Synthesis of Monodispersed Pd Nanoparticles and Ultrathin Twisty Pd Nanowire Networks for Electrooxidation of Ethanol.

In recent years, preparing precious metal catalysts with a controllable morphology has become a hot research topic for researchers. In this study, monodispersed palladium (Pd) nanoparticles (NP) and ultrathin Pd twisty nanowire networks (TNN) were synthesized in a solvothermal system using N,N-dimethylformamide (DMF) and oleylamine (OAm) as solvents, Transmission electron microscopy (TEM) images reveal the successful synthesis of nanoparticles and ultrathin TNN microstructures. Electrochemical data show that the current densities of Pd-NP and Pd-TNN for the ethanol oxidation reaction (EOR) reach 1878 mA mg-1 and 1765 mA mg-1, respectively. Compared to commercial Pd/C, Pd-TNN and Pd-NP exhibit better catalytic stability, lower electron transfer barriers, and more resistance to catalyst poisoning. Temperature, pH value, and ethanol concentration are all favorable for the EOR. According to the experimental data, the mechanism of enhanced electrocatalytic activity of Pd-NP and Pd-TNN catalysts for ethanol oxidation is discussed. This paper presents a method for preparing catalysts with stabilized structures to develop Pd-based catalysts for electrocatalytic oxidation reactions.

High-Performance Room Temperature Ammonia Sensors Based on Pure Organic Molecules Featuring B-N Covalent Bond.

Exploring organic semiconductor gas sensors with high sensitivity and selectivity is crucial for the development of sensor technology. Herein, for the first time, a promising chemiresistive organic polymer P-BNT based on a novel π-conjugated triarylboron building block is reported, showcasing an excellent responsivity over 30 000 (Ra/Rg) against 40 ppm of NH3, which is ≈3300 times higher than that of its B-N organic small molecule BN-H. More importantly, a molecular induction strategy to weaken the bond dissociation energy between polymer and NH3 caused by strong acid-base interaction is further executed to optimize the response and recovery time. As a result, the BN-H/P-BNT system with rapid response and recovery times can still exhibit a high responsivity of 718, which is among the highest reported NH3 chemiresistive sensors. Supported by in situ FTIR spectroscopy and theoretical calculations, it is revealed that the N-H fractions in BN-H small molecule promoted the charge distribution on phenyl groups, which increases charge delocalization and is more conducive to gas adsorption in such molecular systems. Notably, these distinctive small molecules also promoted charge transfer and enhanced electron concentration of the P-BNT sensing polymer, thus achieving superior B-N-containing organic molecules with excellent sensing performance.

High Tribocatalytic Performance of FeOOH Nanorods for Degrading Organic Dyes and Antibiotics.

Tribocatalysis is vitally important for electrochemistry, energy conservation, and water treatment. Exploring eco-friendly and low-cost tribocatalysts with high performance is crucial for practical applications. Here, the highly efficient tribocatalytic performance of FeOOH nanorods is reported. The factors related to the tribocatalytic activity such as nanorod diameter, surface area, and surface roughness are investigated, and the diameter of the FeOOH nanorods is found to have a significant effect on their tribocatalytic performance. As a result, under ultrasonic excitation, the optimized FeOOH nanorods exhibit superior tribocatalytic degradation toward rhodamine B (RhB), acid orange 7, methylene blue, methyl orange dyes, and their mixture. The RhB and mixed dyes are effectively degraded within 20 min (k = 0.179 min-1 ) and 35 min (k = 0.089 min-1 ), respectively, with the FeOOH nanorods showing excellent reusability. Moreover, antibiotics, such as tetracycline hydrochloride, phenol, and bisphenol A are efficiently degraded. Investigation of the catalytic mechanism reveals that the friction-generated h+ as well as these yielded •OH and •O2 - active radicals participate in the catalytic reaction. This work not only shed light on the design of high-performance tribocatalyst but also demonstrates that by harvesting mechanical energy, the FeOOH nanorods are promising materials for removing organic contaminants in wastewater.

Revealing the effect of LiOH on forming a SEI using a Co magnetic "probe".

