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Compared with single-molecule TADF emitters, exciplexes can simplify the complicated molecule design and synthesis and have the superiority of conveniently realizing spectra with a bathochromic shift via mixing donor and acceptor components.

The sluggish oxygen reaction kinetics concomitant with the high overpotentials and parasitic reactions from cathodes and solvents is the major challenge in aprotic lithium-oxygen (Li-O2 ) batteries. Herein, PtIr multipods with a low Lewis acidity of the Pt atoms are reported as an advanced cathode for improving overpotentials and stabilities. DFT calculations disclose that electrons have a strong disposition to transfer from Ir to Pt, since Pt has a higher electronegativity than Ir, resulting in a lower Lewis acidity of the Pt atoms than that on the pure Pt surface. The low Lewis acidity of Pt atoms on the PtIr surface entails a high electron density and a down-shifting of the d-band center, thereby weakening the binding energy towards intermediates (LiO2 ), which is the key in achieving low oxygen-reduction-reaction (ORR) and oxygen-evolution-reaction (OER) overpotentials. The Li-O2 cell based on PtIr electrodes exhibits a very low overall discharge/charge overpotential (0.44 V) and an excellent cycle life (180 cycles), outperforming the bulk of reported noble-metal-based cathodes.

The main challenge for lithium-oxygen (Li-O2) batteries is their sluggish oxygen evolution reaction (OER) kinetics and high charge overpotentials caused by the poorly conductive discharge products of lithium peroxide (Li2O2). In this contribution, the cesium lead bromide perovskite (CsPbBr3) nanocrystals were first employed as a high-performance cathode for Li-O2 batteries. The battery with a CsPbBr3 cathode can exhibit the lowest charge overpotential of 0.5 V and the best cycling performance of 400 cycles among all the reported perovskite-based Li-O2 cells, which represents a new benchmark. Most importantly, the density functional theory (DFT) calculations further prove that the rate limitation step during OER processes is the decomposition of LiO2 to form O2 and Li+, and the weak adsorption strength between CsPbBr3 surfaces and LiO2 results in a low charge overpotential for the CsPbBr3-based Li-O2 battery. This work first demonstrates the good potential of CsPbBr3 for application in metal-air batteries.

High-entropy alloys (HEAs) are attracting intensive attention due to their broad compositional tunability and interesting catalytic properties. However, precisely shaping the HEAs into suprathin low-dimensional nanostructures for achieving diverse applications remains an enormous challenge owing to their intrinsic thermodynamic instability. Herein we propose a new and general low-temperature method for incorporating up to eight metallic elements into one single-phase subnanometer ribbon to achieve the thinnest HEA metal materials in the world. We experimentally demonstrate that synthetic processes for suprathin HEA subnanometer ribbons (SNRs) include (1) different metal atom nucleation via galvanic exchange reaction between different metal precursors and Ag nanowire template, (2) co-reduction of different metal precursors on nanowire template, and (3) the removal of the inner Ag core. Density functional theory (DFT) calculations reveal that the crystallization and stabilization of HEA SNRs strongly depend on the "highly dynamic" Ag from the template, and the crystallization levels of HEA subnanometer ribbons are closely correlated with the concentration of Pt and Pd. We demonstrate that the present synthetic method enables the flexible control of components and concentrations in HEAs SNRs for achieving a library of HEA SNRs and also superior electrocatalytic properties. The well-designed HEA SNRs show great improvement in catalyzing the oxygen reduction reaction of fuel cells and also high discharge capacity, low charge overpotential, and excellent durability for Li-O

