Abstract
A new series of sidewall modified single-walled carbon nanotubes (SWCNTs) with perfluorophenyl molecules bearing carboxylic acid or methyl ester moieties are herein reported. Pristine and functionalized SWCNTs (p-SWCNTs and f-SWCNTs, respectively) were characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and scanning electron microscopy (SEM). The nitrene-based functionalization provided intact SWCNTs with methyl 4-azido-2,3,5,6-tetrafluorobenzoate (SWCNT-N-C6F4CO2CH3) and 4-azido-2,3,5,6-tetrafluorobenzoic acid (SWCNT-N-C6F4CO2H) attached every 213 and 109 carbon atoms, respectively. Notably, SWCNT-N-C6F4CO2H was sensitive in terms of the percentage of conductance variation from 5 to 40 ppm of ammonia (NH3) and trimethylamine (TMA) with a two-fold higher variation of conductance compared to p-SWCNTs at 40 ppm. The sensors are highly sensitive to NH3 and TMA as they showed very low responses (0.1%) toward 200 ppm of volatile organic compounds (VOCs) containing various functional groups representative of different classes of analytes such as benzene, tetrahydrofurane (THF), hexane, ethyl acetate (AcOEt), ethanol, acetonitrile (CH3CN), acetone and chloroform (CHCl3). Our system is a promising candidate for the realization of single-use chemiresistive sensors for the detection of threshold crossing by low concentrations of gaseous NH3 and TMA at room temperature.
Highlights
There has been an explosion of interest in carbon nanomaterials over the last 30 years
single-walled carbon nanotubes (SWCNTs)-N-C6F4CO2H was sensitive in terms of the percentage of conductance variation from 5 to 40 ppm of ammonia (NH3) and trimethylamine (TMA) with a two-fold higher variation of conductance compared to p-SWCNTs at 40 ppm
The degree of functionalization of the modi ed SWCNTs was evaluated by X-ray photoelectron spectroscopy (XPS) analysis
Summary
There has been an explosion of interest in carbon nanomaterials over the last 30 years. In Raman spectroscopy, the G-band (at about 1590 cmÀ1) is associated with the ordered sp[2] hybridized carbon structure typical of graphite, whereas the D-band (at about 1330 cmÀ1) is due to the amorphous carbon and local defects that originate from structural imperfections.[27] The general trend shows that a er CNTs covalent functionalization, the G/D ratio decreases and the width of the D-band increases.[28] Fig. 3 shows the Raman spectra for p-SWCNTs and f-SWCNTs and in Table 3 the modes and intensity peaks of D and G bands are reported.
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