Abstract
Toluene is extensively used in many industrial products, which needs to be effectively detected by sensitive gas sensors even at low-ppm-level concentrations. Here, NiFe2O4 nano-octahedrons were calcinated from NiFe-bimetallic metal-organic framework (MOFs) octahedrons synthesized by a facile refluxing method. The co-existence of p-Phthalic acid (PTA) and 3,3-diaminobenzidine (DAB) promotes the formation of smooth NiFe-bimetallic MOFs octahedrons. After subsequent thermal treatment, a big weight loss (about 85%) transformed NiFe2O4 nanoparticles (30 nm) into NiFe2O4 porous nano-octahedrons with hollow interiors. The NiFe2O4 nano-octahedron based sensor exhibited excellent gas sensing properties for toluene with a nice stability, fast response, and recovery time (25 s/40 s to 100 ppm toluene), and a lower detection limitation (1 ppm) at 260 °C. The excellent toluene-sensing properties can not only be derived from the hollow interiors combined with porous nano-octahedrons to favor the diffusion of gas molecules, but also from the efficient catalytic activity of NiFe2O4 nanoparticles.
Highlights
Toluene is one kind of a colorless substance with a unique aromatic odor that is widely used in commercial products and industrial applications
The octahedron NiFe-bimetallic MOFs were synthesized through a refluxing method, as schematically shown in Figure 1, which were further transferred into NiFe2O4 with thermal treatment
NiFe-bimetallic MOFs octahedrons were synthesized by a simple refluxing method, as scNheiFmea-btiicmaleltyalslhicowMnOiFns Foigcutarhee1d,rownhsicwh ewreassuysnetdheasiszethde bseylf-asascirmifipclieal rteefmlupxliantge fmoretNhioFde,2Oa4s fsacbhreimcaatitoicna.llIyt isshcloewarnthiant uFnigifuorrem1N, iwFeh-iMchOFwsaosctuahseeddroansstwheeresewlfe-slla-cdreififincieadl wteimthpalnataeveforargNe siFizee2Oof4 afabboruicta3t0io0nn. mIt,isasclsehaorwthnaitnutnhiefoirnmseNt oiFf eF-iMguOreFs2ao.ctCalhoesderoobnssewrvearteiownerlel-vdeeafliendedthwatitthheasneaNvieFrea-gMe OsiFzes oocf taabhoeudtr3o0n0snwme,raesssmhoowotnhionnthteheinssuetrfoafcFei.guTrhee2aas.-CplroespeaorebdseNrviaFteio-Mn rOeFvseaolcetdahtheadtrtohnessewNeirFeef-uMrtOhFesr tohcetarmheadlrlyontsrawnsefroermsmedooitnhtoonNitFhee2Osu4rfnaacne.o-Tohcetaahse-dprroenpsariendaNn iaFier-MatOmFosspohcetarheeadtroanhsewateinreg fruarttehoerf thermally transformed into NiFe2O4 nano-octahedrons in an air atmosphere at a heating rate of 3 °C/min
Summary
Toluene is one kind of a colorless substance with a unique aromatic odor that is widely used in commercial products and industrial applications. Toluene is seriously harmful to human health as it strongly affects the nervous system to induce brain function disturbances and damage to the kidneys or liver [1,2]. Due to the harmful effects of toluene, it is of great urgency to be able to effectively detect toluene. Resistive-based gas sensors on a metal oxide base are the most attractive with respect to their cost-effective, versatile, and simple fabrication techniques. Many p-type oxide semiconductors such as NiO [8], CuO [9], Co3O4 [10], Cr2O3 [11], Mn3O4 [12], and so on have been reported to have potential for gas sensors, it is still far less than their counterpart, n-type oxide semiconductors
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