Short-time preparation and electrochemical properties of a single layer of tetraoctylammonium bromide capped Au nanoparticles on dithiol self-assembled monolayer-modified Au electrode

摘要

Short time immobilization of densely packed tetraoctylammonium bromide (TOAB) stabilized gold nano-particles (AuNPs) were established on a Au electrode modified with a self-assembled monolayer (SAM) of 1,6-hexanedithiol (HDT) or 1,4-benzenedimethanethiol (BDMT). The quartz crystal microbalance exper_iment showed densely packed TOAB-AuNPs single layer formation on both SAMs was achieved within 20 min. AFM images demonstrated that the immobilized TOAB-AuNPs on the SAMs were densely packed and the AuNPs film thickness was 6-7 nm. The electronic communication between the immobilized AuN_Ps and the underlying bulk electrode was confirmed by cyclic voltammetry and electrorefiectance spec_troscopy. A reversible electron transfer reaction was observed for both [Fe(CN)_6]~4-/3- and [Ru(NH_3)_6]~2+/3+ at TOAB-AuNPs immobilized on HDT (Au/HDT/AuNPs) and BDMT (Au/BDMT/AuNPs) modified elec_trodes. The electrorefiectance spectra show a red-shifted strong positive-going plasmon resonance bands at 551 nm and 584 nm, respectively, for the Au/BDMT/AuNPs and Au/HDT/AuNPs electrodes. The observed reversible redox response for the solution redox species and red-shifted plasmon resonance bands for the immobilized AuNPs again indicated that the AuNPs were immobilized on the SAMs in a densely packed manner. An advantage of TOAB-AuNPs modified electrode prepared by short time immersion over citrate-stabilized AuNPs modified electrode was demonstrated by the enhanced oxida_tion of ascorbic acid (AA) at these electrodes. The oxidation of AA was shifted to 90 mV less positive potential with higher oxidation current at TOAB-AuNPs modified electrode when compared to citrate-stabilized AuNPs modified electrode.