Cryogenic electron tomography (cryoET) allows visualization of cellular structures in situ. However, anisotropic resolution arising from the intrinsic “missing-wedge” problem has presented major challenges in visualization and interpretation of tomograms. Here, we have developed IsoNet, a deep learning-based software package that iteratively reconstructs the missing-wedge information and increases signal-to-noise ratio, using the knowledge learned from raw tomograms. Without the need for sub-tomogram averaging, IsoNet generates tomograms with significantly reduced resolution anisotropy. Applications of IsoNet to three representative types of cryoET data demonstrate greatly improved structural interpretability: resolving lattice defects in immature HIV particles, establishing architecture of the paraflagellar rod in Eukaryotic flagella, and identifying heptagon-containing clathrin cages inside a neuronal synapse of cultured cells. Therefore, by overcoming two fundamental limitations of cryoET, IsoNet enables functional interpretation of cellular tomograms without sub-tomogram averaging. Its application to high-resolution cellular tomograms should also help identify differently oriented complexes of the same kind for sub-tomogram averaging.

The electrosynthesis of high-value-added multicarbon compounds coupled with hydrogen production is an efficient way to achieve carbon neutrality; however, the lack of effective bifunctional catalysts in electrosynthesis largely hinders its development. Herein, we report the first example on the highly efficient electrosynthesis of high-value-added 1,1-diethoxyethane (DEE) at the anode and high-purity hydrogen at the cathode using 1 nm PtIr nanowires (NWs) as the bifunctional catalysts. We demonstrate that the cell using 1 nm PtIr nanowires as the bifunctional catalysts can achieve a reported lowest voltage of 0.61 V to reach the current density of 10 mA cm-2, much lower than those of the Pt NWs (0.85 V) and commercial Pt/C (0.86 V), and also can have the highest Faraday efficiencies of 85% for DEE production and 94.0% for hydrogen evolution in all the reported electrosynthesis catalysts. The in situ infrared spectroscopy study reveals that PtIr NWs can facilitate the activation of O-H and C-H bonds in ethanol, which is important for the formation of acetaldehyde intermediate, and finally DEE. In addition, the cell using PtIr NWs as bifunctional catalysts exhibits excellent stability by showing almost no obvious decrease in the Faraday efficiency of the DEE production.

Structure and defect control are widely accepted effective strategies to manipulate the activity and stability of catalysts. On a freestanding hierarchically porous carbon microstructure, the tuning of oxygen vacancy in the embedded hollow cobaltosic oxide (Co3 O4 ) nanoparticles is demonstrated through the regulation of nanoscale Kirkendall effect. Starting with the embedded cobalt nanoparticles, the concentration of oxygen-vacancy defect can vary with the degree of Kirkendall oxidation, thus regulating the number of active sites and the catalytic performances. The optimized freestanding catalyst shows among the smallest reversible oxygen overpotential of 0.74 V for catalyzing oxygen reduction/evolution reactions in 0.1 m KOH. Moreover, the catalyst shows promise for substitution of noble metals to boost cathodic oxygen reactions in portable zinc-air batteries. This work provides a strategy to explore catalysts with controllable vacancy defects and desired nano-/microstructures.

Core/shell nanocatalysts are a class of promising materials, which achieve the enhanced catalytic activities through the synergy between ligand effect and strain effect. However, it has been challenging to disentangle the contributions from the two effects, which hinders the rational design of superior core/shell nanocatalysts. Herein, we report precise synthesis of PdCu/Ir core/shell nanocrystals, which can significantly boost oxygen evolution reaction (OER) via the exclusive strain effect. The heteroepitaxial coating of four Ir atomic layers onto PdCu nanoparticle gives a relatively thick Ir shell eliminating the ligand effect, but creates a compressive strain of ca. 3.60%. The strained PdCu/Ir catalysts can deliver a low OER overpotential and a high mass activity. Density functional theory (DFT) calculations reveal that the compressive strain in Ir shell downshifts the d-band center and weakens the binding of the intermediates, causing the enhanced OER activity. The compressive strain also boosts hydrogen evolution reaction (HER) activity and the strained nanocrystals can be served as excellent catalysts for both anode and cathode in overall water-splitting electrocatalysis.

