Anisotropic etching characteristics of single crystal silicon by KOH and KOH-IPA Solutions

조남인,천인호 韓國眞空學會 2002 Applied Science and Convergence Technology Vol.11 No.4

이방성 습식 식각기술을 이용하여 멤버레인을 제작하기 위하여 KOH 용액 및 KOH-IPA 혼합용액을 사용하여 단결정 실리콘 기판을 식각하였다. 단결정 실리콘의 식각속도는 식각 용액의 온도와 농도에 좌우되었으며, 식각 용액의 농도에 따라 식각 형태와 패턴 형성 방향이 달라짐도 관찰되었다. 식각을 위한 표면패턴은 실리콘웨이퍼의 primary flat에 45°로 기울여 형성되었으며 KOH 의 농도가 20 wt%로 유지되었을 때, 식각 용액의 온도 80℃이상에서는 U-groove, 80℃ 이하의 온도에서는 V-groove 식각 형태가 형성되었다. 각 면에 대한 식각속도 차이에 의해서 생기는 hillock은 온도와 농도가 높아짐에 따라 현저하게 줄어들었다. For a formation of membrane structures, single crystal silicon wafers have been anisotropically etched with solutions of KOH and KOH-IPA. The etching rate was observed to-be strongly dependent upon tie etchant temperature and concentration. Mask patterns for the etching experiment was aligned to incline 45 on the primary flat of the silicon wafer. The different etching characteristics were observed according to pattern directions and etchant concentration. When the KOH concentration was fixed to 20 wt%, the U-groove etching shape was observed for the etching temperature of above 80℃, and V-groove shapes observed at below 80℃. Hillocks, which were generated at the etched silicon surfaces, has been deceased as the increasing of the etchant temperature and concentration.

Fabrication and design equation of film-type large-scale interdigitated supercapacitor chips.

Nam, Inho,Kim, Gil-Pyo,Park, Soomin,Park, Junsu,Kim, Nam Dong,Yi, Jongheop RSC Pub 2012 Nanoscale Vol.4 No.23

<P>We report large-scale interdigitated supercapacitor chips based on pseudo-capacitive metal oxide electrodes. A novel method is presented, which provides a powerful fabrication technology of interdigitated supercapacitors operated by a pseudo-capacitive reaction. Also, we empirically develop an equation that describes the relationship between capacitance, mass, and sweep rate in an actual supercapacitor system.</P>

[Review] Quantum Dots For Killing Multidrug Resistant Bacteria via Photodynamic Therapy

Inho NAM,Hyung Joon CHA 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.4

Colorimetric oxygen sensor based on nano-sized black TiO2 catalysts: DFT modeling and experiments

Nam, Inho,Son, Hyunwoo,Choi, Youngbo Elsevier 2018 Molecular catalysis Vol.459 No.-

<P>There are the imperious demands for novel oxygen (O-2) sensors in cutting-edge biochemical technologies and industrial hygiene. Here, we develop a colorimetric O-2 sensor based on a spherical nano-sized reduced TiO2 (TiO2 - x) catalyst, which resolves the critical bottlenecks of conventional systems. The sensing mechanism of our O-2 sensors relies on two characteristics which are proven by simulations based on density functional theory (DFT) calculations. First, nano-TiO2-x, in the partially reduced form, shows a rapid, reversible O-2 uptake at room temperature. Second, the partially reduced form of nano-TiO2-x called black TiO2, shows a change in the lightness of color. Owing to these characteristics, the developed sensor it is well-suited for use at ambient temperature/pressure in the absence of a reference gas, in contrast with the conventional system. Also, it allows long-term operations and it can withstand degradation because the former comprises solid-state inorganic compounds.</P>

All-solid-state, origami-type foldable supercapacitor chips with integrated series circuit analogues

Nam, Inho,Kim, Gil-Pyo,Park, Soomin,Han, Jeong Woo,Yi, Jongheop The Royal Society of Chemistry 2014 ENERGY AND ENVIRONMENTAL SCIENCE Vol.7 No.3

