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Sensitive data collected by a wireless sensor network (WSN) should be protected by a secret key shared between two adjacent (or neighboring) sensors. Sensors are mobile devices with limited memory and computational power, and sensors are deployed in a field randomly in which relative positions among sensors cannot be pre‐determined. Key distribution in WSN is a challenging research problem. Random key distribution is one of the most popular key distribution techniques in WSN; but it is a probabilistic key distribution scheme since two neighboring sensors may or may not share any pairwise key. There are many published papers to improve the probability of connectivity of two neighboring sensors. In this paper, a novel design of lightweight key establishment is proposed based on top of random key distribution. The first scheme can increase the probability of connectivity of two neighboring sensors, and the second scheme can also enable sensors to authenticate the established pairwise key. Both schemes need only XOR operation so they are lightweight and especially suitable for WSNs.

One of the major challenges regarding the sulfur cathode of Li-S batteries is to achieve high sulfur loading, fast Li ions transfer, and the suppression of lithium polysulfides (LiPSs) shuttling. This issue can be solved by the development of molybdenum carbide decorated N-doped carbon hierarchical double-shelled hollow spheres (Mo2 C/C HDS-HSs). The mesoporous thick inner shell and the central void of the HDS-HSs achieve high sulfur loading, facilitate the ion/electrolyte penetration, and accelerate charge transfer. The microporous thin outer shell suppresses LiPSs shuttling and reduces the charge/mass diffusion distance. The double-shelled hollow structure accommodates the volume expansion during lithiation. Furthermore, Mo2 C/C composition renders the HDS-HSs cathode with improved conductivity, enhanced affinity to LiPSs, and accelerated kinetics of LiPSs conversion. The structural and compositional advantages render the Mo2 C/C/S HDS-HSs electrode with high specific capacity, excellent rate capability, and ultra-long cycling stability in the composed Li-S batteries.

Water electrolysis offers a promising green technology to tackle the global energy and environmental crisis, but its efficiency is greatly limited by the sluggish reaction kinetics of both the cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER). In this work, by growing amorphous multi-transition-metal (cobalt and iron) oxide on two-dimensional (2D) black phosphorus (BP), we develop a bifunctional electrocatalyst (CoFeO@BP), which is able to efficiently catalyze both HER and OER. The overpotentials for the hybrid CoFeO@BP catalyst to reach a current density of 10 mA cm-2 in 1 m KOH are 88 and 266 mV for HER and OER, respectively. Based on a series of ex-situ and in situ investigations, the excellent catalytic performance of CoFeO@BP is found to result from the adaptive surface structure under reduction and oxidation potentials. CoFeO@BP can be transformed to CoFe phosphide under reduction potential, in situ generating the real active catalyst for HER.

Executive function (EF) refers to a set of cognitive abilities involved in self‐regulated behavior. Given the critical role of EF in cognition, strategies for improving EF have attracted intensive attention in recent years. Previous studies have explored the effects of abacus‐based mental calculation (AMC) training on several cognitive abilities. However, it remains unclear whether AMC training affects EF and its neural correlates. In this study, participants were randomly assigned to AMC or control groups upon starting primary school. The AMC group received 2 h AMC training every week, while the control group did not have any abacus experience. Neural activity during an EF task was examined using functional MRI for both groups in their 4(th) and 6(th) grades. Our results showed that the AMC group performed better and faster than the control group in both grades. They also had lower activation in the frontoparietal reigons than the control group in the 6(th) grade. From the 4(th) to the 6(th) grade, the AMC group showed activation decreases in the frontoparietal regions, while the control group exhibited an opposite pattern. Furthermore, voxel‐wise regression analyses revealed that better performance was associated with lower task‐relevant brain activity in the AMC group but associated with greater task‐relevant brain activity in the control group. These results suggest that long‐term AMC training, with calculation ability as its original target, may improve EF and enhance neural efficiency of the frontoparietal regions during development. Hum Brain Mapp 38:5234–5249, 2017. © 2017 Wiley Periodicals, Inc.

