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The development of energy storage devices providing high energy and power densities and long-term stability will play an important role in the future utilization of sustainable energy sources. Numerous efforts have been devoted to achieving these requirements, especially the design of advanced electrode materials. For this reason, there is growing interest in the innovation of new carbon-based materials with enhanced electrochemical performance. Nanostructured carbon spheres (CSs) have attracted significant attention due to their prominent properties, such as high surface area, excellent electrical conductivity, tunable porosity, and surface functionality. This review offers a comprehensive overview into the recent advances of nanostructured CSs within the last five years, focusing on synthetic strategies for producing carbon particles with precisely controlled morphologies and interior structures, as well as the potential applications of these particles as high-performance electrode materials in rechargeable batteries and supercapacitors. The challenges and perspectives on future research directions are highlighted, focusing on the controlled synthesis and functionalization of nanostructured CSs with tunable structures and properties that are well-suited to practical applications. This review is intended to serve as a helpful resource to researchers involved in the fabrication of new CS materials and the development of methods to control their structure and morphology.

The purpose of the present study was to reveal the details of the preparation of CaF2 particles with controllable size (30–900 nm) and shape (spherical, hexagonal, and cubical forms) using a liquid-phase synthesis method, and to demonstrate that a change in the composition of the reactants and crystalline structure of the CaF2 product could improve material performance. The particles were synthesized from the reaction of CaCl2 and NH4F in an aqueous solution in the absence of any additional components (e.g., chemicals, surfactants). Monodispersed particles were achieved by the optimization of the reaction condition parameters: temperature, mixing rate, and reaction time. Control of the particle size was accomplished mainly by changing the concentration of the reactants, which is qualitatively explained by the conventional nucleation theory. Flexibility of the process in controlling particle morphology, from a spherical to a hexagonal and/or a cubical form, was predominantly achieved by varying the concentration of CaCl2. Since the identical XRD pattern was detected in particles with varying morphologies, the shape transformation was due to changes in particle growth. A theoretical background to support how the particles changed was also added and was compared with an analysis of the number of nuclei. In addition, sufficient adjustment of the reactant compositions made it possible to produce a material with an ultralow refractive index (nCaF2 was near to ntheoretical CaF2), which was confirmed by the measurement of the refractive index and the material crystallinity.

Pt metal particles supported on carriers such as MgO and SiO2 showed high activity for the formation of carbon nanotubes (CNTs) through ethylene decomposition at 973 K. However, these CNTs were not uniform in diameter because of the sintering of Pt metal particles during the reaction. Covering Pt catalysts with silica prevented the sintering of Pt metal particles during ethylene decomposition, resulting in the formation of CNTs with a uniform diameter. [ABSTRACT FROM AUTHOR]

Cross-sectional TEM images of carbon nanofibers formed through methane decomposition over Ni/SiO2 catalysts were observed by using an ultramicrotome. The TEM images indicated that carbon nanofibers have regular hexagonal prism structures. [ABSTRACT FROM AUTHOR]

Platinum-loaded carbon is commonly used in polymer electrolyte fuel cells (PEFCs); however, it is known to corrode or degrade under high potentials, which results in poor cell performance. Niobium-doped tin oxide (Nb-SnO2; NTO) nanoparticles are alternative materials to carbon because of their high durability and good cell performance as catalyst support in fuel cells. Here, we introduce the preparation of NTO nanoparticles with high specific surface area by spray flames. The particle characteristics and PEFC performances of the nanoparticles were evaluated. Spray combustion with a two-fluid nozzle was used where the raw material species were rapidly gasified to form fine nanoparticles. The spray flame synthesis was operated at a combustion enthalpy density of 4.87 kJ/ggas. This enabled homogeneous nanoparticle formation and suppressed particle growth under a minimal condition. The flame-made NTO nanoparticles showed a primary particle size and specific surface area of ~ 8.77 nm and 87.04 m2/g, respectively. Rietveld analysis revealed a detailed crystal structure of the NTO nanoparticles. In addition, Pt was loaded on the NTO nanoparticles and the cell performance of the resulting material was assessed using a membrane electrode assembly. The results of this study can be used to improve the features of flame-made NTO nanoparticles in order to suit the needs of a fuel cell application. [ABSTRACT FROM AUTHOR]