The solid-electrolyte-interphase (SEI) plays a critical role in lithium-ion batteries (LIBs) because of its important influence on electrochemical performance, such as cycle stability, coulombic efficiency, etc. Although LiOH has been recognized as a key component of the SEI, its influence on the SEI and electrochemical performance has not been well clarified due to the difficulty in precisely controlling the LiOH content and characterize the detailed interface reactions. Here, a gradual change of LiOH content is realized by different reduction schemes among Co(OH)2, CoOOH and CoO. With reduced Co nanoparticles as magnetic "probes", SEI characterization is achieved by operando magnetometry. By combining comprehensive characterization and theoretical calculations, it is verified that LiOH leads to a composition transformation from lithium ethylene di-carbonate (LEDC) to lithium ethylene mono-carbonate (LEMC) in the SEI and ultimately results in capacity decay. This work unfolds the detailed SEI reaction scenario involving LiOH, provides new insights into the influence of SEI composition, and has value for the co-development between the electrode materials and electrolyte.

Sm-Doped PIN-PMN-PT Transparent Ceramics with High Curie Temperature, Good Piezoelectricity, and Excellent Electro-Optical Properties.

Transparent piezoelectric materials are capable of coupling several physical effects such as optics, acoustics, electricity, and mechanical deformation together, which expands applications for mechanical-electro-optical multifunctional devices. However, piezoelectricity, transparency, and Curie temperature restrict each other, so it is difficult to achieve high piezoelectricity with both good transparency and a high Curie point. In this paper, Sm-doped 24Pb(In1/2Nb1/2)O3-42Pb(Mg1/3Nb2/3)O3-34PbTiO3 (PIN-PMN-PT) transparent ceramic with a high piezoelectric coefficient of 905 pC/N, excellent electro-optical coefficient of 814 pm/V, and high Curie-point of 179 °C is fabricated. Sm doping effect on the phase structures, piezoelectricity, ferroelectricity, optical transparency, electro-optical properties, and thermal stability is systematically investigated. Compared with PMN-PT transparent ceramics, PIN-PMN-PT transparent ceramics exhibit better temperature stability. Electro-optical modulation and energy conversion are achieved using PIN-PMN-PT transparent piezoelectric ceramic, which indicates that it has great potential to develop mechanical-electrical-optical multifunctional coupling devices for optical communication, energy harvesting, photoacoustic imaging, and so on.

Revealing interfacial space charge storage of Li+/Na+/K+ by operando magnetometry.

Interfacial space charge storage between ionic and electronic conductor is a promising scheme to further improve energy and power density of alkali metal ion batteries (AMIBs). However, the general behavior of space charge storage in AMIBs has been less investigated experimentally, mostly due to the complicated electrochemical behavior and lack of proper characterization techniques. Here, we use operando magnetometry to verify that in FeSe2 AMIBs, abundant Li+/Na+/K+ (M+) can be stored at M2Se phase while electrons accumulate at Fe nanoparticles, forming interfacial space charge layers. Magnetic and dynamics tests further demonstrate that with increasing ionic radius from Li+, Na+ to K+, the reaction kinetics can be hindered, resulting in limited Fe formation and reduced space charge storage capacity. This work lays solid foundation for studying the complex interfacial effect in electrochemical processes and designing advanced energy storage devices with substantial capacity and considerable power density.

In situ TEM observations of growth mechanisms of PbO nanoparticles from a Sm-doped PMN-PT matrix.

An excess PbO is usually added to raw materials to compensate for PbO volatilization during high-temperature sintering of a (1 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) piezoelectric material. However, the detailed growth mechanism of liquid phase and solid phase PbO due to excess PbO during the sintering process is still unknown. Here, the evolution behavior and growth mechanism of PbO nanoparticles from a Sm-doped 0.70PMN-0.30PT (Sm-PMN-PT) matrix were in situ observed using transmission electron microscopy with the help of electron beam irradiation. It was found that PbO nanodroplets firstly separated from the Sm-PMN-PT matrix, leading to rapid growth of newly formed PbO nanodroplets. Then, these nanodroplets coalesced into solid phase PbO nanoparticles with their size increased. After that, small solid phase nanoparticles further grew into large PbO nanoparticles by either rapidly engulfing adjacent nanodroplets and nanoparticles or slowly merging by matching these same crystal planes of adjacent nanoparticles. Finally, a heterojunction was formed between the formed large PbO nanoparticles and Sm-PMN-PT matrix. Our investigations demonstrate that the excess PbO could provide a liquid environment at the interface of Sm-PMN-PT, and the PbO nanoparticles formed act as the secondary phase at the grain boundaries of the Sm-PMN-PT matrix. This work provides a deep understanding of the role of excess PbO in the synthesis of lead-based piezoelectric materials.

