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Metal-modified and vertically aligned carbon nanotube sensors array for landfill gas monitoring applications

TitoloMetal-modified and vertically aligned carbon nanotube sensors array for landfill gas monitoring applications
Tipo di pubblicazioneArticolo su Rivista peer-reviewed
Anno di Pubblicazione2010
AutoriPenza, Michele, Rossi R., Alvisi Marco, and Serra Emanuele
RivistaNanotechnology
Volume21
ISSN09574484
Parole chiaveair pollutant, Air Pollutants, Alumina substrates, Array sensors, article, Atmospheric humidity, carbon, carbon nanotube, Carbon nanotubes, Charge transfer, Chemical sensors, Chemical vapor deposition, Chemiresistors, chemistry, CNT sensors, CO and NO, Cross sensitivity, Electrical charges, electron, Fe-coated, Functional characterization, Gas, Gas concentration, Gas detection, Gas detectors, Gas sensitivity, Gas sensor arrays, Gases, High sensitivity, Intensity ratio, Ion exchange, Land fill, Landfill gas, Low-power consumption, Maximum sensitivity, metal nanoparticle, Metal nanoparticles, Metal recovery, Metals, methodology, Microscopy, Mixtures, Models, Multi-walled, Multicomponent gas-mixtures, Multicomponent mixture, Nanoclusters, nanotechnology, Nanotubes, Operating temperature, Optimal temperature, Pattern Recognition, Plasma deposition, Platinum, Principal component analysis, Radio frequency plasma, Raman scattering, Raman spectroscopy, Rapid-heating, Recovery mechanisms, Refuse Disposal, Relative humidities, Rf-PECVD, Room temperature, Ruthenium, Scanning, Scanning electron microscopy, SEM, Sensing elements, Sensing mechanism, Sensing property, Sensor arrays, silver, TEM, Temperature, Theoretical, theoretical model, Top surface, Transmission, Transmission electron microscopy, Tube diameters, Ultrastructure, Vertically aligned, Vertically aligned carbon nanotube, Waste disposal
Abstract

Vertically aligned carbon nanotube (CNT) layers were synthesized on Fe-coated low-cost alumina substrates using radio-frequency plasma enhanced chemical vapour deposition (RF-PECVD) technology. A miniaturized CNT-based gas sensor array was developed for monitoring landfill gas (LFG) at a temperature of 150 °C. The sensor array was composed of 4 sensing elements with unmodified CNT, and CNT loaded with 5nm nominally thick sputtered nanoclusters of platinum (Pt), ruthenium (Ru) and silver (Ag). Chemical analysis of multicomponent gas mixtures constituted of CO2, CH4, H2, NH 3, CO and NO2 has been performed by the array sensor responses and pattern recognition based on principal component analysis (PCA). The PCA results demonstrate that the metal-decorated and vertically aligned CNT sensor array is able to discriminate the NO2 presence in the multicomponent mixture LFG. The NO2 gas detection in the mixture LFG was proved to be very sensitive, e.g.: the CNT:Ru sensor shows a relative change in the resistance of 1.50% and 0.55% for NO2 concentrations of 3.3ppm and 330ppb dispersed in the LFG, respectively, with a wide NO2 gas concentration range measured from 0.33 to 3.3ppm, at the sensor temperature of 150 °C. The morphology and structure of the CNT networks have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. A forest-like nanostructure of vertically aligned CNT bundles in the multi-walled form appeared with a height of about 10 νm and a single-tube diameter varying in the range of 5-35nm. The intensity ratio of the Raman spectroscopy D-peak and G-peak indicates the presence of disorder and defects in the CNT networks. The size of the metal (Pt, Ru, Ag) nanoclusters decorating the CNT top surface varies in the range of 5-50nm. Functional characterization based on electrical charge transfer sensing mechanisms in the metal-modified CNT-chemoresistor array demonstrates high sensitivity by providing minimal sub-ppm level detection, e.g., download up to 100ppb NO2, at the sensor temperature of 150 °C. The gas sensitivity of the CNT sensor array depends on operating temperature, showing a lower optimal temperature of maximum sensitivity for the metal-decorated CNT sensors compared to unmodified CNT sensors. Results indicate that the recovery mechanisms in the CNT chemiresistors can be altered by a rapid heating pulse from room temperature to about 110 °C. A comparison of the NO2 gas sensitivity for the chemiresistors based on disorderly networked CNTs and vertically aligned CNTs is also reported. Cross-sensitivity towards relative humidity of the CNT sensors array is investigated. Finally, the sensing properties of the metal-decorated and vertically aligned CNT sensor arrays are promising to monitor gas events in the LFG for practical applications with low power consumption and moderate sensor temperature. © 2010 IOP Publishing Ltd.

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URLhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-77149173439&doi=10.1088%2f0957-4484%2f21%2f10%2f105501&partnerID=40&md5=c452267ec443dd4cce6b57f3a2ea8d94
DOI10.1088/0957-4484/21/10/105501
Citation KeyPenza2010