Sub-ppt level voltammetric sensor for Hg2+ detection based on nafion stabilized l-cysteine-capped Au@Ag core-shell nanoparticles

Journal of Solid State Electrochemistry - Bimetallic nanoparticles (BMNPs) have received considerable attention due to their distinctive properties when compared to the corresponding monometallic...     

Properties of the angular gap in a one-dimensional photonic band gap structure containing single negative materials

Properties of the angular gap in a one-dimensional photonic band gap structure containing single negative materials are investigated. This gap forms at oblique incidence due to the total internal reflection into air when the Snell's law breaks down. Its lower edge occurs at the frequency where the refractive index of one or both layers of the structure approaches zero. This gap is found to be highly sensitive to the incident angle and the polarization of the incident light, but is not affected by the thickness ratio of the layers. It is also shown that the electric field gets extremely enhanced at the lower edge of this gap for transverse magnetic polarization. This highly enhanced electric field can be utilized for certain applications.     

Optical bistability at angular incidence in a one-dimensional photonic crystal containing single negative materials

Nonlinear wave propagation is studied theoretically in a one-dimensional photonic band gap structure containing single negative materials. It is found that Kerr nonlinearity is greatly enhanced near the lower edge of a recently explored angular gap for transverse magnetic polarized light. Consequently, optical bistability is achieved at very low values of input intensity in a periodic structure composed of only a few repeating units. The characteristics of optical bistability are affected only slightly with the variation of the incident angle and thickness ratio of the layers. The effect of losses is also found to be relatively insignificant in such a small structure.     

Highly selective enrichment of phosphopeptides using poly(dibenzo‐18‐crown‐6) as a solid‐phase extraction material

A poly(dibenzo‐18‐crown‐6) was used as a new solid‐phase extraction material for the selective enrichment of phosphopeptides. Isolation of phosphopeptides was achieved based on specific ionic interactions between poly(dibenzo‐18‐crown‐6) and the phosphate group of phosphopeptides. Thus, a method was developed and optimized, including loading, washing and elution steps, for the selective enrichment of phosphopeptides. To assess this potential, tryptic digest of three proteins (α‐ casein, β‐casein and ovalbumin) was applied on poly(dibenzo‐18‐crown‐6). The nonspecific products were removed by centrifugation and washing. The spectrometric analysis was performed using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. Highly selective enrichment of both mono‐ and multiphosphorylated peptides was achieved using poly(dibenzo‐18‐crown‐6) as solid‐phase extraction material with minimum interference from nonspecific compounds. Furthermore, evaluation of the efficiency of the poly(dibenzo‐18‐crown‐6) was performed by applying the digest of egg white. Finally, quantum mechanical calculations were performed to calculate the binding energies to predict the affinity between poly(dibenzo‐18‐crown‐6) and various ligands. The newly identified solid‐phase extraction material was found to be a highly efficient tool for phosphopeptide recovery from tryptic digest of proteins.     

Properties of single and multiple defect modes in one-dimensional photonic crystals containing left-handed metamaterials

Wave propagation is studied in structures consisting of alternate left- and right-handed layers.Bragg gap and zero-n gap appear in different frequency regions of the structure.The periodicity of the structure is broken by simply reversing the order of the layers in one half of the structure,resulting in defect modes located inside the zero-n gap and Bragg gap.These modes can be made very narrow by adding more layers in the structure.The defect mode located inside the zero-n gap is sensitive to the symmetry of the structure and insensitive to the angle of incidence of the incoming radiation.Multiple modes are also generated inside the gaps by repeating the structural pattern.Thus,a simple structure can be used for single and multiple modes that are important for different applications.     

Highly efficient precipitation of phosphoproteins using trivalent europium,terbium, and erbium ions

This study describes a highly efficient method for the selective precipitation of phosphoproteins by trivalent europium, terbium, and erbium metal ions. These metal cations belong to the group of lanthanides and are known to be hard acceptors with an overwhelming preference for oxygen-containing anions such as phosphates to which they form very tight ionic bonds. The method could be successfully applied to specifically precipitate phosphoproteins from complex samples including milk and egg white by forming solid metal–protein complexes. Owing to the low solubility product of the investigated lanthanide salts, the produced metal–protein complexes showed high stability. The protein pellets were extensively washed to remove nonphosphorylated proteins and contaminants. For the analysis of proteins the pellets were first dissolved in 30 % formic acid and subjected to matrix-assisted laser desorption/ionization–time of flight (MALDI-TOF) MS. For peptide mass-fingerprint analysis the precipitated phosphoproteins were enzymatically digested using microwave-assisted digestion. The method was found to be highly specific for the isolation and purification of phosphoproteins. Protein quantification was performed by colorimetric detection of total precipitated phosphoproteins and revealed more than 95 % protein recovery for each lanthanide salt.     

