New phosphorescence spectroscopy techniques come to shed light on the recent progress in the study of water ice and its interaction with small organic molecules. Scientists from the University of Science and Technology of China managed to show that crystallinity in water ice may be perturbed by ethylene glycol and other substances, which changes its physical-chemical properties.
The role of ice in astrobiology and the origins of life has long been recognized, due in large part to the fact that it can concentrate organic molecules within its crystal lattice. Traditionally, methods for the analysis of organic compounds within the ice matrix rely on absorption-based spectroscopic techniques like Raman and infrared spectroscopy, which have intrinsic sensitivities and precisions.
A team from USTC, including Profs Guoqing Zhang, Shiyong Liu, Xiaoguo Zhou, and Researcher Xuepeng Zhang, has proposed the first application of phosphorescent probes in the detection of microstructural changes of water ice. The approach, published in Angewandte Chemie, relies on helps from a phosphorescent probe, acridinium iodide, which alerts, due to its emission properties, about crystalline and amorphous ice states influenced by trace amounts of water-soluble organic molecules.
Also read: Why is Knowledge Important in Education?
One of the emission-based methods developed by the team is monitoring the hydration state of ADI within water ice. Under amorphous ice conditions—in a setup where orderly crystal formation is hindered due to low temperature—ADI molecules would emit highly visible greenish-yellow afterglow as it shows long-lived phosphorescence, resulting from the separation of AD+ cation and I– anion within the bound water molecules. In contrast to ordered crystalline ice, where ADI molecules aggregate, the appearance of short-lived red phosphorescence arises due to the heavy atom effect from iodine.
Phosphorescence spectroscopy showed dramatic changes in the spectroscopy that occurred upon inclusion of small organic molecules, such as ethylene glycol into water ice doped with ADI. An amount as trace as 0.1% of EG produced prominent changes in the fluorescence and phosphorescence bands of ADI, which reflect structural transitions from undissolved aggregates to dissolved ion states.
The authors used the following advanced imaging techniques for the validation of their findings: low-temperature scanning electron microscopy and low-temperature Raman spectroscopy. Cryo-SEM images confirmed the formation of porous microstructures in the water ice matrix with the addition of EG, consistent with what was observed using phosphorescence spectroscopy. On the other hand, LT-Raman spectra revealed shifts in O-H vibration frequencies of water ice, further confirming a crystalline-to-glassy state transition upon the addition of EG.
These findings speak to more far-reaching implications than simple chemistry and have applications in astrobiology and planetary science. They realize more generally the power of phosphorescence spectroscopy but reach into potential applications of studies on interactions between water, ice, and organics at lower concentrations and wider temperature ranges.
In a word, the pioneering work of the USTC team in using phosphorescence spectroscopy pushed a step further toward the understanding of intricate interplay between water ice and organic molecules. Their findings not only enhance our knowledge regarding ice microstructures but also pave the way for future research aimed at deciphering the origins of life and habitability in the cosmos. With the continuous batch of results from evolving technology, phosphorescence spectroscopy will turn out to be a very powerful tool in unlocking secrets in icy worlds and their potentials for life.
Phosphorescence spectroscopy offers studies on water-ice molecular interactions with small organic molecules, hence an improvement in techniques of analysis towards planetary science and astrobiology. Understanding the physical and chemical properties of ice has had special status throughout history because it is so prevalent in the Solar System and probably supports extraterrestrial life. The ability to better understand the characterization of ice microstructure and its responses to environmental stimuli, such as the presence of organic compounds, opens up prospects for the exploration of icy moons and comets or other celestial bodies where ice is abundant.
In a development departing from traditional spectroscopic means, hurriedly trying to make out sensitivity issues in the study of low-concentration organic molecules in an icy environment, Prof. Guoqing Zhang’s team from USTC used phosphorescent probes and succeeded. The finding by the scientists showed that it had the ability to detect very minute changes in the structure of water ice through minute traces of organics, significantly altering its crystalline integrity.
The results now published in Angewandte Chemie underline how chemistry, physics, and planetary sciences come together in space research nowadays. The collaborative effort that Prof Zhang and his team have led exemplifies the synergy needed to push forward our understanding of basic processes working surfaces and environments beyond Earth.
The spectral analyses the USTC team did test provides a fine grid ricocheting the next investigations on the dynamics of the ice-organic interactions. In uncovering how ethylene glycol and similar molecules disrupt the crystalline order of water ice, researchers get insights into which chemical dynamics could have influenced icy body formation and evolution through the Solar System’s history.
The broader implications of the study reach beyond planetary science into an understanding of Earth’s cryospheric processes and their ecological significance. Terrestrial ice processes, very similar to those modeled here, would inform climate change impacts, permafrost dynamics, and biogeochemical cycling of organic compounds in polar regions.
Looking ahead, the integration of phosphorescence spectroscopy into planetary exploration missions could potentially enhance the detection and identification of organic molecules in extreme environments. Such technological development could have an important role in future spacecraft missions that will launch toward icy moons, like Europa and Enceladus, likely unveiling new evidence for habitable conditions and life beyond Earth.
In a nutshell, the pioneering work by Prof. Zhang’s team presents a quantum leap forward in using advanced spectroscopic tools to probe intrinsic interactions between water ice and organic molecules. As planetary exploration keeps completing its sweep, the contributions that such studies will make toward the understanding of the Solar System’s icy bodies and their habitability will be an inspiration for further exploration and discovery in astrobiology.
Reference: “Water-Ice Microstructures and Hydration States of Acridinium Iodide Studied by Phosphorescence Spectroscopy” by Hongping Liu, Hao Su, Ning Chen, Jie Cen, Jiajia Tan, Baicheng Zhang, Xiaoyu Chen, Aoyuan Cheng, Shengquan Fu, Xiaoguo Zhou, Shilin Liu, Xuepeng Zhang, Shiyong Liu, Yi Luo and Guoqing Zhang, 11 April 2024, Angewandte Chemie International Edition.
Source: SciTechDaily
Read More: DignityHub