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Upconversion photoluminescence can eliminate problems associated with autofluorescence and scattered excitation light in homogeneous luminescence-based assays without need for temporal resolution. We have demonstrated a luminescence resonance energy-transfer-based assay utilizing inorganic upconverting (UPC) lanthanide phosphor as a donor and fuorescent protein as an acceptor. UPC phosphors are excited at near-infrared and they have narrow-banded anti-Stokes emission at visible wavelengths enabling measurement of the proximity-dependent sensitized emission with minimal background. The acceptor alone does not generate any direct emission at shorter wavelengths under near-infrared excitation. A competitive model assay for biotin was constructed using streptavidin-conjugated [Er.sup.3+], [Yb.sup.3+]-doped UPC phosphor as a donor and biotinylated phycobiliprotein as an acceptor. UPC phosphor was excited at near-infrared (980 nm) and sensitized acceptor emission was measured at red wavelength (600 nm) by using a microtitration plate fluorometer equipped with an infrared laser diode and suitable excitation and emission filters. Lower limit of detection was in the subnanomolar concentration range. Compared to time-resolved fluorometry, the developed assay technology enabled simplified instrumentation. Excitation at near-infrared and emission at red wavelengths render the technology also suitable to analysis of strongly colored and fluorescent samples, which are often of concern in clinical immunoassays and in high-throughput screening.

A new study investigates the degradation of ZnS and Y2O2S cathodoluminescent phosphors at 1-4 keV.

A new study investigates the leakage current mechanism in a blue-light emitting SrS:Cu, Cl electroluminescent phosphor.

EL spectra of SnS and SRs ACTFEL devices was compared to assess the relative high field transport efficiency and short wavelength electroluminescence potential of ZnS and SrS for alternating-current thin-film electroluminescent devices.

The use of fluorimetric and diffuse reflectance measurements on the isomorphous series alpha-CuAlBrxCl4-x ( x = 0-4) to investigate the electronic structure of CuAlCl4 is described. Alpha- and beta-CuAlCl4 phases demonstrate luminescence of brilliant blue to blue-green.

Synthesis of novel chiral indolyl-oxazaphosphorines has been carried out. Evaluation of their potential as chiral phosphorothioates precursors has been made.

Research was conducted to examine the determination of the Ce+3 bonding in the Ca0.5Sr0.5Ga2S4:Ce phosphor via x-ray photoelectron spectroscopy. The addition of oxygen in the phosphor was observed to nearly double the luminance and to blue shift the emission spectrum of the Ce+3 4f-5d transition. SCF/CI potential energy surface calculations and thermodynamic data revealed that the formation of Ce-O bonds are favored over Ce-Sd, Sr-O or Ca-O bonds.

A study on the use of high quality phosphor such as ZnS for a variety of applications relating to electroluminescence presents the time-dependent, current-voltage, electrical conduction characteristics of ZnS:Pr, Ce, Mn layers prepared with various post-deposition treatments. The surface roughness of ZnS:Pr, Ce films parallel to the glass substrate and the high peak-to-valley resulting from hillock formation in the 60 min annealed film were assumed to be the main sources of difference at initial direct current voltage characteristics and the fluctuations with time.

The influence of radiation transport on the kinetics of phosphor degradation was studied by assuming that the values of the rate constants are related to the ultraviolet surface intensity. The results showed that phosphor degradation was a function of discharge properties and the time elapsed. The findings also underscored the significance of knowing the distinction between optical properties of the phosphor layer and the natural material characteristics.

A study relating to research on subphthalocyanines as materials for nonlinear optical applications was conducted to investigate the photochemical and photophysical behavior of a perfluorinated subphthalocyanine, namely, (dodecafluorosubphthalocyanaoto)boron(III) chloride in room temperature solutions. Among other results, it was found that this subphthalocyanine has a highly luminescent singlet excited state that is a powerful one-electron oxidant.

We present results from an ongoing search for inorganic scintillators for x- and gamma- ray detection. We measure the scintillation properties (luminous efficiency, decay time, and emission wavelength) of powdered samples excited by brief x-ray pulses. To find scintillators that are compatible with silicon photodetectors, we have tested over 1,100 samples using a photomultiplier tube with a GaAs:Cs photocathode, which is sensitive to 200-950 nm emissions. Optical filters are used to block emissions that are observable with bialkali PMTs. Several lanthanide and transition metal ions, molecular complexes, and II-VI compounds are known to have strong emissions at wavelengths >500 nm. We find that several compounds exhibit emission intensities comparable to commercial phosphors in the 600-900 nm range, including Eu and Sm doped LuP[O.sub.4], ScP[O.sub.4], and YP[O.sub.4]. Significant emissions are also observed from Tb, Dy, Er, Pr, and Tm doped phosphates, as well as several intrinsic compounds, notably [Hg.sub.2][Cl.sub.2]. Scintillation characteristics of promising compounds (in powdered or small crystal form) are presented.

