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This study systematically evaluates Neodymium (Nd) recovery from actual seawaters and wastewater using functionalized magnetic ferrite (3-mercaptopropionic acid-tetraethyl orthosilicate ferrite, MPA-TEOS-ferrite). The recovery of Nd by MPA-TEOS-ferrite displayed an L-shaped nonlinear isotherm, suggesting limiting binding sites on the adsorbent surface. At room temperature, a significant recovery of Nd by MPA-TEOS-ferrite increased from 8.99% to 99.99% with increasing pH (2.89-8.16) and an enhanced maxima Nd recovery capacity was observed on MPA-TEOS-ferrite (25.58 mg/g) when compared with pure ferrite (22.27 mg/g). The L3-edge X-ray absorption near-edge structure (XANES) spectra for the adsorbents collected after Nd recovery indicated that Nd(III) was still the predominant oxidation species on the surface of MPA-TEOS-ferrite. Only slightly change in the oxidation state or electronic structure around the Nd ions could be found during the adsorption process. Importantly, no significant change was found on Nd recovery while the NaCl ionic strength increased from 0.01 to 0.5 N. Furthermore, the results also displayed that the synthesized MPA-TEOS-ferrite has a great potential in efficient and rapid recovery of Nd from seawaters and wastewater. more...

We report the phonon and magnetic properties of various well-stabilized Co3O4 nanoparticles. The net valence in cobalt (II)/(III) cation can be obtained by subtracting the Co2+ ions in tetrahedral interstices and Co3+ ions in the octahedral interstices, respectively, which will possess spatial inhomogeneity of its magnetic moment via Co2+ in tetrahedra and Co3+ in octahedral configurations in the normal spinel structure. Furthermore, the distribution of Co2+/Co3+ governed by various external (magnetic field and temperature) and internal (particle size and slightly distorted CoO6 octahedra) sources, have led to phenomena such as a large redshift of phonon-phonon interaction and short-range magnetic correlation in the inverse spinel structure. The outcome of our study is important in terms of the future development of magnetic semiconductor spintronic devices of Co3O4. more...

Developing efficient and durable bifunctional electrocatalysts for oxygen reduction and evolution reaction (ORR/OER) is highly desirable in energy conversion and storage systems. This study prepares nickel–ruthenium layered double hydroxide (NiRu-LDHs) nanosheets subjected to decoration with conductive silver nanoparticles (Ag NP/NiRu-LDHs), which interestingly induce their multivacancies associated with catalytic site activity and populations. The as-prepared Ag NP/NiRu-LDH shows excellent catalytic activity toward both OER and ORR features with low onset overpotentials of 0.21 V and −0.27 V, respectively, with a 0.76 V potential gap between OER potential at 10 mA cm–2 and ORR potential at −3 mA cm–2, demonstrating that it is the preeminent bifunctional electrocatalyst reported to date. Compared with pristine NiRu-LDHs, the resulting Ag NP/NiRu-LDHs nanosheets require only an overpotential of 0.31 V to deliver 10 mA cm–2 with excellent durability. The superb bifunctional performance of Ag NP/NiRu-LDH is ... more...

Excellent thermoelectric performance has been reported for the ZrCuSiAs-type BiCuOSe derivatives; for these materials the transport properties can be effectively adjusted by chemical substitutions or by introducing Cu vacancies. In this work we compare stoichiometric BiCuSeO and its Cu-deficient derivative BiCu0.95SeO by utilizing temperature-dependent extended X-ray absorption fine structure (EXAFS) measurements. Such a local probe evidences that Cu vacancies make the lattice more ductile and susceptible to temperature variation. more...

This study addresses the issue of whether the magnetite Fe3O4 nanoparticle shows a true spin-glass like behavior or if this is an artifact of interparticle interaction. Transmission electron microscopy and X-ray diffraction pattern analysis confirms the formation of pseudospherical Fe3O4 nanoparticles with a grain size of 8(1) nm. The magnetic moment relaxation M(t) follows a stretched exponential and power law function, confirming the presence of multiple-magnetic anisotropic barriers (β = 0.51(1)) and weak-interparticle interaction (n = 0.60(4)). The observed field cooling (FC) memory effect occurs because of the presence of magnetic anisotropy arising from a broad size distribution and weak-interparticle interactions. The absence of the zero-field-cooled (ZFC) memory effect signals that the Fe3O4 nanoparticle system is not a true spin-glass system, and the observed decreasing behavior of magnetization in FC measurement is an artifact of the weak-interparticle interaction. more...

One of the key challenges in artificial photosynthesis is to design a photocatalyst that can bind and activate the CO

We report the phonon and magnetic properties of various well-stabilized Co3O4 nanoparticles. The net valence in cobalt (II)/(III) cation can be obtained by subtracting the Co2+ ions in tetrahedral interstices and Co3+ ions in the octahedral interstices, respectively, which will possess spatial inhomogeneity of its magnetic moment via Co2+ in tetrahedra and Co3+ in octahedral configurations in the normal spinel structure. Furthermore, the distribution of Co2+/Co3+ governed by various external (magnetic field and temperature) and internal (particle size and slightly distorted CoO6 octahedra) sources, have led to phenomena such as a large redshift of phonon-phonon interaction and short-range magnetic correlation in the inverse spinel structure. The outcome of our study is important in terms of the future development of magnetic semiconductor spintronic devices of Co3O4. more...

