Elucidating the deprotonation of polyaniline films by X-ray photoelectron spectroscopy

Abstract

Spin-coated polyaniline (PANI) thin films can be made conductive following treatment with a dopant (reducing or oxidising agent). However, de-doping results in loss of electrical properties. We chemically doped PANI films using p-toluene sulfonic acid (pTSA) and camphor sulfonic acid (CSA) and examined their ability to retain these dopants and their conductive properties in physiological media. Changes in the protonation level of these films were assessed by N 1s core line spectra in X-ray photoelectron spectroscopy (XPS). PANI films were found to de-dope with a decrease in the ratio of N 1s photoelectron signal corresponding to positively charged nitrogen (i.e. –NH2+, [double bond, length as m-dash]NH+) to the total N 1s signal. De-doping of PANI films was confirmed by depletion of the dopant fragment (–SO3−) as determined from both XPS and atomic distribution in Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) images. XPS has been successfully used as a tool to elucidate the deprotonation of PANI films and the loss of the dopant from the bulk

In situ formation of molecular-scale ordered polyaniline films by zinc coordination

“…4a). 39 A low percentage of protonated amine was also detected in the XPS spectrum, which is not unexpected. 40 After coordination crosslinking of PANI with Zn 2+ , however, PANI-Zn showed different two components that are indicative of a coordinated amine (~400.1 eV) and imine (~401.3 eV), respectively (Fig.…”

A conducting polymer with enhanced electronic stability applied in cardiac models

“…The residing state of nitrogen in the PANI backbone is of particular interest because its chemical environment reveals the oxidation and protonation states of PANI (fig. S1) and can be related to the doping level induced by the addition of acids ( 17 , 35 ). To this effect, the relative amounts of protonated imine and amine were estimated from curve-fitting the N 1 s spectra (Fig.…”

“…Similarly, polythiophene-based biomaterials are converted to the reduced form following incubation in cell culture medium ( 14 ) or through exposure to air ( 15 ). A further challenge for PANI is the deprotonation of amine groups caused by the neutral pH of bodily fluid ( 16 , 17 ). In a study by Gill et al ( 18 ), a reduction in conductance was directly related to the level of deprotonation of the PANI amine groups that occurs in response to neutral or higher pH solutions.…”

Facile fabrication of superparamagnetic graphene/polyaniline/Fe3O4 nanocomposites for fast magnetic separation and efficient removal of dye

“…The N1s core-level spectrum could be deconvoluted into three Gaussian peaks (Fig. 3d), and the peak of major benzenoid-amine component (–NH–) was observed at 399.5 eV along with a small quinoid-imine ( = NH–) peak at 398.9 eV 42 . The shoulder peak at a high binding energy of 400.5 eV was ascribed to positively charged nitrogen (–NH + –), suggesting the formation of the protonated nitrogen species 42 .

Figure 3XPS spectra of GS/PANI/Fe 3 O 4 -4 nanocomposite: ( a ) full spectrum, ( b ) Fe2p, ( c ) C1s, and ( d ) N1s.

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