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Compared to traditional electric double-layer capacitors, redox-enhanced electrochemical capacitors (redox-ECs) show increased energy density and steadier power output thanks to the use of redox-active electrolytes. The aim of this study is to understand the electrochemical mechanisms of the aqueous pentyl viologen/bromide dual redox system at the interface of an ordered mesoporous carbon (CMK-8) and improve the device performance. Cells with CMK-8 carbon electrodes were investigated in several configurations using different charging rates and potential windows. The pentyl viologen electrochemistry shows a mixed behavior between solution-based diffusion and adsorption phenomena, with the reversible formation of an adsorbed layer. The extension of the voltage window allows for full reduction of the viologen molecules during charge and a consequent increase in the specific discharge energy delivered by the cell. Investigation of the mechanism indicates that a 1.5 V charging voltage with a 0.5 A g-1 charging rate and fast discharge rate produces the best overall performance.

The molecules feeding life's emergence are thought to have been provided through the hydrothermal interactions of convecting carbonic ocean waters with minerals comprising the early Hadean oceanic crust. Few laboratory experiments have simulated ancient hydrothermal conditions to test this conjecture. We used the JPL hydrothermal flow reactor to investigate CO

The chemical reactivity and/or the diffusion of Ag atoms or ions during thermal processing can cause irreversible structural damage, hindering the application of Ag nanowires (NWs) in transparent c...

Janus nanoparticles (JNPs) offer unique features, including the precisely controlled distribution of compositions, surface charges, dipole moments, modular and combined functionalities, which enable excellent applications that are unavailable to their symmetrical counterparts. Assemblies of NPs exhibit coupled optical, electronic and magnetic properties that are different from single NPs. Herein, we report a new class of double-layered plasmonic-magnetic vesicle assembled from Janus amphiphilic Au-Fe3 O4 NPs grafted with polymer brushes of different hydrophilicity on Au and Fe3 O4 surfaces separately. Like liposomes, the vesicle shell is composed of two layers of Au-Fe3 O4 NPs in opposite direction, and the orientation of Au or Fe3 O4 in the shell can be well controlled by exploiting the amphiphilic property of the two types of polymers.

A large (40 mm ϕ) composite membrane with mesoporous silica nanotubes (F127MST) was coated with a thin carbon layer (1–2 graphene sheets) by carrying out chemical vapor deposition (CVD) using acetylene, and the obtained carbon-coated F127MST (C/F127MST) was used directly as an electrode. After evaluating the electrical conductivity inside the continuous mesopore network, the enzyme bilirubin oxidase (BOD) was loaded into the mesopores of C/F127MST to form BOD–C/F127MST. Indeed, this loading procedure was effective and achieved direct electron transfer between the enzymes and electrodes. The loading also was found to enhance the stability of stored BOD (it was stable for 15 days) and could be used to control the enzymatic reaction by varying the electric potential. We therefore consider BOD–C/F127MST to be a promising candidate as an effective bioelectrode in various fields.

AgPd alloy nanoparticles deposited on carbon nitride have been synthesized by a facile one-step reduction method and exhibit high catalytic activity at near room temperature (30 °C) for formic acid dehydrogenation, both under visible light and in darkness. The study proves that using the synergistic combination of alloying effects and metal-support interactions greatly enhances the catalytic activity of Pd-based nanocatalysts for hydrogen generation.

The performance of redox-enhanced electrochemical capacitors (redox ECs) is substantially improved when oxidized catholyte (bromide) and reduced anolyte (viologen) are retained within the porous electrodes through reversible counterion-induced solid complexation. Investigation of the mechanism illustrates design principles and identifies pentyl viologen/bromide (PV/Br) as a new high-performance electrolyte. The symmetric PV/Br redox EC produces a specific energy of 48.5 W·h/kgdry at 0.5 A/gdry (0.44 kW/kgdry) with 99.7% Coulombic efficiency, maintains stability over 10 000 cycles, and functions identically when operated with reversed polarity.

SiC oxidizes and is structurally unstable at temperatures above 1000 ​°C in a water-containing oxidative gaseous environment. Herein, we explore the hydrothermal stability of high-surface-area mesoporous SiC (m-SiC) prepared using Pluronic F-127 as structure directing agent, with and without boron doping as synthesized by a magnesiothermic reduction method (700 ​°C for 12 ​h). Under hydrothermal treatment at 800 ​°C in a water-saturated air stream, the undoped m-SiC is completely oxidized and reduced to amorphous SiO2. Lightly doped boron-substituted m-SiC (m-BxSiC, B/Si ​= ​0.04) is significantly more stable and retains the structural characteristics of m-SiC. m-BxSiC shows significant (300 ​°C) catalytic performance (CO conversion, HC conversion, and NO oxidation), better Pt dispersibility, and retention of a smaller Pt particle size. Studies of hierarchically porous m-BxSiC/PS prepared with F-127 and polystyrene dual templating further confirmed the enhancement by boron doping of the 800 ​°C hydrothermal stability and the 300 ​°C catalytic activity.