The behaviour of arsenic (As) from geogenic soil exposed to aerobic conditions is critical to predict the impact of As on the environment, which processes remain unresolved. The current study examined the depth profile of As in geologically derived subsoil cores from Hong Kong and investigated the mobilization, plant availability, and bioaccessibility of As in As-contaminated soil at different depths (0-45.8 m). Results indicated significant heterogeneity, with high levels of As in three layers of soil reaching up to 505 mg/kg at a depth of 5 m, 404 mg/kg at a depth of 15 m, and 1510 mg/kg at a depth of 27-32 m. Arsenic in porewater samples was11.5 μg/L in the study site. X-ray absorption spectroscopy (XAS) indicated that main As species in soil was arsenate (As(V)), as adsorbed fraction to Fe oxides (41-69% on goethite and 0-8% on ferrihydrite) or the mineral form scorodite (30-57%). Sequential extraction procedure demonstrated that 0.5 ± 0.4% of As was exchangeable. Aerobic incubation experiments exhibited that a very small amount (0.14-0.48 mg/kg) of As was desorbed from the soil because of the stable As(V) complex structure on abundant Fe oxides (mainly goethite), where indigenous microbes partly (59 ± 18%) contributed to the release of As comparing with the sterilized control. Furthermore, no As toxicity in the soil was observed with the growth of ryegrass. The bioaccessibility of As was27% in the surface soil using simplified bioaccessibility extraction test. Our systematic evaluation indicated that As in the geogenic soil profile from Hong Kong is relatively stable exposing to aerobic environment. Nevertheless, children and workers should avoid incidental contact with excavated soil, because high concentration of As was present in the digestive solution (0.1-268 μg/L). more...

Single-component, single-activator-converted high-color-rendering index (CRI) white-light phosphors have sparked much interest for phosphor-converted white light-emitting diodes. However, manipulating the distribution and locations of single activators to target desired sites in a given host lattice is still a challenge. Herein, we report the remote regulation of the distribution of Eu2+ ions by engineering and controlling the structural ordering in Sr3(Ce1−xLax)(PO4)3:0.05Eu2+ (SCLP:Eu2+) compound, which are designed by using two-color phosphors with different anionic structural ordering, viz., Sr3Ce(PO4)3:Eu2+ (yellow) with disordered state of PO4 tetrahedra, and Sr3La(PO4)3:Eu2+ (blue) with ordered state of PO4 tetrahedra. The successive substitution of Ce by La triggers a pronounced disorder-to-order structural transformation of PO4 tetrahedra within SCLP:Eu2+ compounds and guides remotely the distribution of Eu2+ activators, which is demonstrated by a detailed analysis of synchrotron X-ray diffraction refinement, electron paramagnetic resonance spectra, electron spin-echo envelope modulation spectra, Raman spectra, nuclear magnetic resonance spectra and micro-cathodoluminescence spectrum. Benefitting from the controllable structural ordering transformation, as-prepared samples form a unique disorder-order crystal structure, exhibiting controllable microstructure acting on Eu2+ ions, tunable-color emissions including a high CRI (Ra = 90) white-light, increased structural rigidity and thermal stability. These interesting findings in the local structure-dependent luminescence properties demonstrate that structural ordering engineering may be an effective approach to regulate the migration of Eu2+ activators and improve the thermal stability of phosphors. more...

We report the remarkable production of H2 and H2O2 from pure water using porous brookite TiO2 nanoflutes decorated with Pt nanoparticles through two-electron photocatalytic intermediate water splitting (PIWS). The H2 production rate from deionized water (pH ~7.0) was 9.8 ± 0.6 μmol mg−1 h−1, more than 12-fold and 230-fold higher than the reported TiO2-based photocatalytic overall water splitting (POWS) and H2/H2O2 production systems, respectively. The apparent quantum yields (AQY) value can achieve 43.4%, which is the highest value compared with the reported TiO2-based POWS systems and the commercial value for PIWS is ~9-fold higher than that for POWS even ignoring the separation cost. The mechanism of the distinct performance was confirmed by DFT and experimental measurements. The present work provides a feasible strategy to significantly improve the process efficiency and value of photocatalytic water splitting in both pure water and seawater using natural sunlight. more...

A novel reddish-orange-emitting BaLa2Si2S8:Eu(2+) thiosilicate was prepared in a sealed fused silica ampule and its crystal structure was refined using Rietveld methods. The BaLa2Si2S8:Eu(2+) phosphor is excitable over a broad range from UV to blue (350-450 nm) and generated a reddish-orange broadband emission peaking at 645 nm with a quantum efficiency of ∼24%. The thermal luminescence quenching of BaLa2Si2S8:Eu(2+) was investigated over the range 25 to 150 °C. This phosphor was utilized to incorporate with two commercially available phosphors, blue BaMgAl10O17:Eu(2+) and green (Ba,Sr)2SiO4:Eu(2+), and a near-UV LED chip (405 nm), a white light with Ra of ∼94 was obtained. more...

The synthesis and component of red phosphor, Sr4Al14O25: Mn, were optimized for application in white light-emitting diodes. The microstructure and morphology were investigated by the X-ray diffraction and scanning electron microscopy. Different valences of Mn ions in Sr4Al14O25 were discriminated using the electron paramagnetic resonance and X-ray absorption near-edge structure spectroscopy techniques. The bond-valence theory was used to analyze the effective valences of Sr2+ and Al3+ in Sr4Al14O25. As a result, the strong covalence of Al3+ in the AlO4 tetrahedron other than in the AlO6 octahedron is disclosed. The deep red emission is attributed to Mn4+ occupying the center of AlO6 octahedron. The mechanism of energy transfer is mainly through dipole–dipole interaction, revealed by the analyses of critical distance and concentration quench. A high color rendering white LED prototype with color-rendering index up to Ra 93.23 packaged by using the red phosphor demonstrates its applicability. more...