Visualization of the chemical structures of two-dimensional (2D) materials and their interfaces at the virtually atomic scale is an imperative step toward devising highly efficient ultrathin optoelectronic devices. Herein, we demonstrate a universal method featuring time-of-flight secondary ion mass spectrometry (ToF-SIMS), coupled with the structure simplicity of 2D materials, as a versatile tool to reveal the vertical atomic layers of various two-dimensional (2D) materials including graphene, hexagonal boron nitride (h-BN), and transition metal dichalcogenides (TMDs). We demonstrated that the vertical atomic layers of those 2D materials can be unveiled layer-by-layer using a strategy of ToF-SIMS three-dimensional (3D) analysis developed in this work. Moreover, we found that the extreme surface sensitivity and chemical specificity of ToF-SIMS also enables the examination of the lateral uniformity of 2D materials. During this process, we first removed interference of adsorbed organic contamination by anne...

High efficiency platinum-based catalyst demands the ultrafine size and well dispersion of Pt nanoparticles (NPs), with clean surface and strong interactions between the supports. In this work, we demonstrate a simple strategy for the preparation of ultra-dispersed surface-clean Pt catalyst with high stability, in which the Pt nanoparticles (NPs) with 1.8 ± 0.6 nm in size are anchored tightly on a 3D hierarchical porous graphitized carbon (3D-HPG) through galvanic replacement reaction. The as-obtained catalyst can undergo 2000 voltage cycles with negligible activity decay and no apparent structure and size changes for MOR during the durability test, and its mass activity for ORR only reduce 18.3% after 5000 cycles. The excellent performance is attributed to strong anchoring effect between carbon support and Pt nanoparticles.

One-dimensional (1D) Pt-based nanotubes (NTs) are widely studied as a promising class of ORR electrocatalysts. A rational porosity for wall of nanotubes could lead to higher atomic utilization and better mass transportation. To confirm this speculation, we prepare a novel class of PdPt porous nanotubes with sub-nano Pt-shell. Their ESCA of 95 m2 g−1 and mass activity of 2.29 A mgPt−1 are distinctly greater than that of the Pt nanotubes with perfect wall (91.45 m2 g−1 and 2.09 A mgPt−1), and are 14.3 and 9.6 times higher than those of commercial benchmark Pt/C catalyst, respectively. The prolonged electrocatalytic durability is also shown. The improved performance can be ascribed to a combination of alloying and unique geometry (one dimension and nanotubes with porous walls).

Ultrathin nanosheet catalysts deliver great potential in catalyzing the oxygen reduction reaction (ORR), but encounter the ceiling of the surface atomic utilizations, thus presenting a challenge associated with further boosting catalytic activity. Herein, a kind of PdPtCu ultrathin nanorings with increased numbers of electrocatalytically active sites is reported, with the purpose of breaking the activity ceiling of conventional catalysts. The as-made PdPtCu nanorings possess abundant high-index facets at the edge of both the exterior and interior surfaces. An ultrahigh electrochemical active surface area of 92.2 m

The interaction between graphene and different metal substrates is important for preparation of graphene with large area and high quality. The existence of graphene-metal interaction can also alter the electronic properties of graphene. In this study, experiments using time-of-flight secondary ion mass spectrometry (ToF-SIMS) were conducted at 450 °C to investigate the interaction between graphene and Cu foil substrate. In the ToF-SIMS spectra, in addition to graphene and Cu-related peaks, we also found the peaks originated from the interaction between graphene and Cu foil substrate. The distribution of the graphene-related ions and the ions related to the graphene-Cu interaction shows a similar pattern in the ToF-SIMS images; however, the distribution of the ions related to the graphene and the Cu oxide exhibits a complementary pattern, revealing that a graphene-covered Cu surface shows an improved oxidation resistance during annealing processes and storage. This work provides direct and strong evidence showing the interaction between graphene and Cu foil substrate.

