Ratiometric fluorescent sensor with large pseudo-Stokes shifts for precise sensing and imaging of pH without...

Area of Science:

• Materials Science
• Nanotechnology
• Analytical Chemistry

Background:

• Fluorescent pH sensors often suffer from background interference due to overlapping emission spectra.
• Developing luminescent materials with large Stokes shifts is crucial for overcoming this limitation.
• Existing methods for achieving large Stokes shifts in fluorescent sensors are limited.

Purpose of the Study:

• To design and synthesize lanthanide-doped fluoride nanoparticles (LFNPs) with exceptionally large pseudo-Stokes shifts.
• To develop a novel fluorescent pH sensor system utilizing these LFNPs for accurate and background-free pH measurements.
• To demonstrate the application of this sensor system in real biological samples.

Main Methods:

• Fabrication of NaGdF4:Ce@NaGdF4:Nd@NaYF4:Eu core-double shells (CDS) lanthanide-doped fluoride nanoparticles (LFNPs).
• Utilizing Gd3+-mediated energy migration and interfacial energy transfer for intense red and NIR emissions.
• Integration of CDS LFNPs with bromocresol green to create a fluorescent sensor film and employing a dual-chip RGB-NIR camera for signal detection.

Main Results:

• Achieved significant pseudo-Stokes shifts of 361 nm (red emission) and 610 nm (NIR emission) under 254 nm irradiation.
• Developed a ratiometric pH sensor with a range of 5-6 (pKa ± 0.5) based on inner-filter effects and intensity ratios.
• Demonstrated accurate pH determination in autofluorescent real samples like algae and serum, with high signal-to-noise ratios.

Conclusions:

• The developed CDS LFNPs offer a promising platform for creating fluorescent sensors with large pseudo-Stokes shifts.
• The novel pH sensor system enables background-free measurement and 2D imaging by separating emission signals from background fluorescence.
• This approach provides a new strategy for precise pH determination in complex and autofluorescent environments.