Pt and Pd-nanoclusters functionalized carbon nanotubes networked films for sub-ppm gas sensors (original) (raw)
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Carbon nanotubes as new materials for gas sensing applications
Journal of The European Ceramic Society, 2004
Carbon nanotubes (CNTs) deposited by plasma enhanced chemical vapor deposition on Si3N4/Si substrates provided with Pt electrodes have been investigated as resistive gas sensors towards NO2. The electrical response has been measured exposing the films to sub-ppm NO2 concentrations (10–100 ppb in dry air) at different operating temperatures ranging between 25 and 250 °C. The response to NO2 has been found to be at maximum at around 165 °C. Upon exposure to NO2 the electrical resistance of randomly oriented CNTs is found to decrease. The prepared films show reasonable dynamic of the electrical response and high reproducibility of the electrical properties. The resistance decrease of the CNTs when exposed to NO2 gas and the sensor response to concentrations as low as 10 ppb NO2, suggest the possibility to utilize CNTs as new sensors for air-quality monitoring.
Sensors and Actuators B-chemical, 2009
We investigate the impact of the tailored load of gold (Au) nanoclusters functionalizing the sidewalls of the carbon nanotubes (CNTs) networks on gas sensing performance of a chemiresistor, operating at a working temperature in the range of 20-250 • C. CNTs networked films have been grown by radiofrequency plasma enhanced chemical vapour deposition (RF-PECVD) technology onto low-cost alumina substrate, provided with 6 nm nominally thick cobalt (Co) growth-catalyst. Nanoclusters of Au have been deposited by sputtering onto CNTs networks with a controlled loading of equivalent thickness of 2.5, 5 and 10 nm. Microstructure and morphology of the CNTs have been characterized by FE-SEM and TEM with diameter of the bundles of nanotubules of 10-40 nm. CNTs and Au-modified CNTs exhibit a p-type response with a decrease in electrical resistance upon exposure to oxidizing NO 2 gas and an increase in resistance upon exposure to reducing gases (NH 3 , CO, N 2 O, H 2 S, SO 2 ). Negligible response has been found for CNTs and Au-modified CNTs sensors exposed to CO, N 2 O, SO 2 . In the contrast, significantly enhanced gas response of NO 2 , H 2 S and NH 3 , up to a low limit of sub-ppm level, has been measured for Au-functionalized CNTs-chemiresistors. Highest gas sensitivity to NO 2 , H 2 S and NH 3 has been found by CNTs functionalized with Au loading of 5 nm, at 200 • C. An optimal operating temperature for each Au-modified CNTs-sensor exposed to NO 2 gas has been recorded. Good repeatability of the electrical response to 200 ppb NO 2 is also reported, at 200 • C. These results demonstrate the efficiency of the CNTs-chemiresistors functionalized with Au nanoclusters for selective air-pollutants environmental monitoring applications.
Journal of Sensors, 2008
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 NO 2 gas sensing, at working temperature in the range of 100-250 • C. 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 NO 2 gas detection up to sub-ppm level. It is demonstrated that the NO 2 gas sensitivity of the MWCNT-based sensors depends on Au-loading used as surface-catalyst. The gas response of MWCNT-based chemiresistor is attributed to p-type conductivity in the Au-modified semiconducting MWCNTs with a very good short-term repeatability and faster recovery. The sensor temperature of maximum NO 2 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 NO 2 is effectively performed with Au-modified MWCNT chemiresistors.
Applied Physics Letters, 2007
Multiwalled carbon nanotube ͑MWCNT͒ films have been fabricated by using plasma-enhanced chemical vapor deposition system onto Cr-Au patterned alumina substrates, provided with 3 nm thick Fe growth catalyst, for NO 2 and NH 3 gas sensing applications, at sensor temperature in the range of 100-250°C. Nanoclusters of noble metal surface catalysts ͑Au and Pt͒ have been sputtered on the surface of MWCNTs to enhance the gas sensitivity with respect to unfunctionalized carbon nanotube films. It was found that the gas sensitivity of Pt-and Au-functionalized MWCNT gas sensors significantly improved by a factor up to an order of magnitude through a spillover effect for NH 3 and NO 2 gas detections, respectively. The metal-functionalized MWCNT sensors exhibit very high gas sensitivity, fast response, reversibility, good repeatability, and sub-ppm range detection limit with the sensing properties of the MWCNT films tailored by surface catalyst used to functionalize the MWCNT 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).
