Effect of Nitrogen Atoms in the CNT Structure on the Gas Sensing Properties of PANI/CNT Composite

Abstract

Herein we report the gas-sensitive properties to ammonia (at 2–10 ppm) of individual nanostructures of a polyaniline/nitrogen-doped carbon nanotube composite with a nitrogen content of 0 at.% (uCNTs), 2 at.% (N-CNTs) and 4 at.% (N+-CNTs). Doping of nanotubes with nitrogen was carried out in order to both reduce the electron work function, to form a potential barrier at the “PANI-CNTs” interface, and reduce the contribution of nanotubes to the composite conductivity. An increase in the nitrogen content in CNTs leads to an increase in conductivity, a decrease in the work function, and the formation of defects in the outer walls of CNTs. It was found that the structural and chemical state of the polymer layer of all composites is the same. However, polymer morphology on nanotubes changes dramatically with increasing nitrogen content in CNTs: a thin smooth layer on uCNTs, a globular layer on N-CNTs, and a thick layer with a sheet-like structure on N+-CNTs. All composites showed the same response time (~20 s) and recovery time (~120 s). Ammonia sensitivity was 10.5 ± 0.2, 15.3 ± 0.5 and 2.2 ± 0.1 ppm−1 for PANI/uCNTs, PANI/N-CNTs and PANI/N+-CNTs, respectively. Based on the results obtained here, we came to the conclusion that the morphological features of the polymer layer on CNTs with different nitrogen content have a dominant effect on the gas reaction than the change in the electronic properties of the polymer at the interface “PANI-CNT”.

Carboxyl Functionalization of N-MWCNTs with Stone–Wales Defects and Possibility of HIF-1α Wave-Diffusive Delivery

“…Figure 1 f shows the C1s NEXAFS spectrum of the irradiated N-MWCNTs formed by absorption transitions of electrons from the 1s state of carbon to unoccupied 2p π* and σ* states due to X-ray quantum absorption at a photon energy of 280–320 eV. The presence of intense absorption bands π*(C=C) at a photon energy of ~284.9 eV and σ*(C=C) at ~291–293 eV in the C1s NEXAFS spectrum shows that the N-MWCNT contains regions with a hexagonal structure [ 35 , 36 ]. However, the absence of local peaks at ~291.7 and ~292.8 eV, which should be present in perfectly structured MWCNTs, and the smearing of the high-energy spectrum of σ*(C=C) point to a large number of structural defects in the specimen [ 37 , 38 ].…”

“…However, the absence of local peaks at ~291.7 and ~292.8 eV, which should be present in perfectly structured MWCNTs, and the smearing of the high-energy spectrum of σ*(C=C) point to a large number of structural defects in the specimen [ 37 , 38 ]. The peaks of π*(C–OH) at a photon energy of ∼286.4 eV and π*(C=O) at ∼288.5 eV correspond to carbon in hydroxyl, carbonyl, and carboxyl groups [ 35 , 39 ]. The above spectral features suggest that oxygen-containing functional groups are present on the CNT surface.…”

Sugar Molecules Detection via C2N Transistor-Based Sensor: First Principles Modeling

“…Because the surface to volume ratios of carbon nanomaterials, such as carbon nanotubes and graphene are high, a lot of biomolecules can be adsorbed onto the surface [ 47 ]. Nitrogen atom doping of carbon nanomaterials improves their electrical conductivity, increasing their sensitivity for sensing applications [ 48 ]. It is possible to create nitrogen-doped carbon nanomaterials by adding nitrogen to carbon nanomaterials.…”

“…Additionally, compared to pristine carbon, nitrogen-doped carbon nanomaterials have demonstrated enhanced stability and biocompatibility, making them appropriate for application in biosensors [ 50 ]. Overall, nitrogen-doped carbon nanomaterials are a desirable option for use in biosensors due to their large surface area, electrical conductivity, and biocompatibility [ 46 , 48 , 50 ].…”