One model for the emergence of life posits that ancient, low temperature, submarine alkaline hydrothermal vents, partly composed of iron-sulfides, were capable of catalyzing the synthesis of prebiotic organic molecules from CO2, H2 and CH4. Specifically, hydrothermal mackinawite (FeIIS) and greigite (FeIIFeIII2S4) have been highlighted in previous studies as analogs of the active centers of hydrogenase, ferredoxin, acetyl coenzyme-A synthase and carbon monoxide dehydrogenase featured in the biochemistry of certain autotrophic prokaryotes that occupy the base of the evolutionary tree. Despite the proposed importance of iron sulfide minerals and clusters in the synthesis of abiotic organic molecules, the mechanisms for the formation of these sulfides from solution and their preservation under the anoxic and low temperature (below 100 °C) conditions expected in off-axis submarine alkaline vent systems is not well understood ( Bourdoiseau et al., 2011 , Rickard and Luther, 2007 ). To rectify this, single hydrothermal chimneys were precipitated using a unique apparatus to simulate growth at hydrothermal vents of moderate temperature under supposed Hadean ocean-bottom conditions. Iron sulfide phases were observed through Raman spectroscopy at growth temperatures ranging from 40° to 80 °C. Fe(III)-containing mackinawite is confirmed to be present with mackinawite and greigite, supporting an FeIII-mackinawite intermediate mechanism for the transformation of mackinawite to greigite below 100 °C. Raman spectroscopy of the chimneys revealed a maximum yield of greigite at 75 °C. These results suggest abiotic production of catalytically active mackinawite and greigite are possible under early Earth hydrothermal conditions as well as on other wet, rocky worlds geochemically similar to the Earth.

Comparing active site reactivity Noble metal nanoparticles often exhibit behaviors distinct from atomic and bulk versions of the same material. Gold and platinum dispersed on metal oxide supports, for example, show remarkable low-temperature reactivity for carbon monoxide (CO) oxidation by oxygen or water. Ding et al. used infrared spectroscopy to identify CO adsorbed on isolated platinum atoms or nanoparticles dispersed on zeolite and oxide supports. Temperature-programmed desorption studies showed that CO reacted at much lower temperatures when adsorbed on nanoparticles versus on isolated metal atoms. Science , this issue p. 189

A high-yielding synthesis of a series of polyimide dendrimers, including decacyclene- and perylene-containing dendrimer D6, in which two types of polyimide dyes are present, is reported. In these constructs, the branching unit is represented by trisphenylamine, and the solubilizing chains by N-9-heptadecanyl-substituted perylene diimides. The photophysical properties of the dendrimers have been studied by absorption, steady-state, and time-resolved emission spectroscopy and pump–probe transient absorption spectroscopy. Photoinduced charge-separated (CS) states are formed on the femtosecond timescale upon visible excitation. In particular, in D6, two different CS states can be formed, involving different subunits that decays independently with different lifetimes (ca. 10–100 ps).

We report utilization of graphitic carbon nitride (g-CN) as an electrocatalyst for dye-sensitized solar cells (DSSCs). Crystalline poly(triazine imide) based g-CN was synthesized via a modified ionothermal method, and deposited onto the counter electrodes along with a conductive additive and a sacrificial polymer binder. The resulting DSSCs exhibited a power conversion efficiency (7.8%) comparable to that of conventional Pt catalyst (7.9%), confirming the excellent catalytic activity of poly(triazine imide) g-CN as a non-precious metal electrocatalyst.

Cells use three main ways of generating energy currency to drive metabolism: (i) conversion of adenosine diphosphate (ADP) to adenosine triphosphate (ATP) by the proton motive force through the rotor-stator ATP synthase; (ii) the synthesis of inorganic phosphate∼phosphate bonds via proton (or sodium) pyrophosphate synthase; or (iii) substrate-level phosphorylation through the direct donation from an active phosphoryl donor. A mechanism to produce a pyrophosphate bond as “energy currency” in prebiotic systems is one of the most important considerations for origin of life research. Baltscheffsky (1996) suggests that inorganic pyrophosphate (P_2O_7^(4-); PP_i) may have preceded ATP/ADP as an energy storage molecule in earliest life, produced by an H^+ pyrophosphatase. Here we test the hypothesis that PP_i could be synthesized in inorganic precipitates simulating hydrothermal chimney structures transected by thermal and/or ionic gradients. Appreciable yields of PP_i were obtained via substrate phosphorylation by acetyl phosphate within the iron sulfide/silicate precipitates at temperatures expected for an alkaline hydrothermal system.