Clean surface of graphene was obtained at 500 °C and characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). In the XPS C1s spectrum of graphene, besides an asymmetric sp2 carbon peak and a π-π∗ shake-up peak appeared, an additional sp3 carbon peak representing sp3 defects was also present. In the ToF-SIMS positive ion spectrum of graphene, a series of CxH2+ ions originated from the defects of graphene was found. To determine the origin of the CxH2+ ions, defects were created on the surface of nearly defect-free highly oriented pyrolytic graphite (HOPG) by bombarding it with a Cs+ ion beam at various sputtering doses. A detailed examination of the positive ion spectra of ion-bombarded HOPG surfaces reveals the presence of the CxH2+ ions, confirming that these CxH2+ ions, which came from the defects created on the sputtered HOPG surfaces, are similar to the defects present on graphene surface. A sp3 carbon peak at 285.3 eV, representing sp3 defects appeared in the XPS spectra of sputtered HOPG samples, confirms that the surface of the sputtered HOPG is similar to that of graphene. Fragmentation mechanisms of selected ions in the ToF-SIMS spectra of graphene and HOPG were proposed.

The exploration of new materials for modifying electrodes is important to advance electrochemical biosensors. Herein, we demonstrated that amorphous bimetallic boride material (Co–2Ni–B) prepared by a simple and facile aqueous reaction is an efficient matrix to immobilize acetylcholinesterase (AChE) to construct a biosensor for the determination of organophosphate pesticides. The effects of different composition and crystallinity on its electrochemical performance are investigated, and the optimization studies of the biological transducer were also discussed. Under optimal conditions, the fabricated sensor showed good analytical performance for the determination of chlorpyrifos with a low limit of detection (2.83 pM) and a wide linear range (3 pM–300 nM). The proposed biosensor also demonstrated high reproducibility, stability and accuracy. The impressive performance was due to the excellent conductivity and the unique amorphous bimetal–metalloid complex nanostructure. These results introduce a new class of promising materials as a robust platform for biosensor applications.

Polyethylene glycol (PEG) was used as a catalyst to enhance chalcopyrite bioleaching with Acidithiobacillus ferrooxidans in shake flasks. The effects of PEG on the sulfur oxidation of A. ferrooxidans and on the process of chalcopyrite bioleaching were investigated. The morphology, main components and sulfur speciation of bioleached chalcopyrite surfaces were evaluated combining with XRD, SEM and XPS. It was demonstrated that addition of PEG could significantly improve the bioleaching of chalcopyrite. Furthermore, the results indicated that elemental sulfur and jarosite were the main components of the passivation layer during the bioleaching of chalcopyrite. PEG could promote the sulfur oxidation by A. ferrooxidans due to an increase in bacterial attachment, and therefore accelerate the biooxidation of elemental sulfur generated in leaching process. It was found that PEG eliminated inhibitory elemental sulfur from the chalcopyrite surface which could be the main reason for enhanced the leaching efficiency.

Polydimethylsiloxane (PDMS)-grafted nanoparticles and PDMS were added, respectively, to inhibit the dewetting of polymer films and the formation of surface patterns in spin coating. Uniform and flat films were successfully achieved with the addition of PDMS-grafted silica nanoparticles or PDMS. Time-of-flight secondary ion mass spectrometry depth profiling indicated that PDMS-grafted silica nanoparticles and PDMS preferentially segregated to the surface. A high concentration of bromine end groups was observed at the interface. The surface layer of PDMS or PDMS-grafted silica nanoparticles can decrease the surface tension of the polymer solutions and reduce the evaporation rates of the solvents, providing more time for the bromine end groups to anchor themselves at the silicon substrates. Copyright © 2016 John Wiley & Sons, Ltd.

This report describes a reversible colourimetric and on–off–on module of fluorescent chemosensor for selective cascade recognition of Cu2+ and with unique output optical response in aqueous solution. On the other hand, F−, Cl−, Br−, I−, CH3COO−, HSO4−, ClO4−, CN− and SCN− did not induce significant changes in fluorescence. Moreover, the colour change in chemosensor LH by response of this colourimetric chemosensor can be visualised by naked eye. These fluctuations in spectral response, under electronic behaviour, can be viewed to mimic as IMPLICATION logic gate.

