Azide-modified graphitic surfaces were prepared by reaction with iodine azide. The surface-attached azides undergo the “click” reaction with alkyne-terminated molecules ethynylferrocene and 1-ethynyl-4-(trifluoromethyl)benzene. Voltammetric and XPS analyses show the surface coverage of both the azide and the subsequent triazole of 2 × 1013 molecules/cm2. The 1,2,3-triazole linker is stable in an aqueous 1 M HCl solution for at least 60 min at 55 °C.

A Cu I complex of 3-ethynyl-phenanthroline covalently immobilized to an azide-modified glassy carbon surface is an active electrocatalyst for the 4-electron reduction of O 2 to H 2 O. The rate of O 2 reduction is 2 nd order in Cu coverage at moderate overpotential, suggesting that two Cu I species are necessary for efficient 4-electron reduction of O 2 . Mechanisms for O 2 reduction are proposed that are consistent with the observations for this covalently immobilized system and previously reported results for a similar physisorbed Cu I system. Discrete copper complexes are potential catalysts for the 4-electron reduction of O 2 to water in ambient temperature fuel cells as evidenced by Cu-containing fungal laccase enzymes that rapidly reduce O 2 directly to water at a trinuclear Cu active site at remarkably positive potentials. [1][2][3][4][5] Several groups have studied molecular Cu complexes immobilized onto electrode surfaces as an entry into the study of 4-electron O 2 reduction. [6][7][8][9][10][11][12][13][14][15][16][17][18][19] In particular, physisorbed Cu I (1,10-phenanthroline), Cu(phen P ), reduces O 2 quantitatively by 4 electrons and 4 protons to water. [8][9][10] Anson, et al., determined that this reaction was 1 st order in Cu coverage, suggestive of a mononuclear Cu site as the active catalyst. 8,10 In the present study, similar Cu I complexes are covalently attached to a modified glassycarbon electrode surface to form a species denoted Cu(phen C ), and the effect of Cu coverage on the kinetics of electrocatalytic O 2 reduction is investigated. At low overpotentials, we observe a 2 nd order dependence of the O 2 -reduction rate on the coverage of Cu(phen C ), from which we infer that two physically proximal Cu(phen C ) bind O 2 to form a binuclear Cu 2 O 2 species required for 4-electron reduction. We suggest that a similar binuclear species also forms in the case of Cu(phen P ) 8,10 but that rate-limiting binding of O 2 to the first Cu(phen P ) NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript followed by rapid surface diffusion of a second Cu(phen P ) has, until now, obscured the binuclear nature of the reaction.The covalent attachment of 3-ethynyl-1,10-phenanthroline to an azide-modified glassy carbon electrode to form Cu(phen C ) relies on the Cu I -catalyzed cycloaddition of azide and ethynyl groups to form a triazole linker, commonly referred to as the click reaction. 20,21 The electrode is azide terminated by treating a roughly-ground, heat-treated glassy carbon surface with a solution of IN 3 in hexanes, a procedure modified from that first described by Devadoss and Chidsey. 22 An XPS survey of the azide-modified surface shows two N 1s peaks at 399 eV and 403 eV in a 2:1 ratio attributable to the azide nitrogens. [22][23][24] Upon exposure to 3-ethynyl-1,10-phenanthroline under the click reaction conditions 25 , the 403-eV peak disappears and the 399-eV peak broadens, consistent with the formation of the 1,2,3-triazole linker. 22,24 XPS peaks at 934 and ...

Size, shape, and compositional control are at the heart of nanochemistry.[1] Herein, we present a novel method that allows control over all three variables in a simple one-step, wet-chemical procedure. One-dimensional (1D) nanomaterials are of great interest for the construction of highperformance thermoelectric (TE) devices. Theoretical calculations indicate that improvement in TE efficiency can be achieved as the diameter of the 1D structures approaches a few nanometers. [2,3] To date, the most successful synthesis of 1D TE materials has been achieved by electrodeposition within alumina templates. A series of Bi 2 Te 3 , [4,5] Bi 2Àx Sb x Te 3 , [6] Bi 2 Te 3Ày Se y , [7] and Bi 1Àx Sb x [8,9] nanowires were prepared by using the template-based method. The advantages of the electrodeposition method include high efficiency, ease of control over composition, highly crystalline products, and room-temperature reaction conditions. However, the diameters of the nanowires synthesized by the template method are well above 10 nm. To get into the sub-10-nm regime, one needs to obtain templates with very narrow channel diameters, which is currently the limiting factor of this technique.However, advances in combining sonochemistry and electrochemistry have provided a new strategy for the synthesis of nanomaterials. [10][11][12][13] The synthesis of quite sophisticated 1D nanomaterials has recently been demonstrated [14] to be possible through careful control of the electrochemistry, sonochemistry, and initial composition of the precursor solutions. As observed, the advantage of the sonoelectrochemical method is that it achieves 1D control without any template, thereby practically overcoming the limitation of generating nanorods with diameters below 10 nm. This diameter is the size regime in which TE properties become enhanced and a controlled synthesis can produce technologically relevant nanomaterials. Herein, we report the first synthesis of monodispersed PbTe nanorods that are sub-10 nm in diameter through a sonoelectrochemical technique.Furthermore, we present the effect of changing the concentration of the coordinating ligand on the resulting composition of the synthesized nanomaterials. Changing the metal/ ligand ratio enabled us to tune the composition of the product from pure Te to pure PbTe nanorods.Lead telluride is the material of choice because of its great potential in high-performance TE devices.[15] Furthermore, it allows the mechanisms that lead to control over the resulting nanorod size and composition to be studied. Basically, the synthesis of PbTe nanorods consists of two steps: First, the electrodeposition of PbTe on the surface of the Ti sonication horn, and second, the dispersion of the PbTe nuclei into solution by pulsed sonication. Control over the electrodeposition process is crucial in obtaining pure and highly crystalline PbTe nanoparticles. Interestingly, we found that the Pb 2+

Platinum microelectrodes modified with a lipid bilayer membrane incorporating cholesterol oxidase are used for detection of cholesterol contained in the plasma membrane of a single cell. Amperometric responses are consistent with enzymatic catalysis being rate limiting and cholesterol diffusing laterally in the plasma membrane to the electrode contact site. Importantly, electrode response appears to correlate with the cholesterol content of the cell plasma membrane. The electrodes should be useful for characterizing cellular cholesterol tracking pathways involved in pathogenesis of disease.

In this report, we present a novel platform to study proton-coupled electron transfer (PCET) by controlling the proton flux using an electrode-supported hybrid bilayer membrane (HBM). Oxygen reduction by an iron porphyrin was used as a model PCET reaction. The proton flux was controlled by incorporating an aliphatic proton carrier, decanoic acid, into the lipid layer of the HBM. Using this system, we observed a different catalytic behavior than obtained by simply changing the pH of the solution in the absence of an HBM.