An acetylcholinesterase-immobilized sensor unit was successfully prepared by encapsulating the enzyme within hybrid mesoporous silica membranes (F127-MST). Through a novel combination with tetracyanoquinodimethane, both acetylcholine and organophosphorus pesticides were successfully detected with high sensitivity. Furthermore, we manufactured the working prototype of an enzyme sensor with this sensor unit for detecting dichlorvos, aldicarb and parathion. At present, the detection limit in this working prototype either equaled or surpassed that of others. Also, we have the advantage of increased stability of the enzyme against the outer environment by encapsulation of the enzymes into a silica nanospace. Consequently, acetylcholinesterase immobilized in F127-MST is a practical sensor with high sensitivity, reusability, and storage stability.

Because of microbial resistance to conventional antibiotics, there is increasing interest in silver, including silver nanoparticles (nano-Ag), in antimicrobial applications. However, questions remain regarding the relative roles of nano-Ag particles, versus Ag(+) ions released from nano-Ag dissolution, in imparting bacterial toxicity. Here, we developed a novel nano-Ag that, based on its cysteine cap, was expected to dissolve slowly and thus potentially allow for differentiating nanoparticle, versus ionic, effects of Ag. The nano-Ag was systematically tested for its differential toxicity to Escherichia coli and Pseudomonas aeruginosa. Bacterial growth, reactive oxygen species (ROS) generation, particle dissolution, cellular electron transfer activity, and cell membrane damage and potential were evaluated. In minimal growth medium, E. coli and P. aeruginosa growth were slowed at 100 mg L(-1) (0.93 mM) and 5 mg L(-1) (0.046 mM), respectively; P. aeruginosa was completely inhibited at and above 10 mg L(-1) (0.093 mM). For both strains, toxicity was associated with ROS and cell membrane damage. Based on comparisons to AgNO3 exposures, toxicity from nano-Ag was due to Ag(+) ions and not intact nano-Ag, even though nanoparticle dissolution was less than 2% in minimal growth medium. Because of their stability and slow Ag(+) ion release, the cysteine-capped nano-Ag particles here are useful to antimicrobial applications. Additionally, our systematic approach to evaluating toxicity, membrane damage, and ROS generation can be applied with other nanomaterials and bacteria.

We present a rapid microwave-assisted sol-gel approach to Pd-substituted LnFeO3 (Ln = Y, La) for applications in C-C coupling reactions. These materials could be prepared in household microwave ovens in less than 15 minutes of reaction time with the final materials displaying well-defined structure and morphology. Phase evolution was studied using time-dependent microwave heatings and then compared with the results obtained from thermogravimetric analyses. Materials were confirmed to be phase pure by laboratory and synchrotron X-ray diffraction. Substituted Pd is ionic as shown by the binding energy shift from X-ray photoelectron spectroscopy. The short heating periods required for phase purity allow these materials less time for sintering as compared to conventional solid state preparation methods, making relatively high surface areas achievable. These materials have been successfully used as catalyst precursor materials for C-C coupling reactions in which the active species is Pd(0). Pd-substituted LnFeO3 (Ln = Y, La) provides Pd(0) in solution which can be complexed by the ligand SPhos, allowing for aryl chloride coupling.

We report a method for preparing p-type silicon germanium bulk alloys directly from a boron-doped silica germania nanocomposite. This is the first successful attempt to produce and characterize the thermoelectric properties of SiGe-based thermoelectric materials prepared at temperatures below the alloy's melting point through a magnesiothermic reduction of the silica-germania nanocomposite. We observe a thermoelectric power factor that is competitive with the literature record obtained for high energy ball milled nanocomposites. The large grain size in our hot pressed samples limits the thermoelectric figure of merit to 0.5 at 800 C for an optimally doped Si80Ge20 alloy. © 2013 American Chemical Society.

Short-chain polyphosphate (polyP) is released from platelets upon platelet activation, but it is not clear if it contributes to thrombosis. PolyP has increased propensity to clot blood with increased polymer length and when localized onto particles, but it is unknown whether spatial localization of short-chain polyP can accelerate clotting of flowing blood. Here, numerical simulations predicted the effect of localization of polyP on clotting under flow, and this was tested in vitro using microfluidics. Synthetic polyP was more effective at triggering clotting of flowing blood plasma when localized on a surface than when solubilized in solution or when localized as nanoparticles, accelerating clotting at 10–200 fold lower concentrations, particularly at low to sub-physiological shear rates typical of where thrombosis occurs in large veins or valves. Thus, sub-micromolar concentrations of short-chain polyP can accelerate clotting of flowing blood plasma under flow at low to sub-physiological shear rates. However, a physiological mechanism for the localization of polyP to platelet or vascular surfaces remains unknown.

