Engineering
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Mutant Gene Network in Colon Cancer Identified
The principles of the gene network for colon tumorigenesis have been identified by a KAIST research team. The principles will be used to find the molecular target for effective anti-cancer drugs in the future. Further, this research gained attention for using a systems biology approach, which is an integrated research area of IT and BT.
The KAIST research team led by Professor Kwang-Hyun Cho for the Department of Bio and Brain Engineering succeeded in the identification. Conducted by Dr. Dongkwan Shin and student researchers Jonghoon Lee and Jeong-Ryeol Gong, the research was published in Nature Communications online on November 2.
Human cancer is caused by genetic mutations. The frequency of the mutations differs by the type of cancer; for example, only around 10 mutations are found in leukemia and childhood cancer, but an average of 50 mutations are found in adult solid cancers and even hundreds of mutations are found in cancers due to external factors, such as with lung cancer.
Cancer researchers around the world are working to identify frequently found genetic mutations in patients, and in turn identify important cancer-inducing genes (called ‘driver genes’) to develop targets for anti-cancer drugs. However, gene mutations not only affect their own functions but also affect other genes through interactions. Therefore, there are limitations in current treatments targeting a few cancer-inducing genes without further knowledge on gene networks, hence current drugs are only effective in a few patients and often induce drug resistance.
Professor Cho’s team used large-scale genomic data from cancer patients to construct a mathematical model on the cooperative effects of multiple genetic mutations found in gene interaction networks. The basis of the model construction was The Cancer Genome Atlas (TCGA) presented at the International Cancer Genome Consortium. The team successfully quantified the effects of mutations in gene networks to group colon cancer patients by clinical characteristics.
Further, the critical transition phenomenon that occurs in tumorigenesis was identified using large-scale computer simulation analysis, which was the first hidden gene network principle to be identified. Critical transition is the phenomenon in which the state of matter is suddenly changed through phase transition. It was not possible to identify the presence of transition phenomenon in the past, as it was difficult to track the sequence of gene mutations during tumorigenesis.
The research team used a systems biology-based research method to find that colon cancer tumorigenesis shows a critical transition phenomenon if the known driver gene mutations follow sequentially. Using the developed mathematical model, it can be possible to develop a new anti-cancer targeting drug that most effectively inhibits the effects of many gene mutations found in cancer patients. In particular, not only driver genes, but also other passenger genes affected by the gene mutations, could be evaluated to find the most effective drug targets.
Professor Cho said, “Little was known about the contribution of many gene mutations during tumorigenesis.” He continued, “In this research, a systems biology approach identified the principle of gene networks for the first time to suggest the possibility of anti-cancer drug target identification from a new perspective.”
This research was funded by the Ministry of Science and ICT and the National Research Foundation of Korea.
Figure1. Formation of giant clusters via mutation propagation
Figure2. Critical transition phenomenon by cooperative effect of mutations in tumorigenesis
2017.11.10 View 7357 -
LG's Woo Jong Lee Named the Alumnus of College of Engineering
The College of Engineering at KAIST selected Woo Jong Lee, President and Head of the VC Business Division at LG Electronics Inc., as the 2017 Alumnus of the Year for the College of Engineering.
‘Alumnus of the Year’ is an award given to a distinguished alumnus who has contributed to the development of industrial technology or made outstanding academic achievements.
Lee graduated from KAIST with the master’s degrees in Industrial Engineering. He also worked at Daewoo Motors as an executive member in the development division. He has been a crucial human resource for LG since he joined the company in 2000.
While leading the VC business Division, which was established in 2013, Lee is recognized as a creative engineer as well as a leader in the automotive industry. Focusing on autonomous driving and eco-friendliness, he has been engaged in the production of major projects from the beginning to the end.
Since 2014, outstanding alumni whose achievements have represented KAIST at the highest level have received the award. The first recipient was Tae-Kyung Yoo, an executive at Lumens Co., Ltd., and the second recipient was Jung-Ju Kim, the founder of NXC. In 2016, the award was not given because an appropriate candidate could not be identified.
