Time-resolved luminescence methods

Pulse radiolysis, using as time-resolved detection methods optical absorption, luminescence, electrical conductivity or electron spin resonance can be expected to give information on the formation of transient or permanent radiation products and on their movement. 

The same equipment, which is used for time-resolved Ivuninescence application is suitable for other laser-based spectroscopies. Thus several spectroscopic methods may be applied simultaneously. The most important techniques, which may be used together with time-resolved luminescence, are laser-induced breakdown spectroscopy, Raman spectroscopy and Second Harmonics Generation spectroscopy. 

It is clear that in all cases mentioned above, time-resolved fluorescence methods have enabled a far greater insist into the character and complexities of biopolymer luminescence than have previously been obtained by steady state illuminatnn techniques. 

Time-resolved luminescence spectroscopy complements the steady-state method and can provide essential kinetic information about the decay of excited states. Application of time-resolved fluorescence spectroscopy for analytical chemistry, where low concentrations might require the use of long... 

The most important applications of luminescence probing in microemulsions involve the deactivation dynamics or excitation energy transfer properties of the excited states. With a brief flash of light a population of excited species is created in the sample, and the subsequent deactivation is observed over time. The decay of the excited probe, and the fluorescence spectrum, may depend on the interactions with the environment, which reveal useful information. In time-resolved luminescence quenching (TRLQ), however, it is the interaction of the probe with another added component, a quencher, that is studied. This method is dealt with here. For micellar systems, several publications have already discussed it in both experimental and theoretical detail [1-6]. 

Fig. 8 Experimental setup for a time-correlated single-photon counting method or picosecond single-photon timing method, used for time-resolved luminescence measurements in a range of picoseconds.

Inorganic phosphors are potential labels for time-resolved luminescence staining and assays in aqueous environment [23, 52-55]. The lanthanide phosphors have essentially infinite shelf life, no toxicity, no photobleaching, and are unaffected by environmental conditions such as pH, temperature, enzymatic reactions, or solvent effects. Their major drawback is that the luminescence per lanthanide ion is significantly less than from the dye-doped or dye nanoparticles due to the weak absorption of individual ions partly compensated by their higher number. Inorganic nanoparticles, however, can be prepared readily in large quantities with relatively simple methods. The size of the nanoparticles can be controlled from low nanometer scale to several hundred nanometers with a narrow size distribution. 

In luminescence research, attention has recently shifted from the development of solid-state phosphors (in television screens) and lasers (e.g., yttrium aluminum garnet (YAG) lasers) to solution-state methods exemplified by the development of probes for bioinorganic chemistry and the development of time-resolved luminescent labelings and assays. 

The same equipment, which is used for time-resolved luminescence application is suitable for other laser-based spectroscopies. Thus several spectroscopic methods may be applied simultaneously. The mostly important technique, which may be used together with time-resolved luminescence, is laser-induced breakdown spectroscopy. Several books have been recently published devoted to Laser Induced Breakdown Spectroscopy (LIBS) (Cremers and Radziemski 2013 Miziolek et al. 2006 Singh and Thakur 2007 Noll 2012 Hahn and Omenetto 2010 Hahn and Omenetto 2012). LIBS aspects were considered applied to the analysis of minerals, rocks and related materials (Senesi 2014). Thus only the theoretical aspects which are the mostly relevant to our research devoted to the real time online quality control of minerals will be considered. 

As studies of surfactant self-assemblies developed during 1970 to 1980, other methods, such as time-resolved luminescence quenching (and the related methods of flash photolysis and pulse radiolysis), nuclear magnetic resonance (NMR),... 

Pihlasalo, S. Puumala, R Hanninen, R Harma, H. Sensitive method for determination of protein and cell concentrations based on competitive adsorption to nanoparticles and time-resolved luminescence resonance energy transfer between labeled proteins. Anal. Chem. 2012,84,4950 956. 

Lanthanide chelates also can be used in FRET applications with other fluorescent probes and labels (Figure 9.51). In this application, the time-resolved (TR) nature of lanthanide luminescent measurements can be combined with the ability to tune the emission characteristics through energy transfer to an organic fluor (Comley, 2006). TR-FRET, as it is called, is a powerful method to develop rapid assays with low background fluorescence and high sensitivity, which can equal the detection capability of enzyme assays (Selvin, 2000). 

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