In this work, the crystal field stabilization energy ( D q ) and the Racah B and C parameters were calculated quantitatively to evaluate the nephelauxetic effect of Mn 4+ suffering from the Sr 4 Al 14 O 25 host, aiming for developing novel highly efficient red phosphor for white light-emitting diodes. The phosphor of Mn 4+ activated Sr 4 Al 14 O 25 was synthesized via a high temperature solid reaction in air ambient. The crystallinity was investigated using the X-ray diffraction; and the photoluminescence properties were characterized with the spectrometer. The red emission was attributed to the Mn 4+ which occupies the center of AlO 6 octahedron. Meanwhile, the Mn 2+ and Mn 3+ were detected by using the X-ray absorption near-edge structure spectroscopy (XANES) assisted with Electron Paramagnetic Resonance (EPR) techniques. The energy levels of 4 A 2 , 4 T 2g and 4 T 1g were determined according to excitation spectra, corresponding to the 4 A 2 (t 2 3 ) → 4 T 1 ( 4 F) and the 4 A 2 (t 2 3 ) → 4 T 2g (t 2 2 e) transitions at 330 and 450 nm respectively, whereby the calculation was carried out according to the Tanabe–Sugano diagram for octahedral complex with the d 3 electron configuration. The nephelauxetic ratio β about 0.32 suggests a strong cloud expansion of Mn 4+ in the Sr 4 Al 14 O 25 crystal lattice with D q ∼ 2222 cm −1 , B ∼ 794 cm −1 , C ∼ 3232 cm −1 and C / B ∼ 4.07. In the perspective of physics, these parameters are helpful to perceive the inter-repulsion of the outer electrons in 3 d orbit of Mn 4+ and the effect of local circumstance, in essential to understand the variant spectral configurations of Mn 4+ luminescence observed in different hosts. more...

This study investigates the effect of Fe(3+) on the electronic structure of nanocrystalline ceria. Systematic synchrotron X-ray absorption spectroscopy coupled with scanning transmission electron microscopy/electron energy loss spectroscopy was utilized. The oxygen vacancies can be engineered and their number varied with the degree of iron doping. Comparing the local electronic structure around Ce sites with that around Fe sites reveals two stages of defect engineering. The concentration of Ce(3+) and the distribution of defects differ between lower and higher degrees of doping. Charge is transferred between Ce and Fe when the doping level is less than 5%, but this effect is not significant at a doping level of over 5%. This transfer of charge is verified by energy loss spectroscopy. These Fe-modified ceria nanoparticles exhibit core-shell-like structures at low doping levels and this finding is consistent with the results of scanning transmission electron microscopy/electron energy loss spectroscopy. More Fe is distributed at the surface for doping levels less than 5%, whereas the homogeneity of Fe in the system increases for doping levels higher than 5%. X-ray magnetic circular dichroism spectroscopy reveals that Ce, rather than Fe, is responsible for the ferromagnetism. Interestingly, Ce(3+) is not essential for producing the ferromagnetism. The oxygen vacancies and the defect structure are suggested to be the main causes of the ferromagnetism. The charge transfer and defect structure Fe(3+)-Vo-Ce(3+) and Fe(3+)-Vo-Fe(3+) are critical for the magnetism, and the change in saturated magnetization can be understood as being caused by the competition between interactions that originate from magnetic polarons and from paired ions. more...

An efficient Molybdenum (Mo) removal technology in aqueous solutions was developed for the first time using nano-magnetic CuFe 2 O 4 manufactured from printed circuit board (PCB) industrial sludge. This nano-magnetic CuFe 2 O 4 adsorbent displayed a nonlinear L-type isotherm that fitted well with the Langmuir isotherm, suggested limited adsorption sites and monolayer sorption on surface. The K -edge X-ray absorption near-edge structure (XANES) spectra demonstrated that Mo(VI) was the predominant oxidation species on nano-magnetic CuFe 2 O 4 and the maximum adsorption capacity was found to be 30.58 mg g −1 at pH 2.75. When pH became higher, more negative charges would occur at the surface of adsorbent and lead to more electric repulsion. Consequently, Mo adsorption was sharply reduced in alkaline condition. Importantly, these adsorbed Mo anions were replaced easily by OH − ions in NaOH solution and showed huge potential for removal/concentration of Mo in industrial wastewater, groundwater, and tap water. This unique Mo separation technique can also be potentially applied for geochemical investigation in various natural aqueous solutions. more...

Cu–Al–O thin films are deposited on (0001) sapphire substrates by radio-frequency sputtering using an Al–Cu mosaic target. The Cu/Al atomic ratio of as-deposited Cu–Al–O films is measured to be 1.1. After deposition, the Cu–Al–O films are annealed at 600, 800, and 1000 °C, respectively, for 1 h in a N 2 atmosphere. The film crystal structure, electronic structure, valence band, and electrical properties are studied. The as-deposited films are amorphous and films annealed at 600 °C contain the crystallized CuO phase; the structure becomes crystallized CuAlO 2 after annealing at 800 °C and 1000 °C. The 800 °C annealed film grows along the (00 l ) plane. The crystallization decreases with the growth of the (012) and (018) planes for films annealed at 1000 °C. The resistivity values of the 800 °C and 1000 °C annealed films were measured as 1.07 Ω-cm and 864.01 Ω-cm, respectively. The lower resistivity of the 800 °C annealed film is attributed to preferred (00 l ) growth orientation and a reduction of the energy band gap. more...

