2022 충남대학교 소재화학연구소 국제학술대회 

2022 

International Symposium 

on Materials Chemistry

October 13th (Thursday) 2022

Natural Science Building 4 (W11- 2), Room: 109

주관 : 충남대학교 소재화학연구소

Research Institute of Materials Chemistry, 

Chungnam National University 

후원 : 충남대학교 화학물질특성분석 핵심연구지원센터

CNU Chemistry Core Facility

< Program > 

13:30–14:00  Registration

14:00–14:10  Opening Remarks : 

Prof. Sung Hi Choi (Dean, CNS )

Prof. Jeongkwon Kim (Director, RIMC, CNU)

Session I

Chairperson : Prof. Chang Woo Myung

(Chungnam National University, Korea)

14:10- 14:40  Dr. Hyojik Yang

(Department of Microbial Pathogenesis, University of Maryland, Baltimore, Maryland, USA)

"Culture- free analysis of Gram- negative bacterial lipid A by Mass Spectrometry"

14:40- 15:10  Prof. Maryam Adeli 

(Department of Biochemistry, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran)

"Mesenchymal syem cells and their exosome: sources, properties and potential application in regenerative medicine"

15:10- 15:40  Prof. Denver Walitang

(College of Agriculture, Fisheries and Forestry, Romblon State University, Romblon, Philippines)

"'Proteome of ACC deaminase producing bacteria- mediated salt tolerance in rice(Oryza sativa L.)"

15:40 -  16:00   Coffee Break

Session II

Chairperson : Prof. Ji- Hyun Cha

(Chungnam National University, Korea)

16:00- 16:30  Prof. Lemma Teshome 

(Department of Applied Chemistry, Adama Science and Technology University, Adama, Ethiopia)

"Ni- Based Ultrathin Nanostructures for Overall Electrochemical Water Splitting"

16:30- 17:00  Prof. Dong Hee Son 

(Department of Chemistry, Texas A&M University, USA)

"Excitons and hot electrons from strongly quantum confined perovskite nanostructures"

17:00- 17:30  Prof. Liudmila L. Larina 

(Department of Solar Photovoltaics, Institute of Biochemical Physics, Moscow, Russia)

"Interface engineering in Cd- free Cu(In,Ga)Se2 solar cells"

17:30 -  18:00   Closing & Photo Time 

18:00 – 20:00    Dinner

Culture- free analysis of Gram- negative bacterial lipid A by Mass Spectrometry

Hyojik Yang

Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland 21201, United States

Gram- negative bacteria causes a variety of human infectious diseases, including urinary tract infections, pneumonia, and bloodstream infections (sepsis).  Thus, understanding the pathogenic microbial molecules responsible for such maladies is important. One well- known molecule present in the outer membrane of Gram- negative bacteria is lipopolysaccharide (LPS). LPS consists of three structural elements: O- antigen, the most exterior region and composed of repeating saccharide units, followed by a carbohydrate core region, and anchored in the membrane by lipid A. While the translational uses of lipid A extracted from cultured bacteria are promising, in vitro growth on solid or in liquid media has the potential to change lipid A phenotype and, thus, may not best represent its physiological state during infection. Here, we developed a method to directly detect and analyze structure of the Gram- negative bacterial virulence factor lipid A derived from lipopolysaccharide (LPS) by coupling acid hydrolysis with matrix- assisted laser desorption/ionization mass spectrometry imaging (MALDI- MSI). We called it LPS- to- Lipid A- MSI (LLA- MSI, Anal. Chem. 2020, 92, 20, 13667–13671). By our limited knowledge, this is first report to visualize lipid A on genuinely bacterial infection tissue via label- free manner. We also prove that LLA- MSI is an useful tool to determine dominance composition lipid A in- vivo. Moreover, we are able to conduct on- tissue MS/MS of lipid A ions for structural analysis. Another example of culture- free analysis of lipid A, we describe an innovative use for the recently reported fast lipid analysis technique (FLAT) that allows for the generation of MALDI tandem mass spectrometry data suitable for lipid A structure analysis directly from a single Gram- negative bacterial colony. We refer to this tandem MS version of FLAT as FLATⁿ.  We also show that FLATⁿ can be used to analyze lipid A structures taken directly from a complex biological clinical sample without the need for ex vivo growth. From a urine sample from a patient with an E. coli infection, FLATⁿ identified the organism and demonstrated that this clinical isolate carried the mobile colistin resistance- 1 gene (mcr- 1) that results in the addition of a phosphoethanolamine moiety and subsequently resistance to the antimicrobial, colistin (polymyxin E). Moreover, FLATⁿ allowed for the determination of the existence of a structural isomer in E. coli lipid A that had either a 1-  or 4′- phosphate group modification by phosphoethanolamine generated by a change of bacterial culture conditions.

