Dukovic

New ‘Molecular Dam’ Stops Energy Leaks in Nanocrystals

Daniel Morton — Tue, 21 Oct 2025 19:17:19 +0000

New ‘Molecular Dam’ Stops Energy Leaks in Nanocrystals Daniel Morton Tue, 10/21/2025 - 13:17

Daniel Morton

A molecular engineering breakthrough could make key light-driven reactions over 40 times more efficient.

A collaborative team of scientists from the ��, the University of California Irvine, and Fort Lewis College, led by RASEI Fellow Gordana Dukovic, has found a way to slow energy leaks that have impeded the use of tiny nanocrystals in light-driven chemical and energy applications. As described in a new article published in the journal Chem, the team has used a molecule that strongly binds to the nanocrystal’s surface, essentially acting like a ‘dam’ to hold back the energy stored in the charge-separated state formed after light absorption. This technique extends the lifetime of the charge separation to the longest recorded for these materials, providing a pathway to improved efficiencies and more opportunities to put this energy to work in chemical reactions. This collaboration is part of the U.S. Department of Energy funded Energy Frontier Research Center: Ensembles of Photosynthetic Nanoreactors (EPN).

Harnessing Light to Power Chemistry

Many of the products we rely on today, from plastics, to fertilizers, and pharmaceuticals, are created, or synthesized, through industrial chemical reactions that can often require immense heat and pressure, typically generated by burning fossil fuels. For decades there has been research exploring a less harsh and theoretically more efficient alternative: Photocatalysis. The goal is to use a compound, a “photocatalyst”, that can harness the energy in light and use it to power chemical reactions at room temperature. Semiconductor nanocrystals, particles that are over a thousand times smaller than the width of a human hair, are a leading candidate for this job. When exposed to light these nanocrystals generate a short-lived spark of energy, in the form of a separated negative charge (an electron) and a positive charge (called a “hole”, due to the absence of an electron). A key challenge in this area is that this spark disappears quickly, because the electron and the hole recombine, and the energy is lost before it can be put to good use.

Building a Molecular Dam

To solve this problem the team focused on building what we might call a ‘molecular dam’, something that helps prevent, or at least slow down, the electron and the hole from recombining. This research started with cadmium sulfide (CdS) nanocrystals and designed a molecule (in this case a phenothiazine derivative) with two key features; first the incorporation of a chemical group that acts as a ‘sticky anchor’ (in this case a carboxylate group), which binds strongly to the nanocrystal surface, and second, a molecular structure that quickly accepts the positive charge (the hole), from the nanocrystal to realize the light-driven charge separation event.

By anchoring this molecule to the surface of the nanocrystal the team created a highly efficient and stable pathway. As soon as exposure to light creates the electron-hole pair in the nanocrystal, the anchored molecule shuttles the hole away, physically separating it from the electron. This physical separation of the electron and the hole prevents the two from quickly snapping back together and wasting the energy. This results in a charge-separated state that lasts for microseconds, which is an eternity in the world of photochemistry, creating a much larger window of time for future researchers to work with in terms of harnessing this captured light-driven energy for useful chemical reactions. The team was able to prove the significance of the ‘sticky anchor’ carboxylate, by comparing their derivative to a phenothiazine that lacked the anchor, which was shown to be far less effective at holding the energy, demonstrating that this anchoring to the surface was key to this system’s performance.

This collaborative work was done as part of the U.S. Department of Energy funded Energy Frontier Research Center (EFRC) Ensembles of Photosynthetic Nanoreactors (EPN). EPN consists of 17 senior investigates located across 9 universities and 3 U.S. national laboratories. The goal of EPN is to provide a forum for collaboration, bringing together expertise to advance the frontiers of discovery and fundamental knowledge in photochemical energy conversion. The aim is to not only foster new discoveries and applications, but in doing so, train the researchers who will build knowledge and advances that will benefit the United States innovation and economy.

This project took advantage of the different areas of expertise of each team to generate ideas and quickly execute them. Kenny Miller’s group of dedicated undergraduate researchers at Fort Lewis College synthesized the carboxylated phenothiazine derivative (and a slew of others). Miller then sent the derivative to Jenny Yang’s group of inorganic electrochemists at UC Irvine for advanced electrochemical characterization. Gordana Dukovic’s group here at �� synthesized the nanocrystals, tested their compatibility with the derivative, characterized the binding, and undertook the advanced laser spectroscopy study to see how the electrons and holes behaved.

“The first time I saw the results-saw how effective our ‘molecular dam’ was at slowing charge recombination-I knew we had struck gold” explained Dr. Sophia Click, a lead author on the study. “To slow charge recombination from nanoseconds to microseconds, and with a molecule that can be paired with so many existing photocatalyst systems, makes this work vital to share with as many researchers as possible.”

Development of this ‘molecular dam’ could have implications for the future design of catalysts for light-driven chemistry. By increasing the efficiency of the initial energy-capture step, this system improves the efficiency of the entire process. This could improve not just one specific reaction, but rather, benefit a broad range of light-driven chemical reactions. A key technology this could enhance is the development of light-driven creation of chemical commodities or high-value chemicals. This research provides a more robust and versatile chemical toolkit for exploring these possibilities.