Oxygen-carbon-contained CrMnFeCoNi coatings were electrodeposited in an organic solvent of DMF-CH3CN (N,N-dimethylformamide-acetonitrile) containing chlorides of chromium, manganese, iron, cobalt, and nickel, with or without supporting electrolyte lithium perchlorate (LiClO4). The coatings' composition, structure, hardness, and electrocatalytic properties were examined. The presence of lithium in coatings obtained with LiClO4 showed it unsuitable as a supporting electrolyte in this fabrication process. Without LiClO4, oxygen-carbon-contained CrMnFeCoNi coatings were obtained at constant potentials at −2.0, −2.5, and −3.0 V (vs. SSE) by enhancing the concentrations of the target metal ions in the solution. These coatings were mainly amorphous with nanocrystals, which were comprised of >50 atom% oxygen atoms, >7 atom% carbon atoms, and near equiatomic Cr, Mn, Fe, Co, and Ni, showing a high level of hardness and advanced electrocatalytic activity in the oxygen evolution reaction. [ABSTRACT FROM AUTHOR]

A commercial high‐resolution X‐ray computed tomography (CT) was utilized for non‐destructive analysis of single fibers. The micro‐CT apparatus was employed because it is applicable to both colored and colorless fibers. A sample preparation using adhesive sheets was demonstrated, and the method is similar to typical tape‐lift sample collection method in crime cases. Different cross‐sectional shapes of nylon and polyester single fibers were non‐destructively distinguished, and the method is applicable to all types of fibers. Cross‐sectional areas, aperture ratios, and volumes of individual fibers were directly and automatically measured using the open‐source software. The observed parameters were within a coefficient of variation of 3%. In addition, a mass of a single fragment of a fiber can be estimated when the local density is given. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) were characterized and their synthesis optimized extensively over recent years. It is becoming more and more important to develop synthesis solutions for CQDs applications to allow simple and cheap applications with composite materials. Here, we present a one-pot CQDs reaction in an aqueous polyvinyl alcohol (PVA) solution and the synthesis of transparent UV protection films. The synthesis solution was tuned in a way that transparent UV-protection films cast from unpurified CQDs–PVA solutions could be obtained without the need of yield consuming purification steps. Measuring the impact of varying PVA, branched polyethylene imine (b-PEI), and citric acid (CA) concentrations on the solution's and film's UV/Vis transmission and absorbance allowed elucidating important factors influencing the solution to film property transition. Applying CQDs–PVA films on commercially available PET bottle films resulted in high transparency of the composite film in the visible range (＞80%) and UV absorption of over 90%. Lastly, our CQDs–PVA film performed stable UV-blocking and did not show any bleaching effects over several days of UV-exposure. [ABSTRACT FROM AUTHOR]

The table of contents for June 2016 issue of "New Journal of Chemistry" is presented.

An optimum nanostructure and pore size of catalyst supports is very important in achieving high catalytic performances. In this instance, we evaluated the effects of various carbon nanostructures on the catalytic performances of carbon-supported platinum (Pt/C) electrocatalysts experimentally and numerically. The Pt/C catalysts were prepared using a hybrid method involving the preparation of dense, hollow, and porous nanostructured carbon particle via aerosol spray pyrolysis followed by microwave-assisted Pt deposition. Electrochemical characterization of the catalysts showed that the porous Pt/C catalyst gave the best performance; its electrochemical surface area was much higher, more than twice than those of hollow or dense Pt/C. The effects of pore size on electrocatalysis were also studied. The results showed the importance of a balance between mesopores and macropores for effective catalysis with a high charge transfer rate. A fluid flow model showed that good oxygen transport contributed to the catalytic activity. © 2015 American Institute of Chemical Engineers AIChE J, 62: 440-450, 2016 [ABSTRACT FROM AUTHOR]

White light-emitting diodes offer the possibility of efficient, safe, and reliable solid-state lighting, and thus have various applications. Reported white light-emitting phosphors usually contain expensive rare-earth metals and are generally prepared by high-energy processes (e.g., >1000 °C, H2 and CO reduction atmospheres). These factors limit their applications. Therefore, preparing cost-effective white light-emitting phosphors from environmentally friendly processes is an important challenge. Herein, a direct white light-emitting aluminium–boron–carbon–oxynitride (AlBCNO) phosphor, which can be economically produced using low-energy methods (<900 °C, atmospheric conditions), is reported. To the best of our knowledge, this is the first reported rare-earth-free white light-emitting phosphor. AlBCNO emission spans the entire visible spectrum and its broad excitation spectrum is comparable to that of near-UV light-emitting diodes. Increasing the relative concentrations of B or Al in AlBCNO enables emission tuning to yellow or blue, respectively. These findings have implications for new methods of preparing white light-emitting phosphors. [ABSTRACT FROM AUTHOR]

