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Carbonaceous materials have been recognized as one of the most promising anode materials for potassium-ion batteries (PIBs) due to their abundant raw materials, controllable structure, superior conductivity, and good chemical inertness. However, the large radius of K ions and the low potassium content of intercalation compounds result in the sluggish storage kinetics and low reversible capacity of carbon anodes. In this work, we present a unique heteroatom-doped carbon composite (denoted as NS-MC/SC) through a facile interfacial assembly route and simple heat-treatment process, where NS-MC is well grafted onto the biomass-derived spore carbon (SC). This unique structural design endows it with abundant mesoporous channels, expanded layer spacing, and highly doped N and S. With these merits, the NS-MC/SC anode in PIBs exhibits a high reversible capacity of 350.4 mAhg−1 at 100 mAg−1 after 300 cycles, and an outstanding cycling stability. Besides, in-situ Raman spectra further verify the high reversibility of K ions insertion/extraction. Importantly, theoretical simulations also reveal that the N,S dual-doping is an efficient approach for improving the potassium-ion storage performance of NS-MC/SC. [ABSTRACT FROM AUTHOR]

Mesoporous carbon nanomaterials have shown a great application potential in energy storage and conversion fields due to their outstanding conductivity, tunable pore structure, and good chemical stability. Nevertheless, how to accurately control the pore structure, especially directly assembling the mesoporous carbon onto different substrates remains a big challenge. Herein, we have successfully assembled two kinds of highly nitrogen-doped mesoporous carbon onto carbon nanotubes (NMC/CNTs) based on a facile cooperative assembly process assisted by triblock PEO20PPO70PEO20 (P123) and PEO106PPO70PEO106 (F127) copolymers. The experimental results indicate that the P123/F127 mass ratio has a profound effect on the pore structure, leading to the formation of NMC/CNTs composites with spherical pore structure (S-NMC/CNTs) and cylindrical pore structure (C-NMC/CNTs). In virtue of fast electron/ion transfer kinetics, the as-prepared S-NMC/CNTs anode demonstrates an excellent electrochemical performance for lithium-ion batteries, and it delivers a high reversible capacity of 588.1 mAh·g−1 at the current of 0.1 A·g−1 after 100 cycles, along with a superior cycling stability. Specifically noted, the controlled assembly route developed in our work can also be applied to other support materials with different structures and compositions. [ABSTRACT FROM AUTHOR]

Highlights: The synthetic strategies and fundamental mechanisms of various asymmetric carbon- and silica-based nanomaterials were systematically summarized. The advantages of asymmetric structure on their related applications were clarified by some representative applications of asymmetric carbon- and silica-based nanomaterials. The future development prospects and challenges of asymmetric carbon- and silica-based nanomaterials were proposed. Carbon- and silica-based nanomaterials possess a set of merits including large surface area, good structural stability, diversified morphology, adjustable structure, and biocompatibility. These outstanding features make them widely applied in different fields. However, limited by the surface free energy effect, the current studies mainly focus on the symmetric structures, such as nanospheres, nanoflowers, nanowires, nanosheets, and core–shell structured composites. By comparison, the asymmetric structure with ingenious adjustability not only exhibits a larger effective surface area accompanied with more active sites, but also enables each component to work independently or corporately to harness their own merits, thus showing the unusual performances in some specific applications. The current review mainly focuses on the recent progress of design principles and synthesis methods of asymmetric carbon- and silica-based nanomaterials, and their applications in energy storage, catalysis, and biomedicine. Particularly, we provide some deep insights into their unique advantages in related fields from the perspective of materials’ structure–performance relationship. Furthermore, the challenges and development prospects on the synthesis and applications of asymmetric carbon- and silica-based nanomaterials are also presented and highlighted. [ABSTRACT FROM AUTHOR]

Owing to excellent conductivity and abundant surface terminals, MXene-based heterostructures have been intensively investigated as energy storage materials. However, elaborate design of the structure and composition of MXene-based hybrids towards superior electrochemical performance is still challenging. Herein, we present an ingenious leaf-inspired design for preparing a unique Sb2S3/nitrogen-doped Ti3C2Tx MXene (L-Sb2S3/Ti3C2) hybrid. In-situ TEM observations reveal that the leaflike Sb2S3 nanoparticles with numerous mesopores can well relieve the large volume changes via an inward pore filling mechanism with only 20% outward expansion, whereas highly conductive N-doped Ti3C2Tx nanosheets can serve as the robust mechanical support to reinforce the structural integrity of the hybrid. Benefiting from the structural and constituent merits, the L-Sb2S3/Ti3C2 anode fabricated exhibits a fast sodium storage behavior in terms of outstanding rate capability (339.5 mA h g−1 at 2,000 mA g−1) and high reversible capacity at high current density (358.2 mA h g−1 at 1,000 mA g−1 after 100 cycles). Electrochemical kinetic tests and theoretical simulation further manifest that the boosted electrochemical performance mainly arises from such a unique leaf-like Sb2S3 mesoporous nanostructure with abundant active sites, and enhanced Na+ adsorption energy on the heterojunction formed between Sb2S3 nanoparticles and Ti3C2 matrix. [ABSTRACT FROM AUTHOR]

