A Hybrid of Corannulene and Azacorannulene: Synthesis of a Highly Curved Nitrogen‐Containing Buckybowl

A highly curved nitrogen‐containing buckybowl, which can be considered as a corannulene/azacorannulene hybrid, was synthesized and characterized. This molecule has a polycyclic aromatic C₄₀N core, corresponding to a partial azafullerene structure C_80−xN_x (x=1,2,3…), and exhibits interesting properties that arise from its large and highly curved π surface and the embedded nitrogen atom, which include association with C₆₀, a lower LUMO level relative to azapentabenzocorannulene, and the formation of a radical cationic species upon oxidation.     

New Insights into the Band‐Gap Narrowing of (N,P)‐Codoped TiO2 from Hybrid Density Functional Theory Calculations

The electronic properties of anatase‐TiO₂ codoped by N and P at different concentrations have been investigated via generalized Kohn–Sham theory with the Heyd–Scuseria–Ernzerhof (HSE06) hybrid functional for exchange‐correlation in the context of density functional theory. At high doping concentrations, we find that the high photocatalytic activity of (N, P)‐codoped anatase TiO₂ vis‐à‐vis the N‐monodoped case can be rationalized by a double‐hole‐mediated coupling mechanism [Yin et al., Phys. Rev. Lett. 2011, 106, 066801] via the formation of an effective N? P bond. On the other hand, Ti³⁺ and Ti⁴⁺ ions’ spin double‐exchange results in more substantial gap narrowing for larger separations between N and P atoms. At low doping concentrations, double‐hole‐coupling is dominant, regardless of the N? P distance.     

First‐Principles Calculations on Electronic Structures of N/V‐Doped and N‐V‐Dodoped Anatase TiO2 (101) Surfaces

The energetic and electronic properties of N/V‐doped and N‐V‐codoped anatase TiO₂ (101) surfaces are investigated by first‐principles calculations, with the aim to elucidate the relationship between the electronic structure and the photocatalytic performance of N‐V‐codoped TiO₂. Several substitutional and interstitial configurations for the N and/or V impurities in the bulk phase and on the surface are studied, and the relative stability of different doping configurations is compared by the impurity formation energy. Systematic calculations reveal that N and V impurities can be encapsulated by TiO₂ to form stable structures as a result of strong N‐V interactions both in the bulk and the surface model. Through analyzing and comparing the electronic structures of different doping systems, the synergistic doping effects are discussed in detail. Based on these discussions, we suggest that N_OV_Ti codoping cannot only narrow the band gap of anatase TiO₂, but also forms impurity states, which are propitious for the separation of photoexcited electron–hole pairs. In the case of N_OV_Ti‐codoped TiO₂ (101) surfaces, this phenomenon is especially prominent. Finally, a feasible synthesis route for N_OV_Ti codoping into anatase TiO₂ is proposed.     

Synergistic Enhancement of Electrocatalytic Activity toward Oxygen Reduction Reaction in Alkaline Electrolytes with Pentabasic (Fe,B, N,S, P)‐Doped Reduced Graphene Oxide

As alternatives to Pt‐based electrocatalysts, the development of nonprecious metal catalysts with high performance in the cathodic oxygen reduction reaction (ORR) is highly desirable for widespread use in fuel cells. Here we report a simple approach for preparing pentabasic (Fe, B, N, S, P)‐doped reduced graphene oxide (rGO) via a two‐step doping method of adding boric acid and ferric chloride to ternary (N, S, P)‐doped rGO (NSPG). Electrochemical investigation of the composites for the ORR revealed that simultaneously doping appropriate amounts of Fe and B into the NSPG produced a synergistic effect that endowed the prepared catalyst with both a positively shifted ORR half‐wave potential and high selectivity for the 4e^? reduction of O₂. The optimized Fe₂B‐NSPG catalyst approached a 4e^? process for the ORR with a half‐wave potential (E_1/2=0.90 V vs. RHE) even 30 mV higher than that of the commercial Pt/C catalyst in alkaline solution. Furthermore, relative to the Pt/C catalyst, the Fe₂B‐NSPG demonstrated superior stability and excellent tolerance of the methanol cross‐over effect. This simple method afforded pentabasic (Fe, B, N, S, P)‐doped rGO as a promising nonprecious metal catalyst used for alkaline fuel cells.     

