Synthesis And Sensing Properties Of Two Dimensional Carbon Nanomaterials

With the improvement of people's living standards,people put forward higher requirements for sensors,such as more accurate response and better performance,the sensor material is the basis of sensor technology,no matter what kind of sensor must choose the appropriate material to make,this paper makes a detailed study of different types of sensors made of different types of sensor materials..Firstly,graphene oxide and tetraethyl orthosilicate were mixed in sealed glass ampoules and calcined at high temperature in vacuum to prepare silicon doped graphene nanosheets(Si GNS).The silicon atoms in the silicon doped graphene nanosheets successfully replace part of the carbon atoms in graphene,Carbon and silicon are covalently bonded,and the silicon hydroxyl groups on the silicon atoms still exist after calcination at high temperature,Si-doped graphene nanosheets exhibited excellent NO_x sensing ability with a high response value(21.5%–50 ppm of NO₂),a fast response(126 s),a fast recovery(378 s),a broad detectable concentration range(300 ppm?18 ppb)and outstanding selectivity.The doped Si atoms play a key role in NO_x sensing.The sensor prepared by Si GNS-400 detected NO_x not only in environments with a single harmful gas but also in complex environments containing several harmful gases.The detectable concentration range of the Si GNS-400 sensor decreased with increasing operating temperature.The as-prepared Si GNS exhibited excellent electrochemical detection ability to nitroaromatic compounds in 0.1 M phosphoric acid buffer solution(PBS,p H=8.0)via an electrochemical catalytic process.Five nitroaromatic compounds,including nitrobenzene,2-nitrotoluene,4-nitrotoluene,2,4-dinitrotoluene and 2,4,6-trinitrotoluene,were taken as the analyte to demonstrate the electrochemical catalytic ability of Si GNS.Density functional theory(DFT)calculation was carried out to explore the electrochemical catalytic mechanism of Si GNS.A hydrogen bond mediated electrochemical catalytic mechanism was proposed.Both the excellent electrical conductivity and the rich surface hydroxyl groups enhanced the electrochemical detection ability of Si GNS to nitroaromatic compounds.Si atoms in Si GNS played a key role for the excellent electrochemical detection ability of Si GNS due to most of the surface hydroxyl groups anchored on the Si atoms.The covalent triazine frameworks polymer(PCTF)was synthesized from p-benzenedicarbonamide in the presence of P₂O₅ as catalyst at 400?without water and oxygen.The PCTF has high specific surface area and porosity,which provides better conditions for the adsorption of gas molecules,The p CTF polymerized exhibited excellent NH₃ gas sensing ability with high response value,sensitivity and selectivity at room temperature.Nitrogen atoms from triazine rings served as the active sites for NH₃ adsorption,and then lead to electronic structure changing of p CTF,which resulted in a resistance decreasing of the sensor prepared by p CTF.In control experiments,the NH₃ sensing response value increased with the increasing of pyridinic nitrogen contents of the CTFs,which confirmed again that nitrogen atoms from triazine rings played the key role for the excellent NH₃ sensing ability.The density functional theory(DFT)calculations were employed to study the adsorptions of NH₃ and CO on a model molecule of p CTF fragment which contained six benzene rings and six triazine rings.The computational results indicated that the band gap of the model molecule of p CTF fragment narrowed slightly after NH₃adsorption and0.024 of electrons transferred from NH₃ to the model molecule of p CTF fragment according to the Mulliken charge distribution at 298.15 K.This results agreed well with the experimental results in which the sensor resistance decreased after NH₃molecule absorbed on.