Hydrogenated graphite powder was obtained through Birch reduction of graphite powder and characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) at 500 °C. The sp3 carbons formed at the edges of the surface of the hydrogenated graphite powder exhibited an sp3 carbon peak in the XPS C1s spectrum. The sp3-to-sp2 carbon ratio calculated from the XPS spectra increased from 0.08 to 1.19 after hydrogenation. Two sets of peaks, the Cx− and CxH− ion series (where x = 1, 2, 3…), were identified in the ToF-SIMS spectra of both the graphite powder and hydrogenated graphite powder. The difference between these two spectra represented an increase in the normalized intensities of the H− and CxH− ions in the spectrum of the hydrogenated graphite powder, indicating the formation of more sp3 carbons on the surface.

Carbon nanotubes (CNTs) are synthesized through a novel low cost self-vaporized chemical vapor deposition (SCVD) technique from an indecomposable solid carbon source for the first time. This method was manipulated to avoid the injection of flammable gasses, by producing gaseous carbon (e.g. CO) through an in situ catalyzed gasification of the intermediate product induced by KOH. Simultaneously, the as-produced gaseous carbons will deposit onto the pre-imbedded Ni nanocatalyst surface and form CNTs. The growth mechanism is discussed in detail by adjusting the KOH amount. The as-prepared CNTs are rich in oxygen and deficiencies, which endow them with abundant active sites for electrochemical applications. Superior supercapacitor performance is achieved with a specific capacitance 6 times higher than that of commercial CNTs. This technique represents a novel, convenient approach toward large scale production of CNTs directly from a solid carbon precursor, and would show promising applications in various industrial fields.

The cleanliness of the surface of graphene is important for its proper functioning in devices and sensors. Impurities including residual poly(methyl methacrylate) (PMMA) and hydrocarbon contaminants can alter its electronic and chemical properties. In this study, we used two surface-sensitive techniques, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), to monitor the chemical composition of the surface of graphene after washing it with acetone and annealing at high temperatures. The concentration of residual PMMA and hydrocarbon contaminants decreased as the annealing temperature increased. The atomic ratio of sp3 carbons to sp2 carbons of a clean graphene surface determined using XPS can be used to estimate the amounts of sp3 defects in graphene. ToF-SIMS spectra indicate that residual PMMA was removed from the surface of graphene at 400 °C, while hydrocarbon contaminants required a higher temperature of 500 °C to remove. In ToF-SIMS spectra obtained at 500 °C, the characteristic ions for graphene, which are related to cleavage of ring structure, include Cx+ (x = 1, 2, 3…), CxH+ and CxH2+ as well as Cx− and CxH−. For the first time, we developed a process to produce a very clean graphene surface which was verified by ToF-SIMS and XPS analyses.

In the carbon dioxide (CO2) enhanced oil recovery (EOR) process and subsequent geological CO2 sequestration, a ternary system consisting of CO2, crude oil, and brine exists in the reservoir due to the common practice of injecting CO2 together with brine. In this paper, we carried out molecular dynamics simulations to study the interfacial properties of the ternary CO2, hexane, and 1.52 mol/L sodium chloride (NaCl) solution system under 330 K and 20 MPa with different CO2 compositions at the supercritical state, which are very important for the efficiency of the EOR and CO2 sequestration processes. We observed that CO2 mixes well with hexane and a clear interface separates the CO2–hexane mixture with the NaCl solution. The interfacial roughness increases with the CO2 composition, indicating deeper molecular penetrations and shorter capillary wavelengths, which leads to the reduced interfacial tension. Interestingly, the surface excess of CO2 reaches maximum at a CO2 molar fraction of 62.5% (or a weight fra...

