Transport equation on a finite domain II. Reduction to X- and Y-functions

In this article the solution of the time-independent linear transport equation in a finite homogeneous and non-multiplying medium is expressed in Chandrasekhar's X- and Y-functions through the solution of two linear systems of equations of finite order. The existence of the X- and Y-functions is proved in general.     

Thermal characterization of self-assembled monolayers of dialkyl disulfides containing the urea moiety

Thermal behaviors of urea-containing dialkyl disulfides 4-(3-octadecylureido)phenyl disulfide (ODPD) and 3-(octadecylureido)ethane disulfide (ODED) and octadecyl disulfide (ODDS) self-assembled monolayers (SAMs) were investigated by infrared reflection-absorption spectroscopy (IRRAS). Among the SAMs, the alkyl chain of ODPD is thermally reversible in the temperature region between 30 and 138 degrees C, whereas alkyl chains of ODED and ODDS are irreversible. With regard to the thermal stability of alkyl chains, ODED is superior to ODPD and ODDS. It is considered that the good thermal reversibility of the ODPD SAM is due to the rigid phenyl ring and the good thermal stability of the ODED SAM is due to the flexible ethylene linker. Moreover, 2D correlation analysis provides an enhancement of spectral resolution in amide II and CH2 antisymmetric stretching bands and suggests from the comparison of sequences of spectral events of ODPD and ODED SAMs that the last reorientation of the phenyl ring in the ODPD SAM is responsible for the good thermal reversibility.     

pH-induced structural changes of surface immobilized poly(L-lysine) by two-dimensional (2D) infrared correlation study

This paper reports the pH-induced structural changes in the surface immobilized poly(L-lysine)(PLL)film.Two-dimensional(2D) correlation analysis was applied to the Fourier transform infrared(FTIR)spectra of the surface-immobilized PLL film to examine the spectral changes induced by the alternations of the protonation state of the amino group in the side chain.Significant spectral changes in the FTIR spectra of the PLL film were observed between pH 7 and 8.The decrease in the protonation state of the amino group in the side chain induced spectral changes in the amino group as well as conformational changes in the alky]group in the side chain.From pH 1-8,the spectral changes in the amino and alkyl groups in the side chain occurred before those of the amide group in the main chain of the surface immobilized PLL film.     

Inverse Scattering Transform for the Discrete Focusing Nonlinear Schrödinger Equation with Nonvanishing Boundary Conditions

In this article we develop the direct and inverse scattering theory of the Ablowitz-Ladik system with potentials having limits of equal positive modulus at infinity. In particular, we introduce fundamental eigensolutions, Jost solutions, and scattering coefficients, and study their properties.We also discuss the discrete eigenvalues and the corresponding norming constants. We then go on to derive the left Marchenko equations whose solutions solve the inverse scattering problem. We specify the time evolution of the scattering data to solve the initial-value problem of the corresponding integrable discrete nonlinear Schrödinger equation. The one-soliton solution is also discussed.     

Graphene Nanosheets as a Platform for the 2D Ordering of Metal Oxide Nanoparticles: Mesoporous 2D Aggregate of Anatase TiO2 Nanoparticles with Improved Electrode Performance

Graphene nanosheets are successfully applied as an effective platform for the 2D ordering of metal oxide nanoparticles. Mesoporous 2D aggregates of anatase TiO₂ nanoparticles are synthesized by the heat treatment of the uniformly hybridized nanocomposite of layered titanate–reduced graphene oxide (RGO) at elevated temperatures. The precursor layered titanate–RGO nanocomposite is prepared by self‐assembly of anionic RGO nanosheets and cationic TiO₂ nanosols. The calcination of the as‐prepared layered titanate–RGO nanocomposite at 500 °C induces a structural and morphological change of layered titanate nanoplates into anatase TiO₂ nanoparticles without significant modification of the RGO nanosheet. Increasing the heating temperature to 600 °C gives rise to elimination of the RGO component, leading to the formation of sheetlike porous aggregates of RGO‐free TiO₂ nanoparticles. The nanocomposites calcined at 500–700 °C display promising functionality as negative electrodes for lithium ion batteries. Among the present calcined derivatives, the 2D sheet‐shaped aggregate of TiO₂ nanoparticles obtained from calcination at 600 °C delivers the greatest specific discharge capacity with good capacity retention for all current density conditions applied. Such superior electrode performance of the nanocomposite calcined at 600 °C is attributable both to the improved stability of the crystal structure and crystal morphology of titania and to the enhancement of Li⁺ ion transport through the enlargement of mesopores. The present findings clearly demonstrate the usefulness of RGO nanosheets as a platform for 2D‐ordered superstructures of metal oxide nanoparticles with improved electrode performance.     

