Wednesday, October 01, 2025

New organic molecule set to transform solar energy harvesting

University of Cambridge

Luminous radical film — image:
A thin film emits red light from radical doublet excited state.
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Credit: Biwen Li - Cavendish Laboratory, University of Cambridge

In a discovery that bridges a century of physics, scientists have observed a phenomenon, once thought to be the domain of inorganic metal oxides, thriving within a glowing organic semiconductor molecule. This breakthrough, led by the University of Cambridge, reveals a powerful new mechanism for harvesting light and turning it into electricity. This could redefine the future of solar energy and electronics, and lead to lighter, cheaper, and simpler solar panels made from a single material.

The research focuses on a spin-radical organic semiconductor molecule called P3TTM. At its centre sits a single, unpaired electron, giving it unique magnetic and electronic properties. This work arises from a collaboration between the synthetic chemistry team of Professor Hugo Bronstein in the Yusuf Hamied Department of Chemistry and the semiconductor physics team led by Professor Sir Richard Friend in the Department of Physics. They have developed this class of molecules to give very efficient luminescence, as exploited in organic LEDs, but the new study, published in Nature Materials, reveals their hidden talent: when brought into close contact, their unpaired electrons interact in a manner strikingly similar to a Mott-Hubbard insulator.

“This is the real magic,” explained Biwen Li, the lead researcher at the Cavendish Laboratory. “In most organic materials, electrons are paired up and don’t interact with their neighbours. But in our system, when the molecules pack together the interaction between the unpaired electrons on neighbouring sites encourages them to align themselves alternately up and down, a hallmark of Mott-Hubbard behaviour. Upon absorbing light one of these electrons hops onto its nearest neighbour creating positive and negative charges which can be extracted to give a photocurrent (electricity).”

The team demonstrated this by creating a solar cell from a P3TTM film. When light hit the device, it achieved a remarkable close-to-unity charge collection efficiency, meaning almost every photon of light was converted into a usable electrical charge. In conventional molecular semiconductor solar cells, the conversion of an absorbed photon into electrons and holes (electricity) can only happen at the interface between two different materials where one acts an electron donor and the other as an electron acceptor, and this compromises overall efficiency. In contrast, for these new materials, after a photon is absorbed, it is energetically “downhill” to move an electron from one molecule to an identical neighbouring molecule, thus creating electrical charges. The energy required for this, often termed the “Hubbard U” is the electrostatic charging energy for double electron occupancy of the molecule that has become negatively charged.

Dr Petri Murto in the Yusuf Hamied Department of Chemistry developed molecular structures that allow tuning of the molecule-to-molecule contact and the energy balance governed by Mott-Hubbard physics needed to achieve charge separation. This breakthrough means that it might be possible to fabricate solar cells from a single, low-cost lightweight material.

The discovery carries profound historical significance. The paper’s senior author, Professor Sir Richard Friend, interacted with Sir Nevill Mott early in his career. This finding emerges in the same year as the 120th anniversary of Mott’s birth, paying a fitting tribute to the legendary physicist whose work on electron interactions in disordered systems laid the groundwork for modern condensed matter physics.

“It feels like coming full circle,” said Prof. Friend. “Mott’s insights were foundational for my own career and for our understanding of semiconductors. To now see these profound quantum mechanical rules manifesting in a completely new class of organic materials, and to harness them for light harvesting, is truly special.”

“We are not just improving old designs” said Prof. Bronstein. “We are writing a new chapter in the textbook, showing that organic materials are able to generate charges all by themselves”.

Mott-Hubbard basic energy levels.

Credit

Biwen Li - Cavendish Laboratory, University of Cambridge

Journal

Nature Materials

DOI

10.1038/s41563-025-02362-z

Article Title

Intrinsic intermolecular photoinduced charge separation in organic radical semiconductors

Article Publication Date

30-Sep-2025

ALS appears to be an autoimmune disease

Researchers show how inflammatory T cells target the brain and trigger cell death

La Jolla Institute for Immunology

image:
The new ALS research was co-led by Professor Alessandro Sette, Dr.Biol.Sci.
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Credit: La Jolla Institute for Immunology

LA JOLLA, CA—Around 5,000 Americans are diagnosed with amyotrophic lateral sclerosis (ALS) each year. About half of patients die within 14 to 18 months of being diagnosed, usually due to breathing failure. The exact cause of ALS has long been unknown.

Now, scientists at La Jolla Institute for Immunology (LJI) and Columbia University Irving Medical Center have uncovered evidence that ALS may be an autoimmune disease. The researchers discovered that inflammatory immune cells, called CD4+ T cells, mistakenly target certain proteins that are part of the nervous system in people with ALS.

"This is the first study to clearly demonstrate that in people with ALS, there is an autoimmune reaction that targets specific proteins associated with the disease," says LJI Professor Alessandro Sette, Dr.Biol.Sci., who co-led the study with Professor David Sulzer, Ph.D., of the Columbia University Irving Medical Center.

