Hollow carbonaceous capsules from glucose solution

Repairable body-centered cubic Fe0 anchoring on porous hollow nitrogen-doped carbon spheres with adjusting electron distribution for efficient electrocatalytic ammonia synthesis

Electrocatalytic nitrogen reduction reaction (ENRR) is a promising and efficient method for ammonia production. However, ENRR is restricted by the adsorption and activation of N2. Herein, an efficient nitrogen reduction reaction (NRR) electrocatalyst loaded with zero valent iron (ZVI) particles onto porous nitrogen-doped carbon (NC) hollow spheres is reported. The optimal Fe@10N3C-950 exhibits excellent performance with high ammonia (NH3) yield (152.28 µg h-1 mgcat-1) and Faradaic efficiency (FE, 54.55 %) at - 0.3 V (versus reversible hydrogen electrode, vs. RHE). Bader charge shows that the adsorbed N2 acquires more electrons from Fe sites with body-centered cubic (BCC) structure to better activate N2. Moreover, i-t experiments are performed before electrocatalytic NH3 production to effectively eliminate the effect of oxidation on ZVI and thus, maintain high ENRR activity for Fe@10N3C-950. Theoretical calculations indicate that nitrogen doping not only reduces the Gibbs free energy of rate determining step (RDS), but the BCC-structured Fe can also decrease the energy barriers of N2 activation and RDS.

Process Effluent Recycling in the Supercritical Water Gasification of Dry Biomass

The influence of process water recycling during the Supercritical Water Gasification (SCWG) of dry biomasses was investigated. Dry biomass has to be diluted with water to a dry matter content of approximately 10 wt.% to gasify it in the process of supercritical water gasification. The treatment of wastewater in the SCWG process is cost intensive due to organic contaminants; therefore, the recycling of the process effluent is attractive. Salt separation is needed to avoid accumulation of salts in the effluents, since salts enhance corrosion rates and might cause blocking of the flow when the effluent is recycled. The grass Reed Canary Grass and grapevines were gasified. The recycling of the process effluent did not influence the composition of the product gas. In both cases the carbon efficiency decreased by 4% when wastewater was used to dilute the biomass. An increase in organic carbon and potassium in the reactor effluent was observed after gasification of the biomass with recycled process effluent. The addition of potassium hydroxide to the feed as a homogenous catalyst needs to be closely monitored and adjusted according to the potassium content of the reactor effluent. Insufficient salt separation proved to be an issue regarding formation of solid deposits in the reaction system.

Macroporous chitin microspheres prepared by surfactant micelle swelling strategy for rapid capture of lead (II) from wastewater

Heavy metal pollution of water source continues to be one of the most serious environmental problems which have attracted major global concern. Here, a macroporous chitin microsphere is prepared by surfactant micelle swelling strategy followed by modification with tetraethylenepentamine for Pb²⁺ removal from wastewater. The resultant adsorbent not only exhibits fast adsorption kinetic (>80% of its equilibrium uptake within 20 min) but also has high adsorption capacity of 218.4 ± 6.59 mg/g and excellent reusability (>75% of its initial adsorption capacity after five adsorption/desorption cycles). More importantly, under the continuous operating mode, the adsorbent can treat about 39,000 kg water/kg adsorbent, and the Pb²⁺ concentration decreases from 2000 μg/L to smaller than 10 μg/L, meeting the drinking water standard recommended by the World Health Organization (10 μg/L). All results indicate that the tetraethylenepentamine-modified macroporous chitin microspheres have great potential in the treatment of heavy metal contamination.

Flute-type porous carbon derived from soybean shells for high-performance all-solid-state symmetric supercapacitors

Flute-type porous carbon was successfully prepared from soybean shells through convenient methods. The influence of mass ratio on the structure and electrochemical performance of porous carbon obtained from soybean shells was investigated in detail. The obtained porous carbon exhibited a micro-tube morphology structure with a specific surface area of 2802 m² g⁻¹, pore volume of 1.36 cm³ g⁻¹, and appropriate pore size distribution. The porous carbon showed good electrochemical properties as an electrode material for supercapacitors. The optimal porous carbon SSAC4 exhibited high specific capacitance of 465 F g⁻¹ (1 A g⁻¹) and 287 F g⁻¹ (20 A g⁻¹) in a three-electrode system with 6 M KOH electrolyte. In addition, the as-assembled SSAC4-based all-solid-state supercapacitors delivered a high specific capacitance of 294 F g⁻¹ at 0.1 A g⁻¹ and excellent cycling stability of 86.2% after 10 000 cycles at 5 A g⁻¹.