Graphitic carbon nitride (g-CN) is a promising heterogeneous metal-free catalyst for organic photosynthesis, solar energy conversion, and photodegradation of pollutants. Its catalytic performance is easily adjustable by modifying texture, optical, and electronic properties via nanocasting, doping, and copolymerization. However, simultaneous optimization has yet to be achieved. Here, a facile synthesis of mesoporous g-CN using molecular cooperative assembly between triazine molecules is reported. Flower-like, layered spherical aggregates of melamine cyanuric acid complex (MCA) are formed by precipitation from equimolecular mixtures in dimethyl sulfoxide (DMSO). Thermal polycondensation of MCA under nitrogen at 550 °C produces mesoporous hollow spheres comprised of tri-s-triazine based g-CN nanosheets (MCA-CN) with the composition of C3N4.14H1.98. The layered structure succeeded from MCA induces stronger optical absorption, widens the bandgap by 0.16 eV, and increases the lifetime of photoexcited charge carriers by twice compared to that of the bulk g-CN, while the chemical structure remains similar to that of the bulk g-CN. As a result of these simultaneous modifications, the photodegradation kinetics of rhodamine B on the catalyst surface can be improved by 10 times.

Methyl bromide is used as feed in a process that converts it to gasoline. It is prepared by the gas-phase reaction of CH4 with Br2, a reaction that produces, besides the desired CH3Br, large amounts of CH2Br2. The latter cokes the catalyst used for gasoline production. The separation of CH2Br2 by distillation makes gasoline production too expensive. It is therefore important to increase the selectivity of the bromination reaction. We show that a small amount of I 2 catalyzes the reaction CH2Br2 + CH 4 → 2CH3Br, which leads to higher CH4 conversion and higher selectivity to CH3Br. These findings are promising for developing a low-cost integrated bromine-iodine based dual-halogen pathway to convert stranded natural gas into fuels and chemicals. © 2013 American Chemical Society.

Highly ordered mesoporous crystalline MoSe2 is synthesized using mesoporous silica SBA-15 as a hard template via a nanocasting strategy. Selenium powder and phosphomolybdic acid (H3PMo12O40) are used as Se and Mo sources, respectively. The obtained products have a highly ordered hexagonal mesostructure and a rod-like particle morphology, analogous to the mother template SBA-15. The UV-vis-NIR spectrum of the material shows a strong light absorption throughout the entire visible wavelength region. The direct bandgap is estimated to be 1.37 eV. The high surface area MoSe2 mesostructure shows remarkable photocatalytic activity for the degradation of rhodamine B, a model organic dye, in aqueous solution under visible light irradiation. In addition, the synthesized mesoporous MoSe2 possess a reversible lithium storage capacity of 630 mAh g1 for at least 35 cycles without any notable decrease. The rate performance of mesoporous MoSe2 is much better than that of analogously synthesized mesoporous MoS2, making it a promising anode for the lithium ion battery.

The dependence of electrooxidation on experimental conditions of organic molecules was investigated to optimize the production of hydrogen from potential wastewater sources using low voltage sources (∼1 V dc). Electrooxidation on platinum, gold, and stainless steel anodes with hydrogen production on the cathode was investigated using several different organic reductants, including: methanol, ethanol, glycerol, isopropanol, propanal, glycerol, glucose, sucrose, citric acid, and propionic acid. The electrolyte pH was varied from 2 to 12 in a 1 M Na2SO4 supporting solution. At 1 V, glycerol, citric acid, ethanol and methanol were found to yield the highest currents at low pH values (pH 2 and 7) on platinum electrode, glucose on gold electrode at pH 12 in 1 M Na2SO4 solution produced the highest total current density at 1 V with measured Faradaic efficiency for 1 M glucose of 70%. The hydrogen energy production efficiency was 86%. Practical limitations of glucose oxidation at optimum experimental conditions are discussed. Highlights: We determined optimal conditions for organic wastewater electrooxidation at 1 V. 3 mA/cm2 current density for glucose on Au electrode at 0.5 M and pH 13 obtained. Faradaic efficiency of H2 production was ∼70% for glucose on the Au electrode. These experiments are an alternative to the conventional water photoelectrolysis.

