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Enhanced PDT to Cure Cancer with Fewer Side Effects
(From left: PhD candidate Ilkoo Noh and Professor Yeu-Chun Kim)
A KAIST research team developed near-infrared fluorophores-based photodynamic therapy (PDT) that reduced the downside of existing PDTs.
PDT is a way to cure wounds with lasers instead of drug treatment. When a laser irradiates a targeted site, a photosensitizer (PS) absorbs light energy and then converts oxygen to singlet oxygen or free radicals, leading to programmed cell death. This treatment has been used widely in clinical fields, especially for skin disease because it allows noninvasive treatment.
However, the existing PDTs have limitations for first-line therapy because PDT agents can cause genetic variations when they have low efficiency, hence reducing treatment effects.
The key to enhancing the efficiency of PDTs is how much PS can be concentrated to a wanted site, which laser wavelength the PS is reacted to, and how fast the PS clears organelle after treatment.
Professor Yeu-Chun Kim and his team from the Department of Chemical and Biomolecular Engineering, in collaboration with Professor Ji-Ho Park from the Department of Bio and Brain Engineering, developed a new PS called mitochondria targeting photodynamic therapeutic agent (MitDt) to maximize PDT effects while reducing unwanted side effects.
Mitochondria has emerged as target sites to maximize the effects of PS since they play essential roles in metabolism and have high transmembrane potential.
According to the team, when mitochondria is photodamaged by reactive oxygen species (ROS) generated after laser irradiation, they immediately lose their mitochondrial membrane potential and initiate apoptosis. Therefore, combining the PDT agent with the mitochondrial targeting agent can result in rapid damage to cancer cells, improving therapeutic efficacy and reducing unwanted side effects.
To successfully apply mitochondria-targeting PS, the team developed near-infrared (NIR) region PDT agents, which can be used to treat deep-tissue level cancer due to the permeability of the NIR laser. Light scattering is also decreased, thus obtaining higher therapeutic efficacy.
However, there is a problem of generating singlet oxygen when irradiating with an NIR laser. To address this issue, the team developed a novel PS that combines a functionalized NIR dye and a mitochondria-targeting agent to gain the benefit of rapid organelle clearance after treatment and also remain in cancer mitochondria for a long time, amplifying the amount of ROS to the target sites irradiated by the laser.
To verify the efficacy, the team injected MitDt into tumor-bearing mice. They were irradiated with an NIR laser at 662 nm to induce cancer treatment and their cancer size was reduced up to three-fold.
PhD candidate Ilkoo Noh, who led this research said, “This enhanced photodynamic cancer treatment has the advantage of treating a wanted site without any side effects because this PS stays longer in a mitochondrial cancer cell. We also confirmed that the PS did not cause cytotoxicity.”
Professor Kim added, “This research outcome will reduce the danger of side effects and can be applied for treating various diseases”.
This research was chosen as the cover page of Advanced Science on March 25.
Figure 1. The cover of Advanced Science
Figure 2. a) Chemical structure of MitDt compounds (above) b) mitochondria localization of designed PS (left) and ROS generation after 662nm laser irradiation (right)
2018.07.16 View 7364 -
Mechanism Leading to Cortical Malformation from Brain-Only Mutations Identified
Focal malformations of cortical development (FMCDs) are a heterogeneous group of brain cortical abnormalities. These conditions are the most common causes of medically refractory epilepsy in children and are highly associated with intellectual disability, developmental delay, and autism-spectrum disorders. Despite a broad spectrum of cortical abnormalities in FMCDs, the defective migration of neuronal cells is considered a key pathological hallmark.
A research team led by Professor Jeong Ho Lee in the Graduate School of Medical Science and Engineering at KAIST has recently investigated the molecular mechanism of defective neuronal migration in FMCDs. Their research results were published online in Neuron on June 21, 2018.
The research team previously demonstrated that brain-only mutations in the mechanistic target of rapamycin (MTOR) gene causes focal cortical dysplasia, one major form of FMCDs leading to intractable epilepsy in children. However, the molecular mechanisms by which brain-only mutations in MTOR lead to cortical dyslamination and defective neuronal migration in FMCDs remain unclear.
