Carbon nanotube–TiO₂hybrid films for detecting traces of O₂

Abstract

Hybrid titania films have been prepared using an adapted sol-gel method for obtaining well-dispersed hydrogen plasma-treated multiwall carbon nanotubes in either pure titania or Nb-doped titania. The drop-coating method has been used to fabricate resistive oxygen sensors based on titania or on titania and carbon nanotube hybrids. Morphology and composition studies have revealed that the dispersion of low amounts of carbon nanotubes within the titania matrix does not significantly alter its crystallization behaviour. The gas sensitivity studies performed on the different samples have shown that the hybrid layers based on titania and carbon nanotubes possess an unprecedented responsiveness towards oxygen (i.e. more than four times higher than that shown by optimized Nb-doped TiO(2) films). Furthermore, hybrid sensors containing carbon nanotubes respond at significantly lower operating temperatures than their non-hybrid counterparts. These new hybrid sensors show a strong potential for monitoring traces of oxygen (i.e. ≤10 ppm) in a flow of CO(2), which is of interest for the beverage industry.

Gas sensing properties and p-type response of ALD TiO2coated carbon nanotubes

“…Carbon nanotube-TiO 2 hybrid films showed an increasing resistance in presence of O 2 , revealing a n-type response of the hetero-structure. An enhanced sensitivity, attributed to the formation of a heterojunction, was also noted, compared to optimized Nb-doped TiO 2 sensing device [19]. The same behavior has been observed previously by us with electrospun CNTs/PVAc/TiO 2 composites [57].…”

“…Even though crystalline titanium oxide phases are mostly studied, few papers demonstrated good sensing properties of amorphous TiO 2 nanotubes towards oxygen at low/moderate temperature [18]. TiO 2 /CNT hybrid composites have been already investigated as gas sensors [19][20][21][22][23][24][25][26]. Early attempts focused on dispersion of CNTs into titania films [19,21,22].…”

Optical visualization of individual ultralong carbon nanotubes by chemical vapour deposition of titanium dioxide nanoparticles

“…Although a series of covalent and non-covalent methods have been reported to deposit metal [26][27][28][29][30] or metal oxide NPs [19][20][21][22][23][24][25][30][31][32][33][34][35][36][37][38][39][40][41][42] on CNTs, most of these methods require the CNTs to be functionalized or modified with surfactants 39,42 , and the processes are conducted in liquid phases 41,42 . These strategies cannot be applied on individual suspended ultralong CNTs because of the fact that they will destroy the suspended CNTs.…”

A flexible angle sensor made from MWNT/CuO/Cu2O nanocomposite films deposited by an electrophoretic co-deposition process

“…Recently, the use of carbon nanotubes (CNTs) and metal oxide nanostructures in electronic devices has attracted interest for a variety of applications; for example, CO gas sensors [1], dye sensitized solar cells [2], detectors for traces of oxygen [3], supercapacitors [4], hydrogen gas sensors [5], glucose sensors [6], field emission [7] and superior reversible Li-ion storage [8]. Many types of metal oxide have been used in CNT/metal-oxide composites, such as tin oxide (SnO 2 ) [1], titanium dioxide (TiO 2 ) [2,3], manganese oxide (MnO 2 ) [4], tungsten trioxide (WO 3 ) [5], copper oxide [6,8], ruthenium dioxide (RuO 2 ) [7] and zinc oxide (ZnO) [9].…”

“…Many types of metal oxide have been used in CNT/metal-oxide composites, such as tin oxide (SnO 2 ) [1], titanium dioxide (TiO 2 ) [2,3], manganese oxide (MnO 2 ) [4], tungsten trioxide (WO 3 ) [5], copper oxide [6,8], ruthenium dioxide (RuO 2 ) [7] and zinc oxide (ZnO) [9]. Many methods have been used to fabricate CNT/metal-oxide composites on substrates; for example, electrospinning [1], filtration [2], drop-coating [3], roll-pressing [4], spin-coating [5], inkjet printing [10], spray deposition [11], aerosol methods [12], electrophoretic deposition (EPD) [13,14], hot-pressing transfer [14] and filtration-wet transfer processes [15]. However, the use of the electrophoretic co-deposition method for the preparation of multi-wall carbon nanotube/cupric oxide/cuprous oxide (MWNT/CuO/Cu 2 O) nanocomposite films on a polyethylene terephthalate (PET) sheet for an angle sensor has not been reported.…”