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181.
Derek L. Ho Boualem Hammouda Steven R. Kline 《Journal of Polymer Science.Polymer Physics》2003,41(1):135-138
The dynamic light scattering results presented in this letter demonstrate that the clustering of poly(ethylene oxide) (PEO) can be observed even in ultrapure, freshly double‐distilled and filtered deionized water. It is confirmed that the filtration of solutions removes the clustering structure and that a steady‐state amount of PEO in clusters is reformed in filtered solutions within 24 h. Adding a drop of chloroform to unfiltered aqueous solutions of PEO temporarily alters the clustering structure, but it prevents the clustering of PEO in filtered solutions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 135–138, 2003 相似文献
182.
183.
Wang Y Hernandez RM Bartlett DJ Bingham JM Kline TR Sen A Mallouk TE 《Langmuir : the ACS journal of surfaces and colloids》2006,22(25):10451-10456
Bimetallic nanorods are propelled in aqueous solutions by the catalytic decomposition of hydrogen peroxide to oxygen and water. Several mechanisms (interfacial tension gradients, bubble recoil, viscous Brownian ratchet, self-electrophoresis) have been proposed for the transduction of chemical to mechanical energy in this system. From Tafel plots of anodic and cathodic hydrogen peroxide reactions at various metal (Au, Pt, Rh, Ni, Ru, and Pd) ultramicroelectrodes, we determine the potential at which the anodic and cathodic reaction rates are equal for each metal. These measurements allow one to predict the direction of motion of all possible bimetallic combinations according to the bipolar electrochemical (or self-electrophoretic) mechanism. These predictions are consistent with the observed direction of motion in all cases studied, providing strong support for the mechanism. We also find that segmented nanorods with one Au end and one poly(pyrrole) end containing catalase, an enzyme that decomposes hydrogen peroxide nonelectrochemically, perform the overall catalytic reaction at a rate similar to that of nanorods containing Au and Pt segments. However, in this case there is no observed axial movement, again supporting the bipolar electrochemical propulsion mechanism for bimetallic nanorods. 相似文献
184.
Irena Tatosian Amanda Bubas Anna Iacovino Susan Kline Luke Metzler Michael Van Stipdonk 《Journal of mass spectrometry : JMS》2019,54(9):780-789
The goals of the present study were (a) to create positively charged organo‐uranyl complexes with general formula [UO2(R)]+ (eg, R═CH3 and CH2CH3) by decarboxylation of [UO2(O2C─R)]+ precursors and (b) to identify the pathways by which the complexes, if formed, dissociate by collisional activation or otherwise react when exposed to gas‐phase H2O. Collision‐induced dissociation (CID) of both [UO2(O2C─CH3)]+ and [UO2(O2C─CH2CH3)]+ causes H+ transfer and elimination of a ketene to leave [UO2(OH)]+. However, CID of the alkoxides [UO2(OCH2CH3)]+ and [UO2(OCH2CH2CH3)]+ produced [UO2(CH3)]+ and [UO2(CH2CH3)]+, respectively. Isolation of [UO2(CH3)]+ and [UO2(CH2CH3)]+ for reaction with H2O caused formation of [UO2(H2O)]+ by elimination of ·CH3 and ·CH2CH3: Hydrolysis was not observed. CID of the acrylate and benzoate versions of the complexes, [UO2(O2C─CH═CH2)]+ and [UO2(O2C─C6H5)]+, caused decarboxylation to leave [UO2(CH═CH2)]+ and [UO2(C6H5)]+, respectively. These organometallic species do react with H2O to produce [UO2(OH)]+, and loss of the respective radicals to leave [UO2(H2O)]+ was not detected. Density functional theory calculations suggest that formation of [UO2(OH)]+, rather than the hydrated UVO2+, cation is energetically favored regardless of the precursor ion. However, for the [UO2(CH3)]+ and [UO2(CH2CH3)]+ precursors, the transition state energy for proton transfer to generate [UO2(OH)]+ and the associated neutral alkanes is higher than the path involving direct elimination of the organic neutral to form [UO2(H2O)]+. The situation is reversed for the [UO2(CH═CH2)]+ and [UO2(C6H5)]+ precursors: The transition state for proton transfer is lower than the energy required for creation of [UO2(H2O)]+ by elimination of CH═CH2 or C6H5 radical. 相似文献