This discovery in controlling charge-separation, and energy, at the nanoscale is an important design parameter into developing light-driven chemistry, and hopefully light-driven chemical manufacturing. Imagine a future where materials, such as plastics, and even pharmaceuticals, are not made in energy inefficient high-temperature reactors powered by fossil fuels but instead are synthesized directly and efficiently using the power of light. While this vision is still on the horizon, the work done in this collaboration provides an important piece of the scientific puzzle, constituting a huge leap toward one day achieving these goals.

The study, “Exceptionally Long-Lived Charge Separated States in CdS Nanocrystals with a Covalently Bound Phenothiazine Derivative” was published in the journal Chem. This work was supported by the U.S. Department of Energy, Office of Science, as part of the Energy Frontier Research Center: Ensembles of Photosynthetic Nanoreactors (EPN; DE-SC0023431), with additional experiments on nanorods supported by Air Force Office of Scientific Research under AFOSR (FA9550-22-1-0347).

October 2025

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Pre-steady-state kinetics of nanocrystal:molybdenum nitrogenase biohybrids reveals hole-scavenging efficiency is critical to N2 reduction

Daniel Morton — Wed, 30 Jul 2025 19:59:40 +0000

Pre-steady-state kinetics of nanocrystal:molybdenum nitrogenase biohybrids reveals hole-scavenging efficiency is critical to N2 reduction Daniel Morton Wed, 07/30/2025 - 13:59

CELL REPORTS PHYSICAL SCIENCE, 2025, 102732

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Understanding light-driven production of hydrogen could unlock future insights for harnessing light for chemistry

Daniel Morton — Mon, 09 Jun 2025 16:27:04 +0000

Understanding light-driven production of hydrogen could unlock future insights for harnessing light for chemistry Daniel Morton Mon, 06/09/2025 - 10:27

Daniel Morton

Light to fuel: clean hydrogen production. Improved understanding of the light-driven production of hydrogen holds the promise not just to make the reaction more efficient in producing a fuel, but also to offer a framework to better understand future light-driven chemistries.

Many chemical reactions require the input of energy to activate the transformation. This can often be in the form of heat, or chemical energy. One of the most efficient ways of introducing energy into a reaction is by using light. If you don’t have to heat up a reaction, or add extra chemicals to it, and instead shine a light on it, you can save significant energy. However, it can be difficult to control and optimize light-driven reactions. This research, just published in Chem, is a collaboration between the Dukovic Group at the �� (��) and the King Group at the National Renewable Energy Lab (NREL) and provides a holistic understanding of the light-driven production of hydrogen gas using a nanocrystal-enzyme complex as the catalyst, and a computational framework that can be used more generally to understand other light-driven chemical reactions in the future. The code for this model is being made available in the supplementary documents of this article.

Chemical catalysis is a special type of reaction, one that increases the speed of a transformation and often reduces the amount of waste produced by the process. Think of it like an assembly line. The catalyst is like a station on the line, bringing together two or more components to create a new product that is then passed along. Without the catalyst the components might, by chance, bump together and form the desired product, but it will be much slower, and much less frequent. The catalyst remains unchanged in the process and can repeat the transformation many times.

Enzymes are Nature’s catalysts. On the cellular level, whenever a change needs to happen, an enzyme is usually involved. The speed of an enzyme, and its selectivity, that is its ability to only react with the desired molecules out of the soup of molecules present in a typical cell, is fantastic. Enzymes are often superior to catalysts we can make in a lab, and as such, much research has gone into finding ways to harness such enzymes to do reactions for us in the lab. Unfortunately, it is not as easy as just grabbing some enzyme out of a cell. Enzymes often require specific environments and partners to react with.

Redox enzymes are a special, and particularly attractive, class of enzymes. They are capable of adding, or removing, an electron from a chemical reaction, a key step in the production of hydrogen gas. Redox enzymes rarely exist by themselves. Returning to the assembly line analogy, to get a station that can add the electrons to the protons (H⁺) to make hydrogen gas, many other stations need to be added before in a specific order. In a cell there is a chain of enzymes that pass the electrons along before the reaction can take place.

This is where the artificial component comes in. The nanocrystal, which, when exposed to light, releases an electron, replaces the long chain of enzymes and can directly transfer an electron to the enzyme. So, you reduce your assembly line down from a chain of many stations to just two. “This work was really only possible through collaboration” explains Gordana Dukovic, the lead researcher at ��. “The team at NREL have vast expertise in hydrogenase (the redox enzyme that creates hydrogen gas), and we have the expertise in making and tailoring the nanocrystals and studying what they do after they absorb light”. Getting the enzyme to work with the artificial electron donor took some work.

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This Research

Characterization of Photochemical Processes

Electron Transfer Kinetics

Competition between electron transfer processes

Activation Thermodynamics

Role of Surface-Capping Ligands

Quantum Efficiency of Charge Transfer

2020 Review of this research area