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A Q&A with Alenka Luzar on what’s so special about water

As far back as she can remember, Alenka Luzar, Ph.D., has loved water.

Growing up in Slovenia, she started skiing at age 4, and in her teens became an accomplished alpine skier and participated in the junior Winter Olympics in Grenoble, France.

Of course, snow was just water in another form. Luzar recalls wanting to go down the hill as fast as possible, so she turned to science to search for the answers. She said the experience launched her interest in super-low friction surfaces to reduce water adhesion.

Luzar would turn her love for water, and ultimately for math and science, into a career in chemistry.  

Luzar, professor of physical chemistry in the Virginia Commonwealth University College of Humanities and Sciences, and her team have made pioneering contributions to the fundamental theory of aqueous interfaces, dynamics of hydrogen bonds in condensed phase systems, phase behavior of confined water and dynamics of aqueous self-assembly.

According to Luzar, understanding the changes in liquid dynamics and structure due to interactions with confining surfaces has far-reaching implications for fundamental science, as well as technological applications through molecular engineering. Examples include biological self-assembly, the design of self-cleaning surfaces and molecular development of lab-on-a-chip technologies.

This summer, during the Gordon Research Conference on Water and Aqueous Solutions, Luzar was elected to serve as the vice chair of the 2016 meeting and chair of the 2018 meeting. This is an exceptional recognition, as the Gordon Research Conferences are traditionally the world’s premier scientific meetings, where leading scientists from around the world meet to discuss their latest unpublished work and future challenges in a unique, informal and interactive format.

Luzar, who joined VCU in 2004, recently discussed her research, her goals and her dedication to passing on scientific knowledge to the next generation.

What is your area of research?

We study complex chemical systems, specifically condensed matter. These are systems where interactions between molecules play a central role and quantifying these interactions is essential. The methods are built on statistical mechanics, a probability theory that explains the macroscopic or bulk properties of materials by describing the microscopic forces at work on individual atoms or molecules.

We focus on the dynamics and structure of molecular liquids, in particular interfacial and confined water, hydrogen-bonded mixtures and the nature of hydrophobic interactions. These interactions determine the relationship between water molecules and solute species that lack polar sites with which to form hydrogen bonds.

Hydrophobic/water interfaces surround us. They are important in things as diverse as keeping us dry on a rainy day, or to understand the folding of proteins.

As computational chemists, instead of “wet” chemistry, we use computational tools to interpret experiments, to understand chemical systems at the atomic scale, and make predictions that guide future experiments. Our tools range from pencil and paper calculations to supercomputers where we perform “in silico” experiments and can simulate real life movements of complex systems, consisting of a huge number (tens of thousands) of atoms and molecules. Rarely the existing theoretical tools and software packages are sufficient for these studies. More often, we need to develop new conceptual frameworks and algorithms to tackle really challenging problems.

What drew you to study this field?

For me, theory and computational modeling and physical chemistry have all the components I’ve always had passion for: math and science, and to discover or understand a phenomenon at a fundamental level, zooming in on molecule-to-molecule interactions, and then using this knowledge to enable a new technology or a new drug or a new material. What more can one ask for?

What’s so special about water?

The “molecular sociology” of water, its condensed phase. The essential properties of liquid water reduce to three: a large number of hydrogen bonds, their local tetrahedral symmetry and their short lifetime. Other liquids might have some of those special characteristics, but only water has them all. Might this be enough to make water especially fit for life? The hunt for the correct answer still goes on.

Historically, water fascinated people of many civilizations. It was considered as a simple “element” until the end of the 18th century. Scientific knowledge of water starts in 1780 when Cavendish and Lavoiser discovered that water could be decomposed into two gases, and that, conversely, the combination of these two gases generates water. Since then, apart from numerous experiments, it was molecular modeling, which started in the early 1980s that was influential for the understanding of liquid water, as we know it today.

Water remains an intriguing liquid that continues to excite interest of scientists in many disciplines. No wonder that the most mysterious molecule on Earth (and Mars and the moon and ….) has its own Gordon Research Conference every second year since 1970, and Water and Aqueous Solutions GRC has consistently served as the premier venue for its discussion and viewpoints. And no wonder we follow our basic motto: “water, water everywhere … ” and apply our knowledge to a broad range of basic problems and applications, from biology, to materials by design, to energy storage.

You study hydration processes on the molecular level. What is this and how could this work one day impact the field of materials science?

These processes have impact well beyond materials science alone. Let me give you a few chemical problems that seem to have nothing in common with each other: enzyme catalysis, soil decontamination and electrochemical capacitor performance. But they do have one key ingredient in common. All these examples (and many more) in one way or another involve hydration (if the solvent is water) processes.

To understand these processes we need to understand how water molecules interact with solutes and surfaces in question. We know now that interfacial water (or water near surfaces) is integral to many physical and chemical systems and crucial for biological function. Thus, understanding the basic mechanisms involved in hydration processes in biology and nanotechnology is taking us a step closer to creating new biomimetic materials, harvesting energy from nature and storing energy.