The award was held in the Industrial Engineering & Management Building (E2) on November 8. Faculty members including the dean of the College of Engineering Jong-Hwan Kim, the vice dean Hyochoong Bang, the head of Industrial & Systems Engineering Taesik Lee, and the dean of the KAIST Academy Tae-Eog Lee attended the ceremony.
After the ceremony, Lee delivered a lecture on ‘Auto-components Business of LG Electronics’ to KAIST students.
2017.11.09 View 7159 -
Professor Lee's Research Selected as Top 100 National R&D Projects
A research project, led by Research Professor Ju Yong Lee from the KAIST Institute for IT Convergence, was selected as one of the Top 100 National Research and Development Projects 2017.
This research project, titled LTE-A-based Single RF Small Base Station supporting Multiple Streams, developed 300Mbps low power, low complexity and broadband small base station technology that supports 4x4 MIMO (Multiple Input and Multiple Output) by proposing a new antenna structure and a new RF (Radio Frequency) structure based on LTE-A. Professors from the School of Electrical Engineering at KAIST, Dong Ho Cho, Songcheol Hong, and Yong Hoon Lee also collaborated on the project.
The existing heterodyne method of communication systems generates the problems of increasing unit price and system complexity.
In this project, however, Professor Lee directly modulated the baseband signal from the RF stage through an impedance loading-based RF chip. This method was designed to facilitate low power as well as low complexity while supporting broadband service. Based on this, his team developed source technology for RF that can be applied to fourth and even fifth generation networks.
Furthermore, this base station is smallest among the small-cell stations so far, providing an eco-friendly installation environment. It contributes to the market for fifth generation mobile communications by reducing power consumption significantly yet providing high-capacity services.
Professor Lee said, “This technology will contribute to creating a new market and additional jobs because business based on the fifth mobile generation can provide multi-functional services, including multiband. Requiring low power and providing high-capacity services anywhere at any time will enhance national competence and reduce costs for establishing a next generation mobile communication system. It is expected that this technology will help with disseminating mobile communication infrastructure through expanding information and communication system as well as the infrastructure of island areas.”
2017.11.08 View 7508 -
Highly Flexible Organic Flash Memory for Foldable and Disposable Electronics
A KAIST team reported ultra-flexible organic flash memory that is bendable down to a radius of 300μm. The memory exhibits a significantly-long projected retention rate with a programming voltage on par with the present industrial standards.
A joint research team led by Professor Seunghyup Yoo of the School of Electrical Engineering and Professor Sung Gap Im of the Department of Chemical and Biomolecular Engineering said that their memory technology can be applied to non-conventional substrates, such as plastics and papers, to demonstrate its feasibility over a wide range of applications.
With Dr. Seungwon Lee and Dr. Hanul Moon playing the role of leading authors, the research was published in Nature Communications on September 28.
Flash memory is a non-volatile, transistor-based data-storage device that has become essential in most electronic systems in daily life. With straightforward operation mechanisms and easy integration into NAND or NOR array architecture, flash memory has been established as the most successful and dominant non-volatile memory technology by far.
Despite promising demonstrations in the early stages of organic electronics, the overall progress in this field has been far slower than that of thin-film transistors (TFTs) or other devices based on flexible materials. It has been challenging, in particular, to develop flash memory that simultaneously exhibits a significant level of flexibility and performance. This is mainly due to the scarcity of flexible dielectric layers, which are responsible for the tunneling and blocking of charges.
The solution processing used for the preparation of most of the polymeric dielectric layers also makes it difficult to use them in flash memory due to the complexity involved in the formation of the bilayer dielectric structure, which is the key to flash memory operations.
The research team tried to overcome these hurdles and realize highly flexible flash memory by employing thin polymeric insulators grown with initiated chemical vapor deposition (iCVD), a vapor-phase growth technique for polymers that was previously shown to be promising for the fabrication of flexible TFTs. It was further shown that these iCVD-based polymeric insulators, when coupled with rational device design and material choice, can make a significant contribution to flash memory as well.