To study the molecular mechanism of brain cortical dyslamination, the research team utilized patients’ brain tissues and modeled the MTOR mutation-carrying cell and animal models recapitulating the pathogenesis and symptoms of FMCD patients. By performing comprehensive molecular genetic experiments, they found that the formation of primary cilia, one of cellular organelles, was disrupted in MTOR mutation-carrying neurons and demonstrated that this ciliary disruption was a cause of cortical dyslamination in FMCDs.
MTOR mutations prevented degradation of the OFD1 protein, one of the negative regulators of ciliary formation. As a result, the OFD1 protein was abnormally accumulated in MTOR mutation-carrying neurons, causing focal cortical dyslamination. By suppressing the expression of the OFD1 protein, the research team was able to rescue the defective formation of primary cilia, leading to the restoration of cortical dyslamination and defective neuronal migration considerably.
Based on these results, the research team is carrying out further research to develop novel therapeutics for patients with FMCDs caused by brain-only mutations.
This work was supported by grants from the Suh Kyungbae Foundation and Citizens United for Research in Epilepsy.
The research paper is titled “Brain Somatic Mutations in MTOR Disrupt Neuronal Ciliogenesis, Leading to Focal Cortical Dyslamination.” (Digital Object Identifier #: 10.1016/j.neuron.2018.05.039)
Picture 1: The disrupted formation of primary cilia in brain tissues of FMCD mouse models and patients with FMCDs caused by brain somatic mutations in MTOR.
Picture 2: The rescue of defective ciliary formation in FMCD mouse models leading to the restoration of cortical dyslamination and defective neuronal migration.
2018.07.02 View 9047 -
KAIST Partners with Taiwan for PhD Scholarship Program
(President Shin, Taiwanese Acting Minister of Education Yao, Deputy Director General Chang at the Ministry of Education pose after signing the MOU.(from left))
President Sung-Chul Shin signed an MOU with the Ministry of Education in Taiwan for the Taiwanese PhD scholarship program. The signing was made between President Shin and Dr. Yao Leehter, acting Minister of Education in Taiwan, on June 27.
The Taiwanese Ministry of Education is signing MOUs with prestigious universities around the world to encourage its students to pursue study abroad opportunities at top schools. According to the MOU, Taiwanese PhD candidates will be able to use KAIST scholarships for their tuition fees, while the Taiwanese government will provide a stipend and living costs for four years from next September.
KAIST became the 14th university to sign this MOU, joining a group of top universities that includes University of Cambridge, Oxford University, California Institute of Technology, and Columbia University in the US. KAIST is the first institution in Asia to sign the MOU.
Acting Minister Yao said, “KAIST has emerged as a world leading university in less than five decades since its foundation. This remarkable growth led us to partner with KAIST. We hope this will serve as an opportunity to further our partnership in research collaboration as well as students exchanges.”
President Shin appreciated the Taiwanese government’s recognition of KAIST’s global reputation. He said, “We will closely collaborate with the Taiwan government and its universities for transforming educational opportunities to better respond to the Fourth Industrial Revolution.
2018.06.27 View 6696 -
The Center for Anthropocene Studies (CAS) Opens
KAIST will start Anthropocene research, a convergence field of study, to address issues related to the commencement of human activities that have had scientific, industrial, and economic impacts on the Earth’s ecosystem. The National Research Foundation (NRF) of Korea endorsed the KAIST Center for Anthropocene Studies as its Convergence Research Center project.
Anthropocene refers to a new geological age in which various polluting materials that humans have made during the post-industrial revolution era have made a significant impact on the Earth and the lives of humankind. The studies expand the diverse socio-economic and environmental sectors for responding to climate change, natural disasters, ecological destruction, the polarization of the inequality and wealth, and many others.
The KAIST research group at the center, in collaboration with the Graduate School of Science and Technology Policy, the Graduate School of Culture Technology, the School of Humanities & Social Sciences, the Department of Industrial Design, the School of Electrical Engineering, the Satellite Technology Research Center (SaRTec), and the KAIST Initiative for Disaster Studies will conduct multidisciplinary research to address intriguing challenges with complex but creative approaches incorporating the fields of engineering, socioeconomics, and art.
