Abstract
The accurate detection of NOx is an important issue, because nitrogen oxides are not only environmental pollutants, but also harm to human health. An array composed of two carbon nanotubes (CNTs)-based ionization sensors with different separations is proposed for NO and NO2 selective detection. The experimental results indicate that the CNTs-based ionization sensor has an intrinsic, monotonically decreasing response to NO or NO2. The sensor with 80 µm separations and 100 µm separations exhibited the highest sensitivity of −0.11 nA/ppm to 300 ppm NO and −0.49 nA /ppm to 70 ppm NO2, respectively. Although the effect of the NO2 concentration on the NO response is much stronger than that of NO on NO2, the array of these two sensors still exhibits the ability to simultaneously detect the concentrations of NO and NO2 in a gas mixture without component separation.
Highlights
The oxides of nitrogen, collectively termed as NOx and mainly regarding NO + NO2, are major atmospheric pollutants
One important use for carbon nanotubes (CNTs) is as a resistance sensor based on the change of electrical conductivity caused by gas adsorption and desorption
Almost all previously reported CNTs-based NOx gas sensors are based on this mechanism [6,14,15,16,17]
Summary
The oxides of nitrogen, collectively termed as NOx and mainly regarding NO + NO2, are major atmospheric pollutants. Due to the adsorption or desorption of gas molecules on the surface of metal oxides, the electrical conductivity of these sensors varies greatly with the changes in NOx concentration. One important use for CNTs is as a resistance sensor based on the change of electrical conductivity caused by gas adsorption and desorption. Almost all previously reported CNTs-based NOx gas sensors are based on this mechanism [6,14,15,16,17]. Another important application of CNTs is in a carbon nanotube field effect transistor (CNFET), which has characteristics that are affected by gas-induced changes of contact properties and by the doping level of the nanotube [18,19]. Wioenaaillzssoaotddieoemmnoosnnessntrtsaraotetrdesdthwtahitattthhtehdaeirfarfareryra,eywn,hwticehhliecchtrode separisatciioosmncospmo(ispneosdseeordtf oothffotFhsioegsuCe rNCeNT2-T)b,-abhsaeasdsedtihoionenizaizabatiitloiiontnyssteeonnsdsooirrrssecwwtliitythhdddiiisfffcfeerrriemenntitneelaeltecectrtborodedteweseespeeapnraaartainotyinosnd(siifn(fsienerrsetenrottf toyf pe of gas wFiigthuFoirgeuutr2ec),o2mh),apshoatnsheetnhetabsaielbpiitlyaitryatottioodnidr.ierHcetcletylryed,diwsiscecrriimumsiienndaattetehbebeeattwwrreeaeeynnoaafnntyywdodifisffeefernersenont trtsytpywepietohfo8fg0agsμamswiwtahniothduot1u0t0 μm separcaotmicoopnmosnpetoonntesnsiemtpsuaeprlataatrianotneioo.nHu. sHelryeer,edw,eweteeucustesadedntdhthedeaiarsrrtraianyygoouffittswwhooNsseeOnnssaoornrssdwwNiitthOh8280.0μGμmmasaansndedn10s10i0n0μgmμemsxepspeeaprraaimtriaoetninostnss were carrietodstoiomusutimlatautnlnteaonruemosluyaslldyaedtemectetocastnpadnhdedridseitsiatninngdguuisaihshrNeNlOaOtaiavnneddhNNuOOm22..iGGdaaitssysseeinnssitinnhggeeexrxappneergirmiemeonefnts2tsw1w.e1re–er2ec1acr.a9rir%erdieRoduHotu.attWate discunsseosnrnsstmehiotnareisvmliciattairtyvlomiabsttoysems-tbpswoeehstenpweehrsneeieetrtaniehvnetaidhtntyewadtbrwaoeerolgteaawlgtasiavteesieseve.nesh.hutumhmeiditdiwtiytoyinignatthsheeesrr.aannggee ooff 2211..11––2211..99%%RRHH. .WWeealaslosodidsicsucsusstshtehcerocsrso-ss-
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