From The DOE’s Lawrence Berkeley National Laboratory: “The Donnan Potential – Revealed at Last”
From The DOE’s Lawrence Berkeley National Laboratory
12.19.22
Stephen Ornes
First-ever direct measurement of the electric potential at the liquid-membrane interface could push new research in energy, biology, and materials science
Staff scientist Ethan Crumlin at Berkeley Lab’s Advanced Light Source [below]. (Credit: Marilyn Sargent/Berkeley Lab)
The Donnan electric potential arises from an imbalance of charges at the interface of a charged membrane and a liquid, and for more than a century it has stubbornly eluded direct measurement. Many researchers have even written off such a measurement as impossible.
But that era, at last, has ended. With a tool that’s conventionally used to probe the chemical composition of materials, scientists at the Department of Energy’s Lawrence Berkeley National Laboratory recently led the first direct measurement of the Donnan potential.
Ethan Crumlin and his collaborators recently reported the measurement in Nature Communications [below].
Such a measurement could yield new insights in many areas that focus on membranes. The Donnan potential plays a critical role in transporting ions through a cellular membrane, for example, which ties it to biological functions ranging from muscle contractions to neural signaling. Ion exchange membranes are also important in energy storage strategies and water purification technologies.
“Knowing the Donnan potential is relevant to many applications, from energy to biology, to water treatment,” said Pinar Aydogan-Gokturk, an early career scientist and postdoctoral scholar at Berkeley Lab who performed the measurements.
Aydogan-Gokturk said the new measurement will also improve previous thermodynamic models of the Donnan equilibrium. Those models have long relied on uncertain assumptions and indirect measurements. “Using our method, we are hoping to be able to answer questions about fluid dynamics in non-ideal conditions at the membrane interfaces,” she said.
Staff Scientist Ethan Crumlin (left) and staff scientist Jin QIan (right) with postdoc Pinar Aydogan Gokturk on Zoom at Berkeley Lab’s Advanced Light Source. (Credit: Marilyn Sargent/Berkeley Lab)
Frederick Donnan-a British-Irish chemist-first probed the phenomenon in the early 20th century using a solution of Congo red, a dye that’s now known to be toxic and carcinogenic to many organisms. In a paper published in 1911 [Chemical Reviews (below)], Donnan described experiments in which a membrane separated two charged solutions and only allowed some ions to pass through. As the two solutions reach equilibrium, he found, they may also scatter charges unevenly across the membrane — and therefore produced an electric potential.
The Donnan potential plays a role in any system that brings together a material with fixed ions — like a charged polymer or the membrane of a cell — and an electrolyte solution. The charges in the solution are free to move, and some can pass into the membrane.
To make the measurement, Aydogan-Gokturk, Crumlin, and their collaborators at the University of Texas-Austin’s Center for Materials for Water and Energy Systems used a technique called “tender” ambient pressure x-ray photoelectron spectroscopy, or tender-APXPS.
It’s a sophisticated application of x-ray photoelectron spectroscopy, or XPS, which can reveal the chemical composition, and lesser known (but just as important) local potentials of the surface of a material. When x-rays are focused on the materials’ surface, they trigger the release of electrons, and the energy levels of those electrons give away the constituent atoms. In 1981, Swedish physicist Kai Siegbahn won the Nobel Prize in Physics for work on using XPS.
Surface spectroscopy tools like XPS typically require vacuum environments to work, but pioneering work at Berkeley Lab led to the use of XPS at ambient pressure. About 10 years ago, ALS scientists pushed the technology further, combining ambient pressure XPS with higher-energy x-rays. That advance allowed them to probe solid-liquid interfaces.
(Credit: Marilyn Sargent/Berkeley Lab)
“Until recently, Berkeley Lab’s ALS was the only place in the world where you could do this with a solid-liquid interface,” said Crumlin.