Memory using conventional polymer insulating films has often required a voltage as high as 100 V (volt) in order to attain long memory retention. If the device is made to operate at a low voltage, the short retention period of less than a month was problematic.
The KAIST team produced flash memory with programming voltages around 10 V and a projected data retention time of over 10 years, while maintaining its memory performance even at a mechanical strain of 2.8%. This is a significant improvement over the existing inorganic insulation layer-based flash memory that allowed only a 1% strain.
The team demonstrated the virtually foldable memory devices by fabricating the proposed flash memory on a 6-micrometer-thick ultrathin plastic film. In addition, it succeeded in producing them on printing paper, opening a way for disposable smart electronic products such as electronic paper and electronic business card.
Professor Yoo said, " This study well illustrates that even highly flexible flash memory can be made to have a practically viable level of performance, so that it contributes to full-fledged wearable electronic devices and smart electronic paper."
(Figure 1. Structure of flexible flash memory )
(Figure 2. Foldable flash memory)
2017.11.06 View 8571 -
Scientist of November, Professor Hyung Jin Sung
Professor Hyung Jin Sung from the Department of Mechanical Engineering at KAIST received a ‘Science and Technology Award of the Month’ given by the Ministry of ICT and Science and the National Research Foundation of Korea for November 2017. He developed technology that can exquisitely control a micrometer-scaled liquid drop on a dime-sized lab-on-a-chip. With his work, he was recognized for reinforcing research capability on microfluidics.
Lab-on-a-chip is an emerging experiment and diagnostic technology in the form of a bio-microchip that facilitates complex and various experiments with only a minimal sample size required. This technology draws a lot of attention not only from medical and pharmaceutical areas, but also the health and environmental field. The biggest problem was that technology for the temperature control of a fluid sample, which is one of the core technologies in microfluidics, has low accuracy. This limit had to be overcome in order to use the lab-on-a-chip more widely.
Professor Sung developed an acoustic and thermal method which controls the temperature of a droplet quickly and meticulously by using sound and energy. This is a thermal method that uses heat generated during the absorption of an acoustic wave into viscoelastic substances. It facilitates a rapid heating rate and spatial-temporal temperature control, allowing heating in desired areas. In addition, Professor Sung applied his technology to polymerase chain reactions, which are used to amplify DNA.
Through this experiment, he successfully shortened the reaction time from 1-2 hours to only three minutes, making this a groundbreaking achievement.
Professor Sung said, “My research is significant for enhancing the applicability of microfluidics. I expect that it will lead to technological innovations in healthcare fields including biochemistry, medical checkups, and new medicine development.”
2017.11.03 View 8153 -
Platinum Single Atom Catalysts for 'Direct Formic Acid Fuel Cells'
(Professor Hyunjoo Lee (left) and Ph.D. candidate Jiwhan Kim)
A research team co-led by Professor Hyunjoo Lee at the Department of Chemical and Biomolecular Engineering at KAIST and Professor Jeong Woo Han from the University of Seoul synthesized highly stable high-Pt-content single atom catalysts for direct formic acid fuel cells. The amount of platinum can be reduced to 1/10 of that of conventional platinum nanoparticle catalysts.
Platinum (Pt) catalysts have been used in various catalytic reactions due to their high activity and stability. However, because Pt is rare and expensive, it is important to reduce the amount of Pt used. Pt single atom catalysts can reduce the size of the Pt particles to the size of an atom. Thus, the cost of Pt catalysts can be minimized because all of the Pt atoms can participate in the catalytic reactions. Additionally, single atom catalysts have no ensemble site in which two or more atoms are attached, and thus, the reaction selectivity is different from that of nanoparticle catalysts.
Despite these advantages, single atom catalysts are easily aggregated and less stable due to their low coordination number and high surface free energy. It is difficult to develop a single atom catalyst with high content and high stability, and thus, its application in practical devices is limited.
