Direct Solvothermal Synthesis of B/N‐Doped Graphene

Heteroatom‐doping into graphitic networks has been utilized for opening the band gap of graphene. However, boron‐doping into the graphitic framework is extremely limited, whereas nitrogen‐doping is relatively feasible. Herein, boron/nitrogen co‐doped graphene (BCN‐graphene) is directly synthesized from the reaction of CCl₄, BBr₃, and N₂ in the presence of potassium. The resultant BCN‐graphene has boron and nitrogen contents of 2.38 and 2.66 atom %, respectively, and displays good dispersion stability in N‐methyl‐2‐pyrrolidone, allowing for solution casting fabrication of a field‐effect transistor. The device displays an on/off ratio of 10.7 with an optical band gap of 3.3 eV. Considering the scalability of the production method and the benefits of solution processability, BCN‐graphene has high potential for many practical applications.     

Hybrid Density Functional Study on Mono‐ and Codoped NaNbO3 for Visible‐Light Photocatalysis

Monodoping with Mo, Cr, and N atoms, and codoping with Mo?N and Cr?N atom pairs, are utilized to adjust the band structure of NaNbO₃, so that NaNbO₃ can effectively make use of visible light for the photocatalytic decomposition of water into hydrogen and oxygen, as determined by using the hybrid density functional. Codoping is energetically favorable compared with the corresponding monodoping, due to strong Coulombic interactions between the dopants and other atoms, and the effective band gap and stability for codoped systems increase with decreasing dopant concentration and the distance between dopants. The molybdenum, chromium, and nitrogen monodoped systems, as well as chromium–nitrogen codoped systems, are unsuitable for the photocatalytic decomposition of water by using visible light, because defects introduced by monodoping or the presence of unoccupied states above the Fermi level, which promotes electron–hole recombination processes, suppress their photocatalytic performance. The Mo?N codoped NaNbO₃ sample is a promising photocatalyst for the decomposition of water by using visible light because Mo?N codoping can reduce the band gap to a suitable value with respect to the water redox level without introducing unoccupied states.     

Direct Observation of Atomic Dynamics and Silicon Doping at a Topological Defect in Graphene

Chemical decoration of defects is an effective way to functionalize graphene and to study mechanisms of their interaction with environment. We monitored dynamic atomic processes during the formation of a rotary Si trimer in monolayer graphene using an aberration‐corrected scanning‐transmission electron microscope. An incoming Si atom competed with and replaced a metastable C dimer next to a pair of Si substitutional atoms at a topological defect in graphene, producing a Si trimer. Other atomic events including removal of single C atoms, incorporation and relocation of a C dimer, reversible C? C bond rotation, and vibration of Si atoms occurred before the final formation of the Si trimer. Theoretical calculations indicate that it requires 2.0 eV to rotate the Si trimer. Our real‐time results provide insight with atomic precision for reaction dynamics during chemical doping at defects in graphene, which have implications for defect nanoengineering of graphene.     

A first principle study of adsorption of two proximate nitrogen atoms on graphene

Different possible configurations of two nitrogen‐adatoms on graphene are studied using density functional theory. Adsorption of single nitrogen atom on the bridge site of graphene is accompanied by distortion of the sheet. Electronically, this case amounts to p‐type doping. Two N atoms adsorbed on the graphene sheet can share a bond in two ways. They acquire positions either just above two adjacent carbon atoms or they form a bridge across opposite bonds of a hexagon in the sheet. Both these configurations also induce structural distortion of the sheet. Another stable configuration consists of two N atoms bonded as an N₂ molecule physisorbed on the graphene sheet. It is also possible to adsorb two N atoms on opposite sides of the graphene sheet, bonded to the same two C atoms. Moreover, two N atoms can be individually adsorbed on alternate bridge sites of neighboring hexagons experiencing a repulsion, the energy for which arises from the additional distortion of the graphene sheet. The densities of states near the Fermi level are found to be dependent on the adsorption configurations of two nitrogen atoms on graphene. Thus the electronic properties of graphene can be controlled by the selective adsorption of two nitrogen atoms. © 2014 Wiley Periodicals, Inc.     

