Effective in-device r33 of 735 pm/V on electro-optic polymer infiltrated silicon photonic crystal slot waveguides

We design and fabricate a 320?nm slot for an electro-optic (E-O) polymer infiltrated silicon photonic crystal waveguide. Because of the large slot width, the poling efficiency of the infiltrated E-O polymer (AJCKL1/amorphous polycarbonate) is significantly improved. When coupled with the slow light effect from the silicon photonic crystal waveguide, an effective in-device r(33) of 735?pm/V, which to our knowledge is a record high, is demonstrated, which is ten times higher than the E-O coefficient achieved in thin film material. Because of this ultrahigh E-O efficiency, the V(π)L of the device is only 0.44?V?mm, which is to our knowledge the best result of all E-O polymer modulators.     

Universal electrostatic origin of cation ordering in A2BO4 spinel oxides

The crystal structures of A(2)BO(4) spinel oxides are classified as either normal or inverse, representing different distributions of the A and B cations over the tetrahedrally and octahedrally coordinated cation sites. These structures undergo characteristic structural changes as a function of temperature: (i) the nominally disordered inverse structure orders crystallographically at low T, and (ii) at finite temperatures, both inverse and normal develop characteristic distributions of cations associated with order-disorder structural changes. We show here that all of these universal features emerge naturally from a simple point-ion electrostatic (PIE) model with a single adjustable parameter. Monte Carlo simulations of the PIE Hamiltonian provide quantitative order-disorder characteristic temperatures. We show that, with the help of the PIE model, the magnitude of the temperatures can be inferred from the nominal charges of the atomic species in the spinel. Indeed, we show that characteristic order-disorder temperatures in 3-2 spinels (nominal charges Z(A) = 3 and Z(B) = 2) are approximately an order of magnitude lower than in 2-4 spinels, thus explaining why typical 3-2 samples exhibit much larger degrees of disorder than those belonging to the 2-4 class.     

Larvicide Activity on Aedes aegypti of Essential Oil Nanoemulsion from the Protium heptaphyllum Resin

The aim of this work was to prepare a nanoemulsion containing the essential oil of Protium heptaphyllum resin and to evaluate the larvicidal activity and the residual larvicidal effect against Aedes aegypti. The essential oil was identified by gas chromatography coupled to a mass spectrometer, and the nanoemulsions were prepared using a low-energy method and characterized by photon correlation spectroscopy. The results indicated the major constituents as p-cimene (27.70%) and α-Pinene (22.31%). Nanoemulsions had kinetic stability and a monomodal distribution in a hydrophilic-lipophilic balance of 14 with particle diameters of 115.56 ± 1.68 nn and zeta potential of −29.63 ± 3.46 mV. The nanoemulsion showed larvicidal action with LC₅₀ = 2.91 µg∙mL⁻¹ and residual larvicidal effect for 72 h after application to A. aegypti larvae. Consequently, the nanobiotechnological product derived from the essential oil of P. heptaphyllum resin could be used against infectious disease vectors.     

Synthesis of Polyampholyte Janus‐like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization

Controlling the distribution of ionizable groups of opposite charge in microgels is an extremely challenging task, which could open new pathways to design a new generation of stimuli‐responsive colloids. Herein, we report a straightforward approach for the synthesis of polyampholyte Janus‐like microgels, where ionizable groups of opposite charge are located on different sides of the colloidal network. This synthesis approach is based on the controlled self‐assembly of growing polyelectrolyte microgel precursors during the precipitation polymerization process. We confirmed the morphology of polyampholyte Janus‐like microgels and demonstrate that they are capable of responding quickly to changes in both pH and temperature in aqueous solutions.     

Supramolecular Amperometric Immunosensor for Detection of Human Chorionic Gonadotropin

Human chorionic gonadotropin (hCG) is a hormone produced in high concentrations through the placental trophoblasts and is used for the detection of pregnancy and certain diseases. Here we explored a supramolecular strategy for the potentially substrateless amperometric detection of hCG. A carboxymethylcellulose (CMC) carrier was synthesised and trifunctionalised with anti‐βhCG antibody, horse radish peroxidase (HRP) and ferrocene (Fc) moieties. The ferrocene was used to house the functionalised CMC within the cavities of electrode surface immobilised cyclodextrin, via host‐guest interactions. hCG was detected via a sandwich format, forming an immunocomplex between the surface immobilised antibody and a glucose oxidase/lactate oxidase labelled secondary antibody. Following formation of the immunocomplex, lactate/glucose, which would typically be present in serum/urine samples, was added and the hydrogen peroxide formed detected at the electrode surface via the HRP‐Fc enzyme‐mediator couple. The work reported demonstrates a potential supramolecular platform for the detection of targets in blood/urine samples using endogenous substrates.     

