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Jaehoon Jeong,Sungho Nam,Hwajeong Kim,Youngkyoo Kim IEEE 2014 IEEE journal of selected topics in quantum electro Vol.20 No.6
<P>We report inverted-type organic photodetectors with zinc oxide (ZnO) electron-collecting buffer layers and polymer:fullerene bulk heterojunction active layers. A visible light was detected by the inverted organic photodetectors when a background UV light was ON, whereas no photocurrent signal was measured for visible lights without the background UV light. Interestingly, UV lights solely were successfully detected without any surrounding UV light. The present devices exhibited fast and stable photo-responses under modulated or continuous UV-visible lights.</P>
Jaehoon Jeong,Hanbit Hyun,Heajin Park,Byung Sun Kim,Hye Seong Hwang,Byung Tae Park,Ha Hyung Kim 한국당과학회 2013 한국당과학회 학술대회 Vol.2013 No.1
The carbohydrates in natural plant materials obtained from roots, leaves, stem barks, and seed were investigated. All of the plant materials were dried, and their constituents were isolated by room temperature-water or hot-water extraction. Ethanol precipitation was also used to produce solutions containing the constituents for analysis. Mono- and disaccharides were separated using a high-pH anion-exchange chromatography system equipped with a CarboPac PA10 column and an AminoTrap column working at an isocratic NaOH concentration of 20 mM and at a flow rate of 0.5 ml/min at room temperature for 40 min. Carbohydrates were detected by a pulsed amperometric detector. The concentration of each carbohydrate was quantified by calculation from a calibration curve constructed using a standard mixture containing twofold dilutions from 1,600 pmol of each carbohydrate. Enzymatic deglycosylation of the plant extracts was also performed. Namely, each sample was incubated in the presence of 40 μM trypsin and 40 μM chymotrypsin in 10 mM Tris-HCl buffer (pH 8.0) at 37°C for 18 h. N-glycans were then released from glycopeptides after reaction with 0.1 mU of glycoamidaseA in citrate-phosphate buffer (pH 5.0) at 37°C for 18h. Peptides and salts were removed using graphitized carbon cartridges. The released glycans were lyophilized and stored at –20°C. The N-glycan structures were analyzed by normal-phase high-performance liquid chromatography of 2-aminobenzamide-labeled glycans in combination with exoglycosidase digestion, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The functions of the identified and isolated chemical constituents were also investigated.
Jeong Jaehoon,Bisht Himani,Ryu Sanghyun,Hong Daewha 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.6
Polymer brush surfaces have various interesting applications; however, to facilitate their formation on surfaces, an initiator ad-layer is required in advance. In this study, we developed a versatile initiator film that simultaneously meets the standards of uniformity and stability using a simple surface coating strategy. In brief, co-deposition of dopamine and polyethyleneimine formed a polydopamine/polyethyleneimine (pDP) film, which was then acylated with external α-bromoisobutyryl bromide. The resultant initiator film, pDP functionalized with initiator (pDPI), showed a homogeneous surface morphology and resisted harsh solvent conditions. The subsequent surface-initiated polymerization from the developed pDPI initiator layer also formed a thick polymer brush.
Jeong, Jaehoon,Essafi, Makram,Lee, Chulyeon,Haoues, Meriam,Diouani, Mohamed Fethi,Kim, Hwajeong,Kim, Youngkyoo Elsevier 2018 Journal of hazardous materials Vol.355 No.-
<P><B>Abstract</B></P> <P>Here we report that superoxide, one of the hazardous reactive oxygen species (ROS), can be quickly detected by flexible organic field-effect transistors (OFETs) with the polyphenol-embedded conjugated polymer micro-channels. Rutin, one of the abundant polyphenols found in a variety of plants, was employed as a sensing molecule and embedded in the poly(3-hexylthiophene) (P3HT) matrix. The rutin-embedded P3HT layers showed randomly distributed micro-domains, which became bigger as the rutin content increased. The best transistor performance was achieved at the rutin content of 10 wt%, while the OFETs exhibited proper and controllable transistor performances even in the phosphate buffer solutions. The sensing test revealed that the present OFET sensors could stably detect superoxide using very small amount (<10 μl) of samples at extremely low concentrations (500 pM), while they exhibited outstanding stability and durability upon repeated detection and storage-reuse tests. Finally, the present flexible OFET sensors could deliver confident sensing results for the detection of superoxide generated from the mouse RAW264.7 macrophages.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Flexible OFETs with the polyphenol-embedded conjugated polymers are fabricated. </LI> <LI> Rutin-based OFETs can quickly detect superoxide at extremely low concentrations. </LI> <LI> The OFET sensors exhibit outstanding durability upon repeated and reuse tests. </LI> <LI> Superoxide generated in the macrophages can be effectively detected by the OFETs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>