Mesenchymal stem cells and their exosome: sources, properties and potential application in regenerative medicine

Maryam Adelipour^1,2

1^{Department of Chemistry, Chungnam National University, Daejeon, Republic of Korea}

 2^{Department of Biochemistry, Ahvaz Jundishapur University of Medical Science, Ahvaz,}

Mesenchymal stem cells (MSCs) have been extensively investigated for the treatment of various diseases. Currently, they have an important role in regenerative medicine and many potential applications. Recent investigations revealed that their therapeutic effect is largely mediated by the secretion of paracrine factors including exosomes. The aim of this review is to provide an overview, discussing the application of mesenchymal stem cells and their secreted exosomes in regenerative medicine. MSCs are multipotent progenitor cells with the potential to differentiate into specialized cell types. The main sources of MSCs are bone marrow, adipose tissue (ASC), cord blood, and Wharton's jelly of the umbilical cord. MSCs can migrate to injured sites, engraft, and differentiate into end- stage functional cells, thus repairing the injured tissue. The therapeutic potentials of MSCs are mainly attributed to two aspects: first, replacement of the damaged tissue by differentiating into various cell lineages, and the second, regulation of immune responses by immunomodulatory function. The immunomodulatory modes of MSCs include paracrine activity, cell–cell contact and interaction, mitochondrial transfer, and release of extracellular vesicles. Recently, a growing body of clinical trials worldwide has used MSCs to treat various diseases, including bone/cartilage repair, diabetes, cardiovascular diseases, immune- related, and neurological disorders. However, mechanisms underlying the protective effects of MSCs still require further elucidation. Besides, therapeutic effect of exosomes derived MSCs has fascinated scientist in recent years. Exosomes reflect biophysical features of MSCs and are considered more effective than MSCs themselves. Alternative approaches based on MSC- derived exosomes can offer appreciable promise in overcoming the limitations and practical challenges observed in cell- based therapy. There are several advantages of exosomes including the ability to combine with existing, newly developed compositions or methods and designed as carrier particles, the ability to be engineered to target specific cells or tissues, the ability to home to the lesion tissue. Compared with cell therapy, exosome therapy is safer and has no potential tumorigenicity of stem cells. However, the use of exosomes in several therapies is remained controversial, because a little is known about the function of numerous proteins, RNAs, lipids, and metabolic enzymes which have been identified in exosomes. Overall, although the potential of MSCs and exosomes derived from MSCs in regenerative medicine and tissue engineering is highly promising, further investigations are needed to discover the exact mechanisms by which MSCs and exosomes affect other cell.

Proteome of ACC deaminase producing bacteria- mediated tolerance salt tolerance in rice (Oryza sativa L.)

D. I. Walitang^1,2

1^{College of Agriculture, Fisheries and Forestry, Romblon State University, Romblon, Philippines}

2^{Dept. of Environmental and Biological Chemistry, Chungbuk National University, Cheongju, Korea}

Characteristic proteins in plants revealed through proteomics analysis elucidate mechanisms of protein- based ACC deaminase producing bacteria- mediated salt tolerance. The current study evaluated changes in the proteome of rice (Oryza sativa L.) mediated by inoculation with an ACC deaminase producing bacteria under normal and salt stress conditions. Overall, salt stress caused significant reduction in chlorophyll a, b, and carotenoids but significant improvement in pigment contents were observed upon inoculation of Methylobacterium oryzae CBMB20 regardless of stress conditions. Proteomics analysis showed 41 and 35, 36 and 15, and 14 and 19 upregulated and downregulated differentially abundant proteins (DAPS) in non- inoculated salt- stressed plants, CBMB20 inoculated plants under normal, and CBMB20 inoculated plants under salt stress conditions, respectively. Under normal conditions, CBMB inoculation increased abundance of proteins related to plant growth and development. On the other hand, salt stress resulted in the decreased abundance of proteins related to photosynthesis and enhanced abundance related to ethylene emissions and programmed cell death. The effects of salt stress were countered by CBMB20 inoculation resulting in the increased abundance of antioxidant proteins, RuBisCo, and ribosomal proteins and decreased abundance of proteins related to ethylene biosynthesis. Rice is affected by salt stress in terms of photosynthesis and ethylene induced programmed cell death but ACC deaminase producing Methylobacterium oryzae CBMB20 attenuates salt- induced stress by improving photosynthesis, reactive oxygen species scavenging and modulating ethylene biosynthesis in plants

Ni- Based Ultrathin Nanostructures for Overall Electrochemical Water Splitting

Lemma Teshome Tufa^a,b

a^{Department of Applied Chemistry, Adama Science and Technology University, P.O.Box 1888, Adama Ethiopia}

b^{Research Institute of Materials Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea}

Hydrogen produced by electrochemical water splitting is considered a sustainable fuel source, an ideal way to solve the energy problem and its environmental challenges. However, industrial production of hydrogen from water splitting is mainly hindered by sluggish kinetics of oxygen evolution reactions (OER) at the anode and hydrogen evolution reaction (HER) at the cathode in alkaline solution due to the difficulty in forming binding protons. Thus, the construction of a highly active and cost- effective catalyst with abundant oxygen vacancies is critical to enhancing reaction efficiency and decreasing required overpotential. Due to earth- abundance and electrocatalytic activities, Ni- based ultrathin Nanostructures (Ni- utNSs) have attracted immense attention for overall water splitting. Herein, we have presented a complete summary of Ni- utNSs' recent advancement for overall electrochemical water splitting. Detailed information on Ni- utNSs is presented, including their properties and crystal structure, manufacturing techniques, as well as in- situ and ex- situ characterization, and computer modeling. This work can help researchers understand the Ni- utNS catalyst's recent progress and get insight into the rational design of Ni- utNS catalysts with high electrocatalytic activity

