Soft‐Templating Synthesis of N‐Doped Mesoporous Carbon Nanospheres for Enhanced Oxygen Reduction Reaction

The development of ordered mesoporous carbon materials with controllable structures and improved physicochemical properties by doping heteroatoms such as nitrogen into the carbon framework has attracted a lot of attention, especially in relation to energy storage and conversion. Herein, a series of nitrogen‐doped mesoporous carbon spheres (NMCs) was synthesized via a facile dual soft‐templating procedure by tuning the nitrogen content and carbonization temperature. Various physical and (electro)chemical properties of the NMCs have been comprehensively investigated to pave the way for a feasible design of nitrogen‐containing porous carbon materials. The optimized sample showed a favorable electrocatalytic activity as evidenced by a high kinetic current and positive onset potential for oxygen reduction reaction (ORR) due to its large surface area, high pore volume, good conductivity, and high nitrogen content, which make it a highly efficient ORR metal‐free catalyst in alkaline solutions.     

Cohesive‐Energy‐Resolved Bandgap of Nanoscale Graphene Derivatives

With a size‐dependent cohesive energy formula for two‐dimensional coordinated materials, the bandgap variation in quantum dots and nanoribbons of graphene derivatives, such as graphane, fluorographene and graphene oxides, is investigated. The bandgap is found to increase substantially as the diameter or width of the nano‐sized material decreases. The bandgap variation is attributed to the change in cohesive energy of edge carbon atoms, and is associated with the physicochemical nature and degree of edge saturation. These predictions agree with previously reported computer simulation results, and have potential application in wide‐band optics and optoelectronics.     

Interaction of Aromatic Derivatives with Single‐Walled Carbon Nanotubes

Fluorescence of semiconducting single‐walled carbon nanotubes (SWNTs) normally exhibits diameter‐dependent oxidative quenching behaviour. This behaviour can be changed substantially to become an almost diameter‐independent quenching phenomenon in the presence of electron‐withdrawing nitroaromatic compounds, including o‐nitrotoluene, 2,4‐dinitrotoluene, and nitrobenzene. This change is observed for SWNTs suspended either in sodium dodecyl sulfate or in Nafion upon titration with hydrogen peroxide. Benzene, toluene, phenol, and nitromethane do not show such change. These findings suggest the possibility of forming an electron donor–acceptor complex between SWNTs and nitroaromatic compounds, resulting in leveling the redox potential of different SWNT species. The observation appears to provide a new method for modifying the electrochemical potentials of SWNTs through donor–acceptor complex formation.     

Biocompatible and fluorescent polycaprolactone/silk electrospun nanofiber yarns loaded with carbon quantum dots for biotextiles

Carbon quantum dots (CDs) are attractive nanoparticles for several applications, due to inherent properties such as excitation dependent photoluminescence emission and chemical stability. In the present work, we synthesized CDs from silk (Bombyx Mori) by a microwave‐assisted method. The resultant spherical nanoparticles with high fluorescence under UV light were incorporated into PCL/silk matrix and electrospun into continuous nanofiber yarns (NF‐Ys) by a one‐step method. Besides granting yarns fluorescence, CD inclusion contributed to a decrease in fiber diameter and an increase in strength by 2.7‐fold. Cell viability studies with mammalian lung cell lines show viability above 80%, suggesting good biocompatibilty. Such yarns show the potential to be assembled into larger structures such as biotextiles, with possible multifunctionalities such as antiviral, antibacterial, and biosensing applications.     

