Surface plasmon resonance and surface-enhanced Raman scattering activity of SiO2–Au core-cap nanostructure arrays

SiO₂–Au core-cap nanostructure arrays were prepared by dip-coating technique combined with wet chemical reduction method. The surface morphologies, structures, and optical properties of the obtained samples were characterized by scanning electron microscopy, X-ray diffraction, and ultraviolet–visible spectrophotometer, respectively. The surface-enhanced Raman scattering (SERS) activity of SiO₂–Au core-cap nanostructure arrays substrates was investigated using leucine as probe molecule. And the relationship between the SERS effect and the surface plasmon resonance (SPR) peaks was discussed. High-quality, stable, and reproducible SERS spectra of leucine were successfully obtained. When the maximum SPR peak matched with the excitation wavelength, the substrate gave rise to the highest SERS enhancement. Furthermore, six different fluorescent dyes were also chosen as probe molecules. It was found that the substrate showed good Raman enhancement and highly efficient fluorescence quenching characteristic on these fluorescent dyes.     

Radiative lifetimes of some energy levels of doubly ionized Xenon

Using 1–5 MeV Xenon ions we have studied the beam-foil spectrum of Xenon between 105 nm and 500 nm. Radiative lifetimes were measured for levels of Xenon III. For those lifetimes which have been measured previously (Andersen et al. [l]) good agreement is obtained. The interpretation of the decay curves and the assignment of a measured value, were done with the help of theoretical lifetimes obtained by Coulomb-approximation calculations [2].     

The KLL Auger spectrum of fluorine

The KLL Auger spectrum of fluorine (Z=9) has been studied in three different fluoride salts. Five Auger lines are observed in each compound in accordance with extreme LS coupling theory. A cation dependence of the Auger transition energies and line-widths is observed. The energy shifts are in agreement with a theoretical model.     

THz photomixer with milled nanoelectrodes on LT-GaAs

A terahertz (THz) photomixer: (i) a meander type antenna with integrated nanoelectrodes on (ii) a low temperature grown GaAs has been fabricated and characterized. It was designed for spectral range of 0.3–0.4 THz where molecular fingerprinting and sensing are performed. By combination of electron beam lithography with post-processing using focused ion beam (FIB), milling the THz emitter was successfully fabricated. Nanogaps as small as 40 nm width in the active area of photomixer were milled by FIB. Nanocontacts enhance electric fields of the illuminated and THz radiation and contribute to a better collection of photo-electrons. THz emission was obtained and spectrally characterized.     

Optimized AC conductivity correlated to structure,morphology and thermal properties of PVDF/PVA/Nafion composites

Polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA) composites were prepared by controlled loading of Nafion (5 to 15 wt%) by solution casting using water and dimethylformamide (DMF) as a solvent. The surface morphology of composite analyzed by atomic force microscopy (AFM) reveals the presence of Nafion ionomers. The increase in interlayer spacing of modified PVDF/PVA polymer system as a function of Nafion was detected by X-ray diffraction (XRD). The major change in Fourier transform infrared (FTIR) spectroscopy confirms the chemical bond C=O stretching around 1,700 cm^?1 due to Nafion. Differential scanning calorimetry (DSC) demonstrates the thermal stability of polymer composites and the decrease in melting temperature (T _m). The optimized AC conductivity (σ) of the prepared composite was evaluated by using an impedance analyzer as a function of temperature (40 to 150 °C) at constant 30-MHz frequency. The highest conductivity of 1.3?×?10^?2 S m^?1 was observed at 80 °C for 10 wt% of Nafion and correlated with structure, morphology and thermal properties of modified PVDF/PVA/Nafion composites. The experimental results may be useful for sensors, fuel cells and battery application domains.     

Luminescent properties of Eu2+ ions in AlN at low and high intensity of excitation

Luminescent properties of powder AlN∶Eu²⁺ phosphors were studied by excitation of 2-nd harmonic of ruby laser (hv=3·56 eV). It was shown that emission spectra of AlN∶Eu²⁺ phosphors consist of five or two overlapping bands according to the concentration of europium and the intensity of excitation. Decay times of luminescence of Eu²⁺ centres in different peaks lie between 0·9 and 1·5 μsec which is in agreement with the value of decay time of 4f⁶ 5d→47⁷ transition of Eu²⁺ ions. It is evident from the decomposition of emission spectra of Eu²⁺ centres that there exist several types of Eu²⁺ centres in AlN as was already demonstrated in the case of oxygen centres in AlN.     