We have established a simple and effective biosensing platform based on the non-covalent assembly of biodegradable single-layer MnO2 nanosheets and target-specific oligonucleotide sequences, and demonstrated its application for sensitive and selective sensing of intracellular microRNA in living cells.

The synthesis of ultrathin single-crystal 1D (one dimensional) nanostructures is highly desirable for potential applications as nanoconnectors and nanoscale devices. In this work, we demonstrate the preparation of straight single-crystalline coaxial silver nanocables (13 nm core diameter, 1.5 nm sheath thickness) in large amounts with excellent dispersibility for the first time through a self assembly approach via insulin fibril templates. This outstanding method for obtaining silver nanocables with ultrathin diameters will be attractive for the fabrication of other metallic 1D nanostructures, and this study may offer an effective strategy to design a novel silver nanostructure with diverse functionalities and potential applications in conductive materials, sensors and catalysts.

In this study, a series of suspensions were fabricated by dispersing calcium carbonate (CaCO3), cement and silica fume into a polycarboxylate-ether plasticizer (PCE)/water solution. The PCE used was a comb-like copolymer containing a sodium polymethacrylate (PMA) backbone partially esterified with polyethyleneglycol (PEG) side chains. Sedimentation and optical microscopy tests indicated that both CaCO3 and cement could form homogeneous suspensions. The crystallization behavior of the PEG side chains revealed that PEG had stronger interactions with CaCO3 than with cement and silica fume particles, which was further confirmed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). A detailed time-of-flight secondary ion mass spectrometry (ToF-SIMS) examination suggested that PEG was mainly located on the surfaces of the CaCO3, and the PMA backbones were mainly located on the surfaces of the cement and silica fume, respectively. The different interactions between copolymer and inorganic particles were associated with their interfacial tensions, and had a remarkable influence on the paste fluidity.

Stable and unstable spin-coated polymer films were prepared using various solvents and substrates. The relationship between polymer end-group concentrations and stability of spin-coated polymer films was revealed by time-of-flight secondary ion mass spectrometry depth profiling. A high concentration of bromine end groups at the interface between the polymer and the substrate helped to prevent the dewetting of films. In contrast, the bromine end groups were found to be more evenly distributed in unstable thin films. The extent to which the bromine end groups segregate to the interface depended on the competitive interactions between the polymer, the solvent and the substrate. Stronger polymer–solvent and solvent–substrate interactions prevented the segregation of the bromine end groups to the interface, resulting in unstable polymer films. Copyright © 2013 John Wiley & Sons, Ltd.

The effects of argon (Ar) and a mixture of Ar and oxgyen(Ar/O2) plasmas on amorphous and semi-crystalline poly(bisphenol A hexane ether) thin films were investigated by time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and principal component analysis (PCA). PCA results of the ToF-SIMS spectra indicate that an Ar/O2 plasma produced less physical sputtering and had a higher chemical reactivity than did an Ar plasma, regardless of whether an amorphous or a crystalline surface was involved. However, the chemical differences between the Ar- and Ar/O2-plasma-treated semi-crystalline films were much smaller. The observed results can be explained by the higher resistance of the polymer crystalline regions to physical sputtering and chemical etching. Copyright © 2013 John Wiley & Sons, Ltd.

The scope of hydrogel applications can be greatly expanded by the improvement of mechanical properties. However, enhancement of nanocomposite hydrogels (NC gels) has been severely limited because the size of crosslinking nanoparticles is too large, at least in one dimension. Here we report a new strategy to synthesize non-aggregated spherulite nanoparticles, with diameters, Hydrogels containing nanoparticles have enhanced mechanical properties that can be limited if the size of the crosslinking nanoparticles is too large. Here, Zhang and others have produced non-aggregated spherulite nanoparticles with diameters of less than 5 nm and investigated their effect on hydrogels.

