Ordered PtPb/Pt Core/Shell Nanodisks as Highly Active,Selective, and Stable Catalysts for Methanol Reformation to H2

Herein, we report on unique bimetallic PtPb/Pt core/shell nanodisks consisting of structurally ordered PtPb hexagonal nanoplates as the core and the well‐organized Pt as the shell, as extremely active and selective catalysts towards CH₃OH reformation. We found that the created Pt‐Pb nanodisks/C show the composition‐dependent activity with the optimized PtPb_0.56 nanodisks/C being the most active for the CH₃OH reformation to H₂, 5.1 times higher than those of the commercial Pt/C. Significantly, only very limited carbon monoxide (CO) is produced during the CH₃OH reformation, which is crucial for the practical application in fuel cells. The PtPb_0.56 nanodisks/C is also more active for CH₃OH reformation than PtPb hexagonal nanoplates/C and PtPb_0.58 nanoparticles/C. X‐ray photoelectron spectroscopy (XPS) results reveal that the high ratio of Pt (0) to Pt (II) in Pt‐Pb nanodisks/C enhances the CH₃OH reformation to H₂, while the high content of Pb (0) is beneficial for decrease the CO production. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) of CO adsorption shows that Pt‐Pb nanodisks can promote the activation of CO molecules by forming the carboxylate (CO₂^δ?) intermediates, leading to the low CO production.     

Resonant Aluminum Nanodisk Array for Enhanced Tunable Broadband Light Trapping in Ultrathin Bulk Heterojunction Organic Photovoltaic Devices

A cost-effective approach to enhancing broadband light trapping in ultrathin bulk heterojunction organic photovoltaic (OPV) devices is proposed. This is achieved by simply inserting an array of Al nanodisks at the interface of the ITO anode and the organic active layer; forming circular plasmonic nanopatch cavities (between the nanodisks and the Al cathode) that sandwich the active layer. Through interactions between the surface plasmon polaritons localized at the nanodisk and the cathode, a tunable broadband resonance peak spanning 450?C700?nm in the scattering cross-section spectrum is formed, thereby enhancing the electromagnetic field in the active layer. Compared to an OPV device with a 60-nm-thick PCPDTBT/PC₆₀BM layer, our numerical simulations reveal that integrated absorption enhancements of up to 40?% can be achieved in an equivalent device integrated with an array of nanodisks with a diameter of 100?nm and a periodicity of 250?nm. From the analysis of the structure?Cperformance relationships, implications for the design of these nanopatch cavities for light harvesting in ultrathin OPV devices are discussed.     

Coupling of Whispering-Gallery Modes in the Graphene Nanodisk Plasmonic Dimers

In this paper, we proposed plasmonic dimers consisted of two evanescent field coupled graphene monolayer nanodisks. The electromagnetic properties including the split modes with non-degenerate wavelengths, enhancement of the quality factors (Q factors) and mode areas, and the coupling between the fundamental and the first-order whispering-gallery modes are numerically predicted and analyzed systematically. Compared with the single graphene nanodisk, the Q factor of TM_4,1 reaches 356 in a dimer with a radius of 5 nm of each nanodisk and an inter-disk gap of 0.4 nm, where the corresponding mode area is as small as 6.88?×?10^‐?5(λ ₀)². In addition, the enhanced performances of size-mismatched coupled graphene plasmonic dimers are investigated. This graphene monolayer plasmonic dimer could be one of the fundamental components in the future ultra-high density plasmonic circuit technique, on-chip plasmonic interconnect, and transformation plasmonics. It also could be used as the test-beds for added explorations of cavity quantum electrodynamic experiments.     

