News Articles on Research Outcome
▣ Prof. Hyun-myung Jang, New Technology to Tune Quantum Dot Band Gap

A new technology to tune a band gap, used for display devices, ultra-fine semiconductors and medical appliances, has been developed.

Dr. Eui-hyun Kong’s team of POSTECH Materials Science and Engineering Department (Academic Advisor: Prof. Hyun-myung Jang) has succeeded in developing a new technology to tune a band gap by using phase transition in quantum dots and letting two states coexist.

When this new technology is applied, optical characteristics of electrodes are significantly increased and the efficiency of quantum dot-sensitive solar cells could be raised by 50%.

A quantum dot band gap, also called an energy gap, is the difference in energy between when an electron exists and when it does’t. This difference in energy is an important characteristic that determines electrical conductivity levels. Therefore, research on band gap control is critical to open possibilities to drastically improve optical, electrical characteristics of quantum dots, which are used for display devices, semiconductors and medical appliances relying on their conductivity.

A number of researches have been conducted to control band gaps, but only with complicated methods and too much costs.

Dr. Kong’s team has suggested the band gap tuning technology by distorting a lattice in quantum dots through a short period of heat treatment in the air without expensive devices such as vacuum equipment. This way not only takes a shortened process time but also greatly reduced production costs.

The new technology is expected to be applied to a variety of appliances using quantum dots, since it can be applied to a number of types of semiconductor quantum dots.

The paper on this discovery was published as the cover of April issue of Small, the prestigious academic journal on materials science.

Quantum Dots: Bandgap Tuning by Using a Lattice Distortion Induced by Two Symmetries That Coexist in a Quantum Dot  Small, 10, 7, 1299 (2014) (IF: 7.823)

▣ Prof. Wang-cheol Zin (Center for Advanced Soft Electonics), Closer to Commercialization of Graphene Transparent Electrodes

Ministry of Science, ICT and Future Planning announced on May 30 that Center for Advanced Soft Electronics, launched as part of Global Frontier Project, developed a technology to visualize graphene domains and defects without a complex process.

The research was conducted by the members of the Center, Jong-hyun Ahn, professor at School of Electrical & Electronic Engineering of Yonsei University; Wang-cheol Zin, professor at POSTECH Materials Science and Engineering department; Jong-ho Son, Senior Researcher at Samsung Display Research Center; and Seung-Jae Baeck, Researcher at School of Electrical & Electronic Engineering of Yonsei University.

Graphene, a single sheet of carbon atoms, is a promising next generation transparent electrode material due to its flexibility. However, to make current flow through graphene effectively, nano structure has to be well controlled, and the controlling process involving electron microscopes is complicated. To control the less-than-one nano meter thickness of a film is also not easy.

The research team’s new technology allows optically analyzing crystal structure and defect distribution on the thin film of graphene using liquid crystal. Based on the technology, the team succeeded in imaging how defects in graphene are created depending on the change in mechanical stress from outside.

The team found out that when liquid crystal is coated on a thin film of graphene, liquid crystal turns its direction in alignment with graphene domains. Without extra complicated process, graphene domains could be easily observed and defects detected by looking into the image of liquid crystal in changed direction.

Because the time and cost required to analyze large-scale graphene can be drastically reduced, the new technology is expected to be used for commercialization of flexible, graphene-based transparent electrodes.


Detection of graphene domains and defects using liquid crystals

Nature Communications, 5, 3484 (2014) (IF: 10.015)


▣ Prof. Sei-kwang Hahn, Triple as Effective Drug Delivery System for Hepatitis C

Ministry of Science, ICT and Future Planning announced on February 19 that POSTECH Academia-Industry Collaboration Foundation transferred the technology for its new drug delivery system for hyaluronic acid-based hepatitis C medicine to Shin Poong Pharm Co. Hepatitis C has been usually treated with PEGylated interferon such as Pegasys of Swiss Hoffman La Loche and PEG-Intron of American Merch, accompanied by Ribavirin.

But PEGylated interferon, when injected into the system, moves to organs other than the liver through the blood vessels resulting in decreased effectiveness on the liver and causes side effects including hair loss, anemia and pulmonary edema with repeated dosing.

The new system developed by Prof. Hahn's team more exclusively targets the liver than PEGylated interferon and minimizes the side effects on other organs. When experimented on animals, the effectiveness was double or triple as that of PEGylated interferon.

Prof. Hahn is quoted as saying, “If this technology is commercialized, the new cure is expected to successfully enter the global hepatitis C medicine market, amounting to an estimate of more than 6 trillion won per year. And the technology can be also used to seek a cure for other liver disorders including hepatocirrhosis and liver cancer.”

