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In this work, monodisperse polydopamine (PDA) spheres with tunable diameters have been synthesized through a facile and low cost method using a deionized water and alcohol mixed solvent. The PDA spheres possess surface functional groups (-OH, -NH(2)), exhibiting an extraordinary versatile active nature. It is demonstrated that the PDA spheres could serve as an active template for the convenient synthesis of various nanostructures, e.g., MnO(2) hollow spheres or PDA/Fe(3)O(4) and PDA/Ag core/shell nanostructures. No surface modification or special treatment is required for the synthesis of these nanostructures, which makes the fabrication process simple and very convenient. The novel application of PDA/Fe(3)O(4) spheres as fillers in nanocomposites for high-performance capacitors is demonstrated, indicating a promising practicality. The PDA spheres provide a new general platform not only for the facile assembly of nanostructures but also a green synthetic template for practical applications., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A carbon/SnO(2)/carbon core/shell/shell hybrid nanofibrous mat was successfully prepared via single-spinneret electrospinning followed by carbonization and hydrothermal treatment. The morphology and structure of carbon/SnO(2)/carbon hybrid nanofibers were characterized by field-emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, wide-angle X-ray diffraction and X-ray photoelectron spectroscopy, and their electrochemical properties were studied as an anode in lithium ion batteries (LIBs). It is shown that the designed hybrid nanofibrous mat exhibits excellent electrochemical properties, including high reversible capacity with high columbic efficiency and impressive rate capacity. The greatly enhanced electrochemical performance is mainly due to the morphological stability and reduced diffusion resistance, which are induced by both the carbon core and deposited carbon skin. Furthermore, the embedded and de-aggregated SnO(2) nanoparticles in the carbon phase, which are less than 10 nm in size, provide large numbers of reaction sites for lithium ions and ensure complete alloying with them.

The electrodes with the hierarchical nanoarchitectures could offer a huge increase in energy storage capacity. However, the ability to achieve such hierarchical architectures on a multiple scale still has remained a great challenge. In this paper, we report a scalable self-assembly strategy to create bioinspired hierarchical structures composed of functionalized graphene sheets to work as anodes of lithium-ion batteries. The resulting electrodes with novel multilevel architectures simultaneously optimize ion transport and capacity, leading to a high performance of reversible capacity of up to 1600 mAh/g, and 1150 mAh/g after 50 cycles. Importantly, the process to fabricate such hierarchical structures is facile, low-cost, green, and scalable, providing a universal approach for the rational design and engineering of electrode materials with enhanced performance, and it may have utility in various applications, including biological scaffold, catalysis, and sensors.

Thermally stable organically modified clays based on 1,3-didecyl-2-methylimidazolium (IM2C10) and 1-hexadecyl-2,3-dimethyl-imidazolium (IMC16) were used to prepare poly(ethylene naphthalate) (PEN)/montmorillonite (MMT) nanocomposites via a melt intercalation process. Examination by X-ray diffraction and transmission electron microscopy indicates that an intercalated nanocomposite was formed with IMC16-MMT, while unmodified MMT (Na-MMT) and IM2C10-MMT are generally incompatible with PEN. Thermogravimetric analysis reveals that the peak derivative weight loss temperature of the intercalated PEN/IMC16-MMT was more than 10 "C higher compared to neat PEN, PEN/Na-MMT, or PEN/IM2C10-MMT. Dynamic mechanical analysis also showed that a more significant improvement of the storage modulus was achieved in the better dispersed PEN/IMC16-MMT. The effect of annealing on the dynamic storage modulus of the hybrids is also investigated.

Poly(ethylene terephthalate) (PET)/Clay hybrids were prepared via in situ polymerization, in which the clay was modified with 12-aminododecanoic acid (ADA). Three types of bifunctional compounds were introduced into the system, respectively, as compatibilizers between PET and ADA-Clay. The three compounds contain 1 degree, 2 degree, and 3 degree amino groups, respectively, that could form ionic complex with carboxylic acid of ADA. They also contain an ester group that could react with PET chains through transesterification. The results show that adding the compound with 3 degree amino group can improve clay dispersion significantly, while the ones with 1 degree and 2 degree amino groups are not effective compatibilizers. The possible underlying mechanism is discussed.