Direct formic acid fuel cells can be an energy source for next-generation portable devices because liquid formic acid as a fuel is safer and easier to store and transport than high-pressure hydrogen gas.
To improve the stability of Pt single atom catalysts, Professor Lee’s group developed a Pt-Sn single atom alloy structure on an antimony-doped tin oxide (ATO) support. This structure has been proven by computational calculations which show that Pt single atoms substitute antimony sites in the antimony-tin alloy structure and are thermodynamically stable. This catalyst has been shown to have a higher activity up to 50 times per weight of Pt than that of the commercial catalyst, Pt/C, in the oxidation of formic acid, and the stability of the catalyst was also remarkably high.
Professor Lee’s group also used a single atomic catalyst in a 'direct formic acid fuel cell’ consisting of membranes and electrodes. It is the first attempt to apply a single atomic catalyst to a full cell. In this case, an output similar to that of the commercial catalyst could be obtained by using 1/10 of the platinum compared to the commercial Pt/C catalyst.
Ph.D. candidate Jiwhan Kim from KAIST was the first author of the research. This research was published online on September 11 in Advanced Energy Materials.
This research was carried out with the support of the Samsung Electronics Future Technology Development Center.
(Figure 1. Concept photograph for Pt single atom catalysts.)
(Figure 2. Pt single atom catalysts by HAADF-STEM analysis (bright white circles))
2017.10.31 View 6950 -
In Jin Cho Earned the Best Poster Prize at ME Summit 2017
In Jin Cho, a Ph.D. student in the Department of Chemical and Biomolecular Engineering at KAIST received the best poster prize at the International Metabolic Engineering Summit 2017 held on October 24 in Beijing, China.
The International Metabolic Engineering Summit is a global conference where scientists and corporate researchers in the field of metabolic engineering present their latest research outcomes and build networks.
At this year’s summit, about 500 researchers from around the world participated in active academic exchanges, including giving keynote speeches and presenting posters.
During the poster session, the summit selects one person for the KeAi-synthetic and Systems Biotechnology Poster Award, two for Microbial Cell Factories Poster Awards, and three for Biotechnology Journal Poster Awards among the posters presented by graduate students, post-doctoral fellows and researchers. Cho received the KeAi-synthetic and Systems Biotechnology Poster Award. Her winning poster is on the biotransformation of p-xylene to terephthalic acid using engineered Escherichia coli.
Terephthalic acid is generally produced by p-xylene oxidation; however, this process requires a high temperature and pressure as well as a toxic catalyst during the reaction process.
Cho and Ziwei Luo, a Ph.D. student at KAIST, co-conducted the research and developed a successful biological conversion process. Compared to the existing chemical process, it does not require a high temperature and pressure; and it is environmentally friendly with a relatively high conversion rate of approximately 97%.
Cho’s advisor, Distinguished Professor Sang Yup Lee said, “Further research on glucose-derived terephthalic acid will enable us to produce biomass-based eco-friendly terephthalic acid through engineered Escherichia coli.”
2017.10.31 View 7992 -
Hanmaeum Education Corps Invites Multicultural Families
About 100 graduates from the Multicultural Mother Schools and their families visited the KAIST campus on October 29 at the invitation of the Hanmaeum Education Corps of KAIST. The Hanmanum Education Corps is a volunteering organization composed of KAIST faculty and students. Many retired KAIST faculties are also members of the corps. Byong Kyu Choi, an Emeritus Professor from the Department of Industrial and Systems Engineering, is the director of the corps and has been leading the event since 2015.
With the support of a KAIST educational volunteering organization called SEED(Social Education Embracing Diversity), this year’s event offered various activities including a treasure hunt and convergent science programs. Participants had the opportunity to experience KAIST’s educational environment and enjoyed the perfect autumn weather during outdoor activities with student volunteers.
Children enjoyed making illumination-music stickers with the KAIST students, even though it was tough to learn at first.
