Enhancing Photoinduced Electron Transfer Efficiency of Fluorescent pH-Probes with Halogenated Phenols

Abstract

Photoinduced electron transfer (PET), which causes pH-dependent quenching of fluorescent dyes, is more effectively introduced by phenolic groups than by amino groups which have been much more commonly used so far. That is demonstrated by fluorescence measurements involving several classes of fluorophores. Electrochemical measurements show that PET in several amino-modified dyes is thermodynamically favorable, even though it was not experimentally found, underlining the importance of kinetic aspects to the process. Consequently, the attachment of phenolic groups allows for fast and simple preparation of a wide selection of fluorescent pH-probes with tailor-made spectral properties, sensitive ranges, and individual advantages, so that a large number of applications can be realized. Fluorophores carrying phenolic groups may also be used for sensing analytes other than pH or molecular switching and signaling.

Design, Synthesis and Photochemical Properties of a Phenalenone‐Based pH Sensor: Switchable pH Sensing in Four Detectable Channels

“…Fluorescence quantum yields (Φf) for compound 1 (0.075) was calculated from integrating emission area under the fluorescence spectra at pH 7.2,24 using tryptophan as the standard (λ em ; 300–380 nm, Φf=0.14 in water at pH 7.2 at 25 °C). The quantum yield is comparable to some of the recently reported sensors ,,. Emission intensities in different solvents have been examined.…”

“…Easy and cost‐effective application of the sensor has been established too. Phenol (phenoxide when deprotonated) can act as a photoinduced electron transfer (PET) group, thus showing quenching in emission intensity when attached with different fluorophores . Thus we anticipate compound 1 (Scheme ) to show pH‐dependent emission changes by PET while giving us an ample opportunity to investigate the additional changes in the photochemical properties imparted by the combination of phenol and the phenalenone moiety.…”

Fluorescence pH Probes Based on Photoinduced Electron Transfer Quenching of Long Fluorescence Lifetime Triangulenium Dyes

“…While this probably is the reason for the ability of DAOTA‐M2 to discriminate between different DNA topologies, it is an undesired complication for a pH probe. Thus, to find the optimal pH sensitive PET quencher motif for the azaoxatriangulenium dyes we turn to the less used but more efficient, phenol group (Figure ) ,…”

Photoinduced Electron Transfer-Based Fluorescence Quenching Combined with Rolling Circle Amplification for Sensitive Detection of MicroRNA

“…PET is an excited state electron transfer form an electron-rich species (a donor) to an electron deficient species (an acceptor), and PET has been recently applied to design some fluorescence biosensing systems. [40][41][42][43][44] Guanine can efficiently quench the fluorescence of many fluorophores via PET. [43,44] In our work, mmu-miR-433-5p (mir-433) was taken as a model target for the assay, and the carboxyfluorescein (FAM)-labeled ssDNA was used as signal probe.…”