Resorcinol–formaldehyde (RF) aerogels are widely used as thermal insulation materials. The present investigation of RF aerogels emphases on improving hydrophobic property and high-temperature residual yields. In this study, polysiloxane-modified RF composite xerogel monoliths were prepared by gelation of poly(methylphenylsiloxane) prepolymer with RF in cosolvent and ambient pressure drying. The influence of phenyl content on structure and thermal property of xerogels was investigated. The as-prepared RF composite monoliths were lightweight and hydrophobic with density lower than 0.300 g/cm3 and water contact angles approaching 130°. Morphology analyses indicated that polysiloxane grew and formed a continuous layer on RF porous skeleton with controlled reaction parameter. Thermogravimetry analyses (TGA) certified that the controlled incorporation of polysiloxane in composite xerogels enhanced the thermal degradation temperature at which the weight loss of RF xerogels reaches 5% (T5%) and increased the residual yields at 1000 °C. The carbonized derivatives were obtained for further enhancing the thermal stability by removal of small molecules during carbonization. Xerogel monoliths preserved hydrophobic property till 500 °C carbonization due to the thermal stability of poly(methylphenylsiloxane). The heat-resistant composite xerogels remained monolith structure after 800 °C treatment under nitrogen condition. Highlights: Heat-resistant and hydrophobic xerogel monoliths were prepared by ambient drying. The temperature at which the weight loss of RF xerogels reaches 5% was increased by the controlled incorporation of poly(methylphenylsiloxane). Composite xerogels preserved hydrophobicity after 500 °C carbonization. Macroscale separation of polysiloxane and resorcinol–formaldehyde was resisted. [ABSTRACT FROM AUTHOR]

Intracellular glutathione (GSH) sensing was important for monitoring many diseases and health of cell. In this study, we prepared surface-functionalized Ti3C2 quantum dots (QDs) by ultrasonic cutting and hydrothermal method. Bright excitation wavelength-dependent blue emission was observed in Ti3C2 QDs which was attributed to surface defects and quantum confinement effects. Furthermore, we developed a novel fluorescence sensor that can detect GSH with high sensitivity, based on the fluorescence resonance energy transfer process from Ti3C2 quantum dots to GSH, with a detection limit of 0.02 μM approximately. This novel Ti3C2 QD can be used as a promising fluorescent sensor for practical applications. [ABSTRACT FROM AUTHOR]

Hollow nanostructures have attracted considerable attention owing to their large surface area, tunable cavity, and low density. In this study, a unique flower-like C@SnO@C hollow nanostructure (denoted as C@SnO@C-1) was synthesized through a novel one-pot approach. The C@SnO@C-1 had a hollow carbon core and interlaced petals on the shell. Each petal was a SnO nanosheet coated with an ultrathin carbon layer ~2 nm thick. The generation of the hollow carbon core, the growth of the SnO nanosheets, and the coating of the carbon layers were simultaneously completed via a hydrothermal process using resorcinol-formaldehyde resin-coated SiO nanospheres, tin chloride, urea, and glucose as precursors. The resultant architecture with a large surface area exhibited excellent lithium-storage performance, delivering a high reversible capacity of 756.9 mA·h·g at a current density of 100 mA·g after 100 cycles. [ABSTRACT FROM AUTHOR]

The assembly of hybrid nanomaterials has opened up a new direction for the construction of high-performance anodes for lithium-ion batteries (LIBs). In this work, we present a straightforward, eco-friendly, one-step hydrothermal protocol for the synthesis of a new type of FeO-SnO/graphene hybrid, in which zero-dimensional (0D) SnO nanoparticles with an average diameter of 8 nm and one-dimensional (1D) FeO nanorods with a length of ~150 nm are homogeneously attached onto two-dimensional (2D) reduced graphene oxide nanosheets, generating a unique point-line-plane (0D-1D-2D) architecture. The achieved FeO-SnO/graphene exhibits a well-defined morphology, a uniform size, and good monodispersity. As anode materials for LIBs, the hybrids exhibit a remarkable reversible capacity of 1,530 mA·g at a current density of 100 mA·g after 200 cycles, as well as a high rate capability of 615 mAh·g at 2,000 mA·g. Detailed characterizations reveal that the superior lithium-storage capacity and good cycle stability of the hybrids arise from their peculiar hybrid nanostructure and conductive graphene matrix, as well as the synergistic interaction among the components. [ABSTRACT FROM AUTHOR]