System design considerations for precision measurement of high magnetic fields by Faraday effect

Practical and technical considerations for an instrument designed to measure high magnetic fields by Faraday effect are given. Magnetic fields up to 2 Tesla were measured and the results compared to those of Nuclear Magnetic Resonance technique. Results of measurements at low temperatures are also reported.     

An in silico protocol for identifying mTOR inhibitors from natural products

The mammalian target of rapamycin (mTOR) is an anti-cancer target. In this study, we propose an in silico protocol for identifying mTOR inhibitors from the ZINC natural product database. First, a three-dimensional quantitative structure–activity relationship pharmacophore model was built based on known mTOR inhibitors. The model was validated with an external test set, Fischer’s randomization method, a decoy set and pharmacophore mapping conformation testing. The results showed that the model can predict the mTOR inhibition activity of the tested compounds. Virtual screening was performed based on the best pharmacophore model, and the results were then filtered using a molecular docking approach. In addition, molecular mechanics/generalized born surface area analysis was used to refine the selected candidates. The top 20 natural products were selected as potential mTOR inhibitors, and their structural scaffolds could serve as building blocks in designing drug-like molecules for mTOR inhibition.     

Double-walled core-shell structured Si@SiO2@C nanocomposite as anode for lithium-ion batteries

Double-walled core-shell structured Si@SiO₂@C nanocomposite has been prepared by calcination of silicon nanoparticles in air and subsequent carbon coating. The obtained Si@SiO₂@C nanocomposite demonstrates a reversible specific capacity of about 786 mAh g^?1 after 100 cycles at a current density of 100 mA g^?1 with a capacity fading of 0.13 % per cycle. The enhanced electrochemical performance can be due to that the double walls of carbon and SiO₂ improve the electronic conductivity and enhance the compatibility of electrode materials and electrolyte as a result of accommodating the significant volumetric change during cycles. The interlayer SiO₂ may release the mechanical strain and enhance the interfacial adhesion between carbon shell and silicon core.     

A comparative study of the dopant profiles in diffused planar optical waveguides by SIMS and guided wave probe

A technique has been developed for dopant concentration depth profiling using static Secondary Ion Mass Spectrometry (SIMS), and an ex-situ ion milling facility to produce “tapers” through the region of interest of an optical waveguide sample. Results have been obtained for titanium-diffused optical waveguides in lithium niobate and for potassium and caesium ion-exchanged glass waveguides. The SIMS profiles have been compared with refractive index profiles in multimode structures. The refractive index profiles have been obtained from the waveguide mode spectra by a piecewise linear Wentzel-Kramers-Brillouin (WKB) method. The two profiles are in close agreement. Use of the SIMS technique for single mode Ti∶LiNbO₃ waveguides has revealed significant changes in the forms of the profiles, compared with deeper structures, and we suggest a mechanism to account for these changes.     

SERS scaling rules

We demonstrate the qualitative analysis of surface-enhanced Raman scattering (SERS) intensity and optical extinction by experimentally and numerically. This analytical methods are well matched not only the simple square lattice array of nanostructures, but also the rectangular lattices. We also demonstrate SERS selectivity of modes controlling the optical extinction of excitation and scattering wavelength. Both square lattice and rectangular lattice have similar tendency, but the rectangular lattice structures have much higher selectivity of SERS modes.     

Heat capacity of oxides in the Bi2O3-SiO2 system

The high-temperature heat capacity of Bi₄Si₃O₁₂, Bi₂SiO₅, and Bi₁₂SiO₂₀ has been investigated. It has been found that there is a correlation between the specific heat C _p ⁰ (298 K) and the composition of oxides in the Bi₂O₃-SiO₂ system.     