Adsorption of nitrogen oxides on graphene and graphene oxides: insights from density functional calculations

The interactions of nitrogen oxides NO(x) (x = 1,2,3) and N(2)O(4) with graphene and graphene oxides (GOs) were studied by the density functional theory. Optimized geometries, binding energies, and electronic structures of the gas molecule-adsorbed graphene and GO were determined on the basis of first-principles calculations. The adsorption of nitrogen oxides on GO is generally stronger than that on graphene due to the presence of the active defect sites, such as the hydroxyl and carbonyl functional groups and the carbon atom near these groups. These active defect sites increase the binding energies and enhance charge transfers from nitrogen oxides to GO, eventually leading to the chemisorption of gas molecules and the doping character transition from acceptor to donor for NO(2) and NO. The interaction of nitrogen oxides with GO with various functional groups can result in the formation of hydrogen bonds OH???O (N) between -OH and nitrogen oxides and new weak covalent bonds C???N and C???O, as well as the H abstraction to form nitrous acid- and nitric acidlike moieties. The spin-polarized density of states reveals a strong hybridization of frontier orbitals of NO(2) and NO(3) with the electronic states around the Fermi level of GO, and gives rise to the strong acceptor doping by these molecules and remarkable charge transfers from molecules to GO, compared to NO and N(2)O(4) adsorptions on GO. The calculated results show good agreement with experimental observations.     

Facile One‐Pot,One‐Step Synthesis of a Carbon Nanoarchitecture for an Advanced Multifunctonal Electrocatalyst

A one‐pot/one‐step synthesis strategy was developed for the preparation of a nitrogen‐doped carbon nanoarchitecture with graphene‐nanosheet growth on the inner surface of carbon nanotubes (CNTs). The N‐graphene/CNT hybrids exhibit outstanding electrocatalytic activity for several important electrochemical reactions as a result of their unique morphology and defect structures, such as high but uniform nitrogen doping, graphene insertion into CNTs, considerable surface area, and the presence of iron nanoparticles. The high‐yield synthetic process features high efficiency, low‐cost, straightforward operation, and simple equipment.     

Facile One‐Pot,One‐Step Synthesis of a Carbon Nanoarchitecture for an Advanced Multifunctonal Electrocatalyst

A one‐pot/one‐step synthesis strategy was developed for the preparation of a nitrogen‐doped carbon nanoarchitecture with graphene‐nanosheet growth on the inner surface of carbon nanotubes (CNTs). The N‐graphene/CNT hybrids exhibit outstanding electrocatalytic activity for several important electrochemical reactions as a result of their unique morphology and defect structures, such as high but uniform nitrogen doping, graphene insertion into CNTs, considerable surface area, and the presence of iron nanoparticles. The high‐yield synthetic process features high efficiency, low‐cost, straightforward operation, and simple equipment.     

Doping the Backbone of π‐Conjugated Polymers with Tricoordinate Boron: Synthetic Strategies and Emerging Applications

The doping of π‐conjugated organic compounds with trivalent boron atoms produces materials with intriguing properties and functions that result from the interaction of the π‐electron system with the vacant p orbital on boron. This offers unique opportunities in various applications such as organic (opto)electronics, biomedical imaging, and sensors for physiologically relevant anions or amines, as demonstrated by numerous examples on the molecular scale. Recently, the B‐doping strategy has been expanded to polymer chemistry with a view to benefit from the best of both worlds. Herein, recent advances in the synthesis of π‐conjugated polymers doped with tricoordinate boron in the backbone are reviewed. Selected applications are described where these functional materials have already been successfully implemented.     

Fullerene‐Based Macro‐Heterocycle Prepared through Selective Incorporation of Three N and Two O Atoms into C60

A 14‐membered heterocycle is created on the C₆₀ cage skeleton through a multistep procedure. Key steps involve repeated PCl₅‐induced hydroxylamino N?O bond cleavage leading to insertion of nitrogen atoms, and also piperidine‐induced peroxo O?O bond cleavage leading to insertion of oxygen atoms. The hetero atoms form one pyrrole, two pyran, and one diazepine rings in conjunction with the C₆₀ skeleton carbon atoms. The fullerene‐based macrocycle showed unique reactivities towards fluoride ion and copper salts.     

