RESUMEN
The need for the traceable characterization of fluorescence instruments is emphasized from a chemist's point of view, focusing on spectral fluorescence standards for the determination of the wavelength- and polarization-dependent relative spectral responsivity and relative spectral irradiance of fluorescence measuring systems, respectively. In a first step, major sources of error of fluorescence measurements and instrument calibration are revealed to underline the importance of this issue and to illustrate advantages and disadvantages of physical and chemical transfer standards for generation of spectral correction curves. Secondly, examples for sets of traceable chemical emission and excitation standards are shown that cover a broad spectral region and simple procedures for the determination of corrected emission spectra with acceptable uncertainties are presented. With proper consideration of the respective measurement principle and geometry, these dye-based characterization procedures can be not only applied to spectrofluorometers but also to other types of fluorescence measuring systems and even to Raman spectrometers.
RESUMEN
Real-time and real-space analysis of heavy and transition metal ions employing fluorescent sensor molecules has received much attention over the past few years. Since many of these cations possess intrinsic properties that usually quench the fluorescence of organic dye molecules, a lot of research has lately been devoted to designing fluorescent probes that show complexation-induced fluorescence enhancement. Such an analytical reaction would be highly desirable in terms of increased sensitivity and selectivity. However, in this particular field of sensor research, the photophysical and photochemical mechanisms involved as well as the chemical constitutions of the sensor molecules employed are rather diverse and up to now, very few attempts have been made to establish some general concepts for rational probe design. By analyzing various systems published by other researchers as well as own work, this contribution aims at an elucidation of some of the underlying principles of heavy and transition metal ion-enhanced emission.
Asunto(s)
Colorantes Fluorescentes/química , Espectrometría de Fluorescencia/instrumentación , Espectrometría de Fluorescencia/métodos , Absorción , Cationes , Espectroscopía de Resonancia por Spin del Electrón/métodos , Ligandos , Modelos Químicos , Fotoquímica , Factores de TiempoRESUMEN
The fluorescence behavior of a new bipyridyl ligand, 2,2'-bipyridyl-3,3'-diol (BPDO), was studied as a function of the metal ion complexed. At pH 7.6, the fluorescence of BPDO is strongly decreased by complexation to Cu(II), but binding to Zn(II) leads to an increase in fluorescence intensity. Time-resolved fluorescence measurements suggest that in the case of Cu(II), a nonfluorescent complex is formed, whereas in the presence of Zn(II), a new, longer decay component appears.