Diode-Laser Absorption Measurements of CO(2) Near 2.0 mum at Elevated Temperatures

A diode-laser sensor system based on absorption spectroscopy techniques has been developed for nonintrusive measurements of CO(2) in high-temperature environments. Survey spectra of the CO(2) (20 degrees 1,04 degrees 1)(I)-00 degrees 0 and (20 degrees 1,04 degrees 1)(II)-00 degrees 0 bands between 1.966 and 2.035 mum (4915-5085 cm(-1)) were recorded at temperatures between 296 and 1425 K in a heated static cell and compared with calculated spectra (by using the HITRAN 96/HITEMP database) to find candidate transitions for CO(2) detection. High-resolution measurements of the CO(2) R(56) line shape [(20 degrees 1,04 degrees 1)(II)-00 degrees 0 band] were used to determine the transition line strength, the self-broadening half-width, and the coefficient of temperature dependence of the self-broadening half-width. The results represent what are believed to be the first measurements of CO(2) absorption near 2.0 mum with room-temperature diode lasers. Potential applications of the diode-laser sensor system include in situ combustion measurements and environmental monitoring.     

Difference Frequency Generation of 5-18 mum in a AgGaSe(2) Crystal

Mid-infrared radiation in the 5-18-mum range has been obtained by difference frequency generation in a AgGaSe(2) crystal by pumping with the output of a type I LiNbO(3) optical parametric oscillator (OPO). Here we suggest the use of a LiTaO(3) retarder to achieve an orthogonal state of polarization between OPO outputs that are necessary for efficient pumping of a AgGaSe(2) crystal. Several tens of kilowatts of peak power near 8 mum and continuously tunable operation in the above range have been obtained.     

Simple and rapid synthesis of core-shell SiO2/Mg(OH)2 spheres under ambient conditions

The core-shell SiO₂/Mg(OH)₂ spheres were synthesized under ambient conditions, with the aid of polyethylene glycol (PEG) and sodium dodecyl benzene sulfonate (SDBS) to modify the morphology and dispersion of the products. The solid and hollow core-shell SiO₂/Mg(OH)₂ spheres with different morphologies, such as convex-pointed, gyrus-like and honeycombed, controlled by the ratio of silica and magnesium chloride, were obtained and investigated by means of XRD, EDS, TEM and SEM. The formation mechanism of core-shell SiO₂/Mg(OH)₂ structure was discussed in detail.     

Spatial beam cleanup of a Nd:YAG laser operating at 1.06 mum with two-wave mixing in Rh:BaTiO(3)

Spatial beam cleanup of a distorted cw Nd:YAG laser operating at lambda = 1.06 mum is demonstrated with two-wave mixing in an infrared-sensitive rhodium-doped barium titanate crystal. Because of the high coupling gain of our crystal, high efficiencies are achieved in agreement with the standard photorefractive model.     

Mie scattering interferometer and its application to the study of Raman scattering from molecules at a mercury interface

Interference fringes are observed produced by Mie scattering of laser light from a single microstructure or from a random array of microstructures supported above a reflecting surface. These fringes are the basis of a simple interferometer which can be used to measure distances from thousands of angstroms to centimeters. The interferometer is used to measure the height of liquid above a mercury surface. Raman scattering (RS) from the liquid is measured, and an upper limit of 10(3) is placed on the enhancement of RS from molecules at the interface. Enhancement of RS in a wedge between mercury and solid is examined theoretically.     

Temperature changes of the optical properties of (SiO2) n , (GaAs) m , and (SiO2) n (GaAs) m nanoparticles: Computer experiment

The optical properties of silicon dioxide and gallium arsenide nanoparticles and the four-component particles based on them were calculated by the molecular dynamics method. The complex dielectric permittivity, infrared and Raman spectra, refractive index, and absorption coefficient of these nano particles were determined. The temperature dependences of the infrared and Raman spectra and the number of the optically active electrons in the nanoparticles composed of a semiconductor and/or a dielectric were investigated.     

