Rationally Designed Fluorescent pH Sensors for Measurements in Extremely Alkaline Media

We investigated the pK_a increasing effects on meso-phenol BODIPY to achieve fluorescent pH sensors working in extreme alkalinity. We demonstrated the effects of substituents on meso, α, γ and position of the hydroxyl group on pK_a. By considering these parameters, we developed pH sensors working above 11.0 in aqueous medium (ethanol/water 1:1). One of these sensors had a pK_a of 12.0 and enabled the measurement of pH up to 13.6. This highly photostable and bright sensor compound could be synthesized easily from cheap starting materials.     

Increasing the detection speed of an all-electronic real-time biosensor

Biosensor response time, which depends sensitively on the transport of biomolecules to the sensor surface, is a critical concern for future biosensor applications. We have fabricated carbon nanotube field-effect transistor biosensors and quantified protein binding rates onto these nanoelectronic sensors. Using this experimental platform we test the effectiveness of a protein repellent coating designed to enhance protein flux to the all-electronic real-time biosensor. We observe a 2.5-fold increase in the initial protein flux to the sensor when upstream binding sites are blocked. Mass transport modelling is used to calculate the maximal flux enhancement that is possible with this strategy. Our results demonstrate a new methodology for characterizing nanoelectronic biosensor performance, and demonstrate a mass transport optimization strategy that is applicable to a wide range of microfluidic based biosensors.     

Measurement of the neutron radius of 208Pb through parity violation in electron scattering

We report the first measurement of the parity-violating asymmetry A(PV) in the elastic scattering of polarized electrons from 208Pb. A(PV) is sensitive to the radius of the neutron distribution (R(n)). The result A(PV)=0.656±0.060(stat)±0.014(syst) ppm corresponds to a difference between the radii of the neutron and proton distributions R(n)-R(p)=0.33(-0.18)(+0.16) fm and provides the first electroweak observation of the neutron skin which is expected in a heavy, neutron-rich nucleus.     

N-Heterocyclic Olefins on a Silicon Surface

The adsorption of N-heterocyclic olefins (NHOs) on silicon is investigated in a combined scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory study. We find that both of the studied NHOs bind covalently, with ylidic character, to the silicon adatoms of the substrate and exhibit good thermal stability. The adsorption geometry strongly depends on the N-substituents: for large N-substituents, an upright adsorption geometry is favored, while a flat-lying geometry is found for the NHO with smaller wingtips. These different geometries strongly influence the quality and properties of the obtained monolayers. The upright geometry leads to the formation of ordered monolayers, whereas the flat-lying NHOs yield a mostly disordered, but denser, monolayer. The obtained monolayers both show large work function reductions, as the higher density of the flat-lying monolayer is found to compensate for the smaller vertical dipole moments. Our findings offer new prospects in the design of tailor-made ligand structures in organic electronics and optoelectronics, catalysis, and material science.     

Structural and magnetic studies on mono- and polynuclear chromium ascorbate complexes

Polynuclear chromium ascorbate complexes were isolated and physicochemically analyzed in a comparative manner with their mononuclear analog (1). Characterization by elemental analysis, electronic, vibrational, ¹³C-n.m.r and mass spectroscopies, and variable temperature magnetic susceptibility studies, allowed structural proposals for the binuclear, [Cr₂(μ-OH)₂(H₂O)(C₆H₇O₆)₃(OH)] · 4H₂O (2), and trinuclear, [Cr₃(μ-O)₃(H₂O)₆(C₆H₇O₆)₃] · 4 H₂O (3) complexes. The pseudo-octahedral Cr^III centers were suggested to be connected through hydroxo bridges in (2) and in (3) by oxo bridges forming a hexocyclic ring. An erratum to this article is available at .     

Facilitated Transport of Cr(VI) through Polymer Inclusion Membrane System Containing Calix[4]arene Derivative as Carrier Agent

Chromium(VI) is one of the major toxic elements present in environmental samples. The polymer inclusion membrane (PIM), has been developed to provide metal ion transport with high selectivity. This study was conducted to discover efficient methods for removing Cr(VI) from wastewater. A functionalized calix[4]arene carrier 1 in a PIM system was used to transport Cr(VI) from an acidic aqueous donor phase solution to an acceptor phase that contained an acetic acid/ammonium acetate solution at pH 6. The prepared PIM was characterized with Fourier Transform Infrared (FT-IR) spectroscopy and the Atomic Force Microscopy (AFM) techniques as well as with contact angle measurements. The efficiency of Cr(VI) transport through the PIM was investigated by studying the effects of carrier concentration on the membrane phase as well as by measuring the amount of plasticizer in the membrane, the pH in the acceptor phase and the membrane's stability and thickness. The kinetic parameters were calculated as rate constant (k), permeability coefficient (P), flux (J) and diffusion coefficient (D_o). The transport efficiency of Cr(VI) was observed to be 98.61% after 10 h under optimized conditions. The experimental results show that Cr(VI) can transport from the donor phase to the acceptor phase with high efficiency through the PIM. The results also suggest that the transport efficiency of the PIM was reproducible and that a PIM is effective for long-term separation processes.     

Immobilization of Inulinase on Concanavalin A-Attached Super Macroporous Cryogel for Production of High-Fructose Syrup

In this study, concanavalin A (Con A)-attached poly(ethylene glycol dimethacrylate) [poly(EGDMA)] cryogels were used for immobilization of Aspergillus niger inulinase. For this purposes, the monolithic cryogel column was prepared by radical cryocopolymerization of EGDMA as a monomer and N,N′-methylene bisacrylamide as a crosslinker. Then, Con A was attached by covalent binding onto amino-activated poly(EGDMA) cryogel via glutaraldehyde activation. Characterization of cryogels was performed by FTIR, EDX, and SEM studies. Poly(EGDMA) cryogels were highly porous and pore size was found to be approximately 50–100 μm. Con A-attached poly(EGDMA) cryogels was used in the adsorption of inulinase from aqueous solutions. Adsorption of inulinase on the Con A-attached poly(EGDMA) cryogel was performed in continuous system and the effects of pH, inulinase concentration, and flow rate on adsorption were investigated. The maximum amount of inulinase adsorption was calculated to be 27.85 mg/g cryogel at 1.0 mg/mL inulinase concentration and in acetate buffer at pH 4.0. Immobilized inulinase was effectively used in continuous preparation of high-fructose syrup. Inulin was converted to fructose in a continuous system and released fructose concentration was found to be 0.23 mg/mL at the end of 5 min of hydrolysis. High-fructose content of the syrup was demonstrated by thin layer chromatography.     

Synthesis,characterization, crystal structure and biological activity of the cobalt(IV) complex of 2,6-diacetylpyridine dioxime: [Co(dapdo)<Subscript>2</Subscript>]

The cobalt(IV) complex of 2,6-diacetylpyridine dioxime (dapdoH₂) was prepared and characterized by X-ray diffraction, elemental analysis and FT-IR. The titled complex was found to crystallize in the orthorhombic space group and was screened for antibacterial and antifungal activities by the disc diffusion and microtitter plate techniques using DMF as solvent. It has been found that the antimicrobial activity of the complex [Co(dapdo)₂] is slightly higher than the free ligand (dapdoH₂).