Functionalization of poly-SNS-anchored carboxylic acid with Lys and PAMAM: surface modifications for biomolecule immobilization/stabilization and bio-sensing applications

Poly(2-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl) (SNS) acetic acid) was electrochemically deposited on graphite electrodes and functionalized with lysine (Lys) amino acid and poly(amidoamine) derivatives (PAMAM?G2 and PAMAM?G4) to investigate their matrix properties for biosensor applications. Glucose oxidase (GOx) was immobilized onto the modified surface as the model enzyme. X-Ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to report the surface properties of the matrices in each step of the biosensor construction. The biosensors were characterized in terms of their operational and storage stabilities and the kinetic parameters (K and I(max)). Three new glucose biosensors revealed good stability, featuring low detection limits (19.0 μM, 3.47 μM and 2.93 μM for lysine-, PAMAM?G2- and PAMAM?G4-functionalized electrodes, respectively) and prolonged the shelf lives (4, 5, and 6 weeks for Lys-, PAMAM?G2- and PAMAM?G4-modified electrodes, respectively). The proposed biosensors were tested for glucose detection on real human blood serum samples.     

The Existence and Construction of (K5∖e)‐Designs of Orders 27, 135, 162, and 216

The problem of the existence of a decomposition of the complete graph into disjoint copies of has been solved for all admissible orders n, except for 27, 36, 54, 64, 72, 81, 90, 135, 144, 162, 216, and 234. In this paper, I eliminate 4 of these 12 unresolved orders. Let Γ be a ‐design. I show that divides 2^k3 for some and that . I construct ‐designs by prescribing as an automorphism group, and show that up to isomorphism there are exactly 24 ‐designs with as an automorphism group. Moreover, I show that the full automorphism group of each of these designs is indeed . Finally, the existence of ‐designs of orders 135, 162, and 216 follows immediately by the recursive constructions given by G. Ge and A. C. H. Ling, SIAM J Discrete Math 21(4) (2007), 851–864.     

Diffusion-controlled detection of trinitrotoluene: interior nanoporous structure and low highest occupied molecular orbital level of building blocks enhance selectivity and sensitivity

Development of simple, cost-effective, and sensitive fluorescence-based sensors for explosives implies broad applications in homeland security, military operations, and environmental and industrial safety control. However, the reported fluorescence sensory materials (e.g., polymers) usually respond to a class of analytes (e.g., nitroaromatics), rather than a single specific target. Hence, the selective detection of trace amounts of trinitrotoluene (TNT) still remains a big challenge for fluorescence-based sensors. Here we report the selective detection of TNT vapor using the nanoporous fibers fabricated by self-assembly of carbazole-based macrocyclic molecules. The nanoporosity allows for time-dependent diffusion of TNT molecules inside the material, resulting in further fluorescence quenching of the material after removal from the TNT vapor source. Under the same testing conditions, other common nitroaromatic explosives and oxidizing reagents did not demonstrate this postexposure fluorescence quenching; rather, a recovery of fluorescence was observed. The postexposure fluorescence quenching as well as the sensitivity is further enhanced by lowering the highest occupied molecular orbital (HOMO) level of the nanofiber building blocks. This in turn reduces the affinity for oxygen, thus allocating more interaction sites for TNT. Our results present a simple and novel way to achieve detection selectivity for TNT by creating nanoporosity and tuning molecular electronic structure, which when combined may be applied to other fluorescence sensor materials for selective detection of vapor analytes.     

Spin-orbit-induced photoelectron spin polarization in angle-resolved photoemission from both atomic and condensed matter targets

The existence of highly spin polarized photoelectrons emitted from non-magnetic solids as well as from unpolarized atoms and molecules has been found to be very common in many studies over the past 40 years. This so-called Fano effect is based upon the influence of the spin-orbit interaction in the photoionization or the photoemission process. In a non-angle-resolved photoemission experiment, circularly polarized radiation has to be used to create spin polarized photoelectrons, while in angle-resolved photoemission even unpolarized or linearly polarized radiation is sufficient to get a high spin polarization. In past years the Rashba effect has become very important in the angle-resolved photoemission of solid surfaces, also with an observed high photoelectron spin polarization. It is the purpose of the present topical review to cross-compare the spin polarization experimentally found in angle-resolved photoelectron emission spectroscopy of condensed matter with that of free atoms, to compare it with the Rashba effect and topological insulators to describe the influence and the importance of the spin-orbit interaction and to show and disentangle the matrix element and phase shift effects therein.The relationship between the energy dispersion of these phase shifts and the emission delay of photoelectron emission in attosecond-resolved photoemission is also discussed. Furthermore the influence of chiral structures of the photo-effect target on the spin polarization, the interferences of different spin components in coherent superpositions in photoemission and a cross-comparison of spin polarization in photoemission from non-magnetic solids with XMCD on magnetic materials are presented; these are all based upon the influence of the spin-orbit interaction in angle-resolved photoemission.     