Facile synthesis,phase transition,optical switching and oxidation resistance properties of belt-like VO2(A) and VO2(M) with a rectangular cross section

Belt-like VO₂(A) with a rectangular cross section (VA-RCS) was successfully synthesized using V₂O₅, H₂C₂O₄·2H₂O and H₂O as the starting materials by a facile hydrothermal approach. Some synthetic parameters, such as, the reaction time, reaction temperature and concentration of H₂C₂O₄·2H₂O, were systematically investigated to control the fabrication of belt-like VA-RCS. The formation mechanism of belt-like VA-RCS was proposed. Subsequently, belt-like VO₂(M) with a rectangular cross section (VM-RCS) was prepared by the irreversible transformation of VA-RCS at 700 °C for 2 h under the inert atmosphere. The phase transition temperature (T_c) of VA-RCS and VM-RCS was evaluated by DSC test. The optical switching properties of VA-RCS and VM-RCS were studied by the variable-temperature infrared spectra, and it was found that the as-obtained VA-RCS and VM-RCS could be used as the optical switching materials. Furthermore, the oxidation resistance properties of VA-RCS and VM-RCS were investigated by TGA, indicating that they have good thermal stability and oxidation resistance below 400 °C in air.     

In Situ Combustion Measurements of CO(2) by Use of a Distributed-Feedback Diode-Laser Sensor Near 2.0 mum

High-resolution absorption measurements of CO(2) were made in a heated static cell and in the combustion region above a flat-flame burner for the development of an in situ CO(2) combustion diagnostic based on a distributed-feedback diode laser operating near 2.0 mum. Calculated absorption spectra of high-temperature H(2)O and CO(2) were used to find candidate transitions for CO(2) detection, and the R(50) transition at 1.997 mum (the nu(1) + 2nu(2) + nu(3) band) was selected on the basis of its line strength and its isolation from interfering high-temperature water absorption. Measurements of spectroscopic parameters such as the line strength, the self-broadening coefficient, and the line position were made for the R(50) transition, and an improved value for the line strength is reported. The combustion-product populations of CO(2) in the combustion region above a flat-flame burner were determined in situ to verify the measured spectroscopic parameters and to demonstrate the feasibility of the diode-laser sensor.     

Large-area vapor-phase growth and characterization of MoS(2) atomic layers on a SiO(2) substrate

Atomic-layered MoS(2) is synthesized directly on SiO(2) substrates by a scalable chemical vapor deposition method. The large-scale synthesis of an atomic-layered semiconductor directly on a dielectric layer paves the way for many facile device fabrication possibilities, expanding the important family of useful mono- or few-layer materials that possess exceptional properties, such as graphene and hexagonal boron nitride (h-BN).     

Synthesis of Sb2E3 (E = S, Se) nanorods with a flat cross section by a rapid hot injection method

We report herein a simple colloidal synthesis route, i.e., rapid injection of E (E = S, Se) source into a hot solvent (1-octadecence, ODE) containing antimony precursor (antimony stearate), to grow Sb2E3 nanorods. The as-prepared nanorods were extensively characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM). The mechanism for growth of Sb2E3 nanorods was also clarified from the view of crystal structure-directed growth. We believe that the method present here is a more straightforward and cost-effective route to prepare Sb2E3 nanocrystals with high quality.     

The two-photon excitation of SiO(2)-coated Y(2)O(3):Eu(3+) nanoparticles by a near-infrared femtosecond laser

In order to improve the photoluminescence property of Eu(3+)-doped nanoparticles, Y(2)O(3):Eu(3+) nanoparticles were synthesized using the Pechini-type sol-gel method, then coated with SiO(2) shells by using the St?ber method for different coating times. The SiO(2)-coated nanoparticles were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy, and their photoluminescence spectra were recorded under 800?nm femtosecond laser excitation. The results indicate that a two-photon simultaneous absorption upconversion luminescence is obtained, and their upconversion luminescence intensities are further enhanced after the surfaces of the nanoparticles are coated with different thickness SiO(2) shells. Compared to the upconversion luminescence intensity of non-coated nanoparticles at 611?nm, the upconversion luminescence intensities of SiO(2)-coated Y(2)O(3):Eu(3+) nanoparticles with coating times of 60, 90 and 120?min were enhanced by 3.30, 3.96 and 4.13 times, respectively. This can be attributed to the contributions of the increased amounts of Eu(3+) ions populated at the (5)D(0) level on the surfaces of the nanoparticles because the cooperative ligand fields between the Y(2)O(3) core and non-crystalline SiO(2) shell interfaces activate the 'dormant' Eu(3+) ions near or on the surfaces of the nanoparticles. From a Judd-Ofelt (J-O) theory analysis, the coated shell structures can improve the radiative quantum efficiencies of Eu(3+)-doped nanoparticles. It is therefore concluded that more intense red upconversion luminescence with high radiative quantum efficiencies can enable the SiO(2)-coated Y(2)O(3):Eu(3+) nanoparticles to have the great potential to be used as a fine resolution phosphor.     