Symmetry and conservation dominate modern fundamental physics both in quantum mechanics and in relativity theories. Symmetry stems from theoretical assumptions of no observability. No observability means symmetry. On the other side, any discovery of symmetry breaking suggests the existence of a specific measurement. In article number 1802126, Lei Chen, Guobao Li, Oliver Oeckler, and co‐workers demonstrate not only the existence of symmetry breaking in the lithium compound Li2SrSiO4, but also provide a powerful, but facile, optical tool to detect symmetry breaking. more...

Novel promising blue MSiAl2O3N2:Ce3+ (M = Sr, Ba) and green BaSiAl2O3N2:Eu2+ oxynitride phosphors with broad band emission for white light-emitting diodes are obtained in this study. The detailed energy transfer mechanism from Ce3+ to Eu2+ in SrSiAl2O3N2 is reported. Moreover, the unexpected red shift emission when the compositional variable x is increased from 0 to 0.92 in the Sr0.92-xBaxSiAl2O3N2:Ce3+0.04,Eu2+0.04 system is well investigated. The decrease in emission energy and the increase in thermal quenching barrier height of x are caused by a dominant chemical pressure compression effect on the activator sites, through which the replacement of Sr2+ (occupied by activators) by larger Ba2+ enhances the covalency of Sr–N/O bonding in spite of unit cell enlargement. The chemical pressure compression effect control for photoluminescence is verified by the ionic-radii equilibrium between 9-coordinate IXSr2+ and (IXCa2+, IXBa2+). more...

Ruthenium (Ru = 0%, 1% and 2%) doped nano-crystalline zinc oxide (ZnO) nanorods were synthesized by using well-known sol–gel technique. X-ray diffraction (XRD) results show that Ru (0%, 1% and 2%) doped ZnO nanorods crystallized in the wurtzite structure having space group C3v (P63mc). Williamson and Hall plot reveal that in the nanoscale dimensions, incorporation of Ru induced the tensile strain in ZnO host matrix. Photoluminescence (PL) and Raman studies of Ru doped ZnO nanorods show the formation of singly ionized oxygen vacancies which may account for the observed room temperature ferromagnetism (RTFM) in 2% Ru doped ZnO. X-ray absorption spectroscopy (XAS) reveals that Ru replace the Zn atoms in the host lattice and maintain the crystal symmetry with slightly lattice distortion. more...

We report the influence of the nanosized effect on the optical properties of non-centrosymmetric ZnO nanoparticles. In this study confocal Raman scattering was employed to investigate the strain effect of the softening A1(LO) phonon mode while controlling particle sizes from 55 ± 1 to 32 ± 1 nm. The observations reveal a positive Poisson ratio between the compressive- and tensile-strain. The intensity ratio of the A1(2LO)/A1(LO) modes exhibits strong size dependence. As the particle sizes decrease further, the ratio decreases rapidly, signaling the short-range electron–phonon coupling effect which confines the electrons and holes within a smaller volume. An energy red-shift in the photoluminescence peak was observed, because of a lowering in the strain of local symmetry at O2− sites caused by excess oxygen, and by strong coupling between the electron and phonon vibration. The variation of the bandgap is very sensitive to the electron–phonon coupling and the distinct size effect of strained ZnO nanoparticles. more...

This study examines Al-doped ZnO (AZO) transparent conductive thin films prepared on glass substrate using the pulsed laser deposition method with an expanding magnetic field perpendicular to the sample surface. O K-, Zn L3-, and Al K-edge X-ray absorption near-edge structure (XANES) and X-ray emission spectroscopy (XES) were used to investigate the relationship between the effects of magnetic field size and the electronic structure of AZO thin films. Analysis of the XANES spectra showed increasing O 2p states as film resistance decreases, suggesting that the enrichment of the O 2p-dangling bond along the c-axis is the main factor affecting the electric performance of AZO thin films. Magnetic field size affects electrons itinerating from Zn atoms to Al sites through O 2p–Zn 3d and O 2p–Al 3sp hybridization and consequently weakens O 2p–Zn 3d hybridization with the downsizing of the crystallite size. XES and XANES spectra of O 2p states at the O K-edge exhibit that the conduction-band minimum affects Eg and the valence-band maximum is nearly unaffected by changes in magnetic field size. Factors affecting the resistance/electric conductivity of AZO thin films are the preferential orientation of (002) along the c-axis, the thermal/annealing effect accompanied by the changes of magnetic field size, the surface effect, energy bandgap, and the density of unoccupied O 2p-derived states. more...

Among the thermoelectric misfit-layered cobalt oxides, [MmA2Om+2]qCoO2, the parent m=0 phases exhibit divergent chemical features but are less understood than the more common m>0 members of the series. Here we synthesize Sr-for-Ca substituted [(Ca1−xSrx)z(O,OH)2]qCoO2 zero phases up to x=0.2 through low-temperature hydrothermal conversion of precursor powders of the m=1 misfit system, [Co(Ca1−xSrx)2O3]qCoO2. In the zero-phase [(Ca1−xSrx)z(O,OH)2]qCoO2 system, as the Sr content x increases the lattice expands anisotropically along the c axis such that the ab-plane dimension and the misfit parameter q remain essentially constant. X-ray absorption spectroscopy data suggest the presence of peroxide-type oxygen species in the (Ca1−xSrx)z(O,OH)2 rock-salt block and together with infrared spectroscopy, thermogravimetric and low-temperature resistivity and thermopower measurements evidence that the isovalent Sr-for-Ca substitution controls the balance between the peroxide and hydroxide species in the (Ca1−xSrx)z(O,OH)2 block but leaves the valence of Co essentially intact in the CoO2 block. The higher electrical conductivity of the Sr-substituted phases is explained as a consequence of increased carrier mobility. more...