Unveiling 79‐Year‐Old Ixene and Its BN‐Doped Derivative

Polycyclic aromatic hydrocarbons (PAHs) are key components of organic electronics. The electronic properties of these carbon‐rich materials can be controlled through doping with heteroatoms such as B and N, however, few convenient syntheses of BN‐doped PAHs have been reported. Described herein is the rationally designed, two‐step syntheses of previously unknown ixene and BN‐doped ixene (B₂N₂‐ixene), and their characterizations. Compared to ixene, B₂N₂‐ixene absorbs longer‐wavelength light and has a smaller electrochemical energy gap. In addition to its single‐crystal structure, scanning tunneling microscopy revealed that B₂N₂‐ixene adopts a nonplanar geometry on a Au(111) surface. The experimentally obtained electronic structure of B₂N₂‐ixene and the effect of BN‐doping were confirmed by DFT calculations. This synthesis enables the efficient and convenient construction of BN‐doped systems with extended π‐conjugation that can be used in versatile organic electronics applications.     

Photocatalytic Degradation of Glyphosate in Water by N‐Doped SnO2/TiO2 Thin‐Film‐Coated Glass Fibers

Photocatalytic degradation of glyphosate contaminated in water was investigated. The N‐doped SnO₂/TiO₂ films were prepared via sol–gel method, and coated on glass fibers by dipping method. The effects of nitrogen doping on coating morphology, physical properties and glyphosate degradation rates were experimentally determined. Main variable was the concentration of nitrogen doping in range 0–40 mol%. Nitrogen doping results in shifting the absorption wavelengths and narrowing the band gap energy those lead to enhancement of photocatalytic performance. The near optimal 20N/SnO₂/TiO₂ composite thin film exhibited about two‐ and four‐folds of glyphosate degradation rates compared to the undoped SnO₂/TiO₂ and TiO₂ films when photocatalytic treatment were performed under UV and solar irradiations, respectively, due to its narrowest band gap energy (optical absorption wavelength shifting to visible light region) and smallest crystallite size influenced by N‐doping.     

First‐Principles Study on Doping of SnSe2 Monolayers

Doping is a vitally important technique that can be used to modulate the properties of two‐dimensional materials. In this work, by using first‐principles density functional calculations, we investigated the electrical properties of SnSe₂ monolayers by p‐type/n‐type and isoelectronic doping. Substitution at Sn/Se sites was found to be easy if the monolayer was grown under Sn‐/Se‐poor conditions. Substitutions at Sn sites with metallic atoms (e.g. Ga, Ge, In, Bi, Sb, Pb) resulted in positive substitution energies, which indicated that they were not effective doping candidates. For substitutions at Se sites with nonmetallic atoms, no promising candidates were found for p‐type doping (e.g., N, P, As). Among these, N and As showed positive substitution energies. Although P had a negative substitution energy under Sn‐rich conditions, it introduced trap states within the band gap. For n‐type doping (e.g., F, Cl, Br), all the calculated substitution energies were negative under both Sn‐ and Se‐rich conditions. Br was proven to be a promising candidate, because the impurity introduced a shallow donor level. Finally, for isoelectronic doping (e.g., O, S, Te), the intrinsic semiconducting features of the SnSe₂ monolayer did not change, and the contribution from the impurity to the states near the band edge increased with the atomic number.     

Cu–N Dopants Boost Electron Transfer and Photooxidation Reactions of Carbon Dots

The broadband light‐absorption ability of carbon dots (CDs) has inspired their application in photocatalysis, however this has been impeded by poor electron transfer inside the CDs. Herein, we report the preparation of Cu–N‐doped CDs (Cu‐CDs) and investigate both the doping‐promoted electron transfer and the performance of the CDs in photooxidation reactions. The Cu–N doping was achieved through a one‐step pyrolytic synthesis of CDs with Na₂[Cu(EDTA)] as precursor. As confirmed by ESR, FTIR, and X‐ray photoelectron spectroscopies, the Cu species chelates with the carbon matrix through Cu–N complexes. As a result of the Cu–N doping, the electron‐accepting and ‐donating abilities were enhanced 2.5 and 1.5 times, and the electric conductivity was also increased to 171.8 μs cm^?1. As a result of these enhanced properties, the photocatalytic efficiency of CDs in the photooxidation reaction of 1,4‐dihydro‐2,6‐dimethylpyridine‐3,5‐dicarboxylate is improved 3.5‐fold after CD doping.     