Keywords: Ni- based Nanostructures, Ultrathin, Water splitting, Oxygen vacancy

Excitons and hot electrons from strongly quantum confined perovskite nanocrystals

Dong Hee Son

Department of Chemistry

Texas A&M University, TX, College Station, USA

Perovskite quantum dots (QDs) are emerging as an excellent source of photons and charge carriers for photonic and photovoltaic applications that are superior to many existing semiconductor quantum dots. In this presentation, I will discuss the energetics and relaxation dynamics of bright and dark excitons in strongly quantum confined cesium lead halide perovskite QDs that dictate various photophysical properties in this new family of QDs. For this purpose, we prepared the QDs with varying degree of confinement in non- interacting ensemble and electronically coupled arrays of QDs as well as in the magnetically doped non- interacting QDs. The effect of confinement- enhanced electron- hole exchange interaction in strongly confined QDs on bright- dark level splitting and the rates of bright and dark exciton emission were studied via time- resolved photoluminescence (PL) of exciton in the non- interacting ensemble. The effect of electronic coupling in the 2- dimensional QD arrays altering the electron- hole exchange interaction and the exciton fine structure was studied via the time- resolved exciton PL obtained at cryogenic temperatures. In addition, doping of strongly confined perovskite nanocrystals open a photophysical pathway that that enables the generation of energetic hot electron via exciton- to- hot electron upconversion under weak cw excitation, which enables the photoemission of hot electrons above the vacuum level. The implication of these hot electrons for photocatalysis will also be discussed.

Interface Engineering in Cd- free Cu(In,Ga)Se₂ 

solar cells

Liudmila Larina

Institute of Biochemical Physics, Russian Academy of Sciences Moscow, Russia

Chungnam National University, Chemical Engineering and Applied Chemistry Department Daejeon, Republic of Korea 

Cu(In,Ga)Se₂ (CIGS) thin film solar cells are expected to play a leading role in the photovoltaic market due to their high efficiency of over 23%. The electronic properties of the CIGS absorber and buffer layer influence the solar cell efficiency. In particular, the band alignment strongly affects the charge transfer across the buffer/CIGS interface. So, the key issue in the fabrication of high- efficiency Cd- free CIGS devices is the formation of a high- quality buffer/CIGS interface. The state- of- the- art structure of a CIGS solar cell is ZnO/CdS/CIGS, where CdS is regarded as the best buffer material for high efficiency. The development of a wide- bandgap Cd- free buffer is currently the most pivotal topic in CIGS PV technology. The challenge is addressed to replace the toxic Cd- based buffer and is motivated by concerns over environmental safety. The key issue in the fabrication of high- efficiency Cd- free CIGS devices is a high- quality buffer/CIGS interface. 

This study is aimed to quantify the band discontinuities at the ZnS/CIGS and Zn_{1- x}Mg_xO/CIGS interfaces using XPS and UPS depth profile analysis. ZnS and Zn_{1- x}Mg_xO buffers were grown by chemical bath and atomic layer depositions, respectively. The discontinuity of 2.0 eV in the valence band edge at the ZnS/CIGS interface was directly determined yielding a spike conduction band alignment of 0.25 eV. The VBO at the Zn_{1- x}Mg_xO/CIGS interface was found to be 2.55 eV after considering a small band bending in the interface region. The bandgap energy of Zn_{1- x}Mg_xO film increased from 3.25 to 3.76 eV as the Mg content increased from 0 to 25%. The combination of the VBO and the band energy of Zn_{1- x}Mg_xO films results in the flat and cliff (- 0.23eV) conduction band alignments at the Zn_0.8Mg_0.2O/CIGS and Zn_0.9Mg_0.1O/CIGS interfaces, respectively. The experimental results suggest that the band energy of Zn_{1- x}Mg_xO films is the main factor that determines the CBO at the Zn_{1- x}Mg_xO/CIGS interface.

The study is the first to apply UPS depth profile analysis to assess the valence band structures of the ZnS/CIGS and Zn_{1- x}Mg_xO/CIGS interfaces, as they exist in real devices. Our results provide information for the design optimization of the optoelectronic properties of the ZnS/CIGS and Zn_{1- x}Mg_xO/CIGS interfaces. To enhance the electron injection from the absorber to the ZnS buffer further lowering of the energy barrier is required. For this purpose, the band energy of ZnS should be reduced by controlling the crystal structure and composition or its Fermi level should be upward shifted by appropriate doping.

The experimental results can be used for the optimization of the alignment of energy levels at the ZnS/CIGS and Zn_{1- x}Mg_xO/CIGS interfaces to increase the device efficiency. The quantification of band discontinuities contributes to the knowledge base of PV materials