Flute type porous carbon is successfully derived from soybean shell through a convenient method. The porous carbon shows good electrochemical properties as an electrode material for supercapacitors.

Porous hard carbon spheres derived from biomass for high-performance sodium/potassium-ion batteries

Hard carbon is the most attractive anode material for electrochemical sodium/potassium-ion storage. The preparation of hard carbon spheres directly from the broad sources of biomass is of great interest but barely reported. Herein, we developed a simple two-step hydrothermal method to construct porous carbon microspheres directly from the original waste biomass of camellia shells. The porous carbon microspheres have high specific capacities of 250 mAh g^-1and 264.5 mAh g^-1at a current density of 100 mA g^-1for sodium-ion batteries and potassium-ion batteries, respectively. And it has excellent cycle stability for sodium ions and potassium ions outperforming most reported hard carbons, which is mainly attributed to the microporous structure and spherical morphology. The work paves a way to prepare porous hard carbon spheres directly from biomass for alkali metal-ion batteries.

Facile synthesis of Ag@C@Ag hybrid nanoparticles as SERS substrate

Ag@C core-shell nanoparticles (NPs) were first prepared by a low-temperature heating-stirring method and subsequently modified with polyethyleneimine (PEI) at different concentrations. Finally, Ag@C@Ag hybrid NPs were prepared by a simple self-assembly procedure, and 24-nm Ag NPs were attached onto the surface of the initially fabricated PEI-modified Ag@C NPs via interaction between the NH₂ groups of PEI and Ag. The results demonstrated that rhodamine 6G (R6G) could be detected at a concentration as low as 10^-10 M using the Ag@C@Ag NPs as a substrate. To further understand the signal enhancement mechanism, finite-difference time-domain (FDTD) simulations were performed to calculate the electromagnetic field distributions and illustrate the generated Raman hot spots. The FDTD indicated that this enhancement was attributed to the surface plasmon resonance effects of the core Ag NPs in the Ag@C NPs, hot spots between the Ag@C NPs, and external assembly of the 24-nm Ag NPs, as well as between the massive outlayer 24-nm Ag NPs themselves. These fabricated materials were further applied for the detection of folic acid as an actual sample. The outstanding performance of the Ag@C@Ag NPs can be attributed to both the excellent properties of this hybrid substrate and the absorption capability of the carbon layer. Thus, this Ag@C@Ag NP material demonstrates excellent and stable optical properties, and can be used as a surface-enhanced Raman scattering (SERS) substrate in the field of ultrasensitive spectral analysis. Graphical abstract Ag@C@Ag hybrid nanoparticles are prepared by a simple self-assembly method. Then the synthesized Ag@C@Ag hybrid nanoparticles are used as SERS substrate for folic acid detection. To further understand the signal enhancement mechanism, finite-difference time-domain simulations are performed to calculate the electromagnetic field distributions and illustrate the generated SERS hot spots.

Nanotechnology in cosmetics pros and cons

The field of nanotechnology is being greatly explored by cosmetic industries in order to improve the efficacy of cosmetic products. The increased use of nanomaterials in the field of cosmetics can have two sides as health-related benefits and detrimental effects. This review mainly seeks the pros and cons of the use of nanomaterials in cosmetics along with some examples of nanomaterials that are widely used in cosmetic industries along with different types of nanotechnology-based cosmetic products. The benefits of nanomaterials in cosmetic formulations are huge. Moreover the study regarding the toxic effects on the health also equally matters. This review gives a brief outline of the advantages as well as disadvantages of nanotechnology in cosmetics.

