| With the rise of graphene, two-dimensional( 2D) carbon and silicon nanomaterials generate a great interest in the fields of physics, materials, and chemistry as well as biology. As a result of the developments of nanoscience and advanced technology, a variety of novel 2D nanomaterials are discovered, such as the monolayer III-VA compounds, atomically thin arsenic and antimony. The physical and chemical properties of these 2D nanomaterials are quite different from their bulks. The novel properties due to the absence of the third dimension allow 2D nanomaterials to be applied in nano electronics and biology and other fields.Silicene consisting of silicon element has similar structure and electronic dispersion to graphene. Due to the ultra high carrier mobility originating from Dirac cone and good compatibility with industry of silicone, silicene is a promising candidate for working as future high-performance electronic and spintronic devices. Based on the first principles calculations, the stability and magnetic properties of transition metal atoms from Sc to Zn that are embedded into a single vacancy and a double vacancies of silicene are systematically studied. Sc, Ti and Co show the highest binding energies as high as 6 eV, while Zn has the lowest binding energy of about 2 eV. Silicene is a nonmagnetic 2D material. However, embedding the transition metal atoms(from V to Co) can effectively modulate the magnetic properties of silicene. Fe atom on single vacancy and Mn atom on double vacancy have the largest effective magnetic moment of more than 3 μB. Moreover, we find that doping of N or C atoms on defective site could greatly enhance the magnetism of system. It will be possible to design the silicene-based nano spintronics if inducing the magnetism, while the proper band gap is also necessary for the silicene to be used as device materials.A zero band gap of silicene results in an invalid off state of silicene based channel electronic devices, thus induces a low switch current ratio. In order to realize the application of silicene in field effect transistors, it is necessary to control the electronic structure of silicene and generate a band gap. Through the first principles calculations, we systematically study the influence of the single layer III-VA compounds on the structure and electronic properties of silicene. The III-VA compounds own planar structures. The heterojunction of silicene and monolayer III-VA compounds stacked by ring-to-ring is the most stable among all the stacked types. All of AlN, GaN, and GaP have a significant effect on silicene, generating an effective band gap ranging from 0.1 to 0.3 eV at the K point. The lattice of monolayer GaP matches best that of silicene, and the band gap can be continuously tuned if a perpendicular electric field is applied. These results provide a theoretical guidance for choosing a reasonable substrates during the growth of silicene, and may promote the expansive application of silicene in semiconductor nanodevices. Due to the instability of the silicene in the open air, better stability can be achieved by the hydrogenation, and a large band gap of 2.5 eV in silicene is accompanied. We have designed a 2D silicon-based material with continuously tunable band gap through partly dehydrogenating silicane. Combining with tight binding and density functional theory methods, we systematically investigate the structures and electronic properties of silicane through dehydrogenation in shapes of hexagonal, triangular, zigzag and armchair. Our calculations indicate that the dehydrogenation in hexagonal shape is not only the easiest to achieve, can but also continuously modulate the band gap in silicane.In recent years, a variety of the novel 2D nanomaterials, such as arsenene and antimonene reported in a recent experiment, have been found by both in theories and experiments. Both the arsenene and antimonene have the similar hexagonal structure as silicene. Due to their wide band gap, they are proposed to be used in optical devices in the future. We have studied the structures, formation energies, diffusions, electronic and magnetic properties of some typical point defects in arsenene and antimonene. We have considered several typical defects containing Stone-Wales defect, single vacancy(SV), double vacancies(DVs) and adatom. Two SV can coalesce into DVs by diffusion. The indirect band gap of antimonene can change into direct band gap when DVs(555|777) formed. And, the single vacancy and adatoms defects change the semiconducting materials to metal. Moreover, SV and adatoms defects can induce large magnetic moments. Our theoretical results provide valuable foundations for the growth and application of arsenene and antimonene in the future.Graphene is similar to silicene in both structure and band structure, and much more stable than the free standing silicene. Morever, it possesses excellent electronic properties and well biocompatibility Both of them can work as intelligent microelectronic devices, which are embedded into the biological bodies. As we know, protein is the basic minimal unit for a life, so it is critical to reveal the interaction mechanism between nanomaterials and the biological proteins is the crux. From the theoretical results, chymotrypsin(ChT) can be adsorbed on graphene and graphene oxide(GO) surfaces with different curvature. By the cationic and hydrophobic residues, the enzyme adsorbed on the GO surface which makes the GO as an efficient inhibitor for ChT, and the mechanism of the inhibition of GO on ChT was systematically investigated. At the same time, we also find that GO has a similar effect on trypsin. By using molecular dynamics method, we extensively study the effect of the silicon nanoparticles with the size radius of 4 nm and 11 nm on several enzymes(including cytochrome C, RNase A and lysozyme) about orientation and adsorption. Our results show that both of these three enzymes can be adsorbed on the surface of silicon nanoparticle, which will introduce greater structural stability. We also further explore the influences of different chemical groups(-OH,-COOH,-NH2, CH3) coated silicon nanoparticles on the cytochrome C. Our molecular dynamics results indicate that the selective interaction is existed between the silicon nanoparticles and the enzyme.In this paper, we have systematically studied silicene, silicane, graphene, GO, silicon quantum dots, arsenene and antimonene nanomaterials by first principles calculations. We explore the mechanisms between their structural stability and properties, and probe the ways to enhance their performance. Our results broad the applications of these nanomaterials in optoelectronic devices and biomedical fields. |
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