Cerium Glows Yellow: Chemists Discover How to Control Luminescence of Rare Earth Elements
.jpg "Cerium Glows Yellow: Chemists Discover How to Control Luminescence of Rare Earth Elements")
Researchers at HSE University and the Institute of Petrochemical Synthesis of the Russian Academy of Sciences have discovered a way to control both the colour and brightness of the glow emitted by rare earth elements. Their luminescence is generally predictable—for example, cerium typically emits light in the ultraviolet range. However, the scientists have demonstrated that this can be altered. They created a chemical environment in which a cerium ion began to emit a yellow glow. The findings could contribute to the development of new light sources, displays, and lasers. The study has been published in Optical Materials.
Rare earth elements are used in microelectronics, LEDs, and fluorescent materials because of their ability to emit light in precisely defined colours. This depends on how their electrons behave when absorbing and releasing energy.
When an atom absorbs energy—such as from light or an electric current—one of its electrons can be excited to a higher energy level. However, this excited state is unstable, and after a short time, the electron returns to its original level, releasing the excess energy as light. This process is known as luminescence.
In rare earth elements, the glow results from electron transitions between 4f orbitals—regions around the atomic nucleus where electrons can reside. Typically, the energy of these transitions is fixed, meaning the colour of the glow remains constant: cerium emits invisible ultraviolet light, while terbium emits green. The 4f orbitals are situated deep within the atom and interact minimally with the surrounding environment. In contrast, the 5d orbitals are sensitive to external influences but generally do not contribute to the luminescence of lanthanides due to their excessively high energy.
However, scientists from HSE University and the Institute of Petrochemical Synthesis of the Russian Academy of Sciences have demonstrated that the colour of the radiation can be altered by adjusting the chemical environment of the metals. They synthesised cerium, praseodymium, and terbium complexes using organic ligands—molecules that surround metal ions. These ligands shape the geometry of the complex and influence its properties. In all cases, three cyclopentadienyl anions were symmetrically arranged around the metal. These anions consist of regular pentagons of carbon atoms, to which large organic fragments are attached, providing the required structure for the complex. This environment generates a specific electrostatic field around the ion, which alters the energy of the 5d orbitals and, consequently, affects the luminescence spectrum.
Daniil Bardonov
'Previously, a change in the colour of the glow had been observed, but the underlying mechanism was not understood. Now, in collaboration with our physicist colleagues, we have been able to understand the mechanism behind this effect. We deliberately designed compounds with an electronic structure that is atypical for lanthanides. Rather than focusing on a single example, we synthesised a series of compounds from cerium to terbium to observe how their properties change and to identify common patterns,' comments Daniil Bardonov, a master's student at the HSE Faculty of Chemistry.
In conventional compounds, cerium emits ultraviolet light with wavelengths between 300 and 400 nanometres. In the new complexes, its emission shifted to the red range, reaching up to 655 nanometres. This indicates that the energy gap between the 4f and 5d levels has decreased. A similar rearrangement of electronic levels was observed in the other lanthanides studied, also resulting in changes to their luminescence.
Dmitrii Roitershtein
'To understand how this process works, it’s important to first grasp the mechanism of energy transfer. Typically, a ligand molecule absorbs ultraviolet light, enters an excited state, and then transfers this energy to the metal atom, causing it to emit light,' explains Dmitrii Roitershtein, Academic Supervisor of the Chemistry of Molecular Systems and Materials Programme and co-author of the paper. 'However, in the new compounds, the process occurred differently: energy was transferred not directly to the 4f electrons, but via an intermediate 5d state.'
The researchers believe that being able to predict the luminescence spectrum will make it possible to design materials with desired properties more efficiently by eliminating the need for time-consuming trial and error. This could facilitate the creation of new and advanced light sources.
'We were able to demonstrate exactly how the environment of an atom influences its electronic transitions and lanthanide luminescence,' says Fyodor Chernenkiy, bachelor's student at the HSE Faculty of Chemistry. 'We can now intentionally select the structure of compounds to control luminescence and produce materials with specific optical properties.'