Influence of hollow sphere surface heterogeneity and geometry of N-doped carbon on sensitive monitoring of acetaminophen in human fluids and pharmaceutical products

A sensitive and selective acetaminophen sensor assay was designed based on N-HCCS. The surface morphology, and composition of open hollow conjugated spheres of N-HCCS resulted in facile AC diffusion/loading and electrocatalytic oxidation.

Bamboo derived hydrochar microspheres fabricated by acid-assisted hydrothermal carbonization

In this study, bamboo residues derived functional hydrochar microspheres have been fabricated by different acids-assisted hydrothermal carbonization including hydrochloric aicd, sulfuric acid or nitric acid.The energy-dispersive X-ray fluorescence spectroscopy and Fourier Transform Infrared spectroscopy analyses showed that sulfur- and nitrogen-containing functional groups were grafted on the surface of hydrochar microspheres, respectively. Elemental analysis indicates that the addition of acids has a significant influence on the hydrothermal reaction pathway and promotes the hydrolysis process. When the hydrothermal carbonization temperature is 220 °C, hydrochloric acid and nitric acid can effectively overcome the agglomeration of hydrochar microspheres and form single micron carbon sphere. Irregularly shaped hydrochar particles groups were formed during sulfuric acid-assisted hydrothermal treatment. The results indicate the viability of acid assisted hydrothermal carbonization to produce the functional hydrochar microsphere using bamboo residues.

Hollow micro and nanostructures for therapeutic and imaging applications

Hollow particles have been extensively used in bioanalytical and biomedical applications for almost two decades due to their unique and tunable optoelectronic properties as well as their significantly high loading capacities. These intrinsic properties led them to be used in various bioimaging applications as contrast agents, controlled delivery (i.e. drugs, nucleic acids and other biomolecules) platforms and photon-triggered therapies (e.g. photothermal and photodynamic therapies). Since recent studies showed that imaging-guided targeted therapeutics have higher success rates, multimodal theranostic platforms (combination of one or more therapy and diagnosis modality) have been employed more often and hollow particles (i.e. nanoshells) have been one of the most efficient candidates to be used in multiple-purpose platforms, owing to their intrinsic properties that enable synergistic multimodal performance. In this review, recent advances in the applications of such hollow particles fabricated with various routes (either inorganic or organic based) were summarized to delineate strategies for tuning their properties for more efficient biomedical performance by overcoming common biological barriers. This review will pave the ways for expedited progress in design of next generation of hollow particles for clinical applications.

Nanohollow Carbon for Rechargeable Batteries: Ongoing Progresses and Challenges

Among the various morphologies of carbon-based materials, hollow carbon nanostructures are of particular interest for energy storage. They have been widely investigated as electrode materials in different types of rechargeable batteries, owing to their high surface areas in association with the high surface-to-volume ratios, controllable pores and pore size distribution, high electrical conductivity, and excellent chemical and mechanical stability, which are beneficial for providing active sites, accelerating electrons/ions transfer, interacting with electrolytes, and giving rise to high specific capacity, rate capability, cycling ability, and overall electrochemical performance. In this overview, we look into the ongoing progresses that are being made with the nanohollow carbon materials, including nanospheres, nanopolyhedrons, and nanofibers, in relation to their applications in the main types of rechargeable batteries. The design and synthesis strategies for them and their electrochemical performance in rechargeable batteries, including lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, and lithium-sulfur batteries are comprehensively reviewed and discussed, together with the challenges being faced and perspectives for them.

Nanoengineering Carbon Spheres as Nanoreactors for Sustainable Energy Applications

Colloidal carbon sphere nanoreactors have been explored extensively as a class of versatile materials for various applications in energy storage, electrochemical conversion, and catalysis, due to their unique properties such as excellent electrical conductivity, high specific surface area, controlled porosity and permeability, and surface functionality. Here, the latest updated research on colloidal carbon sphere nanoreactor, in terms of both their synthesis and applications, is summarized. Various synthetic strategies are first discussed, including the hard template method, the soft template method, hydrothermal carbonization, the microemulsion polymerization method, and extension of the Stöber method. Then, the functionalization of colloidal carbon sphere nanoreactors, including the nanoengineering of compositions and the surface features, is discussed. Afterward, recent progress in the major applications of colloidal carbon sphere nanoreactors, in the areas of energy storage, electrochemical conversion, and catalysis, is presented. Finally, the perspectives and challenges for future developments are discussed in terms of controlled synthesis and functionalization of the colloidal carbon sphere nanoreactors with tunable structure, and the composition and properties that are desirable for practical applications.