Diffraction theory: application of the fast Fourier factorization to cylindrical devices with arbitrary cross section lighted in conical mounting

The differential theory of diffraction by arbitrary cross-section cylindrical objects is developed for the most general case of an incident field with a wave vector outside the cross-section plane of the object. The fast Fourier factorization technique recently developed for studying gratings is generalized to anisotropic and/or inhomogeneous media described in cylindrical coordinates; thus the Maxwell equations are reduced to a first-order differential set well suited for numerical computation. The resolution of the boundary-value problem, including an adapted S-matrix propagation algorithm, is explained in detail for the case of an isotropic medium. Numerical applications show the capabilities of the method for resolving complex diffraction problems. The method and its numerical implementation are validated through comparisons with the well-established multipole method.     

Diffraction theory in TM polarization: application of the fast Fourier factorization method to cylindrical devices with arbitrary cross section

The diffraction of an electromagnetic wave by a cylindrical object with arbitrary cross section is studied by taking advantage of recent progress in grating theories. The fast Fourier factorization method previously developed in Cartesian coordinates is extended to cylindrical coordinates thanks to the periodicity of both the diffracting object and the incident wave with respect to the polar angle theta. Thus Maxwell equations in a truncated Fourier space are derived and separated in TE and TM polarization cases. The new set of equations for TM polarization is resolved numerically with the S-matrix propagation algorithm. Examples of elliptic cross sections and cross sections including couples of nonconcentric circles show fast convergence of the results, for both dielectric and metallic materials, as well as good agreement with previous published results. Thus the method is suitable for an extension to conical (out-of-plane) diffraction, which will allow studying mode propagation along microstructured fibers.     

Niobium(V) oxide (Nb2O5): application to phosphoproteomics

Proteomics-based analysis of signaling cascades relies on a growing suite of affinity resins and methods aimed at efficient enrichment of phosphorylated peptides from complex biological mixtures. Given the heterogeneity of phosphopeptides and the overlap in chemical properties between phospho- and unmodified peptides, it is likely that the use of multiple resins will provide the best combination of specificity, yield, and coverage for large-scale proteomics studies. Recently titanium and zirconium dioxides have been used successfully for enrichment of phosphopeptides. Here we report the first demonstration that niobium pentoxide (Nb 2O 5) provides for efficient enrichment and recovery ( approximately 50-100%) of phosphopeptides from simple mixtures and facilitates identification of several hundred putative sites of phosphorylation from cell lysate. Comparison of phosphorylated peptides identified from Nb 2O 5 and TiO 2 with sequences in the PhosphoELM database suggests a useful degree of divergence in the selectivity of these metal oxide resins. Collectively our data indicate that Nb 2O 5 provides efficient enrichment for phosphopeptides and offers a complementary approach for large-scale phosphoproteomics studies.     

Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS): a review of applications

Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS) can provide positive identification of an analyte or an analyte mixture with high sensitivity and selectivity. Better understanding of the theory and advances in the understanding of the practice have led to the development of practical applications in which the unique advantages of SERS/SERRS have been used to provide effective solutions to difficult analytical problems. This review presents a basic theory and illustrates the way in which SERS/SERRS has been developed for practical use.     

Extraction of chemical information of suspensions using radiative transfer theory to remove multiple scattering effects: application to a model multicomponent system

The effectiveness of a scatter correction approach based on decoupling absorption and scattering effects through the use of the radiative transfer theory to invert a suitable set of measurements is studied by considering a model multicomponent suspension. The method was used in conjunction with partial least-squares regression to build calibration models for estimating the concentration of two types of analytes: an absorbing (nonscattering) species and a particulate (absorbing and scattering) species. The performances of the models built by this approach were compared with those obtained by applying empirical scatter correction approaches to diffuse reflectance, diffuse transmittance, and collimated transmittance measurements. It was found that the method provided appreciable improvement in model performance for the prediction of both types of analytes. The study indicates that, as long as the bulk absorption spectra are accurately extracted, no further empirical preprocessing to remove light scattering effects is required.     