A new donor–acceptor double‐cable carbazole polymer with perylene bisimide pendant group: Synthesis,electrochemical, and photovoltaic properties

We report here electrochemical synthesis of novel soluble donor–acceptor (D–A) polymer with suitably functionalized perylenetetracarboxylic diimide dye derivative covalently linked to carbazole moiety (Cbz‐PDI). The band gap, E_g was measured using UV–Vis spectroscopy and compared with that obtained by cyclic voltammetry (CV). Efficient intramolecular electron transfer from carbazole‐donor to perynediimide‐acceptor leads to remarkable fluorescence quenching of the perylene core. Furthermore, spectroelectrochemical property and surface morphology of the polymer film were investigated. Characteristic monoanion and dianion radical bands on the UV–Vis absorption spectra attributed to the electrochemical reduction of the neutral polymer were observed. During the reduction process, red color of the film turned into blue and violet, respectively. Finally, the photovoltaic performance of the D–A double‐cable polymer was checked and nearly 0.1% electrical conversion efficiency is obtained under simulated AM 1.5 solar light with 100 mW/cm² radiation power. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6280–6291, 2009     

Giant magnetocaloric effect in Tb5Ge2-xSi2-xMn2x compounds

The crystal structure,magnetic and magnetocaloric characteristics of the pseduo ternary compounds of Tb5Ge2 xSi2 xMn2x(0 ≤ 2x ≤ 0.1) were investigated by x-ray powder diffraction and magnetization measurements.The x-ray powder diffraction results show that all compounds preserve the monoclinic phase as the majority phase and all the synthesized compounds were observed to be ferromagnetic from magnetization measurements.Magnetic phase transitions were interpreted in terms of Landau theory.Maximum isothermal magnetic entropy change value(20.84 J.kg-1.K-1) was found for Tb5Ge1.95Si1.95Mn0.1 at around 123 K in the magnetic field change of 5 T.     

Form-stable electrospun nanofibrous mats as a potential phase change material

A series of Poly vinyl butyral–Poly (acrylic acid) (PVB-PAA) based form-stable phase change materials (PCMs) have been prepared for the use of thermal energy storage applications. Six types of formulations containing five different fatty alcohols were prepared by adding PVB to PAA. Using electrospinning to fabricate nanofibrous mats, our aim was to investigate their properties as form-stable PCMs. Fatty alcohols, 1-Tetradecanol, 1-Hexadecanol, 1-Octadecanol, 1-Eicosanol and 1-Docosanol, were added separately to base formulation. The structural characterization tests were performed by ATR-FTIR spectroscopy. Morphological tests were conducted using Scanning Electron Microscope (SEM). Thermal performances and phase change behaviors were tested by thermogravimetric analysis system (TGA) and differential scanning calorimetry (DSC). The heating cycle phase change enthalpy is measured between 223 and 241?J/g, and the freezing cycle phase change enthalpy is found between 215 and 239?J/g. The main decomposition PVB-PAA based PCMs started at 220?°C. This study suggested that PVB-PAA based PCMs possess well phase change properties and they were found to have an applicable temperature range. With the presented results these materials promise a great potential in thermal energy storage applications.     

Synthesis of novel 2,3‐disubstituted quinazolin‐4(3H)‐one derivatives containing hydrazone skeleton as potent urease inhibitors and their antimicrobial activities

A new series of quinazolinones containing hydrazone moiety were synthesized, and their inhibitory activities on urease were assessed in vitro. Most of the compounds exhibited potent urease inhibitory activity. Among the synthesized compounds, molecule 4a bearing furan ring has the best inhibitory effect against urease with IC₅₀ = 2.90 ± 0.11 μg/mL. Compounds 4f , 4g , 4h , 4i , and 4j have hydroxy group on phenyl ring. Compound 4i is the most active inhibitor among these compounds with IC₅₀ = 5.01 ± 0.10 μg/mL, which has 3‐Cl and 4‐Br on phenyl ring. Also, newly synthesized compounds had been tested for their antimicrobial effects against three of Gram‐positive bacteria (Bacillus cereus 702 Roma, Staphylococcus aureus ATCC 25923, and Streptococcus pyogenes ATCC 19615) and three of Gram‐negative bacteria (Escherichia coli ATCC 25922, Proteus vulgaris ATCC 13315, and Pseudomonas aeruginosa ATCC 27853). Antimicrobial activity results show that compounds 4a , 4h , 4j , 4f , and 4l have the lowest minimum inhibitory concentration (MIC) value of 1000 μg/mL to all tested bacteria. The other compounds have the MIC value of >1000 μg/mL to all tested bacteria.