During the pandemic, Crumlin, Aydogan-Gokturk, and their team collected time intensive spectroscopic data sets to probe the Donnan potential. They immersed a charged membrane in a salt solution, fired x-rays at the interface, and studied the electrons that emerged. To help validate the experiments, Berkeley Lab Staff Scientist Jin Qian compared the measured Donnan potential values to simulated thermodynamic models. A tool that’s usually used to probe chemical composition may not seem like an obvious instrument for studying membranes, but Crumlin predicted that using tender-APXPS in membrane science will continue to reveal new insights about interfacial phenomena.
“The membrane community is a totally new world to this space of science,” he said. “This work really combines two worlds together.”
Science paper:
Nature Communications
See the science paper for instructive material with images.
Chemical Reviews
See the science paper for instructive material with mathematical expressions.
See the full article here .
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In the world of science, The Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the The National Academy of Sciences, one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the The National Academy of Engineering, and three of our scientists have been elected into The Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.
Berkeley Lab is a member of the national laboratory system supported by The DOE through its Office of Science. It is managed by the University of California and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above The University of California-Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.
Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a University of California-Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.
History
1931–1941
The laboratory was founded on August 26, 1931, by Ernest Lawrence, as the Radiation Laboratory of the University of California-Berkeley, associated with the Physics Department. It centered physics research around his new instrument, the cyclotron, a type of particle accelerator for which he was awarded the Nobel Prize in Physics in 1939.
LBNL 88 inch cyclotron.
Throughout the 1930s, Lawrence pushed to create larger and larger machines for physics research, courting private philanthropists for funding. He was the first to develop a large team to build big projects to make discoveries in basic research. Eventually these machines grew too large to be held on the university grounds, and in 1940 the lab moved to its current site atop the hill above campus. Part of the team put together during this period includes two other young scientists who went on to establish large laboratories; J. Robert Oppenheimer founded The DOE’s Los Alamos Laboratory, and Robert Wilson founded The DOE’s Fermi National Accelerator Laboratory.
1942–1950
Leslie Groves visited Lawrence’s Radiation Laboratory in late 1942 as he was organizing the Manhattan Project, meeting J. Robert Oppenheimer for the first time. Oppenheimer was tasked with organizing the nuclear bomb development effort and founded today’s Los Alamos National Laboratory to help keep the work secret. At the RadLab, Lawrence and his colleagues developed the technique of electromagnetic enrichment of uranium using their experience with cyclotrons. The “calutrons” (named after the University) became the basic unit of the massive Y-12 facility in Oak Ridge, Tennessee. Lawrence’s lab helped contribute to what have been judged to be the three most valuable technology developments of the war (the atomic bomb, proximity fuse, and radar). The cyclotron, whose construction was stalled during the war, was finished in November 1946. The Manhattan Project shut down two months later.
1951–2018
After the war, the Radiation Laboratory became one of the first laboratories to be incorporated into the Atomic Energy Commission (AEC) (now The Department of Energy . The most highly classified work remained at Los Alamos, but the RadLab remained involved. Edward Teller suggested setting up a second lab similar to Los Alamos to compete with their designs. This led to the creation of an offshoot of the RadLab (now The DOE’s Lawrence Livermore National Laboratory) in 1952. Some of the RadLab’s work was transferred to the new lab, but some classified research continued at Berkeley Lab until the 1970s, when it became a laboratory dedicated only to unclassified scientific research.
Shortly after the death of Lawrence in August 1958, the UC Radiation Laboratory (both branches) was renamed the Lawrence Radiation Laboratory. The Berkeley location became the Lawrence Berkeley Laboratory in 1971, although many continued to call it the RadLab. Gradually, another shortened form came into common usage, LBNL. Its formal name was amended to Ernest Orlando Lawrence Berkeley National Laboratory in 1995, when “National” was added to the names of all DOE labs. “Ernest Orlando” was later dropped to shorten the name. Today, the lab is commonly referred to as “Berkeley Lab”.
The Alvarez Physics Memos are a set of informal working papers of the large group of physicists, engineers, computer programmers, and technicians led by Luis W. Alvarez from the early 1950s until his death in 1988. Over 1700 memos are available on-line, hosted by the Laboratory.
The lab remains owned by the Department of Energy , with management from the University of California. Companies such as Intel were funding the lab’s research into computing chips.