Doughnut magnesium fluoride particles with controllable size (from 6 to 50 nm) and shape (sphere and cube) were successfully prepared using an electron-beam irradiation method. While common reports typically produced doughnut particles in the micrometer range, the present method succeeded in preparing this type of particles with sizes of nanometers. Different from other methods that pointed out the importance of the additional additive and specific process to support the formation of doughnut structure, we preferred exploiting the electron-beam irradiation method that was simpler and free of additive. Transformation of the particle from its original morphology (dense structure) into doughnut shape were also investigated, along with the analysis of irradiation time and elemental composition. Outer sizes and shapes of the final particles were identical to those of the initial particles (before irradiation process), giving a potential way for controlling the size and the shape of the doughnut particles by adjusting the size and the shape of the initial magnesium fluoride particles only. [ABSTRACT FROM AUTHOR]

In the present study, we found that pressure-dependent droplet-to-particle formation is important for the control of both droplet and particle characteristics during the production of particles with enhanced properties. Using experimental and simulation approaches, the present study investigated the droplet-to-particle formation of zinc oxide as a model material that was synthesized via low-pressure spray pyrolysis. The size distributions of both the droplets generated under low-pressure and the synthesized particles were measured and compared. The effects of operating conditions, i.e., operating pressure, carrier gas-, and liquid-flow rates, reactor temperature, and precursor concentration, on the characteristics of the generated droplets and synthesized zinc oxide particles were systematically investigated. We found that broad and bimodal droplet size distributions shifted to narrow and monodispersed distributions as chamber pressures were reduced. The low-pressure-synthesized zinc oxide nanoparticles were highly crystallized with unimodal distributions and sizes of approximately 8 nm. Droplet temperature decreased with decreasing chamber pressure, which confirmed both the evaporative cooling of droplets and the formation of smaller droplet sizes. The chamber temperature and droplet size simulation results were in accordance with the experimental results. In conclusion, we found that the chamber pressure is the primary determinant of monodispersity with respect to droplet size distribution and to the size and morphology of the synthesized particles. [ABSTRACT FROM AUTHOR]

A solid phase crystallization ( spc) method was applied for the preparation of SrTiO3-supported Ni catalysts and compared to the impregnation ( imp) method. spc-Ni0.2/SrTiO3 has highly dispersed and stable Ni metal particles resulting in higher activity and higher sustainability against coking than imp-Ni0.2/SrTiO3 in the partial oxidation of CH4. Both catalysts were tested for the CH4 pyrolysis in order to elucidate the catalytic nature against coking of spc-Ni0.2/SrTiO3. The amount of carbon and the rate of H2 formation were similar over both catalysts at both 773 and 1073 K. On both catalysts, CH4 continuously decomposed at 773 K, while the rate of CH4 pyrolysis quickly decreased at 1073 K. Fibrous carbons grew up with a Ni metal particle on the tip of the fiber at 773 K, while carbon balls and short carbon fibers with a Ni metal particle encapsulated inside formed and no sufficient growth of the fiber was observed at 1073 K. The carbon species formed at 773 K was hydrogenated completely to CH4 around 873 K, while the hydrogenation of that formed at 1073 K needed higher temperature around 1073 K. However, the carbon species formed on both the catalysts at either 773 or 1073 K was completely oxidized around 773 K. Thus, judging from the anti-coking nature, the behaviors in the CH4 pyrolysis are similar over both catalysts, nonetheless spc-Ni0.2/SrTiO3 was far superior to imp-Ni0.2/SrTiO3 in the CH4 oxidation. It is likely that the high sustainability against coking of spc-Ni0.2/SrTiO3 is not due to its intrinsic nature suppressing the coking but due to its high activity of reforming which can quickly eliminate the carbon formed on the catalyst surface. [ABSTRACT FROM AUTHOR]