Oxidation stability of confined linear carbon chains, carbon nanotubes, and graphene nanoribbons as 1D nanocarbons

Three typical one-dimensional (1D)/quasi-1D nanocarbons, linear carbon chains, carbon nanotubes, and graphene nanoribbons have been proved to grow inside single-walled carbon nanotubes. This gives rise to three types of hybrid materials whose behaviour and properties compared among each other are far from being understood. After proving the successful synthesis of these nanostructured materials in recently published work, we have now been able to study their oxidation stability systematically by using resonance Raman spectroscopy. Surprisingly, the linear carbon chains, which have been theoretically predicted to be very unstable, are actually thermally stable up to 500 °C, assisted by the protection of the carbon nanotube hosts. Besides, longer linear carbon chains inside narrower CNTs are more stable than the shorter ones inside larger tubes, suggesting that the thermal stability not only depends on the length of linear carbon chains alone, but it is correlated with the confinement of the host tubes in a more complicated manner. In addition, graphene nanoribbons overall appear to be the most stable confined structures. On the other hand, peculiarities like the higher stability of the (6,5) CNT compared to that of its (6,4) counterpart allow this study to provide a solid platform for further studies on the application of these 1D nanocarbons (including true 1D linear carbon chains) under ambient conditions.

Carbamazepine removal from water by carbon dot-modified magnetic carbon nanotubes

Carbon dot- and magnetite-modified magnetic carbon nanotubes (CMNTs) were synthesized and evaluated for carbamazepine removal from water. The adsorbent was characterized by multiple modern surface and microstructure analyzing techniques. CMNTs were composed of three components including carbon dots (CDs), carbon nanotubes (CNTs) and magnetite. CDs and CNTs introduce abundant carboxyl groups onto CMNTs and magnetite allows rapid magnetic separation of the adsorbent realizable after batch adsorption. This adsorbent has a moderately high adsorption capacity of 65 mg-carbamazepine/g-adsorbent at pH 7.0 ± 0.2, which is superior to many reported adsorbents. Carbamazepine was uptaken well in a wide pH range, regardless of the surface charging of CMNTs. Its adsorption on CMNTs was quite fast and reached 80% of removal during the initial 3 h. The mass transfer within CMNTs and the time-dependent utilization, exhaustion and depletion of the adsorption capacity were successfully described using a simplified homogeneous surface diffusion model (HSDM). The surface diffusion coefficients (D_s) rose with increasing initial carbamazepine concentrations. After six regeneration and recycle experiments, the capacity loss of CMNTs was less than 2.2% at the conditions tested. FTIR spectra showed the characteristics of the components. Raman spectra implied a π-π electron donor-acceptor (EDA) interaction during adsorption. This work proposed a method of combining π-bond-rich materials (CNTs and CDs) and magnetite to make separable composite adsorbents with high affinity interactions between carbamazepine and carbon materials. The prepared adsorbent is attractive for carbamazepine removal due to its good performance, moderate cost, ease of separation, and ability to regenerate.

Experimental and DFT studies of carbon nanotubes covalently functionalized with an imidazole derivative for electrochemical stability and green corrosion inhibition as a barrier layer on the nickel alloy surface in a sulphuric acidic medium

Nickel-based alloys are used for various applications such as in automobiles, superalloys and ship making. Their stability in acidic environments, however, is often not sufficient due to their native oxide films not withstanding harsh conditions. Carbon-based materials, in contrast, have shown high stability in acidic environments. In the present work, 4,5-diphenyl-imidazole-functionalized carbon nanotubes were investigated as a corrosion-inhibiting barrier layer on nickel alloy surfaces. We studied the corrosion inhibition efficiency of the imidazole-functionalized carbon nanotubes coated on nickel alloys. The materials were characterized using microscopy and spectroscopy methods. DFT studies were performed as well. The corrosion inhibition was evaluated using electrochemical methods. The imidazole-functionalized CNTs were shown to be crystalline and to have tubular structures. They displayed excellent corrosion inhibition on the nickel alloy surface.

(A) The electrostatic interaction of a functionalized carbon material with a 111 nickel surface, (B) the OPT structure of 4,5-DPM + CNT, and (C) 4,5-DPIM + CNT material chemisorbed on a 111 nickel alloy surface.