Pristine Graphene Microspheres by the Spreading and Trapping of Graphene at an Interface

The interfacial spreading and exfoliation of graphene was used to create low-density, hollow microspheres defined by a thin shell of graphene. The spheres were templated by a thermodynamically driven self-assembly process in which graphite spontaneously exfoliated and spread at the high-energy interfaces of a water-in-oil emulsion. Graphene thus acted as a 2D surfactant to stabilize the dispersed water droplets utilized as polymerization templates. Using a mixture of organic solvent and monomer as the emulsion oil phase, polystyrene-coated hollow graphene microspheres were created. These spheres were characterized by optical and electron microscopy, thermo-gravimetric analysis, nanoindentation, and particle sizing. The mechanism leading to the microsphere surface morphology and shape is discussed, with the oil phase composition shown to play a critical role.

Emerging Carbon-Nanofiber Aerogels: Chemosynthesis versus Biosynthesis

Carbon aerogels that are typically prepared using sol-gel chemistry have unique three dimensional networks of interconnected nanometer-sized particles and thus exhibit many fascinating physical properties and great application potentials in widespread fields. To boost the practical applications, it is necessary to develop efficient and low-cost methods to produce high-performance carbon aerogels on a large-scale, preferably in a sustainable way. In 2012, two new classes of aerogels consisting of carbon-nanofiber (CNF) networks were prepared from biomass-derived precursors by chemosynthesis (i.e. template-directed hydrothermal carbonization of carbohydrate) and biosynthesis (i.e. use of bacterial cellulose as precursor), respectively. This Review gives a critical overview of this emerging and rapidly developing field, focusing on the synthetic strategies of the carbon-nanofiber aerogels and their outstanding physical properties. We also discuss the multifunctional application potentials of the two sorts of carbon aerogels and their nanocomposites, and highlight the challenges and future opportunities in this field.

Amending the Structure of Renewable Carbon from Biorefinery Waste-Streams for Energy Storage Applications

Biorefineries produce impure sugar waste streams that are being underutilized. By converting this waste to a profitable by-product, biorefineries could be safeguarded against low oil prices. We demonstrate controlled production of useful carbon materials from the waste concentrate via hydrothermal synthesis and carbonization. We devise a pathway to producing tunable, porous spherical carbon materials by modeling the gross structure formation and developing an understanding of the pore formation mechanism utilizing simple reaction principles. Compared to a simple hydrothermal synthesis from sugar concentrate, emulsion-based synthesis results in hollow spheres with abundant microporosity. In contrast, conventional hydrothermal synthesis produces solid beads with micro and mesoporosity. All the carbonaceous materials show promise in energy storage application. Using our reaction pathway, perfect hollow activated carbon spheres can be produced from waste sugar in liquid effluence of biomass steam pretreatment units. The renewable carbon product demonstrated a desirable surface area of 872 m²/g and capacitance of up to 109 F/g when made into an electric double layer supercapacitor. The capacitor exhibited nearly ideal capacitive behavior with 90.5% capacitance retention after 5000 cycles.