Anomalous thermal transition and crystallization of ionic liquids confined in graphene multilayers

Anomalous thermal transition and crystallization behaviors of three room temperature ionic liquids (RTILs) in graphene multilayers (GMLs), in a different manner to bulk RTILs, occurred due to the molecular orientation of the confined system triggered by the complex π-π stacking and hydrogen bonding interactions.     

Use of temperature dependent Raman spectra to improve accuracy for analysis of complex oil-based samples: Lube base oils and adulterated olive oils

A simple and effective strategy to improve accuracy for Raman spectroscopic analysis of complex mixture samples by probing a measurement temperature yielding enhanced spectral selectivity has been demonstrated. For the evaluation, the determination of Kinematic Viscosity at 40 °C (KV@40) of lube base oil (LBO) samples was initially attempted. Partial least squares (PLS) was used to determine the KV@40 using Raman spectra of the samples collected at 8 different temperatures from 20 to 90 °C with 10 °C increments. Interestingly, the distinct temperature-induced spectral variation among the samples occurred at 50 °C, thereby resulting in the improved accuracy for determination of KV@40. Two-dimensional (2D) correlation analysis was also performed to find an additional supportive rationale for the improved accuracy. The strategy was further evaluated for the identification of soybean oil-adulterated olive oils using linear discriminant analysis (LDA). Similarly, the discrimination accuracy was improved around 80–90 °C due to the enhanced spectral selectivity between olive and soybean oils. In overall, these two results successfully demonstrate analytical effectiveness of the strategy.     

Excitation wavelength dependent surface-enhanced Raman spectra of a dipping film of azobenzene-containing long-chain fatty acid on a silver mirror

Surface-enhanced Raman scattering (SERS) of dipping films of azobenzene-containing long-chain fatty acids, nAmH (n=8, 12, m=3, 5), on silver mirrors measured with a wide range of excitation wavelengths in the 457.9-1064 nm region is reported. The obtained Raman spectra show great SERS effect even with the 1064 nm excitation, and the excitation with 457.9, 476.5, and 488.0 nm gives surface-enhanced resonance Raman scattering (SERRS) due to the resonance effect of the symmetry-forbidden n-pi* transition of the azo group. Of particular note in the present study is that the SERS spectra with the excitation in the 532-1064 nm region yield Raman bands whose frequencies are almost identical to those bands in Raman spectra of nAmH in solid state while the SERRS spectra with the excitation in the 457.9-514.5 nm region show not only a set of bands which correspond to those of nAmH in the solid state but also a set of bands whose frequencies show a significant shift from those of the bands of nAmH in the solid state. These observations lead us to conclude that there are two kinds of molecular aggregates in the dipping films of azobenzene-containing long-chain fatty acid in which azobenzene moieties are condensed to form small bundles.     

Immune recognition construct plasmonic dimer for SERS‐based bioassay

We have first time demonstrated the construction of a plasmonic gold dimer model for bioassays based on immune recognition with surface‐enhanced Raman scattering (SERS). To induce a strong plasmonic coupling effect, a dimer of gold nanoparticles (NPs) with a Raman label located between adjacent NPs is assembled through specific recognition in biological systems. One promising application for this model is the provision of a new type of in situ self‐calibrated and reliable SERS platform where biotinylated molecules can selectively be trapped by streptavidin and placed in the gap enhanced plasmonic field, which may enable the development of powerful, biospecific recognition‐based SERS assays. The capabilities of the dimeric constructions for analytical applications were demonstrated through the use of the SERS technique to detect biotin at very low concentrations. Additionally, the spatial SERS radiation for the gold dimer assembled on the silicon slide was simulated using the finite‐difference time‐domain method; this simulation demonstrated the distribution of the electric field as well as the utility of the proposed system, thereby introducing potential uses of bio‐specific recognition as well as opportunities for the construction of plasmonically coupled nanostructures and bioassay applications. Copyright © 2013 John Wiley & Sons, Ltd.     

A finite element frequency domain method for 2D photonic crystals

In this paper we propose a new finite element frequency domain (FEFD) method to compute the band spectra of 2D photonic crystals without impurities. Exploiting periodicity to identify discretization points differing by a period, it increases the effectiveness of the algorithm and reduces significantly its computational complexity. The results of an extensive experimentation indicate that our method offers an effective alternative to the most quoted methods in the literature.