The group will investigate topics such as▲ surface and marine changes to the Earth by applying satellite data ▲disaster prediction and governance system building through AI modeling ▲sustainable housing, transportation, and lifestyles ▲ engineering and artistic approaches for envisioning a new future for humankind and the Earth.
Professor Buhm Soon Park, who is in charge of the center, said, “This pioneering research work will inspire the re-creation of a new paradigm of convergence studies in science, engineering, humanities, and social science. We will contribute to making the world better by designing new technologies and social policies.
2018.06.05 View 14699 -
ICISTS 2018: Presence of the Wall, Constraint or Control
A KAIST undergraduates body, ICISTS (International Conference for Integration of Science, Technology and Society) will host the 2018 international conference from July 30 to August 3 at KAIST. Under the theme of “Presence of the Wall: Constraint or Control,” participants will share their opinions on the limits the global world is facing today and look for answers discussing various social issues and technologies. More than 300 students from 60 universities in 15 countries will attend the conference.
Speakers include CEO Sebastien Gendron of TransPod Inc., a Canadian company designing and manufacturing ultra-high-speed transportation technology and vehicles, researcher Sven Kreiss from the Visual Intelligence for Transportation of École Polytechnique Fédérale de Lausanne, Professor Des Freedman from the Department of Media and Communications of Goldsmiths, University of London and political scientist-technologist Wilneida Negrón at the Data & Society Research Institute of Ford Foundation in the US.
The conference will hold programs to facilitate the exchange of ideas among speakers and participants. Participants will make small teams for free discussions to share their ideas and thoughts about issues affecting the human race. Participants will be also assigned a team project in which they must come up with creative ideas based on the lectures. Moreover, they can try new gadgets from companies during the Experience Session.
ICISTS was established in 2005 by undergraduate students from KAIST. The organization holds an international conference every year to explore ways to create harmonization among society, science, and technology. It has grown to become Asia’s largest international student conference.
For learn more and register for the program, please visit http://www.icist.org
2018.05.30 View 7568 -
2018 KAIST Research Day Honors Outstanding Research Achievements
(KAIST President Sung-Chul Shin and Professor Jong-Hwan Kim) Professor Jong-Hwan Kim from the School of Electrical Engineering was recognized at the 2018 KAIST Research Day as the Research Grand Prize Awardee. The ten most distinguished research achievements of the past year were also recognized.
The Research Grand Prize recognizes the professor whose comprehensive research performance evaluation indicator was the highest over the past five years. The indicator combines the number of research contracts, IPR and royalty income.
During the May 25th ceremony, Professor Hyochoong Bang from the Department of Aerospace Engineering and Professor In so Kweon from the School of Electrical Engineering also won the Best Research Award prize.
This year, the Research Innovation Award went to Professor Dong Soo Han from the School of Computing. The Research Innovation Award combines scores in the categories of foreign patent registrations, contracts of technological transfer, and income from technology fees, technology consultations, and startups.
The Convergence Research Award was given to Professor Junmo Kim from the School of Electrical Engineering and Professor Hyun Myung from the Department of Civil & Environmental Engineering. The Convergence Research Award recognizes the most outstanding research team that created innovative research results over a one-year period.
President Sung-Chul Shin said, “KAIST has selected the ten most outstanding research achievements of 2017 conducted by our faculty and researchers. All of them demonstrated exceptional creativity, which opens new research paths in each field though their novelty, innovation, and impact.”
KAIST hosts Research Day every year to introduce major research performances at KAIST and share knowledge about the research and development.
During Research Day, KAIST also announced the ten most distinguished research achievements contributed by KAIST professors during the previous year. They are listed below.