In this manuscript, a novel strategy for the therapeutic delivery of nitric oxide to physiological targets is described. Nitric oxide (NO) is a key vasodilator in mammalian cardiovascular systems and has been shown to sensitize tissue to γ -radiation. However, photochemical NO precursors that can be activated by these near-infrared (NIR) wavelengths are extremely limited. Herein, we have addressed this issue by utilizing the known NIR to visible upconversion properties of lanthanide cations doped NaYF 4 nanocrystals. This result is a potential game changer in multiphoton excitation based therapeutic delivery of NO and other small molecule bioregulators. The bioregulatory molecule nitric oxide (NO) plays important roles in cancer biology and has been implicated in both tumor growth and suppression. [ 1 ] Furthermore, NO is a γ -radiation sensitizer that can enhance selective killing of neoplastic tissues. For these reasons, there is considerable interest in developing methods for NO delivery to specifi c physiological targets. In this context, several laboratories have explored photoactivated NO delivery to specifi c tissues upon demand. [ 2‐7 ] A key advantage of photochemical triggering

A mesoporous Bi_2Te_3 monolith with ≈20% porosity is fabricated by hot-pressing mesoporous powders. The mesostructures are able to transport carriers and scatter phonons efficiently. The reduction (≈60%) of the thermal conductivity is sufficient to compensate for the loss of electrical conductivity perpendicular to the direction of applied pressure, leading to an enhanced zT of 0.7, highest among all reported self-doped, n-type Bi_2Te_3 at similar temperatures.

Propane oxidative dehydrogenation is a promising candidate for on-purpose propylene production. However, in oxidative dehydrogenation the propylene yield is limited by the simultaneous oxidization of propane to multiple oxygenated byproducts. We show that a small amount of I2 is highly effective in catalyzing the dehydrogenation of propane into propylene, using dibromomethane (DBM), a byproduct of the activation of methane by bromine, as the oxidant. Single-pass “C3H6+C3H7X” (X = Br, I; C3H7X can be easily converted to C3H6 and HX) yields of up to 80% can be easily achieved, with the highly selective conversion of DBM to methyl bromide, which is readily converted into either high-market-value petrochemicals or liquid fuels. Bearing in mind that the formation of DBM is one of the major undesirable byproducts in the bromine-mediated gas-to-liquid technology, our findings create a win-win situation. On the one hand, this approach is promising for developing a low-cost, on-purpose propylene technology using n...

CH3Br, like CH3OH in the Methanol-To-Gasoline process, can be readily directly converted to petrochemicals and liquid fuels. CH3Br can be obtained in high yields by the direct bromination of methane using relatively low reaction temperatures and pressure, but with the formation of dibromomethane (DBM) as a primary side product. Here, we report that DBM can be highly selectively converted to higher hydrocarbons and methyl bromide via a catalytic hydrodebromination process. Silica-supported palladium carbide shows a high selectivity for the conversion of DBM to higher hydrocarbons, mainly light olefins. Silica-supported ruthenium has a high selectivity for the conversion of DBM to methyl bromide, which can then be converted to fuels or light olefins. These reactions offer pathways to increase the overall useful product yield of the methane bromination reaction, thus taking an important step toward the potential industrial application of bromine mediated Gas-To-Liquid technology.

Ultrafine MoO2 nanorods with a diameter of ∼5 nm were successfully synthesized by a nanocasting method using mesoporous silica SBA-15 as hard template. This material demonstrates high reversible capacity, excellent cycling performance, and good rate capacity as an anode electrode material for Li ion batteries. The significant enhancement in the electrochemical Li storage performance in ultrafine MoO2 nanorods is attributed to the nanorod structure with small diameter and efficient one-dimensional electron transport pathways. Moreover, density functional theory calculations were performed to elucidate the Li uptake/removal mechanism in the MoO2 electrodes, which can help us understand the unique cycling behavior of MoO2 material.

Chemical gardens form when ferrous chloride hydrate seed crystals are added or concentrated solutions are injected into solutions of sodium silicate and potassium phosphate. Various precipitation morphologies are observed depending on silicate and phosphate concentrations, including hollow plumes, bulbs, and tubes. The growth of precipitates is controlled by the internal osmotic pressure, fluid buoyancy, and membrane strength. Additionally, rapid bubble-led growth is observed when silicate concentrations are high. ESEM/EDX analysis confirms compositional gradients within the membranes, and voltage measurements across the membranes during growth show a final potential of around 150-200 mV, indicating that electrochemical gradients are maintained across the membranes as growth proceeds. The characterization of chemical gardens formed with iron, silicate, and phosphate, three important components of an early earth prebiotic hydrothermal system, can help us understand the properties of analogous structures that likely formed at submarine alkaline hydrothermal vents in the Hadean-structures offering themselves as the hatchery of life.

We have studied catalytic activity of Pt-doped CeO2 for the oxidation and the dry reforming of methane. The catalyst was prepared by three methods resulting in ceria containing different ratios of ionic Pt versus Pt0. We show that these materials have different catalytic activity for methane oxidation and dry reforming and that they are more active when the fraction of ionic Pt is increased. Density functional theory was used to help understand the role of Pt dopant. It was found that the presence of Pt activates the oxygen atoms next to it in the surface layer and this decreases the activation energy for dissociative adsorption of methane (which is the rate-limiting step in the reaction).

