Quantitative luminescent analysis methods

Abstract

We have developed quantitative luminescent analysis methods not requiring the use of reference media with known contents of the analyte components. The methods are based on relations describing re-absorption of luminescence and also on a relation connecting the luminescence intensity and the absorption coefficients of a multicomponent medium. We present equations allowing us to find the absorption coefficients and consequently the concentrations of the components of the medium from the luminescence intensity measured in relative units. In order to determine the concentrations of nonluminescent components, we also propose and demonstrate the use of a luminescent probe. We present the experimental results for determination of the absorption coefficients and the concentrations of substances by the methods we developed.Introduction. In luminescent analysis, the presence and concentration of substances are determined from the luminescence spectrum and intensity. For absorption optical densities that are small compared with unity, the photoluminescence (PL) intensity can be assumed to be proportional to the absorption coefficient k 0 , which is uniquely connected with the concentration of the corresponding component of the medium. Therefore from the changes in the intensity in such a case, we can judge changes in the concentration of the substance, which allows us to follow the temporal kinetics of various processes such as chemical reactions. If the condition that the optical density be small is not met, then the photoluminescence intensity cannot be assumed to be proportional to the concentration. Intensity measurements are usually made in relative units and within a small solid angle, the size of which often is difficult to determine sufficiently accurately. Therefore even in the most favorable cases, when carrying out quantitative luminescent analysis we need to use reference media with known content of the components.Luminescent study methods are widely used in scientific practice [1][2][3][4]. They have high sensitivity. There is a large selection of instruments for such studies. However, quantitative luminescent analysis is practically not used due to difficulties in its implementation. This paper is devoted to development of new quantitative luminescent analysis methods. The fundamental difference between our methods and existing methods is the fact that they do not require reference samples, even though they are based on measurements of the photoluminescence intensity in relative units. We have also developed a luminescent probe method which expands the possibilities for analysis, allowing us to use it for nonluminescent substances. The proposed methods are based on analytical relations connecting the photoluminescence intensity and the absorption coefficient of the medium. Such relations have been obtained recently for photoluminescence and photoluminescence excitation (PLE) spectra. In the first case, equations are used that determine the changes in the photoluminescence intensities as a result of re-absorpt...

Point defects isomerism in lithium fluoride crystals and nanocrystals

“…Various techniques (annealing at definite temperatures and time, light exposure at certain wavelengths) were used to reduce these distortions . Measurements were also corrected by the methods described in to get true PL and PLE spectra. The corrected PLE spectra correspond to absorption spectra up to a constant factor.…”

Aggregate color center formation processes in lithium fluoride crystals after irradiation

“…Absorption of F 2 color centers was isolated from the M band, assuming the presence in this region of the spectrum of two close absorption bands for F 3 + centers with maxima at 420 nm and 460 nm. The hypothesis used does not correspond to reality, since as shown in [17], F 3 + color centers in this region have a single absorption band with maximum at 448 nm. Accordingly, the numerical estimates and the conclusions concerning the kinetics of the growth in the concentrations of F 2 centers in [14] should be reconsidered.…”

Luminescent method for determining low concentrations of a substance in optically dense media

“…Furthermore, the media may be not only absorbing media but also multicomponent and scattering media. In [5], methods are discussed for quantitative analysis of absorbing media based on measurements of the photoluminescence intensity in relative units, and not requiring references with known content of the components. They are extended to nonluminescent substances when a luminescent probe is introduced into the analyte medium [6].…”

“…They are extended to nonluminescent substances when a luminescent probe is introduced into the analyte medium [6]. The sensitivity of the methods [5,6] is close to the sensitivity of absorption measurements. Therefore it remains important to search for methods for analysis of absorbing media in which high sensitivity of luminescence measurements could be realized.…”