While the children engaged themselves in the science program, parents visited the chrysanthemum fair and some of KAIST’s cafeterias.
Hanmaeum Education Corps opened the Multicultural Mother Schools to support multicultural mothers so that they can have more interest in and help their children more with their education. Since its establishment in 2015, the Multicultural Mother Schools have been expanding throughout the country.
The corporation hopes that visiting a renowned university will encourage children from multicultural families to study hard in addition to offering self-enrichment opportunities through career exploration and science activities.
2017.10.30 View 4332 -
Distinguished Professor Lee Named International Fellow of the CAS
Distinguished Professor Sang Yup Lee from the Department of Chemical and Biomolecular Engineering at KAIST was awarded the title of distinguished professor and international fellow from the Chinese Academy of Sciences (CAS), and honorary professor from its affiliated organization the Tianjin Institute of Industrial Biotechnology (TIB).
The CAS recognized Distinguished Professor Lee for his significant contributions to biotechnology. He has made significant pioneering academic achievements in the area of systems metabolic engineering, which produces useful chemicals from microorganisms. Not only did he develop the first and best source technology in that field, but also came out with processes for the production of biofuel and environmentally-friendly chemicals.”
As a global leader in systems metabolic engineering, Distinguished Professor Lee has also been appointed as an honorary professor at Jiangnan University in Wuxi, China.
Distinguished Professor Lee was listed in the ‘Top 20 Translational Researchers of 2014’ selected by the renowned international journal Nature Biotechnology. Moreover, he was the first Asian recipient of the James E. Bailey Award in 2016 and Marvin J. Johnson Award in 2012, which are given to scholars in the field of biotechnology.
He is also one of 13 global scientists who are foreign members of the renowned academic societies the National Academy of Engineering and the National Academy of Sciences in the US. Furthermore, he received the ‘2017 Korea Best Scientist Award’ from the president of Korea in July. Finally, his founding field, systems metabolic engineering, was chosen as one of the ‘Top 10 Emerging Technologies of 2016’ by the World Economic Forum.
The Chinese Academy of Sciences, established in November 1949, is an academic organization that carries out research on basic sciences and natural sciences in China. It defined its science and technology system to include the fields of basic sciences, natural sciences, and high technology. While having a base in Beijing, its branch academies are located in 12 main cities along with 117 affiliates and 100 national key labs.
2017.10.26 View 9584 -
Development of a Highly-Accurate Computational Model of Human Metabolism
A research team from KAIST developed a computational framework that enables the reconstruction of a comprehensive computational model of human metabolism, which allows for an accurate prediction of personal metabolic features (or phenotypes).
Understanding personal metabolic phenotypes allows us to design effective therapeutic strategies for various chronic and infectious diseases. A human computational model called the genome-scale metabolic model (GEM) contains information on thousands of metabolic genes and their corresponding reactions and metabolites, and has played an important role in predicting metabolic phenotypes. Although several versions of human GEMs have been released, they had room for further development, especially as to incorporating biological information coming from a human genetics mechanism called “alternative splicing.” Alternative splicing is a genetic mechanism that allows a gene to give rise to multiple reactions, and is strongly associated with pathology.
To tackle this problem, Jae Yong Ryu (a Ph.D. student), Dr. Hyun Uk Kim (Research Fellow), and Distinguished Professor Sang Yup Lee, all from the Department of Chemical and Biomolecular Engineering at KAIST, developed a computational framework that systematically generates metabolic reactions, and adds them to the human GEM. The resulting human GEM was demonstrated to accurately predict metabolic phenotypes under varied environmental conditions. The research results were published online in Proceedings of the National Academy of Sciences (PNAS) on October 24, 2017, under the title “Framework and resource for more than 11,000 gene-transcript-protein-reaction associations in human metabolism.”