Red Phosphorus/P25 Nanophotosensitizers Coated with Platelet Membrane for Enhancing Cancer Cells Photodynamic Therapy.

Photodynamic therapy (PDT), which uses targeted photosensitizing drugs, has been regarded as a promising method for cancer therapy. In the present study, photosensitizer red phosphorus modified P25 nanophotosensitizers (P25-RP) were generated, which were coated with platelet membrane (P25-RP@PLT) extracted from platelet rich plasma. The biocompatibility of P25-RP was demonstrated by cell counting kit-8 (CCK-8) and optical microscope assay, more than 93 % cells in the concentration of 100 µg/ml of P25-RP suspension after co-incubation for 24 h were still kept alive. The antitumor performance of P25-RP@PLT was evaluated via CCK-8 assay, flow cytometry and fluorescence staining of live/dead cells. The experiment results showed that P25-RP@PLT could ablate 55 % malignant tumor cells upon laser irradiation within 5 min, which was 10 % higher than P25-RP alone against cancer cells. Mechanistically, the cancer cell toxicity of P25-RP@PLT nanophotosensitizers was attributed to its heterojunction structure that broadens the absorption spectra, whereas PLT membrane coating technology allows for immune escape and selective adhesion capacity to cancer cells. This work provided a novel pathway on the design of novel visible-light-driven photosensitizer for cancer therapy.

Reacquainting the Electrochemical Conversion Mechanism of FeS2 Sodium-Ion Batteries by Operando Magnetometry.

In spite of the excellent electrochemical performance in lithium-ion batteries (LIBs), transition-metal compounds usually show inferior capacity and cyclability in sodium-ion batteries (SIBs), implying different reaction schemes between these two types of systems. Herein, coupling operando magnetometry with electrochemical measurement, we peformed a comprehensive investigation on the intrinsic relationship between the ion-embedding mechanisms and the electrochemical properties of the typical FeS2/Na (Li) cells. Operando magnetometry together with ex-situ transmission electron microscopy (TEM) measurement reveal that only part of FeS2 is involved in the conversion reaction process, while the unreactive parts form "inactive cores" that lead to the low capacity. Through quantification with Langevin fitting, we further show that the size of the iron grains produced by the conversion reaction are much smaller in SIBs than that in LIBs, which may lead to more serious pulverization, thereby resulting in worse cycle performance. The underlying reason for the above two above phenomena in SIBs is the sluggish kinetics caused by the larger Na-ion radius. Our work paves a new way for the investigation of novel SIB materials with high capacity and long durability.

Operando Magnetometry Probing the Charge Storage Mechanism of CoO Lithium-Ion Batteries.

Cobalt oxide (CoO) is a promising electrode for high-energy-density Li-ion batteries (LIBs), where the charge storage is believed to take place solely during the electrochemical oxidation/reduction processes. However, this simple picture has been increasingly challenged by reported anomalously large storage capacities, indicating the existence of undiscovered extra charge reservoirs inside the system. Here, an advanced operando magnetometry technology is employed to monitor the magnetization variation of the CoO LIBs in real time and, in this particular system, it is clearly demonstrated that the anomalous capacity is associated with both the reversible formation of a spin capacitor and the growth of a polymeric film at low voltages. Furthermore, operando magnetometry provides direct evidence of the catalytic role of metallic Co in assisting the polymeric film formation. These critical findings help pave the way for better understanding of the charge storage mechanisms of transition-metal oxides and further utilizing them to design novel electrode materials.

Assembly of Bimetallic PdAg Nanosheets and Their Enhanced Electrocatalytic Activity toward Ethanol Oxidation.