In delay tolerant networks, most of the existing message forwarding algorithms prefer to deliver messages to the nodes with a higher popularity or centrality in the hope of maximizing the delivery ratio or minimizing the end-to-end delay. This forwarding scheme is prone to cause unfair load distribution and further lead to network congestion, overlooked in the previous work. In this paper, we discuss the network congestion from a community perspective and take it into account the design of message forwarding algorithms. We first put forward a novel distributed community detection approach, which could track the evolution of communities. Based on the identified communities, we develop a congestion avoidance mechanism to divert the load away from the congested areas to the alternative custodians and further present a congestion-aware message forwarding algorithm where messages can avoid being transmitted to the congested nodes. We finally evaluate the effectiveness of distributed community detection and congestion-aware message forwarding through the extensive real-trace driven simulations. Copyright © 2015 John Wiley & Sons, Ltd.

In Identity-Based Encryption IBE systems, there is a widespread concern over the issue on how to provide an efficient revocation mechanism. We develop a new approach in constructing an efficient revocable IBE scheme. Our approach utilizes recent advances in multilinear maps and combines a two-level hierarchical IBE scheme with a revocation encryption system. In our revocable IBE scheme, both the public parameters and the private key are constant-size. Simultaneously, the size of the update key at some time is only proportional to the number of revoked users at the time. Our proposed scheme is proven secure in the selective revocation list model without relying on random oracles. Copyright © 2015 John Wiley & Sons, Ltd.

We revisit the problem of basing signcryption SC tag key encapsulation mechanism KEM on standard assumptions and standard model and present direct constructions of SC-KEM/tag-KEM, which satisfy confidentiality and unforgeability with respect to adversarially chosen keys where the adversary is given more advantageous attack environment than existing models in the literature;are based on the standard decisional bilinear Diffie-Hellman and computational Diffie-Hellman assumptions without random oracle;do not use strongly unforgeable signature schemes as building blocks; andprovide comparable performance to existing SC-KEM/tag-KEM schemes.

Ultrasensitive detection of nucleic acid has attracted considerable attention recently in academic research and clinic diagnostics. Current approaches for DNA analysis involve complicated or expensive processes for labeling and often yield a high detection limit. In this study, a hydrogel electrode prepared from graphene oxide and fish sperm DNA is used for label−free mitochondrial DNA detection by impedimetric approach. The hydrogel has a bionic structure containing rich water and natural biomolecule fish sperm DNA that would benefit the adsorption and hybridization of DNA. Graphene oxide is a semiconductor and its conductivity can be improved by doping negatively charged DNA molecules. The result shows that the conductivity and impedance change of hydrogel electrode could be tuned by its length and component. The linear range for DNA detection by the optimized hydrogel is from 1.0 × 10−9 to 1.0 × 10−20 M with a detection limit of 1.0 × 10−20 M. The result is ascribed to the bionic structure and tunable conductivity of hydrogel electrode. The hydrogel electrode has been used to detect the real DNA samples from patients of ovarian cancer with satisfactory results.

basal plane would provide a template for self-assembly of monodispersed latex spheres to form PCs in aqueous solution. Latex particles are the most favorable building blocks for the self-assembly of colloidal PCs because they can be readily synthesized as monodispersed particles. [ 17–19 ] The most commonly used polymer in latex spheres is polystyrene (PS) that could be produced in many different polymerization routes. Herein, we report a solution graphene-based PC (SGPC) by in situ-free radical polymerization of styrene, acryl amide (AM), and acrylic acid (AA) on the surface of graphene to display a structurally blue color in aqueous solution. The wavelength of blue color lies in the visible range, making it particularly attractive for a variety of applications. The blue SGPC with a value of −37.4 mV of zeta potential is very stable in aqueous solution, so far for about 2 years. The blue SGPC is stable when pH is over 5 and the SGPC solid can also dissolve in water, ethanol, methanol, and polyethylene glycol with a blue color. It is very convenient to prepare the membranes with a blue color and suitable for large-scale industry. At the same time, SGPC can detect trace aromatic solvents (1.0 ng mL −1 ) by changing its color from blue to white very quickly. The preparation of graphene oxide (GO) and reduced graphene oxide (RGO) was described in our previous reports. [ 14,20,21 ]

