Millimeter-scale 3D superlattice arrays composed of dense, regular, and vertically aligned gold nanorods are fabricated by evaporative self-assembly. The regular organization of the gold nanorods into a macroscopic superlattice enables the production of a plasmonic substrate with excellent sensitivity and reproducibility, as well as reliability in surface-enhanced Raman scattering. The work bridges the gap between nanoscale materials and macroscopic applications.

In this work, a novel carbon-free core-shell α-iron oxide (α-Fe2O3)@ spinel lithium titanate (Li4Ti5O12, LTO) composite has been synthesized via a facile hydrothermal process. Element mapping confirmed the core-shell structure of α-Fe2O3@LTO. The effects of various experimental parameters, including thickness of TiO2 coating, reaction temperature, and time on the morphologies of the resulted products, were systematically investigated. The electrochemical measurements demonstrate that uniform α-Fe2O3 ellipsoids are coated with LTO to avoid forming a solid electrolyte interface (SEI) layer, to reduce initial capacity loss, and to improve the reversibility of α-Fe2O3 for Li ion storage. Compared with naked α-Fe2O3 ellipsoids, the α-Fe2O3@LTO composites exhibit lower initial capacity loss, higher reversible capacity, and better cycling performance for lithium storage. The electrochemical performance of α-Fe2O3@LTO composite heavily depends on the thickness and density of LTO coating shells. The carbon-free coating of LTO is highly effective in improving the electrochemical performance of α-Fe2O3, promising advanced batteries with high surface stability and excellent security.

Layered transition-metal oxides (Li[NiMnCo]O, NMC, or NMCxyz) due to their poor stability when cycled at a high operating voltage (>4.5 V) have limited their practical applications in industry. Earlier researches have identified Mn(II)-dissolution and some parasitic reactions between NMC surface and electrolyte, especially when NMC is charged to a high potential, as primarily factors responsible for the fading. In our previous work, we have achieved a capacity of NMC active material close to theoretical value and optimized its cycling performance by a depolarized carbon nanotubes (CNTs) network and an unique "pre-lithiation process" that generates an in situ organic coating (∼40 nm) to prevent Mn(II) dissolution and minimize the parasitic reactions. Unfortunately, this organic coating is not durable enough during a long-term cycling when the cathode operates at a high potential (>4.5 V). This work attempts to improve the surface protection of the NMC532 particles by applying an active inorganic coating consisting of nanosized- and crystal-orientated LiFePO (LFP) (about 50 nm, exposed (010) face) to generate a core-shell nanostructure of Li(NiMnCo)O@LiFePO. Transmission electron microscopy (TEM) and etching X-ray photoelectron spectroscopy have confirmed an intimate contact coating (about 50 nm) between the original structure of NMC and LFP single-particle with atomic interdiffusion at the core-shell interface, and an array of interconnected aligned Li tunnels are observed at the interface by cross-sectional high-resolution TEM, which were formed by ball-milling and then strictly controlling the temperature below 100 °C. Batteries based on this modified NMC cathode material show a high reversible capacity when cycled between 3.0 and 4.6 V during a long-term cycling.

