time) through the rational functionalization of CNTs with different methods (covalent and non-covalent) and with different materials (polymers and metals).
Chemical Sensors Based on Carbon Nanotubes: Comparison Between Single and Bundles of Ropes
Sensors and Microsystems - Proceedings of the 12th Italian Conference, 2008
A chemical gas sensor based on a single rope of single walled carbon nanotubes (SWCNTs) has been fabricated first isolating the rope on a silicon/Si 3 N 4 substrate and then realizing, at its ends, two platinum microelectrodes by means of a Focused Ion Beam (FIB). Its electrical behaviour at room temperature in toxic gas environments has been investigated and compared to sensors based on bundles of SWCNT ropes. For all the devices upon exposure to NO2 and NH3 the conductance has been found to increase or decrease respectively. Response time in NO2 is however faster for device based on the single rope. A mechanism for molecular sensing is proposed.
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.
Angewandte Chemie International Edition, 2008
Single-walled carbon nanotubes (SWNTs) are quasi-1D electronic materials consisting only of surface atoms whose electrical properties can be directly modulated by molecular adsorption. This environmental sensitivity has been utilized to engineer sensor arrays with electrical responses to partsper-billion (ppb) doses of organic vapors. Polymers, metal nanoparticles, and DNA have been reported as functional materials for enhancing the selectivity of such systems. A central problem with the majority of these sensor arrays, including a recent SWNT chemi-capacitor arrangement, is that molecular adsorption is irreversible upon exposure to a wide range of analytes. To be clear, we define reversible adsorption not as the ability to be externally or manually regenerated, but rather the spontaneous desorption of analyte when the chemical potential gradient has been removed. By this criterion, strong electron donors or acceptors appear to adsorb onto bare single-nanotube or network devices irreversibly at room temperature for the vast majority of systems examined in the literature. [2-5, 8, 9, 11, 13-15] In later publications, some of these same systems demonstrate reversible sensor responses from the same analytes, thus underscoring a poor understanding of what determines molecular reversibility. No examination of the disparity has been reported to date.
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.
Material Science & Engineering International Journal, 2020
This paper reported the results of application of screen printed electrodes (SPE) based on polymer/carbon nanostructures (multi wall carbon nanotubes – MWCNT and grapheme – G) for gas sensors. Commercial SPEs were modified by polymers such as conductive polymer Poly Vinylidene Fluorid – PVDF and biocompatible Poly Ethylene Glycol – PEG. Modified SPEs were tested in ammonia vapors with different concentration: 3, 6.2, 12.5 and 25% (wt.). Sensor-testing was performed by monitoring the change in the electrical resistance of the electrodes. The physical characterization of the sensing electrodes was performed by Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) in ATR mode. The surface morphology of CNT/PEG and CNT/ PVDF modifications, after coating with 25% NH3, expressed the effects of ammonia on the surface of the nanocomposite layer. The ammonia solution acts aggressively on the modified surface, causing furrows to form in the uniform structure and very small nanorods of oxides.
Recent progress in carbon nanotube-based gas sensors
Nanotechnology, 2008
The development of carbon nanotube-(CNTs-)based gas sensors and sensor arrays has attracted intensive research interest in the last several years because of their potential for the selective and rapid detection of various gaseous species by novel nanostructures integrated in miniature and low-power consuming electronics. Chemiresistors and chemical field effect transistors are probably the most promising types of gas nanosensors. In these sensors, the electrical properties of nanostructures are dramatically changed when exposed to the target gas analytes. In this review, recent progress on the development of different types of CNT-based nanosensors is summarized. The focus was placed on the means used by various researchers to improve the sensing performance (sensitivity, selectivity and response time) through the rational functionalization of CNTs with different methods (covalent and non-covalent) and with different materials (polymers and metals).
IEEE Sensors Letters
CNTs based chemiresistive gas sensors are known to not fully recover to the baseline after gas exposure. This is why often heat is applied to thermally activate the sensor and improve the gas desorption process occurring at the surface. In this paper, we combine single-walled CNTs (SWCNTs) with conjugated polymers (CPs) i.e., Poly(3-hexylthiophene)(P3HT), to realize chemiresistive gas sensors with improved recovery. Five configurations were fabricated with diverse positions of the sensing material layers with respect to the interdigitated electrodes (IDEs), namely: SWCNTs/IDEs and P3HT/IDEs as controls for the CNTs and P3HT singular materials; SWCNTs/P3HT/IDEs, SWCNTs/IDEs/P3HT and P3HT/SWCNTs/IDEs as combined sensing materials layers configurations. The results show that in particular, the P3HT/SWCNTs/IDEs sensors exhibit better performance with respect to the other configurations when exposed to 5, 25, and 50 ppm NH 3. Improvements in terms of response time (103 seconds faster at 5 ppm), sensor response (+26.83% at 50 ppm), and improved recovery to the baseline (+25.69% and +11.34% at 5 and 50 ppm respectively) were obtained when evaluated against SWCNTs/IDEs sensors. These findings suggest that addition of CPs (i.e. P3HT) may be a promising approach to enhance the performance and stability of SWCNTs-based chemiresistive gas sensors, providing a new direction for future research in this field. Future research to investigate the effect of others CPs on the CNTs based chemiresistive gas sensors will be needed to realize more efficient and reliable ammonia gas sensors.