Fossil fuels have been used for several decades and have resulted in increased greenhouse gases and pollutants. Currently, clean and renewable energy is in demand. Hydrogen appears to be a good candidate for clean energy because the only product of its reaction with oxygen is water. Water splitting by solar energy is a potential method for the generation of hydrogen in future applications. This study investigates the use of a CdTe quantum-dot-sensitized ZnO:N nanowire arrays for water splitting. The proposed method resulted in considerably enhanced photocurrent and stability. The electronic structures of the ZnO:N materials are also determined by O K-edge X-ray absorption spectroscopy. The incorporation of nitrogen into the ZnO nanostructure is determined by X-ray photoelectron spectroscopy and Zn K-edge X-ray absorption spectroscopy; the nitrogen incorporation changes the electronic state and, thus, increases the water-splitting performance. more...

VOx films were deposited by radio-frequency reactive magnetron sputtering from a vanadium target in an Ar–O 2 gas mixture and pure O 2 . For the films deposited in the gas mixture, the Ar flow rate was controlled at 20 sccm and the oxygen flow rate was controlled at 1, 3, and 5 sccm, respectively. A thin (~ 5 nm) Pt layer was deposited on the VOx thin films as a hydrogen catalyst. The long-range structural order, short-range atom arrangement, and gasochromic properties of the deposited films were studied. The grazing incidence X-ray diffraction (GIXRD) results indicate that the deposited films are amorphous. Lamellar structures were found at oxygen flow rates of 3 sccm and above. The X-ray absorption spectroscopy (XAS) results show that the short-range atom arrangement of the lamellar VOx thin films is similar to that of crystal V 2 O 5 . The GIXRD and XAS results show that the film obtained with the gas mixture and at an oxygen flow rate of 1 sccm did not significantly change after exposure to hydrogen, whereas the other films exhibited decreased interlayer distance, oxidation state, and crystallinity. The color of the films changed from light or deep yellow to gray. The results suggest that the gasochromic properties of the VOx thin films are related to the V 2 O 5 -like atom arrangement and the interlayer distance of the lamellar structure. The films deposited with an oxygen flow rate of 3 sccm and above can be applied to H 2 gas sensors. more...

Room-temperature confocal Raman scattering was used to probe the antiferromagnetic exchange energy J2 between the next-nearest-neighboring Ni ions in different sized NiO nanoparticles. NiO nanoparticles were synthesized using the sol–gel method and annealed at various temperatures ranging from 300 to 800 °C. The morphology and crystal structure of the prepared samples were characterized using SEM and XRD, revealing the uniformity and development of short-range crystallinity of NiO nanoparticles. This study shows that short spin correlation leads to an exponential dependency of particle size and the existence of Ni vacancies in two-magnon excitation. The Ni vacancy concentration plays an important role in lattice expansion, along with the size reduction effect. A direct comparison between short-range magnon excitation related to the Ni vacancy concentration and NiO nonstoichiometry has been made. more...

We recently reported in this journal the preparation and characterization of a nanostructured AuCu 3 alloy electrode for use as chemical sensors. This alloy electrode was prepared from a barrel-plated gold electrode (AuBPE) consisting of copper main body with successive plating of nickel and gold by manipulating the grain boundary diffusion through thermal annealing treatment and electrochemical activation in alkaline solution. In this study, based on a more detailed XRD study, we tend to explain how the nanostructured film is attained for this AuCu 3 alloy electrode. The structural characterization and electrochemical behavior of the AuCu 3 alloy were performed by XRD, EDS, and cyclic voltammetry. We further demonstrated its application as an electrochemical sensor towards non-enzymatic detection of hydrazine with good selectivity. Compared to that of AuBPE, the sensitivity for hydrazine detection using cyclic voltammetry was found to increase by ∼24.8 times with a low peak potential of ∼0.0 V vs. Ag/AgCl in neutral medium. Flow injection analysis of hydrazine shows a wide linear calibration range of 0.1 μM to 1 mM and further increases the sensitivity with a detection limit down to 0.04 μM (S/N = 3). Real sample analysis was successfully demonstrated for the detection of hydrazine in environmental water samples. more...

The effect of Mn addition on the promotion of oxygen reduction reaction (ORR) performance for PtCo/C catalysts is investigated. The structures, surface compositions, chemical compositions, local structural parameters including coordination numbers and bond distances, morphologies and electrochemical properties of prepared catalysts are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-atomic emission spectrometer (ICP-AES), extended X-ray absorption fine structure (EXAFS), high resolution transmission electron microscopy (HRTEM) and rotating disk electrode (RDE) technique, respectively. For PtCo/C catalysts modified with 0.4 and 3.2 wt% of Mn, the Pt/Co atomic ratio is 3.5 and the size is about 3.0 nm with the same face centered cubic (fcc) structure. Moreover, Mn-modified PtCo/C catalysts have the same surface composition, which is about Pt/Co/Mn of 62/32/6, and their ORR activity are both higher than that of PtCo/C and commercial Pt/C catalysts. After accelerated durability test (ADT) of 1700 cycles, Mn-2 with 3.2 wt% Mn addition still presents the best ORR mass activity, which is about 420% of commercial Pt/C. In the Mn-modified PtCo/C system, due to the existence of the neighboring Co and/or Mn oxide, there is OH repulsion between Pt–OH and these non-noble metal hydroxides or oxides, decreasing the OH coverage on Pt and increasing the number of free Pt active sites. Besides, based on the XAS analysis, the unfilled d-orbital values and extent of hybridization of Pt and Co/Mn of the PtCo and Mn-modified samples are very similar. Therefore, the promotional effect on ORR performance of Mn-2 is attributed to the most enhanced Pt-skin structure, highest Pt usage, and comparable electron transfer number during ORR instead of changes in d-orbital vacancy and alloying degree. more...