Tunable Photoluminescence Across the Entire Visible Spectrum from Carbon Dots Excited by White Light

Although reports have shown shifts in carbon dot emission wavelengths resulting from varying the excitation wavelength, this excitation‐dependent emission does not constitute true tuning, as the shifted peaks have much weaker intensity than their dominant emission, and this is often undesired in real world applications. We report for the first time the synthesis and photoluminescence properties of carbon dots whose peak fluorescence emission wavelengths are tunable across the entire visible spectrum by simple adjustment of the reagents and synthesis conditions, and these carbon dots are excited by white light. Detailed material characterization has revealed that this tunable emission results from changes in the carbon dots’ chemical composition, dictated by dehydrogenation reactions occurring during carbonization. These significantly alter the nucleation and growth process, resulting in dots with either more oxygen‐containing or nitrogen‐containing groups that ultimately determine their photoluminescence properties, which is in stark contrast to previous observations of carbon dot excitation‐dependent fluorescence. This new ability to synthesize broadband excitable carbon dots with tunable peak emissions opens up many new possibilities, particularly in multimodal sensing, in which multiple analytes and processes could be monitored simultaneously by associating a particular carbon dot emission wavelength to a specific chemical process without the need for tuning the excitation source.     

Functionalized Natural Carbon‐Supported Nanoparticles as Excellent Catalysts for Hydrocarbon Production

We report a one‐pot and eco‐friendly synthesis of carbon‐supported cobalt nanoparticles, achieved by carbonization of waste biomass (rice bran) with a cobalt source. The functionalized biomass provides carbon microspheres as excellent catalyst support, forming a unique interface between hydrophobic and hydrophilic groups. The latter, involving hydroxyl and amino groups, can catch much more active cobalt nanoparticles on surface for Fischer–Tropsch synthesis than chemical carbon. The loading amount of cobalt on the final catalyst is much higher than that prepared with a chemical carbon source, such as glucose. The proposed concept of using a functionalized natural carbon source shows great potential compared with conventional carbon sources, and will be meaningful for other fields concerning carbon support, such as heterogeneous catalysis or electrochemical fields.     

Heteroatom‐containing ferrocene derivatives as catalysts for MWCNTs and other shaped carbon nanomaterials

The effects of heteroatom‐containing ferrocene catalysts on the materials produced from chemical vapour deposition (CVD) floating catalyst synthesis were investigated. Specifically, the influence of nitrogen‐ and oxygen‐containing ferrocenoyl imidazolide and (N‐phenylcarbamoyl)ferrocene, and sulfur‐ and oxygen‐containing S,S‐bis(ferrocenylmethyl)dithiocarbonate on the structural morphology and distribution of the products as well as properties such as the thermal stability and crystallinity were studied. In addition, the influence of reaction parameters such as catalyst concentration and temperature were also investigated. The nitrogen‐containing catalysts produced N‐doped multi‐walled carbon nanotubes (N‐MWCNTs), whereas the sulfur‐containing catalyst produced primarily nano‐ and microspheres. A concentration of 2.5 wt% ferrocenoyl imidazolide was shown to be optimal for the synthesis of MWCNTs at 850 °C, with very low metal iron residue, highest thermal stability and highest yield (95%). In general, bamboo compartment length for N‐doped MWCNTs increased with temperature. Crystallinity trends were shown to be independent of catalyst and catalyst concentration in all cases and only dependent on temperature. The average diameter for MWCNTs was shown to be dependent on temperature, choice of catalyst and catalyst concentration in all cases. Copyright © 2012 John Wiley & Sons, Ltd.     

The Chemical Potential of Plasmonic Excitations

By the photoexcitation of localized surface plasmon resonances of metal nanoparticles, one can generate reaction equivalents for driving redox reactions. We show that, in such cases, there is a chemical potential contributed by the plasmonic excitation. This chemical potential is a function of the concentration of light, as we determine from the light‐intensity‐dependent activity in the plasmon‐excitation‐driven reduction of CO₂ on Au nanoparticles. Our finding allows the treatment of plasmonic excitation as a reagent in chemical reactions; the chemical potential of this reagent is tunable by the light intensity.     