Research was conducted to show that the residual gases in a field-emission display (FED) device are essential to the performance and lifetime of ZnS phosphor screens. Auger electron spectroscopy combined with cathodoluminescence (CL) were used to monitor the surface reactions and degraded luminescence intensity caused by electron bombardment at different residual gas pressures and gas compositions. Results indicate that electron-stimulated surface chemical reactions on ZnS cause the degradation of the FED phosphor and subsequent loss of CL intensity.

A model was developed to analyze and define the properties of an energy transfer from luminescent porous silicon (p-Si) to adsorbed osmium(II) and ruthenium(II) polypyridyl complex compounds. The complex's surface adsorption on p-Si wafers quenched the emission. Facile energy transfer shifts from the surface to Ru(II) and Os(II) complexes. Such transfer is faster and more efficient for Os(II) than for Ru(II).

Research was conducted to examine the usefulness of two types of storage phosphors, KCl:Eu and BaFBr:Eu, for soft x-ray imaging diagnostics. The dependencies of the phosphor structure on the spatial resolution and sensitivity were studied at 0.15 nm. Results indicate that it is possible to create storage phosphor detectors with high spatial resolution by using polycrystalline layers composed of small grains and by using single crystals.

Four types of phosphors were subjected to in situ reflectivity measurements to determine the effects of electron beam exposure on the said compound. Results acquired from Raman scattering and optical analysis shows that a contaminating overlayer is created due to the electron-beam-stimulated conversion of hydrocarbons. This results to a significant decline in cathodoluminescence for voltages below 1.5-2 keV.

The electron paramagnetic resonance and the electron nuclear double resonance spectra of x-ray storage phosphors Cs2NaYF6:Ce3+ and Pr3+ are used to analyze properties of the said crystals, particularly their storage and read out process. Results show that the photostimulable electron center of the phosphors is an F center. In x irradiation cases, only F centers and Pr4+ are involved in information storage and readout.

Measurement of surface potential shifts involving secondary and Auger electron spectra for low voltage display phosphors showed strongly negative charges higher than 2 keV. Coincident electron beam measurements indicated aging-enhanced surface charging to reduce phosphor cathodoluminescence. These results indicated substantial space charge for phosphors, even for low energy levels.

New polymetallic complexes have been made with 1,4,5,8,9,12-hexaazatriphenylene ligand, comprising ruthenium, iridium and rhodium. These complexes were synthesized, then studied by mass spectroscopy, HPLC, cyclic voltammetry and spectroscopy. Trimetallic homo-and heteronuclear complexes are unstable in chromatographic conditions or with some organic solvents. Bimetallic compounds have stability, enabling data presentation.

An investigation of low voltage cathodoluminescent characteristics of ZnGa2O4 phosphor in the 300 to 700 nanometer range reveals a peaking of the blue cathodoluminescent emission at 470 nanometers. The ZnGa2O4 phosphor is grown by radio frequency magnetron sputtering. Luminescent characteristics of the phosphor are affected by the annealing treatment and substrate heating. Phosphors with a perfect crystal structure and a perfect diffraction pattern possess better properties of luminescence.

The measured conversion efficiencies at 9.89, 23.6, 44.7, and 160 [Angstrom] of P45 phosphor screens, as well as those of paraterphenyl, tetraphenyl butadiene, and sodium salicylate at 9.89, 44.7, and 67.6 [Angstrom], are presented. The conversion efficiency is defined as the ratio of photoelectrons ejected from the photocathode of a visible detector, which are excited by the scintillated photons that are emitted from the phosphor in a solid angle of 2[Pi], to the number of soft-x-ray photons incident on the phosphor. The effect of the phosphor's thickness on the conversion efficiency was studied. The P45 phosphor converts the soft-x-ray photon (10-200 [Angstrom]) into an order of magnitude more visible photons than the low-Z phosphors. The P45 phosphor screen used in conjunction with a photomultiplier tube offers a soft-x-ray photodetector with a conversion efficiency that ranges from 0.5 to 160 [Angstrom] to 12 at 9.89 angstroms and a high electronic gain.

Degradation nature of LaOBr:Tb under cathode-ray excitation is caused by reduction in browning of phosphor layer and light generation efficiency. Optical analysis of LaoBr:Tb reveals microscopic development of defects and the dominant bromine ion desorption. Combined doping of phosphor and iodide or chloride reduces the degradation nature of LaoBr:Tb.

The phosphors of the alkali-earth sulfides CaS:Eu and SrS:Eu were studied using x-ray photoelectron spectroscopy. The results showed that CaS:Eu phosphors stabilized against water vapor and carbon dioxide by annealing at high temperature for an extended period of time. Between 900 and 1,100 degrees celsius, the S 2p core level underwent abrupt changes in the chemical state of sulfur changes.