▲ High-Speed Motion Core Technology for Magnetic Memory by Professor Kab-Jin Kim from the Department of Physics
▲ A Double Well Potential System by Professor Jaeyoung Byeon from the Department of Mathematical Sciences
▲ Cheap and Efficient Dehydrogenation of Alkanes by Professor Mu-Hyun Baik from the Department of Chemistry
▲ A Dynamic LPS Transfer Mechanism for Innate Immune Activation by Professor Ho Min Kim from the Graduate School of Medical Science and Engineering
▲ A Memristive Functional Device and Circuit on Fabric for Fibertronics by Professor Yang-Kyu Choi and Professor Sung-Yool Choi from the School of Electrical Engineering
▲ A Hippocampal Morphology Study Based on a Progressive Template Deformable Model by Professor Jinah Park from the School of Computing
▲ The Development of a 6-DOF Dynamic Response Measurement System for Civil Infrastructure Monitoring by Professor Hoon Sohn from the Department of Civil and Environmental Engineering
▲ Cooperative Tumour Cell Membrane Targeted Phototherapy by Professor Ji-Ho Park from the Department of Bio and Brain Engineering
▲ HUMICOTTA: A 3D-Printed Terracotta Humidifier by Professor Sangmin Bae from the Department of Industrial Design
▲ Ultrathin, Cross-Linked Ionic Polymer Thin Films by Professor Sung Gap Im from the Department of Chemical and Biomolecular Engineering
2018.05.28 View 13343 -
KAIST Welcomes Global Participants to AI World Cup 2018
KAIST will host the AI (Artificial Intelligence) World Cup 2018 in August, and this time it is open to the international community. AI World Cup 2018 will be a very exciting challenge for extending the limit of academic and industrial applications based on AI technology.
KAIST, after launching its AI World Cup 2017 for domestic participants, is now hosting the AI World Cup 2018 for everyone. The AI World Cup will be comprised of three events: 1) Five on five AI Soccer 2) AI Commentator and 3) AI Reporter. Winner of each category, runner-up of AI Soccer, and 2nd runner-up of AI Soccer will receive awards with cash prizes.
For AI Soccer in which AI controlled robots team up to compete, the preliminary rounds will be held in July in a league format, and the final rounds will be played on August 20-22.
For AI Commentator and AI Reporter, eight finalists will be selected for each category based on scoring criteria, and their performance will be evaluated by the judges to select the winner from each category on August 22.
During the final rounds, a variety of events will also take place at KAIST, including tutorial sessions on AI technology, a poster session where students present their research works on AI, not necessarily limited to the scope of AI Soccer, AI Commentator, and AI Reporter, and panel discussions by prominent experts in the field of AI.
Moreover, renowned experts on AI will deliver their keynote addresses. The Cyberbotics CEO Olivier Michel will address his keynote speech on the topic ‘Simulation benchmarks and competitions: a fundamental tool to foster robotics research.’
The AI World Cup was established by the College of Engineering at KAIST to show that AI technology can be further extended to sports, soccer in particular.
Professor Jong-Hwan Kim, the inventor of AI World Cup and chairman of the organizing committee said, “I hope that this event will offer a great chance to develop AI technology for use in the coming years. I wish many people can enjoy the AI World Cup 2018. I would recommend that prospective teams not worry about the technical barrier when deciding whether to participate in the games. Participants from academia and industry can test whether their code runs well in the competition simulator; this way, they will know their level of play and perhaps they can further develop their algorithms.”
“We will also broadcast the final round of AI Soccer online so that people in remote areas can also enjoy watching the games. I am looking forward to seeing all of you at the AI World Cup. Any participant with a passion to prove excellence in AI technology is welcomed with open arms,” he added.
Anyone interested in the AI World Cup 2018 can register online via aiworldcup.org . Registration starts from April 1. The deadline for registration and final code submission is June 30.
(Cubical players in the figure for domestic AI Soccer competition have been replaced with cylindrical players for more agile movements while playing)
(Opening ceremony of AI World Cup 2017)
(Trophy and prize)
(Interview of participant)
(Casters commentating on game playing)
2018.03.30 View 9501 -
Successful Synthesis of Gamma-Lanctam Rings from Hydrocarbons
(The team of Professor Chang, far right, at the Department of Chemistry)
KAIST chemists have designed a novel strategy to synthesize ring-shaped cyclic molecules, highly sought-after by pharmaceutical and chemical industries, and known as gamma-lactams. This study describes how these five-membered rings can be prepared from inexpensive and readily available feedstock hydrocarbons, as well as from complex organic molecules, such as amino acids and steroids.