Constructing an atlas from a population of brain images is of vital importance to medical image analysis. Especially in neuroscience study, creating a brain atlas is useful for intra‐ and inter‐population comparison. Research on brain atlas construction has attracted great attention in recent years, but the research on pediatric population is still limited, mainly due to the limited availability and the relatively low quality of pediatric magnetic resonance brain images. This article is targeted at creating a high quality representative brain atlas for Chinese pediatric population. To achieve this goal, we have designed a set of preprocessing procedures to improve the image quality and developed an intensity and sulci landmark combined groupwise registration method to align the population of images for atlas construction. As demonstrated in experiments, the newly constructed atlas can better represent the size and shape of brains of Chinese pediatric population, and show better performance in Chinese pediatric brain image analysis compared with other standard atlases. Hum Brain Mapp 35:3880–3892, 2014. © 2014 Wiley Periodicals, Inc.

In password-based or two-factor password and smart card authentications, password changing is one of common techniques used to improve the security of the systems protected by the password. However, the password-changing operations in existing password authentications either depend on the login phase or violate the common practice that an old password should not be valid for subsequent login after being updated. On the other hand, password mistyping is very common in reality, which may be random or be skewed by the adversary via technical means or social engineering manipulation [i.e., a kind of denial-of-service DoS attack]. In human-centric authentication mechanisms, password changing and DoS resilience are not marginal issues. The paper addresses the requirements of robust password changing in authentication and presents SPCA, a password authentication scheme with robust password changing, DoS resilience, and card-compromise security. Thus, the proposal can be viewed as a suitable candidate instantiation for authentication services of human-centric security, by embedding in the computer and software systems. SPCA also achieves other appealing features, such as self-healing ability and strong privacy protection, which may be useful for human-centric applications. Copyright © 2013 John Wiley & Sons, Ltd.

We present the preparation of advanced antistatic and anticorrosion coatings of polystyrene (PS) incorporating a suitable amount of dodecylbenzenesulfonic acid (DBSA)-doped SiO2@polyaniline (SP) core – shell microspheres. First, aniline-anchored SiO2 (AS) microspheres that were about 850 nm in diameter were synthesized using the conventional base-catalyzed sol – gel process with tetraethyl orthosilicate in the presence of N-[3-(trimethoxysilyl)propyl]aniline. SP core – shell microspheres were then synthesized by chemical oxidative polymerization of aniline monomers with ammonium persulfate as an oxidizing agent in the presence of the AS microspheres. The polyaniline shell thickness of the as-prepared core – shell microspheres was estimated to be about 120 nm. The AS and SP microspheres were further characterized using Fourier transform infrared spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy. The as-synthesized DBSA-doped SP core – shell microspheres were then blended into PS using N-methyl-2-pyrrolidone as solvent and then cast onto a cold – rolled steel (CRS) electrode to obtain antistatic and anticorrosion coatings with a thickness of about 10 µm. The corrosion protection efficiency of the as-prepared coating materials on the CRS electrode was investigated using a series of systematic electrochemical measurements under saline conditions. The enhanced corrosion protection ability of the PS/SP composite coatings may be attributed to the formation of a dense passive metal oxide layer induced by the redox catalytic effect of the polyaniline shell of the as-synthesized core – shell microspheres, as evidenced by electron spectroscopy for chemical analysis and SEM observations. Moreover, the PS composite coating containing 10 wt% of the SP core – shell microspheres showed an electrical resistance of about 3.65 × 10 9 � cm −2 , which meets the requirements for antistatic applications. c � 2012 Society of Chemical Industry

Graphene can inhibit non-specific DNA fragments, and the specificity of the polymerase chain reaction (PCR) can be retained even after eight rounds of repeated amplification in the presence of graphene in the form of reduced graphene oxide (RGO). In the figure, the numbers at the top give the number of rounds of PCR; lanes marked with C correspond to controls (no RGO), and the concentration of RGO in the other samples is 12 μg mL(-1) .