A novel strategy for phosphopeptide enrichment using lanthanide phosphate co-precipitation

Reversible phosphorylation of proteins is a common theme in the regulation of important cellular functions such as growth, metabolism, and differentiation. The comprehensive understanding of biological processes requires the characterization of protein phosphorylation at the molecular level. Although, the number of cellular phosphoproteins is relatively high, the phosphorylated residues themselves are generally of low abundance due to the sub-stoichiometric nature. However, low abundance of phosphopeptides and low degree of phosphorylation typically necessitates isolation and concentration of phosphopeptides prior to mass spectrometric analysis. In this study, we used trivalent lanthanide ions (LaCl(3), CeCl(3), EuCl(3), TbCl(3), HoCl(3), ErCl(3), and TmCl(3)) for phosphopeptide enrichment and cleaning-up. Due to their low solubility product, lanthanide ions form stable complexes with the phosphate groups of phosphopeptides and precipitate out of solution. In a further step, non-phosphorylated compounds can easily be removed by simple centrifugation and washing before mass spectrometric analysis using Matrix-assisted laser desorption/ionisation-time of flight. The precipitation method was applied for the isolation of phosphopeptides from standard proteins such as ovalbumin, α-casein, and β-casein. High enrichment of phosphopeptides could also be achieved for real samples such as fresh milk and egg white. The technology presented here represents an excellent and highly selective tool for phosphopeptide recovery; it is easily applicable and shows several advantages as compared with standard approaches such as TiO(2) or IMAC.     

Higher-order inertial Alfvén wave dressed solitons,quasiperiodic structures,and chaos in plasmas

The higher-order, low-amplitude inertial Alfvén wave (IAW) dressed soliton and chaos are investigated in a magnetized plasma. In the linear limit, the dispersion relation for propagation of IAWs in plasmas is also obtained in the presence of electron thermal effects and illustrated numerically. It is found that the electron inertial length plays an important role for wave dispersion effects and its phase speed is increased on including the electron temperature in the model. The reductive perturbation method is employed to obtain the first-order IAW Korteweg–de Vries (KdV) soliton and second-order dressed soliton solutions analytically, which gives electron density dip (or rarefactive) structure and moves with super Alfvénic speed in plasmas. The numerical illustrations of the KdV and dressed IAW solitons are also presented by using the laboratory and space plasma parameters given in the literature. Furthermore, a numerical study of quasi-periodicity and chaotic behaviour of IAWs in the presence of external periodic force is also discussed in detail. The effects of plasma beta (which depends on plasma density, electron temperature, and magnetic field intensity) and obliqueness of the wave propagation on the formation of nonlinear Alfvénic wave structures have also been presented.     

Nonlinear Localization due to a Double Negative Defect Layer in a One-Dimensional Photonic Crystal Containing Single Negative Material Layers

We investigate the effects of introducing a defect layer negative material layers on the transmission properties in a one-dimensional photonic crystal containing single The width of the defect layer is taken to be the same or smaller than the period of the structure. Different cases of the defect layer being linear or nonlinear and double positive or double negative are discussed. It is found that only a nonlinear double negative layer gives rises to a localized mode within the zero-Φeff gap in this kind of structure. It is also shown that the important characteristics of the nonlinear defect mode such as its frequency, its FWHM and the threshold of the associated bistability can be controlled by changing the widths of the defect layer and the host layers.     

Thienopyrazine‐Based Low‐Bandgap Poly(heteroaryleneethynylene)s for Photovoltaic Devices

Summary: Low‐bandgap π‐conjugated polymers that consist of alkyl thiophene/alkoxy phenylene and 2,3‐diphenylthieno[3,4‐b]pyrazine units have been prepared in high yields by a Sonogashira polycondensation. The copolymers are characterized by NMR, IR, UV, GPC, and elemental analysis. Thin films of the polymers P1 , P2 , and P3 exhibit an optical bandgap of ≈1.57–1.60 eV. Under simulated AM 1.5 conditions P2/PCBM devices on polyester foil provide a short circuit current of I_SC = 10.72 mA · cm⁻², an open circuit voltage of V_oc = 0.67 V, and a power conversion efficiency of 2.37%.

Schematic of the photovoltaic device made from the polymers synthesized here.