Gamma-lactams find several applications in medicinal, synthetic, and material chemistry. For example, they are included in a large number of pharmaceutically active compounds with antibiotic, anti-inflammatory, and anti-tumoral functions. This research was published in Science on March 2.
Conversion of hydrocarbons into nitrogen-containing compounds is an important area of research, where the challenge lies in breaking strong carbon-hydrogen (C−H) bonds, and converting them into carbon-nitrogen (C–N) bonds in a controlled fashion. For this reason, hydrocarbons are difficult to use as starting materials, albeit the fact that they exist in large quantities in nature.
Over the last 35 years, chemists have found ways of converting simple hydrocarbons into nitrogen-containing rings, such as indoles or pyrrolidines, but gamma-lactams proved impossible to prepare using the same approaches. Researchers hypothesized that such failure was due to alternative chemical pathways that steer the reaction away from the wanted rings: The reaction intermediate (carbonylnitrene) quickly breaks down into unsought products. Using computer models of the desired and undesired reaction pathways, the team found a strategy to completely shut down the latter in order to obtain the longed-for gamma-lactams. For the first time, these four carbons and one nitrogen cyclic molecules were obtained directly from simple feedstock chemicals.
Led by Professor Chang Sukbok at the Department of Chemistry, the team designed the winning reaction with the help of computer simulations that analyze the reaction mechanisms and calculate the energy required for the reaction to take place. According to such computer predictions, the reaction could follow three pathways, leading to the formation of either the desired gamma-lactam, an unwanted product (isocyanate), or the degradation of the catalyst caused by the substrate reacting with the catalyst backbone. Combining experimental observations and detailed computer simulations, the team designed an iridium-based catalyst, highly selective for the gamma-lactam formation. In this way, the two undesired pathways were systematically shut down, leaving the formation of the nitrogen-containing ring as the only possible outcome. Professor Chang is also in charge of the Center for Catalytic Hydrocarbon Functionalizations at the Institute for Basic Science (IBS).
“With this work we offer a brand new solution to a long-standing challenge and demonstrate the power of what we call mechanism-based reaction development,” explains Professor Baik Mu-Hyun, a corresponding author of the study.
Beyond using cheap feedstock hydrocarbons as substrates, the team was also successful in converting amino acids, steroids, and other bio-relevant molecules into gamma-lactams, which might find a variety of applications as plant insecticide, drugs against parasitic worms, or anti-aging agents. This new synthetic technology gives much easier access to these complicated molecules and will enable the development of potential drugs in a much shorter amount of time at a lower cost.
Figure 1: Selective amidation reaction using newly designed iridium (Ir) catalysts. Abundant in nature Hydrocarbons are used as substrates to synthesize nitrogen-containing ring, called gamma-lactams.
Figure 2: Three possible reaction pathways and energy barriers predicted by computational chemistry. The scientists developed new iridium-based catalysts that are highly selective for the C–H insertion pathway which leads to the desired gamma-lactam molecules.
Figure 3: Interesting gamma-lactams derived from natural and unnatural amino acids, steroids, etc., which may be used to protect plants against insects, fight parasitic worms, or as anti-aging agents.
2018.03.02 View 9512 -
KAIST to Develop Technology to Control Topological Defects
(Professor Chan-Ho Yang and PhD candidate Kwang-Eun Kim)
Professor Chan-Ho Yang and his team from the Department of Physics developed technology to create and remove topological defects in ferroelectric nanostructures.
This technology will contribute to developing topological defect-based storage that will allow the saving of massive amounts of information in a stable manner.
Topology refers to the property of matter upon deformation, in which a circle and a triangle are considered to be the same topologically.
During the announcement of the 2016 Nobel Prize in Physics, the concept of topology was explained with a bagel with a hole, cinnamon bread without a hole, and a glass cup. Although the cinnamon bread and the glass cup have different appearances, they are topologically the same since neither has a hole. In the same sense, the bagel and the cinnamon bread are topologically different.