Antimicrobial carbon nanospheres

Carbon nanomaterials have found numerous applications in various fields. However, their synthesis and functionalization usually require complicated procedures or tough experimental conditions. Herein, we report for the first time the synthesis of a new type of functional nanomaterial, quaternized carbon nanospheres (QCNSs), with superior antibacterial activity via a one-pot hydrothermal treatment of chitosan and hexadecylbetaine (abbreviated as BS-16). During the hydrothermal process, the direct reaction and carbonization between the amine-containing chitosan and the carboxyl-containing BS-16 were realized within only one step. The as-prepared QCNSs feature a well-defined spherical morphology and a homogeneous size distribution with an average diameter of ∼110 nm. In particular, the QCNSs could effectively kill Gram-positive bacteria with a minimum inhibitory concentration (MIC) of 2.0-5.0 μg mL^-1. Meanwhile, the QCNSs showed excellent cytocompatibility towards normal human liver and lung cells and good hemocompatibility towards red blood cells. Moreover, in bacteria-infected macrophage cells, the QCNSs could selectively kill bacteria while the macrophage cells remained unaffected, which further confirmed their biocompatibility. Besides, we have also elucidated the antibacterial mechanism of the QCNSs by disrupting the bacterial cell walls/membranes via the bacterial adsorption and insertion of the long alkyl chain-containing quaternary ammonium groups on the particle surface. The present work provides a novel method for the preparation of functional carbon nanomaterials, which may promote the development of metal-free antibacterial agents.

Study of Preparation, Growth Mechanism and Catalytic Performance of Carbon Based Embedded Silver Nano Composite Materials

Novel and stable carbon based embedded silver nano composite materials (Ag/CSs) were successfully prepared by a facile one-pot hydrothermal method with trioctylamine (TOA) as soft template and stabilizer. These as-prepared Ag/CSs exhibit well-defined shape and relatively uniform size with an average diameter of 1.5 μm and uniformly embedded Ag nanoparticles about 5 nm. The proper proportion of glucose, AgNO3 and TOA is the key to the common growth of hydrothermal carbon materials and silver nanoparticles in an embedded way. Besides, the thickness of carbon sphere matrix and the size of Ag particles can be tailored precisely by adjusting the experimental parameters. In order to facilitate comparative analysis, carbon spheres (CSs) without Ag particles embedded were also prepared with glucose under the same hydrothermal reaction conditions. The composition, structure and morphology of the as-prepared Ag/CSs and CSs were confirmed by X-ray powder diffraction (XRD), FT-IR spectroscopy, Raman spectrum, Transmission electron microscopy (TEM) and scanning electron microscopy (SEM). In addition, the possible formation mechanism of the Ag/CSs has been proposed based on experimental evidences. Finally, the as-prepared Ag/CSs and CSs were used as catalysts in the experiments of photocatalytic degradation of methylene MB in water under visible light irradiation and the high efficiency of photocatalytic performance of Ag/CSs has been verified.

Composite Yttrium-Carbonaceous Spheres Templated Multi-Shell YVO4 Hollow Spheres with Superior Upconversion Photoluminescence

Complex oxide YVO₄ multi-shell hollow spheres with uniform morphologies and controllable shell numbers are successfully prepared by using a newly developed and general composite yttrium-carbonaceous sphere templated approach. The prominent upconversion luminous intensity of the YVO₄ :Yb³⁺ /Er³⁺ hollow spheres might be attributed to the enhanced near-infrared excitation light harvesting efficiency originated from the multiple reflections.

Nanoparticle-mediated delivery of suicide genes in cancer therapy

Conventional chemotherapeutics have been employed in cancer treatment for decades due to their efficacy in killing the malignant cells, but the other side of the coin showed off-target effects, onset of drug resistance and recurrences. To overcome these limitations, different approaches have been investigated and suicide gene therapy has emerged as a promising alternative. This approach consists in the introduction of genetic materials into cancerous cells or the surrounding tissue to cause cell death or retard the growth of the tumor mass. Despite promising results obtained both in vitro and in vivo, this innovative approach has been limited, for long time, to the treatment of localized tumors, due to the suboptimal efficiency in introducing suicide genes into cancer cells. Nanoparticles represent a valuable non-viral delivery system to protect drugs in the bloodstream, to improve biodistribution, and to limit side effects by achieving target selectivity through surface ligands. In this scenario, the real potential of suicide genes can be translated into clinically viable treatments for patients. In the present review, we summarize the recent advances of inorganic nanoparticles as non-viral vectors in terms of therapeutic efficacy, targeting capacity and safety issues. We describe the main suicide genes currently used in therapy, with particular emphasis on toxin-encoding genes of bacterial and plant origin. In addition, we discuss the relevance of molecular targeting and tumor-restricted expression to improve treatment specificity to cancer tissue. Finally, we analyze the main clinical applications, limitations and future perspectives of suicide gene therapy.

