Ultra‐pH‐Sensitive Small Molecule Probe Showing a Ratiometric Fluorescence Color Change

Abstract

We synthesized an amphiphilic small molecule 1 by attaching oligo(ethylene glycol) (OEG) and N,N‐diethylamine (DEA) units to a fluorescent dicyanodistyrylbenzene (DCS) core. The molecule is fully soluble in aqueous solution at low pH (pH<4.3) by protonation of the DEA groups; but, above pH 4.3, it self‐assembles to form nanoparticles due to increased hydrophobicity upon deprotonation, leading to a ratiometric fluorescence color change from green emission in the monomeric form (λem,max=538 nm) to red emission in the aggregated form (λem,max=646 nm). It should be noted that the ratio of emission intensities at 538 nm and 646 nm (R=I538/I646) changes drastically about 42‐fold within a very narrow pH range of 4.3–4.6.

Recent Advances in Small Molecule‐Based Intracellular pH Probes

“…[85b] Amphiphilic fluorescent dicyanodistyrylbenzene dye 56 was synthesized for pH sensing. [86] Probe 56 is a ratiometric fluorescence sensor that gives a redshift in fluorescence emission while moving from pH 2.0-7.0. The probe was completely soluble in the water below pH 4.3.…”

Operando laser scattering: probing the evolution of local pH gradients on complex electrode architectures

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A ratiometric fluorescent probe for pH detection based on Ag 2 S quantum dots–carbon dots nanohybrids

“…Continuous online monitoring of pH is considerably significant for bioprocess and environment [ 11 ]. Until now, small molecule probes have been developed to monitor pH using ratiometric fluorescence changing with broad pH response over a range of 1.0 pH unit [ 12 , 13 ]. Several QD-based pH sensors using ratiometric fluorescent sensing have been reported, in which organic dyes were chemically conjugated with QDs as internal reference [ 14 , 15 ].…”