Highly sensitive fluorescent pH microsensor based on the ratiometric dye pyranine immobilized on silica microparticles

TL;DR

This paper presents a novel noncovalent method to immobilize the pH-sensitive dye pyranine on silica microparticles, resulting in highly sensitive and stable pH microsensors suitable for various applications.

Contribution

It introduces a new immobilization technique that maintains pyranine's pH sensitivity and stability on silica microparticles, overcoming previous challenges with charge interactions.

Findings

Surface charge influences dye sensitivity on silica.

The immobilization method preserves dye sensitivity and stability.

The microsensors show high pH responsiveness and long-term stability.

Abstract

Pyranine (HPTS) is a remarkably interesting pH sensitive dye that has been used for plenty of applications. Its high quantum yield and extremely sensitive ratiometric fluorescence against pH change makes it a very favorable for pH sensing applications and development of pH nano/microsensors. However, its strong negative charge and lack of easily modifiable functional groups makes it difficult to be used with charged substrates such as silica. This study reports a noncovalent HPTS immobilization methodology on silica microparticles that considers the retention of pH sensitivity as well as long term stability of the pH microsensors. The study emphasizes on importance of surface charge for governing the sensitivity of the immobilized HPTS dye molecules on silica microparticles. Importance of methodology of immobilization that preserves the sensitivity as well as stability of the microsensors is also assessed.