Apolipoprotein-induced conversion of phosphatidylcholine bilayer vesicles into nanodisks

Apolipoprotein mediated formation of nanodisks was studied in detail using apolipophorin III (apoLp-III), thereby providing insight in apolipoprotein-lipid binding interactions. The spontaneous solubilization of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) vesicles occured only in a very narrow temperature range at the gel-liquid-crystalline phase transition temperature, exhibiting a net exothermic interaction based on isothermal titration calorimetry analysis. The resulting nanodisks were protected from proteolysis by trypsin, endoproteinase Glu-C, chymotrypsin and elastase. DMPC solubilization and the simultaneous formation of nanodisks were promoted by increasing the vesicle diameter, protein to lipid ratio and concentration. Inclusion of cholesterol in DMPC dramatically enhanced the rate of nanodisk formation, presumably by stabilization of lattice defects which form the main insertion sites for apolipoprotein α-helices. The presence of fully saturated acyl chains with a length of 13 or 14 carbons in phosphatidylcholine allowed the spontaneous vesicle solubilization upon apolipoprotein addition. Nanodisks with C13:0-phosphatidylcholine were significantly smaller with a diameter of 11.7 ± 3.1nm compared to 18.5 ± 5.6 nm for DMPC nanodisks determined by transmission electron microscopy. Nanodisk formation was not observed when the phosphatidylcholine vesicles contained acyl chains of 15 or 16 carbons. However, using very high concentrations of lipid and protein (>10mg/ml), 1,2,-dipalmitoyl-sn-glycero-3-phosphocholine nanodisks could be produced spontaneously although the efficiency remained low.     

Thick filaments in vascular smooth muscle

Two sets of myofilaments were demonstrated after incubation of strips of rabbit portal-anterior mesenteric vein under moderate stretch in a physiological salt solution. Thick filaments had a mean diameter of 18 nm and reached a maximum length of 1.4 µm with a mean length of 0.61 µm. In transverse sections, 2.5–5 nm particles were resolved as subunits of the thick filaments. Thin filaments had an average diameter of 8.4 nm and generally conformed to the structure believed to represent actin filaments in smooth and striated muscles. In the areas of maximum concentration there were 160–328 thick filaments/µm² and the lowest ratio of thin to thick filaments was 12:1. Thick filaments were present in approximately equal numbers in vascular smooth muscle relaxed by theophylline, in Ca⁺⁺-free solution, or contracted by norepinephrine. The same preparatory procedures used with vascular smooth muscle also enabled us to visualize thick filaments in guinea pig and rabbit taenia coli and vas deferens.     

The structural peculiarities of condensed DNA micro- and nanoparticles formed in PCR

Studies of DNA condensation have opened new perspectives in biotechnology and medicine. DNA condensation induced by polyamines or trivalent metal ions in vitro at room temperature has been investigated in detail. Our recent studies have demonstrated Mg²⁺-mediated formation of DNA condensates during the PCR. In this study, we report the unique morphology and fine structure of PCR-generated condensed DNA particles using electron and atomic force microscopy. The principal morphologies of studied DNA condensates are 3D particles of micrometer dimensions, oval microdisks of nanometer thickness, filaments, and compact nano-sized particles. SEM examinations have revealed a new structural type of spherical and elliptical 3D microparticles formed by numerous definitely oriented microdisks and their segments. AFM revealed a granular structure of the microdisk surface and the smallest nano-sized disks and thinnest nanofibrils – that appear to be the primary products of DNA condensation during the PCR. We suggest that the formation of DNA nanofibrils and nanodisks in PCR occurs due to Mg²⁺ – mediated intermolecular (lateral) and intramolecular condensation of ssDNA. Aggregation of elementary nanodisks in the course of thermal PCR cycles, occurring both by magnesium cations and via complementary interactions, give a rise to large nano-sized aggregates and more complex microparticles.     

Charge‐Carrier Mobility Requirements for Bulk Heterojunction Solar Cells with High Fill Factor and External Quantum Efficiency >90%

