Density Functional Theory Study On Structure And Property Of Modified Low-dimensional Carbon Materials

Due to their unique optical, electrical and mechanical properties,low–dimensional carbon materials are attractive to a variety of researchfields and have already exhibited promising applications in lots of fieldssuch as gas sensors, hydrogen storage and catalysis. Recently, modulatingthe electronic properties of low–dimensional carbon materials has alreadybecome one of hot topics of chemists especially theorists. Therefore, basedon density functional theory, we investigate the electronic structures andproperties of silicon carbide nanotubes physically modified by externalelectric field and graphene chemically modified by hydroxyl so as to get asuitable strategy to enhance the performance of low–dimensional carbonmaterials.First, we explore the possibility of using （5,5） silicon carbidenanotube （SiCNT） with an external electric field （EF） as a potential gassensor for SO₂detection. Without EF, SO₂molecules can be chemisorbedto SiCNT, but can not essentially change the electronic properties of SiCNT.Nevertheless, it is interesting that SiCNT can not only adsorb SO₂molecule, but also transform from a semiconductor to a conductor. Through asystematic study, we discover that it is these broken S–C bonds that inducea decrease in the band gap. Furthermore, with the concentration of SO₂exceeding20%, the band gap of SiCNT under an EF of9.00V.nm1wouldbe reduced from1.75eV for SiCNT to zero. Hence, with an appropriate EF,SiCNTs can effectively respond to SO₂and serve as sensors for detectingSO₂gas.Second, we investigate the geometric and electronic properties of（OH）_n（n=1–6） adsorbed on the pristine graphene. Our study shows thathydroxyl pairs on neighboring carbon in either the opposite or the sameside are very stable species because of hydrogen bond. On the other hand, apart of the carbon atoms of the hydroxylated graphene change from sp²tosp³, which is one of the reasons of forming stable configurations.Furthermore, band structure and DOS demonstrate that the electronicstructure of graphene modified by hydroxyl is greatly changed,transforming from a zero gap semiconductor to a narrow-bandsemiconductor. Hence, we can modify the electronic structure of graphenethrough hydroxylation.