Bioreduction of Precious Metals by Microorganism: Efficient Gold@N‐Doped Carbon Electrocatalysts for the Hydrogen Evolution Reaction

The uptake of precious metals from electronic waste is of environmental significance and potential commercial value. A facile bioreductive synthesis is described for Au nanoparticles (ca. 20 nm) supported on N‐doped carbon (Au@NC), which was derived from Au/Pycnoporus sanguineus cells. The interface and charge transport between Au and N‐doped carbon were confirmed by HRTEM and XPS. Au@NC was employed as an electrocatalyst for the hydrogen evolution reaction (HER), exhibiting a small onset potential of ?54.1 mV (vs. RHE), a Tafel slope of 76.8 mV dec^?1, as well as robust stability in acidic medium. Au@NC is a multifunctional electrocatalyst, which demonstrates high catalytic activity in the oxygen reduction reaction (ORR), as evidenced by an onset potential of +0.97 V, excellent tolerance toward methanol, and long‐term stability. This work exemplifies dual recovery of precious Au and fabrication of multifunctional electrocatalysts in an environmentally benign and application‐oriented manner.     

超声法一步合成生物相容的黄绿色荧光碳点

本文以蜡烛灰为碳源,在强酸环境中超声法一步合成了粒径均匀的荧光碳点（CDs）,粒径（3.47±1.81）nm,在紫外灯照射下发出黄绿色荧光.研究表明,CDs表面带有-OH、C=O和-COOH等官能团,存在sp3杂化和sp2杂化两种碳原子.所合成的碳点具有良好的耐光漂白能力和生物相容性,能潜在地作为黄绿色荧光成像试剂应用于细胞成像.     

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.     

Selenium‐Doped Carbon Quantum Dots for Free‐Radical Scavenging

Heteroatom doping is an effective way to adjust the fluorescent properties of carbon quantum dots. However, selenium‐doped carbon dots have rarely been reported, even though selenium has unique chemical properties such as redox‐responsive properties owing to its special electronegativity. Herein, a facile and high‐output strategy to fabricate selenium‐doped carbon quantum dots (Se‐CQDs) with green fluorescence (quantum yield 7.6 %) is developed through the hydrothermal treatment of selenocystine under mild conditions. Selenium heteroatoms endow the Se‐CQDs with redox‐dependent reversible fluorescence. Furthermore, free radicals such as ^.OH can be effectively scavenged by the Se‐CQDs. Once Se‐CQDs are internalized into cells, harmful high levels of reactive oxygen species (ROS) in the cells are decreased. This property makes the Se‐CQDs capable of protecting biosystems from oxidative stress.     

Iron Metal–Organic Frameworks MIL‐88B and NH2‐MIL‐88B for the Loading and Delivery of the Gasotransmitter Carbon Monoxide

Crystals of MIL‐88B‐Fe and NH₂‐MIL‐88B‐Fe were prepared by a new rapid microwave‐assisted solvothermal method. High‐purity, spindle‐shaped crystals of MIL‐88B‐Fe with a length of about 2 μm and a diameter of 1 μm and needle‐shaped crystals of NH₂‐MIL‐88B‐Fe with a length of about 1.5 μm and a diameter of 300 nm were produced with uniform size and excellent crystallinity. The possibility to reduce the as‐prepared frameworks and the chemical capture of carbon monoxide in these materials was studied by in situ ultrahigh vacuum Fourier‐transform infrared (UHV‐FTIR) spectroscopy and Mössbauer spectroscopy. CO binding occurs to unsaturated coordination sites (CUS). The release of CO from the as‐prepared materials was studied by a myoglobin assay in physiological buffer. The release of CO from crystals of MIL‐88B‐Fe with t_1/2=38 min and from crystals of NH₂‐MIL‐88B‐Fe with t_1/2=76 min were found to be controlled by the degradation of the MIL materials under physiological conditions. These MIL‐88B‐Fe and NH₂‐MIL‐88B‐Fe materials show good biocompatibility and have the potential to be used in pharmacological and therapeutic applications as carriers and delivery vehicles for the gasotransmitter carbon monoxide.     

