Rapid quantitative detection of Yersinia pestis by lateral-flow immunoassay and up-converting phosphor technology-based biosensor

Up-converting phosphor technology (UPT)-based lateral-flow immunoassay has been developed for quantitative detection of Yersinia pestis rapidly and specifically. In this assay, 400 nm up-converting phosphor particles were used as the reporter. A sandwich immumoassay was employed by using a polyclonal antibody against F1 antigen of Y. pestis immobilized on the nitrocellulose membrane and the same antibody conjugated to the UPT particles. The signal detection of the strips was performed by the UPT-based biosensor that could provide a 980 nm IR laser to excite the phosphor particles, then collect the visible luminescence emitted by the UPT particles and finally convert it to the voltage as a signal. V-T and V-c stand for the multiplied voltage units for the test and the control line, respectively, and the ratio V-T/V-C is directly proportional to the number of Y pestis in a sample. We observed a good linearity between the ratio and log CFU/ml of Y pestis above the detection limit, which was approximately 10(4) CFU/mI. The precision of the intra- and inter-assay was below 15% (coefficient of variation, CV). Cross-reactivity with related Gram-negative enteric bacteria was not found. The UPT-LF immunoassay system presented here takes less than 30 min to perform from the sample treatment to the data analysis. The current paper includes only preliminary data concerning the biomedical aspects of the assay, but is more concentrated on the technical details of establishing a rapid manual assay using a state-of-the-art label chemistry. (c) 2006 Elsevier B.V. All rights reserved.

Upconversion luminescence from E-2 state of Cr3+ in Al2O3 crystal by infrared femtosecond laser irradiation

Visible upconversion luminescence was observed in Cr3+: Al2O3 crystal under focused femtosecond laser irradiation. The luminescence spectra show that the upconversion luminescence originates from the E-2-(4)A(2) transition of Cr3+. The dependence of the fluorescence intensity of Cr3+ on the pump power reveals that a two-photon absorption process dominates in the conversion of infrared radiation to the visible emission. It is suggested that the simultaneous absorption of two infrared photons produces the population of upper excited states, which leads to the characteristic visible emission from E-2 state of Cr3+.

Three-photon-excited upconversion luminescence of Ce3+: YAP crystal by femtosecond laser irradiation

Infrared to ultraviolet and visible upconversion luminescence was demonstrated in trivalent cerium doped YAlO3 crystal (Ce3+: YAP) under focused infrared femtosecond laser irradiation. The fluorescence spectra show that the upconverted luminescence comes from the 5d-4f transitions of trivalent cerium ions. The dependence of luminescence intensity of trivalent cerium on infrared pumping power reveals that the conversion of infrared radiation is dominated by three-photon excitation process. It is suggested that the simultaneous absorption of three infrared photons pumps the Ce3+ ion into upper 5d level, which quickly nonradiatively relax to lowest 5d level. Thereafter, the ions radiatively return to the ground states, leading to the characteristic emission of Ce3+. (c) 2005 Optical Society of America.

Study of infrared luminescence from Er-implanted GaN films

In this study, we report the dependences of infrared luminescence properties of Er-implanted GaN thin films (GaN:Er) on the kinds of substrates used to grow GaN, the growth techniques of GaN, the implantation parameters and annealing procedures. The experimental results showed that the photoluminescence (PL) intensity at 1.54 mum was severely influenced by different kinds of substrates. The integrated PL peak intensity from GaN:Er /Al2O3 (00001) was three and five times stronger than that from GaN:Er /Si (111) grown by molecular beam epitaxy (MBE) and by metalorganic chemical vapor deposition (MOCVD), respectively. The PL spectra observed from GaN:Er/Al2O3 (0001) grown by MOCVD and by MBE displayed a similar feature, but those samples grown by MOCVD exhibited a stronger 1.54 mum PL. It was also found that there was a strong correlation between the PL intensity with ion implantation parameters and annealing procedures. Ion implantation induced damage in host material could be only partly recovered by an appropriate annealing temperature procedure. The thermal quenching of PL from 15 to 300 K was also estimated. In comparison with the integrated PL intensity at 15 K, it is reduced by only about 30 % when going up to 300 K for GaN:Er/Al2O3 sample grown by MOCVD. Our results also show that the strongest PL intensity comes from GaN:Er grown on Al2O3 substrate by MOCVD. (C) 2004 Elsevier B.V. All rights reserved.