Direct pattern recognition of a motion picture by hole-burning holography of Eu(3+):Y(2)SiO(5)

We propose and demonstrate a novel technique for direct pattern recognition of motion pictures based on frequency- and spatial-domain holography using a cryogenic Eu(3+):Y(2)SiO(5) crystal. The fast hole-burning speed of the crystal allows a moving image to be continuously recorded in it by a frequency-scanned laser. Using Fourier transform holography permitted direct pattern recognition of a 25-s movie stored in the crystal to be realized. The correlation spot continuously followed the moving object with the same time resolution (10 ms) as the reproduced movie.     

Catalytic effect of nanogold on Cu(II)-N2H4 reaction and its application to resonance scattering immunoassay

In the medium of EDTA-NaOH, nanogold strongly catalyzed the slow reaction between hydrazine (N2H4) and Cu(II) to form Cu particles, which exhibited a strong resonance scattering (RS) peak at 602 nm. The increased RS intensity at 602 nm (DeltaI(RS)) was linear to the nanogold concentration in the range of 0.008-2.64 nM, with a detection limit of 1.0 pM Au. The rate equation obtained by the initial rate procedure was V(Cu) = K(Cu)[C(Cu(II))](2)C(OH)(1)C(Au)(1)C(N2)H4(1), with an apparent activation energy of 38 kJ x mol(-1), and the catalytic reaction mechanism was also discussed. An immunonanogold-catalytic resonance scattering spectral (RSS) assay was established for detection of microalbumin (Malb), using 10 nm nanogold to label goat antihuman Malb to obtain an immunonanogold probe (AuMalb) for Malb. In pH 5.0 citric acid-Na2HPO4 buffer solution, the AuMalb aggregated nonspecifically. Upon addition of Malb, it reacted with the probe to form dispersive AuMalb-Malb immunocomplex in the solution. After centrifugation, the supernatant containing AuMalb-Malb was obtained, and exhibited a catalytic effect on the reaction of N2H4-Cu(II) to produce large Cu particles that resulted in the I(602 nm) increasing. The increased RS intensity at 602 nm (DeltaI(602 nm)) was linear to Malb concentration (C(Malb)) in the range of 0.4 to 460 pg x mL(-1), with the regression equation of DeltaI(602 nm) = 0.3713 C(Malb) + 7.2, correlation coefficient of 0.9981 and detection limit of 0.1 pg x mL(-1) Malb. The proposed method was applied to detect Malb in healthy human urine samples, with satisfactory results.     

Magnesium catalyzed growth of SiO(2) hierarchical nanostructures by a thermal evaporation process

SiO(2) hierarchical nanostructures consisting of a wire-like main stem and lots of rod-like sub-branches have been synthesized by a magnesium catalyzed thermal evaporation process. It?is indicated that magnesium plays a critical role in the synthesis of SiO(2) hierarchical nanostructures including promotion for SiO evaporation and hierarchical-like growth of SiO(2). Moreover, the photoluminescence (PL) analysis of the SiO(2) hierarchical nanostructures reveals that blue and ultraviolet (UV) emissions are detected, which are different from those of other SiO(2) nanostructures. Finally, the growth mechanism and PL emission of SiO(2) hierarchical nanostructures have been preliminarily discussed.     

Depth profiles and concentration percentages of SiO2 and SiO x induced by ion bombardment of a silicon (100) target

Very thin-film of silicone oxide is of importance in many microelectronics device fabrication. A 9 keV Ar⁺ beam was applied to bombard a silicon (100) target ambient oxygen gas. The measurement was performed with a fixed time of bombardment but different oxygen pressure, beam intensity and temperature. An X-ray Photoelectron Spectroscopy (XPS) was employed to analyze the depth profiles and the concentration percentages of SiO₂ and SiO _x within the bombarded Si (100) samples. The percentage of SiO₂ in different depth of the sample is found to be proportional to the oxygen pressure. The thickness of SiO₂ film formed at room temperature is larger than the thickness at temperature 650 °C. The net percentages of SiO _x , except at the top layer of the surface, are varied in a small difference among different ion-bombardment conditions as the depth below 2 nm.