The superhydrophobic surface (SHS) applied for corrosion protection in this study was prepared from an organic fluorinated polyacrylate incorporated with methyltriethoxysilane (MTES)-based silsesquioxanes spheres. The SHS, with a contact angle of about 153.2°, was coated onto the surface of cold-rolled steel (CRS) with spin-coating technology. The coating materials applied as anticorrosive coatings were based on a series of electrochemical corrosion-protection measurements in saline conditions. The SHS coating on CRS was found to provide superior corrosion protection to that of the hydrophobic organic coating in a series of electrochemical measurements in 3.5 wt % aqueous NaCl electrolyte. This form of coating could also provide better corrosion protection to coated CRS substrates and could serve as an effective barrier against aggressive species. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

A series of sol–gel derived organic–inorganic hybrid coatings consisting of organic poly (vinyl carbazole) (PVK) and inorganic silica (SiO2), with 3-(trimethoxysilyl)propyl methacrylate (MSMA) as coupling agent, were successfully synthesized. First of all, vinyl carbazole (VCz) monomers are copolymerized with MSMA by performing free-radical polymerization reactions with AIBN as initiator. Subsequently, as-prepared copolymer (i.e., sol–gel precursor) was further reacted with various feeding content of tetraethyl orthosilicate (TEOS) through organic acid (CSA)-catalyzed sol–gel reaction to form a series of PVK-silica hybrid (PSH) sol–gel materials. The as-synthesized hybrid materials were subsequently characterized by Fourier-Transformation infrared (FTIR) spectroscopy and solid-state 29Si NMR. It should be noted that the PVK-SiO2 hybrid (PSH) coating on cold-rolled steel (CRS) electrode with low silica loading (e.g., 10 phr) was found to be superior in anticorrosion property over those of neat PVK based on a series of electrochemical measurements such as corrosion potential, polarization resistance, corrosion current, and electrochemical impedance spectroscopy in 3.5 wt% NaCl electrolyte. The better anticorrosion performance of PSH coatings as compared to that of neat polymer may probably be attributed to the stronger adhesion strength of PSH coatings on CRS electrode, which was further evidenced by Scotch tape test evaluation. Increase of adhesion strength of PSH coatings on CRS electrode may be associated with the formation of Fe–O–Si covalent bonds at the interface of PSH coating and CRS electrode based on the FTIR–RAS (reflection absorption spectroscopy) studies. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers

In this study, electroactive polyimide microspheres (EPSs) based on conjugating segments of electroactive aminocapped aniline trimer as diamine and 4,4′-(4,4′-isopropylidenediphenoxy)-bis(phthalic anhydride) as dianhydride were successfully prepared by electrospraying technology and characterized by time of flight mass spectroscopy, 1H-NMR, Fourier transform infrared spectroscopy and cyclic voltammetry. The prepared electroactive polyimide was then dissolved in a suitable organic solvent (N,N-dimethylformamide; N-methyl-2-pyrrolidone) followed by electrospraying treatment under four different operational parameters (i.e. solution concentration, applied voltage, feeding rate and deposition distance) to give EPSs of various diameters. Moreover, EPSs deposited on the Pt electrode were tested in a 1.0 mol L−1 H2SO4 aqueous solution by cyclic voltammetry which showed an obvious redox peak similar to polyaniline. Copyright © 2011 Society of Chemical Industry

A neat electroactive freestanding non-woven mat was first prepared from poly(o-methoxyaniline) (POMA) using an electrospinning technique without blending or grafting. Results showed that a continuous fibre structure was obtained for high weight-average molecular weight Mw of POMA, i.e. POMA forced to become more soluble when synthesized in the presence of CaCl2 and an alkoxyl-ring-substituted structure. By performing gel permeation chromatography and viscosity tests, we found that Mw ≈ 69 000 g mol−1 and concentrations were critical to the formation of beads or fibres. The electrospinning parameters that cause morphological changes were found by scanning electron microscopy. By comparing these with governing parameters such as viscosity, feeding rate, collector distance and applied voltage, uniform POMA fibres were produced from 5 wt% POMA solution at 20 kV with a feeding rate of 0.02 mL min−1 and nozzle-to-collector distance of 12 cm. In addition, the electroactivity and mechanical strength of the neat electrospun non-woven mats were studied by electrochemical cyclic voltammogram and dynamic mechanical analysis, respectively. Copyright © 2011 Society of Chemical Industry