To increase the efficiency of bulk heterojunction (BHJ) solar cells beyond 15%, 300 nm thick devices with 0.8 fill factor (FF) and external quantum efficiency (EQE) >90% are likely needed. This work demonstrates that numerical device simulators are a powerful tool for investigating charge‐carrier transport in BHJ devices and are useful for rapidly determining what semiconductor pro­perties are needed to reach these performance milestones. The electron and hole mobility in a BHJ must be ≈10^?2 cm² V^?1 s^?1 in order to attain a 0.8 FF in a 300 nm thick device with the recombination rate constant of poly(3‐hexyl­thiophene):[6,6]‐phenyl‐C61‐butyric acid methyl ester (P3HT:PCBM). Thus, the hole mobility of donor polymers needs to increase from ≈10^?4 to ≈10^?2 cm² V^?1 s^?1 in order to significantly improve device performance. Furthermore, the charge‐carrier mobility required for high FF is directly proportional to the BHJ recombination rate constant, which demonstrates that decreasing the recombination rate constant could dramatically improve the efficiency of optically thick devices. These findings suggest that researchers should prioritize improving charge‐carrier mobility when synthesizing new materials for BHJ solar cells and highlight that they should aim to understand what factors affect the recombination rate constant in these devices.     

Analysis and Simulation of a Novel Localized Surface Plasmonic Highly Sensitive Refractive Index Sensor

Dividing a metal nanoparticle into smaller components and the occurrence of the plasmonic phenomenon in the gap between these components can improve the sensitivity of the detector to variation of the refraction coefficient of liquid. In this paper, in a constant volume of metal, a golden disk is divided into two rings and one smaller disk. With a proper arrangement of these components, the surface plasmon resonance phenomenon takes place at the wavelength of 945.7 nm. The occurrence of this phenomenon increases the field in the distance between nanoparticles surrounded by liquid. The sensitivity of the detector that designed using nanodisks is 300 nm/RIU while it increases to 500 nm/RIU for the new structure. The increase of LSPR displacement, for a variation of 0.01 in the liquid refraction coefficient, from 3 nm for a disk to 5 nm for a proposed structure verifies a 67% improvement in the sensitivity of the sensor.

     

Reduced cross-bridge dependent stiffness of skinned myocardium from mice lacking cardiac myosin binding protein-C

The role of cardiac myosin binding protein-C (MyBP-C) on myocardial stiffness was examined in skinned papillary muscles of wild-type (WT^+/+) and homozygous truncated cardiac MyBP-C (MyBP-C^t/t) male mice. No MyBP-C was detected by gel electrophoresis or by Western blots in the MyBP-C^t/t myocardium. Rigor-bridge dependent myofilament stiffness, i.e., rigor minus relaxed stiffness, in the MyBP-C^t/t myocardium (281 ± 44 kN/m²) was 44% that in WT^+/+ (633 ± 141 kN/m²). The center-to-center spacing between thick filaments as determined by X-ray diffraction in MyBP-C^t/t (45.0 ± 1.2 nm) was not significantly different from that in WT^+/+ (43.2 ± 0.9 nm). The fraction of cross-sectional area comprised of myofibrils, as determined by electron microscopy, was reduced in the MyBP-C^t/t (39.9%) by 10% compared to WT^+/+ (44.5%). These data suggest that the 56% reduction in rigor-bridge dependent stiffness of the skinned MyBP-C^t/t myocardium could not be due solely to a 10% reduction in the number of thick filaments per cross-sectional area and must also be due to approximately 50% reduction in the stiffness of the rigor-bridge attached thick filaments lacking MyBP-C. (Mol Cell Biochem 263: 73–80, 2004)     

Structure of multinucleated smooth muscle cells of the ascidian Halocynthia roretzi

Summary Cells isolated from ascidian smooth muscle were about 1.5–2 mm in length. Each contained 20–40 nucle in proportion to cell length. The cytoplasm was characterized by the presence of an enormous quantity of glycogen particles, tubular elements of sarcoplasmic reticulum coupled to the cell membrane, and conspicuous contractile elements. Thick and thin filaments had diameters of about 14–16 nm and 6–7 nm, respectively. The population density of the thick filaments was much higher (mean 270/m² filament area) than in vertebrate smooth muscles. The ratio of thick to thin filaments was about 16. All the thick filaments were surrounded by a single row of 5–9 thin filaments forming a rosette, and cross-bridges with periodicities of 14.5 and 29 nm were found between them. The contractile apparatus consisted of numerous myofibrils which were arranged nearly along the cell axis and were separated from each other by a network of 10-nm filaments. The myofibrils further consisted of many irregularly arranged sarcomerelike structures, each of which was comprised of a small group of thick and thin filaments with attached dense bodies.     