The thermal properties of the fluorocarbon–hydrocarbon copolymer [-(CF2)8-(CH2)10-]N were characterized using polarized optical microscopy, differential scanning calorimetry and X-ray diffraction. The results revealed the presence of a crystalline phase and a threaded nematic liquid crystal phase. The changes in the surface composition during annealing were studied in situ using time-of-flight secondary ion mass spectrometry. The spectra were interpreted using principal component analysis (PCA). The surface compositions at different thermal states can be distinguished by PCA. Moreover, a PCA loadings analysis revealed a continuous increase in the concentration of the hydrocarbon segments on the surface as the polymer gradually changed from the amorphous state to the liquid crystal state and finally the crystalline state. This suggests that the chemical composition of the surface in the amorphous state is controlled by the surface energy difference between the fluorocarbon and hydrocarbon segments, while the surface composition in the crystalline state is controlled by the structural ordering of the fluorocarbon segments. The results also showed that the surface re-construction of this polymer was highly reversible. Copyright © 2012 John Wiley & Sons, Ltd.

This report provides detailed experimental results of thermal and surface characterization on untreated and surface-treated halloysite nanotubes (HNTs) obtained from two geographic areas. Surface characterization techniques, including XPS and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used. ToF-SIMS surface analysis experiments were performed with both atomic and cluster ion beams. Higher ion yields and more high-mass ions were obtained with the cluster ion beams. Static ToF-SIMS spectra were analyzed with principal component analysis (PCA). Morphological diversities were observed in the samples although they mainly contained tubular structures. Thermogravimetric data indicated that aqueous hydrogen peroxide solution could remove inorganic salt impurities, such as alkali metal salts. The amount of grafting of benzalkonium chloride of HNT surface was determined by thermogravimetic analysis. PCA of ToF-SIMS spectra could distinguish the samples minedfrom different geographical locations as well as among surface-treatedand untreatedsamples. Copyright c � 2010 John Wiley & Sons, Ltd.

The synthesis of Pt nanotubes catalysts remains a substantial challenge, especially for those with both sub-nanometer wall thickness and micrometer-scale length characteristics. Combining techniques of insulin fibril template with Pd nanowire template, numerous Pt nanotubes with diameter of 5.5 nm, tube-length of several micrometers, and ultrathin wall thickness of 1 nm are assembled. These tubular catalysts with both open ends deliver electrochemical active surface area (ECSA) of 91.43 m2 gpt-1 which results from multiple Pt atoms exposed on the inner and outer surfaces that doubled Pt atoms can participate in catalytic reactions, further with enhanced electrocatalytic performance for oxygen reduction reaction (ORR). The ultrafine Pt nanotubes represent a class of hollow nanostructure with increased Pt-utilization and large ECSA, which is regarded as a type of cost-effective catalysts for ORR.

Poly(bisphenol-A-etheralkane), BA-Cn(n, which is the number of aliphatic CH2 units, = 8 and 10), composed of rigid and flexible segments, is a semicrystalline polymer. In 50-nm-thick films, the polymers tend to develop flat-on lamellae at the surfaces. Principal component analyses (PCAs) of the ion images were used to discriminate the conformation between the amorphous and flat-on lamellar surfaces of the polymers. The changes of the surface structure were directly detected by time-of-flight secondary ion mass spectrometry chemical imaging when flat-on lamellae were developed from the polymer melts. These structural changes were related to the lengths of the folded segments, which were strongly influenced by the crystallization temperature. The PCA loading analyses suggested that the length of the folded segments, which contained flexible and the rigid segments with an ether linkage, increased when the crystallization temperature decreased, suggesting the kinetic origin of polymer crystallization. Copyright © 2010 John Wiley & Sons, Ltd.

