Postdoc Spotlight: Wan Si Tang Creates Nanocarbon Threads in Search for Clean Energy
Humans use a lot of energy, but increasingly it seems that that energy may come at the expense of our planet. While our world looms on the precipice of global climate change, some scientists, like Postdoctoral Fellow Wan Si Tang, are looking for and actively creating new materials to support sustainable and efficient energy use.
In this Postdoc Spotlight, Wan Si Tang discusses the importance of renewable energy technologies and her recent research to more efficiently create new, optically-tunable carbon nanothreads that may change the way future photovoltaic panels are made. Plus, she shares some of her favorite hobbies, advice for future scientists, and what her plans are for her future after her tenure with Carnegie Science.
Interviewed by Katy Cain. Edited for clarity.
First off, can you introduce yourself and your field of study?
Hi, I’m Wan Si and currently a Postdoctoral Fellow at EPL. My background is in experimental materials science. I have been at BBR for almost 3 years working with Tim Strobel.
What is your area of research, and why would you say is it important?
My research focus is on applied materials science; I have experience with materials for energy storage and conversion, relating to hydrogen storage, batteries, and solar cells. Mainly, I have worked on several complex hydride systems for reversible hydrogen storage, silicon-based anodes for lithium-ion batteries, novel solid electrolytes for all-solid-state batteries, and photocatalysts for solar cells.
Personally, it is essential for me to know that my science is relatable to everyday life – everyone has a cellphone and associated battery problems! That makes an easy elevator pitch. It is also imperative, from a practical standpoint, for researchers to find new materials useful for renewable green energy and move away from fossil fuel dependence.
What are the larger implications of your work?
Energy is one of the “Top Ten Problems of Humanity for Next 50 Years”, as pointed out by Professor Smalley, who won the 1996 Chemistry Nobel Prize. In addition, the 2019 Chemistry Nobel Prize was awarded “for the development of lithium-ion batteries”, highlighting the continued importance of developing materials for energy applications. I hope that my small contribution toward alleviating the energy problem will have a positive impact on humankind.
More significantly, moving toward renewable energy technologies will help mitigate climate change through less greenhouse gas emissions and manage the rate of global warming. There is still much work for science to provide solutions.
Can you summarize what you’ve been working on at Carnegie?
My recent work at Carnegie deals with basic science: we are discovering how varying functionalities aid in the synthesis of crystalline nanothreads through accessing the metastable states of hydrocarbon precursors at very high (gigaPascal (GPa)) pressures.
When we say functionality in organic chemistry we are talking about common groups of atoms that influence a molecule’s function and reactivity. You might recognize some common functional groups like hydroxyl (–OH), carboxylic acid (–COOH), and amide (–NH2).
Nanothreads, as the name suggests, are one-dimensional structures with diameters of a few nanometers. These resulting nanothreads have a variety of possible material properties and applications, like exceptional strength and stiffness, tunable electrical properties, and usage for energy storage.
There are currently few examples of crystalline nanothread materials, which are only formed through high-pressure chemistry.
You recently published a couple of papers where you compressed nanothread materials under high pressure to study how their properties changed. What are some new materials or methods that you’ve discovered?
One interesting material is the polymer semiconductor, PDPB (poly(diphenylbutadiyne)), which is used as a photocatalyst in solar cells. PDPB is a polymer, which is basically a long chain of individual DPB (1,4-diphenyl-1,3-butadiyne) molecules. These individual molecules are called monomers.
At Carnegie, our team was able to incrementally compress the starting DPB monomer, forcing the molecules to react and form very-well-ordered PDPB. The specific molecular arrangement of solid DPB allows for this topochemical reaction to occur readily and synthesize a crystalline, organic semiconductor.
As the chain of DPB grew into PDPB under pressure, the optical properties were simultaneously shifted to produce lower energy light at higher wavelengths, which is indicative of an optically-tunable bandgap. This adjustable property is important for the material to function as a photocatalyst. The coolest thing about using pressure to fabricate PDPB is that, once quenched and depressurized, the material retains its optical properties!