Transition metal oxide materials Li(NixMnyCoz)O2 (NMC) based on layered structures are expected to replace LiFePO4 in automotive Li-ion batteries because of their higher specific capacity and operating potential. However, the actual usable capacity is much lower than the promised theoretical value [Uchaker, E.; Cao, G. Nano Today 2014, 9, 499-524; Tarascon, J.-M.; Armand, M. Nature 2001, 414, 359-367], in addition to the often poor cycling performance and the first-cycle Coulombic efficiency, for which Mn(II)-dissolution, its immobilization in solid electrolyte interface (SEI), oxidation of electrolytes by Ni, and other parasitic process thereat have been held responsible [Zhan, C., et al. Nat. Commun. 2013, 4, 2437; Wang, L., et al. J. Solid State Electrochem. 2009, 13, 1157-1164; Lin, F., et al. Nat. Commun. 2014, 5, 4529]. Previously, we reported a composite Li(Ni0.5Mn0.3Co0.2)O2 (NMC532) depolarized by the embedded carbon nanotube (CNT) and achieved capacity close to the theoretical limit [Wu, Z., et al. Nano. Lett. 2014, 14, 4700-4706]; unfortunately, this high capacity failed to be maintained in long-term cycling due to the degrading contacts between the active ingredient and CNT network. On the basis of that NMC532/CNT composite, the present work proposes a unique "prelithiation process", which brought the cathode to low potentials before regular cycling and led to an interphase that is normally formed only on anode surfaces. The complete coverage of cathode surface by this ∼40 nm thick interphase effectively prevented Mn(II) dissolution and minimized the side reactions of Ni, Co, and Mn at the NMC interface during the subsequent cycling process. More importantly, such a "prelithiation" process activated a structure containing two Li layers near the surface of NMC532 particles, as verified by XRD and first principle calculation. Hence, a new cathode material of both high capacity with depolarized structure and excellent cycling performance was generated. This new structure can be incorporated in essentially all the NMC-based layered cathode materials, providing us with an effective tool to tailor-design future new cathode materials for lithium batteries.

Active chlorine radicals a b s t r a c tAn electrochemical process combined with ultraviolet light irradiation (UPE) using nonphotoactive dimensionally stable anodes (DSAs) like RuO 2 /Ti and IrO 2 /Ti in the presence of chlorides was investigated for ammonia degradation. In this process, the in situ electrogenerated active chlorine and in situ photogenerated chlorine radicals were responsible for the high efficiency of ammonia degradation. More than 97% of ammonia was converted to nitrogen and a significantly synergistic effect was confirmed. Compared with the single electrochemical (E) and photochemical (P) process, the degradation rates of ammonia and the average current efficiencies (ACEs) of the UPE process increased by 1.5 and 1.7 times using RuO 2 /Ti and IrO 2 /Ti electrodes, respectively. On the basis of the linear voltammograms, Electrochemical Impedance Spectra (EIS), UV-vis spectra, Electron Spin Resonance (ESR) analysis and a series of experiments designed, the synergistic mechanism was investigated. In addition, this unique process succeeded in transferring the reaction from the electrode surface to the bulk of the solution compared with the conventional photoelectrocatalytic (PEC) process. The loss of chloride decreased from 21.0% to 7.2% and the recycle of chloride was accelerated in the UPE process. Finally the effects of initial pH, current density and ammonia-nitrogen concentration were discussed. Results indicated that pH and ammonia concentration exerted little influences on the degradation rates and current density was the ''rate-determining'' factor. ª 2009 Elsevier Ltd. All rights reserved. IntroductionAmmonia, as one of the major nitrogen-containing pollutants, is a source of nutrients that may accelerate the eutrophication and algal growth in natural water (Feng et al., 2003;Nemoto et al., 2006). The abatement of ammonia in wastewater discharged has become a prime issue of environmental control. High concentrations of ammonia in wastewater effluents deplete dissolved oxygen, reduce chlorine disinfection efficiency, and exhibit acute toxicity to aquatic life. There are several methods for ammonia removal from water and wastewater, including biological process (Kalyuzhnyi et al., 2006), ammonia stripping (Bonmati and Flotats, 2003), ion exchange (Lin and Wu, 1996), breakpoint chlorination (Thomas et al., 1972), photocatalysis (Zhu et al., 2005) and electrochemical process (Chiang et al., 1995;Kim et al., 2006;Wang et al., 2006). Electrochemical method for the advanced treatment of ammonia in the wastewater has attracted a great deal of * Corresponding author. Tel.: þ86 10 62849151; fax: þ86 10 62923558. E-mail address: jhqu@rcees.ac.cn (J. Qu).A v a i l a b l e a t w w w . s c i e n c e d i r e c t . w a t e r r e s e a r c h 4 3 ( 2 0 0 9 ) 1 4 3 2 -1 4 4 0