The effect of film thickness on the structural conformation of the surfaces of the amorphous state, edge-on lamellae and flat-on lamellae of a semiflexible polymer, poly(bisphenol-A-etheroctane), was investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS) with the aid of principal component analysis (PCA). PCA results empirically indicate that a structurally regular polymer surface was obtained with the formation of the flat-on lamellae from the amorphous state at a low degree of supercooling. A higher concentration of end group and cilium ion fragments, which are indicative of free chain ends, was observed on the edge-on lamellar surfaces than on the amorphous and the flat-on lamellar surfaces. This finding was attributed to the fact that the lateral surface of the edge-on lamellae contains many growth fronts, leaving behind a large number of uncrystallized chain remnants on the surfaces. Structural disorder was facilitated on both edge-on and flat-on lamellar surfaces as the film thickness decreased. Hence, this PCA study offers new insights into the nonequilibrium nature of polymer crystals and the mechanism of polymer crystallization in thin and ultrathin films.

In this work, we examined the effects of the liquid crystalline ordering on the surfaces of thermotropic fluorocarbon-hydrocarbon polymers (FmHn, with m = 8; n = 8, 10) by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with principal component analysis (PCA). XPS results showed that the liquid crystal surfaces of the polymers were enriched with hydrocarbon segments. PCA of ToF-SIMS data further showed that reversible structural changes between the amorphous and ordered states of the polymers occurred. As these polymers ordered at room temperature, their surfaces were transformed from the amorphous state with fluorocarbon-segment enrichment to the fully ordered liquid crystal states with hydrocarbon-segment enrichment. All these results suggested that the molecular orientation controlled the surface composition of the liquid crystalline polymers notwithstanding the surface energy. The axial alignment of the rigid fluorocarbon mesogens anchored the flexible hydrocarbon segments at the surface. Copyright © 2010 John Wiley & Sons, Ltd.

The fold and lateral surfaces of chain-folded lamellae of poly(bisphenol-A-co-etheroctane), containing both aliphatic CH 2 and aromatic segments, were investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS). At low and high crystallization temperatures, the surfaces of the polymer films were shown to consist mainly of edge-on and flat-on lamellae, respectively. Surfaces with a mixture of edge-on and flat-on lamellae were produced at intermediate temperatures. The edge-on and flat-on lamellae were identified by using ions that recognize the flexible and rigid segments of the polymer. Ion images produced using selected ions that are related to the edge-on or flat-on orientation can be used to identify the location of these lamellae on the polymer surface. Our results indicate that ToF-SIMS can be used to detect different lamellar orientations at the surfaces of semi-crystalline polymers.

Highly porous nanostructures with large surface areas are typically employed for electrical double-layer capacitors to improve gravimetric energy storage capacity; however, high surface area carbon-based electrodes result in poor volumetric capacitance because of the low packing density of porous materials. Here, we demonstrate ultrahigh volumetric capacitance of 521 F cm−3 in aqueous electrolytes for non-porous carbon microsphere electrodes co-doped with fluorine and nitrogen synthesized by low-temperature solvothermal route, rivaling expensive RuO2 or MnO2 pseudo-capacitors. The new electrodes also exhibit excellent cyclic stability without capacitance loss after 10,000 cycles in both acidic and basic electrolytes at a high charge current of 5 A g−1. This work provides a new approach for designing high-performance electrodes with exceptional volumetric capacitance with high mass loadings and charge rates for long-lived electrochemical energy storage systems., Carbon-based supercapacitors often suffer from poor volumetric capacitance due to the low packing density which arises from attempts to increase the electrode surface area. Here, in contrast, the authors fabricate N and F co-doped non-porous solid carbon spheres and achieve exceptional performances.

This paper gives a critical review on the applications of ToF SIMS in the areas of polymer additive characterization and in the study of polymer blends and interfaces. Polymer additives can readily be identified by ToF SIMS using their parent molecular ions or characteristic fragments. This analytical capability has been successfully applied to monitor the migration or segregation of additives during polymer processing. ToF SIMS is an ideal analytical tool for the study of polymer blends and interfaces because it is able to provide information on both surface composition and morphology. In combination with other analytical techniques such as AFM and XPS, ToF SIMS chemical imaging capability has opened up new horizons in the investigation of complex polymer blend systems. Finally the main advantages and limitations of ToF SIMS in these application areas are also discussed.