The research team first updated the biological contents of a previous version of the human GEM. The updated biological contents include metabolic genes and their corresponding metabolites and reactions. In particular, metabolic reactions catalyzed by already-known protein isoforms were additionally incorporated into the human GEM; protein isoforms are multiple variants of proteins generated from individual genes through the alternative splicing process. Each protein isoform is often responsible for the operation of a metabolic reaction. Although multiple protein isoforms generated from one gene can play different functions by having different sets of protein domains and/or subcellular localizations, such information was not properly considered in previous versions of human GEMs.
Upon the initial update of the human GEM, named Recon 2M.1, the research team subsequently implemented a computational framework that systematically generates information on Gene-Transcript-Protein-Reaction Associations (GeTPRA) in order to identify protein isoforms that were previously not identified. This framework was developed in this study. As a result of the implementation of the framework for GeTPRA, more than 11,000 GeTPRA were automatically predicted, and thoroughly validated. Additional metabolic reactions were then added to Recon 2M.1 based on the predicted GeTPRA for the previously uncharacterized protein isoforms; Recon 2M.1 was renamed Recon 2M.2 from this upgrade.
Finally, Recon 2M.2 was integrated with 446 sets of personal biological data (RNA-Seq data) in order to build patient-specific cancer models. These patient-specific cancer models were used to predict cancer metabolism activities and anticancer targets.
The development of a new version of human GEMs along with the computational framework for GeTPRA is expected to boost studies in fundamental human genetics and medicine. Model files of the human GEMs Recon 2M.1 and 2M.2, a full list of the GeTPRA and the source code for the computational framework to predict the GeTPRA are all available as part of the publication of this study.
Distinguished Professor Lee said, “The predicted GeTPRA from the computational framework is expected to serve as a guideline for future experiments on human genetics and biochemistry, whereas the resulting Recon 2M.2 can be used to predict drug targets for various human diseases.”
This work was supported by the Technology Development Program to Solve Climate Changes on Systems Metabolic Engineering for Biorefineries (NRF-2012M1A2A2026556 and NRF-2012M1A2A2026557) from the Ministry of Science and ICT through the National Research Foundation (NRF) of Korea.
(Figure 1:A scheme of Recon 2M.1 development and its use in reconstructing personal genome-scale metabolic models (GEMs). (A) A concept of alternative splicing of human genes and its use in Gene-Transcript-Protein-Reaction Associations (GeTPRA) of Recon 2M.1. (B) A procedure of systematic refinement of the Recon 2Q. Recon 2Q is one of the previously released human GEMs. Biochemically inconsistent reactions include unbalanced, artificial, blocked, and/or redundant reactions. Iterative manual curation was conducted while validating the Recon 2M.1. (C) Reconstruction of cancer patient-specific GEMs using Recon 2M.1 for further simulation studies. In this study, personal biological data (RNA-Seq data) were obtained from The Cancer Genome Atlas (TCGA; https://cancergenome.nih.gov/ ) across the ten cancer types.
(Figure 2: Computational framework for the systematic generation of Gene-Transcript-Protein-Reaction Associations (GeTPRA; red box in the flowchart). Peptide sequences of metabolic genes defined in Recon 2M.1 were retrieved from a database called Ensembl. EC numbers and subcellular localizations of all the protein isoforms of metabolic genes in Recon 2M.1 were predicted using software programs EFICAz2.5 and Wolf PSort, respectively. Information on the newly predicted GeTPRA was systematically incorporated into the Recon 2M.1, thereby resulting in Recon 2M.2.)
2017.10.25 View 8709 -
Professor Dai Gil Lee Recognized by the ICCS
Emeritus Professor Dai Gil Lee, from the School of Mechanical and Aerospace Engineering at KAIST, received a special achievement award from the 20th International Conference on Composite Structures (ICCS).
ICCS is a renowned conference in the field of applied composite structures, which highlights the practicality of composite structures. This year, the conference was held at the Conservatoire National des Arts et Métiers (CNAM), Paris, France from September 4 to 7. Approximately 650 papers were presented from 45 countries.