Pt- and Pd-decorated MWCNTs for vapour and gas detection at room temperature
Beilstein Journal of Nanotechnology, 2015
Here we report on the gas sensing properties of multiwalled carbon nanotubes decorated with sputtered Pt or Pd nanoparticles. Sputtering allows for an oxygen plasma treatment that removes amorphous carbon from the surface of the carbon nanotubes and creates oxygenated surface defects in which metal nanoparticles nucleate within a few minutes. The decoration with the 2 nm Pt or the 3 nm Pd nanoparticles is very homogeneous. This procedure is performed at the device level (i.e., for carbon nanotubes deposited onto sensor substrates) for many devices in one batch, which illustrates the scalability for the mass production of affordable nanosensors. The response to selected aromatic and non-aromatic volatile organic compounds, as well as pollutant gases has been studied. Pt-and Pd-decorated multiwalled carbon nanotubes show a fully reversible response to the non-aromatic volatile organic compounds tested when operated at room temperature. In contrast, these nanomaterials were not responsive to the aromatic compounds studied (measured at concentrations up to 50 ppm). Therefore, these sensors could be useful in a small, battery-operated alarm detector, for example, which is able to discriminate aromatic from non-aromatic volatile organic compounds in ambient.
Lecture Notes Electrical Engineering, 2008
Multi walled carbon nanotubes (MWCNTs) are known to respond well to a range of gases and vapours. Metallic additives are often introduced to improve the sensitivity and selectivity to some gases. Here the difference in response between MWCNT sensors with and without a metal additive is discussed for a range of gases. Resistive sensors fabricated from chemical vapour deposition (CVD) grown multi walled carbon nanotubes (MWCNTs) collected between gold microelectrodes by dielectrophoresis are presented as a cheap, scaleable and facile method of producing carbon nanotube gas sensors. The MWCNTs sensors were exposed to a series of test gases including NO 2 , NH 3 , CO and H 2 and exhibited low ppm. detection at room temperature. Increasing the temperature not only reduced the recovery time of the sensors, but also increased the sensitivity to some gases whilst a decrease in the sensitivity was seen for other gases.
A Single-Walled Carbon Nanotube Network Gas Sensing Device
Sensors, 2011
The goal of this research was to develop a chemical gas sensing device based on single-walled carbon nanotube (SWCNT) networks. The SWCNT networks are synthesized on Al 2 O 3-deposted SiO 2 /Si substrates with 10 nm-thick Fe as the catalyst precursor layer using microwave plasma chemical vapor deposition (MPCVD). The development of interconnected SWCNT networks can be exploited to recognize the identities of different chemical gases by the strength of their particular surface adsorptive and desorptive responses to various types of chemical vapors. The physical responses on the surface of the SWCNT networks cause superficial changes in the electric charge that can be converted into electronic signals for identification. In this study, we tested NO 2 and NH 3 vapors at ppm levels at room temperature with our self-made gas sensing device, which was able to obtain responses to sensitivity changes with a concentration of 10 ppm for NO 2 and 24 ppm for NH 3 .
Sensors for sub-ppm NO2 gas detection based on carbon nanotube thin films
Applied Physics Letters, 2003
Carbon nanotubes ͑CNTs͒ deposited by plasma-enhanced chemical vapor deposition on Si 3 N 4 /Si substrates have been investigated as resistive gas sensors for NO 2 . Upon exposure to NO 2, the electrical resistance of the CNTs was found to decrease. The maximum variation of resistance to NO 2 was found at an operating temperature of around 165°C. The sensor exhibited high sensitivity to NO 2 gas at concentrations as low as 10 ppb, fast response time, and good selectivity. A thermal treatment method, based on repeated heating and cooling of the films, adjusted the resistance of the sensor film and optimized the sensor response to NO 2 .