In this article, a comparative study of the preparation and physical properties of as-prepared PMMA-silica nano-hybrid (PSN) and sub-micro-hybrid (PSM) latexes is successfully presented. Vinyl-modified silica spheres were prepared using the Stob er pro- cess with/without a chelating agent to control parti- cle size. The as-prepared vinyl-modified silica spheres with different particle sizes were subse- quently characterized by SEM, 13 C-solid-state NMR, and 29 Si-solid-state NMR spectroscopy. A certain feeding amount of silica spheres was reacted with MMA monomers by emulsion polymerization to yield a series of PSN and corresponding PSM. Both as-prepared nano/sub-micronscale hybrid materials were further characterized by FTIR, SEM-EDX map- ping, and TEM studies. The comparative study on the physical properties of both as-prepared nano/sub- micron-scale hybrid materials was done systemati- cally based on a series of instrumentation evalua- tions performed using a dynamic mechanical ana- lyzer, electrochemical corrosion measurements, salt spray test, and gas permeability analysis. Results indicated that PSN has more effectively enhanced mechanical properties, corrosion protection proper- ties, as well as gas barrier compared to PSM. POLYM. COMPOS., 32:1607-1616, 2011. a 2011 Society of Plastics

In this paper, a comparative study with regard to the preparation and physical properties of as-prepared polystyrene – silica mesocomposite (PSM) and polystyrene-silica nanocomposite (PSN) materials is presented. Vinyl-modified mesoporous silica particles with a wormhole structure were first prepared by doping a sol-gel metal oxide with an optically active nonsurfactant (dibenzoyl-L-tartaric acid) as a template, followed by template removal through Soxhlet extraction. The as-prepared silica particles with/without mesopores were subsequently characterized using the Brunauer – Emmett – Teller method and transmission electron microscopy (TEM) and Fourier transform infrared, 13 CN MR and 29 Si NMR solid-state spectroscopy. A specific feed amount of silica particles was subsequently reacted with styrene monomer by free radical polymerization to yield a series of PSM and corresponding PSN materials. Both as-prepared composite systems were further characterized using TEM and scanning electron microscopy/energy-dispersive X-ray mapping studies. A systematic comparative study of the physical properties of both as-prepared composite materials clearly illustrated that PSM had effectively enhanced thermal stability, optical clarity and dielectric properties compared to the corresponding PSN counterpart. Evaluation was carried out using thermogravimetric analysis, differential scanning calorimetry, UV-visible transmission spectroscopy and dielectric constant measurements. c � 2011 Society of Chemical Industry

Series of advanced anticorrosive hybrid coatings comprising of organo-soluble fluorinated polyimide (SFPI) matrix dispersed with different feeding ratio of inorganic silica (SiO2) nanoparticles has been successfully prepared through a conventional chemical imidization of polyimide and acid catalyzed sol–gel process of TEOS. It should be noted that the incorporation of SiO2 nanoparticles into the SFPI matrix can effectively enhance the corrosion protection performance on cold-rolled steel (CRS) electrode against corrosive species in saline condition when compared with that of neat polymeric coatings based on a series of standard electrochemical corrosion measurements, such as corrosion potential, polarization resistance, corrosion current, and impedance spectroscopy. POLYM. COMPOS., 31:2025–2034, 2010. a 2010 Society of Plastics Engineers