Especially, the conference honored Emeritus Professor Lee, who has been engaged in ICCS since 1993 and received best paper award twice. The ICCS recognized him for serving with distinction in science and technology in the fields of composite materials and structures. As a member of the Editorial Board for many years, he gave significant support to the journal Composite Structures. At the conference, he gave a special lecture titled ‘Lightweight Carbon Composite Proton Exchange Membrane Fuel Cells’.
Professor Lee said, “I will dedicate myself to innovate Vanadium Redox Flow Battery-ESS (VRFB) based on the research findings announced at the conference and related patents. I am hoping that these efforts will contribute to solving energy issues around the world.”
2017.10.19 View 6554 -
Ultra-Fast and Ultra-Sensitive Hydrogen Sensor
(From left: Professor Kim, Ph.D. candidate Koo, and Professor Penner)
A KAIST team made an ultra-fast hydrogen sensor that can detect hydrogen gas levels under 1% in less than seven seconds. The sensor also can detect hundreds of parts per million levels of hydrogen gas within 60 seconds at room temperature.
A research group under Professor Il-Doo Kim in the Department of Materials Science and Engineering at KAIST, in collaboration with Professor Reginald M. Penner of the University of California-Irvine, has developed an ultra-fast hydrogen gas detection system based on a palladium (Pd) nanowire array coated with a metal-organic framework (MOF).
Hydrogen has been regarded as an eco-friendly next-generation energy source. However, it is a flammable gas that can explode even with a small spark. For safety, the lower explosion limit for hydrogen gas is 4 vol% so sensors should be able to detect the colorless and odorless hydrogen molecule quickly. The importance of sensors capable of rapidly detecting colorless and odorless hydrogen gas has been emphasized in recent guidelines issued by the U.S. Department of Energy. According to the guidelines, hydrogen sensors should detect 1 vol% of hydrogen in air in less than 60 seconds for adequate response and recovery times.
To overcome the limitations of Pd-based hydrogen sensors, the research team introduced a MOF layer on top of a Pd nanowire array. Lithographically patterned Pd nanowires were simply overcoated with a Zn-based zeolite imidazole framework (ZIF-8) layer composed of Zn ions and organic ligands. ZIF-8 film is easily coated on Pd nanowires by simple dipping (for 2–6 hours) in a methanol solution including Zn (NO3)2·6H2O and 2-methylimidazole.
(This cover image depicts lithographically-patterned Pd nanowires overcoated with a Zn-based zeolite imidazole framework (ZIF-8) layer.)
As synthesized ZIF-8 is a highly porous material composed of a number of micro-pores of 0.34 nm and 1.16 nm, hydrogen gas with a kinetic diameter of 0.289 nm can easily penetrate inside the ZIF-8 membrane, while large molecules (> 0.34 nm) are effectively screened by the MOF filter. Thus, the ZIF-8 filter on the Pd nanowires allows the predominant penetration of hydrogen molecules, leading to the acceleration of Pd-based H2 sensors with a 20-fold faster recovery and response speed compared to pristine Pd nanowires at room temperature.
Professor Kim expects that the ultra-fast hydrogen sensor can be useful for the prevention of explosion accidents caused by the leakage of hydrogen gas. In addition, he expects that other harmful gases in the air can be accurately detected through effective nano-filtration by using of a variety of MOF layers.
This study was carried out by Ph.D. candidate Won-Tae Koo (first author), Professor Kim (co-corresponding author), and Professor Penner (co-corresponding author). The study has been published in the online edition of ACS Nano, as the cover-featured image for the September issue.
Figure 1. Representative image for this paper published in ACS Nano, August, 18.
Figure 2. Images of Pd nanowire array-based hydrogen sensors, scanning electron microscopy image of a Pd nanowire covered by a metal-organic framework layer, and the hydrogen sensing properties of the sensors.
Figure 3. Schematic illustration of a metal-organic framework (MOF). The MOF, consisting of metal ions and organic ligands, is a highly porous material with an ultrahigh surface area. The various structures of MOFs can be synthesized depending on the kinds of metal ions and organic ligands.
2017.09.28 View 10005