Dual emission and its λ-ratiometric detection in analytical fluorimetry. Pt. I. Basic mechanisms of generating the reporter signal

Abstract

The wavelength-ratiometric techniques gain increasing popularity in fluorescence probing and sensing for providing inner reference to output signal and removing instrumental artefacts, in this way increasing the sensitivity and reliability of assays. Recent developments demonstrate that such approach can allow achieving much more, with the application of broad range of novel molecular and nanoscale fluorophores (luminophores), exploring the whole power of photophysical and photochemical effects and using extended range of assay formats. Simplicity of detection and potentially rich content of output data allows realizing these techniques in different simplified, miniaturized and multiplexing devices. The latter issues are discussed in Pt. II of these series.

Dual emission and its λ-ratiometric detection in analytical fluorimetry Pt. II. Exploration in sensing and imaging

“…In Pt. I of these series [1] we explained the weak points of fluorescence intensity measurements at single wavelength. The sensor response signal when it is based on increase (OFF-ON) or decrease (ON-OFF) of intensity is measured in relative units that are proportional to the number of emitted quanta in given experimental conditions and have no absolute value.…”

“…Regarding sensing the anions, the λ-ratiometric approach is highly popular, but most of developed techniques explore the concept of chemodosimetry (see section 2 of Part I [1]). The reason is that a strong hydration or large size of some anions does not allow…”

“…Those are the dyes of 3-hydroychromone (3HC) family that provide multiparametric spectral response to polarity and hydration of their environment [116,117], see section 5.3 of Pt. I [1]. The two-band deconvolution of their excitation spectra and three-band deconvolution of emission spectra [118] allowed obtaining simultaneously the information on the changes in polarity and hydration of probes attached to aggregating molecules.…”

Bright ESIPT emission from 2,6-di(thiazol/oxazol/imidazol-2-yl)phenol derivatives in solution, aggregation and solid states

“…The luminophores based on excited state intramolecular proton transfer (ESIPT) mechanism show some excellent photophysical features such as large Stokes shift, dual emission, excellent photostability and strong solid-state fluorescence [13][14][15]. The fluorophores incorporating AIE and ESIPT may inherit the advantages of both AIE and ESIPT and thus are applicable in more extensive application scope [16].…”

Hole Relaxation Bottlenecks in CdSe/CdTe/CdSe Lateral Heterostructures Lead to Bicolor Emission

“…The complex engineering of nanocrystal compositions permits the development of materials with novel electronic structure that show multicolor emission, which does not follow Kasha’s rule. From a technical standpoint, multicolor emission offers a simplified route to white lighting or potential ratiometric sensing and thermometry . It is also a potential signal of exotic phenomena such as persistent nonequilibrium charge carriers due to slowed relaxation, which is critical for hot carrier extraction , or intraband emitting devices. , In some cases of bicolor emission from nanocrystals, the two emission features may be interpreted as uncoupled emitters separated by a barrier layer (e.g., PbS/CdS/CdSe). , In other cases, dopant atoms such as copper, manganese, , or silver in a semiconductor nanocrystal host result in multicolor emission from the band edge and the localized emission from dopants.…”