Optical pH sensor based on polyaniline sol-gel film immobilized with bromothymol blue and phenol red

Fiber-optic probes for real-time pH monitoring

“…20 Yet, challenges arise from potential pH indicator leakage when physically trapped in the hydrogel or poor response when chemically crosslinked in the hydrogel matrix. 32–35…”

“…20 Yet, challenges arise from potential pH indicator leakage when physically trapped in the hydrogel or poor response when chemically crosslinked in the hydrogel matrix. [32][33][34][35] Neutral red (NR), a widely employed pH indicator in biology, is commonly immobilized in sensitive hydrogels or films. 36 Its commendable performance as a water-soluble colorimetric pH indicator, functioning within the physiological pH range, has positioned NR as a preferred choice in pH sensor applications.…”