In this work, we report a facile solution-phase synthesis of hollow cubic phase α-NaYF4 nanoparticles by a controlled ion exchange process from cubic phase Y2O3 nanospheres. We demonstrate that hol...

We present a simple, solution-based synthetic route to hollow cerium oxide spheres. Thin layers (∼12 nm) of cerium oxide are deposited onto ∼200 nm silica colloids using cerium nitrate and the silica cores are subsequently removed to yield hollow spheres. The spheres are composed of ∼4 nm ceria nanocrystals. Nitrogen adsorption isotherms indicate that the spheres are microporous with pore sizes of approximately 10 A. The spheres are thermally stable to collapse and ripening up to 700 °C and are active for the catalytic combustion of carbons. The hollow ceria spheres developed in this work are attractive as building blocks for multicomponent catalysts.

The electrocatalytic activity of gold-platinum (Au-Pt) clusters was investigated in acidic and alkaline electrolytes. The clusters were synthesized by electrodeposition on fluorinated tin oxide (FTO) substrates and carbon disks with dimensions from 50 to 200 nm. Methanol electrooxidation (fuel cell anode) and oxygen electroreduction (fuel cell cathode) activities were measured using cyclic voltammetry and chronoamperometry. The results for methanol electrooxidation showed that platinum could be partially substituted by gold to achieve higher resistance to poisoning without affecting the activity in acid electrolyte, while in alkaline environment, a significant overall improvement in performance was observed. On the other hand, for the oxygen electroreduction, kinetic results obtained using a rotating disk electrode (RDE) indicated that Au alloying with Pt does not significantly alter the catalytic activity in acidic electrolyte, while a significant improvement in activity was observed in an alkaline electrolyte, which is attributed to a synergistic effect between the Au and Pt.

Electrostatic interactions between the imidazole-based cationic homopolymer, polyvinylimidazole (PVIm), and anionic polysaccharide, sodium alginate, lead to the formation of colloidal aggregates known as complex coacervates in the pH range 4–6.5. PVIm was labeled with the fluorescent reporter pyrene to investigate the coacervation-induced changes in and around PVIm chains. While the pyrene-tagged PVIm had blue fluorescence in water, the coacervate phase exhibited an additional broad band around 492 nm (green) due to formation of pyrene excimers. Fluorescence spectroscopic investigations point toward aggregation of PVIm chains and desolvation upon coacervation. Highly anisotropic fluorescence emission indicates tight packing of the polymer chains in the coacervate. Confocal microscopy of fluorescein-labeled alginate and rhodamine-labeled PVIm shows coacervates as dense aggregates with uniform distribution of the polymers. Fluorescence spectroscopy offers sensitive and easy investigation into polyelectrolyte interactions.

Free-standing and supported films with a lateral gradient in composition were prepared using blends of poly(acrylic acid) (PAA)/sodium salt and its copolymers with acrylamide (AAm) in an applied electric field. The gradients were stabilized by complexation of carboxylate groups with metal species. To find the favorable conditions and components for successful blending and interaction with Fe and Ce species, we studied blending of the two PAA samples with molecular weights of 2000 and 15 000 Da with two copolymers of AA and AAm (with 10 and 70 wt % of AA units) and interaction of these blends with Fe(III) and Ce(IV) ions. The structure of the hybrid (blend) films was studied using differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, X-ray diffraction, and optical microscopy. To ensure blend miscibility and efficient interaction with metal ions, the copolymer containing 70 wt % AA units has been used. The surface enrichment with metal species was observed at all experimental conditions studied in this work. For lateral gradient film formation, 15 000 Da PAA has been used to avoid uneven distribution of the homopolymer in the film, observed for 2000 Da PAA. The gradient films were characterized by XPS. The lateral gradient of functionality such as COONa group or Fe content has been obtained at different strengths of electric field applied during film formation. The use of lower voltage allows one to prevent NaOH formation and creates more favorable conditions for development of a gradient polymer film. The Ce content gradient was not observed due to formation of large Ce oxide particles (or = 750 nm), masking the gradient of functionality. For the first time, free-standing films with a lateral gradient in composition were prepared using an applied electric field.

Multifunctional mesostructured silica microspheres are prepared using ultrasonic aerosol spray in conjunction with solvent evaporation-induced assembly. Rare earth ion-phenanthroline complexes, magnetite particles, photoacid generators, and pH-sensitive dyes are chosen as luminescent, magnetic, and photosensitive components. The incorporation of these functional components into mesostructured silica microspheres can be readily realized by dispersing them in the precursor solution of the aerosol spray process. Luminescent microspheres that can emit at multiple wavelengths when excited at a single wavelength are produced by the addition of multiple rare earth complexes into the precursor solution. The addition of magnetite particles leads to the production of magnetic luminescent microspheres. Photoacid generators and pH-sensitive dyes are further employed to produce magnetic photosensitive microspheres that can release acid and change color upon UV light illumination. Such multifunctional microspheres could have exciting potential for many optical and biotechnological applications, such as multiplexed labeling, diagnosis, simultaneous imaging and therapy, cell capture and separation, targeted delivery, and optical data storage.