Chemically cross-linked Si xO y cage clusters embedded in N-doped carbon were prepared by thermal treatment of octaammonium polyhedral oligomeric silsesquioxane (POSS; (SiO1.5C3H6NH3Cl)8) in an inert environment. Transmission electron microscopic studies show that by annealing at 900 °C, Si-rich clusters with a size of approximately 5 nm were formed and uniformly distributed in a lighter matrix. XPS analysis indicates that the sample obtained from annealing at 900 °C (P900) has a chemical composition of Si6.5O12.0C9.3N0.5 and it also contains substantial amounts of Si−C and C−O bonds, sp2 C, and a small number of C=N bonds, in addition to Si−O bonds. Together with thermogravimetric analysis, this suggests that the clusters are likely to be formed by chemical cross-linking several POSS cages through Si−C or C−O bonds, whereas the matrix may be N-doped carbon that results from carbonization of some detached side-chains. When used as a lithium-ion battery anode, P900 exhibits stable and high cycling and rate capacity. The capacity can be maintained for at least 1000 cycles. This is much better than results for anodes made from silicon oxides, which could be ascribed to 1) the less compact but fairly stable Si−O active sites brought by the cage structure and the cross-linking; 2) the small size of the clusters that ensures smooth and complete lithium insertion/extraction; and 3) the 'island-sea' morphology for the clusters-in-carbon hybrid that enhances interfacial interactions and facilitates charge conduction. [ABSTRACT FROM AUTHOR]

This article reports the synthesis and characterization of a quantum-confined luminescent dot with size 2-3 nm using well-defined m-octa(bromophenyl) silsesquioxane ( m-OBPS) as core. The highly regioselective bromination of octaphenylsilsesquioxane (OPS), which is an electron-deficient nanometer-sized molecule, has been synthesized using combined catalyst of iodine and zinc chloride at room temperature in dichloromethane solvent. Based on m-OBPS, a hybrid luminescent dot with well-defined structure was synthesized. UV absorption and PL spectra of this light-emitting dot remain same in dilute solution, condensed state, and solid solution. Furthermore, time-resolved PL study indicates that the exciton decay time of the light-emitting dot remains similar regardless in dilute solution, condensed state, or blended with other polymers, suggesting that the charge carriers are well confined within the individual light-emitting dot due to the unique star-like structure and shielding alkyl chain layer. The light-emitting nano-particles can be considered as isolated chromophores as both inter- and intra- molecular aggregation are prohibited. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) nanorods coated with silver (Ag) film on a polyethylene terephthalate (PET) flexible substrate were used as the photoanode for water splitting. The hybrid nanostructures were prepared via low-temperature hydrothermal growth and electron beam evaporation. The effects of plasmonic enhanced absorption, surface recombination inhibition and improved charge transport are investigated by varying the Ag thickness. Light trapping and absorption enhancement are further studied by optimizing the curvature of the PET substrates. The maximum short circuit current density (JSC, 0.616 mA cm−2) and the photoelectron conversion efficiency (PCE, 0.81%) are achieved with an optimized Ag film thickness of 10 nm and substrate bending radius of 6.0 mm. The maximum JSC and PCE are seven times and ten times, respectively, higher than those of the bare ZnO nanorods on flexible substrates without bending. The overall PEC performance improvement is attributed to the plasmonic effects induced by Ag film and improved charge transport due to inhibition of ZnO surface charge recombination. Enhanced light trapping (harvesting) induced by bending the PET substrates further improved the overall efficiency. [ABSTRACT FROM AUTHOR]

The usage of zinc oxide (ZnO)-based nanostructures in photoelectrochemical (PEC) water splitting has been well investigated yet still in keen exploration for further performance enhancement. Multi-walled carbon nanotubes (MWCNTs)-modified ZnO nanorods were prepared via hydrothermal route followed by simple solution deposition. MWCNTs were self-anchored onto the ZnO nanorods and acted as a hole-attracting phase. The PEC performance of MWCNTs-modified ZnO nanorods, including photocurrent density and photo current conversion efficiency (PCE), was found to be significantly improved compared with unmodified ones. The maximum value of PCE (0.646%), which was 2.1 times higher than that of pristine ZnO nanorods, was achieved with a MWCNTs/ethanol suspension concentration of 0.002 wt%. The performance enhancement is attributed to increasing of light absorption from rougher surface and effective charge carrier transport from the excellent conductivity of the incorporated MWCNTs. [ABSTRACT FROM AUTHOR]