Science mission
From the 1950s through the present, Berkeley Lab has maintained its status as a major international center for physics research, and has also diversified its research program into almost every realm of scientific investigation. Its mission is to solve the most pressing and profound scientific problems facing humanity, conduct basic research for a secure energy future, understand living systems to improve the environment, health, and energy supply, understand matter and energy in the universe, build and safely operate leading scientific facilities for the nation, and train the next generation of scientists and engineers.
The Laboratory’s 20 scientific divisions are organized within six areas of research: Computing Sciences; Physical Sciences; Earth and Environmental Sciences; Biosciences; Energy Sciences; and Energy Technologies. Berkeley Lab has six main science thrusts: advancing integrated fundamental energy science; integrative biological and environmental system science; advanced computing for science impact; discovering the fundamental properties of matter and energy; accelerators for the future; and developing energy technology innovations for a sustainable future. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab tradition that continues today.
Berkeley Lab operates five major National User Facilities for the DOE Office of Science:
The Advanced Light Source (ALS) is a synchrotron light source with 41 beam lines providing ultraviolet, soft x-ray, and hard x-ray light to scientific experiments.
The DOE’s Lawrence Berkeley National Laboratory Advanced Light Source.
The ALS is one of the world’s brightest sources of soft x-rays, which are used to characterize the electronic structure of matter and to reveal microscopic structures with elemental and chemical specificity. About 2,500 scientist-users carry out research at ALS every year. Berkeley Lab is proposing an upgrade of ALS which would increase the coherent flux of soft x-rays by two-three orders of magnitude.
Berkeley Lab Laser Accelerator (BELLA) Center
The DOE Joint Genome Institute supports genomic research in support of the DOE missions in alternative energy, global carbon cycling, and environmental management. The JGI’s partner laboratories are Berkeley Lab, DOE’s Lawrence Livermore National Laboratory, DOE’s Oak Ridge National Laboratory (ORNL), DOE’s Pacific Northwest National Laboratory (PNNL), and the HudsonAlpha Institute for Biotechnology . The JGI’s central role is the development of a diversity of large-scale experimental and computational capabilities to link sequence to biological insights relevant to energy and environmental research. Approximately 1,200 scientist-users take advantage of JGI’s capabilities for their research every year.
The LBNL Molecular Foundry is a multidisciplinary nanoscience research facility. Its seven research facilities focus on Imaging and Manipulation of Nanostructures; Nanofabrication; Theory of Nanostructured Materials; Inorganic Nanostructures; Biological Nanostructures; Organic and Macromolecular Synthesis; and Electron Microscopy. Approximately 700 scientist-users make use of these facilities in their research every year.
The DOE’s NERSC National Energy Research Scientific Computing Center is the scientific computing facility that provides large-scale computing for the DOE’s unclassified research programs. Its current systems provide over 3 billion computational hours annually. NERSC supports 6,000 scientific users from universities, national laboratories, and industry.
DOE’s NERSC National Energy Research Scientific Computing Center at Lawrence Berkeley National Laboratory.
Cray Cori II supercomputer at National Energy Research Scientific Computing Center at DOE’s Lawrence Berkeley National Laboratory, named after Gerty Cori, the first American woman to win a Nobel Prize in science.
NERSC Hopper Cray XE6 supercomputer.
NERSC Cray XC30 Edison supercomputer.
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NERSC PDSF computer cluster in 2003.
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Cray Shasta Perlmutter SC18 AMD Epyc Nvidia pre-exascale supercomputer.
NERSC is a DOE Office of Science User Facility.
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Berkeley Lab has a major role in two DOE Energy Innovation Hubs. The mission of the Joint Center for Artificial Photosynthesis (JCAP) is to find a cost-effective method to produce fuels using only sunlight, water, and carbon dioxide. The lead institution for JCAP is the California Institute of Technology and Berkeley Lab is the second institutional center. The mission of the Joint Center for Energy Storage Research (JCESR) is to create next-generation battery technologies that will transform transportation and the electricity grid. DOE’s Argonne National Laboratory leads JCESR and Berkeley Lab is a major partner.
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