Green electroluminescence in powder layers of gadolinium oxyulfide doped with terbium was investigated. The results showed that the cells featured a sharply rising B-V curve related to the insulator-phosphor interface chracteristics of electroluminescent thin film devices. This indicated that barrier formation brought about by the localized space charge region was possible.

The effect of pressure on the thermoluminescence and photoluminescence of ZnS:Mn:Cu:Cl was investigated. The results showed that two traps were present and these increased in depth as pressure became greater. The deepest trap was observed to be connected to defects due to Mn while the two traps next lower inenergy were observed to be connected to defects brought about by Cl. However, the remaining trap could not be associated with any particular defect.

An unusual luminescent inorganic oxide, [Sr.sub.2]Ce[O.sub.4], was identified by parallel screening techniques from within a combinatorial library of more than 25,000 members prepared by automated thin-film synthesis. A bulk sample […]

Quantitative data on the beam energy dependence of phosphor cathodoluminescence with high spatial resolution can be gleaned by combining sophisticated digital imaging manipulation techniques with scanning cathodoluminescence (SCL). Popular in categorizing local minority carrier lifetime nonuniformities in thin and bulk film semiconductors, SCL was, however, not as extensively used in phosphor powders. This was partly due to the effect of the collection and scattering of light on the extraction of quantitative information about light generation efficiency.

Highly emissive (with an external quantum yield exceeding 35 percent at a 365-nanometer excitation wavelength) broadband phosphors can be synthesized from a tetraalkoxysilane sol-gel precursor and a variety of organic [...]

Thermographic phosphors including rare-earth ions were used to demonstrate the effects of heat conduction in solids. Phosphors can be excited by broadband ultraviolet radiation to feature broadband absorption and redistributed according to the temperature-dependent Boltzmann distribution. Emissions that include transitions between the excited and lower states were observed in experiments using the thermographic phosphor europium doped lanthanum oxysulfide.

Luminescence from BaFBr:Eu2+ phosphors by photosimulation of longer wavelength than F absorption bands was seen after x-irradiation for 10 sec. This was due to the surface states or intrinsic defects of the powders. Results indicated that the luminescence by photostimulation into F bands can be reduced by electron migration from F centers into the surface states or intrinsic defects, hence reducing the x-ray storage or image stability. Surface passivation can reduce these defects and enhance the phosphors or image plate quality.

The pressure dependency of the photoluminescence of (Tb3+)- and (Eu3+)-doped oxide sulfides was investigated. The luminescence spectra and lifetimes of Gd2O2S:Tb and La2O2S:Eu indicated that pressure increases covalency and electronegativity of the sulfur anion and decreases interionic repulsion. In effect, a shift in energy level occurred from interconfigurational or charge-transfer transition.

[gamma]-AlON:[Er.sup.3+] Phosphors with different [Er.sup.3+] concentration for upconversion luminescence are prepared by a combination of carbothermal reduction and nitridation and solid-state synthesis methods. The pump power dependence has shown a two-photon process involved in the upconversion luminescence and the ratio of red emission relative to green emission is increased with the increase in [Er.sup.3+] concentration.

Sr2CeO4 blue phosphor particles were prepared with an emulsion liquid membrane system, which could be utilized as a micro reactor for the preparation of size- and morphology-controlled fine particles. The composite oxalate particles obtained were sub micrometer size and much smaller than those prepared in the homogeneous aqueous solutions.

The suitability of newly synthesized series of haloborate phosphors is investigated with the general formula M2B5O9X:Ce(super 3+) (M = Sr or Ca; X = Br or Cl) for thermal neutron detection and with reduced sensitivity to gamma background. The storage properties such as yield of photostimulated luminescence (PSL) and thermoluminescence are reported.

The concept of phosphors having high cathodoluminescence (CL) efficiency at low voltages and high current densities, and the surface modification of phosphors are studied to improve field emission display (FED) phosphor efficiency and maintenance. It is reported that CL efficiency decreases with surface charging, which may occur due to the high resistance of phosphor materials.

Two spectroscopic techniques that are very sensitive to low concentration of activators in phosphor lattices are discussed. Mossbauer and laser Raman spectroscopy have benefited from considerable technological advances and these techniques are becoming increasingly user-friendly.

The synthesis, structure and photoluminescence properties are described for the three-coordinate mononuclear and dinuclear complexes. Ag1, Cu1, and Cu2 exhibit blue pyrazole-based structures emissions with short phosphorescence lifetimes, 101-102 micro sec , due to an internal heavy-metal effect.

The red thin-film phophors were fabricated based on a ZnO:(La,Eu)OF nanocomposite structure by dispersing (La,Eu)OF nanoparticles in a ZnO film matrix. Studies found that Ga doping increases the cathodoluminescence (CL) intensity of the film.