Composition, Electronic and Magnetic Investigation of the Encapsulated ZnFe2O4 Nanoparticles in Multiwall Carbon Nanotubes Containing Ni Residuals

Abstract

We report investigation on properties of multiwall carbon nanotubes (mCNTs) containing Ni residuals before and after encapsulation of zinc ferrite nanoparticles. The pristine tubes exhibit metallic character with a 0.3 eV reduction in the work function along with ferromagnetic behavior which is attributed to the Ni residuals incorporated during the preparation of tubes. Upon encapsulation of zinc ferrite nanoparticles, 0.5 eV shift in Fermi level position and a reduction in both the π band density of state along with a change in the hybridized sp2/sp3 ratio of the tubes from 2.04 to 1.39 are observed. As a result of the encapsulation, enhancement in the σ bands density of state and coating of the zinc ferrite nanoparticles by the internal layers of the CNTs in the direction along the tube axis is observed. Furthermore, Ni impurities inside the tubes are attracted to the encapsulated zinc ferrite nanoparticles, suggesting the possibility of using these particles as purifying agents for CNTs upon being synthesized using magnetic catalyst particles. Charge transfer from Ni/mCNTs to the ZnFe2O4 nanoparticles is evident via reduction of the density of states near the Fermi level and a 0.3 eV shift in the binding energy of C 1 s core level ionization. Furthermore, it is demonstrated that encapsulated zinc ferrite nanoparticles in mCNTs resulted in two interacting sub-systems featured by distinct blocking temperatures and enhanced magnetic properties; i.e., large coercivity of 501 Oe and saturation magnetization of 2.5 emu/g at 4 K.

A Comprehensive Study of Pristine and Calcined f-MWCNTs Functionalized by Nitrogen-Containing Functional Groups

“…As reported during the synthesis of CNTs, some catalyst particles are encapsulated into nanotubes forming a single magnetic domain and, in this way, enhancing the coercivity of nanotubes. Such phenomena were observed in pure and functionalized nanotubes and their composites [ 5 , 26 ]. The value of coercivity estimated based on hysteresis loops is reduced upon calcination from 1.77 kOe (pristine f-MWCNTs) to 0.63 kOe (calcined at 300 °C f-MWCNTs).…”

“…Thus, CNTs can be considered as a hexagonal array of carbon atoms wound in a hollow cylinder in two ways: single-walled nanotubes (SWCNTs) and multi-walled (MWCNTs) nanotubes [ 1 ]. These materials are characterized in particular by (i) outstanding mechanical and structural properties; (ii) good surface to area ratio; (iii) unique electrical conductivity; (iv) chemical and thermal stability, making them attractive components for nanohybrids [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. Nevertheless, CNTs, usually in their pristine form, tend to aggregate by forming agglomerates combined with van der Waals interactions [ 16 ].…”

“…Understanding the impact of the functionalization type on the various properties of CNTs is one of the key factors for their potential future applications. Keeping in mind the development of nanotechnology, the electronic and magnetic properties of CNTs could be exploited, for example, in the design and synthesis of nanocomposite materials [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. In general, MWCNTs are promising candidates for building blocks to build nanocomposites.…”

Filled Carbon Nanotubes as Anode Materials for Lithium-Ion Batteries

“…Mostly, CNT of type PR-24-XT-HHT (Pyrograf Products, Inc., Cedarville OH, USA) have been used as templates. For introducing materials into the inner cavity of the CNT, mainly extensions of solution-based approaches reported in [38][39][40][41][42][43] have been applied [44,45]. This is illustrated by the example of Mn3O4@CNT which has been obtained by filling CNT with a manganese salt solution and a subsequent reducing step yielding homogeneously MnO-filled CNT (MnO@CNT) [4].…”

Encapsulation of Agents inside Crystals as Liquid Inclusions

“…Possible applications range from the encapsulation of pharmaceutically active agents to flavors in food and also to technical applications [1][2][3]. Several techniques are used to generate such encapsulation systems, e.g., extrusion, liposomes, or carbon nanotubes [2][3][4].…”