Explain the principles of pH-sensitive dyes and their applications in indicators, sensors, and medical diagnostics.

pH-sensitive dyes, also known as pH indicators, change color in response to changes in pH levels of their surroundings. They are commonly used in applications such as acid-base titrations, chemical analysis, and monitoring pH levels in biological samples. pH-sensitive dyes exhibit different colors at different pH ranges due to changes in their protonation or deprotonation states, making them valuable tools for visualizing and quantifying acidity or alkalinity in various environments.