Molecular Structure of the Interphase Formed by Plasma-Polymerized Acetylene Films and Steel Substrates

Abstract

The molecular structure of the interphase between plasma-polymerized acetylene films and steel substrates was determined using in situ reflection-absorption infrared spectroscopy (RAIR) and X-ray photoelectron spectroscopy (XPS). Plasma-polymerized acetylene films were deposited onto polished steel substrates using argon as a carrier gas and inductively coupled, radio frequency (RF)-powered plasma reactors that were interfaced directly to the XPS and Fourier transform infrared (FTIR) spectrometers. RAIR showed that the plasma polymerized films contained large numbers of methyl and methylene groups but only a small number of mono substituted acetylene groups, indicating that there was substantial rearrangement of the monomer molecules during plasma polymerization. Bands were observed near 1020 and 855 cm À1 in the RAIR spectra that were attributed to skeletal stretching vibrations in CÀCÀOÀFe groups, indicating that the plasma-polymerized films interacted with the substrate through formation of alkoxide bonds. Another band was observed near 1565 cm À1 and attributed to carboxylate groups in the interphase between the films and the oxidized surface of the substrate. Results obtained from XPS showed that the surface of the iron substrate consisted mostly of a mixture of Fe 2 O 3 and FeOOH and that iron was mostly present in the Fe(III) oxidation state. However, during plasma polymerization of acetylene, there was a tendency for the concentration of FeOOH groups to decrease and for the concentration of Fe(II) to increase, due to the reducing nature of argon=acetylene plasmas. Results from XPS also confirmed the formation of alkoxide and carboxylate groups in the interphase during plasma polymerization of acetylene.

Directional Charge Transfer Channels in a Monolithically Integrated Electrode for Photoassisted Overall Water Splitting

“…As shown in Figure S7, the FTIR spectrum of CCN@FFC matches the vibration modes of bare CCN, indicating the chemical structure of CCN is well maintained after bonding with the FFC nanosheet on the surface, as demonstrated by the typical characteristic sharp band at 810 cm −1 attributed to the out-of-plane bending vibration of tri-s-triazine rings and the stretching modes in the regions of 1200−1700 cm −1 corresponding to the CN heterocycles, respectively. 52 Distinctly, two bands emerged ranging from 650 to 750 cm −1 and can be ascribed to the M− O and M−OH bending vibrations in CCN@FFC, and the sharp band centered at 1004 cm −1 suggests the formed C−C− O−Fe bonds between carbon dots and the FFC nanosheet, 53,54 consistent with the results of the XPS spectra. Moreover, the band of the C−O bond shifts to a lower wavenumber compared with pristine CCN, implying the strong interaction at the heterointerface between CCN and FFC.…”