Highly Curved Bowl‐Shaped Fragments of Fullerenes: Synthesis,Structural Analysis,and Physical Properties

Highly curved buckybowls 3 , 4 , and 5 were synthesized from planar precursors, fluoranthenes 8 , benzo[k]fluoranthenes 10 and naphtho[1,2‐k]‐cyclopenta[cd]fluoranthenes 12 , respectively, using straightforward palladium‐catalyzed cyclization reactions. These fluoranthene‐based starting materials were easily prepared from 1,8‐bis(arylethynyl)naphthalenes 6 . Both buckybowls 3 and 4 are fragments of C₆₀, whereas 5 is a unique subunit of C₇₀. The curved structures were identified by X‐ray crystallography, and they are deep bowls. The maximum π‐orbital axis vector (POAV) pyramidalization angle in both 3 and 4 is 12.8°. Such a high curvature is very rarely obtained. Buckybowls 5 are less curved than the others because they have a lower density of five‐membered rings, analogous to the tube portion of C₇₀. Cyclopentaannulation increases the bowl depths of 3 and 4 , but not the maximum POAV pyramidalization angle. Among the eight buckybowls studied herein, five form polar crystals. The bowl‐to‐bowl inversion dynamics of these buckybowls can be classified into two types; one has a planar transition structure, whereas the other has an S‐shaped transition structure. A larger longitudinal length of these buckybowls corresponds to a stronger preference for the latter. The photophysical properties of these buckybowls were examined and compared with those of C₆₀ and C₇₀. Buckybowls 5 have absorption bands at wavelengths greater than 450 nm, which are similar to those of C₇₀. The chiral resolution of the mono‐substituted buckybowl 4 ac was also studied by using HPLC with a chiral column.     

Thermally Driven Structure and Performance Evolution of Atomically Dispersed FeN4 Sites for Oxygen Reduction

FeN₄ moieties embedded in partially graphitized carbon are the most efficient platinum group metal free active sites for the oxygen reduction reaction in acidic proton‐exchange membrane fuel cells. However, their formation mechanisms have remained elusive for decades because the Fe?N bond formation process always convolutes with uncontrolled carbonization and nitrogen doping during high‐temperature treatment. Here, we elucidate the FeN₄ site formation mechanisms through hosting Fe ions into a nitrogen‐doped carbon followed by a controlled thermal activation. Among the studied hosts, the ZIF‐8‐derived nitrogen‐doped carbon is an ideal model with well‐defined nitrogen doping and porosity. This approach is able to deconvolute Fe?N bond formation from complex carbonization and nitrogen doping, which correlates Fe?N bond properties with the activity and stability of FeN₄ sites as a function of the thermal activation temperature.     

Study of Electronic,Optical Absorption and Emission in Pure and Metal‐Decorated Graphene Nanoribbons (C29H14‐X; X=Ni,Fe, Ti,Co+, Al+, Cu+): First Principles Calculations

Density functional theory (DFT) and time‐dependent density functional theory (TDDFT) calculations were performed with the basis sets 6‐31G for DFT and 6‐31G(d), 6‐31+G(d,p) for TDDFT on pure graphene nanoribbon (GNR) C₃₀H₁₄ and metal‐decorated C₂₉H₁₄‐X (MGNRs; X=Ni, Fe, Ti, Co⁺, Al⁺, and Cu⁺). The metal/carbon ratio (X:C 3.45 %) and the doping site were fixed. Electronic properties, that is, the dipole moment, binding energy, and HOMO–LUMO gaps, were calculated. The absorption and emission properties in the visible range (λ=400–720 nm) were determined. Optical gaps, absorption and emission wavelengths, oscillator strengths, and dominant transitions were calculated. Pure graphene was found to be the most stable form. However, of the MGNRs, C₂₉H₁₄?Co⁺ and C₂₉H₁₄?Al⁺ were found to be the most and least stable, respectively. All GNRs were found to have semiconducting nature. The optical absorption of pure graphene undergoes a shift on metal doping. Emission from the pure graphene followed Kasha′s rule, unlike the metal‐doped GNRs.     

