Balance Center Characteristic for Ultrafine Spectroscopic Analysis Using Rhodamine 6G Fluorescence Sensing as a Case Study.

Although Rhodamine 6G (R6G) has previously been considered insensitive to pH and stress, with no established applications in sensing these specific parameters, this article presents a breakthrough by re-evaluating its potential as active materials for temperature, pH, and stress sensing. This breakthrough is achieved by employing "balance center" instead of peak maximum or mean wavelength for characterizing the spectral emission band. To verify the improvement, R6G/resin composite samples were prepared. Then the balance center among all the spectral characteristics ensured the most precise identification of the fluorescence band shifts caused by any environmental changes onto the samples. Sensitivities of the prototype sensors with balance center output were calibrated as 0.0653(3) nm/°C in the range of 20 ~ 60 °C, 0.339(8) nm/pH in the pH range of 5.71 ~ 9.44, and - 0.63(2) nm/MPa (equivalently 18 cm^-1/MPa) in the stress range of 0.07 ~ 1.43 MPa, respectively. Corresponding resolutions of the sensing systems were determined as 0.15 °C, 0.18 pH, and 0.03 MPa. These example sensors can be utilized in cytobiology research, demonstrating the potential for extensive sensing applications with a wide range of other fluorescent dyes.