The occurrence of pili associated with a plasmid of the W compatibility group

Using electron microscopy, it was found that the acquisition of the W group drug resistance plasmid S-a by normally pilusless bacterial strains was associated with the appearance of pili. The loss of drug resistance markers in presumed R^? revertants was accompanied by a loss of pili. The numbers of pili present on transconjugant strains of the three bacterial species tested were 3.2 pili/cell for $\text{Salmonella typhimurium}$, and 0.19 pili/cell for both $\text{Escherichia coli}$ and $\text{Pseudomonas aeruginosa}$. Negatively stained pili were about 12 nm thick and varied in length from 23 nm to 3,370 nm.     

The structure of isolated cardiac Myosin thick filaments from cardiac Myosin binding protein-C knockout mice

Mutations in the thick filament associated protein cardiac myosin binding protein-C (cMyBP-C) are a major cause of familial hypertrophic cardiomyopathy. Although cMyBP-C is thought to play both a structural and a regulatory role in the contraction of cardiac muscle, detailed information about the role of this protein in stability of the thick filament and maintenance of the ordered helical arrangement of the myosin cross-bridges is limited. To address these questions, the structure of myosin thick filaments isolated from the hearts of wild-type mice containing cMyBP-C (cMyBP-C^+/+) were compared to those of cMyBP-C knockout mice lacking this protein (cMyBp-C^−/−). The filaments from the knockout mice hearts lacking cMyBP-C are stable and similar in length and appearance to filaments from the wild-type mice hearts containing cMyBP-C. Both wild-type and many of the cMyBP-C^−/− filaments display a distinct 43 nm periodicity. Fourier transforms of electron microscope images typically show helical layer lines to the sixth layer line, confirming the well-ordered arrangement of the cross-bridges in both sets of filaments. However, the “forbidden” meridional reflections, thought to derive from a perturbation from helical symmetry in the wild-type filament, are weaker or absent in the transforms of the cMyBP-C^−/− myocardial thick filaments. In addition, the cross-bridge array in the absence of cMyBP-C appears more easily disordered.     

Magnetic lipase adsorbed to a magnetic fluid

A magnetic fluid was synthesized by oxidation of ferrous ions (Fe^2&+) in the presence of a synthetic alternating copolymer of polyethylene glycol (PEG) and maleic acid (MA), poly(PEG-MA). The magnetic fluid dispersed stably both in aqueous solution and in organic solvents. Its particle size was approximately 10 nm. The magnetic fluid was mixed with lipase in water, followed by lyophilization. Although the enzyme and the magnetic fluid were dissociated in aqueous solution, they remained associated in organic solvents such as benzene. The magnetic fluid-adsorbed lipase dispersed in benzene and exerted high enzymic activity (2.9 μmol min⁻¹ mg⁻¹ lyophilized powder) for lauryl laurate synthesis from lauric acid and lauryl alcohol, and was readily recovered from the reaction mixture in a magnetic field (6000 Oe) without loss of enzymic activity.     

A Three-Dimensional Plasmonic Nanostructure with Extraordinary Optical Transmission

We report a 3D plasmonic nanostructure having an extraordinary optical transmission due to localized surface plasmon (LSP) coupling between nanoholes and nanodisks. The nanostructure contains a free-standing gold nanohole array (NHA) film above a cavity and an array of nanodisks at the bottom of the cavity that is aligned with the NHA. For the device, the LSP-mediated resonance position was dependent on the hole and nanodisk diameter as well as the separation distance. Also, the effect of LSP coupling between each hole and corresponding nanodisk became negligible for cavities deeper than 200 nm as observed as a disappearance of the LSP resonance. The greatest LSP resonance transmission and the highest electric field intensity were observed for the structure with the shallowest cavity. In addition, the structure had high surface plasmon resonance sensitivity and may have potential for surface-enhanced Raman spectroscopy and optical trapping applications.     

