A technology has been developed that can simultaneously observe the ultra-fine structure and temperature changes of a material in real time, and it is expected that it will be used to develop advanced materials by analyzing the correlation between the specific structure and thermodynamic properties of a sample.

UNIST (President Jong-Rae Park) announced on the 2nd that Professor Oh-Hoon Kwon's team from the Department of Chemistry has developed a general-purpose 'nano-thermometer' that can precisely measure the temperature of microscopic samples inside a transmission electron microscope.

The developed nanothermometer measures temperature by analyzing the cathode ray emission spectrum emitted by nanoparticles that act as thermometers when exposed to an electron beam.

Transmission electron microscopes use electron beams as light to observe the microstructure of a sample, and these electron beams are also used to measure temperature.

The existing nanothermometers can be used in conjunction with observation of microstructural changes using a real-time (in situ) transmission electron microscope, but they have the inconvenience of having to be calibrated each time they are used depending on the intensity of the electron beam.

In this study, the research team improved the reliability and versatility of the nanothermometer by changing the material. Dysprosium ion (Dy3+) was selected as the cathode ray emitter.

“This is because the distribution of quantum states appearing in the cathodoluminescence spectrum of dysprosium ions follows the Boltzmann distribution, which depends only on the temperature, regardless of the intensity of the electron beam,” explained first author Park Won-woo.

The Boltzmann distribution is a statistical distribution that describes the phenomenon that the proportion of high-energy quantum states increases as temperature increases.

The research team synthesized 150 nm-sized nano-thermometer particles by doping dysprosium ions into yttrium vanadate (YVO4), which can withstand the high energy of electron beams.

When the developed thermometer was used to measure the ambient temperature from -170℃ to 50℃, it showed a measurement error of within approximately 4℃.

We also succeeded in raising the temperature by irradiating the sample with a laser beam and tracking the spatial distribution of the temperature change.

This result proves the effectiveness of the technology that can simultaneously observe temperature and structure changing in real time due to external stimuli.

Professor Kwon Oh-hoon said, “By redesigning the material of the nano-thermometer, we have greatly improved the reliability of temperature measurement and secured versatility,” adding, “It will also contribute to the development of secondary battery materials and display materials that are sensitive to temperature depending on charging and discharging.”

This study was co-first authored by Dr. Pavel K. Olshin, and co-authored by Professor Ye-Jin Kim, a graduate of UNIST who joined the Department of Chemistry at Seoul National University last year.

The research results were published on the 10th of last month in ACS Nano, an authoritative academic journal in the field of nanotechnology. The research was conducted with support from the Samsung Future Technology Promotion Project and the National Research Foundation of Korea.