Scratchproof eyeglasses, crack-resistant paint, fabrics that repel stains — these high-performing materials have all been developed thanks to nanoparticle research.
Yet there’s still so much that nanoparticles and nanomaterials can do for a variety of industries. Three Western Kentucky University professors — Sanju Gupta, Ph.D.; Lawrence Hill, Ph.D.; and Ali Oguz Er, Ph.D. — are in the midst of nanoparticle research that’s poised to have potentially significant impacts on medicine and renewable energy.
Sanju Gupta, Ph.D.: A Less Expensive, More Energy Efficient Way to Filter Water
Gupta’s career as a physicist has spanned more than three decades. Throughout that time, her specific research topics have varied, but she’s typically driven by a particular curiosity.
“I’ve always been drawn to how things work and understanding those mechanisms in greater detail,” she says.
Since joining the WKU faculty in 2013, Gupta has found new ways to tap into her long-running expertise on nanocarbons by focusing on graphene — the single layer of graphite, which is most commonly used in pencil lead.
“When you write with a pencil, you leave thousands of graphene layers on the piece of paper,” Gupta says. “Graphite is basically nothing but a numerous graphene sheets put together in a layered fashion. I’ve been obsessed with graphene since I came to WKU and I’ve used graphene as a platform at the grand challenges of alternative energy-water-sensing nexus research.”
As an example, Gupta’s current research projects include using graphene to create engineered electrodes for energy conversion, storage and harvesting and for scalable membranes used for water detoxification. When graphene is combined with oxygen, it creates water-processable graphene oxide. Not only is this a more cost-effective way to filter water, but it’s also environmentally friendly because there are no chemicals involved in the membranes’ fabrication process. The research results are so promising that Gupta has already fielded calls from interested companies who want to explore commercial applications of this process.
Gupta is also examining several other graphene oxide-based water filtration techniques. Graphene oxide boasts more strength than other membranes currently used in industrial water filtration, and Gupta combined graphene with polymers to make it even stronger. In fact, one of Gupta’s research students recently presented on this particular study and also took home first place in a Kentucky Academy of Science research competition.
In addition to water filtration, Gupta’s research also focuses on capacitive desalination, or removing the salt ions from water using nanoionics. Here, Gupta uses graphene and carbon nanotube to make mesoporous electrodes, or aerogels.
“Imagine if you take a tiny strand of these graphene sheets and put them together so they make an topologically interconnected network, just like neurons,” she says. “As a result, there’s a lot of open space — air pockets. We call those mesoporous architectures/structures ‘aerogels.’”
The benefit of that type of open structure is that it exposes more surface area, which also increases the salt intake capacity, enabling you to desalinate a larger amount of water without requiring more materials. This summer, Gupta plans to research the bio-inspired membranes by use of biological molecules with graphene oxide to filter water selectively while also separately retaining the water’s organic pollutants and bacteria.
No matter the research project, it’s a given that Gupta will be working side-by-side with a range of students, including those from WKU physics, chemistry and engineering majors and Gatton Academy. These student interactions are as important to Gupta as the research itself.
“I love mentoring — it’s like (scientific) coaching for me,” she says. “It’s my duty as a professor to help educate future generations.”
While working with Gupta, students learn a variety of state-of-the-art instruments, analytical thinking and skillsets that are applicable to almost any career path, STEM or otherwise.
“It’s not about knowing all of the technical terms — it’s about the journey and getting involved in intellectual endeavors,” she says. “I can take these examples of sciences, what’s happening and how it’s applicable to what you’re learning in the classroom. When they do the research in the lab, they clearly see the correlation and the concept becomes ingrained. They will never forget, even if they don’t continue to work in the same field. It’s lifelong learning.”
Lawrence Hill, Ph.D.: Improving the Performance of Nanoparticles
There’s so much activity that happens at the nanoparticle level. And given their microscopic size, that can be difficult to imagine!
Hill suggests thinking of a gold brick, which has a certain density and electronic properties. “When you get smaller, that’s no longer true. It starts mattering how many atoms of gold you have and how many layers of gold. There’s a transition from a single atom of gold to a bulk material of gold that we can hold in our hands.”
Hill has a background in organic and materials chemistry and is focused on both nanoparticles and organic polymers. Some of Hill’s research is similar to Gupta’s in that it examines nanoparticle-based applications to help generate renewable energy.
Nanoparticles provide an ideal research focus because their small size has big potential.
“That small size gets you more surface area per unit volume, which results in cost efficiency,” Hill says. “The more surface area you can get, the more active surface area you have and the less money you spend.”
