All‐Optical Temperature Sensor Based on Nitrogen‐Vacancy Centers for Dissolution

Abstract The dissolution process of trace chemical reagents plays a critical role in drug development and biochemical reaction monitoring, yet the accompanying minor temperature variations ( 0.5–1 K) remain challenging to resolve using conventional thermometric techniques. This study presents an all‐optical fiber temperature sensor based on nitrogen‐vacancy (NV) centers in diamond, achieving high‐sensitivity temperature measurements via spectral shifts of the zero‐phonon line (ZPL). Experimental results demonstrate a temperature coefficient of and the uncertainty under an excitation power of 1 mW, outperforming commercial thermocouples and thermometers. By monitoring the dissolution dynamics of NaOH, NaCl, and , the sensor quantitatively analyzes kinetic processes using a single‐exponential decay model. The proportional coefficients of thermal changes exhibit a ratio (1.99) closely aligned with the dissolution enthalpy ratio (1.73). With micrometer‐scale spatial resolution and millisecond‐level temporal response, this non‐invasive sensor offers a robust platform for real‐time monitoring of localized thermal effects in microscale reactions, demonstrating significant potential for applications in cellular biochemistry and microfluidic systems.