Synthesis of (B-C-N) Nanomaterials by Arc Discharge Using Heterogeneous Anodes

In spite of the current prevalence of the CVD-based processes, the electric arc remains an interesting process for the synthesis of carbon nanoforms, thanks to its versatility, robustness and easiness. It also allows performing in-situ substitution of carbon atoms by hetero-elements in the graphene lattice. Our work aims to establish a correlation between the plasma properties, type and chemical composition （and the substitution rate） of the obtained single-wall carbon nan- otubes. The plasma was characterized by optical emission spectroscopy and the products were analyzed by high resolution transmission electron microscopy and core level Electron Energy-Loss Spectroscopy （EELS）. Results show that a high boron content leads to a plasma temperature decrease and hinders the formation of nanotubes. This effect can be compensated by increasing the arc current and/or yttrium content. The optimal conditions for the synthesis of boron- and/or nitrogen-substituted nanotubes correspond to a high axial plasma temperature associated to a strong radial gradient. EELS analysis confirmed that the boron incorporates into the graphenic lattice.

A review of microwave-metal discharge interaction:Mechanism,regulation,and application for synthesis of nanomaterials

Placing metals within microwave ovens has been generally viewed as a dangerous practice because of occurrence of violent discharge,but in recent years such discharge phenomenon has attracted increasing attention and has enabled a variety of exciting applications.In this work,we provide a comprehensive review of fundamental understanding of microwave-metal discharge interaction and its state-of-the-art application for nanomaterials synthesis.We introduce the microscopic interaction between different categories of materials and the electric and magnetic field of microwaves.For microwave-metal interaction,we highlight its size-dependence and point out the influence of the oxide layer on the surface of metals.We discuss the required conditions for occurrence of discharge,microscopic formation mechanism,and characteristic features of microwave-metal discharge processes.Through analyzing the influence from the microwave input,discharging metals,and surrounding discharging media,we discuss the strategy for systematical regulation of the discharge process.We describe the applications of the microwave-metal discharge for facile synthesis of various functional nanomaterials including core-shell carbon/metal,metal oxides,metal chalcogenides,intermetallic compounds,metallic nanoparticles and metallic compounds,and organic compounds.Finally,the challenges in precise characterization and dynamic regulation of the discharge process as well as exciting application opportunities are discussed.

Non-thermal radiation heating synthesis of nanomaterials

The nanoscale effect enables the unique magnetic,optical,thermal and electrical properties of nanostructured materials and has attracted extensive investigation for applications in catalysis,biomedicine,sensors,and energy storage and conversion.The widely used synthesis methods,such as traditional hydrothermal reaction and calcination,are bulk heating processes based on thermal radiation.Differing from traditional heating methods,non-thermal radiation heating technique is a local heating mode.In this regard,this review summarizes various non-thermal radiation heating methods for synthesis of nanomaterials,including microwave heating,induction heating,Joule heating,laser heating and electron beam heating.The advantages and disadvantages of these non-thermal radiation heating methods for the synthesis of nanomaterials are compared and discussed.Finally,the future development and challenges of non-thermal radiation heating method for potential synthesis of nanomaterials are discussed.

Diverse nanomaterials synthesized by laser ablation of pure metals in liquids

Diverse nanomaterials, in the forms of carbides, sulfides, oxides, metals, hydroxides, etc., have been synthesized by laser ablation in liquids(LAL) with metal targets as the dominant educts. Many advantages of LAL technique itself and its products have been revealed since 1983 when the first report about LAL was released. Different from traditional wet-chemical synthesis,one unique feature of LAL is its resultant extreme high-temperature and high-pressure local environment for the nucleation and growth of nanomaterials, despite being performed at room temperature. This extreme condition can induce the atomization and ionization of the target materials and liquid molecules to incur different chemical reactions. The laser, liquid, liquid additive, and target can significantly alter the local environment in a broad range. Thus, different phases and shapes of nanomaterials are producible even from the same target. Through directly comparing the products of LAL of 13 kinds of chosen representative metals synthesized under different conditions, this review presents and discusses current understandings, challenging issues, and perspectives related to the diversity of LAL-products, which is willing to promote a deeper investigation and discussion on a clear clarification of the chemical reactions and particle nucleation/growth processes.

Nanomaterials synthesized by gas combustion flames:Morphology and structure

The flame technology has been employed broadly for large-scale manufacture of carbon blacks, fumed silica, pigmentary titania, and also ceramic commodities such as SiO2, Ti02, and A1203. A deeper understanding of the process also made it possible for production of novel nanomaterials with high functionality--various novel nanomaterials such as nanorods, nanowires, nanotubes, nanocoils, and nanocomposites with core/shell, hollow and ball-in-shell structures, have been synthesized recently via gas combustion technology, while the mechanisms of the material formation were investigated based on the nucleation-growth and chemical engineering principles. Studies of the fluid flow and mass mixing, supported by principles of chemical reaction engineering, could provide knowledge for better understanding of the process, and thus make rational manipulation of the products possible.

