Observing variation in the structural dynamics of 1 nm single molecules at room temperature for the first time

(Left) Illustration of isolated particles sandwiched between layers of gold and aluminum oxide using enhanced nanodissection (right) depicting the vibrational patterns of a bright crystal blue molecule (BCB) with different conformations. credit: Postech

The long-awaited dream of chemists to observe the structural dynamics of a single molecule is now possible. Single molecules with a size of about 1 nm exist in a volatile state under ambient conditions. Given that the coronavirus, which is about 100 nanometers in size, spreads rapidly in the air shows how difficult it is to monitor a single molecule. Recently, a Korean research team discovered a reliable way to monitor single molecules at room temperature by covering them with a thin insulating layer, like a blanket.

The research team led by Professor Kyung Duck Park and Ph.D. Candidate Mingu Kang (Department of Physics) at POSTECH, in collaboration with Professor Yung Doug Suh (Department of Chemistry) at Ulsan National Institute of Science and Technology (UNIST), has successfully investigated the morphology (arrangement of atoms in a molecule) of individual molecules at room temperature for the first time, Which provides a close look at the structural dynamics of a single molecule, the basic unit of all things including humans.

In-depth analysis using Raman scattering signals, known as a molecular ‘fingerprint’, is difficult for molecules exposed to air due to ongoing chemical reactions and molecular motions. Ultra-low temperature (below -200 °C) and vacuum conditions have been widely used for single molecule studies to prevent the above problems, however the formations have many limitations in terms of technical difficulties and environmental conditions.

To get around this, the research team placed a single molecule on a substrate coated with a thin layer of gold and covered it with a very thin layer of aluminum oxide (Al2a3). The molecule trapped between the layers of gold and aluminum oxide is isolated from its surroundings, which leads to chemical reactions and suppressed molecular motions.

The stable molecule is then observed through the high-sensitivity nanoendoscopy developed by the research team. The use of the method allows for accurate detection of weak optical signals of a single molecule, due to the optical antenna effect of the sharp metallic tip. By this, the resolution limit for general optical microscopy (~500 nm) was overcome to clearly distinguish the 1 nm size-matched heterogeneity. single molecules And check if they are standing vertically or horizontally.

Mingu Kang of POSTECH says that “while the James Webb Space Telescope can observe the farthest point in the observable universe to reveal the origin of the universe, our nanoendoscopy of a single individualmolecules He notes the smallest unit to reveal the origin of life.”

The work could reveal the molecular conformation of proteins and DNA with nanometer-level precision, leading to the identification of the cause of incurable diseases and the development of treatments for such conditions. In addition, a sample is covered with an extension thin layer It can be easily applied in Room temperature or even higher temperatures for single molecule Studies and its applications.

The study was recently published in Nature Connections.


Making and breaking chemical bonds in ‘nano-confined’ single molecules


more information:
Mingu Kang et al, The conformational inhomogeneity of molecules adsorbed on a gold surface at room temperature, Nature Connections (2022). DOI: 10.1038 / s41467-022-31576-x

Provided by Pohang University of Science and Technology (POSTECH)

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