In this work, the mechanism analysis of Poly(DL-lactic acid) (PLA) particles formation is investigated by dissipative particle dynamics (DPD) simulations. The polymer PLA is usually as a carrier at the drug deliver system (DDS), first, the mechanism analysis of PLA particles formation was preceded on the basis of the blank PLA particles. At the same time, the formation of PLA particles for drug delivery systems has been investigated. The results of DPD simulations indicate that the formation of PLA particles with drug or not, consists of three steps: (1) aggregation-individual PLA chains got aggregated with each other in solution; (2) formation and disruption of PLA particles; (3) solidification of PLA particles. At the same time, the effects of PLA, drug content on the aggregation morphology are investigated, which indicates the PLA particles with drug or not aggregated and formed is spherical particles, drug molecules are amorphously and homogeneously distributed inside the PLA matrix, the size of PLA particles increases with increasing the initial PLA content and drug content in the solution. The content of DMF is gotten when PLA chains and drug molecules begin to aggregate and form the particles. These could be used to guide the experimental preparation of PLA blank particles and DDS with desired properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

A series of sol-gel derived organic-inor- ganic hybrid coatings consisting of organic epoxy resin and inorganic silica were successfully synthesized through sol-gel approach by using 3-glycidoxypropyl-tri- methoxysilane as coupling agent. Transparent organic- inorganic hybrid sol-gel coatings with different contents of silica were always achieved. The hybrid sol-gel coat- ings with low silica loading on cold-rolled steel coupons were found much superior improvement in anticorrosion efficiently. The as-synthesized hybrid sol-gel materials were characterized by Fourier-transformation infrared spectroscopy, 29 Si-nuclear magnetic resonance spectros- copy and transmission electron microscopy. Effects of the material composition of epoxy resins along with hybrid materials on the thermal stability, Viscoelasticity proper- ties and surface morphology were also studied, respec

In this study, a series of organic-inorganic hybrid sol-gel materials consisting of a poly(methyl meth- acrylate) (PMMA) matrix and dispersed silica (SiO2) par- ticles were successfully prepared through an organic-acid- catalyzed sol-gel route with N-methyl-2-pyrrolidone as the mixing solvent. The as-synthesized PMMA-SiO2 nanocom- posites were subsequently characterized with Fourier transform infrared spectroscopy and transmission electron microscopy. The solid phase of organic camphor sulfonic acid was employed to catalyze the hydrolysis and conden- sation (i.e., sol-gel reactions) of tetraethyl orthosilicate in the PMMA matrix. The formation of the hybrid mem- branes was beneficial for the physical properties at low SiO2 loadings, especially for enhanced mechanical strength and gas barrier properties, in comparison with the neat PMMA. The effects of material composition on the thermal stability, thermal conductivity, mechanical strength, molec- ular permeability, optical clarity, and surface morphology of the as-prepared hybrid PMMA-SiO2 nanocomposites in the form of membranes were investigated with thermogra- vimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, gas permeability analysis, ultraviolet-visible transmission spectroscopy, and atomic force microscopy, respectively. V C 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 2108-2114, 2008

Amine-modified carbon micro/sub-microtubes that encapsulate magnetite cores have been synthesized by decomposing a ferrocene/hexabromobenzene mixture in the presence of ammonia under solvothermal conditions at 250°C for 24 h in a one-step process. The as-prepared carbon microstructures (NH 2 -ME-CMTs) were 90-2000nm in diameter and from tens to hundreds of micrometers in length that could be tuned in various solvents. The surface of the carbon microtubes can be modified with amino groups by the synthetic process, as confirmed by infra-red (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Ammonia in the reaction system plays a key role in the formation of the microtube morphology and was the source of the surface functionalization groups. Fluorescent fluorescein isothiocyanate (FITC) was selected as a model compound and successively attached to the amino groups of the carbon microtubes. This result confirms the reactivity of the amino groups on the surface of the carbon microtubes. The inner magnetite cores were removed after immersion in 1 M HCl solution at room temperature over two months, and hollow carbon microtubes (NH 2 -H-CMTs) were obtained. The magnetite-encapsulated carbon microtubes and the hollow carbon microtubes were coated on gold electrodes to prepare carbon microtube-modified gold electrodes. The two electrodes have been used to investigate the oxidative properties of dopamine (DA) and ascorbic acid (AA). Different from the magnetite-encapsulated microtube-modified electrode, the hollow microtube-modified electrode can be utilized in the selective detection of DA in the presence of a large excess of AA. The electrochemical behaviour of DA and AA on the hollow carbon microtubes modified with amino groups is similar to that on carbon nanotubes. This result suggests that the one-step synthesis method will not change the electrochemical properties or break the backbone structure of the carbon microtubes.