<P>Patterning-assembly technology for energy storage systems can be a breakthrough for physicochemically limited energy storage systems. In this study, a concept of design with experimental proof is provided for an all-solid-state origami-type foldable supercapacitor by a novel patterning approach. The proposed system is composed of periodically assembled isolated electrodes (IEs) and sectionalized ion transferring paper (SITP), which are key factors for the densely packed series circuit analogues in the single system. The system shows a linear relationship between the potential window and the number of IEs, which does not have any limited asymptotic line. This system could increase energy and power simultaneously, which was conventionally not possible. Also, its folding characteristics accommodate highly stable stretching. These characteristics are proven by simulations based on <I>ab-initio</I> calculations and the finite-element method.</P> <P>Graphic Abstract</P><P>Origami-type stretchable supercapacitors permit energy and power to be simultaneously increased and accommodate stable stretching with integrated series circuit analogues. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3ee43175d'> </P>

Abiotic production of sugar phosphates and uridine ribonucleoside in aqueous microdroplets

Nam, Inho,Lee, Jae Kyoo,Nam, Hong Gil,Zare, Richard N. National Academy of Sciences 2017 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.114 No.47

<▼1><P><B>Significance</B></P><P>Phosphorylation is essential for life. Phosphorylated molecules play diverse functions in cells, including metabolic (e.g., sugar phosphates), structural (e.g., phospholipids), and instructional (e.g., RNA and DNA). In nature, the phosphorylation of sugars via condensation is thermodynamically and kinetically unfavorable in bulk solution. Thus, a key question arising within prebiotic chemistry concerning the origin of life is, “How was phosphorus incorporated into the biological world?” Here, we show that sugar phosphates and a ribonucleoside form spontaneously in microdroplets, without enzymes or an external energy source. Sugar phosphorylation in microdroplets has a lower entropic cost than in bulk solution. Therefore, thermodynamic obstacles of prebiotic condensation reactions can be circumvented in microdroplets.</P></▼1><▼2><P>Phosphorylation is an essential chemical reaction for life. This reaction generates fundamental cell components, including building blocks for RNA and DNA, phospholipids for cell walls, and adenosine triphosphate (ATP) for energy storage. However, phosphorylation reactions are thermodynamically unfavorable in solution. Consequently, a long-standing question in prebiotic chemistry is how abiotic phosphorylation occurs in biological compounds. We find that the phosphorylation of various sugars to form sugar-1-phosphates can proceed spontaneously in aqueous microdroplets containing a simple mixture of sugars and phosphoric acid. The yield for <SMALL>D</SMALL>-ribose-1-phosphate reached over 6% at room temperature, giving a Δ<I>G</I> value of −1.1 kcal/mol, much lower than the +5.4 kcal/mol for the reaction in bulk solution. The temperature dependence of the product yield for the phosphorylation in microdroplets revealed a negative enthalpy change (Δ<I>H</I> = −0.9 kcal/mol) and a negligible change of entropy (Δ<I>S</I> = 0.0007 kcal/mol·K). Thus, the spontaneous phosphorylation reaction in microdroplets occurred by overcoming the entropic hurdle of the reaction encountered in bulk solution. Moreover, uridine, a pyrimidine ribonucleoside, is generated in aqueous microdroplets containing <SMALL>D</SMALL>-ribose, phosphoric acid, and uracil, which suggests the possibility that microdroplets could serve as a prebiotic synthetic pathway for ribonucleosides.</P></▼2>

Amorphous Mn Oxide-Ordered Mesoporous Carbon Hybrids as a High Performance Electrode Material for Supercapacitors

Nam, Inho,Kim, Nam Dong,Kim, Gil-Pyo,Park, Junsu,Yi, Jongheop American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.7

