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The micropipet delivery--substrate collection (MD--SC) mode of scanning electrochemical microscopy (SECM) is demonstrated. This new mode is intended for the study and imaging of electrochemical as well as electrocatalytic reactions of neutral species that cannot be generated electrochemically. The spontaneous transfer of the analyte from an organic solvent across an interface between two immiscible electrolyte solutions (ITIES) and its diffusion into the aqueous solution served as the mechanism to deliver it to the substrate, where the corresponding electrochemical or electrocatalytic reaction is carried out. High-resolution SECM images of ferrocenemethanol (FcMeOH) oxidation, benzoquinone (BQ) reduction, and the formic acid oxidation reaction (FAOR) at a Pt microelectrode substrate were successfully acquired. Furthermore, this new mode was used for the screening of electrocatalyst arrays for the methanol oxidation reaction (MOR), with the optimization of an efficient candidate, [Pt.sub.80][Ce.sub.20]. Digital simulations produced quantitative information about the expected current response at the substrate in the proposed MD--SC mode of SECM. 10.1021/ac901434a

The electrochemical oxidation of formic acid was studied by the tip generation-substrate collection (TG-SC) mode of scanning electrochemical microscopy (SECM), extending the number of applications of SECM in electrocatalysis. Formic acid was generated at a Hg on Au ultramicroelectrode (UME) tip by reduction of C[O.sub.2] in a 0.1 M KHC[O.sub.3] solution saturated with this gas. The electrocatalytic activity of different Pd-Co bimetallic compositions was evaluated using a Pd-Co electrocatalyst array formed by spots deposited onto glassy carbon (GC) as a SECM substrate. The SECM tip, which generated a constant formic acid flux, was scanned above the array and the oxidation current generated when formic acid was collected by active electrocatalyric spots was displayed as a function of tip position. This generated a SECM image that showed the electrocatalytic activity of each spot. SECM screening identified [Pd.sub.50][Co.sub.50] (Pd/Co = 50:50, atomic ratio) as a better electrocatalyst toward the formic acid oxidation than pure Pd or Pt in 0.1 M KHC[O.sub.3] solution and this result was confirmed by cyclic voltammetry. Positive feedback was observed for the most active compositions of Pd-Co which suggests fast reaction kinetics and chemical reversibility during the oxidation of formic acid to C[O.sub.2]. Moreover this feedback increases the contrast between active and non-active spots in this imaging mode.

A strategy for the synthesis of dibenz[ a , j ]anthracenes (DBAs) from cyclohexa-2,5-diene-1-carboxylic acids is presented. Our approach involves sequential C-H olefination, cycloaddition, and decarboxylative aromatization. In the key step for DBA skeleton construction, the bis-C-H olefination products, 1,3-dienes, are utilized as substrates for [4 + 2] cycloaddition with benzyne. This concise synthetic route allows for regioselective ring formation and functional group introduction. The structural features and photophysical properties of the resulting DBA molecules are discussed.

A convenient protocol to fabricate an organic-inorganic hybrid system with covalently bound light-harvesting chromophores (stilbene and terphenylene-divinylene) and an electron acceptor (titanium oxide) is described. Efficient energy- and electron-transfer processes may take place in these systems. Covalent bonding between the acceptor chromophores and the titania/silica matrix would be important for electron transfer, whereas fluorescence resonant energy transfer (FRET) would strongly depend on the ratio of donor to acceptor chromophores. Time-resolved spectroscopy was employed to elucidate the detailed photophysical processes. The coupling of FRET and electron transfer was shown to work coherently to lead to photocurrent enhancement. The photocurrent responses reached a maximum when the hybrid-material thin film contained 60 % acceptor and 40 % donor.