Simultaneous determination of methylene blue and new methylene blue by slab optical waveguide spectroscopy and artificial neural networks

A slab optical waveguide (SOWG) has been used for study of adsorption of both methylene blue (MB) and new methylene blue (NMB) in liquid-solid interface. Adsorption characteristics of MB and NMB on both bare SOWG and silanized SOWG by octadecyltrichlorosilane (ODS) were compared. The simultaneous determinations of both MB and NMB were explored by flow injection SOWG spectrophotometric analysis and artificial neural networks (ANNs) for the first time. Concentrations of MB and NMB were estimated simultaneously with the ANNs. Results obtained with SOWG were compared with those got by conventional UV-visible spectrophotometry. (C) 2003 Elsevier Science B.V All rights reserved.

Eutrophication process recorded in dinoflagellate cyst assemblages — a case of Yokohama Port, Tokyo Bay, Japan

To investigate temporal changes of water quality, a role of dinoflagellate cysts preserved in surface sediments was examined in Yokohama Port in Tokyo Bay, Japan. Two cores were collected, and sedimentation rates and ages of both were dated as approximately 1900 years or slightly older on the basis of 210Pb and 137Cs concentrations. The temporal change in dinoflagellate cyst assemblages in the two cores reflects eutrophication in Yokohama Port in the 1960s. Abrupt increases in the cysts of Gyrodinium instriatum cysts strongly suggests that a red tide was caused by this species around 1985. Dinoflagellate cyst assemblages in surface sediments appear to be good biomarkers of changes in the water quality of enclosed seas.

Shallow gas in the muddy sediments of Eckernförde Bay, Germany

The seafloor of central Eckernförde Bay is characterised by soft muddy sediments that contain free methane gas. Bubbles of free gas cause acoustic turbidity which is observed with acoustic remote sensing systems. Repeated surveys with subbottom profiler and side scan sonar revealed an annual period both of depth of the acoustic turbidity and backscatter strength. The effects are delayed by 3–4 months relative to the atmospheric temperature cycle. In addition, prominent pockmarks, partly related to gas seepage, were detected with the acoustic systems. In a direct approach gas concentrations were measured from cores using the gas chromatography technique. From different tests it is concluded that subsampling of a core should start at its base and should be completed as soon as possible, at least within 35 min after core recovery. Comparison of methane concentrations of summer and winter cores revealed no significant seasonal variation. Thus, it is concluded that the temperature and pressure influences upon solubility control the depth variability of acoustic turbidity which is observed with acoustic remote sensing systems. The delay relative to the atmospheric temperature cycle is caused by slow heat transfer through the water column. The atmospheric temperature cycle as ‘exiting function’ for variable gas solubility offers an opportunity for modelling and predicting the depth of the acoustic turbidity. In practice, however, small-scale variations of, e.g., salinity, or gas concentration profile in the sediment impose limits to predictions. In addition, oceanographic influences as mixing in the water column, variable water inflow, etc. are further complications that reduce the reliability of predictions.

An Efficient Nanocrystalline La2O3:Tm3+ Blue Phosphor for Field-Emission Displays with High Color Purity

Nanocrystalline Tm3+-doped La2O3 phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction, field-emission scanning electron microscopy, photoluminescence, and cathodoluminescence spectra were utilized to characterize the synthesized phosphors. Under the excitation of UV light (234 nm) and low-voltage electron beams (1-3 kV), the Tm3+-doped La2O3 phosphors show the characteristic emissions of Tm3+(D-1(2), (1)G(4)-F-3(4), H-3(6) transitions).

Rapid synthesis of polyethylenimine-protected Prussian blue nanocubes through a thermal process

Polyethylenimine (PEI)-protected Prussian blue nanocubes have been simply synthesized by heating an acidic mixture of PEI, FeCl3, K3Fe(CN)(6), and KCI. The experiment results presented here demonstrate that the pH of the mixture plays an important role in controlling the shape and composition of the resultant product.