POSTECH Prof. Hahn's team conducted the research with the support from Ministry of Science, ICT and Future Planning, under the conditions that it is paid a fixed fee of 500 million won and 2% of

the sales amount.

<관련 기사> 전자신문 14-02-19

▣ Prof. Jong-lam Lee, Scientist/Engineer of the Month (February)

 Prof. Jong-lam Lee of POSTECH Materials Science and Engineering was selected on the 5th as the February recipient of Scientist/Engineer of the Month awarded by Ministry of Science, ICT and Future Planning, National Research Foundation of Korea and Seoul Economics Daily
 By this award, Prof. Lee has achieved recognition for developing a technology to manufacture the metal substrate with nanometer scale surface roughness, which can be used for flexible display substrate. The technology is known to enable mass production of metal substrates by fixing the problem that the surface of a metal gets rough as the metal is thinned. The flexible substrate market is estimated to reach 55 trillion won by 2018.  
 The Scientist/Engineer of the Month is an award for those who contribute to the advancement of science and engineering with their excellent research outcome. With the purpose of boosting morale of scientists and engineers and promote the importance of science and engineering among the public, the award has been presented to one person every month since April 1997 with Minister’s award and prize money.

▣ Sang-ho Oh, Reversible Deformation of Gold Nanowire as thin as a three hundredth of a hair

Prof. Sang-ho Oh of POSTECH Reveals Rubber-like Characteristic of Gold Nanowire

 Gold nanowires as thin as a three hundredth of a hair has been revealed to be as flexible as a rubber band.
 Such resilience of gold nanowire is expected to be used for a variety of purposes including ultra fine energy storage devices, shape memory devices and sensors.
 Prof. Sang Ho Oh of POSTECH Materials Science and Engineering has found that gold nanowires have reversible cyclic deformation (repetitive appearance of reversible plastic deformation).
 Prof Oh’s research, supported as part of Middle-level Researcher Support Program sponsored by Ministry of Science, ICT and Future Planning and National Research Foundation of Korea, was conducted in collaboration with KAIST, Erlangen University of Germany, Max Planck Institute and Leoben University of Austria. The paper was recently published in Nature Communications.
 Gold nanowires have attracted interest because of its ultra high mechanical strength theoretically possible, but the research was available only depending on computer simulation due to experimental limitations.
 The key was to track how nanowires are deformed real-time to find out why they are hard to be shaped while getting stronger as being thinned.
 The research team lengthened and compressed gold nanowires three to four times, and observed real-time that nanowires became elongated by 40% and returned to the original length.
 As reversible deformation of gold nanowires has been verified by experiment, not just predicted from simulation, the characteristic is expected to be applied to nano devices including ultra fine sensors, shape memory devices and energy storage devices.
 Prof. Oh said that he will continue his research on real-time analysis on the performance and properties of nano materials based on the discovery that nano-size metal may allow the amount of deformation by 40% repetitively.


Reversible cyclic deformation mechanism of gold nanowires by twinning–detwinning transition evidenced from in situ TEM

Nature Comm, 5, 4033 (2014) (IF: 10.015)


▣ Prof. Sei-kwang Hahn, Cancer Treatment Using Light

POSTECH Research Team Develops Cancer Treatment Using Light

 The joint research team of POSTECH and Harvard Medical School developed a completely new photothermal treatment for cancer based on nanographene oxide-hyaluronic acid conjugate.

 Prof. Sei Kwang Hahn and Ph.D. candidate Ho-sang Jung of POSTECH Materials Science and Engineering in collaboration with Wellman Center for Photomedicine of Harvard Medical School have succeeded in developing a new technology to kill cancer tissue using photothermal method, that is to inject a nano-sized graphene-hyaluronic acid conjugate into animal subjects suffering from cancer and use a near-infrared laser. 
 This new technology can exclusively target cancer tissue and is expected to drastically reduce side effects of anticancer drug administration affecting the entire body.
 The research is published in the prestigious ACS Nano, the January 3 online issue.
 Prof. Hahn’s team have published a total of 30 papers on development of biomaterials for nanomedicine in world-class academic journals including Nature Photonics and Advanced Materials and finished applying and registering 30 domestic and international patents for the last three years.
 The research was supported by National Research Foundation of Korea.
 Prof. Hahn said, “I have again succeeded in developing a cancer treatment after finding a diabetes cure using light in 2013, and I will do my best to develop cures using light for a number of incurable diseases in continued collaboration with Harvard Medical School.”


Nanographene Oxide-Hyaluronic  Acid Conjugate for Photothermal Ablation Therapy of Skin Cancer

ACS Nano, 8, 1, 260–268 (2014) (IF: 12.062)