A copper ferrite generated from the sludge of printed circuit board (PCB) industry was investigated for its As(III) adsorption behavior. The adsorption of As(III) by this copper ferrite exhibited a L-shaped nonlinear isotherm and fitted well the Langmuir isotherm, implying limited binding sites and monolayer sorption occurred on the surface. The K-edge X-ray Absorption Near-Edge Structure (XANES) showed that the adsorbed As(III) could be oxidized to less toxic As(V) by copper ferrite. The maximum As adsorption capacity of the copper ferrite was 41.2 mg g −1 at pH 4.2 and decreased dramatically at higher pH (pH > 9.2) due to enhanced electrostatic repulsion between As(III) and the adsorbent surface. Desorption of As(III) using four different acid solutions demonstrated that the desorption rate decreased in the order of H 3 PO 4 > H 2 SO 4 > HCl > HNO 3 . These results demonstrate that the synthesized copper ferrite is an effective adsorbent for removing As(III) in aqueous solution. The new data obtained reveals informative knowledge for designing an arsenic removal technology in treating contaminated groundwater. more...

Here we present a comprehensive X-ray absorption spectroscopy study carried out at Co-L2,3, Co-K, O-K and Sr-K edges for the parent misfit-layered cobalt oxide phase [Sr2O2]0.52CoO2; comparison is made to another misfit-layered oxide [CoCa2O3]0.62CoO2 and the perovskite oxide LaCoO3. A high-quality sample of [Sr2O2]0.52CoO2 was obtained through ultra-high-pressure synthesis using Sr3Co2O6 and Sr(OH)2∙8H2O as starting materials. Different dosages of KClO3 were mixed with the raw materials as an oxygen source and tested, but it was found that the window for the redox control of [Sr2O2]0.52CoO2 is rather narrow. From Co-K and Co-L2,3 spectra a mixed III/IV valence state is revealed for cobalt in [Sr2O2]0.52CoO2, but the average valence value is a little lower than in [CoCa2O3]0.62CoO2. Then, Sr-K spectrum indicates that the [Sr2O2] double-layer block in [Sr2O2]0.52CoO2 clearly deviates from the cubic SrO rock-salt structure, suggesting a more complicated coordination environment for strontium. This together with a somewhat low Co-valence value and the fact that the phase formation of [Sr2O2]0.52CoO2 required the presence of Sr(OH)2∙8H2O in the high-pressure synthesis suggest that the [Sr2O2] block contains OH groups, i.e. [Sr2(O,OH)2]0.52CoO2. more...

The effect of Au and/or Ni addition on the ethanol oxidation reaction (EOR) performance in alkaline media of Pd-based binary and ternary catalysts (Pd3Au/C, Pd3Ni/C, and Pd3AuNi/C) is systematically elucidated. The EOR activities, structures, morphologies, surface compositions and surface species of the prepared catalysts are analyzed by cyclic voltammetry, X-ray diffraction and X-ray absorption spectroscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and temperature-programmed reduction, respectively. It is observed that the surface Ni with the chemical state of NiOOH can promote the EOR through bi-functional mechanism and spillover while surface Au can modify the Pd lattice and electron configuration which is helpful for the absorption of ethanol molecular. Chronoamperometric (CA) results obtained at room temperature demonstrate that the mass current density of ternary Pd3AuNi/C catalysts after the long-term EOR test for 4 h is about 1.39 and 1.10 times higher than that of the monometallic Pd/C and binary Pd3Au/C catalysts, respectively. It is proposed that the EOR stability enhancement of Pd3AuNi can be attributed to the synergistic effect of Ni and Au alloying. more...

After a decade of effort, a large number of magnetic memory nanoparticles with different sizes and core/shell compositions have been developed. While the field-cooling memory effect is often attributed to particle size and distribution effects, other magnetic coupling parameters such as inter- and intra-coupling strength, exchange bias, interfacial pinned spins, and the crystallinity of the nanoparticles also have a significant influence on magnetization properties and mechanisms. In this study, we used the analysis of static- and dynamic-magnetization measurements to investigate NiO nanoparticles with different sizes and discussed how these field-cooling strengths affect their memory properties. We conclude that the observed field-cooling memory effect from bare, small size NiO nanoparticles arises because of the unidirectional anisotropy which is mediated by the interfacial strongly pinned spins. Electronic supplementary material The online version of this article (doi:10.1186/s11671-017-1988-x) contains supplementary material, which is available to authorized users. more...

Ni doped ZnS (Zn 1− x Ni x S) nanoparticles with Ni concentration x = 0.01, 0.03 and 0.05 were synthesized by the chemical co-precipitation technique. Powder X-ray diffraction (XRD) reveals that Ni incorporates into the ZnS crystal lattice with a cubic structure. Transmission electron microscopy (TEM) measurements show that the average size of these nanoparticles is in the range 2–3 nm. Micro-Raman and photololuminescence (PL) studies also confirm the incorporation of Ni in the lattice. X-ray absorption spectroscopy (XAS) reveals that Ni replace the Zn atoms in the host lattice without forming second phases. The ZnS nanoparticles with lower Ni concentration exhibit saturated hysteresis loop at room temperature indicating ferromagnetism where as samples having higher Ni concentrations did not show such saturation confirming the intrinsic nature of the ferromagnetism at smaller doping. more...