Superoxide Formation on Isolated Cationic Gold Clusters

Gold nanoparticles are known to be highly versatile oxidation catalysts utilizing molecular oxygen as a feedstock, but the mechanism and species responsible for activating oxygen remain unclear. The reaction between unsupported cationic gold clusters and molecular oxygen has been investigated. The resulting complexes were characterized in the gas phase using IR spectroscopy. A strong red‐shift in the observed ν(O‐O) stretching frequency indicates the formation of superoxo (O₂^?) moieties. These moieties are seen to form spontaneously in systems, which upon electron transfer attain a closed shell within the spherical jellium model (Au₁₀⁺ and Au₂₂⁺), whereas an oxygen induced self‐promotion in the activation is observed for other systems (Au₄⁺, Au₁₂⁺, Au₂₁⁺).     

Nickel‐Catalyzed Csp2Csp3 Bond Formation by CarbonFluorine Activation

We report herein a general catalytic method for Csp²?Csp³ bond formation through C?F activation. The process uses an inexpensive nickel complex with either diorganozinc or alkylzinc halide reagents, including those with β‐hydrogen atoms. A variety of fluorine substitution patterns and functional groups can be readily incorporated. Sequential reactions involving different precatalysts and coupling partners permit the synthesis of densely functionalized fluorinated building blocks.     

Combined EXAFS and DFT Structure Calculations Provide Structural Insights into the 1:1 Multi‐Histidine Complexes of CuII,CuI, and ZnII with the Tandem Octarepeats of the Mammalian Prion Protein

The metal‐coordinating properties of the prion protein (PrP) have been the subject of intense focus and debate since the first reports of its interaction with copper just before the turn of the century. The picture of metal coordination to PrP has been improved and refined over the past decade, but structural details of the various metal coordination modes have not been fully elucidated in some cases. In the present study, we have employed X‐ray absorption near‐edge spectroscopy as well as extended X‐ray absorption fine structure (EXAFS) spectroscopy to structurally characterize the dominant 1:1 coordination modes for Cu^II, Cu^I, and Zn^II with an N‐terminal fragment of PrP. The PrP fragment corresponds to four tandem repeats representative of the mammalian octarepeat domain, designated as OR₄, which is also the most studied PrP fragment for metal interactions, making our findings applicable to a large body of previous work. Density functional theory (DFT) calculations have provided additional structural and thermodynamic data, and candidate structures have been used to inform EXAFS data analysis. The optimized geometries from DFT calculations have been used to identify potential coordination complexes for multi‐histidine coordination of Cu^II, Cu^I, and Zn^II in an aqueous medium, modelled using 4‐methylimidazole to represent the histidine side chain. Through a combination of in silico coordination chemistry as well as rigorous EXAFS curve‐fitting, using full multiple scattering on candidate structures derived from DFT calculations, we have characterized the predominant coordination modes for the 1:1 complexes of Cu^II, Cu^I, and Zn^II with the OR₄ peptide at pH 7.4 at atomic resolution, which are best represented as square‐planar [Cu^II(His)₄]²⁺, digonal [Cu^I(His)₂]⁺, and tetrahedral [Zn^II(His)₃(OH₂)]²⁺, respectively.     

Features of the melt flow of polyethylene and boron oxide oligomer blends

The features of melt flow of LDPE and boron oxide oligomer blends during extrusion mixing are investigated. It is established that the extruder-wall pressure and the torque of the screw decrease monotonically with an increase in the boron oxide oligomer content up to 25 vol %. Exceeding this concentration threshold leads to a several-fold stepwise fall in of the mentioned characteristics. This result is explained within the concepts about spontaneous restructuring of the blend accompanied by an increase of the specific surface of phases and by slipping at the interface of the blend components that is caused by the planar structure of the boron oxide oligomer molecules.