Abstract
The influence of single-walled carbon nanotubes enriched in semiconductor (S-SWNTs) and metallic (M-SWNTs) tubes on the photoluminescence (PL) of polyaniline (PANI), electrosynthesized in the presence of the H2SO4 and HCl solutions, is reported. The emission bands peaked at 407–418 and 440–520 nm indicate that the electropolymerization of aniline (ANI) leads to the formation of short and longer macromolecular chains (MCs), respectively. We demonstrate that the reaction product consists of ANI tetramers (TT) and trimers (TR) as well as PANI-salt. Using Raman scattering and IR absorption spectroscopy, a covalent functionalization of SWNTs with shorter and longer MCs of PANI-salt is demonstrated. The presence of S-SWNTs and M-SWNTs induces a decrease in ANI TT weight in the reaction product mass consisting in S-SWNTs and M-SWNTs covalently functionalized with PANI-emeraldine salt (ES) and PANI-leucoemeraldine salt (LS), respectively. A PANI PL quenching is reported to be induced of the S-SWNTs and M-SWNTs. A de-excitation mechanism is proposed to explain PANI PL quenching.
Highlights
In the last thirty years, many efforts have been made in order to understand the effect of various electrolytes such H2SO4 and HCl on the polyaniline (PANI) electrosynthesis, the electrochemical properties and the conductivity[1,2,3,4,5]
The cyclic voltammograms (CVs) shown in Fig. 1a2,b2 and c2 illustrate in the case of (i) the blank Au electrode, three oxidation maxima situated at +0.20, +0.47 and +0.70 V, and three reduction peaks at +0.041, +0.41 and +0.56 V (Fig. 1a2); (ii) the Au electrode covered with a M-single-walled carbon nanotubes (SWNTs) film, the oxidation peaks localized at +0.21, +0.49 and +0.73 V, they being accompanied by three reduction peaks at +0.006, +0.36 and +0.606 V (Fig. 1b2), respectively; and for (iii) the Au electrode covered with a S-SWNT film, the oxidation maxima peaked at +0.22, +0.50 and +0.73 V while the three reduction maxima peaked at +0.001, +0.38, +0.58 V (Fig. 1c2)
A schematic illustration of the ANI electropolymerization in the presence of the H2SO4 and HCl solutions onto the Au electrode covered with S-SWNTs and M-SWNTs films as well as the chemical reactions mechanism involved in the preparation of the PANI/SWNTs composite films are shown in Figs S2 and S3 in Supplementary Information
Summary
In the last thirty years, many efforts have been made in order to understand the effect of various electrolytes such H2SO4 and HCl on the polyaniline (PANI) electrosynthesis, the electrochemical properties and the conductivity[1,2,3,4,5]. To the best of the authors’ knowledge, there is no article that is focused on the influence of SWNTs on the PL of PANI electrosynthesized in the presence of HCl or H2SO4 We will investigate this optical property of composites based on PANI and SWNTs enriched in metallic tubes (98%, called M-SWNTs) and semiconducting tubes (99%, called S-SWNTs), respectively, in order to answer the following questions: (i) Does the ANI electropolymerization, in the presence of HCl or H2SO4 solutions, lead to the formation of longer and shorter macromolecular chains (MCs) like those of the PANI and aniline oligomers? We will investigate this optical property of composites based on PANI and SWNTs enriched in metallic tubes (98%, called M-SWNTs) and semiconducting tubes (99%, called S-SWNTs), respectively, in order to answer the following questions: (i) Does the ANI electropolymerization, in the presence of HCl or H2SO4 solutions, lead to the formation of longer and shorter macromolecular chains (MCs) like those of the PANI and aniline oligomers? (ii) Do SWNTs influence the weight of the longer and shorter MCs in the reaction product mass resulted by the ANI electropolymerization? and (iii) Do M-SWNTs or S-SWNTs have an identical role in the PANI PL quenching process?
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