A new fabrication strategy in which Ag plasmonics are embedded in the interface between ZnO nanorods and a conducting substrate is experimentally demonstrated using a femtosecond-laser (fs-laser)-induced plasmonic ZnO/Ag photoelectrodes. This fs-laser fabrication technique can be applied to generate patternable plasmonic nanostructures for improving their effectiveness in hydrogen generation. Plasmonic ZnO/Ag nanostructure photoelectrodes show an increase in the photocurrent of a ZnO nanorod photoelectrodes by higher than 85% at 0.5 V. Both localized surface plasmon resonance in metal nanoparticles and plasmon polaritons propagating at the metal/semiconductor interface are available for improving the capture of sunlight and collecting charge carriers. Furthermore, in-situ X-ray absorption spectroscopy is performed to monitor the plasmonic-generating electromagnetic field upon the interface between ZnO/Ag nanostructures. This can reveal induced vacancies on the conduction band of ZnO, which allow effective separation of charge carriers and improves the efficiency of hydrogen generation. Plasmon-induced effects enhance the photoresponse simultaneously, by improving optical absorbance and facilitating the separation of charge carriers. more...

The formation of μ-OO peroxide (Co-OO-Co) moieties on spinel Co

By cosubstituting [Ca(2+)-P(5+)] for [La(3+)-Si(4+)] in the Eu-doped Ca(2→8)La(8→2)(SiO4)6-x(PO4)xO2 (0 ≤ x ≤ 6) system, Eu(3+) ions are controllably and gradually transformed to Eu(2+). Thus, the emission colors consecutively changed from red to blue/green light. Furthermore, excellent warm-white lights with the low correlated color temperature (CCT) range of 3500-3800 K and a high color rendering index (Ra) (88.4-93.2) have been achieved by mixing the as-prepared phosphors at different cation cosubstitution ratios. more...

Co and N co-doped ZnO nanopowders with Co and N concentration 4, 6, and 8 mol% were synthesized by sol–gel method. Powder X-ray diffraction reveals that Co and N co-doped ZnO crystallize in wurtzite structure having space group C 6v . Photo-luminescence studies show the reduction in band gap with increase in concentration of dopants. Micro Raman studies show the red shift for 1LO phonon peak with increase in doping, generally credited to the stress caused by lattice mismatch due to N doping in ZnO. X-ray absorption spectroscopy reveals that Co replaces the Zn atoms and N replace the O atoms in the host ZnO lattice. Magnetic studies show that Co and N co-doped ZnO nanopowders exhibit ferromagnetic character at room temperature. more...

The crystal structure of Eu(2+)-activated Sr(8)ZnSc(PO(4))(7):Eu(2+) phosphor was refined and determined from XRD profiles by the Rietveld refinement method using a synchrotron light source. This phosphor crystallizes in the monoclinic structure with the I2/a space group. The SZSP:xEu(2+) phosphors showed a broad yellow emission band centered at 511 and 571 nm depending on the concentration of Eu(2+), and the composition-optimized concentration of Eu(2+) in the Sr(8)ZnSc(PO(4))(7):Eu(2+) phosphor was determined to be 2 mol %. The estimated crystal-field splitting and CIE chromaticity coordinates of Sr(8)ZnSc(PO(4))(7):xEu(2+) (x = 0.001-0.05 mol) were 20181-20983 cm(-1) and (0.3835, 0.5074) to (0.4221, 0.5012), respectively, and the emission band showed a redshift from 547 to 571 nm with increasing Eu(2+) concentration. The nonradiative transitions between the Eu(2+) ions in the Sr(8)ZnSc(PO(4))(7) host were attributable to dipole-dipole interactions, and the critical distance was approximately 19.8 Å. The combination of a 400 nm NUV chip with a blend of Sr(8)ZnSc(PO(4))(7):0.02Eu(2+) and BAM:Eu(2+) phosphors (light converters) gave high color rendering indices between 79.38 and 92.88, correlated color temperatures between 4325 and 7937 K, and tuned CIE chromaticity coordinates in the range (0.381, 0.435) to (0.294, 0.310), respectively, depending on the SZSP:0.02Eu(2+)/BAM:Eu(2+) weight ratio. These results suggest that the Sr(8)ZnSc(PO(4))(7):0.02Eu(2+)/BAM:Eu(2+) phosphor blend has potential applications in white NUV LEDs. more...

A novel fabricated copper ferrite was investigated for its As(V) removal in this study. The adsorption of As(V) by this recycled copper ferrite exhibited an L-shaped nonlinear isotherm, suggesting limited binding sites on the adsorbent surface. The As K -edge XANES indicated that the adsorbed As(V) on copper ferrite was not reduced to more toxic As(III) by Fe 2+ in the structure. The maximum As adsorption capacity of the copper ferrite was 45.66 mg g −1 at pH 3.7 and decreased with pH due to enhanced electrostatic repulsion between As(V) and the adsorbent surface. Desorption of As(V) using six different acid and salt solutions revealed that the desorption rate decreased in the order of H 3 PO 4 > Na 3 PO 4 > H 2 SO 4 > Na 2 SO 4 > HCl > HNO 3 . These results suggest that the recycled copper ferrite without surface modification is an effective adsorbent for removing As(V) from water, confirmed by effective removal of As(V) from contaminated groundwater. Furthermore, the novel fabricated copper ferrite can be used to recover rapidly in 20 s using a magnet. The information obtained in this work shows great potential for developing a cost-effective adsorbent for immobilization of arsenate using the recycled copper ferrite. more...