Intercellular fibrillar skeleton in the basal interdigitations of kidney tubular cells

Summary The tubular cells from the thick ascending limb of the loop of Henle in rabbit kidney medulla contain in their basallateral surfaces a complex system of interdigitations. Within these interdigitations, the plasma membranes are separated by extracellular spaces of relatively constant width that contain a previously undescribed fibrillar system. The structural organization and distribution of this intercellular fibrillar skeleton was studied using freeze-fracture etch and then section electron microscopy. The skeleton is comprised of discrete strands with a density of 300 to 400 per m² evenly distributed along the entire basal-lateral region. Each strand has the shape of a brace and it is constructed from up to eight finer filaments each having a width of about 2 nm. The filaments are tightly joined together along their shafts for about 30 nm but they separate at both ends for about 10 nm before contacting the external surface of the plasma membrane. We propose that this intercellular fibrillar skeleton is responsible for maintaining the wide (about 50 nm) and uniform plasma membrane separation along the entire length of the basallateral region of the tubular cells of the thick ascending limb.     

Overcoming Space‐Charge Effect for Efficient Thick‐Film Non‐Fullerene Organic Solar Cells

Organic solar cells (OSCs) containing non‐fullerene acceptors have realized high power conversion efficiency (PCE) up to 14%. However, most of these high‐performance non‐fullerene OSCs have been reported with optimal active layer thickness of about 100 nm, mainly due to the low electron mobility (≈10^?4–10^?5 cm² V^?1 s^?1) of non‐fullerene acceptors, which are not suitable for roll‐to‐roll large‐scale processing. In this work, an efficient non‐fullerene OSC based on poly[(5,6‐difluoro‐2,1,3‐benzothiadiazol‐4,7‐diyl)‐alt‐(3,3′″‐di(2‐octyldodecyl)‐2,2′;5′,2″;5″,2′″‐quaterthiophen‐5,5′′′‐diyl)] (PffBT4T‐2OD):EH‐IDTBR (consists of electron‐rich indaceno[1,2‐b:5,6‐b′]dithiophene as the central unit and an electron‐deficient 5,6‐benzo[c][1,2,5]thiadiazole unit flanked with rhodanine as the peripheral group) with thickness‐independent PCE (maintaining a PCE of 9.1% with an active layer thickness of 300 nm) is presented by optimizing device architectures to overcome the space‐charge effects. Optical modeling reveals that most of the incident light is absorbed near the transparent electrode side in thick‐film devices. The transport distance of electrons with lower mobility will therefore be shortened when using inverted device architecture, in which most of the excitons are generated close to the cathode side and therefore substantially reduces the accumulation of electrons in the device. As a result, an efficient thick‐film non‐fullerene OSC is realized. These results provide important guidelines for the development of more efficient thick‐film non‐fullerene OSCs.     

Sub-microsecond chlorophyll A delayed fluorescence from Photosystem I Magnetic field-induced increase of the emission yield

(1) In photosystem I (PS I) particles in the presence of dithionite and intense background illumination at 290 K, an external magnetic field (0–0.22 T) induced an increase, ΔF, of the low chlorophyll a emission yield, F ($\text{ΔF}\text{F}\text{? 1–1.5\%}$). Half the effect was obtained at about 35–60 mT and saturation occurred for magnetic fields higher than about 0.15 T. In the absence of dithionite, no field-induced increase was observed. Cooling to 77 K decreased ΔF at 685 nm, but not at 735 nm, to zero. Measuring the emission spectra of F and ΔF, using continuous excitation light, at 82, 167 and 278 K indicated that the spectra of F and ΔF have about the same maximum at about 730, 725 and 700 nm, respectively. However, the spectra of ΔF show more long-wavelength emission than the corresponding spectra of F. (2) Only in the presence of dithionite and with (or after) background illumination, was a luminescence (delayed fluorescence) component observed at 735 nm, after a 15 ns laser flash (530 nm), that decayed in about 0.1 μs at room temperature and in approx. 0.2 μs at 77 K. A magnetic field of 0.22 T caused an appreciable increase in luminescence intensity after 250 ns, probably mainly caused by an increase in decay time. The emission spectra of the magnetic field-induced increase of luminescence, ΔL, at 82, 167 and 278 K coincided within experimental error with those of ΔF mentioned above. The temperature dependence of ΔF and ΔL was found to be nearly the same, both at 685 and at 735 nm. (3) Analogously to the proposal concerning the 0.15 μs luminescence in photosystem II (Sonneveld, A., Duysens, L.N.M. and Moerdijk, A. (1980) Proc. Natl. Acad. Sci. U.S.A. 77, 5889–5893), we propose that recombination of the oxidized primary donor P-700⁺ and the reduced acceptor A^?, probably A^?₁, of PS I causes the observed fast luminescence. The effect of an external magnetic field on this emission may be explained by the radical pair mechanism. The field-induced increase of the 0.1–0.2 μs luminescence seems to be at least in large part responsible for the observed increase of the total (prompt + delayed) emission measured during continuous illumination in the presence of a magnetic field.     

