Fluorescence future developments

In the past ten years, numerous applications of fluorescence methods for monitoring homogeneous and heterogeneous immunoassays have been reported. Advances in the design of fluorescent labels have prompted the development of various fluorescent immunoassay schemes such as the substrate-labeled fluorescent immunoassay and the fluorescence excitation transfer immunoassay. As sophisticated fluorescence instrumentation for lifetime measurement became available, the phase-resolved and time-resolved fluorescent immunoassays have also developed. With the current emphasis on satellite and physician s office testing, future innovations in fluorescence immunoassay development will be expected to center on the simplification of assay protocol and the development of solid-state miniaturized fluorescence readers for on-site testing. 

Atomic Fluorescence Spectrometry. A spectroscopic technique related to some of the types mentioned above is atomic fluorescence spectrometry (AFS). Like atomic absorption spectrometry (AAS), AFS requires a light source separate from that of the heated flame cell. This can be provided, as in AAS, by individual (or multielement lamps), or by a continuum source such as xenon arc or by suitable lasers or combination of lasers and dyes. The laser is still pretty much in its infancy but it is likely that future development will cause the laser, and consequently the many spectroscopic instruments to which it can be adapted to, to become increasingly popular. Complete freedom of wavelength selection still remains a problem. Unlike AAS the light source in AFS is not in direct line with the optical path, and therefore, the radiation emitted is a result of excitation by the lamp or laser source. 

In the following we consider the nature of LIFS in more detail. The theoretical foundations of laser excitation and fluorescence are outlined and such issues as detectability and dynamic range are discussed. Finally the status of LIFS is summarized and a prognosis for future development given. 

High-resolution circuitry and active devices employing Langmuir-Blodgett film techniques or polymer-based transistors are being considered for the sophisticated electronics required in future vehicles. Temperature or energy balance in the vehicle could be controlled through conductive polymers or semiconductor deposits on electrochromic windows. Electroluminescent liquid crystals and fluorescent and electrochromic materials used for visual displays show promise for future development. 

In this chapter we have mentioned only a few of the more important future developments which can be foreseen in colloid science. Many of these will depend on the availability of modern instrumentation and of powerful computer facilities. In addition to the techniques dealt with in this chapter, mention should also be made of the contributions from greatly improved electron microscopic techniques, ultracentrifuges, and X-ray equipment. Other techniques that will become of increasing significance include dielectric measurements, electrical birefringence, and time-resolved fluorescence. 

It is the aim of this chapter to review the most widely used techniques for time-resolved fluorescence in the life sciences, to point out possible future developments, and to give examples of typical and important applications. The reader less familiar with fluorescence techniques is referred to the chapters on fluorescence energy transfer by P. R. Selvin (this volume... 

Abstract In this chapter, the structures and luminescent properties of some widely used practical oxide phosphors for three-band fluorescent lamps, plasma displays, and white light-emitting diodes are briefly introduced. The problems of preparation, luminescent properties, and applications of these phosphors in industry are presented. Many efforts have been made to improve the performance of these phosphors mainly by composition adjustment, surface modification, and improvements in preparation methods. However, some of these problems in engineering still remain therefore, developing new phosphors with superior stabilities and efficiency to replace traditional phosphors with poor performance is an urgent demand, and some newly developed promising phosphors are briefly introduced. Finally, future developments of oxide phosphors are briefly discussed. 

The present article concentrates on atomic physics experiments involving hard synchrotron radiation. Selected experiments are reviewed in order to elucidate basic principles as well as experimental possibilities and achievements. No attempt is made to cover the whole rapidly expanding field or to speculate on future developments. The discussion starts with instrumental details, e.g., the properties of synchrotron radiation, and a brief review of x-ray monochromators and detectors. Thereafter x-ray absorption studies are described that are experimentally very simple (at least in principle). More detailed information on atomic structure may be obtained if one observes not only the x-ray absorption, but additionally the induced fluorescence or emitted electrons. Finally, studies of photon scattering are sketched. 

J.R. Lakowicz, G. Laczo, I. Gryczynski, H. Szmacinski, W. Wiczk, M.L. Johnson Pireqnency-doniain fluorescence spectroscopy Principles, biochemical appUcations and future developments. Ber. Bunseiiges. Phys. Chem. 93, 316 (1989)... 

To date, the diffusion coefficient of a solute in a gel has been determined by the membrane technique, magnetic gradient nuclear magnetic resonance (NMR) spectroscopy, and fluorescence polarization relaxation. Compared to these techniques, the characteristics of the method described in this section include (1) the information obtained by this method is the value near the electrode and the electrode itself acts as a microprobe (2) the diffusion coefficient and disfribution coefficient of the solute can be simultaneously determined (3) not only the gel at equilibrium state but also a non-equilibrium state gel can be studied and (4) relatively simple apparatus can be used to make measurements. Future developments that will build on these advantages is desired. 

Whereas the eadiest fluorescent-dye pigments would last only 20 days outdoors in a screen-ink film, fade resistance has been improved to such an extent that some modem daylight-fluorescent coated panels stiU have useful color after nine months or mote in Florida sunlight in a 45° exposure tack facing south. The fluorescent layer is usually coated with an acrylic film containing a uv absorber. Indoor-accelerated exposure equipment is, of course, invaluable in the development of such systems. Better dyes and resins very likely will make possible fat mote stable coatings in the future. 

The active state of luminescence spectrometry today may be judged ly an examination of the 1988 issue of Fundamental Reviews of Analytical Chemistry (78), which divides its report titled Molecular Fluorescence, Phosphorescence, and Chemiluminescence Spectrometry into about 27 specialized topical areas, depending on how you choose to count all the subdivisions. This profusion of luminescence topics in Fundamental Reviews is just the tip of the iceberg, because it omits all publications not primarily concerned with analytical applications. Fundamental Reviews does, however, represent a good cross-section of the available techniques because nearly every method for using luminescence in scientific studies eventually finds a use in some form of chemical analysis. Since it would be impossible to mention here all of the current important applications and developments in the entire universe of luminescence, this report continues with a look at progress in a few current areas that seem significant to the author for their potential impact on future work. 

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