Several naturally occurring biomacromolecular structures, particularly those containing histidine-rich proteins, have been shown to depend on metal ion complexation for hardness and stiffness. In this study, water-soluble metal-binding polymers and copolymers based on vinylimidazole were utilized to mimic the glycine- and histidine-rich proteins of ragworm jaws. Blends of these polymers with agarose exhibited a significant capacity for Zn(II) and Cu(II) complexation. Rheological and uniaxial tensile tests as well as nanoindentational analysis of the blends revealed a more than 10-fold improvement in the tensile strength, along with increases in the hardness of the dried samples, upon metal ion addition. Pronounced differences in mechanical effects, however, were associated with Cu(II) and Zn(II) complexation, and the latter provided much better overall mechanical performance.

We developed a simple sol−gel chemistry-based opal infiltration method for the fabrication of high-quality planar titania photonic crystals. Polystyrene synthetic opals were infiltrated with a hydrophobic and air/moisture-stable liquid titania precursor. The high stability and hydrophobicity of the titania precursor enabled a new “lift-off/turn-over” backfilling technique that after calcination gives planar titania inverse opals with a flat and completely open surface, without the need for additional processing steps to remove any excess surface coating of the backfilling material. We also compare two different infiltration strategies and their influence on the structural and photonic properties. The obtained inverse opals display excellent photonic properties as evidenced by the presence of first-, second-, and third-order Bragg reflection peaks in accordance with theoretical photonic band structure calculations.

We report a novel strategy for writing volume holograms by photoacid generation and subsequent acid-catalyzed degradation leading to increased free volume/refractive index modulation in the exposed regions of a cross-linked rigid polymeric matrix. This strategy offers nondestructive read out and high diffraction efficiency and allows optical-quality, millimeter thick films to be fabricated that possess excellent thermal and dimensional stability. A key feature of this approach is the efficient acid-catalyzed degradation of functional groups in the cross-linked matrix leading to release of volatile products which diffuse readily out of the thick films. Furthermore, the reported data storage material is lightweight and inexpensive and can be easily processed into different shapes, making it an attractive candidate for data storage applications.

Developing electrode materials with high-energy densities is important for the development of lithium-ion batteries. Here, we demonstrate a mesoporous molybdenum dioxide material with abnormal lithium-storage sites, which exhibits a discharge capacity of 1,814 mAh g−1 for the first cycle, more than twice its theoretical value, and maintains its initial capacity after 50 cycles. Contrary to previous reports, we find that a mechanism for the high and reversible lithium-storage capacity of the mesoporous molybdenum dioxide electrode is not based on a conversion reaction. Insight into the electrochemical results, obtained by in situ X-ray absorption, scanning transmission electron microscopy analysis combined with electron energy loss spectroscopy and computational modelling indicates that the nanoscale pore engineering of this transition metal oxide enables an unexpected electrochemical mass storage reaction mechanism, and may provide a strategy for the design of cation storage materials for battery systems., Electrode materials with high energy density are important for the development of Li-ion batteries. Here, the authors report a molybdenum dioxide anode with abnormal lithium storage sites, exhibiting a discharge capacity twice its theoretical value by utilizing two different storage mechanisms.

The surface-plasmon properties of Au bipyramids are investigated using the finite-difference time-domain method. It is found that both the extinction cross sections and local electric-field enhancements of Au bipyramids are larger than those of Au nanorods that have longitudinal surface plasmon (LSP) wavelengths close to those of Au bipyramids. Following this result the growth of Au bipyramids using cationic surfactants of variously sized headgroups as stabilizing agents is carried out. It is found that the growth using cetyltributylammonium bromide (CTBAB) produces Au bipyramids with tunable LSP wavelengths in high yields. The oxidation behaviour of Au bipyramids using hydrogen peroxide as the oxidizing agent is fully explored and the oxidation is found to occur preferentially at highly curved surface sites. It is further demonstrated that the oxidation rate can be controlled by varying the amounts of hydrogen peroxide and hydrochloric acid. This oxidation approach can be used in conjunction with the seed-mediated growth in CTBAB solutions to produce Au bipyramids, the LSP wavelengths of which are finely tunable from 650 to 1300 nm.

