A simple NIR fluorescent probe for detecting pH in actual water samples and cells

Area of Science:

• Analytical Chemistry
• Biophysical Chemistry
• Materials Science

Background:

• Accurate pH monitoring is crucial in various scientific disciplines, including chemistry and biology.
• Developing novel fluorescent probes with high sensitivity and water solubility is an ongoing research area.
• Existing probes may have limitations in aqueous environments or specific pH ranges.

Purpose of the Study:

• To introduce a novel, water-soluble fluorescent probe (FC) for rapid and accurate pH sensing.
• To investigate the pH sensing mechanism of the probe in acidic environments.
• To demonstrate the probe's utility in real-world applications, such as water sample analysis and intracellular pH detection.

Main Methods:

• Synthesis and characterization of the novel fluorescent probe (FC).
• Investigation of the probe's fluorescence response to pH changes using spectroscopy.
• Theoretical calculations and nuclear magnetic titration to elucidate the sensing and response mechanisms (photoinduced electron transfer - PET).
• Application of the probe for pH measurements in aqueous samples and biological cells.

Main Results:

• The developed probe (FC) exhibits rapid response to pH changes.
• FC accurately measures pH in the weakly acidic range of 4.0 to 6.6.
• The probe demonstrates excellent water solubility, enabling measurements in aqueous systems without organic solvents.
• Fluorescence quenching in acidic conditions is attributed to the protonation of the pyridine moiety via a photoinduced electron transfer (PET) mechanism.
• Successful application of FC for monitoring pH in real water samples and detecting intracellular acidity.

Conclusions:

• FC is a highly effective and water-soluble fluorescent probe for rapid pH determination in the 4.0-6.6 range.
• The probe's mechanism, based on PET, is well-understood and validated.
• FC offers a promising tool for environmental monitoring and biological research requiring precise pH measurements in aqueous media.