How the formation process influences the structure of BChl c aggregates

The change of absorption spectra has been measured during the drying process of (3¹ R)bacteriochlorophyll (BChl) c from diethyl ether, dichloromethane (CH₂Cl₂) and carbon tetrachloride (CCl₄) solutions. Absorption maxima of the Q_y(0–0) transition of BChl c appear at 659 nm in diethyl ether, 680 nm in CH₂Cl₂ and 710 nm in CCl₄. All these peaks are red-shifted to about 740 nm with formation of solid high aggregates when the solutions are completely dried. Fourier transform infrared spectra of the three solid aggregates are almost identical. However, magnetic circular dichroism and circular dichroism spectra are different and can be explained in terms of variations in stacking size of the aggregates and molecular arrangement of BChl c. Small-angle X-ray diffraction has been observed only for the aggregates treated with CH₂Cl₂, and the same sample gave rise to highly resolved cross polarization/magic angle spinning ¹³C nuclear magnetic resonance spectrum. The results suggest that molecular ordering of the solid-state BChl c aggregates is highly dependent on the formation process which is largely determined by the solvent used.     

Magnetic behaviour of negatively charged nickel(II) hexacyanoferrate(III) coordination nanoparticles

Negatively charged 4 nm bimetallic Ni^II–Fe^III cyanide-bridged nanoparticles were obtained and isolated by different coating agents. The magnetic properties of the particles were studied in the powder form and in diluted samples. A spin-glass like behaviour occurs in the concentrated sample, while the magnetic behaviour of the diluted ones strongly depends on the method used to isolate the nanoparticles. Only high dilution in a polymer matrix leads to a single-domain superparamagnetic behaviour, with a blocking temperature of 3.5 K.     

Lessons from a tarantula: new insights into muscle thick filament and myosin interacting-heads motif structure and function

The tarantula skeletal muscle X-ray diffraction pattern suggested that the myosin heads were helically arranged on the thick filaments. Electron microscopy (EM) of negatively stained relaxed tarantula thick filaments revealed four helices of heads allowing a helical 3D reconstruction. Due to its low resolution (5.0 nm), the unambiguous interpretation of densities of both heads was not possible. A resolution increase up to 2.5 nm, achieved by cryo-EM of frozen-hydrated relaxed thick filaments and an iterative helical real space reconstruction, allowed the resolving of both heads. The two heads, “free” and “blocked”, formed an asymmetric structure named the “interacting-heads motif” (IHM) which explained relaxation by self-inhibition of both heads ATPases. This finding made tarantula an exemplar system for thick filament structure and function studies. Heads were shown to be released and disordered by Ca²⁺-activation through myosin regulatory light chain phosphorylation, leading to EM, small angle X-ray diffraction and scattering, and spectroscopic and biochemical studies of the IHM structure and function. The results from these studies have consequent implications for understanding and explaining myosin super-relaxed state and thick filament activation and regulation. A cooperative phosphorylation mechanism for activation in tarantula skeletal muscle, involving swaying constitutively Ser35 mono-phosphorylated free heads, explains super-relaxation, force potentiation and post-tetanic potentiation through Ser45 mono-phosphorylated blocked heads. Based on this mechanism, we propose a swaying-swinging, tilting crossbridge-sliding filament for tarantula muscle contraction.