Nitrogen‐Doped Carbon Nanomaterials: Synthesis,Characteristics and Applications

Nonmetallic carbon‐based nanomaterials (CNMs) are important in various potential applications, especially after the emergence of graphene and carbon nanotubes, which demonstrate outstanding properties arising from their unique nanostructures. The pristine graphitic structure of CNMs consists of sp² hybrid C?C bonds and is considered to be neutral in nature with low wettability and poor reactivity. To improve its compatibility with other materials and, hence, for greater applicability, CNMs are generally required to be functionalized effectively and/or doped with heteroatoms in their graphitic frameworks for feasible interfacial interactions. Among the various possible functional/doping elements, nitrogen (N) atoms have received much attention given their potential to fine tune the intrinsic properties, such as the work‐function, charge carrier concentration, surface energy, and polarization, of CNMs. N‐doping improves the surface energy and reactivity with enhanced charge polarization and minimal damage to carbon frameworks. The modified surface energy and chemical activity of N‐doped carbon nanomaterials (NCNMs) can be useful for a broad range of applications, including fuel cells, solar cells, Li‐ion batteries, supercapacitors, chemical catalysts, catalyst supports, and so forth.     

Electronic and magnetic properties of all 3d transition‐metal‐doped ZnO monolayers

Stable geometries, electronic structures, and magnetic properties of the ZnO monolayer doped with 3d transition‐metal (TM) (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) atoms substituting the cation Zn have been investigated using first‐principles pseudopotential plane wave method within density functional theory (DFT). It is found that these nine atomic species can be effectively doped in the ZnO monolayer with formation energies ranging from ?6.319 to ?0.132 eV. Furthermore, electronic structures and magnetic properties of ZnO monolayer can be modified by such doping. The results show that the doping of Cr, Mn, Fe, Co, Ni, and Cu atoms can induce magnetization, while no magnetism is observed when Sc, Ti, and V atoms are doped into the ZnO monolayer. The magnetic moment is mainly due to the strong p–d mixing of O and TM (Cr, Mn, Fe, Co, Ni, and Cu) orbitals. These results are potentially useful for spintronic applications and the development of magnetic nanostructures. © 2013 Wiley Periodicals, Inc.     

富勒烯C_(36)等电子体C_(34)BN异构体的结构及其相对稳定性理论研究

用半经验的AM1和MNDO方法优化了富勒烯C_(36)的等电子体C_(34)BN所有可能 异构体的构型,分析了各异构体相对稳定性与杂原子取代位置间的关系。另外,比 较了C_(36)碳笼上同位置地取代杂原子形成的C_34BN,C_(34)B_2和C_(34)N_2间的 电子结构,并分析了C_(34)BN最稳定异构体的振动模型。结果表明以C_(36):A (D_(6h))为母体形成的最稳定C_(34)BN异构体对应于碳笼赤道位置六元环中1,4- 取代产物,而以C_(36):B(D_(2d))为母体形成的最稳定C_(34)BN异构体对应于碳笼 近赤道位置的1,2-取代产物.C_(34)BN各异构体的稳定性可能主要由体系的共轭性 质决定。前线轨道能级表明B,N原子取代所得异构体的氧化-还原活性按以下顺序 递增：C_(34)B_2相似文献   

A comparative study of open‐close and related rotamers methods to evaluate the intramolecular hydrogen bond energies in 3‐imino‐propen‐1‐ol and its derivatives

MP2 study of O? H…N intramolecular hydrogen bond (IMHB) in 3‐imino‐propen‐1‐ol and its derivatives were performed and their IMHB energies were obtained using the related rotamers and open‐close methods. Also the topological properties of electron density distribution and charge transfer energy associated with IMHB were gained by quantum theory of atoms in molecules and natural bond orbital theory, respectively. The computational results reveal that the related rotamers method energies are well correlates with geometrical parameters, topological parameters at hydrogen bond and ring critical points, integrated properties, proton transfer barrier and charge transfer energy of O? H…N unit. Surprisingly, it was found that the open‐close hydrogen bond energies cannot represent good linear correlations with these parameters. Consequently, we extrapolate a number of equations that can be used in estimation of O? H…N IMHB energy in complex biological systems. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Halogen‐ and Hydrogen‐Bonded Salts and Co‐crystals Formed from 4‐Halo‐2,3,5,6‐tetrafluorophenol and Cyclic Secondary and Tertiary Amines: Orthogonal and Non‐orthogonal Halogen and Hydrogen Bonding,and Synthetic Analogues of Halogen‐Bonded Biological Systems

