Self-Organized Electropolymerization of Aniline on Au (111) Electrode in Hydrochloric Acid

Abstract

The chemical identity of supporting electrolyte can affect the rate of oxidative polymerization of aniline and the structure of the produced polyaniline (PAN). While PAN molecules deposited on ordered gold electrodes are linear in sulfuric and perchloric acids, the situation in hydrochloric acid is yet to be characterized by scanning tunneling microscopy (STM). Although aniline molecules were adsorbed in disarray between 0.1 and 0.8 V (vs. reversible hydrogen electrode) in 0.5 M HCl + 30 mM aniline, they drifted toward nuclei formed preferentially at steps on the Au(111) electrode and self-assembled into highly organized PAN molecules upon anodization at E > 0.9 V. Shifting the potential from 0.9 to 0.6 V converted PAN molecules from the pernigraniline to emeraldine state, and an increase of the film's corrugation height. On Pt(111), aniline molecules were also adsorbed in disarray at E < 0.9 V, but anodization yielded winding PAN molecules in 0.5 M HCl + 3 mM aniline.

Atomic Force Microscopy Based Top-Illumination Electrochemical Tip-Enhanced Raman Spectroscopy

“…Figures a,b exhibit the three redox forms and cyclic voltammogram of PANI on a Au film (AFM image is shown in Figure S7). The two pairs of peaks located at −0.35 V (O 1 /R 1 ) and 0.2 V (O 2 /R 2 ) are attributed to the redox reactions of emeraldine (SQ)/leucoemeraldine (B) and pemigraniline (Q)/emeraldine. , Figure c shows the potential-dependent TERS spectra of 2.2 nm PANI on an Au film substrate. As the potential was swept from −0.4 to 0.3 V, a remarkable increase in the overall intensities of the TERS spectra was observed.…”

“…Thiolacetyl-terminated-phenylene ethynylene-substituted anthraquinone (2-AQ) and (4′-(pyridin-4-yl)­biphenyl-4-yl)­methanethiol (4-PBT) were used as the probe molecules. Monolayer adsorption of the 2-AQ (or 4-PBT) was accomplished by immersing the fresh Au(111) single crystal in a 0.025 mM 2-AQ (or 0.4 mM 4-PBT) ethanol solution for 1 h. Then the substrate was rinsed with copious amounts of ethanol to remove the physisorbed molecules and finally was dried under a nitrogen gas flow. , In the EC-TERS experiment, an atomically smooth Au film was prepared following a template-stripping method. , A 2.2 nm PANI layer was deposited on the Au film by potentiostatic electropolymerization in 0.5 M H 2 SO 4 and 30 mM aniline solution …”

“…40,41 A 2.2 nm PANI layer was deposited on the Au film by potentiostatic electropolymerization in 0.5 M H 2 SO 4 and 30 mM aniline solution. 42 Tip Preparation. Au-and Ag-coated AFM TERS tips were fabricated by the electrochemical deposition of Au or Ag onto silicon AFM tips (VIT_P/IR, NT-MDT) according to our reported protocol.…”

Adsorption and Electrochemical Polymerization of Pyrrole on Au(100) Electrodes as Examined by In Situ Scanning Tunneling Microscopy

“…All solutions were then thoroughly degassed with nitrogen. The Au(100) and Au(111) single crystal electrode beads were made by melting a Au wire (Φ 0.8 mm), as reported previously . They were cut and polished with SiC cloth and alumina slurry to expose the oriented faces.…”

“…The Au(100) and Au(111) single crystal electrode beads were made by melting a Au wire (Φ 0.8 mm), as reported previously. 21 They were cut and polished with SiC cloth and alumina slurry to expose the oriented faces. The electrodes were then annealed by a hydrogen flame and quenched into ultrapure water saturated with hydrogen.…”