The researchers found that people with ALS produce high numbers of CD4+ T cells that target a specific protein (called C9orf72), which is expressed in neurons. This kind of "self-attack" is the defining feature of autoimmune disease.

"There is an autoimmune component to ALS, and this study gives us clues as to why the disease progresses so rapidly," says Sulzer. "This research also gives us a possible direction for disease treatment."

The new study was published recently in Nature.

Scientists discover two patient groups—with different survival times

Although ALS usually progresses quickly, around ten percent of patients live with the disease for ten years or longer. Baseball player Lou Gehrig passed away just two years after his ALS diagnosis. In contrast, physicist Stephen Hawking, Ph.D., lived for 55 years following his diagnosis.

Scientists aren't sure what accounts for this variation. Researchers have linked certain genetic and environmental factors to different ALS "subtypes," but we don't have a broad explanation to account for different survival times in the majority of patients.

The new study suggests the immune system plays a big role in patient survival times.

By examining T cell responses in ALS patients, the researchers were surprised to find two distinct patient groups. One group had shorter predicted survival times. Their inflammatory CD4+ T cells were quick to release inflammatory mediators when they recognized C9orf72 proteins.

The second patient group also had harmful inflammatory CD4+ T cells, but they also had higher numbers of different T cells, anti-inflammatory CD4+ T cells. This second group also had significantly longer projected survival times.

Anti-inflammatory CD4+ T cells are important because they can regulate disease. When the immune system fights a viral infection, for example, it churns out inflammatory T cells to eliminate the infected cells. Once the immune system clears the virus, anti-inflammatory CD4+ T cells step in to prevent overzealous T cells from damaging healthy tissues.

The scientists weren't expecting to observe this same process in ALS patients. The new research suggests that CD4+ T cells may reduce harmful autoimmune responses and slow the progression of ALS.

"This protective T-cell response is strongest in people with a longer predicted survival time," says Emil Johansson, Ph.D., a Visiting Scientist in the Sette Lab.

Next steps in ALS research

Future ALS therapies might boost protective CD4+ T cell responses and dial back harmful inflammation, says LJI Research Technician Tanner Michaelis, who served as the study's first author.

"Hopefully, now that we know the specific target for these immune cells, we can make more effective therapies for ALS," says Michaelis.

"This approach may be applicable for additional disorders such as Parkinson’s, Huntington’s, and Alzheimer’s," adds Sette.

In fact, the new research is just the latest breakthrough in the growing field of neuroimmunology. Recent findings from the Sette Lab have also shown connections between autoimmunity and Parkinson's disease, another disease marked by the death of neurons.

"There are several neurodegenerative diseases where we now have clear evidence of immune cell involvement," says Sette. "This is turning out to be more of a rule of neurodegenerative diseases—rather than an exception."

Additional authors of the study, "Autoimmune response to C9orf72 protein in amyotrophic lateral sclerosis," include Cecilia S. Lindestam Arlehamn, April Frazier, James D. Berry, Merit Cudkowicz, Namita Goyal, Christina Fournier, Allison Snyder, Justin Y. Kwan, Jody Crook, Elizabeth J. Phillips, Simon A. Mallal, John Ravits, Karen S. Marder, and John Sidney.

The study was supported by LJI & Kyowa Kirin, Inc. (KKNA- Kyowa Kirin North America); the Swedish Research Council (grant2024-00175); the Freedom Together Foundation; and in part by the Intramural Research Program, National Institute of Neurological Disorders and Stroke, National Institutes of Health.

DOI: 10.1038/s41586-025-09588-6

Journal

Nature

DOI

10.1038/s41586-025-09588-6

Method of Research

Experimental study

Subject of Research

Cells

Article Title

Autoimmune response to C9orf72 protein in amyotrophic lateral sclerosis

Article Publication Date

1-Oct-2025

Taming the “bad” oxygen

From cell damage to empty batteries, ISTA chemists put singlet oxygen on a leash

Peer-Reviewed Publication

Institute of Science and Technology Austria

Researchers from the Freunberger group at the Institute of Science and Technology Austria (ISTA) have unveiled pivotal insights into the redox chemistry of oxygen and reactive oxygen species (ROS). While some ROS play essential roles in cell signaling, the particularly harmful singlet oxygen damages cells and degrades batteries. For the first time, the team uncovers a way to tune it. The results, published in Nature, could have broad applications, including in energy storage processes.

While “oxidation” sounds oddly similar to “oxygen,” the two words have little in common. Oxidation-reduction—or simply redox—refers to two tightly linked phenomena involving the exchange of electrons in a chemical reaction. The molecule that loses electrons gets oxidized, whereas the one that gains electrons gets reduced. As a result, substances can exist in various redox states. But the redox chemistry of oxygen, one of the most abundant elements, has not yet revealed all its secrets.

From the most reduced to the most oxidized form, the four common redox states of oxygen are called oxide, peroxide, superoxide, and molecular oxygen. Oxide is the form that exists in water, rust, and sand, while peroxide is commonly used in bleaching agents. On the other hand, superoxide is the closest state to molecular oxygen and is necessarily involved in any chemical reaction that consumes or generates it. Peroxide and superoxide have interesting chemical properties, making them so-called “reactive oxygen species,” or ROS. But things get even more interesting with molecular oxygen.