Morphology-Controlled Synthesis of CeO_2 Microstructures and Their Room Temperature Ferromagnetism

Gear-shape CeO2 microstructures have been synthesized via a facile hydrothermal method with Ce（NO3）3-6H20 as the cerium source, NHaHCO3 as both the precipitator and the carbon source, and cetyltrimethyl ammonium bromide （CTAB） as the surfactant. X-ray diffraction （XRD） inferred that the synthesized CeO2 microstructures exhibited a fluorite structure. The band gap （Eg） of CeO2 samples is larger than that of bulk. X-ray photoelectron spectroscopy （XPS） showed that there are plenty or Ce3＋ ions and oxygen vacancies at the surface of CeO2 samples. All the synthesized CeO2 samples exhibited the room temperature ferromagnetism, and the saturation magnetization increases with the increases of lattice parameter and Eg. The room temperature ferromagnetism mechanism of gear-shape CeO2 is mainly attributed to the influence Ce3＋ ions.

Gold nanoparticles functionalized with supramolecular macrocycles

Gold nanoparticles （AuNPs） functionalized with supramolecular macrocycles are versatile and diverse hybrid nanomaterials, which combine and enhance the characteristics of the two components. In this mini-review, we summarize the recent research progress on the synthesis and assembly of AuNPs functionalized with different supramolecular macrocyclic compounds, i.e., crown ethers, cyclophanes, cyclodextrins （CDs）, cucurbit[n]urils （CB[n]）, calix[n]arenes, and pillar[n]arenes （PIn]A）. Meanwhile, applications of these supramolecular hybrid nanomaterials in the fields of sensors, biomedicine and plasmonic devices are also presented.

Sub-100 nm hollow SnO_2@C nanoparticles as anode material for lithium ion batteries and significantly enhanced cycle performances

Rational designing and controlling of nanostructures is a key factor in realizing appropriate properties required for the high-performance energy fields. In the present study, hollow Sn O2@C nanoparticles（NPs） with a mean size of 50 nm have been synthesized in large-scale via a facile hydrothermal approach.The morphology and composition of as-obtained products were studied by various characterized techniques. As an anode material for lithium ion batteries（LIBs）, the as-prepared hollow Sn O2@C NPs exhibit significant improvement in cycle performances. The discharge capacity of lithium battery is as high as 370 m Ah g 1, and the current density is 3910 m A g 1（5 C） after 573 cycles. Furthermore, the capacity recovers up to 1100 m Ah g 1at the rate performances in which the current density is recovered to 156.4 m A g 1（0.2 C）. Undoubtedly, sub-100 nm Sn O2@C NPs provide significant improvement to the electrochemical performance of LIBs as superior-anode nanomaterials, and this carbon coating strategy can pave the way for developing high-performance LIBs.

Self-organization of various“phase-separated”nanostructures in a single chemical vapor deposition

Chemical vapor deposition(CVD)is one of the most versatile techniques for the controlled synthesis of functional nanomaterials.When multiple precursors are induced,the CVD process often gives rise to the growth of doped or alloy compounds.In this work,we demonstrate the self-assembly of a variety of‘phase-separated’functional nanostructures from a single CVD in the presence of various precursors.In specific,with silicon substrate and powder of Mn and SnTe as precursors,we achieved self-organized nanostructures including Si/SiOx core-shell nanowire heterostructures both with and without embedded manganese silicide particles,Mn11Si19 nanowires,and SnTe nanoplates.The Si/SiOx core-shell nanowires embedded with manganese silicide particles were grown along the<111>direction of the crystalline Si via an Au-catalyzed vapor-liquid-solid process,in which the Si and Mn vapors were supplied from the heated silicon substrates and Mn powder,respectively.In contrast,direct vapor-solid deposition led to particle-free<110>-oriented Si/SiOx core-shell nanowires and<100>-oriented Mn11Si19 nanowires,a promising thermoelectric material.No Sn or Te impurities were detected in these nanostructures down to the experimental limit.Topological crystalline insulator SnTe nanoplates with dominant{100}and{111}facets were found to be free of Mn(and Si)impurities,although nanoparticles and nanowires containing Mn were found in the vicinity of the nanoplates.While multiple-channel transport was observed in the SnTe nanoplates,it may not be related to the topological surface states due to surface oxidation.Finally,we carried out thermodynamic analysis and density functional theory calculations to understand the‘phase-separation’phenomenon and further discuss general approaches to grow phase-pure samples when the precursors contain residual impurities.