The effect of inserting strain-compensated GaNAs layers on the luminescence properties of GaInNAs/GaAs quantum well

Photoluminescence (PL) properties of GaInNAs/GaAs quantum wells (QWs) with strain-compensated GaNAs layers grown by molecular beam epitaxy are investigated. The temperature-dependent PL spectra of GaInNAs/GaAs QW with and without GaNAs layers are compared and carefully studied. It is shown that the introduction of GaNAs layers between well and barrier can effectively extend the emission wavelength, mainly due to the reduction of the barrier potential. The PL peak position up to 1.41 mum is observed at the room temperature. After adding the GaNAs layers into QW structures, there is no essential deterioration of luminescence efficiency. N-induced localization states are also not remarkably influenced. It implies that with optimized growth condition, high-quality GaInNAs/GaAs QWs with strain-compensated GaNAs layers can be achieved. (C) 2003 Elsevier Science B.V. All rights reserved.

Influence of combined InAlAs and InGaAs strain-reducing laser on luminescence properties of InAs/GaAs quantum dots

We have fabricated self-organized InAs/GaAs quantum dots (QDs) capped by 1 nm In0.2Al0.8As and 5 nm In0.2Ga0.8As strain-reducing layer (SRL). The luminescence emission at a long wavelength of 1.33 mum with narrower half width is realized. A wider energy separation between the ground and first excited radiative transitions of up to 102meV was observed at room temperature. Furthermore, the comparative study proves that luminescence properties of InAs/GaAs QDs overgrown with combined InAlAs and InGaAs SRLs are much better than that of one capped with InGaAs or InAlAs SRL. (C) 2002 Elsevier Science B.V. All rights reserved.

Effect of growth temperature on luminescence and structure of self-assembled InAlAs/AlGaAs quantum dots

The effect of growth temperature on the optical properties of self-assembled In0.65Al0.35As/Al0.35Ga0.65As quantum dots is studied using photoluminescence and electroluminescence spectra. With the growth temperature increasing from 530 to 560 degreesC, the improvement of optical and structural quality has been observed. Furthermore, edge-emitting laser diodes with three stacked InAlAs quantum dot layers grown at different temperature are processed, respectively. For samples with quantum dots grown at 560 degreesC, the continuous wave operation is obtained up to 220 K, which is much higher than that of ones with InAlAs islands grown at 530 degreesC and that of the short-wavelength quantum-dot laser previously reported. (C) 2001 American Institute of Physics.

Interband luminescence and absorption of GaNAs/GaAs single-quantum-well structures

We have investigated the interband electron transitions in a GaNAs/GaAs single quantum well (QW) by photoluminescence and absorption spectra. The experimental results show that the dominant photoluminescence at low temperature and high excitation intensity originates from transitions within the GaNAs layer. The interband transition energy for QWs with different well widths can be well fitted if a type-II band line up of GaNAs/GaAs QWs is assumed. (C) 2000 American Institute of Physics. [S0003-6951(00)03220-4].

Photostimulated luminescence of silver clusters in zeolite-Y

Upon UV-irradiation at 254 nm, the photoluminescence of silver atoms in zeolite-Y decreases, meanwhile an absorption band shows up around 840 nm. By photostimulation at 840 nm, fluorescence of silver atoms is detected, which is called photostimulated luminescence, and the photoluminescence of silver atoms is increased slightly. These phenomena are attributed to the charge-transfer interaction between the zeolite framework and the entrapped silver atoms. (C) 1997 Published by Elsevier Science B.V.

Study of infrared luminescence from Er-implanted GaN films

In this study, we report the dependences of infrared luminescence properties of Er-implanted GaN thin films (GaN:Er) on the kinds of substrates used to grow GaN, the growth techniques of GaN, the implantation parameters and annealing procedures. The experimental results showed that the photoluminescence (PL) intensity at 1.54 mum was severely influenced by different kinds of substrates. The integrated PL peak intensity from GaN:Er /Al2O3 (00001) was three and five times stronger than that from GaN:Er /Si (111) grown by molecular beam epitaxy (MBE) and by metalorganic chemical vapor deposition (MOCVD), respectively. The PL spectra observed from GaN:Er/Al2O3 (0001) grown by MOCVD and by MBE displayed a similar feature, but those samples grown by MOCVD exhibited a stronger 1.54 mum PL. It was also found that there was a strong correlation between the PL intensity with ion implantation parameters and annealing procedures. Ion implantation induced damage in host material could be only partly recovered by an appropriate annealing temperature procedure. The thermal quenching of PL from 15 to 300 K was also estimated. In comparison with the integrated PL intensity at 15 K, it is reduced by only about 30 % when going up to 300 K for GaN:Er/Al2O3 sample grown by MOCVD. Our results also show that the strongest PL intensity comes from GaN:Er grown on Al2O3 substrate by MOCVD. (C) 2004 Elsevier B.V. All rights reserved.