<P>A supercapacitor has the advantages of both the conventional capacitors and the rechargeable batteries. Mn oxide is generally recognized one of the potential materials that can be used for a supercapacitor, but its low conductivity is a limiting factor for electrode materials. In this study, a hybrid of amorphous Mn oxide (AMO) and ordered mesoporous carbon (OMC) was prepared and characterized using X-ray diffraction, transmission electron microscopy, N2/77 K sorption techniques, and electrochemical analyses. The findings indicate that the electrochemical activities of Mn oxide were facilitated when it was in the hybrid state because OMC acted as a pathway for both the electrolyte ions and the electrons due to the characteristics of the ordered mesoporous structure. The ordered mesoporous structure of OMC was well maintained even after hybridization with amorphous Mn oxide. The electrochemical-activity tests revealed that the AMO/OMC hybrid had a higher specific capacitance and conductivity than pure Mn oxide. In the case where the Mn/C weight ratio was 0.75, the composite showed a high capacitance of 153 F/g, which was much higher than that for pure Mn oxide, due to the structural effects of OMC.</P>

Abiotic synthesis of purine and pyrimidine ribonucleosides in aqueous microdroplets

Nam, Inho,Nam, Hong Gil,Zare, Richard N. National Academy of Sciences 2018 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.115 No.1

<▼1><P><B>Significance</B></P><P>Discovery of an improved prebiotic method for the synthesis of ribonucleosides provides support to theories that posit a central role for RNA in the origin of life. It has been assumed that ribonucleosides arose through an abiotic process in which ribose and nucleobases became conjoined, but the direct condensation of nucleobases with ribose to give ribonucleosides in bulk solution is thermodynamically uphill. We show a general synthetic path for ribonucleosides, both purine and pyrimidine bases, using an abiotic salvage pathway in a microdroplet environment with divalent magnesium ion (Mg<SUP>2+</SUP>) as a catalyst. Purine and pyrimidine ribonucleosides are formed simultaneously under the same conditions, which suggests a possible scenario for the spontaneous production of random ribonucleosides necessary to generate various types of primitive RNA.</P></▼1><▼2><P>Aqueous microdroplets (<1.3 µm in diameter on average) containing 15 mM <SMALL>D</SMALL>-ribose, 15 mM phosphoric acid, and 5 mM of a nucleobase (uracil, adenine, cytosine, or hypoxanthine) are electrosprayed from a capillary at +5 kV into a mass spectrometer at room temperature and 1 atm pressure with 3 mM divalent magnesium ion (Mg<SUP>2+</SUP>) as a catalyst. Mass spectra show the formation of ribonucleosides that comprise a four-letter alphabet of RNA with a yield of 2.5% of uridine (U), 2.5% of adenosine (A), 0.7% of cytidine (C), and 1.7% of inosine (I) during the flight time of ∼50 µs. In the case of uridine, no catalyst is required. An aqueous solution containing guanine cannot be generated under the same conditions given the extreme insolubility of guanine in water. However, inosine can base pair with cytidine and thus substitute for guanosine. Thus, a full set of ribonucleosides to generate the purine–pyrimidine base pairs A-U and I-C are spontaneously generated in aqueous microdroplets under similar mild conditions.</P></▼2>

NH3-activated polyaniline for use as a high performance electrode material in supercapacitors

Kim, Nam Dong,Kim, So Jeong,Kim, Gil-Pyo,Nam, Inho,Yun, Hyeong Jin,Kim, Pil,Yi, Jongheop Elsevier 2012 ELECTROCHIMICA ACTA Vol.78 No.-

Tuning the oxidation states of nanostructured amorphous Mn oxides for electrochemical applications

Kim, Nam Dong,Yun, Hyeong Jin,Nam, Inho,Yi, Jongheop Royal Society of Chemistry 2011 Journal of materials chemistry Vol.21 No.40

<P>A simple precipitation method is proposed in order to maximize the electrochemical performance of nanostructured amorphous Mn oxide <I>via</I> the tuning of the oxidation states using various <I>n</I>-alcohol solvents with different lengths of alkyl chain.</P> <P>Graphic Abstract</P><P>We demonstrate a facile method for controlling the oxidation state and chemical properties of nanostructured amorphous Mn oxide by using organic solvent based precipitation. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1jm12890f'> </P>