Development of a DualEmission Laser-Induced Fluorescence (DELIF) Method for Long-Term Temperature Measurements.

Area of Science:

• Optical diagnostics
• Fluorescence spectroscopy
• Temperature measurement

Background:

• Traditional dual-emission laser-induced fluorescence (DELIF) methods suffer from fluorescent dye degradation over time, limiting their use for long-term temperature monitoring.
• The photobleaching of fluorescent dyes is a significant challenge for continuous and stable measurements.
• Existing DELIF techniques are unsuitable for applications requiring prolonged, accurate temperature data.

Purpose of the Study:

• To develop a modified DELIF method for accurate long-term temperature measurements.
• To address the limitations of dye photobleaching in conventional DELIF techniques.
• To investigate the use of fluorescence intensity ratios for stable temperature sensing.

Main Methods:

• Investigated fluorescence intensity characteristics of Fluorescein disodium and Rhodamine B from 10-60 °C.
• Utilized two high-speed monochrome CMOS cameras and narrow bandpass filters for spectral analysis.
• Developed a novel DELIF approach based on the ratio of fluorescence intensities at specific wavelengths (λ and λ ± 10 nm).

Main Results:

• The fluorescence intensity ratio of dyes (e.g., Rhodamine B at 589 nm and 600 nm) showed high sensitivity to temperature but was independent of excitation time.
• Achieved a high temperature resolution of ≤0.042 °C using Rhodamine B.
• Demonstrated negligible variation in the fluorescence intensity ratio over 180 min of excitation, with a measurement uncertainty of 0.045 °C at 20 °C.

Conclusions:

• The proposed DELIF method, utilizing fluorescence intensity ratios, enables highly accurate and stable long-term temperature measurements.
• This approach effectively overcomes the photobleaching limitations of traditional DELIF methods.
• The findings support the application of this modified DELIF technique in scenarios requiring continuous, precise temperature monitoring.