Thermally stable methylsilicone xerogel monoliths were prepared by sol-gel technology with methylsilicone oligomer as precursor and titania nanoparticles as filler. The effects of titania doping and heating temperature on the structure, morphology, and hydrophobic property of xerogels were investigated. The structural evolution under thermal treatment showed that the blank methylsilicone monolith was crushed after 300 °C treatment, but the samples reinforced by titania could retain the intact structure after 500 °C treatment. Thermogravimetric analysis results certified that the thermal degradation of methylsilicone was resisted due to incorporation of TiO. Fourier transform infrared spectra and Si nuclear magnetic resonance results showed that Si-CH unit still existed in the reinforced samples, compared with the complete transformation of Si-C to Si-O in the blank methylsilicone after 500 °C treatment. Thus, the hydrophobic property was preserved and certified by measurement of contact angle. [ABSTRACT FROM AUTHOR]

In the work, an in situ chemical synthesis approach has been developed to fabricate SnO2/reduced graphene oxide nanocomposites in ethanol solution. X-ray diffraction, x-ray photoelectron, Fourier transform infrared and Raman spectrum revealed the formation of SnO2/reduced graphene oxide nanocomposites. Scanning electron microscopy and transmission electron microscopy showed that SnO2 nanoparticles had a crystal size of about 3–4 nm and homogeneously distributed on reduced graphene oxide matrix. The electrochemical performances of the SnO2/reduced graphene oxide nanocomposites as anode materials were measured by the galvanostatic charge/discharge cycling. The results indicated that as-synthesized SnO2/reduced graphene oxide nanocomposites had a reversible lithium storage capacity of 1051 mAh/g and an enhanced cyclability, which can be attributed to increased electrode conductivity and buffer effect to volume change in the presence of a percolated reduced graphene oxide network embedded into the metal oxide electrodes. [ABSTRACT FROM PUBLISHER]

The mesoporous and nanorods SnO2 are synthesized by controlling the state of SnCl2·2H2O precursor with SBA-15 as hard template, and the possible formation mechanisms at different assembling modes inside the ordered mesoporous silica templates are proposed. In addition, SnO2 nanoparticles are synthesized by hydrolysis depositing method. The electrochemical tests of as-prepared samples indicate that the reticular stacking structure of the nanorods would limit the Li+ ions to intercalate, but the effect of volume expansion in this case upon cycling is insignificant. The mesostructure SnO2 tends to be stable after partial structural collapse at first few cycles. And the Li+ ions can readily intercalate and de-intercalate into/from its ordered channels structure, which provides a high capacity and an improved cycle property. Although SnO2 nanoparticles deliver high capacity at an early stage, the agglomeration may induce the capacity to drop rapidly after a certain number of cycles. [ABSTRACT FROM PUBLISHER]

FeO/polyaniline (PANI) composite hollow spheres were prepared by using sulfonated polystyrene (SPS) microspheres as templates. The sulfonic acid groups were applied to induce absorbing FeO nanoparticle, and subsequently, conductive PANI was grown. Finally, the polystyrene cores were selectively dissolved to yield composite hollow microspheres with electromagnetic properties. The analysis results indicated that the adsorption of FeO on template core by electrostatic interaction resulted in magnetic composite microspheres. The conductivity of composite hollow spheres was remarkably increased after polyvinylpyrrolidone modification which favored the growth of PANI on SPS/FeO and enhanced the integrity of hollow microspheres. The saturated magnetization of the composite hollow microspheres was tuned from 2.7 to 9.1 emu/g, and the conductivity was in the range from 10 to 10 S/cm. [ABSTRACT FROM AUTHOR]

The porous Li1.2Ni0.13Co0.13Mn0.54O2 nanoplate is prepared by colloidal crystal template assembled by the poly (methyl methacrylate) (PMMA) beads. Scanning electron microscopy and transmission electron microscopy results show that the nanoplates of porous solid solution cathodes are composed of nanoparticles with a size range of 30 nm, which interweave together forming an open porous structure. Electrochemical tests show that porous Li1.2Ni0.13Co0.13Mn0.54O2 cathode could deliver higher discharge capacity than that of bulk Li1.2Ni0.13Co0.13Mn0.54O2 cathode at all C-rates. The enhanced structural stability reflected by high ratios of integrated Intensity I(003)/I(104) and lattice parameters c/a, high specific surface area, a fast reaction and ionic diffusion kinetics of the nanoplates are considered attributable to the improved electrochemical properties. [ABSTRACT FROM AUTHOR]

TiO/graphene composite photocatalysts have been prepared by a simple liquid phase deposition method using titanium tetrafluoride and electron beam (EB) irradiation-pretreated graphene as the raw materials. The products were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The effects of varying the synthesis parameters such as graphene content, concentration of titanium tetrafluoride solution and irradiation dose were investigated. It was found that the preparation conditions had a significant effect on the structure and properties of the final products. The irradiated graphene was covered with petal-like anatase TiO nanoparticles, which were more uniform and smaller in size than those in products synthesized without EB irradiation-pretreated graphene. The photocatalytic activities of the products were evaluated using the photocatalytic degradation of methyl orange as a probe reaction. The results showed that the products synthesized using EB irradiation-pretreated graphene exhibited higher photocatalytic activities than those using graphene without EB irradiation pretreatment. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]