In other words, topology of matter is conserved and its properties cannot be altered by continuous deformation.
Using this topological texture can produce information storage devices that can protect the stored information from external stimuli, but the data can still be written and erased, resulting in ideal non-volatile memory.
Unlike ferroelectrics, magnetic topological defect structures such as the ferromagnetic vortex and skyrmion have already been implemented.
Ferroelectrics, which have aligned electric dipoles without external electric fields, can stabilize topological defect structures to a smaller size using less energy; however, further research on ferroelectrics has not been carried out sufficiently. This is due to a lack of research on stabilizing topological defect structures and how to control them in an experimental setting.
To overcome this problem, the team applied inhomogeneous deformations to ferroelectric nanostructures to successfully stabilize the topological defect structures. The team manufactured a ferroelectric nanoplate structure on a special board, which can exert strong compression from the bottom surface while the sides and the upper surfaces of the structure is free from deformation.
This structure led to radial compressive strain relaxation, in which deformations of the lattice stabilize the vortex structure of ferroelectrics.
This could lead to the establishment of the core principle of topological ferroelectric memory of high density, high efficiency, and high stability.
Professor Yang said, “Ferroelectrics are nonconductor but topological ferroelectric quasiparticles could carry electrical conductivity locally. This finding could be expanded to new quantum device research.”
This research, led by the PhD candidate Kwang-Eun Kim, was published in Nature Communications on January 26.
The study was co-conducted by Professor Si-Young Choi and Dr. Tae Yeong Koo from POSTECH, Professor Long-Qing Chen from The Pennsylvania State University, and Professor Ramamoorthy Ramesh from the University of California at Berkeley.
Figure 1. Five different topological structures produced by controlling the number of topological defects
2018.02.19 View 8269 -
Hubo Completes New Mission at the Winter Olympic Torch Relay
KAIST-born humanoid robot, Hubo, completed its special new mission: carrying the Olympic torch. The Winter Olympics will be held in PyeongChang for two weeks beginning February 9.
On December 11, the final leg of the torch relay in Daejeon for the PyeongChang Olympics 2018 took place inside KAIST. A city known for science and technology hosted special torch relay runners over three days.
Hubo arrived at the campus with Dr. Dennis Hong, a professor from the University of California at Los Angeles, in an autonomous vehicle. Then, Hubo received the flame from Professor Hong. Hubo, a robot developed by Professor Jun Ho Oh from the Department of Mechanical Engineering at KAIST, is best known for being the winner of the DARPA Robotics Challenge in 2015.
Hubo successfully completed its Olympic mission. That is, it had to drill through a wall to deliver the torch to the next runner. After completing the mission successfully, the torch was passed to Professor Oh. He ran a few steps and handed it over to the last runner of the Daejeon leg.
The last runner was Jung Jae Lee, who is a winning team member of the Samsung Junior Software Cup. Lee also had the honor of riding and controlling FX-2 which is another robot developed by Professor Oh for this peace torch relay. FX-2 took a few steps to finalize the relay.
Lee said, “I would like to become an expert in security. As I was riding the robot, I felt every step I took was one step closer to achieving of making major developments in the field of security.
Professor Oh said, “It is meaningful to see humans and robots cooperating with each other to carry out the torch relay.”
The torch relay, participated in by both humans and robots in Daejeon, was successfully completed and the torch headed off to Boryeong, Chungcheongnam-do.
2017.12.12 View 12123 -
A New Spin Current Generating Material Developed
(Professor Park(left) and Ph.D. candidate Kim)
Magnetic random-access memory (MRAM) is a non-volatile device made of thin magnetic film that can maintain information without an external power supply, in contrast to conventional silicon-based semiconductor memory. It also has the potential for high-density integration and high-speed operation.
The operation of MRAM involves the control of the magnetization direction by exerting spin current-induced torque on a magnetic material. Spin current is generated using electricity in conventional MRAM, but this study developed materials technology that generates spin current using heat.
A KAIST research team led by Professor Byong-Guk Park of the Department of Materials Science and Engineering developed a material that generates spin current from heat, which can be utilized for a new operation principle for MRAM.