Reactivity of silicon‐doped carbon nanotubes toward small gaseous molecules in the atmosphere

The reactivities of the pristine and silicon doped (Si‐doped) single‐walled carbon nanotubes (CNTs) toward small gaseous molecules in the atmosphere, such as formaldehyde, carbon monoxide, and hydrogen sulfide, were studied by performing density functional theory calculations. Compared with the physisorptions on the pristine (8, 0) CNT, these small molecules present strong chemical interactions with the Si‐doped (8, 0) tube. Doping intrinsic CNTs with silicon is expected to be a potential strategy for improving the property of pristine CNTs and expanding the application of CNTs in nanoscience and nanotechnology. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Nitrogen‐Doped Carbon Nanosheets with Size‐Defined Mesopores as Highly Efficient Metal‐Free Catalyst for the Oxygen Reduction Reaction

Nitrogen‐doped carbon nanosheets (NDCN) with size‐defined mesopores are reported as highly efficient metal‐free catalyst for the oxygen reduction reaction (ORR). A uniform and tunable mesoporous structure of NDCN is prepared using a templating approach. Such controlled mesoporous structure in the NDCN exerts an essential influence on the electrocatalytic performance in both alkaline and acidic media for the ORR. The NDCN catalyst with a pore diameter of 22 nm exhibits a more positive ORR onset potential than that of Pt/C (?0.01 V vs. ?0.02 V) and a high diffusion‐limited current approaching that of Pt/C (5.45 vs. 5.78 mA cm^?2) in alkaline medium. Moreover, the catalyst shows pronounced electrocatalytic activity and long‐term stability towards the ORR under acidic conditions. The unique planar mesoporous shells of the NDCN provide exposed highly electroactive and stable catalytic sites, which boost the electrocatalytic activity of metal‐free NDCN catalyst.     

Boosting ORR Catalytic Activity by Integrating Pyridine‐N Dopants,a High Degree of Graphitization,and Hierarchical Pores into a MOF‐Derived N‐Doped Carbon in a Tandem Synthesis

N‐doped carbon materials represent promising metal‐free electrocatalysts for the oxygen reduction reaction (ORR), the cathode reaction in fuel cells, metal–air batteries, and so on. A challenge for optimizing the ORR catalytic activities of these electrocatalysts is to tune their local structures and chemical compositions in a rational and controlled way that can achieve the synergistic function of each factor. Herein, we report a tandem synthetic strategy that integrates multiple contributing factors into an N‐doped carbon. With an N‐containing MOF (ZIF‐8) as the precursor, carbonization at higher temperatures leads to a higher degree of graphitization. Subsequent NH₃ etching of this highly graphitic carbon enabled the introduction of a higher content of pyridine‐N sites and higher porosity. By optimizing these three factors, the resultant carbon materials displayed ORR activity that was far superior to that of carbon derived from a one‐step pyrolysis. The onset potential of 0.955 V versus a reversible hydrogen electrode (RHE) and the half‐wave potential of 0.835 V versus RHE are among the top ranks of metal‐free ORR catalysts and are comparable to commercial Pt/C (20 wt %) catalysts. Kinetic studies revealed lower H₂O₂ yields, higher electron‐transfer numbers, and lower Tafel slopes for these carbon materials compared with that derived from a one‐step carbonization. These findings verify the effectiveness of this tandem synthetic strategy to enhance the ORR activity of N‐doped carbon materials.     

Ag/ZnO Catalysts with Different ZnO Nanostructures for Non‐enzymatic Detection of Urea

Silver coated ZnO nanorods and nanoflakes with different crystallographic orientations were synthesized by a combination of sputter deposition and solution growth process. Catalytic properties of morphology‐dependent Ag/ZnO nanostructures were then investigated for urea sensors without enzyme. Ag/ZnO nanorods on carbon electrodes exhibit a higher catalytic activity and an improved efficiency than Ag/ZnO nanoflakes on carbon electrodes. Ag/ZnO nanorod catalysts with more electrochemically surface area (169 cm² mg^?1) on carbon electrode facilitate urea electrooxidation due to easier electron transfer, which further promotes the urea electrolysis. The Ag/ZnO nanorod catalysts also show a significant reduction in the onset voltage (0.410 V vs. Ag/AgCl) and an increase in the current density (12.0 mA cm^?2 mg^?1) at 0.55 V vs Ag/AgCl. The results on urea electrooxidation show that Ag/ZnO nanostructures can be a potential catalyst for non‐enzymatic biosensors and fuel cells.     

