Wavelength Of Excitation Source Research Articles

Doping dependence of laser-induced transverse thermoelectric voltages in the perovskite Nd2−x Ce x CuO4 thin films

Large laser-induced thermoelectric voltages (LITVs) are measured in the electron-doped Nd2−x Ce x CuO4 thin films grown on the vicinal-cut SrTiO3 substrates by pulsed laser deposition. The dependence of LITV signals upon the doping carrier density is investigated by changing the Ce content of the films. The optimum Ce dopant corresponding to the largest voltage is found and is attributed to the two-dimensional transport behaviors of the localized electrons. The shorter laser irradiation always induces the larger voltage signals in samples with richer Ce content, suggesting the optimum dopant level is sensitive to the wavelength of excitation source. Thus, the behaviors of LITV signals are resulted from both effects of the anisotropic thermoelectric transport and the optical properties of the thin films. The doping dependence related with an anisotropic charge transport may come from the change in carrier density and the modification in energy band configuration.

Effect of surface coating on optical properties of Eu3+-doped CaMoO4 nanoparticles

A simple polyol method has been used for the synthesis of CaMoO4:Eu (core), CaMoO4:Eu@CaMoO4 (core/shell) and their silica coated CaMoO4:Eu@CaMoO4 (core/shell/shell) nanoparticles. X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), Fourier transform Raman (FT-Raman), Fourier transform infrared (FT-IR), UV/Vis absorption and photoluminescence (PL) spectroscopies techniques has been employed for their characterization. XRD patterns and FT-Raman spectra showed that these nanoparticles have a scheelite-type tetragonal structure without the presence of deleterious phases. These nanoparticles were easily dispersed in water, producing a transparent colloidal solution. The optical energy band-gap decreases after core/shell formation due to increase the crystalline size. The photoluminescence (PL) spectra of the as-synthesized core, core/shell and core/shell/shell nanoparticles measured with an excitation source wavelength of 325nm showed that the emission intensity was increases after shell formation around the surface of core nanoparticles.

LIF Spectroscopy of Fruits: Study of Excitation Wavelength Independence

In fluorescence spectroscopy, fluorescence emissiongenerally occurs from the excited state with the lowest energy. This is known as Kasha's rule and is a general principle with only a few rare exceptions. As a consequence,the emission wavelength is independent of the excitation wavelength. In order to select an appropriate excitation source in fluorescence spectroscopy,it is very important to know the relation between the excitation source wavelength and the emission wavelength. The aim of this paper isto study the excitation-wavelength-independent fluorescence emission of some fruits. To do so, a fluorescence spectrometer controlled by labVIEW software was developed forcollecting the fluorescence spectra ofsome famous fruits.A semiconductor laser and light emitting diodes with different wavelengths was used as the excitation sources.

Triggering and Monitoring Plasmon‐Enhanced Reactions by Optical Nanoantennas Coupled to Photocatalytic Beads

Plasmonic metal/semiconductor nanocomposites promise to be a breakthrough for boosting and investigating photon-assisted processes at the nanoscale, with exciting perspectives for energy conversion and catalysis. However, the efficiency and selectivity of these surface processes are still far from being controlled. Here, shown for the first time, is a new class of photocatalyst which is based on the synergistic combination of bowtie-like gold nanoantennas and SiO2 /TiO2 core/shell oxide beads. These systems are exploited as efficient near-field optical light concentrators, stimulating photon-driven processes at the metal-semiconductor interface. Extraordinary enhancements of photodegradation rates (minutes instead of hours) result from matching the nanoantenna surface plasmon resonance with the optical absorption of organic dyes and the excitation source wavelength. Moreover, strong Raman enhancements are observed allowing for direct in-situ monitoring of reaction progress of different analytes on the same site.

Surface plasmon-enhanced lasing in dye-doped cholesteric liquid crystals

This study shows the results of a photonic band-edge laser using dye-doped cholesteric liquid crystals (CLCs) combined with silver (Ag) nanoparticles. When the Ag nanoparticle surface plasmon resonance wavelength matched the excitation source wavelength, the large optical fields provided by surface plasmons increased the fluorescence of dye molecules by enhancing the molecular excitation rate, achieving a low lasing threshold and high pumping efficiency.