The dark side of the oxygen we breathe

Usually, molecular oxygen is the relatively unreactive dioxygen that we breathe (O₂), known by chemists as “triplet oxygen.” However, it can also exist as the highly reactive “singlet oxygen,” a much more powerful and harmful ROS than superoxide. Apart from causing cell damage, this ‘bad’ oxygen is also a primary source of degradation in human-made oxygen redox systems such as batteries.

Although the ‘good’ triplet and ‘bad’ singlet oxygen have the same chemical structure and overall number of electrons, the way these electrons are distributed makes all the difference. In triplet oxygen, the two outer valence electrons are unpaired: they each occupy an orbital and spin around the oxygen atoms in the same direction. However, in singlet oxygen, the two outer valence electrons occupy the same orbital, moving in opposite directions. This leaves one electron orbital empty and very eager to snatch additional electrons from any organic molecule that crosses its path.

Professor Stefan Freunberger from the Institute of Science and Technology Austria (ISTA) underlines a fundamental problem in the redox chemistry of oxygen: “While superoxide can give rise to either singlet or triplet oxygen, we still did not know what exactly causes the ‘bad’ singlet oxygen to evolve and how it can be tuned.”

When does oxygen take the wrong turn?

Now, a team of researchers led by Freunberger and the recent ISTA PhD graduate Soumyadip Mondal tackles the foundations of how specific ROS arise from other members of the ROS family. These molecules are relevant in a biological context principally for two roles: first, they typically cause cell damage, earning them their infamous reputation. However, these oxygen species also act as signaling agents, regulating a wide range of functions from inflammation to cell growth and all forms of cell death.

Inside cells, the mitochondria, also called the ‘powerhouse of the cell,’ produce superoxide. Since it is toxic to cells, the mitochondria break it down to peroxide, another ROS form that is essential for cell signaling. “We demonstrate the principle of ‘superoxide disproportionation,’ also known as ‘superoxide dismutation,’ in a laboratory setup: If two superoxide molecules ‘shake hands,’ one gets reduced to peroxide and the other one gets oxidized to oxygen,” says Mondal. Inside mitochondria, this reaction is even accelerated by the enzyme superoxide dismutase. “But the question remains: which form of oxygen gets released—the ‘good’ triplet or the ‘bad’ singlet—and under which condition?” According to the team, the pH inside mitochondria might hold the answer.

Batteries inspired by biology

The pH inside our cells varies greatly between the compartments known as organelles. It can range from 4.7 in the acidic lysosomes—the cell’s ‘degradation centers’—to 8.0 inside mitochondria. This alkaline—or basic—environment is essential for the mitochondria so they produce large amounts of ATP, the ‘molecular unit of currency’ for intracellular energy transfer.

The team shows that the driving force for superoxide disproportionation is pH-dependent. “There is a competition between two forms of oxygen gas: if one dominates, the other slows down,” says Freunberger. At a high (basic) pH, the driving force is low, and more ‘good’ triplet oxygen is produced. This is the scenario that plays out inside mitochondria. However, if the environment shifts to an acidic (low) pH, the reaction’s driving force will increase. In this case, the levels of ‘good’ oxygen drop fast, and the ‘bad’ singlet oxygen quickly gains the upper hand. The scientists linked this behavior to the Marcus theory, which describes a reaction’s initially growing speed followed by its counterintuitive slowing down beyond a specific driving force .

In non-biological applications, the team must still find defense mechanisms that will help them tune the reaction and put the ‘bad’ oxygen on a leash. “Biological systems know how to defend themselves from singlet oxygen. Whether we are doing basic chemistry or developing batteries, we must take inspiration from biology to keep the reaction’s driving force low,” says Mondal. The team can do so either by using the right combination of cations and electrolytes in the reaction solution or by developing better defense systems, such as materials that can resist or quench singlet oxygen.

Optimizing green energy processes?

While the Freunberger group specializes in materials electrochemistry and focuses on applications in energy storage devices such as rechargeable batteries, their present findings affect the very foundations of redox chemistry. The fundamental relevance of this research thus promises broad applications in pure chemistry, the life sciences, and energy storage. Beyond advancing rechargeable battery technologies, the findings may also help optimize water splitting, a technique used to produce green fuel hydrogen while releasing molecular oxygen as a byproduct. However, water splitting as a green energy source remains inefficient and often consumes more electrical energy than the generated hydrogen is worth. “How singlet oxygen formation impacts the efficiency of water splitting and potentially degrades the electrolyzer’s carbon carrier remains to be investigated,” says Freunberger. “With our present knowledge, we might soon be able to tame the ‘bad’ oxygen in various applications.”

The campus of the Institute of Science and Technology Austria (ISTA) as seen from above. Located in Klosterneuburg near Vienna, ISTA is an international PHD-granting research institute that brings together leading minds from around the world. It currently hosts around 90 research groups.