What do you ultimately hope your research will find – what is the goal of your work?

Understanding interfacial water at the molecular and nanoscale level has been an essential goal of my group research, which has been supported by the National Science Foundation, through its Chemistry Division, during the past decade, and continues now.

My group investigates the control of water properties in nanoconfined spaces with applications to nanofluidic devices. The objective is to gain a detailed understanding of hydrophobicity, a molecule’s resistance to wetting; and hydrophilicity, a molecules attraction to water, by focusing on water structure, thermodynamics and motion in confined spaces.  

Ultimately, the work will lead to a unified picture of factors that control interfacial water's thermodynamic and kinetic properties and will enable us to tune surface hydrophobicity on multiple length scales.

Beyond hydrophobicity, our further objective is to explore the influence of nanoscale surface texture and its relation to superhydrophobicity or extreme resistance to wetting. These surfaces show promise for passive drag reduction (super-low friction) and our goal is to tailor wetting properties in a reversible manner, to make smart or responsive surfaces for dynamical tunable devices.

Additional components of my current research program span across materials’ characterization at the nanoscale, the tuning of surface properties with external electric fields, surface ionization, and molecular mechanisms involved in electrical and surface energy storage currently funded by the Department of Energy through the Office of Basic Science. In this program, our goal is to develop molecular level understanding of energetics, kinetics and hydration of nanoparticle dispersions in ionic solutions, and to introduce novel separation techniques. Through molecular modeling studies, we are learning how to design new media for surface energy storage, tune nanomaterial’s wetting properties permanently (by ionic functionalization) or transiently (by applied fields), and how to sequester ions or drive water against concentration gradient.

You brought the Faraday Discussion FD146 to VCU in 2010; what do opportunities such as this offer students and faculty alike?

Bringing the most prestigious international meeting in physical chemistry for the first time to the U.S. offered a lifetime opportunity for VCU students and their faculty.

What made FD146 unique was the Inaugural Faraday Discussion Graduate Research Seminar that preceded it. It was the very first of its kind and was designed to prepare students for actual Faraday Discussion. As indicated by the title, a distinct feature of Faraday Discussion is much greater emphasis on discussion of papers and subsequent publications of all questions, comments and responses. The pre-meeting gave students a lot of encouragement and confidence to stand up and ask many relevant questions at the FD146.

Do you know that 30 percent of questions in the printed Faraday Discussion volume book comes from students? What this means is that their active participation is recorded forever in their first (for most of them) publication on par with the most eminent scientists in the field. Many of these students have now moved to independent positions in academia and industry. An opportunity such as this one is a model for how science can be passed on to the next generation.

What advice do you have for young people interested in research in chemistry?

If they like to solve intellectual and practical problems on a daily level, have curiosity and like to wonder about how things work and why, my advice would be to go for it. To pursue their dream, To choose research problems they have passion for. To choose hard problems, working on the idea that where there is difficulty there must be treasure. To trust there is always a better way (in solving a problem), to challenge conventional wisdom. To be willing to expand their horizons beyond chemistry. It is a lifelong learning experience, and this is a wonderful time to be a scientist and to be able to contribute to the well-being of our society.

There are so many exciting research problems out there waiting to be solved. There is a famous scene from the 1960s movie “The Graduate” in which a family friend tells Dustin Hoffman that the future is in “plastics.” Advice today might very well be “nanoscience and nanotechnology,” where chemistry yet again plays one of the leading roles. And because of experimental limitations, molecular modeling has become an important characterization tool in nanotechnology and will continue to do so in the future. Imagine how low-cost clean water (via better filters) and abundant energy (via better solar cells) could free millions around the world from shortages of clean water and electricity, and play a role in diminishing the impact of climate change.

Where do you see your research field headed?

Theoretical and computational chemistry will continue to play a critical role in modern chemistry. The importance of the field (molecular modeling) has been recognized by the 2013 Nobel Prize, awarded to three US scientists — Karplus, Levitt and Warshel. It is a great feeling to see your colleagues and your own professional working field win a Nobel Prize and it really tells you how pervasive calculations and modeling have become in solving all kinds of chemical problems.

One of the important directions in the future will be to further develop multiscale methods for exploring complex systems at multiple length and time scales. The world at the level of molecules is a dynamical one. It will be very important to successfully model non-equilibrium (dynamic) systems.

Molecular modeling will continue to be particularly useful for determination of properties that are still inaccessible experimentally and for the interpretation of experimental data. Together, experiment and theory can make a difference. Theories can provide clues that experiments must confirm, and experiments discover findings that require new theories to explain them. Let me give you one example: hydrophobic attraction — one of the key forces in molecular biology. We still don’t understand its physical origin. We (theorists) think we nailed it down, building theories based on experimental data, then new experiments come out that contradict the previous ones, and we need to think harder. This is what's so exciting about doing theory and calculations, to be able to interpret experiments at a molecular level and to make predictions that guide future experiments.

 

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Alenka Luzar, Ph.D.
Alenka Luzar, Ph.D.