Self-assembled monolayers of fluorene- and nitrofluorene-terminated thiols on polycrystalline gold electrode: Electrochemical and optical properties

PAK F., Meral K., Altundas R., EKİNCİ D.

JOURNAL OF ELECTROANALYTICAL CHEMISTRY, cilt.654, ss.20-28, 2011 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 654
  • Basım Tarihi: 2011
  • Doi Numarası: 10.1016/j.jelechem.2011.01.041
  • Dergi Adı: JOURNAL OF ELECTROANALYTICAL CHEMISTRY
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.20-28
  • Anahtar Kelimeler: Fluorene-terminated thiols, Self-assembled monolayers, Cyclic voltammetry, Fluorescence spectroscopy, Spectroelectrochemical measurements, ORGANIZED MOLECULAR ASSEMBLIES, OMEGA-HYDROXY THIOL, SURFACE-CONFINED MONOLAYERS, OXIDIZED ALUMINUM SURFACE, N-ALKANETHIOL MONOLAYERS, GLASSY-CARBON ELECTRODES, PHASE PROBE MOLECULES, NORMAL-ALKANOIC ACIDS, STRUCTURAL-CHARACTERIZATION, COATED ELECTRODES
  • Atatürk Üniversitesi Adresli: Evet

Özet

In this paper, two new thiols, [4-(9H-fluoren-9-ylmethyl)-phenyl]-methanethiol (6a) and [4-(2-nitro-9H-fluoren-9-ylmethyl)-phenyl]-methanethiol (6b), were synthesized, and self-assembled monolayers (SAMs) of these thiols were formed on gold electrodes. The structure and surface properties of molecular films were investigated by contact angle measurements and attenuated total reflectance infrared spectroscopy (ATR-FTIR). The blocking behavior of Au-6a and Au-6b SAMs was examined with cyclic voltammetry in the presence of redox probes such as K3Fe(CN)(6), Ru(NH3)(6)Cl-3 and ferrocene. Electrochemical measurements revealed that the voltammetric behavior of the redox probes was dependent on the nature of the probe molecules, the electrolytic solution composition and the monolayer structure. The optical properties of the SAMs were studied by steady-state and time-resolved fluorescence spectroscopy. It was obtained that the fluorescence emission bands of Au-6a and Au-6b monolayers were red-shifted and broadened compared to those of free thiols in solution as well as significant reduction at their emission intensities. The fluorescence decay profiles of 6a and 6b monolayers were described by a monoexponential function. In order to determine the possible deactivation mechanism between the metal support and photoexcited molecules, spectroelectrochemical steady-state fluorescence and lifetime measurements on the Au-fluorophore electrodes were also performed as a function of the applied potential. These results indicate that the fluorescence quenching occurs via an energy transfer mechanism from the excited molecules to the gold substrate. (C) 2011 Elsevier B.V. All rights reserved.