Solid-State Fabrication of SnS2/C Nanospheres for High-Performance Sodium Ion Battery Anode

Tin disulfide (SnS2) has emerged as a promising anode material for sodium ion batteries (NIBs) due to its unique layered structure, high theoretical capacity, and low cost. Conventional SnS2 nanomaterials are normally synthesized using hydrothermal method, which is time-consuming and difficult to scale up for mass production. In this study, we develop a simple solid-state reaction method, in which the carbon-coated SnS2 (SnS2/C) anode materials were synthesized by annealing metallic Sn, sulfur powder, and polyacrylonitrile in a sealed vacuum glass tube. The SnS2/C nanospheres with unique layered structure exhibit a high reversible capacity of 660 mAh g(-1) at a current density of 50 mA g(-1) and maintain at 570 mAh g(-1) for 100 cycles with a degradation rate of 0.14% per cycle, demonstrating one of the best cycling performances in all reported SnS2/C anodes for NIBs to date. The superior cycling stability of SnS2/C electrode is attributed to the stable nanosphere morphology and structural integrity during charge/discharge cycles as evidenced by ex situ characterization.

Interface-mediated fabrication of bowl-like and deflated ballon-like hollow carbon nanospheres

In our work, two kinds of hollow carbon nanospheres with controlled morphologies have been successfully prepared from low-cost and nontoxic glucose as the sole carbon precursor under neutral aqueous medium via a simple hydrothermal route. During the process, sodium dodecylbenzene sulfonate (SDBS) and triblock copolymer P123 ((EO)20(PO)70(EO)20) was skillfully selected as the structure-directing agent, respectively. SEM, TEM and AFM results revealed that the two products showed bowl-like and deflated-balloon-like morphology with uniform particle sizes, respectively. Based on the experimental observations, a possible formation mechanism was also discussed, in which the growth of the carbon nanospheres involved an interface-medicated assembly process. The present method was easy, green and mild. Apart from the unique nanostructure, the obtained bowl-like hollow carbon nanospheres exhibited excellent biocompatibility. In particular, it should be mentioned that the open window formed by the bowl-like morphology can facilitate ion transport, thus improving their performances.

An advanced MoS2 /carbon anode for high-performance sodium-ion batteries

Molybdenum disulfide (MoS2 ) is a promising anode for high performance sodium-ion batteries due to high specific capacity, abundance, and low cost. However, poor cycling stability, low rate capability and unclear electrochemical reaction mechanism are the main challenges for MoS2 anode in Na-ion batteries. In this study, molybdenum disulfide/carbon (MoS2 /C) nanospheres are fabricated and used for Na-ion battery anodes. MoS2 /C nanospheres deliver a reversible capacity of 520 mAh g(-1) at 0.1 C and maintain at 400 mAh g(-1) for 300 cycles at a high current density of 1 C, demonstrating the best cycling performance of MoS2 for Na-ion batteries to date. The high capacity is attributed to the short ion and electron diffusion pathway, which enables fast charge transfer and low concentration polarization. The stable cycling performance and high coulombic efficiency (∼100%) of MoS2 /C nanospheres are ascribed to (1) highly reversible conversion reaction of MoS2 during sodiation/desodiation as evidenced by ex-situ X-ray diffraction (XRD) and (2) the formation of a stable solid electrolyte interface (SEI) layer in fluoroethylene carbonate (FEC) based electrolyte as demonstrated by fourier transform infrared spectroscopy (FTIR) measurements.

Hydrothermal synthesis and characterization of carbon nanospheres: a mechanistic insight

SEM and PL for CNS synthesized for 4 h by hydrothermal reaction of glucose.

Tremella-like graphene–Au composites used for amperometric determination of dopamine

Tremella-like graphene–Au composites were synthesized by a one-step hydrothermal method for selective detection of DA.