Dual‐Doped Molybdenum Trioxide Nanowires: A Bifunctional Anode for Fiber‐Shaped Asymmetric Supercapacitors and Microbial Fuel Cells

A novel in situ N and low‐valence‐state Mo dual doping strategy was employed to significantly improve the conductivity, active‐site accessibility, and electrochemical stability of MoO₃, drastically boosting its electrochemical properties. Consequently, our optimized N‐MoO_3?x nanowires exhibited exceptional performances as a bifunctional anode material for both fiber‐shaped asymmetric supercapacitors (ASCs) and microbial fuel cells (MFCs). The flexible fiber‐shaped ASC and MFC device based on the N‐MoO_3?x anode could deliver an unprecedentedly high energy density of 2.29 mWh cm^?3 and a remarkable power density of 0.76 μW cm^?1, respectively. Such a bifunctional fiber‐shaped N‐MoO_3?x electrode opens the way to integrate the electricity generation and storage for self‐powered sources.     

Bonding characters of M‐Cd4Te4 and M‐Cd3Te3 (M = Cr,Cu, Ag,Al, Cd,and Zn) clusters

At DFT/B3LYP/LANL2DZ theoretical level, conformations, bonding characters and Molecular Orbital (MO) of M‐Cd₄Te₄ and M‐Cd₃Te₃ (M = Cr, Cu, Ag, Al, Cd, and Zn) molecules are investigated. First, through analysis of conformations and bonding characters, we conclude that different doping atoms have different influence on doping structures. Al atom can form bonding with Cd atoms in doping molecules. Besides, as for M‐Cd₄Te₄ and M‐Cd₃Te₃ structures, there are different characters and conformations as to the same doping atoms. Second, MO is used to discuss characters of bonding. We believe that doping atoms influence the orbital characters and make the transition change. Moreover, different conformations for the same doping atoms induce different transitions. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

A Nitrogen‐Doped Hexapole [7]Helicene versus Its All‐Carbon Analogue

Two synthetic nanographenes (NGs), N‐H7H and C‐H7H , were prepared. N‐H7H is doped with nitrogen, and C‐H7H is the all‐carbon analogue. Both are hexapole [7]helicenes (H7Hs), and their structures were identified by single‐crystal X‐ray diffraction. Sharp contrasts in absorption (^absλ_max, 683 vs. 593 nm), emission (^emλ_max, 894 vs. 777 nm), and electrochemical behavior (^oxE₁, 0.28 vs. 0.53 V) were observed between N‐H7H and C‐H7H , and the origin of these differences was rationalized by theoretical calculations. Studies on N‐H7H and C‐H7H set a clear example to elucidate the remarkable effects of N‐doping on the physical properties of NGs.     

Fulfilling the 2(N+1)2 Hirsch rule in smaller hollow fullerenes. Evaluation of long‐range magnetic behavior and NMR patterns of C28, , C24N4, and C28H4

The formation of different 32 π‐electron systems derived from a prominent small fullerene given by C₂₈, allows to evaluate several approaches ensuring an electronic shell closure in terms of the characteristic chemical shift anisotropy (CSA) and long‐range magnetic response properties for spherical aromatic compounds. Our results show that the inclusion of extra electrons and the doping of the cage, are able to sustain a long‐range shielding cone when an external field is oriented in a specific orientation. Such properties are inherent characteristics of spherical aromatic compounds, which are not obtained in the neutral C₂₈ fullerene, and in the exo‐bonded approach leading to C₂₈H₄. Thus, the doping of the cage is suggested as the most suitable approach to modify the overall count of electrons, leading to the expected response properties for further design of highly aromatic fullerenes.     