If you can produce nanoparticles and control their electronic properties, they can then be used as catalysts. The nanoparticle surface reacts with a substrate and a reaction occurs. Modern, multi-component materials can present more challenges because of a higher likelihood of a bulk or aggregate that forms and clogs the surface area. You can use organic molecules to keep the particles from sticking together, but you’ll then have a decreased surface area. Part of Hill’s research includes identifying alternative ways to synthesize nanoparticles without ligands (an atom or molecule attached to a central atom).
And he’s well on his way. Hill recently published a study showing that two nanoparticles were connected using ionic liquids instead of ligands.
“They stabilize the particles without binding strongly to them,” he says. “Our next step is to synthesize a semiconductor particle that’s capable of harvesting light using only ionic liquids.”
Hill describes his research as “more fundamental than applied,” so many of his studies are designed to focus on a particular approach and whether it can improve the activity of nanoparticles.
“The actual nanoparticle we’re investigating at any one time may or may not be the best particle to split water, but can we come up with an approach to any nanomaterial to improve its performance?” he says.
Because the research is often focused on nanoparticle performance, the studies don’t typically take very long, Hill says. Instead, the focus is often on synthesizing the particles, purifying them and then identifying the result.
“It’s making it, then figuring out what you made that takes awhile,” he says.
Like Gupta, Hill often works with students on his research projects. For example, Hill is currently working with a master’s student who is essentially independent in the lab. Another master’s student completed his thesis on the recently published research study on particles and ionic liquids and has since transitioned to full-time employment with a leading manufacturer of sealants, adhesives and polyurethane foams.
Hill also works with undergraduate and Gatton Academy students. In fact, two Gatton Academy students were co-authors on the recently published paper. Hill says watching these high school students work in the lab has been nothing short of impressive.
“I’m working with one Gatton student who’s doing amazing things in the lab,” he says. “She’s not yet 17!”
Ali Oguz Er, Ph.D.: Better Health and Energy Outcomes with Nanoparticles
In Er’s on-campus lab, powerful lasers are at work to help produce tangible results that guide the creation of new procedures and processes.
“The amount of power in one laser pulse is enough to power Bowling Green,” he says.
Yet the power generated by nanosecond and picosecond lasers decays in a short amount of time, so it’s much better suited to producing nanoparticles from various materials rather than power generation.
Once the nanoparticles are produced (and also characterized using WKU’s Large Chamber Scanning Electron Microscope), a variety of applications can be explored. For example, Er is working on a collaborative research study with the University of Kentucky Medical School that uses laser-produced nanoparticles to kill bacteria in human blood. In surgical procedures like knee, hip and joint replacements, infections can occur that sometimes require additional surgical repair. There’s quite a bit of work remaining until this procedure would be available in the hospital, but progress is happening.
“The research can go really fast, but getting permission to try on humans takes some time,” Er says.
Since Er’s collaborator is a medical doctor, they’ll be able at some point to test the nanoparticle procedure on blood that’s extracted from a patient. Then, if the expected results occur, further testing will continue.
Another of Er’s research studies is especially relevant to WKU’s home state and its role as one of the nation’s biggest coal producers. Using laser-generated nanoparticles in an ultra-high vacuum chamber, hydrogen can be produced from coal without requiring large power plants. The research has been so successful that a patent has been secured and companies are starting to inquire about the process, especially given the increased attention on hydrogen production.
“Right now, the Department of Energy has prioritized hydrogen production — this is the future,” Er says. “You want to diversify your portfolio because even if you don’t run out of fossil fuels, it’s not hard to stay clean. When you burn hydrogen, you just get water — nothing else.”
Like Gupta and Hill, Er works with a variety of students, including WKU graduate and undergraduate students, as well as Gatton Academy students. Due to the expansive nature of Er’s projects, he usually works with students from a variety of departments, including physics, pre-med, biology and chemical engineering. Er shares a similar view of student work as Gupta: the skills learned in the lab are beneficial no matter what career path or course of study a student pursues.
“Two of my biology students have been admitted to medical school and one of my mechanical engineering students is going to pursue her Ph.D.,” he says. “I believe the experiments and the experience they got from our lob helped them a lot.”
Er equates the students’ research experience with a common skill: driving a car.
“Once you know how to drive a car, you can drive a minivan,” he says. “Maybe you can’t drive a large truck at first, but you have the basics, so after practice, you can also drive the truck. Working in the lab is similar. Once you know how to operate the microscopes and lasers, you get the information to run the experiment, then you know what the experiments need. These are important skills to retain.”