Quantitative analysis of thymine with surface-enhanced Raman spectroscopy and partial least squares (PLS) regression

Silver sol surface-enhanced Raman spectroscopy (SERS) was considered as a technique in the quantitative analysis of low-concentration thymine. Because of the poor stability and reproducibility of SERS signal, a polymer of polyacrylic acid sodium was selected as a stable medium to add into silver sol in order to obtain a surface-enhanced Raman spectroscopy signal. Assignments of Raman shift for solid thymine, SERS of thymine, and SERS of thymine containing stable medium were given. The comparison of Raman peaks between them showed that the addition of stable medium had a little influence on the SERS of thymine and is suitable for the quantitative analysis of low-concentration thymine.     

[Cu(X-salicylato)2(N,N-diethylnicotinamide)2(H2O)2] complexes: conformational polymorphism and its consequence in supramolecular hydrogen-bonding networks formation

Novel copper(II) X-salicylate complexes with N,N-diethylnicotinamide (dena) of the formula [Cu(RCOO)₂(dena)₂(H₂O)₂] (RCOO = 3-methylsalicylate anion (3-Mesal, 1), 4-methylsalicylate anion (4-Mesal, 2), 5-methylsalicylate anion (5-Mesal, 3), 5-methoxysalicylate anion (5-MeOsal, 4) or 4-methoxysalicylate anion (4-MeOsal, 5)), and complex [Cu(3-MeOsal)₂(dena)₂(H₂O)₂]∙2H₂O (3-MeOsal = 3-methoxysalicylate anion (6)) have been prepared in the crystalline forms and characterized by spectroscopic methods (IR, Vis–UV, EPR). All the compounds according to their composition (1–5) seem to possess octahedral copper(II) stereochemistry. The complex 1 has been prepared in two different forms. X-ray analyses of the complexes 1, 4, and 5 were carried out and they featured a tetragonal-bipyramidal geometry around the copper atoms. The tetragonal planes are created by X-salicylate anions bonded to the copper(II) atoms via unidentate carboxylate oxygen atoms and the pyridine ring nitrogen atoms of the neutral ligand N,N-diethylnicotinamide, while in axial positions are water molecules. The two forms of complex 1 present conformation polymorphs and supramolecular isomers.     

A Systemic DFT Study on Several 5<Emphasis Type="Italic">d</Emphasis>-Electron Element Dimers: Hf<Subscript>2</Subscript>, Ta<Subscript>2</Subscript>, Re<Subscript>2</Subscript>, W<Subscript>2</Subscript>, and Hg<Subscript>2</Subscript>

Eleven kinds of density functionals in conjunction with three different basis sets are employed to investigate the homonuclear 5d-electron dimers: Hf₂, Ta₂, Re₂, W₂ and Hg₂. The computed bond lengths, vibrational frequencies and dissociation energies of these molecules are used to compare with available experimental data to find the appropriate combination of functional and basis set. The different functionals and basis sets favor different ground electronic state for Hf₂ and Re₂ molecules, indicating that these two dimers are sensitive to the functionals used. The molecular properties of Hg₂ dimer depend strongly on both functionals and basis sets used. It is found that the BP86 and PBEPBE functionals are generally successful in describing the 5d-electron dimers. For the ground states of these dimers, the bonding patterns are determined by natural bond orbital (NBO) analysis. Natural electron configurations show that the 6s and 5d orbitals in the bonding atoms hybrid with each other for the studied dimers except for Hg₂.     

Synthesis and characterization of PbS nanotubes in bicontinuous microemulsion system

PbS nanotubes were successfully synthesized in bicontinuous microemulsion system containing cyclohexane, aqueous solution, n-pentanol and surfactant OP (polyethylene glycol p-octylphenyl ether). The morphology of PbS nanotubes was confirmed by the transmission electron microscopy. The crystallinity and structural features of PbS nanotubes were characterized by powder X-ray diffraction. The effect of key parameters, such as the molar ratio of water to surfactant and the reactant concentration, on the resulting product has also been investigated. The formation mechanism of PbS nanotubes and nanowires synthesized in bicontinuous microemulsion system has been discussed.     