Co‐crystallisation of, in particular, 4‐iodotetrafluorophenol with a series of secondary and tertiary cyclic amines results in deprotonation of the phenol and formation of the corresponding ammonium phenate. Careful examination of the X‐ray single‐crystal structures shows that the phenate anion develops a C?O double bond and that the C?C bond lengths in the ring suggest a Meissenheimer‐like delocalisation. This delocalisation is supported by the geometry of the phenate anion optimised at the MP2(Full) level of theory within the aug‐cc‐pVDZ basis (aug‐cc‐pVDZ‐PP on I) and by natural bond orbital (NBO) analyses. With sp² hybridisation at the phenate oxygen atom, there is strong preference for the formation of two non‐covalent interactions with the oxygen sp² lone pairs and, in the case of secondary amines, this occurs through hydrogen bonding to the ammonium hydrogen atoms. However, where tertiary amines are concerned, there are insufficient hydrogen atoms available and so an electrophilic iodine atom from a neighbouring 4‐iodotetrafluorophenate group forms an I???O halogen bond to give the second interaction. However, in some co‐crystals with secondary amines, it is also found that in addition to the two hydrogen bonds forming with the phenate oxygen sp² lone pairs, there is an additional intermolecular I???O halogen bond in which the electrophilic iodine atom interacts with the C?O π‐system. All attempts to reproduce this behaviour with 4‐bromotetrafluorophenol were unsuccessful. These structural motifs are significant as they reproduce extremely well, in low‐molar‐mass synthetic systems, motifs found by Ho and co‐workers when examining halogen‐bonding interactions in biological systems. The analogy is cemented through the structures of co‐crystals of 1,4‐diiodotetrafluorobenzene with acetamide and with N‐methylbenzamide, which, as designed models, demonstrate the orthogonality of hydrogen and halogen bonding proposed in Ho’s biological study.     

Controlled Synthesis of a Vacancy‐Defect Single‐Atom Catalyst for Boosting CO2 Electroreduction

The reaction of precursors containing both nitrogen and oxygen atoms with Ni^II under 500 °C can generate a N/O mixing coordinated Ni‐N₃O single‐atom catalyst (SAC) in which the oxygen atom can be gradually removed under high temperature due to the weaker Ni?O interaction, resulting in a vacancy‐defect Ni‐N₃‐V SAC at Ni site under 800 °C. For the reaction of Ni^II with the precursor simply containing nitrogen atoms, only a no‐vacancy‐defect Ni‐N₄ SAC was obtained. Experimental and DFT calculations reveal that the presence of a vacancy‐defect in Ni‐N₃‐V SAC can dramatically boost the electrocatalytic activity for CO₂ reduction, with extremely high CO₂ reduction current density of 65 mA cm^?2 and high Faradaic efficiency over 90 % at ?0.9 V vs. RHE, as well as a record high turnover frequency of 1.35×10⁵ h^?1, much higher than those of Ni‐N₄ SAC, and being one of the best reported electrocatalysts for CO₂‐to‐CO conversion to date.     

Half-metallicity in undoped and boron doped graphene nanoribbons in the presence of semilocal exchange-correlation interactions

We perform density functional calculations on one-dimensional zigzag edge graphene nanoribbons (ZGNRs) of different widths, with and without edge doping including semilocal exchange correlations. Our study reveals that, although the ground state of edge-passivated (with hydrogen) ZGNRs prefers to be anti-ferromagnetic, the doping of both of the edges with boron atoms stabilizes the system in a ferromagnetic ground state. Both the local and semilocal exchange correlations result in half-metallicity in edge-passivated ZGNRs at a finite cross-ribbon electric field. However, the ZGNR with boron edges shows half-metallic behavior irrespective of the ribbon width even in the absence of electric field and this property sustains for any field strength, opening a huge possibility of applications in spintronics.     

