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RISS 인기검색어
- 검색키워드
- 저자 : Dowben, Peter A. (검색결과 5 건)
- 무료
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Cyclodextrin-carbon nanotube composites for fluorescent detection of cholesterol
Gilbert, Simeon,Jeong, Hae Kyung,Dowben, P.A. Elsevier 2017 Chemical physics letters Vol.687 No.-
<P>The efficiency of cyclodextrin-carbon nanotube composites (CD-CNT) for cholesterol detection was investigated using their fluorescent yields in the presence of rhodamine 6G (R6G). The CD-CNT composites using alpha-, beta- and gamma-cyclodextrin (x-CD) all showed strong fluorescent responses to cholesterol when in the presence of R6G. The alpha-CD based composites, however, exhibit more dramatic fluorescent changes in response to cholesterol, over a wider range of cholesterol concentrations, and also display the highest binding constant of 2.98 x 10(5) M-1 with cholesterol. The effectiveness of these fluorescent responses for the detection of cholesterol depends primarily on the concentration and cavity size of the CD. (C) 2017 Elsevier B.V. All rights reserved.</P>
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Jeong, H.K.,Zhang, X.,Dowben, P.A. North Holland ; Elsevier Science Ltd 2013 Chemical physics letters Vol.572 No.-
The electronic structure of poly(sodium 4-styrenesulfonate) intercalated graphite oxide (PSSGO) in the vicinity of the Fermi level was investigated using ultraviolet photoemission and inverse photoemission spectroscopies. The conduction band density of states for PSSGO is similar to that of graphite, indicating facile electron transfer from electrolyte ions to the PSSGO electrode in energy storage device applications. The in situ band gap of 1.9eV observed was smaller than that of graphite oxide by 0.4eV, helping to explain the high performance of electric double layer capacitor of PSSGO compared with graphite oxide.
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Evidence of band bending and surface Fermi level pinning in graphite oxide
Jeong, H.K.,Hong, L.,Zhang, X.,Vega, E.,Dowben, P.A. Pergamon Press ; Elsevier Science Ltd 2013 Carbon Vol.57 No.-
We present the electronic structure of graphite oxide in the vicinity of the Fermi level measured using ultraviolet photoemission and inverse photoemission spectroscopies and compare it with X-ray absorption spectra. The expected p-type behavior of graphite oxide is not observed at the surface and the presence of band bending is invoked. The observed electronic structure of graphite oxide exhibited an n-type semiconducting band structure with a band gap of 2.3+/-0.4eV. An oxygen related state, at 0.8eV above Fermi level, and the suppression of the unoccupied carbon weighted states at the conduction band minimum suggests that the oxygen vacancies at the surface of graphite oxide contribute to the n-type semiconducting electronic structure of the surface.
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Aryal, Krishna Prasad,Ekanayaka, Thilini K.,Gilbert, Simeon,Dowben, Peter A.,Jeong, Hae Kyung Elsevier 2020 Chemical physics letters Vol.738 No.-
<P><B>Abstract</B></P> <P>In the present study, carbon nanotube (CNT), thermally reduced graphite oxide (TRGO), and CNT-TRGO were functionalized with p-sulfonatocalix[4]arene (SC4) and then investigated for fluorescent detection of cholesterol in the presence of rhodamine 6G (R6G). All of the composite samples show effective quenching of R6G fluorescent intensity without cholesterol, but the fluorescence intensity significantly increases with the addition of cholesterol. The results indicate a strong interaction between SC4 composites and cholesterol rather than between the SC4 composites and R6G, increasing R6G fluorescence intensity in the presence of cholesterol due to the release of R6G from the SC4 composites. Formation of the complex, made of the SC4 composite plus the cholesterol, enables the detection of cholesterol in the wide range of cholesterol concentration up to 109 µM. The binding constant between SC4 and cholesterol has been calculated, indicating that the SC4 composites display the maximum binding constant of 1.9 × 10<SUP>4</SUP> M<SUP>−1</SUP> with cholesterol.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Demonstration of water soluble calixarene derivatives in the fluorescent detection. </LI> <LI> Successful functionalization of p-sulfonatocalix[4]arene (SC4) on carbon material. </LI> <LI> Fluorescent detection of cholesterol up to 109 μM. </LI> <LI> Maximum binding constant of 1.9 × 104 M<SUP>−1</SUP> between cholesterol and SC4 composites. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Methoxy Formation Induced Defects on MoS<sub>2</sub>
Evans, Prescott E.,Jeong, Hae Kyung,Hooshmand, Zahra,Le, Duy,Rawal, Takat B.,Naghibi Alvillar, Sahar,Bartels, Ludwig,Rahman, Talat S.,Dowben, Peter A. American Chemical Society 2018 The Journal of Physical Chemistry Part C Vol.122 No.18
<P>We find that exposure of the MoS<SUB>2</SUB> basal plane to methanol leads to the formation of adsorbed methoxy and coincides with sulfur vacancy generation. The conversion of methanol to methoxy on MoS<SUB>2</SUB> is temperature dependent. Density functional theory simulations and experiment indicate that the methoxy moieties are bound to molybdenum, not sulfur, while some adsorbed methanol is readily desorbed near or slightly above room temperature. Our calculations also suggest that the dissociation of methanol via O-H bond scission occurs at the defect site (sulfur vacancy), followed subsequently by formation of a weakly bound H<SUB>2</SUB>S species that promptly desorbs from the surface with creation of new sulfur vacancy. Photoluminescence and scanning tunneling microscopy show clear evidence of the sulfur vacancy creation on the MoS<SUB>2</SUB> surface, after exposure to methanol.</P> [FIG OMISSION]</BR>
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