Mesostructured non-silicate oxides, with well-defined organization on the 2–50 nm size scale, may play a pivotal role in advancing vital disciplines such as catalysis, energy conversion, and biotechnology. Herein, we present selected methodologies for utilizing the sol–gel process, in conjunction with organic-directed assembly, to synthesize a variety of mesostructured oxides. The nature of the inorganic precursor is critical for this process. We discuss the development of general routes for yielding stable, nanoscopic, hydrophilic, inorganic precursors compatible with organic co-assembly. In particular, we highlight the use and characterization of organic-acid-modified transition metal oxide sol–gel precursors that allow for the synthesis and processing of designer mesostructured oxides such as titania hybrids for optical applications and porous multicomponent metal oxides useful for catalysis.

Gold nanorods were prepared in high yields by using a one-step seed-mediated process in aqueous cetyltripropylammonium bromide (CTPAB) and cetyltributylammonium bromide (CTBAB) solutions in the presence of silver nitrate. The diameters of the nanorods range from 3 to 11 nm, their lengths are in the range of 15 to 350 nm, and their aspect ratios are in the range of 2 to 70. The diameters of the Au nanorods obtained from one growth batch in CTPAB solutions decrease as their lengths increase, and their volumes decrease as the aspect ratios increase. The diameters of the Au nanorods obtained from one growth batch in CTBAB solutions first decrease and then slightly increase as their lengths increase, and their volumes increase as the aspect ratios increase. These Au nanorods are single-crystalline and are seen to be oriented in either the [100] or [110] direction under transmission electron microscopy imaging, irrespective of their sizes. To the best of our knowledge, this is the first report of the preparation by using wet-chemistry methods of single-crystalline Au nanorods with aspect ratios larger than 15.

New fullerene derivatives, tri-cyanohydrofullerene, HC 60 (CN) 3 , and poly{4-[2-[2-(2-methoxyethoxy)ethoxy]ethoxy]benzyl}fullerene, C 60 (TEO) n , have been synthesized as additives for proton conducting membranes. The new compounds have been incorporated in Nafion ® to fabricate a composite by a newly developed solution cast method. The fullerene–Nafion ® membranes exhibited an excellent handling with no extensive phase separation. C 60 (TEO) n has also been found to be very effective in improving the dispersion of HC 60 (CN) 3 in the Nafion ® matrix. The fullerene composite membranes have demonstrated enhanced proton conductivity under low relative humidity conditions compared to a recast Nafion ® membrane. The membrane characterization was performed through optical microscopy, SEM, and water uptake measurements.

We have developed a facile procedure that can create asymmetrical building blocks by uniformly deforming nanospheres into C(∞v) symmetry at low cost and high quality. Concave polystyrene@carbon (PS@C) core-shell nanospheres were produced by a very simple microwave-assisted alcohol thermal treatment of spherical PS@C nanoparticles. The dimensions and ratio of the concave part can be precisely controlled by temperature and solvents. The concavity is created by varying the alcohol-thermal treatment to tune the swelling properties that lead to the mechanical deformation of the PS@C core-shell structure. The driving force is attributed to the significant volume increase that occurs upon polystyrene core swelling with the incorporation of solvent. We propose a mechanism adapted from published models for the depression of soft capsules. An extrapolation from this model predicts that the rigid shell is used to generate a cavity in the unbuckled shell, which is experimentally confirmed. This swelling and deformation route is flexible and should be applicable to other polymeric nanoparticles to produce asymmetrical nanoparticles.

Redox active electrode materials derived from organic precursors are of interest for use as alternative cathodes in Li batteries due to the potential for their sustainable production from renewable resources. Here, a series of organic networks that either contain triazine units or are derived from triazine-containing precursors are evaluated as cathodes versus Li metal anodes as possible active materials in Li batteries. The role of the molecular structure on the electrochemical performance is studied by comparing several materials prepared across a range of conditions allowing control over functionality and long-range order. Well-defined structures in which the triazine unit persists in the final material exhibit very low capacities at voltages relevant for cathode materials (

Defining the design principles guiding the fabrication of superior biocomposite structures from an assemblage of ordinary molecules is a key goal of biomimetics. Considering their low degree of mineralization, Glycera jaws have been shown to be extraordinarily resistant to abrasion based on the metric hardness3/Young's modulus2. The jaws also exhibit an impressive chemical inertness withstanding boiling concentrated hydrochloric acid as well as boiling concentrated sodium hydroxide. A major organic component largely responsible for the chemical inertness of the jaws has been characterized using a spectrophotometric assay for melanin content, 13C solid state nuclear magnetic resonance, IR spectroscopy, and laser desorption ionization-time of flight mass spectrometry and is identified here as a melanin-like network. Although melanin is widely distributed as a pigment in tissues and other structural biomaterials, to our knowledge, Glycera jaws represent the first known integument to exploit melanin as a cohesive load- and shape-bearing material.