See also:
Resource Race and Green Transition: Three Unexpected Conclusions from Foresight Centre’s Research on Climate and Poverty
Beneath the surface of green energy—which most people associate with solar panels, electric vehicles, and reduced CO2 emissions—lies a complex web of geopolitical interests, international inequality, and resource constraints. Researchers from the Laboratory for Science and Technology Studies (LST) at the HSE ISSEK Foresight Centre have published a series of articles in leading international journals on hidden and overt conflicts surrounding critically important metals and minerals, as well as related processes in the energy sector.
Immersion in Second Language Environment Influences Bilinguals’ Perception of Emotions
Researchers at the Cognitive Health and Intelligence Centre at the HSE Institute for Cognitive Neuroscience have discovered how bilingual individuals process emotional words in their native (first) and non-native (second) languages. It was found that the link between word meaning and bodily sensations is weaker in a second language than in a first language. However, the more a person is immersed in a language environment, the smaller this difference becomes. The article has been published in Language, Cognition and Neuroscience.
Researchers Find More Effective Approach to Revealing Majorana Zero Modes in Superconductors
An international team of researchers, including physicists from HSE MIEM, has demonstrated that nonmagnetic impurities can help more accurately reveal Majorana zero modes—quantum states considered promising building blocks for quantum computing. The researchers found that these impurities shift the energy levels that typically obscure the Majorana signal, while leaving the mode itself largely unaffected, thereby making its spectral peak more distinct. The study has been published in Research.
New Development by HSE Scientists Helps Design Reliable Electronics Faster at a Lower Cost
Scientists from HSE MIEM have developed a new approach to modelling electrothermal processes in high-power electronic circuits on printed circuit boards (PCB). The method allows engineers to quickly and accurately predict how electronic components heat up during operation, helping prevent overheating and potential failures. The results have been published in Russian Microelectronics.
The Future of Cardiogenetics Lies in Artificial Intelligence
Researchers from the AI and Digital Science Institute at the HSE Faculty of Computer Science have developed a program capable of analysing regions of the human genome that were previously inaccessible for accurate interpretation in genetic testing. The program adapts large generative AI (GenAI) models for cardiogenetics to predict how specific mutations affect the function of individual genes.
HSE Researchers: Young Russians Have Sufficient Knowledge About Money but Lack Money Management Skills
Adolescents and young adults in Russia today are well versed in financial terminology: they know what bank cards, loans, interest rates, and online payments are. However, as researchers at HSE University have found, real money-management skills remain poorly developed among most young people. The study ‘Financial Literacy, Financial Culture, and Financial Autonomy of Youth’ has been published in Monitoring of Public Opinion: Economic and Social Changes.
Why Weaker Competitors Give Up—and How to Keep Them in the Game
Anastasia Antsygina, Assistant Professor at HSE University’s Faculty of Economic Sciences, has developed a prize distribution model that maximises competitor engagement. She proposed revising the traditional ‘winner-takes-all’ approach and, in certain cases, offering a small reward even to those who have lost. According to her, this could increase participant motivation and make the competition more intense. The findings of her research were published in the Economic Theory journal.
HSE Researchers Compile Scientific Database for Studying Children’s Eating Habits
The database created at HSE University can serve as a foundation for studying children’s eating habits. This is outlined in the study ‘The Influence of Age, Gender, and Social-Role Factors on Children’s Compliance with Age-Based Nutritional Norms: An Experimental Study Using the Dish-I-Wish Web Application.’ The work has been carried out as part of the HSE Basic Research Programme and was presented at the XXVI April International Academic Conference named after Evgeny Yasin.
New Foresight Centre Study Identifies the Most Destructive Global Trends for Humankind
A team of researchers from the HSE International Research and Educational Foresight Centre has examined how global trends affect the quality of human life—from life expectancy to professional fulfilment. The findings of the study titled ‘Human Capital Transformation under the Influence of Global Trends’ were published in Foresight.
Scientists Develop Algorithm for Accurate Financial Time Series Forecasting
Researchers at the HSE Faculty of Computer Science benchmarked more than 200,000 model configurations for predicting financial asset prices and realised volatility, showing that performance can be improved by filtering out noise at specific frequencies in advance. This technique increased accuracy in 65% of cases. The authors also developed their own algorithm, which achieves accuracy comparable to that of the best models while requiring less computational power. The study has been published in Applied Soft Computing.