The direct ethanol fuel cells in an alkaline medium have a broad vision of applications because of their large energy density, reasonable power density, and environmentally friendly features. Herein, we present a facile one-step method to synthesize PdAg nanosheet assemblies (NSAs) in a mixed solution of N,N-dimethylformamide and water with the addition of molybdenum hexacarbonyl and cetyltrimethylammonium bromide. Pure Pd NSA shows an irregular shape while PdAg NSAs gradually undergo a process from solid assembly to a hollow structure with the Pd/Ag molar ratio changing from 3:1 to 2:1 to 1:1. The formation of alloy nanosheets in the assemblies combined with the introduction of Ag in the Pd catalyst enhances the catalytic activity toward ethanol electrooxidation from 1524 mA mg-1 of pure Pd NSA to 1866 mA mg-1 of PdAg NSA with a Pd/Ag molar ratio of 2:1. On the basis of the experimental data, compared with pure Pd structures, both the nature of a thin nanosheet of PdAg NSAs and the structural changes in the alloy assemblies play key roles in determining the electrocatalytic activity of these Pd-based catalysts.

Electron diffraction study of the space group of Bi5Ti3FeO15 multiferroic ceramic.

Bi5Ti3FeO15 (pentabismuth trititanium iron pentadecaoxide), which is a multiferroic four-layer Aurivillius phase compound, has received much attention in recent years. However, three mutually inconsistent orthorhombic space groups, i.e. A21am, Fmm2 and Pnn2, have been reported for the room-temperature phase of Bi5Ti3FeO15 by X-ray and neutron diffraction investigations. Here, electron diffraction results are presented and discussed for the first time to unambiguously clarify the room-temperature space group of ceramic Bi5Ti3FeO15. It has been found that all the observed reflections from the ceramic agree with those expected in A21am, while the observed reflections 011, 013 and 015 should be forbidden in the case of Fmm2, and no 107 and 109 reflections were observed although allowed for Pnn2. The present study has demonstrated that the space group of Bi5Ti3FeO15 ceramic is A21am rather than Fmm2 or Pnn2, an identification that proved to be a challenge for X-ray diffraction. On the basis of the space group A21am, the lattice parameters of the Bi5Ti3FeO15 ceramic were calculated from its X-ray diffraction data.

Reversible control of magnetization in Fe3O4 nanoparticles by a supercapacitor.

The manipulation of magnetism by electrical means is one of the most intensely pursued research topics of recent times aiming at the development of efficient and low-energy consumption devices in spintronics, microelectronics and bioelectronics. Herein, we successfully tuned the saturated magnetization of Fe3O4 by a supercapacitor. Through increasing the surface area of magnetic particles and activation of carbon cloth, fully reversible and robust saturation magnetization variation with low power consumption and remarkable switching speed can be realized on Fe3O4/ionic liquid interfaces at room temperature. The associated magnetism modulation can be attributed to ionic transition between Fe2+ and Fe3+ resulting from both electrostatic and electrochemical doping. This work paves the way for the development of high-performance spintronic devices.

Enhanced piezo-photocatalytic performance by piezoelectric and visible light photoexcitation coupling through piezoelectric Na0.5Bi0.5TiO3 micron crystals.

The unique piezoelectric potential of piezoelectrics could lead to performance gains for electrochemical catalysis. Here, a cuboid-like Na0.5Bi0.5TiO3 (NBTO) piezoelectric micron crystal was synthesized by a hydrothermal process. The piezocatalytic and visible light assisted piezo-photocatalytic activities of NBTO were investigated. Surprisingly, under ultrasonic vibration and visible light irradiation, the NBTO exhibited four times faster degradation rate than that under ultrasonic vibration only, although the NBTO doesn't absorb visible light. An efficient coupling between piezoelectric effect and visible light photoexcitation in NBTO was directly demonstrated. The improved piezo-photocatalytic performance is attributed to the piezoelectric potential and the decrease of bandgap of NBTO micron crystal due to strain induced by ultrasonic vibration. A new fundamental mechanism for the improved degradation of organic dye has been proposed for piezoelectric and photoexcitation coupling. This work extends the application of wide band gap piezoelectric materials in the visible light area.

Hydrothermal Synthesis of Single-Crystalline Bi2Fe4O9 Photocatalyst with Enhanced Visible-Light Photocatalytic Activity.