Observation of Transition‐Metal–Boron Triple Bonds in IrB2O− and ReB2O−

Multiple bonds between boron and transition metals are known in many borylene (:BR) complexes via metal d_π→BR back‐donation, despite the electron deficiency of boron. An electron‐precise metal–boron triple bond was first observed in BiB₂O^? [Bi≡B?B≡O]^? in which both boron atoms can be viewed as sp‐hybridized and the [B?BO]^? fragment is isoelectronic to a carbyne (CR). To search for the first electron‐precise transition‐metal‐boron triple‐bond species, we have produced IrB₂O^? and ReB₂O^? and investigated them by photoelectron spectroscopy and quantum‐chemical calculations. The results allow to elucidate the structures and bonding in the two clusters. We find IrB₂O^? has a closed‐shell bent structure (C_s, ¹A′) with BO^? coordinated to an Ir≡B unit, (^?OB)Ir≡B, whereas ReB₂O^? is linear (C_∞v, ³Σ^?) with an electron‐precise Re≡B triple bond, [Re≡B?B≡O]^?. The results suggest the intriguing possibility of synthesizing compounds with electron‐precise M≡B triple bonds analogous to classical carbyne systems.     

First-principles study of electronic and magnetic properties of transition metal adsorbed h-BNC2 sheets

Adsorption of Fe, Co and Ni atoms on a hybrid hexagonal sheet of graphene and boron nitride is studied using density functional methods. Most favorable adsorption sites for these adatoms are identified for different widths of the graphene and boron nitride regions. Electronic structure and magnetic properties of the TM-adsorbed sheets are then studied in detail. The TM atoms change the electronic structure of the sheet significantly, and the resulting system can be a magnetic semiconductor, semi-metal, or a non-magnetic semiconductor depending on the TM chosen. This gives tunability of properties which can be useful in novel electronics applications. Finally, barriers for diffusion of the adatoms on the sheet are calculated, and their tendency to agglomerate on the sheet is estimated.     

Adsorption of polyfunctional 5‐fluorouracil and 2,4‐dithio‐5‐fluorouracil on Au(111) surface: Structure,energy, and electronic transmission

Adsorption of 5‐fluorouracil (5‐FU) and 2,4‐dithio‐5‐fluorouracil (2,4‐DT‐5‐FU) on Au(111) surface at low coverage is studied by using periodic‐slab‐density functional theory calculation. Isolated 5‐FU molecule adsorbs preferentially at bridge site in a vertical configuration via N? H group by forming the N? H···Au nonconventional H‐bond. The formation of the anchor Au? O bond is not observed. Substitution of oxygen atoms of 5‐FU with sulfur strongly influences the nature of adsorption and leads to the Au? S anchor bond and the N? H···Au nonconventional H‐bond of single 2,4‐DT‐5‐FU molecule on Au(111) surface. The adsorption site and orientation of 2,4‐DT‐5‐FU molecule on the surface are similar to those of 5‐FU. The metal–molecule coupling effects at asymmetric Au/S(N? H)S/mol/C? H/Au and Au/N? H/mol/O/Au transport junctions and symmetric Au/S(N? H)S/mol/mol/S(N? H)S/Au and Au/O/mol/mol/O/Au transport junctions are also investigated. The electronic structure is analyzed in detail, and the obtained results are used for illustrating the electron transmission in metal–molecule–metal systems. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Mild and Complete Carbonyl Ligand Scission on a Mononuclear Transition Metal Complex

The complete scission of the carbon–oxygen bond of carbon monoxide, while frequently observed on bulk metals and with bimetallic and cluster transition metal complexes, is unknown with monometallic systems. Reaction of a zerovalent iron bis(borylene) complex with a cyclic (alkyl)(amino)carbene revealed a highly selective intramolecular cleavage of the C?O bond of a carbonyl ligand at room temperature, leading to the formation of a highly unusual iron complex containing a base‐stabilized (bora)alkylideneborane ligand. DFT investigation of the reaction mechanism suggested that the two Lewis acidic borylene boron atoms cooperate to cleave the C?O multiple bond.