Latest Advances in Modified/Functionalized Carbon Nanotube- Based Gas Sensors

Abstract

A gas sensor is a device that when exposed to gaseous species, is able to alter one or more of its physical properties, so that can be measured and quantified, directly or indirectly. These devices are used for applications in homeland security, medical diagnosis, environmental pollution, food processing, industrial emission, public security, agriculture, aerospace and aeronautics, among others. Desirable characteristics of a gas sensor are selectivity for different gases, sensitivity at low concentrations, fast response, room temperature operation some applications may require high temperature , low power consumption, low-cost, low maintenance and portability. Traditional techniques like gas chromatography GC , GC coupled to mass spectrometry GC-MS , Fourier transmission infrared spectroscopy FTIR and atomic emission detection AED provide high sensitivity, reliability and precision, but they are also bulky, time consuming, power consuming, operate at high temperature, and the high maintenance and requirement of trained technicians translate in high costs. In an effort to overcome those disadvantages, research in the area has been focused on the search for functional sensing materials.Carbon nanotubes CNTs have been have been focus of intense research as alternative sensing material because of their attractive characteristics like chemical, thermal and mechanical stability, high surface area, metallic and semi-conductive properties and functionalization capability [ ]. CNTs are graphene sheets rolled in a tubular fashion. Different types of CNTs can be synthesized single walled carbon nanotubes SWCNT , double wall carbon nanotubes DWCNTs and multi walled carbon nanotubes MWCNT .The publication of the first CNT-based sensor for NH and NO detection using an individual semiconducting SWCNT [ ] triggered the research activity in this area. Pristine CNTs have shown to be chemically inactive to gas molecules in general. However, their modifica-

Beneficial effect of Pd and MWCNT co-loading in SnO2 nanoparticles towards the low temperature detection of n-butane gas: synergistic effect on sensing performance

“…As both Pd and CNTs have higher work functions as compared to SnO 2 , [39][40][41][42] evidently, the addition of both Pd and CNTs will increase the resistance. However, the work function difference between CNTs and SnO 2 is less than that between Pd and SnO 2 .…”

Conductive ink applications on electronic textiles

“…Karbon nanotüpler sahip oldukları özelliklerinden dolayı son zamanlarda fazla ilgi gören malzemeler arasındadır. Özellikle, elektriksel iletkenlik özelliklerinden dolayı transistörler, RFID [39], sensörler [40]- [42], fotonikler gibi birçok yenilikçi alanlarda kullanılmaktadır [43]. Düşük maliyetli kontaktörler ve tamamlayıcı direnç sistemleri için nano karbon mürekkepler geliştirilmiştir.…”

Poly(vinylidene fluoride-hexafluoropropylene) composite sensors for volatile organic compounds detection in breath

“…Carboxylic-functionalized single wall CNTs (CNT-COOH) have been widely used to detect acetone [37,39]. Thus, in the first step, CNT-COOH were coated over QCM and tested for acetone.…”

“…Carbon-based materials, including CNT, carbon black, and graphene have also been investigated intensely for breath VOC sensing applications [26,34,35]. Pristine CNTs do not efficiently adsorb VOCs, but functionalization improves their performance for sensor applications [36][37][38]. Functionalization of CNTs with carboxylic groups and defect sites on CNTs created through acid sonication have shown improved adsorption of organic compounds and detection of low concentration VOCs.…”