Layer-by-layer assembly of carbon nanotubes and Prussian blue nanoparticles: A potential tool for biosensing devices

A promising method for assembling carbon nanotubes (CNTs) and poly(diallyldimethylammonium chloride) protected Prussian blue nanoparticles (P-PB) to form three-dimensional (3D) nanostructured films is proposed. The electrostatic interaction, combined with layer-by-layer self-assembly (LBL), between negatively charged CNTs and positively charged P-PB is strong enough to drive the formation of the 3D nanostructured films. Thus, prepared multilayer films were characterized by ultraviolet-visible-near-infrared spectroscopy (UV-vis-NIR), scanning electron microscopy (SEM) and cyclic voltammetry (CV).

Blue-light emission of mesoporous SBA-15 covalently bonded with carbazole chromophore

Much attention has been paid to carbazole derivatives for their potential applications as optical materials. For the first time, the blue-light-emitting carbazole chromophore has been covalently bonded to the ordered mesoporous SBA-15 (The resultant hybrid mesoporous materials are denoted as carbazole-SBA-15) by co-condensation of tetraethoxysilane (TEOS) and prepared compound 3-[N-3-(triethoxyilyl)propyl]ureyl-9-ethyl-carbazole (denoted as carbazole-Si) in the presence of Pluronic P123 surfactant. The results of H-1 NMR and Fourier transform infrared (FTIR) reveal that carbazole-Si has been successfully synthesized.

Investigation on charge transfer bands of Ce4+ in Sr2CeO4 blue phosphor

Bulk and nano-materials Sr2CeO4 were prepared by solid-state reaction and sol-gel technique, respectively. Photoluminescence shows that luminescence has the characteristic of a ligand-to-metal charge transfer (CT) emission. Compared with bulk Sr2CeO4, the nano-material exhibits stronger emission intensity, longer decay time, and higher CT excitation energy. Three CT excitation peaks were observed in both bulk and nano samples.

White Electroluminescence from a Star-Like Polymer with an Orange Emissive Core and Four Blue Emissive Arms

A star-like white light-emitting polymer with an orange emissive core and four blue emissive arms is designed and synthesized. White electroluminescence is observed with simultaneous orange emission from the core and blue emission from the arms. A single-layer device based on this polymer emits white light with CIE coordinates of (0.35, 0.39) and a luminous efficiency of 7.06 cd A(-1).

Blue electroluminescent polymers with dopant-host systems and molecular dispersion features: polyfluorene as the deep blue host and 1,8-naphthalimide derivative units as the light blue dopants

We developed a series of highly efficient blue electroluminescent polymers with dopant-host systems and molecular dispersion features by selecting 1,8-naphthalimide derivatives as the light blue emissive dopant units, choosing polyfluorene as the deep blue emissive polymer host and covalently attaching the dopant units to the side chain of the polymer host. The polymers' EL spectra exhibited both deep blue emission from the polymer host and light blue emission from the dopant units because of the energy transfer and charge trapping from the polymer host to the dopant units.

Realization of blue, green and red emission from top-emitting white organic light-emitting diodes with exterior tunable optical films

We developed an approach to realize blue, green and red emission from top-emitting white organic light-emitting diodes (OLEDs) through depositing exterior tunable optical films on top of the OLEDs. Three primary colors for full color display including blue, green and red emission are achieved by controlling the wavelength-dependent transmittance of the multilayer optical films overlaid on the emissive layer.

Fabrication and electrochemical characterization of electrostatic assembly of polyelectrolyte-functionalized ionic liquid and Prussian blue ultrathin films

Polyelectrolyte-functionalized ionic liquid (PFIL) and Prussian blue (PB) nanoparticles were used to fabricate ultrathin films on the ITO substrate through electrostatic layer-by-layer assembly method. Multilayer growth was examined by UV-vis spectroscopy and cyclic voltammetry. The resulting ITO/(PFIL/PB)n electrode showed two couples of well-defined redox peaks and good electrocatalytical activity towards the reduction of hydrogen peroxide.