Redox and Double-Layer Charging of Phenothiazine Functionalized Monolayer-Protected Clusters

Abstract

Monolayer-protected Au clusters (MPCs) have been prepared with mixed monolayers of alkanethiolates and alkanethiolates terminally omega-functionalized with phenothiazine. The mixed monolayer MPCs can contain as many as 10 phenothiazines/MPC; these electron donors are electroactive in rapid, successive one-electron reactions. Surface adsorption of the functionalized MPCs is evident in cyclic voltammetry. Double-potential-step chronocoulometry with incremented potential steps was applied to unfunctionalized hexanethiolate-coated MPCs and to those functionalized with phenothiazine to analyze the coupling between the diffusion-controlled double-layer charging of the MPC cores and the oxidation of the phenothiazine centers. Apparent changes in ordering of the MPC alkanethiolate chains were observed with infrared spectroscopy in solutions of MPCs where alcohol, carboxylic acid, or phenothiazine moieties had been incorporated into the monolayer.

Peer Reviewed: Optical Sensing with Quantum Dots

“…Additional papers describe "fluorescent" nanoparticles that are, in fact, polymer nanoparticles that contain organic fluorescent dyes (63). Fundamental electrochemical studies of monolayer-protected gold nanoparticles are in the analytical literature, and there are reports of visible photoluminescence from such species (64,65). Colorimetric detection of analytes using analyte-mediated aggregation of gold nanoparticles to produce a red-to-blue color change has been reported (66).…”

Synthesis and structure of new 3,7,10-substituted-phenothiazine derivatives

“…New phenothiazine derivatives, substituted at position 10 with alkyl chains bearing thioacetate (8)(9)(10) or mercapto (11-13) groups, were obtained starting from phenothiazine 1 (Scheme 1, Table 1) In the first step the starting compound was alkylated to 10-bromoalkyl phenothiazine compounds using dibromoalkanes [Br-(CH 2 ) n+1 -Br; n = 2, 5, 7]. After several experiments carried out to obtain the compound 2 we concluded that the best results are obtained using Cu / K 2 CO 3 in an alkylation procedure adapted from the literature [13].…”

“…To a suspension of lithium aluminium hydride (1.34 mmol, 0.05 g) in dry diethyl ether (10 mL) cooled in an ice bath was added dropwise a solution of 3,7-dibromo-10-alkylthioacetate-phenothiazine (8)(9)(10) [0.67 mmol, 0.31 (8), 0.34 (9), 0.36 g (10)] in dry diethyl ether (20 mL). The mixture was stirred for two hours, then sodium hydroxide solution 20% (2 mL) was added and the reaction mixture was stirred for another half an hour then filtered.…”

“…mercapto or thioacetate derivatives) by deposition as self assembled monolayers (SAMs) on gold (1.1.1) surface. Some recent publications revealed special properties for the aggregates obtained by the deposition of phenothiazine units on GNP (gold nanoparticules) via mercapto derivatives [8], or for aggregates that exhibit phenothiazine units at their surface and are built up by ester or ether group formation reactions [9][10]. The phenothiazine units are connected to different materials or substrates using as linkers alkyl or (poly) ethyleneoxid chains attached to the N atom at position 10 ( Fig.…”

Electrochemistry with Nanoparticles

“…The MPCs are soluble nanoelectrodes that exhibit various unusual electrochemical properties when compared to functionalized planar electrodes. Murray and co-workers have contributed enormously to the understanding of the electrochemistry of ofunctionalized and unfunctionalized alkanethiolate stabilized Au-cluster compounds [52][53][54][55][56][57][58][59]. Functional groups such as anthraquinone (AQ), ferrocene (Fc), phenothiazine, arenes, esters, acids, alcohols and dithiols of different chain lengths have been incorporated into alkanethiolate modified Au-clusters using the place exchange method [52].…”