We have successfully controlled the shape of gold nanocrystals through a simple and low-cost hydrothermal method based on a modified polyol process. Well-defined gold nanocrystals of icosahedral shape were synthesized in high yields by the rapid reduction of gold precursors with ethylene glycol (EG) in the presence of poly(vinyl pyrrolidone) (PVP) under hydrothermal conditions for 1 h. Truncated icosahedra (football-shaped) have been prepared for the first time by prolonging the reaction time to 4 h. Both nanocrystal shapes were obtained quantitatively. Addition of citric acid inhibits the shape-change process (from icosahedron to truncated icosahedron) by blocking oxidative etching, while addition of Fe(III) facilitates the shape-change process by enhancing oxidative etching. We propose that growth of truncated icosahedra can be induced and maintained through interplay of the following processes: generation of multiple twinned seeds, shape- and size-focusing by Ostwald ripening, and oxidative etching and preferential growth on the {100} face.

Gold clusters have been electrodeposited on a boron-doped diamond (BDD) electrode by scanning the potential from 0.7 V to 0.0 V (vs. 3 M KCl-Ag/AgCl reference) in a solution of 0.5 mM KAuCl 4 and 1.0 M KCl. The cluster-modified diamond (Au/ BDD) electrode has been used to investigate the oxidative properties of dopamine (DA) and ascorbate (AA). The modified diamond electrode shows a higher activity for DA oxidation than AA; the oxidation potential of DA shifted to a less-positive potential (0.11 V) than that of AA, which oxidized at 0.26 V, and DA possesses a much higher peak current than that of AA. The reversibility of the electrode reaction with DA is significantly improved at the Au/BDD electrode, which results in a large increase in the square-wave voltammetric peak current, with a detection limit of 0.1 μM in the presence of a large excess of AA. The Au/BDD electrode shows excellent sensitivity and good selectivity for DA detection. A self-assembled monolayer (SAM) of mercaptoacetic acid on the Au clusters was used to provide an antifouling effect as the negative CO 2 - groups repulse negative ascorbate and attract positive dopamine in pH 7.4 buffer. After pre-absorption, the SAM/Au/BDD electrode could detect 1.0 nM DA in a linear range from 10 nM to 10 μM in the presence of 10 - 4 M AA.

We synthesized a series of cyclens substituted with mixed stilbene and poly(ethylene glycol) dendritic arms. All dendrimers terminated with different peripheral groups had good solubility in common organic solvents, and dendrimers terminated with CO2H groups (CO2H-dendrimers) were also soluble in alkaline solutions. The nickel coordination properties of these dendrimers were investigated in organic solvents. Dendrimers terminated with CN groups (CN-dendrimers) and the second-generation CO2H-dendrimer [(CO2H)8L2] could produce pentacoordinated nickel complexes; the third-generation CO2H-dendrimer [(CO2H)16L3] could form tetra- and pentacoordinated nickel complexes, and the nickel complex of the fourth-generation CO2H-dendrimer [(CO2H)32L4] could not be obtained. This result was due to the fact that the globular surface of (CO2H)16L3 formed a hydrogen-bond network that selectively penetrated cations and inhibited the access of anions to the core. The formation of the hydrogen-bond network was confirmed by Fourier transform infrared, 1H NMR, and fluorescence data. The CN-dendrimers could not form hydrogen bonds on the surface, and the first- and second-generation CO2H-dendrimers could not form intramolecular hydrogen-bond networks. Therefore, they had no selectivity for positive nickel ions and negative chloride ions. (CO2H)32L4 could not produce a nickel complex because it had a crammed backbone structure that could not penetrate nickel and chloride ions. Therefore, it was possible to control the ion access of cations and anions with the hydrogen-bond network of (CO2H)16L3. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5414–5428, 2005