Self-assembled 3D microflowery In(OH)(3) architecture and its conversion to In2O3

Using sodium dodecyl sulfate (SDS), a 3D microflowery indium hydroxide [In(OH)(3)] structure assembled from 2D nanoflakes was fabricated in a large quantity via a hydrothermal approach at relative low temperature. The obtained In(OH)(3) flowers exhibited a narrow size range between 4 and 6 mu m. The properties of these composites were characterized by XRD, EDX, FE-SEM, TEM, SAED, and TGA. In this work, both the use of urea and SDS and the amounts of these components played important roles in the formation of In(OH)3 with different nanostructures.

Facile synthesis and luminescence properties of octahedral YVO4:Eu3+ microcrystals

Uniform octahedral YVO4:Eu3+ microcrystals have been successfully prepared through a designed two-step hydrothermal conversion method. One-dimensional precursor Y4O(OH)(9)NO3 was first prepared through a simple hydrothermal process without using any surfactant, catalyst or template. Subsequently, well-defined octahedral YVO4 was synthesized at the expense of the precursor during a hydrothermal conversion process. XRD results demonstrate that the diffraction peaks of the final product can be well indexed to the pure tetragonal phase of YVO4.

Electrospinning Synthesis and Luminescence Properties of One-Dimensional Zn2SiO4:Mn2+ Microtibers and Microbelts

One-dimensional Mn2+-doped Zn2SiO4 rnicrobelts and microfibers were prepared by a simple and cost-effective electrospinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), energy-dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and cathodoluminescence (CL) spectra as well as kinetic decays were used to characterize the samples. The XRD and DTA results show that the Zn2SiO4 phase begins to crystallize at 800 degrees C and crystallizes completely around 1000 degrees C. SEM results indicate that the as-prepared microbelts/fibers are smooth, whose diameters decrease with increasing the annealing temperature. The average diameter of the Zn2SiO4:Mn2+ microfibers annealed at 1000 degrees C is 0.32 mu m, and their lengths reach up to several millimeters. The average width and thickness of the Zn2SiO4:Mn2+ microbelts fired at 1000 degrees C are around 0.48 and 0.24 mu m, respectively.

Facile synthesis of highly uniform octahedral LuVO4 microcrystals by a facile chemical conversion method

Uniform octahedral LuVO4 microcrystals have been successfully prepared through a designed two-step hydrothermal method. One-dimensional lutetium precursor was first prepared through a simple hydrothermal route. Subsequently, a well-shaped octahedral LuVO4 sample was synthesized at the expense of the wirelike precursors during the hydrothermal process. The whole process in this method was carried out in aqueous conditions without the use of any organic solvents, surfactant, or catalyst. The conversion process from nanowire precursor to octahedral product has been investigated in detail. The LuVO4 : Ln(3+) (Ln Eu, Dy, Sm, and Er) phosphors show strong light emissions with different colors coming from different activator ions under ultraviolet light excitation or low-voltage electron beam excitation. Furthermore, this general and facile method may be of much significance in the synthesis of many other lanthanide compounds with polyhedral morphology.

Uniform Lanthanide Orthoborates LnBO(3) (Ln = Gd, Nd, Sm, Eu, Tb, and Dy) Microplates: General Synthesis and Luminescence Properties

A variety of uniform lanthanide orthoborates LnBO(3) (Ln = Gd, Nd, Sm, Eu, Tb, and Dy) microplates have been successfully prepared by a general and facile conversion method. One-dimensional (ID) lanthanide hydroxides were first prepared through a simple hydrothermal process. Subsequently, uniform LnBO(3) microplates were synthesized at the expense of the ID precursors during a hydrothermal conversion process. The whole process in this method was carried out in aqueous condition without the use of any organic solvents, surfactant, or catalyst. The as-obtained rare earth ions doped GdBO3 and TbBO3 microplates show strong light emissions with different colors coming from different activator ions under ultraviolet excitation or low-voltage electron beam excitation, which might find potential applications in fields such as light phosphor powders and advanced flat panel display devices.