This investigation demonstrates an environmentally friendly inorganic light-harvesting nanostructure. This system provides a stable photoelectrochemical platform for the photolysis of water. The device is constructed by first building up an array of ZnO nanowires and then incorporating indium phosphide (InP) nanocrystals into them. A different-sized quantum dots (QDs) sensitization of the ZnO nanowire array for splitting water with a substantially enhanced photocurrent was demonstrated. InP QDs of various sizes are utilized as simultaneous sensitizers of the array of ZnO nanowires, and this multi-bandgap sensitization layer of InP QDs can harvest complementary solar light in the visible region while the ZnO nanostructures absorb the UV part of solar light. A photocurrent of 1.2 mA/cm2 at +1.0 V was observed; it was more than 108% greater than the photocurrent achieved by bare ZnO nanowires. Solar illumination measurements investigated the contribution from photoelectrochemical response and effect in unocc... more...

A space-confined synthesis method, using a mesoporous template that produces nano-sized copper (∼3.6 nm crystal size) by the thermal hydrogen reduction (THR) of spinel CuFe 2 O 4 nano-crystals, that have a high surface area ∼126 m 2 /g, (c.f. commonly cited literature values 2 /g) and a rod-like morphology, is described. In situ XRD and temperature program reduction (TPR) results showed that the generation of the copper nanoparticles occurred at 210 °C, which is lower than other reported literature values—due to the fine crystal size of the spinel CuFe 2 O 4 . The generated copper nanoparticles were also characterized by XANES, and FT-EXAFS. We have used the steam reforming of methanol (SRM) as a model reaction to demonstrate the capability of the materials formed in which a 100% conversion of methanol by steam reforming was achieved at approximately 240 °C. The proposed synthesis method combines metallurgy and THR while at the same time effectively resolving issues related to the large crystal sizes, higher calcinations temperature (above 750 °C) and low surface areas (below 10 m 2 /g), that commonly occur in conventional solid state methods. The mixed metal oxide synthesis method, using a mesoporous template, can also be applied to other heterogeneous metal oxide systems. more...

This investigation demonstrates the photocatalytic properties and activities of N-doped InTaO4 photocatalysts, which were prepared by impregnating Ni and the use of a modified Ni@NiO core–shell nanostructure-cocatalytic method for the reduction of CO2 to methanol. X-ray absorption spectroscopy (XAS) clearly indicates the oxygen vacancies and mechanism of a series of InTaO4-based photocatalysts. Nitrogen doping produces visible-light-responsive photocatalytic activity and further enhances absorbance. The cocatalytic method not only dramatically enhances absorbance, but also efficiently avoids electron–hole recombination that would otherwise be caused by electrons and holes separated from the crystal. The photocatalytic activity that was determined by the methanol yield demonstrates that N-doped samples give approximately twice the yield of undoped ones, whereas the cocatalytic method gives about triple the yield. A mechanism is aided in attempts to elucidate the correlation between structures and activities. more...

We report on the nanosized effect on superconducting properties of Bi nanoparticles (NPs) that extracted from the temperature and applied magnetic field dependent magnetization measurements of bismuth NPs, and revealed an enhanced TC and stronger coupling strength because of increased density of state and softened phonons ωln. A strong electron-phonon coupling (λep = 1.639) to low-lying phonons (ωln = 58 K) is found to be the leading mechanism behind the observed superconductivity with an enhanced TC ∼ 8.22 K and a strong superconducting coupling strength of α = 2.32(1) of 15 nm Bi NPs. Our results are well described by the Allen and Dynes formula within the framework of the McMillan formalism and are in agreement with the Ginzburg-Landau theory calculations. more...

We report here preparation and characterization of an AuCu 3 alloy electrochemical sensing platform fabricated on an easy for mass production barrel-plated gold electrode (AuBPE). Note that the AuBPE consists of Cu main body with successive plating of a very thin layer of Ni and Au (i.e., Cu–Ni–Au multilayer). By suitably manipulating the grain boundary diffusion between individual metallic layers of Cu–Ni–Au by means of thermal annealing treatment, AuCu 3 alloy film can be formed directly on the outer surface of the AuBPE. Electrochemical activation in alkaline solution can further generate a nanostructured AuCu 3 alloy film. This facile and novel approach is promising to prepare sensors for electroanalytical applications, e.g., glucose oxidation in pH-neutral solutions and simultaneous detection of uric acid, dopamine and ascorbic acid. more...

The synergistic effect of Co alloying and oxidation treatment induced progressive enhancement on oxygen reduction reaction (ORR) activities of Pd/C catalysts is studied. Based on the XPS characterization, a new term, degree of surface oxidation (DSO), is proposed to illustrate their relationship between ORR activity and surface oxidation extent. TPR characterization also provides the evolution of surface species within the topmost region. It can be obviously found the optimal temperature for the promotion of ORR activity on various oxidized samples is 520 K. On the other hand, various heat treatment atmospheres (H 2 and CO) are applied on Pd–Co system without changing their particle size. It is clearly evident that the oxidized catalysts can exhibit the superior performance relative to that of the non-oxidized ones, confirming the improved ORR activity is solely ascribed to the formation of surface PdO species with 100% DSO value rather than large particle size effect. Moreover, an explainable model is demonstrated to illustrate the promotional effect of ORR performance on the oxidized PdCo/C catalysts. more...