There have been theoretical reports on the spin Nernst effect, the phenomenon of the thermal generation of spin current, but is yet to have been experimentally proven due to technological limitations. However, the research team introduced a spin Nernst magnetoresistance measurement method using tungsten (W) and platinum (Pt) with high spin orbit coupling which allows for the experimental identification of the spin Nernst effect. They also demonstrated that the efficiency of spin current generation from heat is similar to that of spin current generated from electricity.
Professor Park said, “This research has great significance in experimentally proving spin current generation from heat, a new physical phenomenon. We aim to develop the technology as a new operational method for MRAM through further research. This can lower power consumption, and is expected to contribute to the advancement of electronics requiring low power requirement such as wearable, mobile, and IOT devices”.
This research was conducted as a joint research project with Professor Kyung-Jin Lee at Korea University and Professor Jong-Ryul Jeong at Chungnam National University. It was published in Nature Communications online on November 9 titled “Observation of transverse spin Nernst magnetoresistance induced by thermal spin current in ferromagnet/non-magnet bilayers.” Ph.D. candidate Dong-Jun Kim at KAIST is the first author. This research was funded by the Ministry of Science and ICT.
(Schematic diagram of spin Nernst magnetoresistance)
(Research result of new spin current generating materials)
2017.12.08 View 9363 -
Expanding Gas Storage Capacity of Nanoporous Materials
A KAIST research team led by Professor Jihan Kim of the Department of Chemical and Biomolecular Engineering has successfully proposed a rational defect engineering methodology that can greatly enhance the gas storage capacity of nanoporous materials. The team conducted a high-throughput computational screening of a large experimental metal-organic framework database to identify 13 candidate materials that could experience significant methane uptake enhancement with only a small proportion of linker vacancy defects.
This research was published online on November 16 in Nature Communications, with M.S. candidate Sanggyu Chong from KAIST as the first author and post-doctorate researcher Günther Thiele from the Department of Chemistry at UC Berkeley as a contributing author.
Metal-organic frameworks, hereinafter MOF, are crystalline nanoporous materials that are comprised of metal clusters and organic linkers continuously bound together by coordination bonds. Due to their ultrahigh surface areas and pore volumes, they have been widely studied for various energy and environment applications.
Similar to other crystalline materials, MOFs are never perfectly crystalline and are likely to contain several different types of defects within their crystalline structures. Among these defects, linker vacancy defects, or the random absence of linker vacancies in their designated bonding positions, are known to be controllable by practicing careful control over the synthesis conditions.
The research team combined the concepts of rational defect engineering over the linker vacancy defects and the potential presence of inaccessible pores within MOFs to propose a methodology where controlled the introduction of linker vacancy defects could lead to a dramatic enhancement in gas adsorption and storage capacities.
The study utilized a Graphic Processing Unit (GPU) code developed by Professor Kim in a high-throughput computational screening of 12,000 experimentally synthesized MOFs to identify the structures with significant amounts of pores that were inaccessible for methane. In determining the presence of inaccessible pores, a flood-fill algorithm was performed over the energy-low regions of the structure, which is the same algorithm used for filling an area with color in Microsoft Paint.
For the MOFs with significant amounts of inaccessible pores, as determined from the screening, the research team emulated linker vacancy defects in their crystalline structures so that the previously inaccessible pores would be newly merged into the main adsorption channel with the introduction of defects for additional surface area and pore volume available for adsorption. The research team successfully identified 13 structures that would experience up to a 55.56% increase in their methane uptake with less than 8.33% of the linker vacancy defects.
The research team believes that this rational defect engineering scheme can be further utilized for many other applications in areas such as selective adsorption of an adsorbate from a gas mixture and the semi-permanent capture of gas molecules.
This research was conducted with the support of the Mid-career Research Program of the National Research Foundation of Korea.
Figure1. A diagram for flood fill algorithm and example of identification of inaccessible regions within the MOFs, using the flood fill algorithm
Figure2. Methane energy contours before and after detect introduction
2017.12.04 View 8930