A series of sol-gel derived organic-inorganic hybrid materials consisting of organic poly(methyl methac- rylate) (PMMA) and inorganic titania (TiO2) were success- fully synthesized by using 2-hydroxyethyl methacrylate (HEMA) as coupling agent. In this work, HEMA is first copolymerized with methyl methacrylate monomer at spe- cific feeding ratios by using benzoyl peroxide (BPO) as initiator. Subsequently, the as-prepared copolymer (i.e., sol- gel precursor) is then cohydrolyzed with various contents of titanium butoxide to afford chemical bondings to the form- ing titania networks to give a series of hybrid materials. Transparent organic-inorganic hybrid materials with differ- ent contents of titania are always achieved. Effects of the material composition on the thermal stability, optical prop- erties, and morphology of neat copolymer and a series of hybrid materials, in the form of both coating and free-stand- ing film, are also studied by differential scanning calorime- try, thermogravimetric analysis, UV-Vis transmission spec- tra, refractometer, and atomic force microscopy, respec- tively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 400 - 405, 2004

Three novel bithiazole-containing polymers were synthesized from 2,2′-diamino-4, 4′-bithiazole (DABT) condensed with bismaleimide, bis(methyloxycarbonyl ethyl)tin dichloride (BETD), and 4,4′-diphenylmethane diisocyanate (DPDI), respectively. A new series of polymeric complexes were prepared from Fe2+ and the three polymers. These polymers and their complexes were characterized through FTIR, 1H-NMR, and related techniques. The chemical compositions of the complexes were determined by XPS. The presence of the exchange interaction between the unpaired electrons was investigated by ESR spectroscopy. The magnetic behavior of these complexes was measured as a function of the magnetic field strength (0–40 kOe) at 5 K and as a function of temperature (5–300 K) at a magnetic field strength of 30 kOe. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1353–1359, 2001

Three polymer-Fe 2+ complexes were synthesized from Fe 2+ and poly(Schiff base)s. The poly-(Schiff base)s were prepared from 2,2'-diamino-4,4'-bithiazole (DABT) with phthalaldehyde, 5,5'-methylene-bis(salicylaldehyde) (MBSA) and terephthalaldehyde, respectively, and characterized by IR, XPS, NMR and ESR spectroscopy. The magnetic behavior of these polymer-Fe 2+ complexes was examined as a function of magnetic field strength and temperature (5-300 K), respectively. The hysteresis loops were also studied. Based on these results, several novel derromagnets were obtained.

Poly(vinyl acetal) from poly(vinyl alcohol) and 4-dimethylaminobenzaldehyde (DMAB) is synthesized. Fluorescence behavior of the polymer is investigated in acetic acid glacial (HAc), dimethylsulfoxide (DMSO), and dimethylformamide (DMF) solvents. Fluorescence emission intensities of the polymer solutions are different with the change of concentration. The result suggests that the maximum fluorescence emission intensities of the polymer solutions depend on the optimal concentration of the polymer. It has been found that the fluorescence intensity of DMAB is dramatically lower than that of the polymer in the same chromophore concentration, and such phenomenon is termed as structural self-quenching effect (SSQE). The strong fluorescence of the polymer can be quenched by adding electron-deficient monomers which have no chromophore moieties such as lactic acid, adenine, etc., and their Stern–Volmer constants are determined. It is observed that the higher the electron deficiencies of the quenchers, the higher the Stern–Volmer constants, which means stronger quenching effect. The result indicates that the polymer can recognize these biologic small molecules. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2385–2390, 1999

(N2H4)3 (N2H5)4Sn2Se6 complexes, synthesized by dissolving elemental tin and selenium in hydrazine under ambient conditions, are used as precursors for SnSe2 deposition on TiO2 nanocrystalline porous films.

The adverse effects of heat stress are a major limitation to realizing the genetic potential for productivity of wheat (Triticum aestivum L.). This study was undertaken to characterize the temperature-dependent induction response of heat-shock protein (HSP) synthesis in wheat seedlings, and to determine if HSPs could be detected in flag leaves of flowering wheat plants at nonlethal temperatures similar to those encountered during agricultural production(.)