Methods of IR spectroscopy in monitoring of chemotherapy of oncological pathologies using palladium complexes

FTIR spectroscopy is used to study mammary-gland tissues of mice with a sarcoma tumor (strain 180). Spectral features that are typical of malignant tumors are revealed in the FTIR spectra in the sarcoma-tumor tissues. Tumor tissues are studied after treatment using coordination compounds based on palladium complexes with 3-amino-1-hydroxypropylidene-1,1-diphosphonic acid and zoledronic acid. A therapeutic effect is not revealed after treatment using palladium complex with 3-amino-1-hydroxypropylidene-1,1-diphosphonic acid. The suppression of tumor growth amounts to 59% when palladium complexes with zoledronic acid are used. Suppression of tumor growth is accompanied by variations in spectral characteristics. With respect to diagnostic features, the FTIR spectra of tumor tissues after treatment with the palladium complexes with zoledronic acid are similar to the FTIR spectra of tissues that are free of malignant tumors. Specific spectroscopic characteristics that make it possible to control the chemotherapy of oncological pathologies are determined.     

Two dimension photonic crystal Y-branch beam splitter with variation of splitting ratio based on hybrid defect controlled

This article represents a new Y-branch hybrid design of 2D photonic crystal with defect control. The structure is made of hexagonal arrays of InP nano-rods surrounded by air. This system is comprised of a modified add/change to a polymethylmethacrylate (PMMA) rod, which can be applied to the beam splitter selection device. The optical properties and radial of PMMA defect rods have been transfigured. By selecting an appropriate temperature, a change of refractive index and expanded radius are occurred. The obtained results have shown that the selected optical amplitude in a hybrid semiconductor-polymer Y-branch can be separated to 50–50, 60–40 and 67–33 % at wavelength 1.557 µm. Both of the photonic band gap and transmission spectra are calculated by using 2D finite different time domain (FDTD) method via OptiFDTD software. Such a device can be useful for photonic crystal switching devices in the integrated optical circuit.     

Passivation of InAs/GaSb type II superlattice photodiodes

One of the major challenges faced by antimonide-based devices is a result of the large number of surface states that are generated. Surface passivation and subsequent capping of the surfaces are essential for any practical applicability of this material system, as evidenced by the comparison of unpassivated and passivated InAs/GaSb superlattice mid-infrared photodiodes herein. The surface passivation methods include silicon dioxide (SiO₂) coating after anodic sulfide, SiO₂ coating after anodic oxide, SiO₂ coating only, zinc sulfide (ZnS) coating after anodic sulfide, and ZnS coating after ammonium sulfide [(NH₄)₂S] chemical passivation. The leakage current as a function of bias voltage (I–V) for superlattice diodes obtained using different passivation methods has been examined at 77 K. The best performance was demonstrated by the SiO₂ after anodic sulfide passivation. The leakage current of the passivated diode is four orders of magnitudes less than that of the unpassivated diode.     

TheK Auger spectrum of the free magnesium atom

TheK Auger spectrum of free Mg atoms has been investigated with an electrostatic energy analyzer at an energy resolution of 0.16%. The ionization in theK shell of the Mg vapour was caused by electron impact. Absolute energies and relative intensities of the normal Auger transitionsK-LL and of the most intense satellite lines have been determined. The experimental energies and relative group intensities of the normal lines agree well with theoretical values. The total intensity of special classes of satellites are compatible with calculations of the shake theory within the sudden approximation.     

Searches for fractional electric charge in meteorite samples

The magnetic levitation technique has been used to test for fractional electric charge on samples of several types of meteorite material, thus providing the first mass-independent search for free quarks or other fractionally-charged particles in natural nonterrestrial materials. The tests were made on diced samples of the Hoba and Forsyth County iron-nickel meteorites, and the Murchison stony meteorite, the latter being plated with iron to allow magnetic levitation. No evidence for fractional charge was found, the quantities tested being 1.3 mg (Hoba), 1.1 mg (Forsyth), and 0.4 mg (Murchison).     

On the theory of electron diffusion under a temperature gradient in degenerate semiconductors having non-parabolic energy bands

The theory of electron diffusion under a temperature gradient (Soret effect) in degenerate semiconductors having non-parabolic energy bands and spherical constant-energy surfaces is worked out for the first time. An expression is given for the Soret coefficient which may be determined from the knowledge of the energy dependence of the relaxation time and can be related to the thermoelectric power.     

Luminescence of poly(N-vinylcarbazole) in the solution and solid state

Fluorescence spectra of poly(N-vinylcarbazole) have been studied as a function of various environments and temperature. Fluorescence spectra have been excited with UV light from 200 W Xenon lamp or with second-harmonics of a pulsed ruby laser. Polymer films and powders show exclusively excimer fluorescence at room temperature. At high intensities of excitation the observed fluorescence spectra have a weak quasiperiodic structure.