Modification of Hole Transport Layers for Fabricating High Performance Non‐fullerene Polymer Solar Cells

Interfacial engineering is expected to be a feasible strategy to improve the charge transport properties of the hole transport layer (HTL), which is of crucial importance to boost the device performance of organic solar cells (OSCs). In this study, two types of alcohol soluble materials, 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F₄‐TCNQ) and di‐tetrabutylammoniumcis–bis(isothiocyanato)bis (2,2’‐bipyridyl‐4,4’‐dicarboxylato) ruthenium(II) (N719) dye were selected as the dopant for HTL. The doping of F₄‐TCNQ and N719 dye in poly (ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) with and without integrating a graphene quantum‐dots (G‐QDs) layer has been explored in poly[[2,6′‐4‐8‐di(5‐ethylhexylthienyl)benzo[1,2‐b:3,3‐b]dithiophene][3‐fluoro‐2[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thio‐phenediyl:(2,2′‐((2Z,2′Z)‐(((4,4,9, 9‐tetrakis(4‐hexylphenyl)‐4,9‐dihydro‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis(4‐((2‐ethylhexyl)oxy)thiophene‐5,2‐diyl))bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (PTB7‐Th:IEICO‐4F) OSCs. The power conversion efficiency of the non‐fullerene OSCs has been increased to 10.12% from 8.84%. The influence of HTL modification on the nano‐morphological structures and photophysical properties is analyzed based on the comparative studies performed on the control and modified devices. The use of chemical doping and bilayer strategy optimizes the energy level alignment, nanomorphology, hole mobility, and work‐function of HTL, leading to considerable reduction of the leakage current and recombination losses. Our work demonstrates that the doping of HTL and the incorporation of G‐QDs layer to constitute a bilayer HTL is an promising strategy to fabricate high performance non‐fullerene polymer solar cells     

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.     

Nitrogen,Phosphorus, and Sulfur Co‐Doped Hollow Carbon Shell as Superior Metal‐Free Catalyst for Selective Oxidation of Aromatic Alkanes

Metal‐free heteroatom‐doped carbocatalysts with a high surface area are desirable for catalytic reactions. In this study, we found an efficient strategy to prepare nitrogen, phosphorus, and sulfur co‐doped hollow carbon shells (denote as NPS‐HCS) with a surface area of 1020 m² g^?1. Using a poly(cyclotriphosphazene‐co‐4,4′‐sulfonyldiphenol) (PZS) shell as carbon source and N, P, S‐doping source, and the ZIF‐67 core as structural template as well as extra N‐doping source, NPS‐HCS were obtained with a high surface area and superhydrophilicity. All these features render the prepared NPS‐HCS a superior metal‐free carbocatalyst for the selective oxidation of aromatic alkanes in aqueous solution. This study provides a reliable and facile route to prepare doped carbocatalysts with enhanced catalytic properties.     

Tungsten and nitrogen co‐doped TiO2 nanobelts with significant visible light photoactivity

Tungsten and nitrogen co‐doped TiO₂ nanobelts (W/N‐TNBs) have been successfully synthesized via 1‐step hydrothermal method. The structure, morphology, and composition of prepared samples were characterized by X‐ray diffraction, scanning electron microscopy, and X‐ray photoelectron spectroscopy, respectively. The prominent phase of all as‐prepared samples is anatase crystal. For samples with N doping, new energy states can be introduced on top of O 2p states which reduced the band gap by 1.1 eV. The reduced band gap leads to efficient visible light activity. The 3%‐W/N‐TNBs were found to exhibit the highest activity. The photocatalytic performance of 3%‐W/N‐TNBs under visible light is about 4.8 times than that of pure TiO₂ nanobelts, which emphasizes the synergistic effect of W and N co‐doping for effectively inhibiting the recombination of photogenerated electrons and holes. In addition, our results testify the different redox potentials of the photoelectrons at different final states.     

Nitrogen,Phosphorus, and Sulfur Co‐Doped Hollow Carbon Shell as Superior Metal‐Free Catalyst for Selective Oxidation of Aromatic Alkanes

Metal‐free heteroatom‐doped carbocatalysts with a high surface area are desirable for catalytic reactions. In this study, we found an efficient strategy to prepare nitrogen, phosphorus, and sulfur co‐doped hollow carbon shells (denote as NPS‐HCS) with a surface area of 1020 m² g⁻¹. Using a poly(cyclotriphosphazene‐co‐4,4′‐sulfonyldiphenol) (PZS) shell as carbon source and N, P, S‐doping source, and the ZIF‐67 core as structural template as well as extra N‐doping source, NPS‐HCS were obtained with a high surface area and superhydrophilicity. All these features render the prepared NPS‐HCS a superior metal‐free carbocatalyst for the selective oxidation of aromatic alkanes in aqueous solution. This study provides a reliable and facile route to prepare doped carbocatalysts with enhanced catalytic properties.