This high-pressure assembly route allows for precise reaction control, and improves upon the traditional way of forming PDPB, which is through a light-activated, wet chemistry route. All of this makes our method more desirable in real-world applications.
We also observed new crystalline nanothread phases through the compression of other benzene-based organic solids with various functionalities. In these solids, the particular arrangement of the benzene backbone within the starting monomer molecules is vital for pressure-induced chemistry. We determined the two main indicators for nanothreads to form under pressure are 1) the centroid distance between monomer molecules and 2) their relative slippage angles with respect to each other. When taken into account, these two factors allowed us to determine a monomer’s reaction potential from its crystal structure alone.
Applying our model through the mining of crystallographic databases, we may be able to better predict and find other similarly known monomers with differing functional groups, for access to a wider range of possible nanothread materials.
What inspired you to choose to study materials under pressure?
Pardon my ignorance, but before coming to Carnegie, the diamond anvil cell (DAC) technique to generate high-pressures had not crossed my research path! However, after starting my tenure at the Broad Branch Road campus, I came to understand and respect this meticulous technique, which trains and tests patience and motor skills—both proficiencies particularly relevant to any researcher. Overcoming this challenging field of study has helped make me a more adept scientist.
How has your background influenced your research?
Throughout my scientific career, I have been blessed with good advisors, who have been supportive of my professional trajectory. Without such strong role models, I would not be able to continue down this path. It came full circle when I was invited for an oral presentation at the 2017 Hydrogen-Metal Systems Gordon Research Conference. There, I was reunited with my undergraduate project supervisor, Dr. Ping Chen, who introduced and guided my novice research foray many years ago. It was a bittersweet moment in my professional journey.
International exposure has also greatly influenced my research. Not just having spent time in Asia, Europe, and North America, but also the interactions with a multitude of international scientists—including the broad range of scientists found here at BBR!
It definitely also helps to have great family support from miles away in Singapore!
What else has influenced your thinking as a scientist?
Curiosity and creativity. These are basic tools for problem-solving: what is the problem and how to solve it. To do science, both are required in order to have a greater understanding of our world.
When you’re not actively researching, what hobbies or activities do you enjoy in your spare time?
I started pole-fitness/dancing about 1.5 years ago and currently, with COVID still raging, I am doing plenty at home since it can be a lone sport. The encouragement from the pole community and friends has been wonderful. I had a virtual showcase in June and some friends from campus showed up online to support; everyone was very positive indeed!
What I love about this sport is that there is always something to learn and improve upon, and it is a personal choice to push your boundaries to better a certain aspect. In fact, tackling pole dancing is like taking on challenges in life, both mentally and physically!
Why did you choose Carnegie’s Earth and Planets Laboratory?
I would turn this around to say that Carnegie has given me this opportunity instead. Tim Strobel—and of course BBR (especially those in Tim’s group)—has been extremely welcoming to an outsider without prior experience in high-pressure science. Particularly to those who have slogged through synchrotron time together, like Gus (Borstad), Matt (Ward), Piotr (Guńka), and Tom (Shiell). The friendliness of everyone on campus (fellow postdocs and permanent staff members) is also a valuable social aspect. These three years have been enjoyable and I will definitely miss the campus, many activities, and its members when I leave.
Most importantly, a big shout-out to those from the Abelson lunch club, who have been extremely inviting and inclusive. (And that includes you, Katy!)
What are you planning to do after your time at EPL?
My career path is toward applicable sciences in the industry setting, so stay tuned! Currently, there is an opportunity at the Battery Innovation Center, a public-private, not-for-profit organization in Indiana, working on battery-related research and development. I am excited to be transitioning to another stage of my life and utilizing my knowledge with practical uses to benefit society.
Do you have any advice for current graduate students?
Broaden your mind. In science, in your professional and personal life, and as a human being in general! Sometimes we are so focused on the minute details that we forget the bigger, more important picture. I am sure 2020 has made us all more level-headed and appreciative.
Also, for incoming postdocs, treasure your time here at Carnegie; it is an experience unlike any other.
Anything else you’d like to add?
Here’s my professional portfolio (https://wansitang.wordpress.com/). Thank you for your questions, Katy!