Graphene is an important material with potential application in spintronics. Edge-modified zigzag graphene nanoribbons (ZGNR) are investigated with density functional theory. The modifications are realized by saturating the dangling edge bonds by different terminal groups, such as H, NH2, NO2, and CH3. Such modification has a significant impact on the ZGNR electronic structure. Half-metallicity is observed when ZGNR is terminated by NO2 groups at one edge and by CH3 groups on the other side. Free energy analysis suggests that edge-modification is a practical way in experiment to realize half-metallicity.

Optoelectronic applications require materials both responsive to objective photons and able to transfer carriers, so new two-dimensional (2D) semiconductors with appropriate band gaps and high mobilities are highly desired. A broad range of band gaps and high mobilities of a 2D semiconductor family, composed of monolayer of Group 15 elements (phosphorene, arsenene, antimonene, bismuthene) is presented. The calculated binding energies and phonon band dispersions of 2D Group 15 allotropes exhibit thermodynamic stability. The energy band gaps of 2D semiconducting Group 15 monolayers cover a wide range from 0.36 to 2.62 eV, which are crucial for broadband photoresponse. Significantly, phosphorene, arsenene, and bismuthene possess carrier mobilities as high as several thousand cm(2)  V(-1)  s(-1) . Combining such broad band gaps and superior carrier mobilities, 2D Group 15 monolayers are promising candidates for nanoelectronics and optoelectronics.

Optoelectronic applications require materials both responsive to objective photons and able to transfer carriers,so new two-dimensional (2D) semiconductors with appropriate band gaps and high mobilities are highly desired. Ab road range of band gaps and high mobilities of a2Dsemiconductor family,c omposed of monolayer of Group 15 elements (phosphorene,arsenene,antimonene,bismuthene) is presented. The calculated binding energies and phonon band dispersions of 2D Group 15 allotropes exhibit thermodynamic stability.T he energy band gaps of 2D semiconducting Group 15 monolayers cover awide range from 0.36 to 2.62 eV,which are crucial for broadband photoresponse.S ignificantly,p hosphorene,a rsenene,a nd bismuthene possess carrier mobilities as high as several thousand cm 2 V À1 s À1 .Combining such broad band gaps and superior carrier mobilities,2 DG roup 15 monolayers are promising candidates for nanoelectronics and optoelectronics.

Metastable structural polymorphs can have superior properties and applications to their thermodynamically stable phases, but the rational synthesis of metastable phases is a challenge. Here, a new strategy for stabilizing metastable phases using surface functionalization is demonstrated using the example of formamidinium lead iodide (FAPbI) perovskite, which is metastable at room temperature (RT) but holds great promises in solar and light-emitting applications. We show that, through surface ligand functionalization during direct solution growth at RT, pure FAPbI in the cubic perovskite phase can be stabilized in nanostructures and thin films at RT without cation or anion alloying. Surface characterizations reveal that long-chain alkyl or aromatic ammonium (LA) cations bind to the surface of perovskite structure. Calculations show that such functionalization reduces the surface energy and plays a dominant role in stabilizing the metastable perovskite phase. Excellent photophysics and optically pumped lasing from the stabilized single-crystal FAPbI nanoplates with low thresholds were demonstrated. High-performance solar cells can be fabricated with such directly synthesized stabilized phase-pure FAPbI with a lower bandgap. Our results offer new insights on the surface chemistry of perovskite materials and provide a new strategy for stabilizing metastable perovskites and metastable polymorphs of solid materials in general.