Growth and optical absorption properties of silver nanorod arrays in porous anodic aluminum oxide templates

Silver nanorod arrays have been fabricated by alternating current (AC) and pulsed direct current (DC) electrodeposition in porous anodic aluminum oxide (AAO) templates with controlled pore diameters of 19, 38, and 65 nm, respectively. The variation of their optical absorption properties with the incident angle and the nanorods length (corresponding to the electrodeposition time) has been investigated. Optical absorption spectra show that the position of longitudinal surface plasmon resonance (LSPR) peak has a small blueshift with the increase of incident angle of the excitation light. While the aspect ratio of the nanorods increases, the position of LSPR peak first redshifts and then blueshifts to a certain wavelength. Furthermore, the position of LSPR peak can be tuned, ranging from 550 nm to 900 nm, which makes it possible to couple various wavelength of excitation source to assist radiative energy transfer to the acceptor.

The effect of excitation wavelength on dynamics of laser-produced tin plasma

We investigated the effect of the excitation wavelength on the density evolution of laser-produced tin plasmas, both experimentally and numerically. For producing plasmas, Sn targets were excited with either 10.6 μm CO2 laser or 1.06 μm Nd:yttrium aluminum garnet laser; both are considered to be potential excitation lasers for extreme ultraviolet lithography laser-produced plasma light sources. The electron density of the plasma during the isothermal expansion regime was estimated using an interferometric technique. The Stark broadening of isolated singly-ionized emission was employed for deducing the density during the plasma adiabatic expansion regime. Our results indicate that the excitation source wavelength determines the initial density of the plasma, as well the plume expansion dynamics. Numerical simulation using HEIGHTS simulation package agrees well with the experimentally measured density profile.

Fine particle Sr 2SiO 4:Tb phosphor for the plasma display panel prepared by a combined approach

Sol–gel with microwave heating was employed to prepare fine particles Sr 2SiO 4:Tb phosphor. X-ray diffractometer was used to characterize the structural of the samples. The Scanning Electron Microscope image shows that the particle size is about 300 nm. The phosphor particles have several advantages in the morphology, such as excellent surface quality, spherical shape, and narrow size distribution with no aggregation. The VUV luminescence measurements indicate that the phosphor presents an intense excitation band at 173 nm. Because the wavelength of excitation source in PDP is mainly at 147 and 172 nm, it makes Sr 2SiO 4:Tb a potential candidate for green emitting phosphor for plasma display panel (PDP) application. Photoluminescence (PL) measurements indicate that the Sr 2SiO 4:Tb particles present excellent green emission at 542 and 547 nm excitated at 236 and 172 nm, respectively.

Controlled fabrication of rare earth fluoride superstructures via a simple template-freeroute

A new and simple route to fabricate rare earth metal fluoride superstructureshas been investigated. Typically, doughnut- and shuttle-shapedEuF3 superstructures were controllably synthesized by using sodium tetrafluoroborate(NaBF4) as a fluorine source to react with metal nitrate in aqueous solution under ambientconditions. Scanning electron microscopy (SEM) and transmission electron microscopy(TEM) demonstrated that different superstructures can be obtained by changing theconcentration of the reactants. The photoluminescence (PL) spectra of the as-synthesizedEuF3 measured with an excitation source wavelength of 380 nm showed that the emissionintensity at different wavelengths can be adjusted by changing the morphology ofEuF3. Moreover, our experiments indicated that the fabrication of the rare earth metal fluoridesuperstructures could be readily scaled up to grams.

Complex NAPL Site Characterization Using Fluorescence Part 2: Analysis of Soil Matrix Effects on the Excitation/Emission Matrix

Commercially available cone penetrometer (CPT)fluorescence based sensor platforms have been used to detect non-aqueous phase liquids (NAPLs), such as petroleum oils and lubricants, in situf or more than a decade. These approaches have also been used to detect dense non-aqueous phase liquid (DNAPL) source zones by detecting commingled oilsfuels, and naturally occurring organic materials entrained by DNAPLs and carried to depths below the water table. Several neat NAPLs and mixtureswere added to various soil types and analyzedfor specific fluorescence characteristics to determine the optimal excitation source for site characterization efforts. Using excitationlemission matrices (EEMs), we demonstrate that an optimized excitation wavelength can be determinedfor specific fiuowphores within the NAPL mixtures, and that available systems can be ranked based on the specific contaminant and site soil types. An optimal excitation wavelength yields the maximum fluorescence within an EEM spectrum. We ranked commercially available cone penetrometer fluorescence detection systems according to the potential for ease of detection based on maximum fluorescence response. When soils were added tocomplexNAPLmixtures,analytefluorescence emissionwasattenuatedinpreferential portions of the EEM, leading to differences in the optimal excitation source wavelength. Furthermore, impure silica-containing minerals impact the emission signal, potentially leading to incorrect conclusionsf or several commercially available systems. Our find ings suggest that afrequency-agile (e.g., tunable excitation source) probe system would be superior to any other system commercially available, provided the system would be relatively easy to operate and would have rapid in-situ EEM generating capabilitiesfo r optimization in the field.