A complex study of the adhesion of multi-walled carbon nanotubes to a titanium surface, depending on the modes of irradiation with He⁺ ions of the “MWCNT/Ti” system, was conducted using atomic force microscopy and X-ray photoelectron spectroscopy. A quantitative assessment of the adhesion force at the interface, performed using atomic force microscopy, demonstrated its significant increase as a result of treatment of the “MWCNT/Ti” system with a beam of helium ions. The nature of the chemical bonding between multi-walled carbon nanotubes and the surface of the titanium substrate, which causes this increase in the adhesion of nanotubes to titanium as a result of ion irradiation, was investigated by X-ray photoelectron spectroscopy. It was established that this bonding is the result of the formation of chemical C–O–Ti bonds between titanium and carbon atoms with the participation of oxygen atoms of oxygen-containing functional groups, which are localized on defects in the nanotube walls formed during ion irradiation. It is significant that there are no signs of direct bonding between titanium and carbon atoms.

The morphology, structure, and electrophysical characteristics of multiwall carbon nanotubes (MWCNTs), as affected by defects induced by ion bombardment, are studied using Raman spectroscopy...

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”.

The electric conductivity of individual multiwalled carbon nanotubes (CNTs) doped with nitrogen has been studied in as-synthesized, heat-treated, and argon-ion-irradiated states by the method of electrostatic force microscopy (EFM). Modelling of transverse cross-section profiles of EFM images were used to determine the potential difference across the probe tip–CNT gap (U_tip-CNT), which is a parameter related to the conductivity of CNTs. A strong correlation between the specific volume conductivity of a CNT layer and average U_tip-CNT value has been found for all types of samples. It is established that a change in the conductivity of N-doped CNTs upon thermal annealing and argon-ion irradiation is caused by modification of the composition and/or concentration of defects in CNT walls.

A technique for determination of the dielectric constant of individual hemoglobin molecules is presented. It is based on modeling the profiles of their images obtained using electrostatic...