Luminescence basic principles

In recent years no truly new basic principles have been introduced for the detection of luminescence. However, the technical evolution in the field of microelectronics and optoelectronics, charge coupled device (CCD) detectors, fiberoptics, assembly techniques, and robotics resulted in the introduction on the market of new generations of instruments with increased performance, speed, and ease of handling. In this chapter, some of their typical features will be reviewed. To keep this presentation at a concrete level and to illustrate some specific item, instruments of different makes will be referred to. However, this does not imply they are better than those not cited. It is more a matter of availability of recent documentation at the time of writing. Note that numerical values cited typically relate what can be done today and may vary from one instrument to another from the same company. 

When looking for R(III) determination, use can be made of the antenna effect already discussed in sect. 3.7, provided the lanthanide of interest is luminescent. The basic principle is to add a given organic ligand, which will ensure a high complexation constant with the lanthanide together with an efficient UV absorption and energy transfer to the R(III)... 

Device motivation for interface studies, and Optical absorption and emission in conjugated oligomers and polymers. The principles of device physics of metal insulator field-effect transistors (MISFETs) and light emitting diodes (LEDs) are oudined mainly as motivation for the contents of the chapters which follow, but also to point out certain features relevant to developing an understanding of the nature of the polymer-metal interface (chapters 5 and 6). The basic principles of electro-luminescence are reviewed here, at the level consistent with the aims of this work. 

The idea of the use of luminescent lanthanide chelates in bioanalysis can be traced back to the 1980s, when Hemmila (1985) reported a time-resolved fluorometric system using an Eu labeling reagent, which was commercially produced by Wallac Oy company. The system was intended for immunoassay and included the spectrometer for time-resolved measurements. The basic principle of the immunoassay system (DELFIA ) is shown in fig. 1. 

The basic principle of the DAC is extremely simple [6,7] an anvil is made of a brilliant cut diamond with the tip cut to form a small flat part, the culet. In a DAC, two such anvils are placed in front of each other, with the culets parallel. The experimental volume is a cylindrical hole drilled in a metallic foil, the gasket. In that volume are the sample, a pressure gauge, normally a ruby chip, whose luminescence is calibrated versus pressure, and a pressure transmitting medium whose function is to ensure the stresses on the sample are as homogeneous as possible (FIGURE 2). All DACs work with the same principle. They differ only in the way the force is applied on the diamonds. 

The basic principles of dc and ac voltage measurements are discussed in Chapter XVI and in standard textbooks on electronics. In many apphcations these measnrements are carried out by complex electronic instruments designed to produce a visual record of the detected signal, either as a trace on a luminescent screen, a plot on paper, or a numerical... 

Immunoassays which employ drugs labelled with a substance which emits light when activated have been developed. The basic principles of these assays are similar to those of fluoroimmunoassays. The use of luminescent labels, however, has the advantage that light is not introduced into the system, so giving an increase in sensitivity. 

In this review, the basic principles and practical aspects of photol uminescence techniques and their application to adsorption, catalysis, and photocatalysis phenomena have been summarized. We did not discuss studies on adsorption luminescence and/or chemiluminescence in which photons emitted by adsorption or chemical reactions are used to monitor adsorption and/or catalytic reactions on surfaces (255, 256). 

The present review begins with a brief description of the basic principles of luminescence [1-3], after which it deals with the fluorescence studies of polymers in solution and energy transfer in polymeric systems. Spectral and time dependent studies of polymers in the gel state are discussed later, with an emphasis on phase transition and phase separation studies. 

The basic principle of a streak camera is schematically depicted in Fig. 11.39. The optical pulse with the time profile I(t) is focused onto a photocathode, where it produces a pulse of photoelectrons Ape(0 oc I(t). The photoelectrons are extracted into the z-direction by a plane grid at the high voltage U. They are further accelerated and imaged onto a luminescent screen at z = z. A pair... 