Submicron Bi2Fe4O9 crystals were successfully synthesized by a one-step hydrothermal synthesis method and employed effectively as a visible-light-driven photocatalyst for the degradation of methylene blue dye. Scanning electron microscopy and transmission electron microscopy observations revealed that the as-prepared sample consisted mainly of submicron plates and a small quantity of submicron particles. The ultraviolet-visible absorption spectrum of the submicron Bi2Fe4O9 crystals shows two broad absorption edges in the visible region with band gaps of 1.57 and 2.15 eV, respectively. The photodegradation rate of Bi2Fe4O9 is more than twice that of TiO2 for the degradation of methylene blue under visible-light irradiation, demonstrating the excellent photocatalytic activity of these submicron Bi2Fe4O9 crystals. The acquired photocurrent densities are 43.3 and 46.6 µA/cm² for visible-light and ultraviolet-visible irradiation, respectively. These results demonstrate that the submicron Bi2Fe4O9 crystals are potential visible-light photocatalysts for use in environmental purification and solar energy utilization.

Electrospun γ-Fe2O3 nanofibers as bioelectrochemical sensors for simultaneous determination of small biomolecules.

Nanofibers of α-Fe2O3 and γ-Fe2O3 have been obtained after the controlled calcination of precursor nanofibers synthesized by electrospinning. α-Fe2O3 nanofibers showed an irregular toruloid structure due to the decomposition of poly (4-vinyl) pyridine in air while γ-Fe2O3 nanoparticles decorated nanofibers were observed after the calcination under N2 atmosphere. Electrochemical measurements showed that different electrochemical behaviors were observed on the glassy carbon electrodes modified by α-Fe2O3 and γ-Fe2O3 nanofibers. The electrode modified by γ-Fe2O3 nanofibers exhibited high electrocatalytic activities toward oxidation of dopamine, uric acid and ascorbic acid while α-Fe2O3 nanofibers cannot. Furthermore, the γ-Fe2O3 modified electrode can realize the selective detection of biomolecules in ternary electrolyte solutions. The synthesis of nanofibers of α-Fe2O3 and γ-Fe2O3 and their electrochemical sensing properties relationship have been discussed and analyzed based on the experimental results.

Structural Regulation of PdCu2 Nanoparticles and Their Electrocatalytic Performance for Ethanol Oxidation.

Two types of PdCu2 nanoparticles were prepared through one-pot synthesis and a two-step reducing process, named as PdCu2-1 and PdCu2-2, respectively. The morphology and structure of as-prepared samples were investigated by transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and inductively coupled plasma-optical emission spectrometry. Results showed that more Pd atoms were buried in the inside of PdCu2-1, whereas more available Pd sites were distributed on the surface of PdCu2-2. The electrochemical measurements indicated that both PdCu2-1 and PdCu2-2 nanoparticles showed a higher electrocatalytic activity than that for pure Pd nanoparticles. In particular, PdCu2-2 predictably exhibited a better stability and durability as well as a lower onset potential and a higher catalytic current density than that of PdCu2-1 toward ethanol oxidation in alkaline media. On the basis of these studies, the formation mechanisms of both the PdCu2 catalysts and the relationship between their structure and properties were discussed in this paper.

Novel rod-shaped magnetotactic bacteria belonging to the class Alphaproteobacteria.

Novel large, rod-shaped magnetotactic bacteria (MTB) were discovered in intertidal sediments of the Yellow Sea, China. They biomineralized more than 300 rectangular magnetite magnetosomes per cell. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that they are affiliated with the Alphaproteobacteria and may represent a new genus of MTB.

Hydrothermal synthesis and optical properties of single-crystalline Bi3.15Nd0.85Ti3O12 nanoplates of layered-perovskite structure.

Single-crystalline Bi3.15Nd0.85Ti3O12 (BNdT) nanoplates of bismuth-layered perovskite structure have been synthesized through hydrothermal process. The BNdT nanoplates possess well-defined tetragonal shapes with landscape dimension of 100-600 nm and thickness of 10-30 nm. The in-plane surfaces of tetragonal-shaped nanoplates lies on (001), and the side surfaces are (110) and (110). The BNdT nanoplates were formed due to the rather higher growth rate of a-b plane than that of c-axis. The optical absorption characteristics in UV-visible region demonstrated that the band gap of the BNdT nanoplates is 3.33 eV. The absorption bands around 516 nm, 526 nm, 585.6 nm, 684.6 nm and 750 nm should be assigned as transitions of Nd3+ from the ground state 4I9/2 to 2G9/2, 4G7/2, 2G7/2 or 4G5/2, 4F9/2 and 4S3/2 states, respectively.