Green synthesis of ZnO hollow sphere nanostructures by a facile route at room temperature with efficient photocatalytic dye degradation properties

The present work has prepared ZnO hollow spherical nanoparticles using a straightforward synthetic route and has innovatively made use of carbon spheres as a template at room temperature.

Comparison of carbon materials as electrodes for enzyme electrocatalysis: hydrogenase as a case study

We present a study of electrocatalysis by an enzyme adsorbed on a range of carbon materials, with different size, surface area, morphology and graphitic structure, which are either commercially available or prepared via simple, established protocols. We choose as our model enzyme the hydrogenase I from E. coli (Hyd-1), which is an active catalyst for H₂ oxidation, is relatively robust and has been demonstrated in H₂ fuel cells and H₂-driven chemical synthesis. The carbon materials were characterised according to their surface area, surface morphology and graphitic character, and we use the electrocatalytic H₂ oxidation current for Hyd-1 adsorbed on these materials to evaluate their effectiveness as enzyme electrodes. Here, we show that a variety of carbon materials are suitable for adsorbing hydrogenases in an electroactive configuration. This unified study provides insight into selection and design of carbon materials for study of redox enzymes and different applications of enzyme electrocatalysis.

Porous carbon spheres and monoliths: morphology control, pore size tuning and their applications as Li-ion battery anode materials

Various synthetic techniques are employed to fabricate porous carbon spheres and monoliths for improved performance as Li-ion battery anode materials.

A SnO2@carbon nanocluster anode material with superior cyclability and rate capability for lithium-ion batteries

A nanocluster composite assembled by interconnected ultrafine SnO2-C core-shell (SnO2@C) nanospheres is successfully synthesized via a simple one-pot hydrothermal method and subsequent carbonization. As an anode material for lithium-ion batteries, the thus-obtained nano-construction can provide a three-dimensional transport access for fast transfer of electrons and lithium ions. With the mixture of sodium carboxyl methyl cellulose and styrene butadiene rubber as a binder, the SnO2@C nanocluster anode exhibits superior cycling stability and rate capability due to a stable electrode structure. Discharge capacity reaches as high as 1215 mA h g(-1) after 200 cycles at a current density of 100 mA g(-1). Even at 1600 mA g(-1), the capacity is still 520 mA h g(-1) and can be recovered up to 1232 mA h g(-1) if the current density is turned back to 100 mA g(-1). The superior performance can be ascribed to the unique core-shell structure. The ultrafine SnO2 core gives a high reactive activity and accommodates volume change during cycling; while the thin carbon shell improves electronic conductivity, suppresses particle aggregation, supplies a continuous interface for electrochemical reaction and alleviates mechanical stress from repeated lithiation of SnO2.

Synthesis of monodisperse hollow carbon nanocapsules by using protective silica shells

Monodisperse hollow carbon nanocapsules (<200 nm) with mesoporous shells were synthesized by coating their outer shells with silica to prevent aggregation during their high-temperature annealing. Monodispersed silica nanoparticles were used as starting materials and octadecyltrimethoxysilane (C18TMS) was used as a carbon source to create core-shell nanostructures. These core-shell nanoparticles were coated with silica on their outer shell to form a second shell layer. This outer silica shell prevented aggregation during calcination. The samples were characterized by TEM, SEM, dynamic light scattering (DLS), UV/Vis spectroscopy, and by using the Brunauer-Emmett-Teller (BET) method. The as-synthesized hollow carbon nanoparticles exhibited a high surface area (1123 m(2) g(-1)) and formed stable dispersions in water after the pegylation process. The drug-loading and drug-release properties of these hollow carbon nanocapsules were also investigated.

Low-temperature preparation of tailored carbon nanostructures in water

The development of low-temperature carbonization procedures promises to provide novel nanostructured carbon materials that are of high current interest in materials science and technology. Here, we report a "wet-chemical" carbonization method that utilizes hexayne amphiphiles as metastable carbon precursors. Nearly perfect control of the nanoscopic morphology was achieved by self-assembly of the precursors into colloidal aggregates with tailored diameter in water. Subsequent carbonization furnished carbon nanocapsules with a carbon microstructure resembling graphite-like amorphous carbon materials.