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Qingshan Xie

Bio: Qingshan Xie is an academic researcher from University of Miami. The author has contributed to research in topics: Materials science & Composite material. The author has an hindex of 5, co-authored 8 publications receiving 1157 citations.

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TL;DR: In this article, the authors measured anodic and cathodic currents for the triaionic states of C[sub 60] at a scan rate between 10 and 100 mV/s and found that the ratios determined (i[sub a] i[sub c]) were all equal to 1 within experimental error, and that the lifetime of the radicals can be estimated to be < 0.5 min.
Abstract: Of special interest has been the cathodic electrochemistry of fullerenes, in part due to the observation of superconductivity for some of the triaionic states of C[sub 60]. While the cathodic electrochemistry has proven to be very rich, culminating last year in the observation of C[sub 60][sup 6], its anodic electrochemistry remains largely unexplored. To establish the chemical reversibility of the first oxidation wave of C[sub 60] and C[sub 70], the corresponding anodic and cathodic currents for this couple were measured as a function of the scan rate between 10 and 100 mV/s. The ratios determined (i[sub a]i[sub c]) were all equal to 1 within experimental error. Therefore, the cation radicals generated electrochemically are relatively long-lived on the voltammetric time scale at room temperature. The lifetime of the radicals can be estimated to be < 0.5 min. Most interestingly, scanning the potential more positive than that of the first reversible oxidation of C[sub 70] resulted in the observation of a second, one-electron oxidation of C[sub 70], C[sub 70][sup +] [yields] C[sub 70][sup 2+], at a potential of + 1.75 V. It is interesting to note that the potential difference between the first and the second anodic waves is 550 mV, closemore » to the values previously reported for the separations between consecutive cathodic waves of C[sub 60] and C[sub 70]. This second wave does not appear to be chemically reversible, as judged by preliminary cyclic voltammetric studies. Attempts to observe the second oxidation wave for C[sub 60] have not been successful. 14 refs., 1 fig.« less

150 citations

Journal ArticleDOI
TL;DR: Using the dynamic NMR methode presented initially by Riddell and Hayer, recently extended by Hinton et al., it is demonstrated that this molecule significantly enhances the rate at which Na + is transported compared to a closely related carrier model.
Abstract: We report herein the synthesis and characterziation of a rationally designed, completely synthetic compound that inserts in phosphatidylcholine (pc) vesicles. Using the dynamic (equilibrium) NMR methode presented initially by Riddell and Hayer, recently extended by Hinton et al., we demonstrate that this molecule significantly enhances the rate at which Na + is transported compared to a closely related carrier model

125 citations

Journal ArticleDOI
TL;DR: A series of 12 synthetic ionophores containing an amide subtituent connected via a methylene bridge to an aza-crown ring were evaluated for their ability to transport Na + across large unilamellar vesicles (LUVs) using dynamic 23 Na NMR spectroscopy as mentioned in this paper.
Abstract: A series of 12 synthetic ionophores containing an amide subtituent connected via a methylene bridge to an aza-crown ring were evaluated for their ability to transport Na + across large unilamellar vesicles (LUVs) using dynamic 23 Na NMR spectroscopy. The structures contain lipophilic groups connected to the amide nitrogen, ranging in size from C 5 H 11 to C 18 H 37 , and are either tertiary or secondary amides. The crown ether ring size was also varied from 12-C-4 to 15-C-5 to 18-C-6. Surprisingly, the Na + transport efficiencies were very high, with one synthetic system exhibiting an overall transport rate constant similar to that for a naturally-occurring ionophore, monensin

23 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the authors review nonlinear optical processes in various materials which can be utilized in passive optical limiting devices, including reverse saturable absorption, two-photon and free-carrier absorption, nonlinear refraction and induced scattering.

1,201 citations

Journal ArticleDOI
01 Mar 2011-Carbon
TL;DR: In this paper, a review of the literature on nanocarbon-TiO2 photocatalysts is presented, highlighting recent progress in the development of carbon dioxide photocatalyst.

1,075 citations

Journal ArticleDOI
26 May 1994-Nature
TL;DR: This work presents a simple strategy for the design of artifi-cial membrane ion channels based on a self-assembled cylindrical β-sheet peptide architecture that displays good channel-mediated ion-transport activ-ity with rates exceeding 107 ions s−1, rivalling the performance of many naturally occurring counterparts.
Abstract: NATURALLY occurring membrane channels and pores are formed from a large family of diverse proteins, peptides and organic secon-dary metabolites whose vital biological functions include control of ion flow, signal transduction, molecular transport and produc-tion of cellular toxins. But despite the availability of a large amount of biochemical information about these molecules1, the design and synthesis of artificial systems that can mimic the bio-logical function of natural compounds remains a formidable task2–12. Here we present a simple strategy for the design of artifi-cial membrane ion channels based on a self-assembled cylindrical β-sheet peptide architecture13. Our systems—essentially stacks of peptide rings—display good channel-mediated ion-transport activ-ity with rates exceeding 107 ions s−1, rivalling the performance of many naturally occurring counterparts. Such molecular assemblies should find use in the design of novel cytotoxic agents, membrane transport vehicles and drug-delivery systems.

854 citations

Journal ArticleDOI
TL;DR: In this article, the basic principles of the organic chemistry of fullerenes, together with a description of the physicochemical properties that have made these carbon cages popular in materials science, and review the most recent achievements in functionalization of the original fullerene aimed at the creation of new molecular materials.
Abstract: Since their first detection and bulk production, the fullerenes have gained a primary role on the scientific scene, reaching their climax when the 1996 Nobel Prize for Chemistry was awarded to Kroto, Curl and Smalley for their seminal discovery. The unique physical and chemical properties of these new forms of carbon led many scientists to predict several technological applications. This created a heavy disappointment when it was clear that fullerene-based materials would not soon be ready for the market. However, the fullerenes have so far delighted several dozens of researchers who found that C 60 and its relatives undergo a variety of chemical reactions. In most cases, the new derivatives retain the main properties of the original fullerene, and it is now not unlikely that some functionalized fullerenes may find useful applications in the field of materials science and technology. In this Article we summarize the basic principles of the organic chemistry of fullerenes, together with a description of the physicochemical properties that have made these carbon cages popular in materials science, and review the most recent achievements in the functionalization of fullerenes aimed at the production of new molecular materials.

768 citations