Most of the basic principles needed to approach the luminescence of the lanthanide ions have been described. Luminescence is a fascinating phenomenon, but as it was shown, very intricate because many processes are involved. Therefore, the design of highly luminescent lanthanide compoimds and especially of highly luminescent-sensitized lanthanide complexes is quite unpredictable. From a theoretical point of view, the efficiency of the luminescence can always be associated with one particular feature of the environment of the lanthanide ion. It may be solvent molecules... 

The next two sections provide a discussion of the basic principles of luminescence spectroscopy, which include the electronic transitions and the important parameters determined from luminescence measurements. Then follow two sections that describe the general characteristics of luminescence measurements and one which provides two case studies for organic and inorganic luminophores. The remainder of the article covers more specific topics and phenomena in luminescence spectroscopy, namely quenching, energy transfer, exciplexes and chemiluminescence. The examples in this article were selected to cover multidisciplinary areas of science. 

Abstract In the first part of this chapter we will illustrate circular dichroism and we will discuss the optical activity of chemical compounds with respect to light absorption which is at the basis of this technique. Moreover, we will introduce the phenomena that lie behind the technique of optical rotatory dispersion. We thought appropriate to include a brief description of linear dichroism spectroscopy, although this technique has nothing to do with optical activity. In the final part of the chapter we will introduce the basic principles of the luminescence teehniques based on polarized (either circularly or linearly) excitation. The experimental approach to the determination of steady-state and time resolved fluorescence anisotropy will be illustrated. For all the teehniques examined in this chapter the required instrumentation will be schematieally deseribed. A few examples of application of these techniques to molecular and supramolecular systems will also be presented. 

Optical property refers to a material s response to exposure to electromagnetic radiation and, in particular, to visible light. This chapter first discusses some of the basic principles and concepts relating to the nature of electromagnetic radiation and its possible interactions with solid materials. Then it explores the optical behaviors of metallic and nonmetal-lic materials in terms of their absorption, reflection, and transmission characteristics. The final sections outline luminescence, photoconductivity, and light amplification by stimulated emission of radiation (laser), the practical use of these phenomena, and the use of optical fibers in communications. 

The first two chapters of this work cover theoretical and practical aspects of the emission process, the spectroscopic techniques and the equipment used to characterize the emission. Chapter 3 introduces and reviews the property of circularly polarized emission, while Chapter 4 reviews the use of lanthanide ion complexes in bioimaging and fluorescence microscopy. Chapter 5 covers the phenomenon of two-photon absorption, its theory as well as applications in imaging, while Chapter 6 reviews the use of lanthanide ions as chemo-sensors. Chapter 7 introduces the basic principles of nanoparticle upconversion luminescence and its use for bioimaging and Chapter 8 reviews direct excitation of the lanthanide ions and the use of the excitation spectra to probe the metal ion s coordination environment in eoordination compounds and biopolymers. Finally, Chapter 9 describes the formation of heterobimetallic complexes, in whieh the lanthanide ion emission is promoted through the hetero-metal. 

The book starts with a short introduction to the fundamentals of optical spectroscopy, (Chapter 1) describing the basic standard equipment needed to measure optical spectra and the main optical magnitudes (the absorption coefficient, transmittance, reflectance, and luminescence efficiency) that can be measured with this equipment. The next two chapters (Chapters 2 and 3) are devoted to the main characteristics and the basic working principles of the general instrumentation used in optical spectroscopy. These include the light sources (lamp and lasers) used to excite the crystals, as well as the instrumentation used to detect and analyze the reflected, transmitted, scattered, or emitted light. 

The interaction phenomenon of the analyte with radiation is governed or modifies the principle on which light is transmitted through the waveguide. Depending on that interaction, we can differentiate three basic types of intrinsic optical sensors [82] refractive-index-type sensors, luminescence-based sensors and absorption-type sensors. 

J. R. Lakowicz, Principles of Flnorescence Spectroscopy , Springer, New York, 2006, Considered by many the seminal reference material on luminescence instrumentation and basic measurements, although solid-state measurements are not directly addressed. 

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