Effects of carbon coating on the temperature-dependent electrochemical properties of Li3V2(PO4)3

Carbon coated and carbon free Li₃V₂(PO₄)₃ cathode materials were prepared by carbothermal reduction and H₂ reduction methods, respectively. The carbon free material had a grain size about 1 μm whereas the carbon coated material was less than 100 nm. The surface carbon layer enhanced the electronic conductivity of Li₃V₂(PO₄)₃ by five orders of magnitude. In addition, the surface carbon layer also prevented the formation of SEI film, decreased the charge transfer resistance and increased the chemical diffusion coefficient of Li⁺ ions. All of these advantages improved the electrochemical performance of Li₃V₂(PO₄)₃. As most of intercalation materials, the low temperature performance of Li₃V₂(PO₄)₃ was poorer than that at room temperature. This was attributed to the electrochemical sluggish kinetics which caused higher charge transfer resistance and smaller chemical diffusion coefficient. The carbon coating technique was effective to eliminate these sluggish kinetics, and then improved the low temperature performance of Li₃V₂(PO₄)₃.     

Ultrasensitive nucleic acid detection using confocal laser scanning microscope with high crystalline silver dendrites

A new kind of silver micro-dendrites with no surfactants protected has been synthesized for the separation and detection of DNA merely by earth gravity as the density of silver is larger than that of water. Through this approach, the DNA of human T-lymphotropic virus type I (HTLV-I) can be detected down to 10 pM with the detection range from 10 pM to 100 nM.     

Electrografted Poly(N‐mercaptoethyl acrylamide) and Au Nanoparticles‐Based Organic/Inorganic Film: A Platform for the High‐Performance Electrochemical Biosensors

In this study, we describe the use of the combination of eletrografting poly(N‐mercaptoethyl acrylamide) and Au nanoparticles in the construction of high‐performance biosensors. The poly(N‐mercaptoethyl acrylamide) was electrografted onto the glassy carbon electrode surface, which provided a strongly adhering primer film for the stable attachment of Au nanoparticles and horseradish peroxidase (HRP) enzymes. The performances of the biosensors based on the HRP immobilized in the Au/poly(N‐mercaptoethyl acrylamide) composite film were investigated. A couple of redox peaks were obtained, indicating that the Au nanoparticles could facilitate the direct‐electron transfer between HRP and the underlying electrode. The biosensor showed an excellent electrocatalytic activity toward the reduction of hydrogen oxide and long‐term stability, owing to the stable electrografted film and biocompatible Au nanoparticles. Our results demonstrate that the combination of electrografting and Au nanoparticles provides a promising platform for the immobilization of biomolecules and analysis of redox enzymes for their sensing applications.     

Pulse shape analysis to reduce the background of BEGe detectors

A simple technique for pulse shape discrimination in HPGe-detectors of the so-called BEGe type, based on just one parameter obtained from one signal read out, is presented here. This technique allows discriminating between pulses generated when the deposited energy is located within a small region of about 1 mm³ from the pulses generated when the energy is deposited at different locations several mm or cm apart. Two possible applications using this technique are: (i) experiments that look for neutrinoless double β decay in ⁷⁶Ge, such as GERDA; (ii) γ spectrometry measurements where the Compton continuum can be reduced and the efficiency for cascading γ-rays can remain high. With this active background reduction technique a Compton suppression factor of about 3 was obtained. The detector response may be influenced by the detector size. The detector used for this study had a diameter of 6 cm, a thickness of 2.6 cm and a relative efficiency of 19%. The results obtained with this detector were consistent with the results obtained by Budjá? et al. [J Instrum 4:10, 2009] with a 50% relative efficiency BEGe detector.     

Elucidating the identity of Anisakis larvae from a broad range of marine fishes from the Yellow Sea,China, using a combined electrophoretic‐sequencing approach

Larval nematodes were collected from marine fishes from the Yellow Sea, China. Specimens (n=1731) of Anisakis type I from 311 fishes (representing 40 species) were each identified based on morphological characters. From the genomic DNA from individual specimens, a region of nuclear ribosomal DNA was amplified by PCR, followed by digestion with restriction endonuclease HinfI, TaqI or HhaI. Subsequently, the ITS‐1 and ITS‐2 regions of selected samples were sequenced. The results revealed three species of Anisakis, namely Anisakis pegreffii (n=1709), A. typica (n=3) and a genotype (n=19) proposed, also based on comparison with previous studies, to be a “hybrid” between A. pegreffii and A. simplex sensu stricto. Thus, A. pegreffii was the dominant species, accounting for 98.7% of the total number of specimens examined herein. This is the first report of A. typica and the “hybrid” genotype from fishes from the Yellow Sea. This study provides important basic information on Anisakis in this region and suggests that the genus Anisakis has substantial host and geographical distributions.