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:
Mathematician from HSE University–Nizhny Novgorod Solves Equation Considered Unsolvable in Quadratures Since 19th Century
Mathematician Ivan Remizov from HSE University–Nizhny Novgorod and the Institute for Information Transmission Problems of the Russian Academy of Sciences has made a conceptual breakthrough in the theory of differential equations. He has derived a universal formula for solving problems that had been considered unsolvable in quadratures for more than 190 years. This result fundamentally reshapes one of the oldest areas of mathematics and has potential to have important implications for fundamental physics and economics. The paper has been published in Vladikavkaz Mathematical Journal.
Scientists Reveal How Language Supports Complex Cognitive Processing in the Brain
Valeria Vinogradova, a researcher at HSE University, together with British colleagues, studied how language proficiency affects cognitive processing in deaf adults. The study showed that higher language proficiency—regardless of whether the language is signed or spoken—is associated with higher activity and stronger functional connectivity within the brain network responsible for cognitive task performance. The findings have been published in Cerebral Cortex.
HSE AI Research Centre Simplifies Particle Physics Experiments
Scientists at the HSE AI Research Centre have developed a novel approach to determining robustness in deep learning models. Their method works eight times faster than an exhaustive model search and significantly reduces the need for manual verification. It can be applied to particle physics problems using neural networks of various architectures. The study has been published in IEEE Access.
Scientists Show That Peer Influence Can Be as Effective as Expert Advice
Eating habits can be shaped not only by the authority of medical experts but also through ordinary conversations among friends. Researchers at HSE University have shown that advice from peers to reduce sugar consumption is just as effective as advice from experts. The study's findings have been published in Frontiers in Nutrition.
HSE University Develops Tool for Assessing Text Complexity in Low-Resource Languages
Researchers at the HSE Centre for Language and Brain have developed a tool for assessing text complexity in low-resource languages. The first version supports several of Russia’s minority languages, including Adyghe, Bashkir, Buryat, Tatar, Ossetian, and Udmurt. This is the first tool of its kind designed specifically for these languages, taking into account their unique morphological and lexical features.
HSE Scientists Uncover How Authoritativeness Shapes Trust
Researchers at the HSE Institute for Cognitive Neuroscience have studied how the brain responds to audio deepfakes—realistic fake speech recordings created using AI. The study shows that people tend to trust the current opinion of an authoritative speaker even when new statements contradict the speaker’s previous position. This effect also occurs when the statement conflicts with the listener’s internal attitudes. The research has been published in the journal NeuroImage.
Language Mapping in the Operating Room: HSE Neurolinguists Assist Surgeons in Complex Brain Surgery
Researchers from the HSE Center for Language and Brain took part in brain surgery on a patient who had been seriously wounded in the SMO. A shell fragment approximately five centimetres long entered through the eye socket, penetrated the cranial cavity, and became lodged in the brain, piercing the temporal lobe responsible for language. Surgeons at the Burdenko Main Military Clinical Hospital removed the foreign object while the patient remained conscious. During the operation, neurolinguists conducted language tests to ensure that language function was preserved.
AI Overestimates How Smart People Are, According to HSE Economists
Scientists at HSE University have found that current AI models, including ChatGPT and Claude, tend to overestimate the rationality of their human opponents—whether first-year undergraduate students or experienced scientists—in strategic thinking games, such as the Keynesian beauty contest. While these models attempt to predict human behaviour, they often end up playing 'too smart' and losing because they assume a higher level of logic in people than is actually present. The study has been published in the Journal of Economic Behavior & Organization.
Scientists Discover One of the Longest-Lasting Cases of COVID-19
An international team, including researchers from HSE University, examined an unusual SARS-CoV-2 sample obtained from an HIV-positive patient. Genetic analysis revealed multiple mutations and showed that the virus had been evolving inside the patient’s body for two years. This finding supports the theory that the virus can persist in individuals for years, gradually accumulate mutations, and eventually spill back into the population. The study's findings have been published in Frontiers in Cellular and Infection Microbiology.
HSE Scientists Use MEG for Precise Language Mapping in the Brain
Scientists at the HSE Centre for Language and Brain have demonstrated a more accurate way to identify the boundaries of language regions in the brain. They used magnetoencephalography (MEG) together with a sentence-completion task, which activates language areas and reveals their functioning in real time. This approach can help clinicians plan surgeries more effectively and improve diagnostic accuracy in cases where fMRI is not the optimal method. The study has been published in the European Journal of Neuroscience.