Researchers at the University of Houston have developed a noncontact optical method capable of measuring the temperature of hot surfaces with an accuracy exceeding 1°C (Device, doi: 10.1016/j.device.2024.100467). This advanced technique aims to improve the understanding of photothermal catalysts, which use laser heating to drive chemical reactions.
The Emissivity Challenge Houston
Photoexcited electrons are believed to lower the activation energy in photothermal catalysts, but precise temperature measurements are crucial for understanding their role. Infrared thermometers, known for their speed and sensitivity, are commonly used because they measure temperature without interfering with the light-driven reaction. However, these devices measure temperature by evaluating the thermal radiation intensity and the material’s emissivity—the efficiency of emitting heat compared to a perfect blackbody. Emissivity varies with both wavelength and temperature, which can affect measurement accuracy. While measuring infrared emission at different wavelengths can reduce uncertainty, it requires complex modeling to achieve reliable results.
Enhanced Accuracy
Houston The new approach developed by the researchers utilizes a near-infrared spectrometer to capture the emission spectrum from 950 to 1600 nm. To calibrate the system, they first record the spectrum at a known temperature (400°C) and compare it to the theoretical blackbody curve. This comparison helps in normalizing the data, allowing the temperature to be determined by matching the measured spectrum to the blackbody formula.
Houston The technique was tested on a silver heating stage, achieving temperature accuracy of better than 1°C across a range of 200 to 550°C. The method was also applied to measure the surface temperature of a powder catalyst heated by a laser, with a thermocouple placed 100 µm below the surface. This measurement showed a significant temperature gradient within the catalyst—over 320°C from the surface to the thermocouple at a laser power of 500 mW—consistent with simulation results.
Houston Lead author Jiming Bao highlights the technique’s advantages: “This method overcomes the limitations of traditional thermal cameras and infrared thermometers. It offers a more accurate way to understand non-thermal contributions in photothermal reactions and is valuable in fields requiring precise measurements of high surface temperatures.
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