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Electrochemically active hybrid electrodes have been obtained by non-covalent immobilization of homo-oligoribonucleotide probes on the surface of multi-walled carbon nanotubes (MWCNTs) grown vertically on a silicon substrate. Immobilization has been achieved by interaction of heterocyclic bases of oligonucleotide with MWCNT surface or through a pyrene anchor group pre-conjugated to oligonucleotide. The electrode capacitance signal measured in our model system allowed for the selective recognition of target RNA oligonucleotides. Pyrene-anchoring of oligonucleotide probes to the MWCNT surface was shown to provide the better selectivity and stability of electrochemical response of the hybrid electrode. [ABSTRACT FROM AUTHOR]

Using a set of microscopic, spectroscopic, and electrochemical methods, a detailed study of the interrelation between the structural and electrochemical properties of the as-prepared nitrogen-containing multi-walled carbon nanotubes (N-MWCNTs) and their modified derivatives is carried out. It was found that after treatment of nanotubes with hydrochloric acid, their structure is improved by removing amorphous carbon from the outer layers of N-MWCNTs. On the contrary, ion bombardment leads to the formation of vacancy-type structural defects both on the surface and in the bulk of N-MWCNTs. It is shown that the treated nanotubes have an increased specific capacitance (up to 27 F·g−1) compared to the as-prepared nanotubes (13 F·g−1). This is due to an increase in the redox capacitance. It is associated with the reversible Faraday reactions with the participation of electrochemically active pyridinic and pyrrolic nitrogen inclusions and oxygen-containing functional groups (OCFG). Based on the comparison between cyclic voltammograms of N-MWCNTs treated in HCl and with an ion beam, the peaks on these curves were separated and assigned to specific nitrogen inclusions and OCFGs. It is shown that the rate of redox reactions with the participation of OCFGs is significantly higher than that of reactions with nitrogen inclusions in the pyridinic and pyrrolic forms. Moreover, it was established that treatment of N-MWCNTs in HCl is accompanied by a significant increase in the activity of nitrogen centers, which, in turn, leads to an increase in the rate of redox reactions involving OCFGs. Due to the significant contribution of redox capacitance, the obtained results can be used to develop supercapacitors with increased total specific capacitance. [ABSTRACT FROM AUTHOR]

This work contributes to the understanding of single-walled carbon nanotube synthesis by an aerosol CVD method using ethylene and toluene as a hybrid carbon source. We evaluated an extensive set of synthesis conditions revealing the role of ferrocene, toluene, and ethylene. We found the fundamental role of ethylene promoting nanotube nucleation and catalyst activation degree at all the concentrations studied, and enhancing nanotube growth at low ethylene content. We observed the interplay effect of toluene and ethylene concentrations on the nanotube growth rate, accompanied by the detrimental effect of toluene on catalyst activation degree. Nevertheless, toluene apparently promotes nanotube crystallinity, increasing the film conductivity while used as an individual carbon source. Adjusting the ethylene and toluene concentrations, we produced carbon nanotube-based transparent and conductive films with an equivalent sheet resistance (at 90% transmittance at 550 nm wavelength) value of 57 Ω/□ at the synthesis yield of 0.24 cm2 L−1, which is at least two times higher than the results reported earlier. [Display omitted] • Ethylene boosts SWCNT nucleation and enhances catalyst activation degree. • Ethylene promotes growth rate but deactivates catalyst at high concentrations. • Toluene improves nanotube crystanillity and deteriorates catalyst activation degree. • Toluene and ethylene together yield in better performance unlike separate supply. • High-yield production of high-performance transparent conductive films demonstrated. [ABSTRACT FROM AUTHOR]

Advances in supercapacitor performance are boosted both by material design helping to improve specific capacitance and by tailoring of device architecture, often addressing flexibility to enable rolling-up packaging to reach high nominal values. This keeps attention to flexible lightweight materials, such as single-walled carbon nanotubes (SWCNTs), and conducting polymers, such as polyaniline (PANI). In this work, we design and study unique "dead-weight" free supercapacitors based on PANI electrochemically deposited on free-standing SWCNT films. Depending on the carbon nanotube film characteristics, we adjusted polymer inclusion into the nanotube films and evaluated its structure by TEM, SEM, XPS and Raman spectroscopy. Electrochemical methods were used to investigate the relationship between the morphology of initial SWCNT films, deposited PANI, and the electrochemical properties of the composite materials, including specific gravimetric capacitance and self-discharge processes. We show that thin free-standing films of SWCNTs with deposited PANI are less prone to self-discharge due to higher resistance arising from the lower density of the nanotubes in the film. Yet, such films enable better and more uniform deposition allowing to reach the maximum gravimetric capacitance value of 541 F g−1. This synergistic performance allows the creation of an electrode material for flexible ultra-light and powerful supercapacitors. [Display omitted] • "Dead-weight" free flexible supercapacitor is designed. • The supercapacitor is based on free-standing SWCNT film and PANI composite. • Thin SWCNT films serve as a substrate for PANI in situ deposition. • SWCNTs provide high capacitance retention for PANI/SWCNT composite. • The highest achieved specific gravimetric capacitance is 541 F g−1. [ABSTRACT FROM AUTHOR]