Electrochemical Synthesis of Carbon Nanodots Directly from Alcohols

Carbon nanodots (C‐dots) show great potential as an important material for biochemical sensing, energy conversion, photocatalysis, and optoelectronics because of their water solubility, chemical inertness, low toxicity, and photo‐ and electronic properties. Numerous methods have been proposed for the preparation of C‐dots. However, complex procedures and strong acid treatments are often required, and the as‐prepared C‐dots tend to be of low quality, and in particular, have a low efficiency for photoluminescence. Herein, a facile and general strategy involving the electrochemical carbonization of low‐molecular‐weight alcohols is proposed. As precursors, the alcohols transited into carbon‐containing particles after electrochemical carbonization under basic conditions. The resultant C‐dots exhibit excellent excitation‐ and size‐dependent fluorescence without the need for complicated purification and passivation procedures. The sizes of the as‐prepared C‐dots can be adjusted by varying the applied potential. High‐quality C‐dots are prepared successfully from different small molecular alcohols, suggesting that this research provides a new, highly universal method for the preparation of fluorescent C‐dots. In addition, luminescence microscopy of the C‐dots is demonstrated in human cancer cells. The results indicate that the as‐prepared C‐dots have low toxicity and can be used in imaging applications.     

Electrochemiluminescence of CdSe Quantum Dots Composited with Nitrogen‐Doped Carbon Nanotubes

A nanocomposite of CdSe quantum dots with nitrogen‐doped carbon nanotubes was prepared for enhancing the electrochemiluminescent (ECL) emission of quantum dots. With hydrogen peroxide as co‐reactant, the nanocomposite modified electrode showed a cathodic ECL emission with a starting potential of ?0.97 V (vs. Ag/AgCl) in phosphate buffer solution, which was five‐times stronger than that from pure CdSe quantum dots and three‐times stronger than that from CdSe quantum dots composited with carbon nanotubes. The latter showed a starting potential of ?1.19 V. This result led to a sensitive ECL sensing of hydrogen peroxide with good stability, acceptable reproducibility and a detection limit down to 2.1×10^?7 mol L^?1. Nitrogen‐doped carbon nanotubes could be used as a good material for the construction of sensitive ECL biosensors for chemical and biochemical analysis.     

Thermomechanical and structural characterization of polybutadiene/poly(ethylene oxide)/CNT stretchable electrospun fibrous membranes

It is difficult to produce rubbery polymer nanofibers, that is, polybutadiene, by the method of electrospinning, since during electrospinning rubbery polymer fibers join and entangles due to their low T_g. For this reason, it is not easy to achieve the fiber form out of these polymers. Homogeneously electrospun carbon nanotubes (CNT)‐filled polybutadiene (PBu) and poly(ethylene oxide) (PEO) composite elastomeric fibers exhibit distinctive physical features such as uniform fiber diameter and distribution with significant improvements in thermomechanical properties. Controlled hydrophilicity/hydrophobicity with the components allows to generate homogenous, thermally stable and stretchable bio‐composite scaffold, and fibrous antibacterial membrane scaffolds out of PBu/PEO/CNT composite. We have combined the exciting properties of PEO with high pore density with the rubber elasticity of PBu via dissolving them in a dichloromethane/ethyl acetate organic solvent, and subsequently producing electrospun woven fibers with different PBu/PEO ratios. Frequency‐dependent thermomechanical characterization via dynamic mechanical analysis reveals pronounced changes in the onset and extent of melting, as well as the storage and loss modulus values at the onset of melting, in particular when small amounts (1.25% by wt%) of CNTs are present. The characteristic bands were detected for the PBu/PEO and PBu/PEO/CNT samples by means of Raman and Fourier‐transform infrared spectroscopy. CNT addition increases the hydrophobicity via the increase in roughness as attained by atomic force microscopy.